Semiconductor processing solution and method for using same as low-toxicity semiconductor processing solution

Abstract

Provided is a semiconductor processing solution containing the following (A) to (E): (A) a quaternary ammonium ion represented by formula (1); (B) a halide ion; (C) a hydroxide ion; (D) an oxidizer; and (E) water. (In the formula, R1, R2, R3, and R4 are each independently a C1-16 alkyl group, provided that the number of carbon atoms in at least one alkyl group among R1, R2, R3, and R4 is 2-16.)

Description

Semiconductor processing solution and method for using it as a low-toxicity semiconductor processing solution

[0001] The present invention relates to a semiconductor processing solution and a method for using the solution as a low-toxicity semiconductor processing solution, and more particularly to a semiconductor processing solution containing a predetermined quaternary ammonium ion, a halide ion, a hydroxide ion, an oxidizing agent, and water.

[0002] Quaternary ammonium compounds are used as phase transfer catalysts, surfactants, disinfectants, etc. Among quaternary ammonium compounds, tetramethylammonium hydroxide, in particular, is a type of organic alkali that exhibits strong basicity and is used in semiconductor processing solutions used in cleaning, etching, developing, etc. during semiconductor manufacturing.

[0003] For example, Patent Document 1 discloses a ruthenium semiconductor processing solution containing hypobromite ions.

[0004] International Publication No. 2021 / 059666

[0005] The examples of Patent Document 1 disclose a ruthenium semiconductor processing solution using tetramethylammonium hydroxide as a basic compound. However, the present inventors have noted that aqueous tetramethylammonium hydroxide (hereinafter also referred to as TMAH) solutions are highly toxic and require careful handling. Furthermore, semiconductor processing solutions containing an oxidizing agent can remove or process transition metals by oxidizing and dissolving (etching) the transition metals with the oxidizing agent, but they have found that surface roughness after etching can be a problem. Therefore, an object of the present invention is to provide a semiconductor processing solution that can suppress surface roughness after etching and is low in toxicity. Another object of the present invention is to provide a method for using a low-toxicity semiconductor processing solution.

[0006] The present inventors have conducted extensive research to obtain a low-toxicity semiconductor processing solution, and as a result have found that a semiconductor processing solution containing a specific quaternary ammonium ion, a halide ion, a hydroxide ion, an oxidizing agent, and water is low-toxic and can suppress surface roughness after etching, leading to the completion of the present invention.

[0007] That is, the present invention is configured as follows: Item 1: A semiconductor processing solution comprising the following (A) to (E): (A) a quaternary ammonium ion represented by the following formula (1): (B) a halide ion: (C) a hydroxide ion: (D) an oxidizing agent: (E) water (In the formula, R １ , R ２ , R ３ , and R ４ are each independently an alkyl group having 1 to 16 carbon atoms, provided that R １ , R ２ , R ３ , and R ４ Among these, one or more alkyl groups have 2 to 16 carbon atoms.) Item 2 R in the formula (1) １ , R ２ , R ３ , and R ４ Item 3. The semiconductor processing solution according to Item 1, wherein not all of R in formula (1) are the same alkyl group. １ , R ２ , and R ３ is a methyl group, and R ４ is an alkyl group having 2 to 16 carbon atoms. Item 4. The semiconductor processing solution according to any one of Items 1 to 3, wherein the (B) halide ion is a chloride ion or a bromide ion. Item 5. The semiconductor processing solution according to any one of Items 1 to 4, wherein the concentration of the halide ion in the semiconductor processing solution is 0.1 ppm by mass to 5.0% by mass. Item 6. The semiconductor processing solution according to any one of Items 1 to 5, wherein an LD50 value calculated assuming that the hydroxide of the quaternary ammonium ion is 100% by mass exceeds 50 mg / kg in a toxicity test using rats based on the OECD TG420 acute oral toxicity test. Item 7. The semiconductor processing solution according to any one of Items 1 to 6, wherein the oxidizing agent contains at least one halogen oxygen acid ion selected from the group consisting of hypochlorite ion, hypobromite ion, and periodate ion. Item 8. The semiconductor processing solution according to any one of Items 1 to 7, further comprising one or more compounds selected from the group consisting of alcohols and amines. Item 9. A method of using the semiconductor processing solution according to any one of Items 1 to 8 as a low-toxicity semiconductor processing solution.

[0008] According to the present invention, a low-toxicity semiconductor processing solution is provided. As a result, a semiconductor processing solution that is highly safe during use and also leads to a low environmental impact is provided. Also, a method for using the low-toxicity semiconductor processing solution is provided.

[0009] FIG. 2 is an explanatory diagram showing an electrolytic cell.

[0010] 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.

[0011] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, and "A to B" means that the range is from A to B. Furthermore, when a numerical range is expressed in stages, the upper and lower limits of each numerical range can be combined in any way.

[0012] The semiconductor processing solution of the present invention contains the following (A) to (E): (A) a quaternary ammonium ion represented by the following formula (1), (B) a halide ion, (C) a hydroxide ion, (D) an oxidizing agent, and (E) water. (In the formula, R １ , R ２ , R ３ , and R ４ are each independently an alkyl group having 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4), provided that R １ , R ２ , R ３ , and R ４ Among these, one or more alkyl groups have 2 to 16 carbon atoms (preferably 2 to 8, more preferably 2 to 4).

[0013] By including the quaternary ammonium ion represented by the formula (1) above, the semiconductor processing solution is likely to be less toxic than a semiconductor processing solution using tetramethylammonium hydroxide. Furthermore, by including the quaternary ammonium ion represented by the formula (1) above, the etching rate can be improved. Furthermore, roughness of the metal surface after etching can be suppressed. R１ ~R ４ If the number of carbon atoms in R exceeds the above range, the steric hindrance of the quaternary ammonium ion becomes large, and the etching rate may decrease. １ ~R ４ If the number of carbon atoms exceeds the above range, the quaternary ammonium halide described below becomes difficult to dissolve, which may make it difficult to produce a semiconductor processing solution.

[0014] In the formula (1), R １ , R ２ , R ３ , and R ４ It is also preferable that not all of R are the same alkyl group. In other words, the compounds shown in the following (1) to (3) are preferred. (1) R １ , R ２ , R ３ , and R ４ (2) A compound in which any three of R are the same alkyl group and the remaining one is a different alkyl group from the above. １ , R ２ , R ３ , and R ４ (3) A compound in which any two of R are the same alkyl group and the remaining two are different alkyl groups (the remaining two may be the same or different). １ , R ２ , R ３ , and R ４ In the case of the above (1), R １ , R ２ , R ３ , and R ４ and the remaining one is an alkyl group having 1 to 16 carbon atoms, and the first three and the remaining one are different alkyl groups, and either the first three or the remaining one has 2 to 16 carbon atoms. １ , R ２ , R ３ , and R ４Preferably, three of the groups R are the same, and the remaining one is an alkyl group having 2 to 16 carbon atoms different from the groups R. In this case, the compound represented by formula (1) has two types of alkyl groups. １ , R ２ , R ３ , and R ４ In the case of (2) above, compounds in which any three of R are methyl groups and the remaining alkyl group has 2 to 16 carbon atoms are preferred. Among these, compounds in which the remaining alkyl group has 2 to 8 carbon atoms are more preferred, and compounds in which the remaining alkyl group has 2, 3, or 4 carbon atoms are even more preferred. １ , R ２ , R ３ , and R ４ In this case, the compound represented by formula (1) has two or three types of alkyl groups. In the case of (3) above, R １ , R ２ , R ３ , and R ４ are all different alkyl groups, at least one of which has a carbon number of 2 to 16. In this case, the compound represented by formula (1) has four types of alkyl groups.

[0015] In addition, in the formula (1), R １ , R ２ , R ３ , and R ４ may all be the same alkyl group. For example, R １ , R ２ , R ３ , and R ４ may all be ethyl, propyl, or butyl.

[0016] Specific examples of the quaternary ammonium ion represented by the above formula (1) include tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, ethyltrimethylammonium ion, diethyldimethylammonium ion, triethylmethylammonium ion, propyltrimethylammonium ion, butyltrimethylammonium ion, etc. These quaternary ammonium ions may be used alone or in combination.

[0017] The semiconductor processing liquid contains hydroxide ions. The semiconductor processing liquid contains quaternary ammonium ions represented by the above formula (1) and hydroxide ions, which can be said to indicate that the semiconductor processing liquid contains quaternary ammonium hydroxide containing quaternary ammonium ions represented by the above formula (1) and hydroxide ions. The inclusion of quaternary ammonium hydroxide allows the semiconductor processing liquid to be used as a semiconductor processing liquid.

[0018] The concentrations of the quaternary ammonium ions represented by formula (1) and hydroxide ions in the semiconductor processing solution are not particularly limited, but are preferably prepared at 1.00 to 65.00 mass% as quaternary ammonium hydroxide. For example, the quaternary ammonium hydroxide is more preferably used at 1.00 to 5.00 mass%, and even more preferably at 1.50 to 3.50 mass%. It is also preferably 15.00 to 35.00 mass%, and even more preferably 20.00 to 30.00 mass%. Furthermore, the molar concentration of the quaternary ammonium hydroxide is preferably 0.10 to 0.50 mol / L, and even more preferably 0.15 to 0.35 mol / L.

[0019] The concentration of the quaternary ammonium ion represented by formula (1) in the semiconductor processing solution is preferably 0.01 to 20.00 mass%, more preferably 0.01 to 10.00 mass%, and even more preferably 0.05 to 5.00 mass%. The concentration of hydroxide ions in the semiconductor processing solution is preferably 0.001 mass ppm to 2.00 mass%, more preferably 0.01 mass ppm to 0.20 mass%, and even more preferably 0.1 mass ppm to 0.20 mass%.

[0020] The semiconductor processing solution contains an oxidizing agent. The inclusion of an oxidizing agent can impart etching functionality. The type of oxidizing agent is not particularly limited, and examples include hydrogen peroxide, ozone, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, hypobromous acid, bromous acid, bromic acid, perbromic acid, hypoiodous acid, iodous acid, iodic acid, periodic acid, salts thereof, and ions generated by dissociation of these salts, as well as one or more selected from the group consisting of hydrogen peroxide, ozone, fluorine, chlorine, bromine, iodine, permanganate, chromate, dichromate, and cerium salt. For example, the oxidizing agent may contain at least one halogen oxygen acid ion selected from the group consisting of hypochlorite ions, hypobromite ions, and periodate ions. The type of preferred oxidizing agent varies depending on the transition metal to be etched. For example, in the case of Si, W, and Mo, hydrogen peroxide, hypochlorous acid and hypochlorite ions, hypobromous acid and hypobromite ions, and periodic acid and periodate ions are preferably used; in the case of Ti-based metals, hydrogen peroxide is preferably used; and in the case of Ru-based metals, hypochlorite ions, hypobromite ions, periodate ions, and permanganate ions are preferably used.

[0021] The semiconductor processing solution may contain one or more oxidizing agents. The inclusion of multiple oxidizing agents may stabilize the etching rate or improve the stability of the semiconductor processing solution when reused. For example, when hypobromite ions are included as the first oxidizing agent, the hypobromite ions consumed in metal etching lose their oxidizing power and convert to bromide ions. In this case, the greater the amount of bromide ions converted to bromide ions, the lower the etching ability. In semiconductor wafer manufacturing plants, recycling and reusing processing solutions is common from the perspective of cost reduction. However, if the etching ability decreases due to the reuse of processing solutions, it becomes difficult to reliably manufacture semiconductor wafers. On the other hand, when the semiconductor processing solution contains multiple oxidizing agents, for example, when hypochlorite ions are included in addition to hypobromite ions, the bromide ions that have lost their oxidizing power are oxidized by hypochlorite ions and converted to hypobromite ions. This makes it possible to suppress a decrease in the concentration of hypobromite ions in the semiconductor processing solution, making it less likely that the etching rate will decrease even when the semiconductor processing solution is reused.

[0022] (Counter Cation of Oxidizing Agent) The counter cation of the oxidizing agent contained in the semiconductor processing solution of the present invention is not particularly limited, but is preferably a metal ion or an onium ion. Examples of metal ions that can be used include alkali metal ions such as sodium, potassium, and calcium, and alkaline earth metal ions such as magnesium and calcium. Examples of onium ions that can be used include quaternary ammonium ions represented by the above formula (1). In semiconductor manufacturing, if metals or metal ions remain on a semiconductor wafer, they may cause abnormalities in the electrical characteristics and processed shape. Therefore, it is desirable to contain as few metals and metal ions as possible, and therefore onium ions are preferred as the counter cation of the oxidizing agent.

[0023] (Hydrogen Peroxide) The hydrogen peroxide that can be contained in the semiconductor processing solution of the present invention can be prepared by adding a commercially available aqueous hydrogen peroxide solution to the semiconductor processing solution. The hydrogen peroxide content in the semiconductor processing solution is not particularly limited, but is preferably 0.001 mol / L to 6.0 mol / L, and more preferably 0.01 mol / L to 3.0 mol / L. A hydrogen peroxide content within the above range enables stable etching of transition metals at a sufficient rate. A hydrogen peroxide content below 0.001 mol / L results in a slow etching rate of transition metals, making it less practical. On the other hand, a hydrogen peroxide content above 6.0 mol / L increases the risk of decomposition of hydrogen peroxide, making stable etching of transition metals difficult. The hydrogen peroxide content in the semiconductor processing solution can be confirmed using widely known methods. For example, sulfuric acid can be added to a semiconductor processing solution containing hydrogen peroxide, and the hydrogen peroxide concentration can be determined by oxidation-reduction titration using a potassium permanganate solution under sulfuric acid acidity.

[0024] (Hypochlorite ions) The hypochlorous acid and hypochlorite ions that can be contained in the semiconductor treatment solution of the present invention may be generated in the treatment solution, or may be added to the treatment solution as hypochlorite. The hypochlorite referred to here refers to a salt containing hypochlorite ions, or a solution containing such a salt. To generate hypochlorite ions in the treatment solution, for example, chlorine gas may be blown into the treatment solution. In this case, from the viewpoint of efficiently generating hypochlorite ions, the treatment solution is preferably 50°C or less. If the treatment solution is 50°C or less, not only can hypochlorite ions be generated efficiently, but the generated hypochlorite ions can also be stably used in the treatment solution. Furthermore, in order to dissolve as much chlorine as possible in the treatment solution, the temperature of the treatment solution is more preferably 30°C or less, and most preferably 25°C or less. There is no particular lower limit for the temperature of the treatment solution, but it is preferable that the treatment solution does not freeze. Therefore, the treatment solution is preferably −35°C or higher, more preferably −15°C or higher, and most preferably 0°C or higher. There are no particular limitations on the pH of the treatment solution into which the chlorine gas is blown, but if the treatment solution has an alkaline pH, it can be used for semiconductor treatment immediately after hypochlorite ions are generated.

[0025] Furthermore, when hypochlorite ions are generated by blowing chlorine gas into the treatment liquid, chloride ions (Cl － ) is contained, chlorine gas (Cl ２ The solubility of Cl dissolved in the treatment solution is improved. ２ is Cl － and Cl ３ － reacts with Cl ３ － and Cl ５ － This is because the complex ions such as Cl are formed and stabilized in the treatment solution. ２ , Cl － , Cl ３ － , Cl ５ － A treatment solution containing a large amount of the above can generate a larger amount of hypochlorite ions, and therefore can be suitably used as the treatment solution of the present invention. In addition, hypochlorite ions can be produced in the treatment solution by oxidizing chlorine-containing compounds with an oxidizing agent.

[0026] To add hypochlorite ions as a compound to the treatment solution, hypochlorous acid, chlorine water, and / or hypochlorite may be added. As hypochlorite, sodium hypochlorite, potassium hypochlorite, and tetraalkylammonium hypochlorite are preferred, and hypochlorous acid or tetraalkylammonium hypochlorite is more preferred because it does not contain metal ions that are problematic in semiconductor manufacturing. The tetraalkylammonium hypochlorite can be easily obtained by passing chlorine gas through a tetraalkylammonium hydroxide solution. It can also be obtained by mixing hypochlorous acid and a tetraalkylammonium hydroxide solution. Furthermore, tetraalkylammonium hypochlorite can also be obtained by substituting cations contained in hypochlorites such as sodium hypochlorite with tetraalkylammonium ions using an ion exchange resin.

[0027] The concentration of the hypochlorite ions in the semiconductor processing solution of the present invention is not particularly limited as long as it does not deviate from the object of the present invention, but is preferably 0.001 mol / L or more and 1.5 mol / L or less. If it is less than 0.001 mol / L, the etching rate of transition metals is low and practicality is low. On the other hand, if it exceeds 1.5 mol / L, decomposition of hypochlorite ions is likely to occur, making the etching rate of transition metals difficult to stabilize. In order to stably etch transition metals at a sufficient rate, the concentration of the hypochlorite ions is preferably 0.001 mol / L or more and 1.5 mol / L or less, more preferably 0.005 mol / L or more and 1.0 mol / L or less, and most preferably 0.01 mol / L or more and 0.40 mol / L or less, in terms of the amount of chlorine element contained in the hypochlorite ions.

[0028] The concentration of hypochlorite ions in a semiconductor processing solution can be confirmed using widely known methods. For example, by using ultraviolet-visible spectrophotometry, absorption due to hypochlorite ions can be easily confirmed, and the hypochlorite ion concentration can be determined from the intensity of the absorption peak (generally around 292 nm, depending on the pH of the processing solution and the hypochlorite ion concentration, etc.). Furthermore, the hypochlorite ion concentration can also be determined by iodometric titration. Alternatively, the hypochlorite ion concentration can be determined from the oxidation-reduction potential (ORP) of the processing solution. Measurement by ultraviolet-visible spectrophotometry is most preferable from the viewpoint of non-contact and continuous measurement. Note that when measuring the hypochlorite ion concentration by ultraviolet-visible spectrophotometry, if there is absorption due to other chemical species, the hypochlorite ion concentration can be determined with sufficient accuracy by performing data processing such as spectral division and baseline correction, or by appropriately selecting a reference.

[0029] (Hypobromite ion) The hypobromite ion that can be contained in the semiconductor processing solution of the present invention may be generated in the semiconductor processing solution, or may be added to the semiconductor processing solution as a hypobromite. The hypobromite salt referred to here means a salt containing hypobromite ion or a solution containing the salt. Hypobromite ion (BrO －, also referred to as BrO) in a semiconductor processing solution can be generated, for example, by blowing bromine gas into the semiconductor processing solution. In this case, from the viewpoint of efficiently generating hypobromite ions, the semiconductor processing solution is preferably kept at a temperature of 20°C or higher and 50°C or lower. If the semiconductor processing solution is kept at 50°C or lower, not only can hypobromite ions be efficiently generated, but the generated hypobromite ions can also be stably used in semiconductor processing. Furthermore, in order to dissolve as much bromine as possible in the semiconductor processing solution, the temperature of the semiconductor processing solution is more preferably 20°C or higher, and most preferably 30°C or higher. There are no particular limitations on the pH of the semiconductor processing solution into which bromine gas is blown, but if the semiconductor processing solution has an alkaline pH, it can be used for semiconductor processing immediately after generating hypobromite ions.

[0030] Furthermore, when hypobromite ions are generated by blowing bromine gas into the semiconductor processing solution, bromide ions (Br － ) is contained, bromine gas (Br ２ The solubility of Br dissolved in the semiconductor processing solution is improved. ２ Br － YaBr ３ － reacts with Br ３ － YaBr ５ － This is because the Br forms a complex ion such as ２ ,Br － ,Br ３ － ,Br ５ － A semiconductor processing solution containing a large amount of the above can generate a larger amount of hypobromite ions, and therefore can be suitably used as the semiconductor processing solution of the present invention.

[0031] Hypobromite ions can also be produced in semiconductor processing solutions by oxidizing bromine-containing compounds with an oxidizing agent. For example, by mixing hypochlorite ions as an oxidizing agent with tetramethylammonium bromide as a bromine-containing compound, the hypochlorite ions oxidize bromide ions to produce hypobromite ions. Hypobromite ions can be added as a compound to semiconductor processing solutions by adding hypobromous acid, bromine water, and / or hypobromite salts. Suitable hypobromites include sodium hypobromite, potassium hypobromite, and tetraalkylammonium hypobromites. Hypobromite or tetraalkylammonium hypobromites are more suitable because they do not contain metal ions that are problematic in semiconductor manufacturing. The aforementioned tetraalkylammonium hypobromites can be easily obtained by passing bromine gas through a tetraalkylammonium hydroxide solution. Alternatively, hypobromite can be obtained by mixing hypobromous acid with a tetraalkylammonium hydroxide solution. Furthermore, tetraalkylammonium hypobromite can also be obtained by substituting the cation contained in a hypobromite such as sodium hypobromite with a tetraalkylammonium ion using an ion exchange resin.

[0032] The content of hypobromite ions in the semiconductor processing solution is not particularly limited, but is preferably 0.001 mol / L or more and 0.50 mol / L or less, and more preferably 0.001 mol / L or more and 0.20 mol / L or less. By having the hypobromite ion content within the above range, transition metals can be stably etched at a sufficient rate. If the content is less than 0.001 mol / L, the transition metal etching rate is slow and practically inadequate. On the other hand, if the content exceeds 0.50 mol / L, decomposition of hypobromite ions is likely to occur, making it difficult to stably etch transition metals. The content of hypobromite ions in the semiconductor processing solution can be confirmed using widely known methods. For example, by using ultraviolet-visible absorptiometry, absorption due to hypobromite ions can be easily confirmed, and the hypobromite ion concentration can be determined from the intensity of the absorption peak (generally around 330 nm, depending on the pH and hypobromite ion concentration of the residue removal solution, etc.). Furthermore, the hypobromite ion concentration can also be determined by iodometric titration. Alternatively, the hypobromite ion concentration can be determined from the oxidation-reduction potential (ORP) of the residue removal solution. Measurement by ultraviolet-visible absorptiometry is most preferable because it is non-contact and allows for continuous measurement. When measuring the hypobromite ion concentration by ultraviolet-visible absorptiometry, if there is absorption due to other chemical species, the hypobromite ion concentration can be measured with sufficient accuracy by performing data processing such as spectral splitting and baseline correction, or by appropriately selecting a reference.

[0033] (Periodic Acid Compound) Examples of periodic acid compounds that can be contained in the semiconductor processing solution of the present invention include orthoperiodic acid, metaperiodic acid, and ions thereof. The processing solution of the present invention containing these periodic acids can be prepared by adding commercially available periodic acid to the semiconductor processing solution. The content of the periodic acid compound in the semiconductor processing solution is not particularly limited, but is preferably 0.001 mol / L or more and 1.0 mol / L or less, and more preferably 0.01 mol / L or more and 0.5 mol / L or less. By having the content of the periodic acid compound within the above range, the transition metal can be etched stably at a sufficient rate. If the content is less than 0.001 mol / L, the transition metal etching rate is low and practicality is low. On the other hand, if the content exceeds 1.0 mol / L, the transition metal etching becomes difficult to stabilize. The content of the periodic acid compound in the semiconductor processing solution can be confirmed using widely known methods. For example, sulfuric acid is added to a semiconductor processing solution containing a periodate compound, and the periodate concentration can be determined by iodometric titration under sulfuric acid acidity.

[0034] The halide ion is not particularly limited, but specific examples include one or more selected from the group consisting of chloride ions, bromide ions, and iodide ions. Furthermore, chloride ions or bromide ions are preferred. When a semiconductor processing solution contains halide ions, roughness of the metal surface after etching can be suppressed. It is presumed that halogens are present to a certain extent even on the metal surface in the processing solution, and therefore it is presumed that it is possible to control the etching rate of the metal by the oxidizing agent to a certain extent. It is presumed that uniforming the etching rate of the metal can suppress surface roughness due to etching.

[0035] The concentration of halide ions in the semiconductor processing solution is not particularly limited, but is preferably 0.01 ppm by mass to 20.0% by mass, more preferably 0.1 ppm by mass to 10.0% by mass, and even more preferably 0.1 ppm by mass to 5.0% by mass. If the semiconductor processing solution contains a large amount of halide ions, the halide ions may remain on the surface of the semiconductor. In such cases, the physical properties of the semiconductor may be degraded. Furthermore, if the halide ion concentration in the semiconductor processing solution is less than 0.01 ppm by mass, surface roughness may occur due to non-uniform etching. By having the halide ion concentration in the above range, the physical properties of the semiconductor obtained using the semiconductor processing solution are likely to be improved.

[0036] The concentration of halide ions in semiconductor processing solutions can be analyzed by ion chromatography. When the alkaline aqueous solution is highly concentrated, neutralization analysis is particularly effective. Specifically, before introducing the semiconductor processing solution into anion ion chromatography, the cations in the processing solution are exchanged for hydrogen ions, and the hydroxide ions are converted into water. This allows the hydroxide ions to be removed. Furthermore, concentration enhances sensitivity. This method allows the measurement of low concentrations of halide ions. Details will be described later.

[0037] The semiconductor processing solution contains water. The type of water is not particularly limited, and any known water can be used, with ultrapure water having reduced metal impurities being particularly preferred. The water content in the semiconductor processing solution is not particularly limited, but is preferably 10.00% by mass or more, more preferably 20.00% by mass or more, and even more preferably 30.00% by mass or more. It is also preferably 99.99% by mass or less, and even more preferably 99.90% by mass or less. For example, it is preferably 10.00 to 99.99% by mass, more preferably 20.00 to 99.99% by mass, and even more preferably 30.00 to 99.90% by mass.

[0038] The semiconductor processing solution may also contain one or more compounds selected from the group consisting of alcohols and amines. The inclusion of such compounds improves the wettability of the transition metal surface, making it easier to suppress surface roughness due to non-uniform etching. The concentration of the one or more compounds selected from the group consisting of alcohols and amines in the semiconductor processing solution is not particularly limited, but is preferably 0.1 mass ppb to 1.0 mass%, and more preferably 1 mass ppb to 0.1 mass%. The alcohol is not particularly limited, and known alcohols can be used. Examples include primary alcohols such as methanol, ethanol, and 1-propanol, secondary alcohols such as 2-propanol and 2-butanol, and tertiary alcohols such as 2-methyl-2-propanol. The valence of the alcohol is not particularly limited, and either monohydric alcohols or dihydric or higher alcohols may be used. Among these, primary alcohols are preferred from the standpoint of low cost and easy availability. Furthermore, alcohols with 16 or fewer carbon atoms (more preferably 2 to 8, even more preferably 2 to 4) are preferred, as longer chains increase the likelihood of adsorption inhibition during semiconductor processing.

[0039] The amine is not particularly limited, and known amines can be used. Examples include primary amines such as methylamine, secondary amines such as dimethylamine, and tertiary amines such as trimethylamine. The amine valence is also not particularly limited, and either monovalent amines or divalent or higher amines can be used. Among these, tertiary amines are preferred from the viewpoint of low cost and easy availability. Furthermore, amines having 16 or fewer carbon atoms (more preferably 2 to 8, and even more preferably 2 to 4) are preferred, since longer chains are more likely to cause adsorption inhibition during semiconductor processing.

[0040] To evaluate the toxicity of aqueous quaternary ammonium hydroxide solutions, it is preferable that the median lethal dose (LD50) value, calculated based on 100% by mass of the hydroxide of the quaternary ammonium ion, exceeds 50 mg / kg in a toxicity test using rats based on OECD TG420 acute oral toxicity. This increases safety during use and contributes to a lower environmental impact. Furthermore, in the GHS classification, an LD50 value of 50 mg / kg or less corresponds to Category 2, which imposes stricter regulations on storage, transportation, etc., and a value of 5 mg / kg or less corresponds to Category 1, which is even stricter. Therefore, it is preferable that the LD50 value exceeds 50 mg / kg. The LD50 value is more preferably greater than 100 mg / kg, even more preferably greater than 200 mg / kg, and particularly preferably greater than 300 mg / kg. The LD50 value can be preferably more than 50 mg / kg and not more than 1000 mg / kg, more preferably more than 100 mg / kg and not more than 1000 mg / kg, even more preferably more than 200 mg / kg and not more than 1000 mg / kg, and most preferably more than 300 mg / kg and not more than 1000 mg / kg. The LD50 value can be adjusted by changing the type of quaternary ammonium ion represented by the above formula (1).

[0041] In view of this toxicity, for example, R １ , R ２ , and R ３ is an alkyl group having one carbon atom, and R ４ is a quaternary ammonium ion, R is an alkyl group having 2 to 4 carbon atoms, １ , R ２ , R ３ , and R ４ is a quaternary ammonium ion, R is an alkyl group having 2 carbon atoms, １ , R ２ , R ３ , and R ４ is a quaternary ammonium ion, R is an alkyl group having 3 carbon atoms, １ , R ２ , R ３ , and R ４is an alkyl group having 4 carbon atoms. More specifically, an ethyltrimethylammonium ion, a propyltrimethylammonium ion, a butyltrimethylammonium ion, a tetraethylammonium ion, a tetrapropylammonium ion, or a tetrabutylammonium ion is preferred.

[0042] The semiconductor processing solution can be used, for example, as an etching solution. It can also be used, for example, as a semiconductor processing solution for transition metals. The transition metal in the present invention includes, for example, one or more metals selected from the group consisting of Si, Ru, Rh, Ti, Ta, Co, Cr, Hf, Os, Pt, Ni, Mn, Cu, Zr, La, Mo, and W. The semiconductor processing solution may also contain oxides, nitrides, oxynitrides, carbides, or silicides of these transition metals. Furthermore, the semiconductor processing solution can be used as a low-toxicity semiconductor processing solution. That is, one aspect of the present invention is a method of using the semiconductor processing solution of the present invention as a low-toxicity semiconductor processing solution.

[0043] The method for producing a semiconductor processing solution of the present invention is not particularly limited, and may include, for example, a preparation step A of preparing an alkaline aqueous solution for semiconductors as a raw material, a mixing step of mixing the alkaline aqueous solution for semiconductors, an oxidizing agent, and, if necessary, water to a predetermined concentration to obtain a mixture, and a dissolving step of dissolving the obtained mixture to a uniform concentration. Alternatively, these steps may be combined into one step.

[0044] The preparation step A for preparing an alkaline aqueous solution for semiconductors is not particularly limited. However, from the viewpoint of suppressing the halide ion concentration, it is preferable to obtain the alkaline aqueous solution for semiconductors by electrolyzing a quaternary ammonium halide aqueous solution. That is, the preparation step A preferably includes an electrolysis step for electrolyzing a quaternary ammonium halide aqueous solution. Specifically, it preferably includes an electrolysis step for electrolyzing a quaternary ammonium halide aqueous solution containing the following (A), (B), and (E). (A), (B), and (E) can be those described above. (A) A quaternary ammonium ion represented by the following formula (1): (B) A halide ion (E) Water (In the formula, R １ , R ２ , R ３ , and R ４ are each independently an alkyl group having 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4), provided that R １ , R ２ , R ３ , and R ４ Among these, one or more alkyl groups have 2 to 16 carbon atoms (preferably 2 to 8, more preferably 2 to 4).

[0045] To produce an alkaline solution for semiconductors by electrolysis, an electrolytic cell can be used, which has one or more cation exchange membranes disposed between an anode and a cathode, a raw material chamber for supplying a quaternary ammonium halide solution as a raw material, and a base chamber (cathode chamber) for producing a quaternary ammonium hydroxide solution. In this production method using an electrolytic cell, quaternary ammonium ions contained in the quaternary ammonium halide solution pass through the cation exchange membrane disposed on the cathode side during electrolysis. This produces a quaternary ammonium hydroxide solution in the base chamber. While the above example illustrates the use of one or more cation exchange membranes, an electrolytic cell containing multiple membranes selected from the group consisting of cation exchange membranes, anion exchange membranes, and bipolar membranes (composite membranes consisting of a cation exchange membrane and an anion exchange membrane) may also be used, as long as it can produce a quaternary ammonium hydroxide solution.

[0046] At this time, halide ions, which are anions of the quaternary ammonium halide, move to the anode side, but some of the halide ions also move to the cathode side due to diffusion. For this reason, depending on the concentration of the liquid used as the raw material, halide ions of about 1 to several tens of ppm may be mixed into the aqueous quaternary ammonium hydroxide solution.

[0047] The method for producing a semiconductor processing solution may include, prior to the electrolysis step, a preparation step B of preparing an aqueous quaternary ammonium halide solution to be used as a raw material in the electrolysis step. The preparation step B is not particularly limited, and for example, the aqueous quaternary ammonium halide solution can be prepared by producing an aqueous quaternary ammonium halide solution. Furthermore, the method for producing the aqueous quaternary ammonium halide solution is not particularly limited. For example, from the viewpoints of productivity and quality, a step of reacting a trialkylamine with an alkyl halide in ultrapure water to obtain a quaternary ammonium halide is preferred.

[0048] The trialkylamine and alkyl halide used as raw materials are not particularly limited as long as they can produce the quaternary ammonium ion represented by formula (1). Specifically, the alkyl groups contained in the trialkylamine and the alkyl halide can be those in which at least one alkyl group has 2 to 16 carbon atoms (preferably 2 to 8, more preferably 2 to 4), and the remaining alkyl groups have 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4). The halide ion, which is the anion of the alkyl halide, can be the same as that described in (B) above. Because impurities contained in the quaternary ammonium halide diffuse into and become mixed into the aqueous quaternary ammonium hydroxide solution, it is preferable to use a high-purity quaternary ammonium halide. Specifically, the concentration of any one metal selected from lithium, sodium, potassium, aluminum, magnesium, calcium, chromium, manganese, iron, nickel, cobalt, copper, silver, cadmium, barium, zinc, and lead in the aqueous quaternary ammonium halide solution is preferably 0.01 ppt to 1 ppb by mass.

[0049] Examples will be given below to specifically explain the present invention, but the present invention is not limited to these. The evaluations carried out in the examples and comparative examples were determined by the following methods.

[0050] [Evaluation Method] 1) Halide Ion Concentration The halide ion concentration in the semiconductor processing solution was measured using an ion chromatography analyzer (DIONEX INTEGRATION HPLC, manufactured by Thermo SCIENTIFIC). A KOH aqueous solution was used as the eluent, and the solution was passed through at a flow rate of 1.2 mL / min. The column used was an anion analysis column for hydroxide-based eluents (AS15, manufactured by Thermo SCIENTIFIC), and the column temperature was set to 30°C. After removing background noise using a suppressor, the halide ions in the processing solution were quantified using an electrical conductivity detector.

[0051] 2) Hydroxide ion concentration Neutralization titration of 1 mL of the aqueous solutions prepared in the examples and comparative examples with 0.1 mol / L hydrochloric acid was performed using a Hiranuma automatic titrator (COM-1700, manufactured by Hiranuma). The hydroxide ion concentration was calculated from the amount of 0.1 mol / L hydrochloric acid required for neutralization.

[0052] 3) Etching Test 60 mL of the treatment solution of the example was prepared in a fluororesin container with a lid (manufactured by AsOne, PFA container 94.0 mL). Each evaluation semiconductor wafer piece, measuring 10 x 20 mm, was immersed in the treatment solution for 1 minute at 25°C or 50°C. The change in film thickness before and after treatment was divided by the immersion time to calculate the etching rate, which was then evaluated according to the following criteria. In all cases, ratings A to C were acceptable, and rating D was unacceptable. (Titanium nitride film, ruthenium film, molybdenum film) A: >50 Å / min B: 50-20 Å / min C: 20-10 Å / min (acceptable) D: Unable to etch (Tungsten film) A: >500 Å / min B: 500-100 Å / min C: 100-10 Å / min (acceptable) D: Unable to etch

[0053] 4) Surface evaluation after etching The metal surface was observed before and after etching using a field emission scanning electron microscope (JSM-7800F Prime, manufactured by JEOL Ltd.) to check for the presence or absence of surface roughness, and was evaluated according to the following criteria. Surface roughness was ranked from least to greatest, A to D, with ratings A to C being acceptable levels and rating D being unacceptable. A: No surface roughness was observed B: Some surface roughness was observed C: Roughness was observed over the entire surface, but the roughness was shallow D: Roughness was observed over the entire surface, and the roughness was deep

[0054] 5) Toxicity Tests Data on median lethal dose (LD50) was collected in toxicity tests using rats. For products for which data was not disclosed, toxicity tests based on OECD TG420 Acute Oral Toxicity were conducted to obtain data. The obtained LD50s were converted to 100% by mass of quaternary ammonium hydroxide aqueous solution, and evaluation was performed based on the following criteria. When two or more types of quaternary ammonium hydroxide aqueous solutions were mixed, the LD50s of each quaternary ammonium hydroxide aqueous solution were multiplied by the mixing ratio and the sum was calculated. The results are shown in Table 1. A: LD50 greater than 2000 mg / kg B: LD50 greater than 300 mg / kg to 2000 mg / kg or less C: LD50 greater than 50 mg / kg to 300 mg / kg or less D: LD50 or less A to C grades indicate a low-toxicity semiconductor processing solution, with A to B being preferable.

[0055] (Reagents) The reagents used in the examples and comparative examples are as follows: Hydrogen peroxide (H ２ O ２ ): Fujifilm Wako Pure Chemical Industries, Ltd. Orthoperiodic acid (H ５ IO ６ ): Fujifilm Wako Pure Chemical Industries, Ltd. Metaperiodic acid (HIO ４): manufactured by Sigma-Aldrich; Hydrochloric acid (HCl): manufactured by Kanto Chemical; Hydrobromic acid (HBr): manufactured by Tama Chemical; Hydroiodic acid (HI): manufactured by Tokyo Chemical Industry Co., Ltd.; Ethyltrimethylammonium hydroxide (ETMAH, prepared from raw materials); Propyltrimethylammonium hydroxide (PTMAH, prepared from raw materials); Butyltrimethylammonium hydroxide (BTMAH, prepared from raw materials); Tetrapropylammonium hydroxide (TPAH, manufactured by Tokyo Chemical Industry Co., Ltd.); Tetrabutylammonium hydroxide (TBAH, manufactured by Tokyo Chemical Industry Co., Ltd.); Tetramethylammonium hydroxide (TMAH, manufactured by Tokuyama). TPAH, TBAH, and TMAH were prepared to the concentrations shown in Table 1.

[0056] (Preparation of Quaternary Ammonium Hydroxide Aqueous Solution) ETMAH (ethyltrimethylammonium hydroxide), PTMAH (propyltrimethylammonium hydroxide), and BTMAH (butyltrimethylammonium hydroxide) were prepared by the following procedure. A quaternary ammonium halide aqueous solution was prepared from the raw materials trialkylamine and alkyl halide, and this was used as the raw material to prepare a quaternary ammonium hydroxide aqueous solution by electrolysis. Specifically, in the case of ETMAH, trimethylamine and ethyl chloride were charged in a molar ratio of 1:1 into a reaction vessel containing ultrapure water, and the reaction temperature was maintained at 60°C to prepare a 50% by mass ethyltrimethylammonium chloride aqueous solution. Unreacted trimethylamine and ethyl chloride, and by-product ethanol were each removed under reduced pressure until their concentrations were less than 100 ppm, and then ETMAH was prepared using the electrolytic cell shown in FIG. 1 . In FIG. 1, 1 indicates an anode, 2 indicates a cathode, 3 indicates a power source, 4 indicates an anode chamber, 5 indicates a raw material chamber, 6 indicates an intermediate chamber, 7 indicates a cathode chamber, 8 indicates an anion exchange membrane, and 9 indicates a cation exchange membrane.

[0057] A platinum-plated nickel plate was used as the cathode, a platinum-plated titanium plate as the anode, two Nafion N324 (manufactured by Chemours) cation exchange membranes, and ASE (manufactured by Astom) anion exchange membrane. 0.5N hydrochloric acid was circulated in the anode chamber, a 50% by mass aqueous solution of ethyltrimethylammonium chloride was circulated in the raw material chamber between the anion exchange membrane and the cathode-side cation exchange membrane, and ultrapure water was circulated in the intermediate chamber between the cathode chamber and the two cation exchange membranes. The current density was gradually increased until a final current density of 30 A / dm was achieved. ２ Electrolysis was carried out continuously while maintaining the temperature at 40° C. During the electrolysis, an aqueous solution of ethyltrimethylammonium chloride was replenished so that the concentration of ethyltrimethylammonium chloride in the source chamber was maintained at 40 mass % or more, and when the concentration of ETMAH in the cathode chamber increased to 30 mass %, electrolysis was terminated and an aqueous ETMAH solution was obtained.

[0058] PTMAH and BTMAH were prepared in the same manner as in the preparation of ETMAH, except that propyl chloride and butyl chloride, respectively, were used as the alkyl halide.

[0059] Examples 1 to 5, Comparative Examples 1 and 5 (Preparation of Semiconductor Processing Solutions Containing Hydrogen Peroxide) A processing solution having the composition shown in Table 1 was prepared by adding ion-exchanged water, hydrogen peroxide, and hydrochloric acid to the quaternary ammonium hydroxide aqueous solution obtained by the above procedure. However, in Example 4, the TBAH aqueous solution prepared in the reagent section was used instead of the quaternary ammonium hydroxide aqueous solution obtained by the above procedure. Similarly, in Example 5, the TPAH aqueous solution prepared in the reagent section was used instead of the quaternary ammonium hydroxide aqueous solution obtained by the above procedure. Furthermore, in Comparative Examples 1 and 5, the TMAH aqueous solution prepared in the reagent section was used instead of the quaternary ammonium hydroxide aqueous solution obtained by the above procedure. Furthermore, the amine concentrations in the semiconductor processing solutions were all less than 100 ppm by mass. Furthermore, the alcohol concentrations in the semiconductor processing solutions were all less than 100 ppm by mass.

[0060] Examples 6 to 10, Comparative Example 2 (Preparation of Semiconductor Processing Solution Containing Hypochlorite Ions) The quaternary ammonium hydroxide aqueous solution obtained by the above procedure and ion-exchanged water were mixed in a 2 L glass three-neck flask (manufactured by Cosmos Bead Co., Ltd.) to obtain a 1.69 mol / L quaternary ammonium hydroxide aqueous solution. The pH at this time was 14.2. Next, a rotor (manufactured by AsOne Co., Ltd., total length 30 mm x diameter 8 mm) was placed in the three-neck flask, and a thermometer protection tube (manufactured by Cosmos Bead Co., Ltd., bottom-sealed type) and a thermometer were placed in one opening. Furthermore, a chlorine gas cylinder and a PFA tube (manufactured by Flon Industries Co., Ltd., F-8011-02) connected to a nitrogen gas cylinder and capable of switching between chlorine gas and nitrogen gas at will were connected to the other opening, and the tip of the PFA tube was immersed in the bottom of the aqueous solution. In addition, the remaining opening was connected to a gas washing bottle (AsOne, gas washing bottle, model number 2450 / 500) filled with 5 wt% aqueous sodium hydroxide solution. Nitrogen gas was flowed through the PFA tube at 200 ccm (25°C) for 20 minutes to expel carbon dioxide from the gas phase.

[0061] Thereafter, a magnetic stirrer (AsOne, C-MAG HS10) was placed at the bottom of the three-neck flask and rotated at 300 rpm. While the outer periphery of the three-neck flask was cooled with ice water, chlorine gas (Fujiox, specified purity 99.4%) was supplied at 200 ccm (25°C) for 360 minutes to obtain a 1.5 mol / L aqueous solution of quaternary ammonium hypochlorite (containing 1.5 mol / L quaternary ammonium chloride and 0.05 mol / L quaternary ammonium hydroxide). The liquid temperature during the reaction was 11°C. Hydrochloric acid and an aqueous solution of quaternary ammonium hypochlorite were added to the resulting aqueous solution of quaternary ammonium hypochlorite to prepare a treatment solution with the composition shown in Table 1. However, in Comparative Example 2, the aqueous solution of TMAH prepared in the reagent column was used instead of the aqueous solution of quaternary ammonium hydroxide obtained by the above procedure. Furthermore, the amine concentrations in all of the semiconductor treatment solutions were less than 100 ppm by mass. Furthermore, the alcohol concentration in each of the semiconductor processing solutions was less than 100 ppm by mass.

[0062] Examples 11-15, Comparative Example 3 (Preparation of Semiconductor Processing Solutions Containing Hypobromite Ions) A 0.5 mol / L quaternary ammonium hypobromite solution was obtained by adding hydrobromic acid and a quaternary ammonium hydroxide solution to a mixed solution containing a 1.5 mol / L quaternary ammonium hypochlorite solution and a quaternary ammonium hydroxide solution obtained by the above procedure. Ion-exchanged water, hydrobromic acid, and a quaternary ammonium hydroxide solution were added to the resulting quaternary ammonium hypobromite solution to prepare a processing solution having the composition shown in Table 1. However, in Comparative Example 3, the TMAH aqueous solution prepared in the reagent section was used instead of the quaternary ammonium hydroxide aqueous solution obtained by the above procedure. The amine concentrations in all of the semiconductor processing solutions were less than 100 ppm by mass. Furthermore, the alcohol concentrations in all of the semiconductor processing solutions were less than 100 ppm by mass.

[0063] Examples 16 to 20, Comparative Example 4 Preparation of Semiconductor Processing Solutions Containing Periodate Compounds Orthoperiodic acid or metaperiodic acid was added to the aqueous quaternary ammonium hydroxide solution obtained by the above procedure, and then ion-exchanged water and hydroiodic acid were added to prepare processing solutions having the compositions shown in Table 1. However, in Comparative Example 4, the aqueous TMAH solution prepared in the reagent section was used instead of the aqueous quaternary ammonium hydroxide solution obtained by the above procedure. The amine concentrations in all of the semiconductor processing solutions were less than 100 ppm by mass. The alcohol concentrations in all of the semiconductor processing solutions were less than 100 ppm by mass. In the table, ETMA+ represents ethyltrimethylammonium ion, PTMA+ represents propyltrimethylammonium ion, BTMA+ represents butyltrimethylammonium, TBA+ represents tetrabutylammonium ion, TPA+ represents tetrapropylammonium ion, TMA+ represents tetramethylammonium ion, and ClO represents hypochlorite ion (ClO － ), and BrO represents hypobromite ion (BrO － ) represents

[0064] In Examples 1 to 20, the etching rate, surface roughness, and toxicity test results were all rated C or higher, whereas in Comparative Examples 1 to 5, the toxicity test result was rated D. Furthermore, in Comparative Example 5, the surface roughness was also rated D. These results demonstrate that the semiconductor processing solution according to the embodiment of the present invention can suppress surface roughness after etching and is a low-toxicity semiconductor processing solution.

[0065] 1: Anode 2: Cathode 3: Power supply 4: Anode chamber 5: Raw material chamber 6: Intermediate chamber 7: Cathode chamber 8: Anion exchange membrane 9: Cation exchange membrane

Claims

1. A semiconductor processing solution containing the following (A) to (E): (A) a quaternary ammonium ion represented by the following formula (1); (B) a halide ion; (C) a hydroxide ion; (D) an oxidizing agent; and (E) water. (In the formula, R １ , R ２ , R ３ , and R ４ are each independently an alkyl group having 1 to 16 carbon atoms, provided that R １ , R ２ , R ３ , and R ４ Among these, at least one alkyl group has 2 to 16 carbon atoms.

2. R in the above formula (1) １ , R ２ , R ３ , and R ４ The semiconductor processing solution according to claim 1 , wherein not all of the alkyl groups are the same.

3. R ​​in the above formula (1) １ , R ２ , and R ３ is a methyl group, and R ４ The semiconductor processing solution according to claim 1 or 2, wherein is an alkyl group having 2 to 16 carbon atoms.

4. The semiconductor processing solution according to any one of claims 1 to 3, wherein the (B) halide ion is a chloride ion or a bromide ion.

5. A semiconductor processing solution according to any one of claims 1 to 4, wherein the concentration of said halide ions in said semiconductor processing solution is 0.1 ppm by mass to 5.0% by mass.

6. The semiconductor processing solution according to any one of claims 1 to 5, which has an LD50 value calculated based on 100 mass% of the hydroxide of the quaternary ammonium ion in a toxicity test using rats based on the OECD TG420 acute oral toxicity test, and which exceeds 50 mg / kg.

7. The semiconductor processing solution according to any one of claims 1 to 6, wherein the oxidizing agent contains at least one halogen oxygen acid ion selected from the group consisting of hypochlorite ion, hypobromite ion, and periodate ion.

8. The semiconductor processing solution according to any one of claims 1 to 7, further comprising one or more compounds selected from the group consisting of alcohols and amines.

9. A method for using the semiconductor processing solution according to any one of claims 1 to 8 as a low-toxicity semiconductor processing solution.

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