Method of processing semiconductor substrate

Abstract

To provide a processing method of a semiconductor substrate for selectively removing a high melting point metal such as ruthenium contained in the semiconductor substrate with respect to copper.SOLUTION: The method for processing a semiconductor substrate includes an oxidation treatment step for forming copper oxide on the surface of copper and a step for removing the high melting point metal. The high-melting-point metal is a metal having a melting point of 1400°C. or more, and examples thereof include one or more kinds selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for processing a semiconductor substrate. [Background technology]

[0002] In semiconductor devices, wiring layers are formed to transmit electrical signals generated by transistors to the outside. Semiconductor devices are becoming increasingly miniaturized, and using materials with low electromigration resistance or high resistance can lead to reduced reliability and impaired high-speed operation. Therefore, wiring materials with high electromigration resistance and low resistance are desired.

[0003] Materials with high electromigration resistance and low resistance, such as aluminum and copper, have been used to date. Metal wiring is formed on patterns exposed on an insulating film. However, as the wiring width becomes narrower, the metal fillability deteriorates, leading to problems such as the formation of voids and short circuits. Therefore, to improve metal fillability, a method is used in which a thin metal film called a liner layer is formed on the dielectric, and then the wiring metal is formed on top of that. High-melting-point metals such as cobalt and ruthenium are being considered for use as liner layers for copper wiring.

[0004] Forming a wiring layer on a semiconductor device involves a process of processing the wiring material, which can be done using dry or wet etching. When wet etching the metal of the liner layer, etching the wiring metal at the same time can lead to increased resistance due to surface roughness and the risk of short circuits, so it is necessary to selectively etch only the metal of the liner layer.

[0005] As a treatment liquid capable of etching a specific metal, Patent Document 1 discloses an etching liquid for etching ruthenium, which contains orthoperiodic acid and ammonia and has a pH of 8 or more and 10 or less.

[0006] Furthermore, Patent Document 2 discloses a treatment liquid for cleaning semiconductor wafers, which contains hypochlorite ions and a solvent and has a pH of more than 7 and less than 12.0 at 25°C. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-090040 [Patent Document 2] International Publication No. 2019 / 142788 Summary of the Invention [Problem to be solved by the invention]

[0008] However, according to the inventors' investigations, it was found that when copper is used as the wiring metal with the etching solution of Patent Document 1, the copper is etched at the same time as the metal of the liner layer, and therefore it is not possible to selectively etch only the metal of the liner layer.

[0009] Furthermore, it has been found that the etching solution of Patent Document 2 can etch high-melting point metals such as ruthenium, but slightly dissolves copper. Furthermore, as copper dissolves, precipitates may form on the copper surface. The reason why the etching solution described in Patent Document 1 cannot selectively etch only high-melting-point metals is The reason for this is not clear, but it is assumed that when the etching solution comes into contact with copper, galvanic corrosion occurs because the corrosion potential of copper is higher than that of high-melting-point metals.

[0010] Therefore, the present invention provides a method for treating a semiconductor substrate that can selectively remove a refractory metal from a semiconductor substrate that contains a refractory metal and copper. [Means for solving the problem]

[0011] As a result of extensive research to solve the above problems, the inventors have found that a high-melting-point metal can be selectively removed by a semiconductor substrate processing method including an oxidation treatment step of forming copper oxide on the copper surface and a step of removing the high-melting-point metal after the oxidation treatment step.

[0012] That is, the gist of the present invention is specifically as follows. [1]: A method for treating a semiconductor substrate containing a refractory metal and copper, comprising: an oxidation treatment step of forming copper oxide on the surface of the copper; and removing the high-melting-point metal after the oxidation treatment step. [2]: The method according to [1], wherein the oxidation treatment step is a step of contacting the semiconductor substrate with a solution containing an oxidizing agent. [3]: The method according to [1] or [2], wherein the oxidizing agent is at least one selected from the group consisting of a hexacyanide metal complex and a halogen oxygen acid ion. [4]: The method according to any one of [1] to [3], wherein the step of removing the high-melting point metal is a step of contacting the semiconductor substrate with a treatment liquid containing hypohalite ions. [5]: The method according to any one of [1] to [4], wherein the high-melting point metal is one or more metals selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium. [6]: A method for manufacturing a semiconductor substrate, comprising the method according to any one of [1] to [5]. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a semiconductor substrate processing method capable of selectively removing a high-melting point metal from a semiconductor substrate containing the high-melting point metal and copper. [Brief explanation of the drawings]

[0014] [Figure 1] 1A to 1C are schematic diagrams illustrating a process for forming wiring on a semiconductor substrate. [Figure 2]FIG. 1 is a schematic diagram of an apparatus used to prepare an aqueous sodium hypobromite solution used in the Examples. [Figure 3] FIG. 1 is a schematic diagram of an apparatus used to prepare an aqueous solution of tetramethylammonium hypochlorite used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] Although the embodiments of the present invention will be described in detail below, the present invention is not limited to these details as long as they do not deviate from the gist of the present invention. Furthermore, the present invention can be implemented by making any modifications within the scope of the present invention. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be combined arbitrarily. Furthermore, the expression "A or B" in this specification may be read as "at least one selected from the group consisting of A and B." Furthermore, the expression "amount of B relative to amount of A" in this specification means "amount of B / amount of A." Furthermore, although a number of embodiments are described in this specification, various conditions in each embodiment may be applied to each other to the extent that they are applicable.

[0016] (Method for processing semiconductor substrates) A method for processing a semiconductor substrate according to one embodiment of the present invention is a method for processing a semiconductor substrate containing a high-melting-point metal and copper, and includes an oxidation treatment step of forming copper oxide on the surface of the copper, and a step of removing the high-melting-point metal after the oxidation treatment step.

[0017] (semiconductor substrate) By treating a semiconductor substrate using the above method, it becomes possible to selectively remove (etch) a high-melting-point metal contained in the semiconductor substrate relative to copper. The high melting point metal contained in the semiconductor substrate is present in the form of a film formed on the semiconductor substrate as, for example, a liner layer. Copper may also be present on the semiconductor substrate or liner layer, for example as wiring. The semiconductor substrate is not limited as long as it contains a high-melting-point metal and copper, and the processing method according to one embodiment of the present invention can be applied to any known substrate used for semiconductors, including, for example, various substrates such as semiconductor wafers, glass substrates, and organic resin substrates.

[0018] (High melting point metals) In this specification, a high-melting point metal is a metal having a melting point of 1400°C or higher. Specific examples include one or more metals selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium. The high-melting point metal preferably includes ruthenium, molybdenum, or tungsten, and most preferably includes ruthenium. The metals may include alloys, and may also include metal compounds such as oxides, nitrides, and oxynitrides of the metals.

[0019] (Oxidation treatment process) The oxidation treatment process aims to form a copper oxide film on the copper surface. The copper oxide film formed by the oxidation treatment process is resistant to many oxidizing agents and is a dense film. Therefore, dissolution of copper by the treatment solution used in the subsequent process of removing the high-melting-point metal is suppressed, making it possible to selectively remove only the high-melting-point metal. The method of the oxidation treatment step is not particularly limited, but it preferably includes a step of contacting an oxidizing gas such as oxygen or carbon dioxide with the semiconductor substrate, or a step of contacting a solution containing an oxidizing agent (hereinafter referred to as an oxidation treatment liquid) with the semiconductor substrate.

[0020] The oxidizing agent contained in the oxidation treatment solution is not particularly limited as long as it can form an oxide film on the copper surface without dissolving the copper and does not affect the high-melting-point metal. Specific examples of the oxidizing agent include at least one selected from the group consisting of hexacyanide metal complexes, halogen oxygen acid ions, and peroxodisulfates. The oxidizing agent is preferably at least one selected from the group consisting of hexacyanide metal complexes and halogen oxygen acid ions.

[0021] The hexacyanide metal complex is, for example, an iron(III) hexacyanide complex, and specific examples thereof include sodium iron(III) hexacyanide, potassium iron(III) hexacyanide, and quaternary ammonium iron(III) hexacyanide. Specific examples of the quaternary ammonium include one or more selected from the group consisting of tetramethylammonium, ethyltrimethylammonium, tetraethylammonium, propyltrimethylammonium, tetrapropylammonium, butyltrimethylammonium, and tetrabutylammonium.

[0022] When the oxidation treatment solution contains a hexacyanide metal complex, the concentration of the hexacyanide metal complex is not particularly limited as long as it does not deviate from the object of the present invention, but is preferably 0.0001 mol / L or more. A concentration of 0.1 mol / L or less is preferred. When the concentration of the hexacyanide metal complex is 0.1 mol / L or less, an oxide film is unlikely to form on the surface of the high-melting point metal, and therefore etching of the high-melting point metal in the subsequent high-melting point metal removal step is unlikely to be hindered. When the concentration of the hexacyanide metal complex is 0.0001 mol / L or more, the rate at which copper oxide is formed on the copper surface is sufficient. From the viewpoints of the effect on the high-melting point metal and the rate at which an oxide film is formed on the copper surface, the concentration of the hexacyanide metal complex is preferably 0.001 mol / L or more and 0.1 mol / L or less, and more preferably 0.005 mol / L or more and 0.1 mol / L or less, relative to the total volume of the oxidation treatment solution.

[0023] Examples of halogen oxygen acid ions include one or more selected from the group consisting of chlorate ions, bromate ions, iodate ions, chlorite ions, and bromite ions. Specific examples of sources of halogen oxygen acid ions include one or more selected from the group consisting of sodium chlorate, sodium bromate, sodium iodate, sodium chlorite, sodium bromite, quaternary ammonium chlorate, quaternary ammonium bromate, quaternary ammonium iodate, quaternary ammonium chlorite, and quaternary ammonium bromite. Specific examples of quaternary ammonium include one or more selected from the group consisting of tetramethylammonium, ethyltrimethylammonium, tetraethylammonium, propyltrimethylammonium, tetrapropylammonium, butyltrimethylammonium, and tetrabutylammonium.

[0024] When the oxidation treatment solution contains a halogen oxyacid, the concentration of the halogen oxyacid ions is not particularly limited as long as it does not deviate from the purpose of the present invention, but is preferably 0.0001 mol / L or more and 5.0 mol / L or less. A halogen oxyacid ion concentration of 5.0 mol / L or less can prevent the deposition of halogen oxyacid salts on the copper surface. A halogen oxyacid ion concentration of 0.0001 mol / L or more ensures a sufficient rate of copper oxide formation on the copper surface. From the viewpoints of preventing the deposition of halogen oxyacid salts on the copper surface and the rate of oxide film formation on the copper surface, the halogen oxyacid ions are preferably 0.001 mol / L or more and 0.5 mol / L or less, and more preferably 0.005 mol / L or more and 0.1 mol / L or less, relative to the total volume of the oxidation treatment solution.

[0025] Examples of peroxodisulfates include one or more selected from the group consisting of sodium peroxodisulfate, ammonium peroxodisulfate, and quaternary ammonium peroxodisulfate. Specific examples of quaternary ammonium include one or more selected from the group consisting of tetramethylammonium, ethyltrimethylammonium, tetraethylammonium, propyltrimethylammonium, tetrapropylammonium, butyltrimethylammonium, and tetrabutylammonium. When the oxidation treatment solution contains peroxodisulfate, the concentration thereof is preferably 0.001 mol / L or more and 0.5 mol / L or less, and more preferably 0.005 mol / L or more and 0.1 mol / L or less, relative to the total volume of the oxidation treatment solution, from the viewpoints of preventing the precipitation of peroxodisulfate on the copper surface and of the rate at which an oxide film is formed on the copper surface.

[0026] (solvent) Examples of the solvent for the oxidation treatment solution include water and organic solvents, with water being most preferred. The water contained in the oxidation treatment solution is preferably water from which metal ions, organic impurities, particles, etc. have been removed by distillation, ion exchange treatment, filtration, various adsorption treatments, etc., and pure water or ultrapure water is particularly preferred.

[0027] The organic solvent is preferably a water-soluble organic solvent that can be mixed with water in any ratio, and examples of the water-soluble organic solvent include one or more selected from the group consisting of ether solvents, alcohol solvents, ketone solvents, amide solvents, nitrile solvents, sulfur-containing solvents, and lactone solvents.

[0028] Examples of the ether solvent include one or more selected from the group consisting of diethyl ether, isopropyl ether, tert-butyl methyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol butyl methyl ether, diethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, ethylene glycol dibutyl ether, and 1,2-diethoxyethane.

[0029] Examples of alcohol solvents include one or more selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methoxyethanol, ethylene glycol monobutyl ether, and 2-ethoxyethanol.

[0030] Examples of the ketone solvent include one or more selected from the group consisting of acetone, 2-butanone, 3-pentanone, cyclohexanone, and cyclopentanone.

[0031] Examples of the amide solvent include one or more selected from the group consisting of formamide, monomethylformamide, dimethylformamide, acetamide, monomethylacetamide, dimethylacetamide, monoethylacetamide, and diethylacetamide.

[0032] The nitrile solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, glutaronitrile, and 3,3'-oxydipropionitrile. Examples of sulfur-containing solvents include dimethyl sulfone and sulfolane. Examples of lactone solvents include γ-butyrolactone and ε-caprolactone.

[0033] The amount of the solvent is not particularly limited, and can be adjusted appropriately so that the concentration of the oxidizing agent in the oxidation treatment liquid becomes the desired concentration.

[0034] (Process for removing high melting point metals) According to one embodiment of the present invention, the step of removing the high-melting-point metal (hereinafter referred to as the removing step) is a step that follows the oxidation treatment step. The order of the removing step is not particularly limited as long as it is performed after the oxidation treatment step. For example, the removing step may be performed immediately after the oxidation treatment step, or a step of washing off the oxidizing agent used in the oxidation treatment step or other steps may be optionally performed between the oxidation treatment step and the removing step.

[0035] The removal step is not particularly limited as long as it is a method capable of removing the high-melting point metal, and may include physical treatment or chemical treatment, but preferably includes a step of contacting the semiconductor substrate with a treatment liquid containing hypohalite ions. Preferably, the removing step is a step of selectively removing the high-melting-point metal with respect to copper. Here, selectively removing with respect to copper means that the etching rate ratio (etching rate of the high-melting-point metal / etching rate of copper) described later in the examples is 50 or more.

[0036] (hypohalite ion) The treatment liquid used in the removal step (hereinafter referred to as the removal treatment liquid) is preferably capable of selectively removing only the high-melting-point metal without removing the oxide film formed in the oxidation treatment step. Specific examples of such removal treatment liquids include treatment liquids containing hypohalite ions. The removal treatment liquid preferably contains one or more hypohalite ions selected from the group consisting of hypobromite ions and hypochlorite ions. The concentration of the hypohalite ions is determined in accordance with the present invention. There are no particular limitations as long as the objective of the present invention is not exceeded, but the concentration is preferably 0.0001 mol / L or more and 1.0 mol / L or less.

[0037] When the concentration of hypohalite ions is 1.0 mol / L or less, decomposition of the hypohalite ions is suppressed, and the function as an oxidizing agent is fully exhibited. When the concentration of hypohalite ions is 0.0001 mol / L or more, the etching rate of the high-melting-point metal is sufficient. From the viewpoints of the stability of the removal treatment solution and the dissolution rate of the high-melting-point metal, the concentration of hypohalite ions contained in the removal treatment solution of this embodiment is preferably 0.001 mol / L or more and 0.5 mol / L or less, and more preferably 0.005 mol / L or more and 0.1 mol / L or less, relative to the total volume of the removal treatment solution.

[0038] The removal treatment solution may contain only one type of hypohalite ion, or may contain two or more types of hypohalite ions. The above concentration range of the hypohalite ion indicates the concentration range of one type when hypochlorite ion or hypobromite ion is contained alone, and indicates the total concentration range when two or more types are contained.

[0039] Methods for incorporating one or more hypohalite ions selected from the group consisting of hypobromite ions and hypochlorite ions into the removal treatment solution include a method of adding a hypohalite salt, a method of adding chlorine or bromine to an alkaline solution, and, in the case of hypobromite ions, a method of generating hypobromite ions by adding a bromine-containing compound and an oxidizing agent. The hypohalite may be at least one selected from the group consisting of sodium hypochlorite, potassium hypochlorite, sodium hypobromite, and potassium hypobromite. The alkaline solution may be, for example, one or more selected from the group consisting of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and an aqueous tetramethylammonium solution.

[0040] (alkali metals or alkaline earth metals) The removal treatment solution may contain an alkali metal or alkaline earth metal to the extent that the object of the present invention is not impaired. Specific examples of alkali metals include one or more selected from the group consisting of Na, K, and Rb. Specific examples of alkaline earth metals include one or more selected from the group consisting of Mg, Ca, and Sr. The alkali metal or alkaline earth metal functions as an oxidation promoter for the high-melting-point metal. These metals are presumed to exist in the treatment solution in the form of metal ions. The concentration of the alkali metal or alkaline earth metal is not particularly limited as long as it does not deviate from the object of the present invention, but is preferably 0.0001% by mass or more and 10.0% by mass or less relative to the total mass of the removal treatment solution. A concentration of the alkali metal or alkaline earth metal of 10.0% by mass or less is preferred in terms of the stability of the hypohalite ions, since decomposition of the hypohalite ions is suppressed. Furthermore, a concentration of 0.0001% by mass or more sufficiently promotes the oxidation of the high-melting-point metal. The alkali metal or alkaline earth metal contained in the removal treatment solution is preferably 0.001 mass % or more and 5.0 mass % or less, and more preferably 0.01 mass % or more and 1.0 mass % or less, relative to the total mass of the removal treatment solution, from the viewpoints of the stability of the removal treatment solution and the oxidation-promoting effect of high-melting-point metals.

[0041] The removal treatment solution may contain two or more of these alkali metals or alkaline earth metals, in which case the total concentration of the alkali metals and alkaline earth metals is preferably 0.005% by mass or more and 5.0% by mass or less, and more preferably 0.01% by mass or more and 1.0% by mass or less.

[0042] As a method for incorporating an alkali metal or alkaline earth metal into the removal treatment solution, a method of adding a salt of an alkali metal or alkaline earth metal, specifically a fluoride, chloride, bromide, iodide, hydroxide, or the like of an alkali metal or alkaline earth metal, to the removal treatment solution can be mentioned, as will be described later.

[0043] (chloride ions or bromide ions) The removal treatment liquid may contain chloride ions or bromide ions to the extent that the object of the present invention is not impaired. When the removal treatment liquid contains hypochlorite ions, it is preferable that it contains chloride ions, and when the removal treatment liquid contains hypobromite ions, it is preferable that it contains bromide ions.

[0044] Chloride ions can be contained in the removal treatment solution by adding, for example, chlorine gas, hydrogen chloride, or a chloride salt, and the content can be adjusted by the mass of chlorine gas, hydrogen chloride, or a chloride salt added to the treatment solution.

[0045] Bromide ions can be contained in the removal treatment solution by adding, for example, bromine gas, hydrogen bromide, or bromide salts, and the content can be adjusted by the mass of bromine gas, hydrogen bromide, or bromide salts added to the treatment solution.

[0046] The concentration of chloride ions or bromide ions is not particularly limited as long as it does not deviate from the objectives of the present invention, but is preferably 0.0001 mol / L or more and 5.0 mol / L or less. A chloride ion or bromide ion concentration of 5.0 mol / L or less can suppress copper corrosion. A chloride ion or bromide ion concentration of 0.0001 mol / L or more can provide a sufficient removal rate (etching rate) of high-melting-point metals. From the viewpoints of suppressing copper corrosion and the etching rate of high-melting-point metals, the concentration of chloride ions or bromide ions contained in the removal treatment solution is preferably 0.001 mol / L or more and 3.0 mol / L or less, and more preferably 0.005 mol / L or more and 1.0 mol / L or less, relative to the total volume of the treatment solution.

[0047] The treatment solution may contain two types of chloride ions or bromide ions, in which case the total concentration of chloride ions and bromide ions is preferably 0.0001 mol / L or more and 5.0 mol / L or less, and more preferably 0.001 mol / L or more and 3.0 mol / L or less.

[0048] (halogen oxygen acid ion) The removal treatment solution may contain halogen oxyacid ions within the scope of the present invention. Specifically, the halogen oxyacid ions are preferably at least one selected from the group consisting of chlorate ions, chlorite ions, bromate ions, and bromite ions.

[0049] Chlorate ions can be contained in the removal treatment solution by adding, for example, chloric acid or a chlorate salt, and the content can be adjusted by the mass of chloric acid or a chlorate salt added to the removal treatment solution.

[0050] Chlorite ions can be contained in the removal treatment solution by adding, for example, chlorous acid or a chlorite salt, and the content can be determined by the mass of chlorous acid or a chlorite salt added relative to the removal treatment solution.

[0051] Bromate ions can be contained in the removal treatment solution by adding, for example, bromic acid or a bromate salt, and the content can be adjusted by the mass of bromic acid or a bromate salt added to the removal treatment solution.

[0052] Bromite ions can be contained in the removal treatment solution by adding, for example, bromous acid or a bromite salt, and the content can be adjusted by the mass of bromous acid or a bromite salt added to the removal treatment solution.

[0053] The concentration of halogen oxyacid ions in the removal treatment solution is not particularly limited as long as it does not deviate from the objectives of the present invention, but is preferably 0.1 mmol / L or more and 1.0 mol / L or less. A halogen oxyacid ion concentration of 1.0 mol / L or less can prevent halogen oxyacid salts from depositing on the copper surface. A halogen oxyacid ion concentration of 0.1 mmol / L or more can prevent copper corrosion. From the viewpoint of preventing the deposition of halogen oxyacid salts on the copper surface and suppressing copper corrosion, the concentration of halogen oxyacid ions is preferably 1.0 mmol / L or more and 0.5 mol / L or less, and more preferably 10.0 mmol / L or more and 0.1 mol / L or less, relative to the total volume of the removal treatment solution. Furthermore, two or more types of these halogen oxyacid ions may be contained in the removal treatment solution. In this case, the total concentration of halogen oxyacid ions is preferably 1.0 mmol / L or more and 0.5 mol / L or less, and more preferably 10 mmol / L or more and 0.1 mol / L or less.

[0054] Furthermore, when the removal treatment liquid contains hypochlorite ions or chloride ions, it is preferable that it contains chlorate ions as halogen oxygen acid ions, and when the treatment liquid contains hypobromite ions or bromide ions, it is preferable that it contains bromate ions as halogen oxygen acid ions.

[0055] (pH) The pH of the removal treatment solution is preferably 7.0 to 14.0. When the pH is 7.0 or higher, the storage stability of the hypohalite ions is good. When the pH is 14.0 or lower, the etching rate for high-melting-point metals is sufficient. The storage stability is an evaluation of the change in concentration of hypohalite ions when the removal treatment solution is stored for a long period of time. The pH of the removal treatment solution is set to pH 9 from the viewpoint of the dissolving ability of high melting point metals and the storage stability of the treatment solution. The pH is more preferably 0.0 to 13.0, and even more preferably 11.0 to 13.0. The pH values ​​here are measured at 25°C.

[0056] An acid or a base can be used to adjust the pH of the removal treatment solution. Examples of bases include inorganic bases (inorganic alkalis) and organic bases (organic alkalis). Inorganic bases consist of metal ions and hydroxide ions, and specific examples include one or more selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, rubidium hydroxide, strontium hydroxide, and barium hydroxide. It is particularly preferable to use an inorganic base to adjust the pH of the removal treatment solution.

[0057] The organic base comprises an organic cation and a hydroxide ion. An example of an organic cation is an onium ion. An onium ion is a polyatomic cation formed by the addition of an excess proton (hydrogen cation) to a monoatomic anion. Specific examples include one or more cations selected from the group consisting of imidazolium ion, pyrrolidinium ion, pyridinium ion, piperidinium ion, ammonium ion, phosphonium ion, fluoronium ion, chloronium ion, bromonium ion, iodonium ion, oxonium ion, sulfonium ion, selenonium ion, telluronium ion, arsonium ion, stibonium ion, and bismuthonium ion. Among these, one or more cations selected from the group consisting of ammonium ion, phosphonium ion, and sulfonium ion are suitable as the organic cation contained in the organic alkali of this embodiment because they are stable in alkaline solutions, the carbon chains and functional groups contained in the onium ion can be easily modified, and the solubility, bulkiness, and charge density can be easily controlled.

[0058] From the viewpoint of industrially inexpensive mass production, the onium ion is more preferably an ammonium ion. Examples of such ammonium ions include tetraalkylammonium ions, and more preferably, tetramethylammonium ions, ethylammonium ions, etc. The organic alkali is at least one selected from the group consisting of trimethylammonium ion, tetraethylammonium ion, propyltrimethylammonium ion, tetrapropylammonium ion, butyltrimethylammonium ion, and tetrabutylammonium ion. An organic alkali containing an onium ion and a hydroxide ion, i.e., onium hydroxide, can be suitably used as the organic alkali. In addition, an ammonium ion (NH4 + An organic alkali containing 2-hydroxyethyltrimethylammonium or 2-hydroxyethyltrimethylammonium as an organic cation can also be suitably used as the organic alkali in this embodiment.

[0059] The organic alkali is particularly preferably a tetraalkylammonium hydroxide, examples of which include one or more selected from the group consisting of tetramethylammonium hydroxide, ethyltrimethylammonium hydroxide, tetraethylammonium hydroxide, propyltrimethylammonium hydroxide, tetrapropylammonium hydroxide, butyltrimethylammonium hydroxide, and tetrabutylammonium hydroxide.

[0060] The acid may be an inorganic acid or an organic acid. Specific examples of inorganic acids include one or more selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and hydrofluoric acid. Specific examples of organic acids include one or more selected from the group consisting of formic acid, acetic acid, citric acid, methanesulfonic acid, and benzoic acid.

[0061] (others) The removal treatment solution may contain metals other than alkali metals and alkaline earth metals, specifically, one or more selected from the group consisting of aluminum, iron, chromium, manganese, nickel, zinc, and lead. These metals may be mixed in during the manufacturing process, eluted from the container, or mixed in from the environment. Because these metals may have a negative effect on the stability of hypohalite ions, the content of each metal is preferably 1 ppm or less, more preferably 200 ppt or less, and most preferably 100 ppt or less.

[0062] The removal treatment solution may contain other additives conventionally used in semiconductor treatment solutions, provided that the purpose of the present invention is not impaired. For example, the other additives may be one or more selected from the group consisting of a water-soluble organic solvent, a fluorine compound, a reducing agent, a complexing agent, a chelating agent, a surfactant, an antifoaming agent, a buffer, and a stabilizer. These additives may be added alone or in combination.

[0063] The removal treatment liquid may contain a solvent. Preferred solvents include those similar to those used in the oxidation treatment liquid. More specifically, water from which metal ions, organic impurities, particles, etc. have been removed by distillation, ion exchange treatment, filtration, various adsorption treatments, etc. is preferred, and pure water and ultrapure water are particularly preferred. Such water can be obtained by known methods widely used in semiconductor manufacturing.

[0064] The removal treatment liquid is preferably stored at low temperature and / or protected from light. Storing the treatment liquid at low temperature and / or protected from light is expected to have the effect of suppressing decomposition of the oxidizing agent in the treatment liquid. Furthermore, storing the treatment liquid in a container filled with an inert gas prevents carbon dioxide from being mixed in, thereby maintaining the stability of the treatment liquid. Furthermore, the inner surface of the container, i.e., the surface that comes into contact with the treatment liquid, is preferably made of glass or an organic polymer material. By forming the inner surface of the container from glass or an organic polymer material, the inclusion of impurities such as metals, metal oxides, and organic substances can be further reduced.

[0065] (Semiconductor substrate etching process) The removal process is an etching process ( Hereinafter, this is referred to as etching treatment. The removal treatment liquid can be used in etching a semiconductor substrate, which includes a step of contacting a semiconductor substrate with the removal treatment liquid. As an example of an etching process using a removal treatment solution, a wet etching process of a substrate (semiconductor substrate) containing ruthenium and copper will be described. First, a substrate made of a semiconductor (e.g., Si) is prepared. The prepared substrate is subjected to a silicon oxidation process to form a silicon oxide film on the substrate. Then, an interlayer insulating film made of a low-dielectric constant (Low-k) film is formed, and via holes are formed at predetermined intervals. After the via holes are formed, a ruthenium film is formed by thermal chemical vapor deposition (CVD). Then, a copper film is formed on the ruthenium film by electroplating. Then, the copper is polished by chemical mechanical polishing (CMP). Then, the substrate is immersed in an oxidation treatment solution to form copper oxide on the copper surface (oxidation treatment step). By etching the excess ruthenium film by a method such as immersion in the removal treatment solution, it is possible to selectively etch ruthenium without corroding or etching copper. Immediately after the oxidation treatment step, a step of washing the oxidation treatment solution with water or the like may be included.

[0066] From the viewpoint of semiconductor manufacturing processes, it is preferable that the ratio of the etching rate of the high-melting point metal to the etching rate of copper (etching rate of the high-melting point metal / etching rate of copper) is 50 or more. This ratio is more preferably 80 or more, and even more preferably 100 or more.

[0067] The temperature during immersion in the oxidation treatment step is not particularly limited, but for example, the temperature is preferably 10°C to 90°C, more preferably 15°C to 60°C, and most preferably 20°C to 50°C. The immersion time in the oxidation treatment step is not particularly limited, but is, for example, 0.1 to 60 minutes, preferably 0.5 to 30 minutes, and more preferably 1 to 10 minutes.

[0068] The temperature when etching a high-melting-point metal using a removal treatment solution is not particularly limited, and may be determined taking into consideration the etching rate of the high-melting-point metal, etc. If the treatment temperature is high, the stability of the hypohalite ion decreases. On the other hand, the etching rate tends to decrease as the temperature decreases. For these reasons, the temperature when etching a high-melting-point metal is preferably 10°C to 90°C, more preferably 15°C to 60°C, and most preferably 20°C to 50°C.

[0069] The contact time between the removal treatment solution and the semiconductor substrate is 0.1 to 60 minutes, preferably 0.5 to 30 minutes, and more preferably 1 to 10 minutes, and can be appropriately selected depending on the etching conditions and the cleaning equipment used. A rinse solution used after using each treatment solution can be appropriately selected from those capable of removing etching residues and particles and organic matter derived from the metal in the treatment solution without corroding the metal on the substrate. Specifically, the rinse solution can be one or more selected from the group consisting of ultrapure water, isopropyl alcohol, ammonia water, hydrofluoric acid, hydrochloric acid, hydrogen peroxide, citric acid aqueous solution, acetic acid, sulfuric acid, ozone water, hydrogen water, a mixture of hydrofluoric acid and hydrogen peroxide, a mixture of sulfuric acid and hydrogen peroxide, a mixture of ammonia water and hydrogen peroxide, and a mixture of hydrochloric acid and hydrogen peroxide.

[0070] <Method of manufacturing semiconductor substrate> Another embodiment of the present invention is a method for manufacturing a semiconductor substrate, including the semiconductor substrate processing method according to one embodiment of the present invention described above. The method for manufacturing a semiconductor substrate may include, in addition to the etching process and other steps described above, known steps used in manufacturing semiconductor substrates, such as one or more steps selected from a wafer fabrication step, an oxide film formation step, a transistor formation step, a wiring formation step, and a CMP step. In the manufacturing method of this embodiment, a semiconductor substrate can be manufactured that includes a metal described above as a high-melting-point metal and a metal, such as copper, whose corrosion potential becomes higher than that of the high-melting-point metal when it comes into contact with a removal treatment liquid. Specific examples of the wiring formation process include: An example of this process will be described with reference to FIG. 1. First, a substrate 11 having a via hole is prepared, and a layer of a high-melting-point metal is formed on the substrate as a seed layer 13. Resist 12 is provided on a predetermined portion of the substrate 11, and then a copper layer 14 is applied by an operation such as electroplating. The metal is planarized by a chemical mechanical polishing process, and then the resist 12 is stripped. Furthermore, the oxidation process described above is performed to form copper oxide on the copper surface. Then, a portion of the seed layer 13 made of the high-melting-point metal is removed by etching with a removal treatment solution. According to the semiconductor substrate manufacturing method of this embodiment, the copper oxide formed by the oxidation process protects the copper surface during the etching process, allowing the high-melting-point metal (e.g., ruthenium) to be selectively removed relative to copper. The copper oxide on the copper surface may be removed by a known method after the step of removing the high-melting point metal, for example, by reduction treatment using hydrogen plasma to remove the copper oxide and re-expose the copper surface. [Example]

[0071] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] (Method for determining hypochlorite ion concentration and hypobromite ion concentration) The concentrations of hypochlorite ions and hypobromite ions were measured using an ultraviolet-visible spectrophotometer (UV-2600, manufactured by Shimadzu Corporation). Calibration curves were prepared using aqueous solutions of hypobromite ions and hypochlorite ions with known concentrations, and the concentrations of hypochlorite ions and hypobromite ions in each treatment solution were determined. The concentrations of hypochlorite ions and hypobromite ions were determined from the measurement data when the absorption spectrum stabilized after the treatment solution was produced.

[0073] (Method for determining alkali metal and alkaline earth metal concentrations) The concentrations of alkali metals and alkaline earth metals in each treatment solution were analyzed using a high-frequency inductively coupled plasma optical emission spectrometer (iCAP6500DuO, manufactured by Thermo Scientific). Each treatment solution was diluted with ultrapure water to an appropriate concentration, and then nitric acid (Kanto Chemical, Ultrapure) was added to adjust the pH to 1 or less. Each adjusted treatment solution was introduced into the device. and analyzed for metal concentrations.

[0074] (Method for determining halide ion and halogen oxyacid ion concentrations) The concentrations of halide ions and halogen oxyacid ions were analyzed using an ion chromatography analyzer (DIONEX INTEGRION HPLC, manufactured by Thermo Scientific). KOH was used as the eluent, and an ion analysis column for hydroxide-based eluents (AS15, manufactured by Thermo Scientific) was used. After removing background noise with a suppressor, the halide ions and halogen oxyacid ions in the treatment solution were quantified using an electrical conductivity detector.

[0075] (pH measurement method) The pH of 10 mL of the treatment solution prepared in the Examples and Comparative Examples was measured using a benchtop pH meter (LAQUA F-73, manufactured by Horiba, Ltd.). Prior to measurement of the treatment solution, the pH was calibrated using a neutral phosphate pH standard solution (pH 6.86, manufactured by Kanto Chemical), a borate pH standard solution (pH 9.18, manufactured by Kanto Chemical), and a pH 13.00 standard solution (manufactured by Hanna Instruments). The pH measurement was performed after the treatment solution was prepared and stabilized at 25±1°C.

[0076] (evaluation) Using the produced treatment solution, the etching rate of ruthenium, the etching rate of copper, and the deposits on the copper surface were evaluated by the methods described below.

[0077] (Oxidation treatment process and high melting point metal removal process) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a copper film was then formed on top of it using a sputtering method to a thickness of 200 Å (±10%). 40 mL of the removal treatment solution was prepared in a fluororesin container with a lid (AsOne, PFA container 94.0 mL). A 10 mm x 10 mm copper film piece cut from the 200 Å copper film-coated wafer was immersed in a chemical solution containing an oxidizing agent (oxidation treatment solution) at 25°C for 1 minute and then rinsed with ultrapure water. This resulted in the formation of copper oxide on the surface, forming a post-oxidation copper film. The resulting copper film after oxidation treatment was immersed in an etching solution (removal treatment solution) for high melting point metals at 25° C. for 2 minutes, and then washed with ultrapure water to obtain an etched copper film. (Ruthenium etching rate) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a ruthenium film was then formed thereon using a sputtering method to a thickness of 1200 Å (±10%). The sheet resistance of the ruthenium was measured using a four-point probe resistivity meter (Loresta-GP, Mitsubishi Chemical Analytech Co., Ltd.) and converted to film thickness, which was used as the ruthenium film thickness before etching. 40 mL of the removal treatment solution was prepared in a fluororesin container with a lid (AsOne, PFA container, 94.0 mL). A 10 × 10 mm ruthenium film piece cut from a wafer with a 1200 Å ruthenium film was immersed in the treatment solution at a specified temperature for 2 minutes to obtain the treated ruthenium film. The thickness of the treated ruthenium film was measured using the method described above, and the etching rate was determined by dividing the difference in film thickness before and after treatment by the treatment time. The etching rate of ruthenium was evaluated according to the following criteria. A:100Å / min or more B: 50Å / min or more and less than 100Å / min C: 10 Å / min or more and less than 50 Å / min D: Less than 10Å / min

[0078] (Evaluation of the stability of ruthenium etching rate) A 10 x 10 mm ruthenium film piece cut from a wafer with a ruthenium film having a thickness of 1200 Å formed by the above method was immersed in a removal treatment solution at 25°C for 2 minutes, and the ruthenium film thickness was measured according to the method described above and recorded as the film thickness after etching. This was recorded as the etching rate immediately after preparation of the treatment solution, and the etching rate was subsequently evaluated every week using the method described above. The number of days during which the obtained etching rate remained within ±20% of the etching rate immediately after preparation of the treatment solution was defined as the stability of the etching rate (days), and was evaluated according to the following criteria. A: 180 days or more B: 120 days or more and 179 days or less C: 60 days or more and 119 days or less D: 59 days or less

[0079] (Copper etching rate) 40 mL of the removal treatment solution was prepared in a fluororesin container with a lid (AsOne, PFA container 94.0 mL). A 10 mm x 10 mm copper film piece cut from a wafer with a copper film of 200 Å thickness was immersed in the ruthenium etching treatment solution at a predetermined temperature for 1 hour. The copper dissolved in the solution was analyzed using a high-frequency inductively coupled plasma optical emission spectrometer (iCAP6500DuO, Thermo Scientific). The amount of copper dissolved was calculated based on the density of copper, 8.96 g / cm. 3 The copper etching rate was calculated by dividing the amount of elution calculated as the film thickness by the treatment time. The corrosion of copper was evaluated according to the following criteria. A: Less than 1Å / min B: 1Å / min or more and 10Å / min or less C: More than 10Å / min

[0080] (Evaluation of copper surface after etching) The surface of the copper film obtained in the oxidation treatment step and the high-melting-point metal removal step was observed with a field emission scanning electron microscope (JSM-7800F Prime, manufactured by JEOL Ltd.) and evaluated according to the following evaluation criteria. A: No precipitates B: Precipitation in some areas C: Partially precipitated D: Precipitates present throughout

[0081] <Examples 1 to 3> A solution containing an oxidizing agent (oxidation treatment solution) to be used in the oxidation step was prepared as follows, so as to have the composition shown in Table 1. Sodium chlorate (special grade, content 99%, manufactured by Kishida Chemical Co., Ltd.) and ultrapure water were added to a 100 mL fluororesin container to obtain the oxidation treatment solution. Next, a treatment liquid (removal treatment liquid) to be used in the high-melting-point metal removal step was prepared as follows, so as to have the composition shown in Table 1. Sodium hypochlorite pentahydrate (nickel oxide pentahydrate, manufactured by Nippon Light Metal Co., Ltd.), ultrapure water, and a 10% aqueous solution of sodium hydroxide (special grade, manufactured by Kanto Chemical Co., Ltd.) were added to a 100 mL fluororesin container to obtain the removal treatment liquid. The obtained treatment solution was used to carry out the oxidation treatment step and the high-melting-point metal removal step, and the evaluations shown in Table 1 were carried out.

[0082] Example 4 As shown in FIG. 2, a 25% by mass aqueous solution of tetramethylammonium hydroxide (SD-25, manufactured by Tokuyama Corporation) and ultrapure water were mixed in a 2 L three-necked glass flask 21 (manufactured by Cosmos Bead Co., Ltd.) to obtain a 0.63 mol / L aqueous solution of tetramethylammonium hydroxide. Next, a rotor 24 (manufactured by AsOne, total length 30 mm × diameter 8 mm) was placed in the three-neck flask 21, a thermometer protection tube 22 (manufactured by Cosmos Bead, bottom-sealed type) and a thermometer 23 were placed in one opening, a chlorine gas cylinder and a nitrogen gas cylinder were connected to the other opening, and the tip of a PFA tube 25 (manufactured by Flon Industries, F-8011-02) was immersed in the bottom of the solution in a state where it was possible to switch between chlorine gas and nitrogen gas as desired, and the remaining opening was connected to a gas washing bottle 26 (manufactured by AsOne, gas washing bottle, model number 2450 / 500) filled with a 5% by mass aqueous solution of sodium hydroxide 27. Thereafter, a magnetic stirrer (C-MAG HS10, manufactured by AsOne) was placed at the bottom of the three-neck flask 21 and rotated at 300 rpm to stir the mixture, and chlorine gas (purity 99.999 or higher, manufactured by ADEKA) was supplied at a flow rate of 38 mL / min while the outer periphery of the three-neck flask was cooled with ice water 20. The concentration of the obtained aqueous tetramethylammonium hypochlorite solution was 0.31 mol / L, and the pH was 12.0. Ultrapure water and a 10% aqueous solution of sodium hydroxide were added to the obtained aqueous solution of tetramethylammonium hypochlorite to obtain a removal treatment liquid shown in Table 1. Using the oxidizing treatment liquid and the removing treatment liquid prepared in the same manner as in Example 2, the evaluations listed in Table 1 were carried out. In FIG. 2, reference numeral 28 denotes a flow meter, and reference numeral 29 denotes a water bath.

[0083] <Example 5> As shown in Figure 3, one end of a 100 mL PFA trap bottle 16 (manufactured by Fluorochemical Co.) was connected to a nitrogen cylinder so that nitrogen gas could be supplied. The other end was connected to a 500 mL PFA trap bottle 17 (manufactured by Fluorochemical Co.). 20 mL of bromine (purity >98%, manufactured by Tokyo Chemical Industry Co.) was added to the 100 mL PFA trap bottle 16. It was confirmed that the tip of the PFA tube 19 was not in contact with the liquid bromine. A 10% aqueous solution of sodium hydroxide (special grade, manufactured by Kanto Chemical Co.) and ultrapure water were added to the 500 mL PFA trap bottle 17 to obtain a 0.34 mol / L aqueous solution of sodium hydroxide. Next, a stirring bar 18 was placed in a 500 mL PFA trap bottle 17. A magnetic stirrer (AsOne, C-MAG HS10) was placed below the 500 mL PFA trap bottle 17 and rotated at 300 rpm to stir the contents. Nitrogen was supplied to the 100 mL PFA trap bottle 16 at a flow rate of 100 cc / min, and gasified bromine was supplied to the subsequent 500 mL PFA trap bottle 17 for 300 minutes, yielding a 0.12 mol / L sodium hypobromite aqueous solution with a pH of 12.0. A 10% sodium hydroxide aqueous solution and ultrapure water were added to the resulting sodium hypobromite aqueous solution to obtain the removal treatment solution listed in Table 1. Using the oxidizing treatment liquid and the removing treatment liquid prepared in the same manner as in Example 2, the evaluations listed in Table 1 were carried out. In FIG. 3, reference numeral 15 denotes a flow meter.

[0084] Example 6 A treatment solution to be used in the high-melting-point metal removal step was obtained in the same manner as in Example 5, except that the liquid into which bromine gas was injected was changed from 0.34 mol / L aqueous sodium hydroxide solution to 0.34 mol / L aqueous tetramethylammonium hydroxide solution so as to have the composition shown in Table 1. Using the oxidizing treatment liquid and the removing treatment liquid prepared in the same manner as in Example 2, the evaluations listed in Table 1 were carried out.

[0085] <Examples 7 to 9> A treatment solution was obtained in the same manner as in Example 1, except that sodium bromate (content >99.5%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of sodium chlorate to prepare the oxidation treatment solution so that the composition was as shown in Table 1. The resulting treatment liquid was used to carry out the evaluations listed in Table 1.

[0086] Example 10 The oxidation treatment liquid prepared in the same manner as in Example 8 and the removal treatment liquid prepared in the same manner as in Example 4 were used to carry out the evaluations listed in Table 1.

[0087] Example 11 Using an oxidation treatment liquid prepared in the same manner as in Example 8 and a removal treatment liquid prepared in the same manner as in Example 5, the evaluations listed in Table 1 were carried out.

[0088] Example 12 Using an oxidation treatment liquid prepared in the same manner as in Example 8 and a removal treatment liquid prepared in the same manner as in Example 6, the evaluations listed in Table 1 were carried out.

[0089] <Examples 13 to 15> A treatment solution was obtained in the same manner as in Example 1, except that sodium iodate (content >99.5%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of sodium chlorate to prepare the oxidation treatment solution so that the composition was as shown in Table 1. The resulting treatment liquid was used to carry out the evaluations listed in Table 1.

[0090] Example 16 The oxidation treatment liquid prepared in the same manner as in Example 14 and the removal treatment liquid prepared in the same manner as in Example 4 were used to carry out the evaluations listed in Table 1.

[0091] Example 17 Using an oxidation treatment liquid prepared in the same manner as in Example 14 and a removal treatment liquid prepared in the same manner as in Example 5, the evaluations listed in Table 1 were carried out.

[0092] Example 18 The oxidation treatment liquid prepared in the same manner as in Example 14 and the removal treatment liquid prepared in the same manner as in Example 6 were used to carry out the evaluations listed in Table 1.

[0093] <Examples 19 to 21> Potassium hexacyanidoferrate (III) (purity >99.0%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and ultrapure water were mixed to obtain the composition shown in Table 1, thereby obtaining an oxidation treatment liquid. Using the obtained oxidation treatment liquid and a removal treatment liquid prepared in the same manner as in Example 1, the various evaluations listed in Table 1 were carried out.

[0094] <Example 22> Using an oxidation treatment liquid prepared in the same manner as in Example 20 and a removal treatment liquid prepared in the same manner as in Example 4, the evaluations listed in Table 1 were carried out.

[0095] Example 23 Using an oxidation treatment liquid prepared in the same manner as in Example 20 and a removal treatment liquid prepared in the same manner as in Example 5, the evaluations listed in Table 1 were carried out.

[0096] Example 24 Using an oxidation treatment liquid prepared in the same manner as in Example 20 and a removal treatment liquid prepared in the same manner as in Example 6, the evaluations listed in Table 1 were carried out. Example 25 Ammonium peroxodisulfate (purity >99.0%, Fujifilm Wako Pure Chemical Industries, Ltd.) and ultrapure water were added to obtain the composition shown in Table 1, thereby obtaining an oxidation treatment liquid. Using the resulting treatment liquid and a removal treatment liquid prepared in the same manner as in Example 1, the evaluations listed in Table 1 were carried out. <Example 26> Using an oxidation treatment liquid prepared in the same manner as in Example 25 and a removal treatment liquid prepared in the same manner as in Example 5, the evaluations listed in Table 1 were carried out.

[0097] <Comparative Example 1> The removal treatment liquid used in Example 1 was used without carrying out the oxidation treatment step, and the evaluations listed in Table 1 were carried out.

[0098] <Comparative Example 2> The removal treatment liquid used in Example 5 was used without carrying out the oxidation treatment step, and the evaluations listed in Table 1 were carried out. [Table 1]

[0099] As is clear from the results shown in Table 1, by treating a semiconductor substrate with a method according to one embodiment of the present invention, high-melting-point metals such as ruthenium contained in the semiconductor substrate can be selectively removed relative to copper, and precipitates on the copper surface can be suppressed. [Explanation of symbols]

[0100] 11 Circuit Board 12 Resist 13 Seed layer 14 Metal layer 15 Flow meter 16 100mL PFA trap bottles 17 500mL PFA trap bottles 18 rotor 19 PFA tube 20 Ice water 21 Three-neck flask 22 Thermometer protection tube 23 Thermometer 24 rotor 25 PFA tubing 26 Gas washing bottle 27 5% by mass sodium hydroxide aqueous solution 28 Flow meter 29 Water Bath

Claims

1. 1. A method for processing a semiconductor substrate comprising a refractory metal and copper, the method comprising: an oxidation treatment step of forming copper oxide on the surface of the copper; and removing the high-melting-point metal after the oxidation treatment step.

2. The method according to claim 1 , wherein the oxidation treatment step is a step of contacting the semiconductor substrate with a solution containing an oxidizing agent.

3. 3. The method of claim 2, wherein the oxidizing agent is at least one selected from the group consisting of a hexacyanide metal complex and a halogen oxygen acid ion.

4. 2. The method according to claim 1, wherein the step of removing the high-melting point metal is a step of contacting the semiconductor substrate with a treatment liquid containing hypohalite ions.

5. 2. The method of claim 1, wherein the refractory metal is one or more metals selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium.

6. A method for manufacturing a semiconductor substrate, comprising the method according to any one of claims 1 to 5.

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