Treatment liquid for semiconductor substrate

Abstract

Provided is a treatment liquid for a semiconductor substrate for removing a high melting point metal from a semiconductor substrate containing said high melting point metal, the treatment liquid containing one or more metals selected from an alkali metal and an alkaline earth metal, and an oxidizing agent. The oxidizing agent is at least one element selected from the group consisting of hypohalous acid ions, metal complexes, and salts thereof, and has a pH of 7–14 at 25°C.

Description

Semiconductor substrate processing solution

[0001] The present invention relates to a processing solution for semiconductor substrates.

[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 have traditionally been used, such as aluminum and copper. Metal wiring is formed on a pattern exposed on an insulating film, but as the wiring width becomes narrower, the metal fillability deteriorates, leading to problems such as short circuits due to the formation of voids. 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. Cobalt and ruthenium are being considered as metals for use in the liner layer 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. If the wiring metal is also etched during wet etching of the metal liner layer, the surface roughness can increase resistance and risk of short circuits. Therefore, a processing solution that selectively etches only the metal liner layer is needed.

[0005] Furthermore, it is known that if a metal more noble than the wiring metal is used for the liner layer, the corrosion potential difference between them acts as a driving force to cause galvanic corrosion, which can lead to the risk of short circuits due to the elution of the wiring metal.

[0006] JP 2004-172576 A JP 2023-98232 A

[0007] Patent Document 1 discloses an etching solution that contains an aqueous hydrofluoric acid solution and a copper corrosion inhibitor, and the corrosion inhibitor forms a protective film on the copper surface that prevents corrosion of the copper, thereby preventing galvanic corrosion of metals that are more base than copper. However, it has been found that the etching solution in this document can prevent copper corrosion, but cannot etch high-melting-point metals such as ruthenium.

[0008] Patent Document 2 discloses a cleaning solution for cleaning a substrate on which ruthenium and metal atoms other than ruthenium are present adjacently, the cleaning solution containing at least one hydrazine compound, an amine other than the hydrazine compound, and a quaternary hydroxide, and capable of reducing galvanic corrosion. However, the cleaning solution in this document is intended to remove copper oxide shavings generated on the substrate after CMP or via formation, and it was found that while it can etch copper oxide, it cannot etch high-melting-point metals such as ruthenium.

[0009] Therefore, the present invention provides a treatment solution for semiconductor substrates that can remove high-melting-point metals such as ruthenium contained in semiconductor substrates. The present invention also provides a treatment solution for semiconductor substrates that, when a semiconductor substrate comes into contact with a metal other than the high-melting-point metal (e.g., copper), can selectively remove the high-melting-point metal over the other metal by increasing the corrosion potential of the other metal (e.g., copper) in the treatment solution compared to the high-melting-point metal.

[0010] The present inventors have conducted extensive research to solve the problem of removing high-melting-point metals such as ruthenium contained in semiconductor substrates, and have found that high-melting-point metals can be selectively removed by using a treatment solution containing hypohalite ions, an alkali metal or alkaline earth metal, and halide ions. Furthermore, they have found that when a semiconductor substrate contains, in addition to the high-melting-point metal, a metal that causes galvanic corrosion in contact with the high-melting-point metal, for example, when the semiconductor substrate contains copper, galvanic corrosion of the metal can be prevented.

[0011] That is, the gist of the present invention is specifically as follows: [1] A treatment solution for a semiconductor substrate for removing a high-melting point metal from a semiconductor substrate containing the high-melting point metal, the treatment solution for a semiconductor substrate comprising one or more metals selected from alkali metals and alkaline earth metals, and an oxidizing agent, the oxidizing agent being one or more selected from the group consisting of hypohalite ions, metal complexes, and salts thereof, and having a pH of 7 to 14 at 25° C. [2] The treatment solution for a semiconductor substrate according to [1], wherein the semiconductor substrate further contains copper, and the high-melting point metal is one or more selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium, is used to selectively remove the high-melting point metal relative to the copper. [3] The semiconductor substrate treatment solution according to [1] or [2], wherein the semiconductor substrate treatment solution is an etching solution, the semiconductor substrate contains a refractory metal and copper, and when the semiconductor substrate is treated with the etching solution, the ratio of the etching rate of the refractory metal to the etching rate of the copper is 50 or more. [4] The semiconductor substrate treatment solution according to any of [1] to [3], wherein the alkali metal is at least one selected from the group consisting of sodium and potassium. [5] The semiconductor substrate treatment solution according to any of [1] to [4], wherein the alkaline earth metal is at least one selected from the group consisting of magnesium and calcium. [6] The semiconductor substrate treatment solution according to any of [1] to [5], further containing a halogen oxyacid ion. [7] A method for treating a semiconductor substrate containing a refractory metal and copper, comprising the step of selectively removing the refractory metal relative to the copper contained in the semiconductor substrate using the semiconductor substrate treatment solution according to any of [1] to [6]. [8] A method for manufacturing a semiconductor substrate containing a high-melting point metal and copper, comprising a step of selectively removing the high-melting point metal relative to the copper contained in the semiconductor substrate using the treatment solution for semiconductor substrate according to any one of [1] to [6].

[0012] According to the present invention, a treatment solution can be provided that has a sufficient etching rate for high-melting-point metals, particularly ruthenium, contained in semiconductor substrates, and that, when the semiconductor substrate contains a metal that causes galvanic corrosion, such as copper, does not cause corrosion of copper due to galvanic corrosion even when the high-melting-point metal and copper are in contact with each other.

[0013] It is a schematic diagram of a wiring formation process using the treatment liquid of the present embodiment. It is a schematic diagram of an apparatus used for preparing a sodium hypobromite aqueous solution used in the examples. It is a schematic diagram of an apparatus used for preparing a tetramethylammonium hypochlorite aqueous solution used in the examples.

[0014] Although the present invention will be described in detail below with reference to the preferred embodiments, the present invention is not limited to these embodiments as long as they do not depart from the spirit of the present invention. Furthermore, the present invention can be implemented by modifying it as desired within the scope of the present invention.

[0015] (Treatment liquid for semiconductor substrate) The treatment liquid for semiconductor substrate of this embodiment contains one or more metals selected from alkali metals or alkaline earth metals, and an oxidizing agent, wherein the oxidizing agent is one or more selected from hypohalite ions, metal complex salts, and salts thereof, and has a pH of 7 or more and 14 or less at 25°C.

[0016] (Processing Object: Semiconductor Substrate) Using the processing solution of this embodiment, for example, it is possible to etch a refractory metal film formed on a semiconductor substrate. The processing object of this embodiment is a semiconductor substrate containing at least a refractory metal. That is, the processing object includes at least the substrate and the refractory metal on the substrate. Examples of the semiconductor substrate include various substrates such as semiconductor wafers, glass substrates, and organic resin substrates. Furthermore, even when the semiconductor substrate contains another metal in addition to the refractory metal and the other metal is in contact with the refractory metal, the refractory metal can be removed while suppressing galvanic corrosion of the other metal. An example of such another metal is copper. By treating a semiconductor substrate containing multiple metals with different corrosion potentials with the processing solution of this embodiment, it is possible to remove only the metal to be removed while suppressing corrosion of the other metal (e.g., copper) driven by the corrosion potential difference. Therefore, the processing solution of this embodiment does not require the addition of a copper corrosion inhibitor as described in Patent Document 1. When the treatment solution of this embodiment is used on a semiconductor substrate containing a refractory metal and copper, it is possible to selectively etch the refractory metal and suppress galvanic corrosion of the copper. The treatment solution of this embodiment is suitable for selectively removing refractory metals, and is also suitable as a treatment solution for suppressing galvanic corrosion of metals such as copper when the substrate contains a metal that causes galvanic corrosion. Specific examples of refractory metals include metals with melting points of 1400°C or higher, such as one or more selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium, including alloys, oxides, nitrides, oxynitrides, etc. of these metals. Among these, ruthenium, molybdenum, or tungsten is preferred, and ruthenium is most preferred.

[0017] (Oxidizing Agent) The treatment solution of this embodiment contains an oxidizing agent for the purpose of oxidizing and dissolving the high-melting-point metal. The oxidizing agent is one or more selected from the group consisting of hypohalite ions, metal complexes, and salts thereof (also referred to as metal complex salts). The hypohalite ions include one or more hypohalite ions selected from the group consisting of hypobromite ions and hypochlorite ions. The concentration 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 1.0 mol / L or less. If the concentration of the hypohalite ions exceeds 1.0 mol / L, the function as an oxidizing agent may be reduced due to decomposition of the hypohalite ions. If the concentration of the hypohalite ions is less than 0.0001 mol / L, the etching rate of the high-melting-point metal may be extremely slow, and the treatment solution may no longer function. In terms of the stability of the treatment solution and the ability to dissolve high-melting-point metals, the concentration of hypohalite ions contained in the treatment solution of this embodiment is preferably 0.001 mol / L to 0.5 mol / L, and more preferably 0.005 mol / L to 0.1 mol / L, relative to the total mass of the treatment solution. Only one type of hypohalite ion may be used, or two or more types of hypohalite ions may be used. The concentration range of the hypohalite ions refers to the concentration range of one type when hypochlorite ions or hypobromite ions are used alone, and refers to the combined concentration range of two or more types when two or more types are used.

[0018] Methods for incorporating one or more hypohalite ions selected from the group consisting of hypobromite ions and hypochlorite ions into the 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.

[0019] The metal complex may be one or more selected from the group consisting of a hexacyanide metal complex, a permanganate complex, and a cerium complex. The concentration is not particularly limited as long as it does not deviate from the objectives of the present invention, but is preferably 0.001 mol / L to 3.0 mol / L. If the metal complex concentration exceeds 3.0 mol / L, a deposit of the metal complex may remain on the substrate after treatment. If the metal complex concentration is less than 0.001 mol / L, the etching rate of the high-melting-point metal may become extremely slow, and the treatment solution may no longer function. The hypohalite ions contained in the treatment solution of this embodiment are preferably 0.01 mol / L to 2.0 mol / L, more preferably 0.05 mol / L to 1.5 mol / L, relative to the total mass of the treatment solution, in order to prevent deposition on the substrate and dissolve the high-melting-point metal. Only one type of metal complex may be used, or two or more types of metal complexes may be included. When a single metal complex is contained, the concentration range of that metal complex is indicated. When two or more metal complexes are contained, the combined concentration range is indicated. Methods for incorporating one or more metal complexes selected from the group consisting of hexacyanide metal complexes, such as hexacyanide iron(III) complexes, permanganate complexes, and cerium complexes, such as cerium(IV) complexes, into the treatment solution include adding a metal complex salt. Metal complex salts are salts of metal complexes and cations, specifically, potassium hexacyanide iron(III), potassium permanganate, and diammonium cerium(IV) nitrate. The treatment solution of this embodiment may also contain the hypohalite ions and metal complexes simultaneously. When hypohalite ions and metal complexes are contained simultaneously, they are preferably contained within the individual concentration ranges described above.

[0020] (Alkali Metal or Alkaline Earth Metal) The treatment liquid of this embodiment contains an alkali metal or alkaline earth metal. Specific examples of alkali metals include Na, K, and Rb. Specific examples of alkaline earth metals include 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 liquid 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 objectives of the present invention, but is preferably 0.0001% by mass or more and 10.0% by mass or less. If the concentration of the alkali metal or alkaline earth metal exceeds 10.0% by mass, the decomposition of hypohalite ions is promoted, which may reduce the stability of the hypohalite ions. Furthermore, if the concentration is less than 0.0001% by mass, the oxidation promoter effect for the high-melting-point metal may not be obtained. In terms of the stability of the treatment solution and the oxidation-promoting effect of the high-melting-point metal, the alkali metal or alkaline earth metal contained in the treatment solution of this embodiment is preferably 0.001% by mass to 5.0% by mass, and more preferably 0.01% by mass to 1.0% by mass, relative to the total mass of the treatment solution. Two or more of these alkali metals or alkaline earth metals may be contained in the treatment solution. In this case, the total concentration of the alkali metals and alkaline earth metals is preferably 0.005% by mass to 5.0% by mass, and more preferably 0.01% by mass to 1.0% by mass. An example of a method for adding an alkali metal or alkaline earth metal to the treatment solution is to add a salt of the alkali metal or alkaline earth metal to the treatment solution, specifically a fluoride, chloride, bromide, iodide, or hydroxide of the alkali metal or alkaline earth metal, as described below.

[0021] (Chloride Ions or Bromide Ions) The treatment solution of this embodiment may contain chloride ions or bromide ions as long as the object of the present invention is not impaired. When the treatment solution contains hypochlorite ions, it preferably contains chloride ions. When the treatment solution contains hypobromite ions, it preferably contains bromide ions. Chloride ions can be added to the treatment solution, for example, by chlorine gas, hydrogen chloride, or a chloride salt. The content can be adjusted by the weight of chlorine gas, hydrogen chloride, or a chloride salt added to the treatment solution. Bromide ions can be added to the treatment solution, for example, by bromine gas, hydrogen bromide, or a bromide salt. The content can be adjusted by the weight of bromine gas, hydrogen bromide, or a bromide salt added to the treatment solution. The concentration of chloride ions or bromide ions 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 and 5.0 mol / L or less. If the chloride ion or bromide ion concentration exceeds 5.0 mol / L, galvanic corrosion of copper or the like may be accelerated. If the chloride ion or bromide ion concentration is less than 0.0001, the etching rate of high-melting-point metals may decrease. In terms of suppressing galvanic corrosion of copper or the like and improving the etching rate of high-melting-point metals, the concentration of chloride ions or bromide ions contained in the treatment solution of this embodiment 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 mass of the treatment solution. Furthermore, two types of chloride ions or bromide ions may be contained in the treatment solution. In this 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.

[0022] (Halogen Oxygen Acid Ions) The treatment solution of this embodiment may contain halogen oxygen acid ions, provided that the object of the present invention is not impaired. Specifically, the halogen oxygen acid ions are preferably one or more selected from the group consisting of chlorate ions, chlorite ions, bromate ions, and bromite ions. Chlorate ions can be added to the treatment solution, for example, by chloric acid or a chlorite salt. Furthermore, the content can be adjusted by the weight of chloric acid or a chlorite salt added to the treatment solution. Chlorite ions can be added to the treatment solution, for example, by chlorous acid or a chlorite salt. Furthermore, the content can be adjusted by the weight of chlorous acid or a chlorite salt added to the treatment solution. Bromate ions can be added to the treatment solution, for example, by bromic acid or a bromate salt. Furthermore, the content can be adjusted by the weight of chloric acid or a chlorite salt added to the treatment solution. Bromite ions can be added to the treatment solution, for example, by bromous acid or a bromate salt. Furthermore, the content can be adjusted by the weight of chloric acid or a chlorite salt added to the treatment solution. Bromite ions can be added to the treatment solution, for example, by bromous acid or a bromite salt. The content can be adjusted by adjusting the weight of bromous acid or bromite salt added to the treatment solution. The concentration of the halogen oxyacid ions 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 exceeding 1.0 mol / L may accelerate copper corrosion. A halogen oxyacid ion concentration less than 0.1 mmol / L may not suppress the copper etching rate. From the viewpoint of copper corrosion inhibition, the concentration of the 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 mass of the treatment solution. Two or more of these halogen oxyacid ions may be contained in the treatment solution. In this case, the total concentration of the 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.Furthermore, when the treatment liquid contains hypochlorite ions and chloride ions, it is preferable that it contains chlorate ions as halogen oxygen acid ions, and when the treatment liquid contains hypobromite ions and bromide ions, it is preferable that it contains bromate ions as halogen oxygen acid ions.

[0023] (pH) The pH of the treatment liquid of this embodiment is preferably 7.0 to 14.0. The reason for the existence of a preferred pH range is that if the pH is too low, the storage stability of the hypohalite ions deteriorates, and if the pH is too high, the etching rate for high-melting-point metals slows. Storage stability is an evaluation of the change in concentration of hypohalite ions when the treatment liquid is stored for an extended period of time. From the viewpoints of the dissolving ability of high-melting-point metals and the storage stability of the treatment liquid, the pH of the treatment liquid of this embodiment is preferably 9.0 to 13.0, and more preferably 11.0 to 13.0. The pH of the treatment liquid is measured at 25°C.

[0024] An acid or a base can be used to adjust the pH of the treatment solution of this embodiment. Examples of bases include inorganic bases. Inorganic bases are composed of metal ions and hydroxide ions, specifically, 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 in the treatment solution of this embodiment. The treatment solution of this embodiment does not necessarily require the use of an organic base. Examples of acids include inorganic acids and organic acids. 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.

[0025] (Others) The treatment solution of this embodiment may contain alkali metals and metals other than alkali metals, specifically 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 have a negative effect on the stability of hypohalite ions, the content of each metal is preferably 1 ppm or less, and more preferably 1 ppb or less.

[0026] The treatment liquid of this embodiment may contain other additives that have been conventionally used in semiconductor treatment liquids, as long as the purpose of the present invention is not impaired. For example, other additives that can be added include water-soluble organic solvents, fluorine compounds, reducing agents, complexing agents, chelating agents, surfactants, antifoaming agents, buffering agents, and stabilizers. These additives may be added alone or in combination.

[0027] The water contained in the treatment solution of this embodiment 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 is particularly preferably pure water or ultrapure water. Such water can be obtained by known methods widely used in semiconductor manufacturing.

[0028] The treatment liquid of this embodiment 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. This is because, if the inner surface of the container is made of glass or an organic polymer material, the inclusion of impurities such as metals, metal oxides, and organic substances can be further reduced.

[0029] (Etching Treatment of Semiconductor Substrate) The treatment solution of this embodiment can be used in the etching treatment of a semiconductor substrate. The treatment solution of this embodiment can be used as an etching solution. The etching treatment includes a step of contacting a semiconductor substrate with the treatment solution of this embodiment. As an example of an etching treatment performed using the treatment solution of this embodiment, a wet etching treatment 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 an oxidation treatment to form a silicon oxide film on the substrate. Then, an interlayer insulating film made of a 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 CVD. Then, a copper film is formed on the ruthenium film by electrolytic plating. The copper is polished by CMP polishing, and the excess ruthenium film is etched using the treatment solution of this embodiment, making it possible to selectively etch ruthenium without corroding copper. The greater the ratio of the etching rate of the refractory metal to the etching rate of the metal that causes galvanic corrosion, such as copper, the more easily the refractory metal can be etched without corroding the metal that causes galvanic corrosion (e.g., copper). A ratio of the etching rate of the refractory metal to the etching rate of the metal that causes galvanic corrosion (e.g., copper) of 50 or greater can be used in semiconductor manufacturing processes. This ratio is more preferably 80 or greater, and even more preferably 100 or greater.

[0030] The temperature when etching a high-melting-point metal using the treatment solution of this embodiment is not particularly limited, but 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 ions 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.

[0031] The time for using the treatment solution of this embodiment is in the range of 0.1 to 60 minutes, preferably 0.5 to 30 minutes, and more preferably 1 to 10 minutes, and may be appropriately selected depending on the etching conditions and the cleaning equipment used. A rinse solution used after using the treatment solution of this embodiment may be selected from those capable of removing etching residues and metal-derived particles and organic matter in the treatment solution without corroding the metal on the substrate. Specifically, the rinse solution may 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.

[0032] (Method of Manufacturing a Semiconductor Substrate) Another aspect of this embodiment is a method of manufacturing a semiconductor substrate that includes the etching treatment of the semiconductor substrate described above as one step. In addition to the etching treatment described above, the method of manufacturing a semiconductor substrate may include 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. The manufacturing method of this embodiment can produce a semiconductor substrate that includes a metal described above as a refractory metal and a metal, such as copper, whose corrosion potential becomes higher than that of the refractory metal upon contact with the treatment liquid. A specific wiring formation step will be described with reference to FIG. 1 . First, a substrate 11 having a via hole is prepared, and a layer of a refractory metal is formed on the substrate as a seed layer 13. A resist 12 is provided in a predetermined portion of the substrate 11, and then a layer 14 of a metal (e.g., copper) whose corrosion potential becomes higher than that of the refractory metal upon contact with the treatment liquid is applied by an operation such as electroplating. After planarizing the metal by chemical mechanical polishing, a process for stripping the resist 12 is performed, and a portion of the seed layer 13 made of a high-melting-point metal is removed by etching with the processing liquid. According to the method for manufacturing a semiconductor substrate of this embodiment, galvanic corrosion driven by the difference in corrosion potential in the processing liquid is suppressed during the etching process, and the high-melting-point metal (e.g., ruthenium) can be selectively removed relative to a metal (e.g., copper) whose corrosion potential becomes higher than that of the high-melting-point metal upon contact with the processing liquid.

[0033] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0034] (Method for quantifying hypochlorite ion concentration and hypobromite ion concentration) The hypochlorite ion and hypobromite ion concentrations were measured using an ultraviolet-visible spectrophotometer (UV-2600, manufactured by Shimadzu Corporation). A calibration curve was created using aqueous solutions of hypobromite ions and hypochlorite ions with known concentrations, and the concentrations of hypochlorite ions and hypobromite ions in the treatment solution for manufactured semiconductor substrates were determined. The hypochlorite ion concentration and hypobromite ion concentration were determined from measurement data when the absorption spectrum stabilized after the treatment solution was manufactured.

[0035] (Method for Determining Alkali Metal and Alkaline Earth Metal Concentrations) The concentrations of alkali metals and alkaline earth metals in the treatment solution were analyzed using high-frequency inductively coupled plasma atomic emission spectrometry (iCAP6500DuO, manufactured by Thermo SCIENTIFIC).

[0036] (Method for quantifying halide ion and halogen oxyacid ion concentrations) The concentrations of halide ions and halogen oxyacid ions were analyzed using an ion chromatography analyzer (DIONEX INTEGRATION 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 as the column. After removing background noise with a suppressor, the halide ions and halogen oxyacid ions in the treatment solution were quantified with an electrical conductivity detector.

[0037] (pH Measurement Method) The pH of 10 mL of the treatment solution prepared in the Examples and Comparative Examples was measured using a desktop pH meter (LAQUA F-73, manufactured by HORIBA, Ltd.) The pH measurement was carried out after the treatment solution was prepared and stabilized at 25°C.

[0038] (Evaluation) The etching rate of ruthenium, the etching rate of copper, and the galvanic corrosion of copper were evaluated using the produced treating solution by the methods described below. The results are shown in Table 2.

[0039] (Ruthenium Etching Rate) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a 1200 Å (±10%) ruthenium film was formed thereon using a sputtering method. The sheet resistance of the ruthenium was measured using a four-point probe resistance meter (Loresta-GP, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) and converted to film thickness, which was used as the ruthenium film thickness before the etching treatment. 40 mL of 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 predetermined temperature for 2 minutes to obtain the ruthenium film after the treatment. The thickness of the ruthenium film after the treatment was measured using the method described above, and the difference in film thickness before and after the treatment was divided by the treatment time to obtain the etching rate. The ruthenium etching rate was evaluated using the following evaluation criteria. Grades A to C were acceptable, and grade D was unacceptable. A: ≧100 Å / min B: 50 Å / min or more and less than 100 Å / min C: 10 Å / min or more and less than 50 Å / min D: < 10 Å / min

[0040] (Evaluation of Stability of Etching Rate of Ruthenium) 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 chemical solution at a predetermined temperature for 2 minutes, and the ruthenium film thickness was measured according to the method described above, and this was taken as the film thickness after the etching treatment. This was taken as the etching rate immediately after production of the treatment solution, and the etching rate was evaluated every week thereafter according to the method described above. The time during which the obtained etching rate was within ±20% of the etching rate immediately after production of the treatment solution was defined as the stability of the etching rate, and was evaluated according to the following criteria. Ratings A to C are acceptable levels, and rating D is unacceptable. 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

[0041] (Copper Etching Rate) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a copper film of 200 Å (±10%) was formed thereon using a sputtering method. 40 mL of the 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 200 Å copper film was immersed in the treatment solution at a predetermined temperature for 1 hour. The copper dissolved in the solution was analyzed using high-frequency inductively coupled plasma atomic emission spectroscopy (iCAP6500DuO, Thermo SCIENTIFIC). The amount of copper dissolved was calculated based on the copper density of 8.96 g / cm. ３ The thickness was converted into film thickness. The obtained film thickness was divided by the treatment time to obtain the copper etching rate. The copper corrosion was evaluated according to the following evaluation criteria. Evaluations A to B are acceptable levels, and evaluation C is unacceptable. A: <1 Å / min B: 1 Å / min to 10 Å / min C: >10 Å / min

[0042] (Ratio of ruthenium etching rate to copper etching rate) From the ruthenium etching rate and copper etching rate obtained by the above method, the ratio of the ruthenium etching rate to the copper etching rate (etching selectivity) was calculated. The etching selectivity was evaluated according to the following evaluation criteria. Evaluations A and B are acceptable levels, and evaluation C is unacceptable. A: 100 or more B: 50 or more and less than 100 C: Less than 50

[0043] (Evaluation of Copper Galvanic Corrosion) An oxide film was formed on a silicon wafer using a batch-type thermal oxidation furnace, and a ruthenium film of 1200 Å (±10%) and a copper film of 200 Å (±10%) were formed thereon using a sputtering method. The ruthenium film and copper film were cut into small pieces of a predetermined size. Using these as electrodes, a potentiostat (VersaSTAT 3F, manufactured by AMETEK) was used to measure the Tafel plot of each small piece in the treatment solution to determine the corrosion potential. The electrodes used for the potentiostat were each small piece as the working electrode, a Pt wire as the counter electrode, and a silver / silver chloride electrode as the reference electrode. The corrosion potential difference was calculated using the following formula: Corrosion potential difference = (Corrosion potential of copper) - (Corrosion potential of ruthenium)

[0044] Galvanic corrosion (corrosion potential difference) of copper was evaluated according to the following evaluation criteria. Evaluations A to B are acceptable levels, and evaluation C is unacceptable. A: >0 mV B: -100 to 0 mV C: <-100 mV

[0045] Examples 1 to 7 Treatment solutions were prepared as follows to have the compositions shown in Table 1. Sodium hypochlorite pentahydrate (tin dichloride 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 treatment solutions.

[0046] Example 8 A treatment solution was obtained in the same manner as in Example 1, except that 5% potassium hypochlorite (Shika Grade 1, manufactured by Kanto Chemical Co., Ltd.) was used instead of sodium hypochlorite and potassium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 10% aqueous sodium hydroxide solution, so as to have the composition shown in Table 1.

[0047] Example 9 A treatment solution having the composition shown in Table 1 was obtained in the same manner as in Example 1, except that calcium hypochlorite (manufactured by Sigma-Aldrich) was used instead of sodium hypochlorite, and calcium hydroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of the 10% aqueous sodium hydroxide solution.

[0048] Example 10 A treatment liquid was obtained in the same manner as in Example 1, except that sodium chloride (purity 99.999%, manufactured by Sigma-Aldrich) was further added so as to obtain the composition shown in Table 1.

[0049] Example 11 A treatment liquid was obtained in the same manner as in Example 10, except that sodium chlorate (special grade, content 99%, manufactured by Kishida Chemical Co., Ltd.) was further added so as to obtain the composition shown in Table 1.

[0050] Example 12 A treatment liquid was obtained in the same manner as in Example 10, except that sodium chlorite (content 80%, manufactured by Kishida Chemical Co., Ltd.) was further added so as to obtain the composition shown in Table 1.

[0051] Examples 13-16 As shown in FIG. 2 , one end of a 100 mL PFA trap bottle (manufactured by Fluorochemical Co., Ltd.) 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 (manufactured by Fluorochemical Co., Ltd.). 20 mL of bromine (purity >98%, manufactured by Tokyo Chemical Industry Co., Ltd.) was added to the 100 mL PFA trap bottle. It was confirmed that the tip of the PFA tube was not in contact with the liquid bromine. A 10% aqueous sodium hydroxide solution (special grade, manufactured by Kanto Chemical Co., Ltd.) and ultrapure water were added to the 500 mL PFA trap bottle to obtain a 0.34 mol / L aqueous sodium hydroxide solution. A stir bar was then placed in the 500 mL PFA trap bottle. A magnetic stirrer (AsOne, C-MAG HS10) was placed under the 500 mL PFA trap bottle and rotated and stirred at 300 rpm. Nitrogen was supplied to the 100 mL PFA trap bottle at a flow rate of 100 cc / min, and gasified bromine was supplied to the subsequent 500 mL PFA trap bottle for 300 minutes, yielding a 0.12 mol / L aqueous sodium hypobromite solution with a pH of 12.0. A 10% aqueous sodium hydroxide solution and ultrapure water were added to the obtained aqueous sodium hypobromite solution to obtain the treatment solution listed in Table 1.

[0052] Example 17 A treatment solution was obtained in the same manner as in Example 13, except that sodium bromate (content >99.5%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added so as to obtain the composition shown in Table 1.

[0053] Example 18 Sodium hypochlorite pentahydrate, a 0.12 mol / L aqueous solution of sodium hypobromite prepared in the same manner as in Example 13, ultrapure water, and a 10% aqueous solution of sodium hydroxide were mixed to obtain a treatment liquid described in Table 1.

[0054] Examples 19 and 20 Potassium hexacyanidoferrate(III) (purity >99.0%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), ultrapure water, and potassium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed so as to obtain a treatment solution with the composition shown in Table 1.

[0055] Example 21 Potassium permanganate (purity >99.3%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), ultrapure water, and potassium hydroxide (manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed to obtain a treatment solution having the composition shown in Table 1.

[0056] 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 glass three-neck flask (manufactured by Cosmos Bead Co., Ltd.) to obtain a 0.63 mol / L aqueous solution of tetramethylammonium hydroxide. Next, a rotor (manufactured by AsOne Co., Ltd., total length 30 mm x diameter 8 mm) was placed in the three-neck flask, a thermometer protection tube (manufactured by Cosmos Bead Co., Ltd., bottom-sealed type) and a thermometer were inserted into one opening, and a chlorine gas cylinder and a nitrogen gas cylinder were connected to the other opening. The tip of a PFA tube (manufactured by Flon Industries Co., Ltd., F-8011-02) was immersed in the bottom of the solution in a state where the chlorine gas / nitrogen gas could be switched between optionally, and the remaining opening was connected to a gas washing bottle (manufactured by AsOne Co., Ltd., gas washing bottle, model number 2450 / 500) filled with a 5% by mass aqueous solution of sodium hydroxide. Thereafter, a magnetic stirrer (AsOne Corporation, C-MAG HS10) was placed at the bottom of the three-neck flask and rotated at 300 rpm to stir the contents. While the outer periphery of the three-neck flask was cooled with ice water, chlorine gas (purity 99.999 or higher, manufactured by ADEKA Corporation) was supplied at a flow rate of 38 cc / min. The concentration of the resulting aqueous tetramethylammonium hypochlorite solution was 0.31 mol / L, and the pH was 12.0. The resulting aqueous tetramethylammonium hypochlorite solution, ultrapure water, and 10% aqueous sodium hydroxide solution were added to obtain the treatment solution shown in Table 1.

[0057] Comparative Example 2 A treatment liquid was obtained by mixing orthoperiodic acid (content >98.5%, Fujifilm Wako Pure Chemical Industries, Ltd.), ultrapure water, and a 25% aqueous solution of tetramethylammonium hydroxide so as to obtain the composition shown in Table 1.

[0058] Comparative Example 3 A treatment liquid was obtained by mixing hydrogen peroxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), ultrapure water, and a 25% aqueous solution of tetramethylammonium hydroxide so as to obtain the composition shown in Table 1.

[0059]

[0060] REFERENCE SIGNS LIST 11 Substrate 12 Resist 13 Seed layer 14 Metal layer 15 Flow meter 16 100 mL PFA trap bottle 17 500 mL PFA trap bottle 18 Rotor 19 PFA tube 20 Ice water 21 Three-neck flask 22 Thermometer protection tube 23 Thermocouple 24 Rotor 25 PFA tube 26 Trap bottle 27 5 mass % sodium hydroxide aqueous solution 28 Flow meter 29 Water bath

Claims

1. A semiconductor substrate treatment solution for removing high-melting point metals from semiconductor substrates containing such metals, the treatment solution containing one or more metals selected from alkali metals and alkaline earth metals, and an oxidizing agent, the oxidizing agent being one or more selected from the group consisting of hypohalite ions, metal complexes, and salts thereof, and having a pH of 7 or more and 14 or less at 25°C.

2. The semiconductor substrate treatment solution according to claim 1, wherein the semiconductor substrate further contains copper, and the high-melting point metal is one or more selected from the group consisting of titanium, tantalum, ruthenium, molybdenum, tungsten, chromium, iridium, rhodium, platinum, and niobium, and the solution is used to selectively remove the high-melting point metal relative to the copper.

3. A processing solution for semiconductor substrates according to claim 1 or 2, wherein the processing solution for semiconductor substrates is an etching solution, the semiconductor substrate contains a high-melting point metal and copper, and when the semiconductor substrate is processed using the etching solution, the ratio of the etching rate of the high-melting point metal to the etching rate of the copper is 50 or more.

4. The semiconductor substrate treating solution according to claim 1 or 2, wherein the alkali metal is at least one selected from the group consisting of sodium and potassium.

5. The semiconductor substrate treating solution according to claim 1 or 2, wherein the alkaline earth metal is at least one selected from the group consisting of magnesium and calcium.

6. The treating solution for semiconductor substrates according to claim 1 or 2, further containing halogen oxyacid ions.

7. A method for treating a semiconductor substrate containing a high-melting point metal and copper, comprising the step of selectively removing the high-melting point metal relative to the copper contained in the semiconductor substrate using a treatment solution for semiconductor substrates according to any one of claims 1 to 6.

8. A method for manufacturing a semiconductor substrate containing a high-melting point metal and copper, comprising the step of selectively removing the high-melting point metal relative to the copper contained in the semiconductor substrate using the semiconductor substrate treatment solution according to any one of claims 1 to 6.

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