Method for removing metal compound

Abstract

Provided is a method for removing a metal compound, whereby it is possible to selectively remove an oxide of a metal, a nitride of a metal and an oxynitride of a metal while preventing the removal of silicon dioxide, silicon nitride, a polysilicon, an element metal or the like. At least one metal compound selected from an oxide of a metal, a nitride of a metal and an oxynitride of a metal is removed from a material of interest by bringing the at least one metal compound into contact with a treatment solution. The metal comprises at least one metal selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper and molybdenum. The treatment solution is an aqueous solution containing one or more compounds for removal use each of which is selected from a carboxylic acid and a salt thereof, wherein the total concentration of all of the compounds for removal use in the treatment solution is 2% by mass or more.

Description

Technical Field

[0001] The present invention relates to a method for removing metal compounds.

Background Art

[0002] In electronic devices such as liquid crystal displays and semiconductor elements, metals such as tungsten (W), cobalt (Co), nickel (Ni), tantalum (Ta), titanium (Ti), iron (Fe), copper (Cu), and molybdenum (Mo) may be used as wiring materials, channel materials, gate materials, barrier metals, etc.

[0003] In the process of forming wiring or the like in an electronic device using the above metals, various contaminations may occur. These contaminations can contribute to deteriorating the characteristics of the electronic device, for example, by causing leakage current. Examples of contamination include, for example, when contaminants such as metal oxides, metal nitrides, and metal oxynitrides are formed in the film formation process of a nitride film or an oxide film during the manufacture of an electronic device, or when air enters the chamber used during the manufacture of an electronic device and oxygen, nitrogen react with the metal film to form contaminants such as metal oxides, metal nitrides, and metal oxynitrides.

[0004] For the above reasons, a cleaning process using a treatment liquid is performed to remove contaminants such as metal oxides on the electronic device. In a semiconductor manufacturing process for manufacturing a semiconductor using silicon as a substrate, as a treatment liquid for removing the above contaminants, for example, a solution containing a fluorine compound or a fluoride ion-containing compound, a mixed solution of hydrogen peroxide water and ammonia water (see, for example, Patent Document 1), and a mixed solution obtained by adding a chelating agent to an aqueous carboxylic acid solution (see, for example, Patent Document 2) are used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, treatment liquids containing fluorine compounds or fluoride ion-containing compounds have a problem in that they also remove silicon substrates, silicon dioxide films, etc. at the same time because they contain fluorine. In addition, the treatment liquid disclosed in Patent Document 1 has a problem in that it also removes metal elements such as tungsten and titanium at the same time because it contains an oxidizing agent. Also, Patent Document 2 discloses that contaminant metals such as iron can be removed with an aqueous oxalic acid solution having a concentration of 1%, but a method for selectively removing metal oxides, metal nitrides, or metal oxynitrides with respect to metal elements, etc. is not disclosed.

[0007] An object of the present invention is to provide a method for removing metal compounds capable of selectively removing metal oxides, metal nitrides, and metal oxynitrides while suppressing the removal of silicon dioxide, silicon nitride, polysilicon, metal elements, etc. [Means for Solving the Problems]

[0008] To solve the above problems, one aspect of the present invention is as follows in [1] to

[16] . [1] A method for removing metal compounds comprising a removal step of removing at least one metal compound selected from metal oxides, metal nitrides, and metal oxynitrides from an object to be treated by bringing it into contact with a treatment liquid, wherein the metal is at least one selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper, and molybdenum, and the treatment liquid is an aqueous solution containing at least one removal compound selected from carboxylic acids and their salts, A method for removing a metal compound, wherein the total concentration of the removing compound in the treatment liquid is 2% by mass or more.

[0009] [2] The method for removing a metal compound according to [1], wherein the total concentration of the removing compound in the treatment liquid is 3% by mass or more and 70% by mass or less. [3] The method for removing a metal compound according to [1], wherein the total concentration of the removing compound in the treatment liquid is 5% by mass or more and 50% by mass or less. [4] The method for removing a metal compound according to any one of [1] to [3], wherein the carboxylic acid is a polyvalent carboxylic acid.

[0010] [5] The method for removing a metal compound according to any one of [1] to [3], wherein the carboxylic acid is an α-hydroxycarboxylic acid. [6] The method for removing a metal compound according to any one of [1] to [3], wherein the carboxylic acid is an α-amino acid. [7] The method for removing a metal compound according to any one of [1] to [3], wherein the carboxylic acid is at least one selected from citric acid, tartaric acid, succinic acid, malic acid, glutaric acid, lactic acid, and glycine.

[0011] [8] The method for removing a metal compound according to any one of [1] to [7], wherein the removing compound contains at least one selected from the ammonium salt of the carboxylic acid, the sodium salt of the carboxylic acid, and the potassium salt of the carboxylic acid. [9] The method for removing a metal compound according to any one of [1] to [8], wherein the pH of the treatment liquid at 25 °C is 1 or more and 9 or less.

[10] The method for removing a metal compound according to any one of [1] to [9], wherein the temperature of the treatment liquid is 0 °C or more and 100 °C or less.

[0012]

[11] The method for removing a metal compound according to any one of [1] to

[10] , wherein the contact time between the metal compound and the treatment liquid is 1 second or more and 60 minutes or less.

[12] The ratio of the removal rate of the metal compound to be removed to the removal rate of the object not to be removed is 10 or more, and the object not to be removed is at least one selected from silicon dioxide, silicon nitride, polysilicon, tungsten alone, cobalt alone, nickel alone, tantalum alone, titanium alone, iron alone, copper alone, and molybdenum alone. The method for removing a metal compound according to any one of [1] to

[11] .

[0013]

[13] The method for removing a metal compound according to any one of [1] to

[12] , wherein the metal compound is a contaminant in an electronic device.

[14] The method for removing a metal compound according to any one of [1] to

[13] , wherein the concentration of fluoride ions in the treatment liquid is 1% by mass or less.

[15] The method for removing a metal compound according to any one of [1] to

[14] , wherein the concentration of the oxidizing agent in the treatment liquid is 1% by mass or less.

[16] The method for removing a metal compound according to

[15] , wherein the oxidizing agent is hydrogen peroxide. [Advantages of the Invention]

[0014] According to the present invention, it is possible to selectively remove metal oxides, metal nitrides, and metal oxynitrides while suppressing the removal of silicon dioxide, silicon nitride, polysilicon, elemental metals, etc. [Embodiments for Carrying Out the Invention]

[0015] One embodiment of the present invention will be described below. Note that this embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. Also, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

[0016] As a result of various studies by the present inventors, it has been found that the above problems can be solved by treating with a treatment liquid having a specific configuration, and the present invention has been completed. That is, a method for removing a metal compound according to an embodiment of the present invention includes a removal step of removing at least one metal compound selected from metal oxides, metal nitrides, and metal oxynitrides from an object to be treated by bringing it into contact with a treatment liquid. And the above metal is at least one selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper, and molybdenum. Further, the treatment liquid is an aqueous solution containing at least one removal compound selected from carboxylic acids and their salts, and the total concentration of the removal compounds in the treatment liquid is 2% by mass or more.

[0017] Since carboxylic acids and their salts have a chelating action on the above-mentioned metal oxides, nitrides, and oxynitrides, when treated with the above-mentioned treatment liquid, removal of silicon dioxide, silicon nitride, polysilicon, elemental metal, etc. can be suppressed while selectively removing the metal oxides, nitrides, and oxynitrides of the above-mentioned metal.

[0018] For example, when forming a metal film (a film of elemental metal) on a substrate during the manufacture of electronic devices such as liquid crystal displays and semiconductor elements, contaminants such as oxides of the metal, nitrides of the metal, and oxynitrides of the metal may adhere to the substrate due to the reaction of the mixed oxygen and nitrogen with the metal film. When the method for removing a metal compound according to this embodiment is applied to a substrate with contaminants adhering thereto, the removal compound in the treatment liquid forms a complex with the metal oxide, metal nitride, and metal oxynitride by a chelating action, so that the contaminants adhering to the substrate can be removed.

[0019] On the other hand, the metal element that constitutes the metal film takes a long time to form a chelate with the removing compound compared to the metal oxide, metal nitride, and metal oxynitride, so the metal film is hardly removed even when it is contacted with the treatment liquid. The same is true when a silicon dioxide film, silicon nitride film, or polysilicon film is formed on the substrate, and the silicon dioxide film, silicon nitride film, and polysilicon film are hardly removed.

[0020] Metal oxides, metal nitrides, and metal oxynitrides refer to compounds consisting of a metal and an oxygen atom (O), compounds consisting of a metal and a nitrogen atom (N), and compounds consisting of a metal, an oxygen atom, and a nitrogen atom, respectively. The form of the metal oxides, metal nitrides, and metal oxynitrides is not particularly limited, and may be, for example, in the form of a film, foil, powder, particle, or lump.

[0021] The ratio of the metal to the oxygen atom or nitrogen atom in the metal compound is not particularly limited. For example, the metal oxide may be x O y (M is at least one metal selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper, and molybdenum, x is an integer of 1 to 5, and y is an integer of 1 to 10). 2 O 3 , M.O. 2 , M.O. 3 , M 3 O 4 , M 2 O 5 Examples of the compound include compounds represented by the following formula:

[0022] Metal nitrides include, for example, M a N b (M is at least one metal selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper, and molybdenum, a is an integer of 1 to 20, and b is an integer of 1 to 30.) 2 N, M 3 N 2 , M 3 N 4 , M4 N, M 7 N 3 , M 16 N 2 Examples of the compound represented by the formula include those represented by the following formulae.

[0023] The metal oxynitride is, for example, a compound represented by M c N d O e (where M is at least one metal selected from tungsten, cobalt, nickel, tantalum, titanium, iron, copper, and molybdenum, and c, d, and e are each independently an integer of 1 or more). It is a compound containing preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more of the metal.

[0024] The total concentration of the removal compound in the treatment liquid is 2% by mass or more, preferably 3% by mass or more and 70% by mass or less, and more preferably 5% by mass or more and 50% by mass or less. If the total concentration of the removal compound in the treatment liquid is within the above numerical range, the removal rate of the above metal compound to be removed is high and more practical. Since an aqueous solution of the removal compound is used as the treatment liquid, the solubility of the removal compound in water (g / 100g-H 2 O) is preferably high, preferably 2 or more.

[0025] The type of the removal compound is not particularly limited as long as it is a carboxylic acid or its salt capable of forming a chelate complex with the above metal oxide, the above metal nitride, and the above metal oxynitride, but it is preferably a polyvalent carboxylic acid, an α-hydroxycarboxylic acid, an α-amino acid, or a salt thereof.

[0026] A polyvalent carboxylic acid is a carboxylic acid having a plurality of carboxy groups in the molecule, and from the viewpoint of the strength of the chelating action, the number of carboxy groups is more preferably 2 or 3. Specific examples of the polyvalent carboxylic acid include citric acid, tartaric acid, malic acid, succinic acid, maleic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, D-glucaric acid, itaconic acid, citraconic acid, mesaconic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, acetylenedicarboxylic acid, 1,1-cyclopropanedicarboxylic acid, trimellitic acid, endothal, glutamic acid, methylsuccinic acid, citramalic acid, phthalic acid.

[0027] An α-hydroxycarboxylic acid is a carboxylic acid having a hydroxy group on the carbon atom adjacent to the carboxy group. Specific examples of the α-hydroxycarboxylic acid include lactic acid, glycolic acid, tartronic acid, quinic acid. An α-amino acid is a carboxylic acid having an amino group on the carbon atom adjacent to the carboxy group. Specific examples of the α-amino acid include glycine, alanine, arginine, asparagine, aspartic acid, glutamine, glutamic acid, valine, leucine, isoleucine, cysteine, histidine, lysine, serine, threonine, tryptophan, phenylalanine, proline, tyrosine, lysine.

[0028] Among these carboxylic acids, citric acid, tartaric acid, malonic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, glutaric acid, endothal, glycolic acid, malic acid, oxalic acid, phthalic acid, lactic acid, glycine, alanine are more preferable, and citric acid, tartaric acid, succinic acid, malic acid, glutaric acid, lactic acid, glycine are even more preferable, in view of ease of handling and high metal compound removal effect.

[0029] When using a carboxylate as the removal compound, the type of salt is not particularly limited. For example, ammonium salts, alkylammonium salts, arylammonium salts, lithium salts, sodium salts, potassium salts, cesium salts, calcium salts, and magnesium salts can be mentioned. From the viewpoints of high safety, ease of handling, and economy, ammonium salts, alkylammonium salts, lithium salts, sodium salts, potassium salts, and cesium salts are more preferred, and ammonium salts, sodium salts, and potassium salts are even more preferred. If a carboxylic acid, a base, and water are mixed to form an aqueous solution, an aqueous solution of the carboxylate can be obtained.

[0030] The carboxylic acid may be used alone or in combination of two or more. Also, only the carboxylic acid may be used as the removal compound, only the carboxylate may be used, or the carboxylic acid and its salt may be used in combination. Furthermore, the types of carboxylates may be used alone or in combination of two or more.

[0031] In addition, the treatment liquid may contain components other than the carboxylic acid and its salt. For example, it may contain a wetting agent, a surfactant, a coloring agent, an antifoaming agent, etc. However, it is preferable that the treatment liquid does not contain an oxidizing agent such as hydrogen peroxide and fluoride ions, and the concentrations of the oxidizing agent and fluoride ions in the treatment liquid are each preferably 1% by mass or less. If the treatment liquid contains an oxidizing agent or fluoride ions, there is a possibility that elemental metals, silicon dioxide, polysilicon, etc. will also be removed together with the metal compound.

[0032] In the method for removing a metal compound according to this embodiment, the method of bringing the treatment liquid into contact with the metal compound is not particularly limited. For example, methods such as dipping, spraying, coating, and pouring can be mentioned. However, from the viewpoint of simplifying the apparatus used for bringing the treatment liquid into contact with the metal compound, the dipping method is preferred.

[0033] The treatment conditions in the immersion method vary depending on the type of metal and the composition of the treatment solution. For example, the pH of the treatment solution at 25°C is preferably 1 or more and 9 or less, and more preferably 7 or more and 9 or less. The pH of the treatment solution at 25°C can be adjusted by adding a basic aqueous solution such as aqueous ammonia.

[0034] Also, the temperature of the treatment solution is preferably 0°C or more and 100°C or less, more preferably 5°C or more and 90°C or less, and even more preferably 10°C or more and 80°C or less. Furthermore, the contact time (treatment time) between the metal compound and the treatment solution is preferably 0.1 second or more and 180 minutes or less, more preferably 0.5 second or more and 90 minutes or less, and even more preferably 1 second or more and 60 minutes or less. In addition, such immersion treatment may be performed by simply immersing an object to be treated (e.g., a substrate) having the above metal compound, which is the object to be removed, in the treatment solution, or by immersing it in a treatment solution with ultrasonic waves applied or being stirred.

[0035] If the object to be treated on which the treatment for removing the metal compound has been performed is washed with a cleaning solution such as water, the removal compound and contaminants remaining on the surface of the object to be treated can be removed from the object to be treated. The type of the cleaning solution is not particularly limited, but it is possible to wash only with water such as pure water, and there is no need to use an organic solvent such as alcohol. Since there is no need to use an organic solvent in the treatment solution or the cleaning solution, the method for removing the metal compound according to this embodiment is less likely to have an adverse effect on the human body and the environment.

[0036] The type of workpiece to which the method for removing metal compounds according to the present embodiment can be applied is not particularly limited as long as it has a metal compound as a removal target and a non-removal target as described below, and examples thereof include electronic devices. Specific examples of electronic devices include liquid crystal displays, semiconductor elements, MEMS (Micro Electro Mechanical Systems) elements, and hard disks. According to the method for removing metal compounds according to the present embodiment, silicon dioxide, silicon nitride, polysilicon, and elemental metals as non-removal targets are hardly removed, so that the metal compounds, which are contaminants in electronic devices, can be removed with little adverse effect on the workpiece such as electronic devices.

[0037] In the method for removing a metal compound according to this embodiment, the ratio of the removal rate of the metal compound, which is the object to be removed, to the removal rate of a non-object that is not the object to be removed is preferably at least 10. Here, the non-object to be removed is at least one selected from silicon dioxide, silicon nitride, polysilicon, elemental tungsten, elemental cobalt, elemental nickel, elemental tantalum, elemental titanium, elemental iron, elemental copper, and elemental molybdenum.

[0038] If the object to be removed is in the form of a film or foil, its thickness is preferably 10 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more, and if it is in the form of a lump, its minor axis is preferably 10 nm or more, more preferably 50 nm or more, and even more preferably 100 nm or more. If the object to be removed is too small, it may be removed by the treatment liquid.

[0039] These non-removal targets are, for example, materials constituting electronic devices, and are used in electronic devices as wiring materials, channel materials, gate materials, barrier metals, etc. If the removal rate ratio is 10 or more, it is possible to selectively remove the metal compounds, which are contaminants in electronic devices, while suppressing the removal of non-removal targets such as silicon dioxide, silicon nitride, polysilicon, and simple metals. EXAMPLES

[0040] Examples, comparative examples, and reference examples are shown below to explain the present invention in more detail. [Example 1] A 100 mL polypropylene container containing 40 mL of a treatment liquid (an aqueous solution of ammonium citrate with a concentration of 5% by mass (pH 7.6 at 25°C)) was heated in a water bath to set the temperature of the treatment liquid at 25°C. Into this treatment liquid, a silicon substrate (manufactured by C. S. T. World Co., Ltd.) on which a tungsten oxide (WO 3 ) film with a thickness of 600 nm was formed was immersed for 5 minutes, allowed to stand, and a removal step was performed. The shape of this silicon substrate was a square with a side length of 2 cm, but only half of it, that is, only the rectangular portion with a length of 1 cm × width of 2 cm, was immersed in the treatment liquid.

[0041] The silicon substrate was taken out from the treatment liquid, and the entire silicon substrate including the portion immersed in the treatment liquid was washed with pure water. Then, the film thickness difference between the tungsten oxide film on the portion immersed in the treatment liquid and the tungsten oxide film on the non-immersed portion was measured, and by dividing the film thickness difference by the immersion time (treatment time), the removal rate of the tungsten oxide film on the portion immersed in the treatment liquid was calculated. The measurement of the film thickness difference of the tungsten oxide film was performed using an atomic force microscope. The measurement conditions are as follows. Also, the measurement results are shown in Table 1.

[0042] Atomic force microscope: VN-8010 manufactured by Keyence Corporation Measurement temperature: 28°C Measurement pressure: 101.3 kPa Measurement atmosphere: Air Scanning range: Width 80.0 μm, height 20.0 μm, angle 0°C

[0043] [Table 1]

[0044] [Example 2] The removal process was carried out in the same manner as in Example 1 except that the temperature of the treatment liquid was set to 90°C, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 3] The removal process was carried out in the same manner as in Example 1 except that the temperature of the treatment liquid was set to 0°C, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1.

[0045] [Example 4] The removal process was carried out in the same manner as in Example 1 except that the concentration of ammonium citrate in the treatment liquid was set to 50% by mass, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 5] The removal process was carried out in the same manner as in Example 1 except that an aqueous solution (pH 8.5 at 25°C) obtained by mixing a 5% by mass aqueous solution of citric acid and a 2% by mass aqueous solution of ammonia in a mass ratio of 1:1 was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. At this time, the treatment liquid is an aqueous solution of 2.5% by mass of citric acid and 1% by mass of ammonia. The results are shown in Table 1.

[0046] [Example 6] The removal process was carried out in the same manner as in Example 1 except that an aqueous solution (pH 6.5 at 25°C) obtained by mixing a 5% by mass aqueous solution of citric acid and a 2% by mass aqueous solution of ammonia in a mass ratio of 2:1 was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. At this time, the treatment liquid is an aqueous solution of 3.33% by mass of citric acid and 0.67% by mass of ammonia. The results are shown in Table 1.

[0047] [Example 7] The removal process was carried out in the same manner as in Example 1 except that an aqueous solution (pH 4.0 at 25°C) obtained by mixing a 5% by mass aqueous solution of citric acid and a 2% by mass aqueous solution of ammonia in a mass ratio of 5:1 was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. At this time, the treatment liquid is an aqueous solution of 4.17% by mass of citric acid and 0.33% by mass of ammonia. The results are shown in Table 1.

[0048] [Example 8] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of trisodium citrate with a concentration of 5% by mass (pH 7.6 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 9] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of tripotassium citrate with a concentration of 5% by mass (pH 7.6 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1.

[0049] [Example 10] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of diammonium DL-tartrate with a concentration of 5% by mass (pH 7.9 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 11] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of diammonium succinate with a concentration of 5% by mass (pH 8.0 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1.

[0050] [Example 12] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of diammonium malate with a concentration of 5% by mass (pH 8.0 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 13] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of diammonium glutarate with a concentration of 5% by mass (pH 8.0 at 25°C) was used as the treatment liquid, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1.

[0051] [Example 14] A removal step was performed in the same manner as in Example 1 except that an aqueous solution of glycine with a concentration of 5% by mass (pH 8.0 at 25°C) was used as the treatment liquid and the temperature of the treatment liquid was set to 60°C, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1. [Example 15] A removal step was performed in the same manner as in Example 1, except that an aqueous citric acid solution having a concentration of 5% by mass (pH 2.0 at 25°C) was used as the treatment liquid and the temperature of the treatment liquid was 60°C, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 1.

[0052] [Example 16] A removal step was performed in the same manner as in Example 1, except that the film type formed on the silicon substrate was a cobalt oxide (CoO) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the cobalt oxide film was calculated. The results are shown in Table 1. [Example 17] A removal step was performed in the same manner as in Example 1, except that the film type formed on the silicon substrate was a nickel oxide (NiO) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the nickel oxide film was calculated. The results are shown in Table 1.

[0053] [Example 18] A removal step was performed in the same manner as in Example 1, except that the film type formed on the silicon substrate was a molybdenum oxide (MoO 3 ) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the molybdenum oxide film was calculated. The results are shown in Table 1. [Example 19] A removal step was performed in the same manner as in Example 1, except that the film type formed on the silicon substrate was a titanium oxide (TiO 2 ) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the titanium oxide film was calculated. The results are shown in Table 1.

[0054] [Example 20] A removal step was performed in the same manner as in Example 1, except that the film type formed on the silicon substrate was an iron oxide (Fe 2 O 3 ) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the iron oxide film was calculated. The results are shown in Table 1. [Example 21] The removal process was carried out in the same manner as in Example 1, except that the type of film formed on the silicon substrate was a copper oxide (CuO) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), and the removal rate of the copper oxide film was calculated. The results are shown in Table 1.

[0055] [Example 22] The removal process was carried out in the same manner as in Example 1, except that the type of film formed on the silicon substrate was a tantalum oxide (Ta 2 O 5 ) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm) and the temperature of the treatment liquid was 60°C, and the removal rate of the tantalum oxide film was calculated. The results are shown in Table 1. [Example 23] The removal process was carried out in the same manner as in Example 1, except that the type of film formed on the silicon substrate was a tantalum oxide film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm), an aqueous ammonium lactate solution with a concentration of 5% by mass (pH 7.8 at 25°C) was used as the treatment liquid, and the temperature of the treatment liquid was 40°C, and the removal rate of the tantalum oxide film was calculated. The results are shown in Table 1.

[0056] [Example 24] The removal process was carried out in the same manner as in Example 1, except that the type of film formed on the silicon substrate was a tungsten nitride (WN 2 ) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm) and the temperature of the treatment liquid was 60°C, and the removal rate of the tungsten nitride film was calculated. The results are shown in Table 1. [Example 25] The removal process was carried out in the same manner as in Example 1, except that the type of film formed on the silicon substrate was a tungsten oxynitride (WON) film (manufactured by C.S.T. World Co., Ltd., film thickness 600 nm) and the temperature of the treatment liquid was 60°C, and the removal rate of the tungsten oxynitride film was calculated. The results are shown in Table 1.

[0057] [Example 26] A silicon substrate (manufactured by C. S. T. World Co., Ltd.) with a tungsten oxide film having a thickness of 600 nm and a silicon substrate (manufactured by C. S. T. World Co., Ltd.) with a tungsten film having a thickness of 100 nm were simultaneously immersed in a treatment liquid, and the removal rates of the tungsten oxide film and the tungsten film were calculated respectively. A test similar to Example 1 was conducted except for this. The results are shown in Table 2.

[0058] In Table 2, although it is indicated as "less than 30 / 0.1" in the column of "removal rate", it means that the removal rate of the tungsten oxide film is 30 nm / min and the removal rate of the tungsten film is less than 0.1 nm / min. That is, the removal rates corresponding to the two types of films described in the column of "film type" in Table 2 are shown. The same applies to Examples 27 and 28 and Comparative Examples 2 and 3 described later. In Table 2, the "removal rate ratio" indicates the ratio of the removal rates corresponding to the above two types of films, that is, (removal rate of the film described on the left) / (removal rate of the film described on the right).

[0059] [Example 27] A removal step was performed in the same manner as in Example 26 except that an aqueous solution (pH 7.6 at 25°C) obtained by mixing an aqueous solution of ammonium citrate tribasic with a concentration of 5% by mass and an aqueous solution of hydrogen peroxide with a concentration of 1% by mass at a mass ratio of 1:1 was used as the treatment liquid, and the removal rates of the tungsten oxide film and the tungsten film were calculated respectively. At this time, the treatment liquid is an aqueous solution of 2.5% by mass of ammonium citrate tribasic and 0.5% by mass of hydrogen peroxide. The results are shown in Table 2.

[0060] [Example 28] An aqueous solution (pH 7.6 at 25°C) obtained by mixing an aqueous solution of ammonium citrate tribasic with a concentration of 5% by mass and an aqueous solution of hydrogen fluoride with a concentration of 1% by mass at a mass ratio of 1:1 was used as the treatment liquid, and a silicon substrate (manufactured by C. S. T. World Co., Ltd.) with a tungsten oxide film having a thickness of 600 nm and silicon dioxide (SiO 2A silicon substrate (manufactured by CST World Co., Ltd.) on which a film was formed was immersed in the treatment liquid at the same time, and the same test as in Example 1 was conducted except that the removal rates of the tungsten oxide film and the silicon dioxide film were calculated respectively. At this time, the treatment liquid is an aqueous solution of 2.5% by mass of ammonium citrate and 0.5% by mass of hydrogen peroxide. The results are shown in Table 2.

[0061]

Table 2

[0062] 〔Reference Example 1〕 A removal step was performed in the same manner as in Example 1 except that the type of film formed on the silicon substrate was a silicon dioxide film (manufactured by CST World Co., Ltd., film thickness 100 nm) and the treatment time was 180 minutes, and the removal rate of the silicon dioxide film was calculated. The results are shown in Table 2. 〔Reference Examples 2 to 10〕 A removal step was performed in the same manner as in Reference Example 1 except that the type of film formed on the silicon substrate was the film described in Table 2 (all manufactured by CST World Co., Ltd., and each film had a thickness of 100 nm), and the removal rates of the films described in Table 2 were calculated. The results are shown in Table 2.

[0063] 〔Comparative Example 1〕 A removal step was performed in the same manner as in Example 1 except that the concentration of ammonium citrate in the treatment liquid was 1% by mass, and the removal rate of the tungsten oxide film was calculated. The results are shown in Table 2. 〔Comparative Example 2〕 A removal step was performed in the same manner as in Example 26 except that an aqueous solution (pH 14.0 at 25 °C) obtained by mixing aqueous ammonia with a concentration of 5% by mass and aqueous hydrogen peroxide with a concentration of 5% by mass in a mass ratio of 2:8 was used as the treatment liquid, and the removal rates of the tungsten oxide film and the tungsten film were calculated respectively. At this time, the treatment liquid is an aqueous solution of 1% by mass of ammonia and 4% by mass of hydrogen peroxide. The results are shown in Table 2.

[0064] 〔Comparative Example 3〕 An aqueous solution (pH 14.0 at 25°C) obtained by mixing an aqueous citric acid solution with a concentration of 5% by mass and aqueous ammonia with a concentration of 5% by mass at a mass ratio of 1:9 was used as the treatment liquid. A silicon substrate (manufactured by C.S.T. World Co., Ltd.) with a tungsten oxide film having a thickness of 600 nm and a silicon substrate (manufactured by C.S.T. World Co., Ltd.) with a polysilicon film having a thickness of 100 nm were simultaneously immersed in the treatment liquid, and the removal rates of the tungsten oxide film and the polysilicon film were calculated respectively. A test similar to Example 1 was conducted except for this. At this time, the treatment liquid is an aqueous solution of 0.5% by mass of citric acid and 4.5% by mass of ammonia. The results are shown in Table 2.

[0065] As can be seen from the results of Examples 1 to 4, by using an aqueous ammonium citrate solution as the treatment liquid, tungsten oxide can be removed at a practical rate. Also, the higher the temperature of the treatment liquid, the faster the removal rate, and the higher the concentration of ammonium citrate in the treatment liquid, the faster the removal rate.

[0066] As can be seen from the results of Example 1 and Examples 5 to 7, the higher the pH of the treatment liquid at 25°C, the more the removal rate is improved. The reason for this is considered that the protonation of citrate ions is suppressed by keeping the pH of the treatment liquid high at 25°C, and the concentration of the chelate species has increased.

[0067] As can be seen from the results of Examples 8 to 15, even when trisodium citrate, tripotassium citrate, ammonium DL-tartrate, diammonium succinate, diammonium malate, diammonium glutarate, glycine, and citric acid are used as the removal compound, the removal of tungsten oxide proceeds without problems.

[0068] As can be seen from the results of Examples 16 to 25, by using ammonium citrate and ammonium lactate as the removal compounds, various metal oxides, metal nitrides, and metal oxynitrides can be removed. In particular, for tantalum oxide, the removal proceeded more rapidly when ammonium lactate was used than when ammonium citrate was used as the removal compound. From this, it can be understood that it is effective to change the type of carboxylic acid used in the treatment liquid depending on the metal species of the metal compound to be removed.

[0069] As can be seen from the results of Example 26, when tungsten oxide and tungsten metal were treated simultaneously in an aqueous ammonium citrate solution, tungsten oxide was selectively removed. As can be seen from the results of Example 27, when tungsten oxide and tungsten metal were treated simultaneously in an aqueous ammonium citrate solution containing a small amount of hydrogen peroxide, although a small amount of tungsten metal was removed, tungsten oxide was selectively removed.

[0070] As can be seen from the results of Example 28, when tungsten oxide and silicon dioxide were treated simultaneously in an aqueous ammonium citrate solution containing a small amount of fluoride ions, although a small amount of silicon dioxide was removed, tungsten oxide was selectively removed. As can be seen from the results of Reference Examples 1 to 10, under the condition of using an aqueous ammonium citrate solution with a concentration of 5% by mass, silicon-based materials and metal metals were hardly removed.

[0071] As can be seen from the results of Comparative Example 1, under the condition of using an aqueous ammonium citrate solution with a concentration of 1% by mass as the treatment liquid, although tungsten oxide could be removed, the removal rate was slow. From this, it can be understood that the concentration of carboxylic acid in the treatment liquid in the present invention significantly affects the removal effect of metal compounds.

[0072] As can be seen from the results of Comparative Example 2 and Comparative Example 3, under the conditions where a mixed solution of aqueous ammonia and aqueous hydrogen peroxide, or a mixed solution of aqueous citric acid and aqueous ammonia (where the concentration of citric acid is less than 2% by mass) is used as the treatment liquid, tungsten oxide can be removed, but the removal of elemental tungsten and polysilicon proceeds simultaneously, resulting in a decrease in selectivity.

Claims

1. A method for removing a metal compound, comprising a removal step of removing at least one metal compound selected from metal oxides, metal nitrides, and metal oxynitrides from an object to be treated by bringing it into contact with a treatment liquid, wherein the metal is at least one selected from tungsten, cobalt, nickel, tantalum, titanium, iron, and molybdenum (however, when the metal is tungsten, the metal compound is a compound other than tungsten oxide), the treatment liquid is an aqueous solution containing at least one removal compound selected from carboxylic acids and their salts, the carboxylic acid is at least one selected from citric acid, tartaric acid, malic acid, glutaric acid, lactic acid, and glycine, the total concentration of the removal compound in the treatment liquid is 2% by mass or more, the concentration of fluoride ions in the treatment liquid is 0.475% by mass or less, the metal compound is a contaminant in an electronic device and the object to be treated is a substrate. A method for removing a metal compound.

2. The method for removing a metal compound according to claim 1, wherein the total concentration of the removal compound in the treatment liquid is 3% by mass or more and 70% by mass or less.

3. The method for removing a metal compound according to claim 1, wherein the total concentration of the removal compound in the treatment liquid is 5% by mass or more and 50% by mass or less.

4. The method for removing a metal compound according to any one of claims 1 to 3, wherein the removal compound contains at least one selected from ammonium salts of the carboxylic acid, sodium salts of the carboxylic acid, and potassium salts of the carboxylic acid.

5. The method for removing a metal compound according to any one of claims 1 to 4, wherein the pH of the treatment liquid at 25°C is 1 or more and 9 or less.

6. The method for removing a metal compound according to any one of claims 1 to 5, wherein the temperature of the treatment liquid is 0°C or more and 100°C or less.

7. The method for removing a metal compound according to any one of claims 1 to 6, wherein the contact time between the metal compound and the treatment liquid is 1 second or more and 60 minutes or less.

8. The ratio of the removal rate of the metal compound to be removed to the removal rate of the object not to be removed is 10 or more, and the object not to be removed is at least one selected from silicon dioxide, silicon nitride, polysilicon, tungsten alone, cobalt alone, nickel alone, tantalum alone, titanium alone, iron alone, copper alone, and molybdenum alone. The method for removing a metal compound according to any one of claims 1 to 7.

9. The method for removing a metal compound according to any one of claims 1 to 8, wherein the concentration of the oxidizing agent in the treatment liquid is 1% by mass or less.

10. The method for removing a metal compound according to claim 9, wherein the oxidizing agent is hydrogen peroxide.

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