Alkaline aqueous solution for semiconductor, method for use as low-toxicity alkaline aqueous solution for semiconductor, and method for producing alkaline aqueous solution for semiconductor

Abstract

An alkaline aqueous solution for semiconductors, which contains (A)-(D): (A) a quaternary ammonium ion represented by formula (1); (B) a halide ion; (C) a hydroxide ion; and (D) water. (In the formula, each of R1, R2, R3 and R4 independently represents an alkyl group having 1-16 carbon atoms, and the number of carbon atoms of one or more alkyl groups among R1, R2, R3 and R4 is 2-16)

Description

Technical Field

[0001] This invention relates to an alkaline aqueous solution for semiconductors, a method for using it as a low-toxicity alkaline aqueous solution for semiconductors, and a method for manufacturing an alkaline aqueous solution for semiconductors. More specifically, it relates to an alkaline aqueous solution for semiconductors comprising specified quaternary ammonium ions, halide ions, hydroxide ions, and water. Background Technology

[0002] Quaternary ammonium compounds are used in phase transfer catalysts, surfactants, disinfectants, etc. Among quaternary ammonium compounds, tetramethylammonium hydroxide, in particular, is an organic base exhibiting strong alkalinity and is used in alkaline aqueous solutions for semiconductors in cleaning, etching, and developing solutions during semiconductor manufacturing.

[0003] For example, Patent Document 1 discloses an aqueous solution of tetramethylammonium hydroxide with a metal ion and halide ion content of 2.35% by weight, which is a specified value.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 4-226466 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, the inventors are concerned about the high toxicity of tetramethylammonium hydroxide (hereinafter also referred to as TMAH) aqueous solution and the need for extra care during operation.

[0009] Therefore, the object of the present invention is to provide a low-toxicity alkaline aqueous solution for semiconductors. Furthermore, the object is to provide a method for using this low-toxicity alkaline aqueous solution for semiconductors. Moreover, the object is to provide a method for manufacturing a low-toxicity alkaline aqueous solution for semiconductors.

[0010] Solution for solving the problem

[0011] The inventors conducted repeated and in-depth research to obtain a low-toxicity alkaline aqueous solution for semiconductors. The results showed that an alkaline aqueous solution for semiconductors containing specific quaternary ammonium ions, halide ions, hydroxide ions, and water exhibits low toxicity, thus completing this invention.

[0012] That is, the structure of the present invention is as described below.

[0013] Item 1 An alkaline aqueous solution for semiconductors, comprising the following (A) to (D):

[0014] (A) The quaternary ammonium ion shown in formula (1) below,

[0015] (B) Halogen ions,

[0016] (C) hydroxide ions,

[0017] (D) Water.

[0018]

[0019] (In equation (1), R) 1 R 2 R 3 and R 4 Each is an alkyl group having 1 to 16 carbon atoms, wherein R 1 R 2 R 3 and R 4 In this context, the number of carbon atoms in one or more alkyl groups is 2 to 16.

[0020] Item 2. An alkaline aqueous solution for semiconductors according to Item 1, wherein R in formula (1) 1 R 2 R 3 and R 4 Not all of them are the same alkyl group.

[0021] Item 3. An alkaline aqueous solution for semiconductors according to Item 1 or 2, wherein R in formula (1) 1 R 2 and R 3 For methyl, R in formula (1) 4 It is an alkyl group with 2 to 16 carbon atoms.

[0022] Item 4. An alkaline aqueous solution for semiconductors according to any one of items 1 to 3, wherein the (B) halide ion is a chloride ion or a bromide ion.

[0023] Item 5. An alkaline aqueous solution for semiconductors according to any one of items 1 to 4, wherein the mass of the halide ions when the mass of the hydroxide ions in the alkaline aqueous solution for semiconductors is set to 1 part by mass is 0.0000001 to 0.01 parts by mass.

[0024] Item 6. An alkaline aqueous solution for semiconductors according to any one of items 1 to 5, wherein, in a rat toxicity test based on the OECD-based TG420 acute oral toxicity test, the LD50 value, calculated as 100% by mass of the hydroxide of the quaternary ammonium ion, exceeds 50 mg / kg.

[0025] Item 7 An alkaline aqueous solution for semiconductors according to any one of items 1 to 6, wherein, in the OECD TG202 acute activity inhibition test for quaternary ammonium ions, the EC50 value obtained by conversion with the hydroxide of the quaternary ammonium ions as 100% by mass exceeds 3 mg / L.

[0026] Item 8. An alkaline aqueous solution for semiconductors according to any one of items 1 to 7, further comprising one or more compounds selected from the group consisting of alcohols and amines.

[0027] Item 9 The alkaline aqueous solution for semiconductors according to any one of items 1 to 8 further comprises a surfactant, wherein the concentration of the surfactant in the alkaline aqueous solution for semiconductors is less than 100 ppm by mass.

[0028] Item 10 A grinding composition comprising any one of items 1 to 9 an alkaline aqueous solution for semiconductors and abrasive grains.

[0029] Item 11 A method for using any one of the alkaline aqueous solutions for semiconductors described in Items 1 to 9 as a low-toxicity alkaline aqueous solution for semiconductors.

[0030] Item 12 A method for manufacturing an alkaline aqueous solution for semiconductors according to any one of items 1 to 7, comprising an electrolysis step of electrolyzing an aqueous solution of a quaternary ammonium halide containing (A), (B), and (D) below.

[0031] (A) The quaternary ammonium ion shown in formula (1) below,

[0032] (B) Halogen ions,

[0033] (D) Water,

[0034]

[0035] (In equation (1), R) 1 R 2 R 3 and R 4 Each is an alkyl group having 1 to 16 carbon atoms, wherein R 1 R 2 R 3 and R 4 In this context, the number of carbon atoms in one or more alkyl groups is 2 to 16.

[0036] Item 13. A method for manufacturing an alkaline aqueous solution for semiconductors according to Item 12, wherein, prior to the electrolysis step, a preparation step for preparing the quaternary ammonium halide aqueous solution is included, the preparation step being a step of reacting a trialkylamine with a haloalkane in ultrapure water to obtain the quaternary ammonium halide aqueous solution.

[0037] The effects of the invention

[0038] According to the present invention, a low-toxicity alkaline aqueous solution for semiconductors is provided. As a result, an alkaline aqueous solution for semiconductors is provided that offers high safety during use and achieves low environmental impact. Furthermore, a method for using this low-toxicity alkaline aqueous solution for semiconductors is provided. Moreover, a method for manufacturing the low-toxicity alkaline aqueous solution for semiconductors is provided. Attached Figure Description

[0039] Figure 1 This is an explanatory diagram showing an electrolytic cell. Detailed Implementation

[0040] The embodiments of the present invention will be described in detail below, but the present invention is not limited to these contents as long as it does not depart from its spirit. In addition, the present invention can be implemented in any way without departing from its spirit.

[0041] In this specification, the numerical range represented by "~" refers to the range of values ​​recorded before and after "~" as the lower and upper limits. "A~B" means above A and below B. Furthermore, when numerical ranges are recorded in stages, the upper and lower limits of each numerical range can be arbitrarily combined.

[0042] The alkaline aqueous solution for semiconductors of the present invention comprises the following (A) to (D):

[0043] (A) The quaternary ammonium ion shown in formula (1) below,

[0044] (B) Halogen ions,

[0045] (C) hydroxide ions,

[0046] (D) Water.

[0047]

[0048] (where R) 1 R 2 R 3 and R 4 Each is independently an alkyl group having 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4), wherein R 1 R 2 R 3 and R 4 In this embodiment, the number of carbon atoms in one or more alkyl groups is 2 to 16 (preferably 2 to 8, more preferably 2 to 4).

[0049] By including the quaternary ammonium ions shown in formula (1) above in the alkaline aqueous solution for semiconductors, it is easier to make it less toxic compared to the alkaline aqueous solution for semiconductors using tetramethylammonium hydroxide.

[0050] Furthermore, by including the quaternary ammonium ions shown in formula (1) above, the etching rate can be increased. R1 ~R 4 When the number of carbon atoms exceeds the above range, the steric hindrance of quaternary ammonium ions increases, sometimes reducing the etching rate. Additionally, R... 1 ~R 4 When the number of carbon atoms exceeds the above range, the quaternary ammonium halides described later are difficult to dissolve, and sometimes it is difficult to manufacture alkaline aqueous solutions for semiconductors.

[0051] From the perspectives of low toxicity, etching rate, and ease of manufacturing alkaline aqueous solutions for semiconductors, R in the above formula (1) 1 R 2 R 3 and R 4 It is also preferred that they are not all the same alkyl group. When expressed in another way, it is preferred to be any of the quaternary ammonium ions shown in (1) to (3) below.

[0052] (1) R 1 R 2 R 3 and R 4 Any three of them are the same alkyl group, and the remaining one is a quaternary ammonium ion of a different alkyl group.

[0053] (2) R 1 R 2 R 3 and R 4 Any two of them are the same alkyl group, and the remaining two are quaternary ammonium ions of different alkyl groups (the remaining two can be the same or different).

[0054] (3) R 1 R 2 R 3 and R 4 All are quaternary ammonium ions of different alkyl groups

[0055] In the case of (1) above, the following can be listed: R 1 R 2 R 3 and R 4 Any three of them are alkyl groups with the same number of carbon atoms (1-16), the remaining one is an alkyl group with the same number of carbon atoms (1-16), and the remaining one is a different alkyl group from the first three. Either the first three or the remaining one is a quaternary ammonium ion with the number of carbon atoms (2-16). R in the above formula (1) 1 R 2 R 3 and R 4 In this configuration, three of the groups are identical, and the remaining group is an alkyl group with 2 to 16 carbon atoms, different from the first group. In this case, the quaternary ammonium ion represented by formula (1) has two alkyl groups. In this configuration, R... 1 R2 R 3 and R 4 When any three of the alkyl groups are methyl groups and the remaining alkyl group has 2 to 16 carbon atoms, it readily functions as a surfactant as described later. More preferably, a quaternary ammonium ion with the remaining alkyl group having 2 to 8 carbon atoms is used; even more preferably, a quaternary ammonium ion with 2 to 4 carbon atoms is used; and most preferably, a quaternary ammonium ion with 3 or 4 carbon atoms is used.

[0056] In the case of (2) above, the following can be listed: R 1 R 2 R 3 and R 4 Any two of the alkyl groups are the same alkyl group with 1 to 16 carbon atoms, and the remaining two are alkyl groups with 1 to 16 carbon atoms that are different from the first two. The remaining two are alkyl groups that are the same as or different from each other, and either the first two or the remaining two are quaternary ammonium ions with 2 to 16 carbon atoms. In this case, the quaternary ammonium ion shown in formula (1) has two or three alkyl groups. In this method, R is preferred. 1 R 2 R 3 and R 4 Any two of them are methyl groups, and the remaining two are alkyl groups that are quaternary ammonium ions with 2 to 16 carbon atoms. R 1 R 2 R 3 and R 4 When either of the two alkyl groups is methyl, it readily functions as a surfactant, as described later. More preferably, the remaining two alkyl groups are quaternary ammonium ions with 2 to 8 carbon atoms, even more preferably quaternary ammonium ions with 2 to 4 carbon atoms, and most preferably quaternary ammonium ions with 3 or 4 carbon atoms.

[0057] In the case of (3) above, the following can be listed: R 1 R 2 R 3 and R 4 All of them are different alkyl groups, and at least one of them is a quaternary ammonium ion with 2 to 16 carbon atoms. In this case, the quaternary ammonium ion represented by formula (1) has four alkyl groups. In this method, R is preferred. 1 R 2 R 3 and R 4 Any one of them is a methyl group, and the remaining three are alkyl groups with 2 to 16 carbon atoms, which are quaternary ammonium ions. R 1 R 2 R 3 and R 4When any of the three alkyl groups is methyl, it readily functions as a surfactant as described later. More preferably, the remaining three alkyl groups are quaternary ammonium ions with 2 to 8 carbon atoms, even more preferably quaternary ammonium ions with 2 to 4 carbon atoms, and most preferably quaternary ammonium ions with 3 or 4 carbon atoms.

[0058] In addition, in the above formula (1), R 1 R 2 R 3 and R 4 They can all be the same alkyl group. For example, R 1 R 2 R 3 and R 4 It can be entirely ethyl, propyl, or butyl.

[0059] Specific examples of the quaternary ammonium ions shown in formula (1) above include tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, ethyltrimethylammonium ion, diethyldimethylammonium ion, triethylmethylammonium ion, propyltrimethylammonium ion, butyltrimethylammonium ion, etc. One or more of these quaternary ammonium ions may be used.

[0060] The halide ion is not particularly limited, but if specific examples are given, one or more can be selected from the group consisting of chloride ions, bromide ions, and iodide ions. In addition, chloride ions or bromide ions are preferred.

[0061] The mass fraction of halide ions when the mass of hydroxide ions in the alkaline aqueous solution for semiconductors is set to 1 part by mass is not particularly limited, but is preferably 0.0000001 to 0.01 parts by mass, more preferably 0.0000001 to 0.001 parts by mass, and even more preferably 0.0000001 to 0.0005 parts by mass. The mass fraction of halide ions varies considerably depending on the manufacturing method of the alkaline aqueous solution for semiconductors. In particular, by using an electrolysis-based manufacturing method, it is possible to prepare a solution with reduced halide ions. Furthermore, adjustments can be made by changing conditions such as the structure of the electrolytic cell, the selection of the cation exchange membrane, and the current density used in the electrolysis.

[0062] By setting the mass fraction of halide ions within the above-mentioned range, when using an alkaline aqueous solution for semiconductors as a semiconductor processing solution such as an etchant for silicon, a sufficient etching rate can be maintained and surface roughness caused by etching can be suppressed, which is therefore preferred.

[0063] The substrate used in silicon etching can be any of monocrystalline, polycrystalline, or amorphous, and there are no particular restrictions on the etching method. As an example of an etching method, an alkaline aqueous solution for semiconductors contains quaternary ammonium ions as shown in formula (1) above, and etching can be performed by immersing the silicon substrate therein for a specified time, for example, 3 to 30 minutes, preferably 5 to 15 minutes. As for the temperature of the etching method, for example, 25 to 90°C, preferably 30 to 80°C, can be listed.

[0064] The mass fraction of halide ions in alkaline aqueous solutions for semiconductors can be analyzed using ion chromatography, especially at high concentrations, where analysis based on neutralization is effective. Specifically, before introducing the alkaline aqueous solution for semiconductors into an anion chromatograph, the cations in the alkaline solution are exchanged with hydrogen ions to convert hydroxide ions into water. This removes hydroxide ions. Furthermore, concentration improves sensitivity. Using this method, the determination of low-concentration halide ion concentrations can be achieved. Details are described below.

[0065] The alkaline aqueous solution for semiconductors contains hydroxide ions. The alkaline aqueous solution for semiconductors containing quaternary ammonium ions and hydroxide ions as shown in formula (1) above can also be described as containing quaternary ammonium hydroxide containing quaternary ammonium ions as shown in formula (1) above and containing hydroxide ions. By containing quaternary ammonium hydroxide, it can be used as a processing solution in semiconductor manufacturing.

[0066] The concentrations of quaternary ammonium ions and hydroxide ions shown in formula (1) above in the alkaline aqueous solution for semiconductors are not particularly limited, but it is preferable to manufacture quaternary ammonium hydroxide at a concentration of 1.0 to 65.0% by mass. When used in semiconductor applications, for example, as quaternary ammonium hydroxide, it is more preferable to use it at a concentration of 1.0 to 10.0% by mass, and even more preferable at a concentration of 2.0 to 7.0% by mass. In addition, it is more preferable to use it at a concentration of 1.0 to 3.0% by mass, and particularly preferable at a concentration of 2.38% by mass.

[0067] Furthermore, as a quaternary ammonium hydroxide, it is preferably used at a molar concentration of 0.10 to 0.50 mol / L, and more preferably at a molar concentration of 0.15 to 0.35 mol / L.

[0068] Furthermore, high-concentration quaternary ammonium hydroxide can be diluted for use. By producing a high concentration, the volume required for transportation can be reduced, thus minimizing transport costs. Additionally, even if contamination occurs during the filling of containers with alkaline aqueous solutions for semiconductors or during transportation, dilution can correspondingly reduce the impact of contamination compared to undiluted cases. The preferred concentration of high-concentration quaternary ammonium hydroxide is 10.0 to 50.0% by mass, more preferably 20.0 to 40.0% by mass. The concentration of quaternary ammonium hydroxide can be determined by acid-based neutralization titration or the like.

[0069] Furthermore, the concentration of quaternary ammonium ions represented by formula (1) in the alkaline aqueous solution for semiconductors is preferably set to 0.8 to 61.7% by mass. More preferably, it is set to 0.8 to 9.5% by mass, and even more preferably, it is set to 1.2 to 6.7% by mass. Additionally, the concentration of quaternary ammonium ions in the high-concentration quaternary ammonium hydroxide before dilution is preferably set to 8.0 to 47.5% by mass, and more preferably, it is set to 16.0 to 38.0% by mass.

[0070] Furthermore, the concentration of hydroxide ions in the alkaline aqueous solution for semiconductors is preferably set to 0.05 to 10.6% by mass. More preferably, it is set to 0.05 to 1.6% by mass, and even more preferably, it is set to 0.1 to 1.2% by mass. Additionally, the concentration of hydroxide ions in the high-concentration quaternary ammonium hydroxide is preferably set to 0.5 to 8.0% by mass, and more preferably, it is set to 1.0 to 6.4% by mass.

[0071] The alkaline aqueous solution for semiconductors contains water. The form of water is not particularly limited, and any known type of water can be used; however, ultrapure water with reduced metal impurities is particularly preferred. Furthermore, the water content in the alkaline aqueous solution for semiconductors is not particularly limited, but is preferably 90.0 to 99.0% by mass, more preferably 93.0 to 98.0% by mass, and even more preferably 97.0 to 98.0% by mass.

[0072] Furthermore, the alkaline aqueous solution for semiconductors may contain one or more compounds selected from the group consisting of alcohols and amines. The concentration of one or more compounds selected from the group consisting of alcohols and amines in the alkaline aqueous solution for semiconductors is not particularly limited, but is preferably 0.1 to 10,000 ppm by mass, more preferably 0.1 to 100 ppm by mass.

[0073] There are no particular limitations on the alcohol used; any known alcohol 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. Furthermore, there are no particular limitations on the functionality of the alcohol; monohydric alcohols or alcohols with two or more carbon atoms can be used. However, from the viewpoint that a long chain could potentially cause adsorption obstacles during semiconductor processing, alcohols with 16 or fewer carbon atoms (more preferably 2 to 8, and even more preferably 2 to 4) are preferred.

[0074] The amine is not particularly limited and can be any known amine. Examples include primary amines such as methylamine, secondary amines such as dimethylamine, and tertiary amines such as trimethylamine. Furthermore, the functionality of the amine is not particularly limited; monoamines or amines with two or more carbon atoms can be used. However, from the viewpoint that a long chain could potentially cause adsorption obstacles during semiconductor processing, amines with 16 or fewer carbon atoms (more preferably 2 to 8, and even more preferably 2 to 4) are preferred.

[0075] Furthermore, the alkaline aqueous solution for semiconductors may contain a surfactant. Preferably, the concentration of the surfactant in the aforementioned alkaline aqueous solution for semiconductors is less than 100 ppm by mass. Alternatively, the aforementioned semiconductor processing solution may not contain a surfactant.

[0076] The quaternary ammonium ions represented by formula (1) contained in the above-mentioned alkaline aqueous solution for semiconductors have an asymmetric shape centered on the nitrogen atom, and R 1 R 2 R 3 and R 4 The alkyl group in the above formula (1) has 2 to 16 carbon atoms, and is therefore considered to be able to act as a surfactant. Specifically, the part with the longer number of carbon atoms in the alkyl group is lipophilic, and the part with the shorter number of carbon atoms is hydrophilic. Therefore, it is believed that the quaternary ammonium ion shown in the above formula (1) has both lipophilic and hydrophilic parts in its ionic structure and acts as a surfactant. Therefore, the alkaline aqueous solution for semiconductors can be completely free of surfactants, or if it is contained, its concentration can be as low as less than 100 ppm by mass. The concentration of the surfactant is more preferably less than 50 ppm by mass, more preferably less than 30 ppm by mass, and particularly preferably less than 10 ppm by mass. By not containing the surfactant contained in the alkaline aqueous solution for semiconductors, or even if it contains the surfactant, its concentration is less than 100 ppm by mass, foaming of the alkaline aqueous solution for semiconductors or impurities from the surfactant can be suppressed, for example. Furthermore, when quaternary ammonium hydroxide is recovered from used alkaline aqueous solutions for semiconductors through separation, purification, etc., and then reused, a surfactant must be added again if a surfactant is required for the alkaline aqueous solution for semiconductors. However, if a surfactant is not required, the recovered liquid can be used directly as an alkaline aqueous solution for semiconductors. Moreover, if the surfactant concentration is low, the amount of surfactant to be added again can be suppressed, which is therefore preferable. There is no particular lower limit for the surfactant concentration, but to demonstrate its effect, it is desirable to contain 0.01 ppm by mass or more, preferably 0.1 ppm by mass or more.

[0077] As a surfactant, it is a compound having both a hydrophilic group and a hydrophobic group (lipophilic group) in one molecule, such as nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0078] It should be noted that surfactants are different from the compounds containing quaternary ammonium ions that may be contained in alkaline aqueous solutions for semiconductors.

[0079] For toxicity evaluation of alkaline aqueous solutions used in semiconductors, in the OECD-based acute oral toxicity test on rats using TG420, the median lethal dose (LD50), calculated as 100% by mass of quaternary ammonium hydroxide, is preferably greater than 50 mg / kg. This further improves safety during use. Furthermore, in the GHS classification, an LD50 value of 50 mg / kg or less corresponds to Category 2, with stricter restrictions during storage and transportation; and a value of 5 mg / kg or less corresponds to Category 1, becoming even more stringent. Therefore, an LD50 value greater than 50 mg / kg is preferred. There is no particular upper limit to the LD50 value, but a value greater than 50 mg / kg and less than 10,000 mg / kg is more preferred, and a value greater than 300 mg / kg and less than 10,000 mg / kg is even more preferred.

[0080] The LD50 value can be adjusted by changing the type of quaternary ammonium ion shown in the above formula (1).

[0081] As for the toxicity evaluation of alkaline aqueous solutions for semiconductors, in the OECD TG202 daphnia acute activity inhibition test, the half-maximal effective concentration (EC50) value, calculated as 100% by mass of quaternary ammonium hydroxide, is preferably greater than 3 mg / L. This makes it easier to achieve a low environmental impact. Furthermore, since the EC50 value of TMAH, which is highly toxic and easily causes environmental impact, is 3 mg / L, it is preferable to exceed 3 mg / L from the viewpoint of reducing environmental impact. There is no particular upper limit to the EC50 value, but it is more preferable to exceed 3 mg / L and be less than 1000 mg / L, and even more preferably to exceed 10 mg / L and be less than 1000 mg / L.

[0082] The EC50 value can be adjusted by changing the type of quaternary ammonium ion shown in equation (1) above.

[0083] Based on the toxicity findings obtained in the aforementioned OECD TG420 acute oral toxicity test and TG202 daphnia acute activity inhibition test, it is preferable, for example, to use R in the above formula (1). 1 R 2 and R 3 Alkyl groups with 1 carbon atom, R 4 R is a quaternary ammonium ion of an alkyl group having 2 to 4 carbon atoms. 1 R 2 R 3 and R 4 R is a quaternary ammonium ion of an alkyl group with 2 carbon atoms. 1 R 2 R 3 and R 4 R is a quaternary ammonium ion of an alkyl group with 3 carbon atoms. 1 R 2 R3 and R 4 Quaternary ammonium ions, such as alkyl groups having 4 carbon atoms, are preferred. More specifically, ethyltrimethylammonium ions, propyltrimethylammonium ions, butyltrimethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, and tetrabutylammonium ions are preferred.

[0084] The alkaline aqueous solution for semiconductors can be used, for example, as a processing solution in semiconductor manufacturing, such as an etching solution, cleaning solution, or developing solution. That is, the alkaline aqueous solution of the present invention can be used to manufacture semiconductors.

[0085] Furthermore, the alkaline aqueous solution for semiconductors can be used as a low-toxicity alkaline aqueous solution for semiconductors. That is, one aspect of the present invention is a method of using the alkaline aqueous solution for semiconductors of the present invention as a low-toxicity alkaline aqueous solution for semiconductors.

[0086] Furthermore, as another aspect of the alkaline aqueous solution for semiconductors according to the present invention, it can be used as a component of a chemical mechanical polishing (CMP) composition (polishing composition). Conventionally used inorganic bases such as sodium hydroxide and potassium hydroxide raise concerns about metal ion contamination during use. On the other hand, tetramethylammonium hydroxide (TMAH), an organic base, is highly toxic, thus requiring strict restrictions on its storage and transportation, and posing a significant environmental burden in terms of waste liquid disposal after use. In contrast, the alkaline aqueous solution for semiconductors of the present invention is low in toxicity, therefore, the aforementioned problems are less likely to occur when preparing and using the polishing composition using it.

[0087] The grinding composition of this embodiment contains the above-mentioned alkaline aqueous solution for semiconductors and abrasive grains.

[0088] The conditions of the above-described alkaline aqueous solution for semiconductors used in the grinding composition of this embodiment can be directly applied as described above. As the quaternary ammonium ion represented by formula (1) above, a quaternary ammonium ion having two alkyl groups is preferred. In this manner, R in formula (1) 1 R 2 R 3 and R 4 When any three of the alkyl groups are methyl groups and the remaining alkyl group has 2 to 16 carbon atoms, a low-toxicity grinding composition can be prepared, resulting in a good grinding speed and a good appearance after grinding. More preferably, the remaining alkyl group is a quaternary ammonium ion with 2 to 8 carbon atoms; even more preferably, it is a quaternary ammonium ion with 2, 3, or 4 carbon atoms; and most preferably, it is a quaternary ammonium ion with 3 or 4 carbon atoms. Alternatively, two or more quaternary ammonium ions of formula (1) can be used in combination. Preferred combinations include: a combination of ethyltrimethylammonium ion and propyltrimethylammonium ion, and a combination of ethyltrimethylammonium ion and butyltrimethylammonium ion. Other quaternary ammonium ions of formula (1) can also be further combined in these combinations.

[0089] The mass fraction of the hydroxide containing quaternary ammonium ions in the alkaline aqueous solution for semiconductors used in the grinding composition of this embodiment is not particularly limited. In the grinding composition, it is preferable to adjust the concentration and / or mixing amount of the alkaline aqueous solution for semiconductors so that the hydroxide containing quaternary ammonium ions shown in the above formula (1) is usually 0.0001 to 15 parts by mass, preferably 0.005 to 10 parts by mass, and more preferably 0.01 to 5 parts by mass.

[0090] The mass fraction of halide ions contained in the alkaline aqueous solution for semiconductors used in the grinding composition of this embodiment is not particularly limited. The mass fraction of hydroxide ions is 0.0000001 to 0.01 parts by mass relative to 1 part by mass, more preferably 0.0000001 to 0.001 parts by mass, and even more preferably 0.0000001 to 0.0005 parts by mass, which can also reduce contamination of the workpiece during CMP processing.

[0091] The pH (25°C) range of the polishing composition can be appropriately selected according to its intended use and is not limited. For example, in the polishing of silicon wafers, it can generally be used at 8 to 12, preferably 9 to 11. For example, the pH of polishing slurry compositions containing oxidants can generally be used at 1 to 8, preferably 2 to 7.

[0092] The grinding composition of this embodiment includes abrasive grains. Examples of abrasive grains suitable for use in water-based grinding compositions include inorganic particles, organic particles, and organic-inorganic composite particles. Examples of inorganic particles include silica, alumina, cerium oxide, titanium oxide, silicon nitride, and zirconium oxide. Among these, fumed silica and colloidal silica can be used as silica. Examples of organic particles include styrene copolymers, (meth)acrylic copolymers, and polyimide copolymers. These abrasive grains can be made from known materials. The average particle size of the abrasive grains can be appropriately selected according to the application and is not particularly limited. For example, the average primary particle size can be, for example, 10-50 nm, preferably 20-40 nm. The average primary particle size of the abrasive grains can be, for example, determined by the specific surface area S (m²) based on the BET method. 2 The average primary particle size (nm) is calculated using the formula 2727 / S. The specific surface area of ​​the abrasive particles can be measured, for example, using a surface area measuring device manufactured by Micromeritics, trade name "Flow Sorb II 2300". The average secondary particle size of the abrasive particles can be, for example, 10~200 nm, preferably 20~150 nm. The average secondary particle size of the abrasive particles can be determined, for example, using the dynamic light scattering method of model "UPA-UT151" manufactured by Nikkiso Co., Ltd., to determine the volume average particle size.

[0093] The amount of abrasive particles in the grinding composition of this embodiment is not particularly limited, for example, it is 0.01 to 20% by mass relative to the grinding composition, preferably 0.03 to 15% by mass, and more preferably 0.05 to 10% by mass.

[0094] The grinding composition of this embodiment may contain oxidizing agents, chelating agents, surfactants, water-soluble compounds, etc., as needed.

[0095] Examples of oxidizing agents include hydrogen peroxide, peracetic acid, perbenzoic acid, perchloric acid, organic peroxides, nitrate compounds, persulfates, cerium ammonium nitrate, and salts of polyvalent metals, as well as heteropoly acids such as silicotungstic acid and silicomolic acid. These can be used alone or in combination with two or more agents. When the grinding composition of this embodiment contains an oxidizing agent, the amount of oxidizing agent in the grinding composition is not particularly limited, for example, it is 0.001 to 50% by mass relative to the grinding composition, preferably 0.01 to 30% by mass, and more preferably 0.05 to 25% by mass.

[0096] Examples of chelating agents include aminocarboxylic acid chelating agents and phosphonic acid chelating agents.

[0097] Surfactants can include the nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, etc., mentioned above, and can be used alone or in combination of two or more. When the grinding composition of this embodiment contains an oxidant, the amount of chelating agent in the grinding composition is not particularly limited, for example, it is 0.0001 to 1% by mass relative to the grinding composition, preferably 0.001 to 0.5% by mass, and more preferably 0.005 to 0.1% by mass.

[0098] Examples of water-soluble compounds include hydroxyethyl cellulose, carboxymethyl cellulose, glycerol, polyglycerol, polyvinyl alcohol, and polyethylene glycol. These can be used alone or in combination of two or more. When the grinding composition of this embodiment contains a water-soluble compound, the amount of the water-soluble compound in the grinding composition is not particularly limited. For example, it is 0.001 to 10% by mass relative to the grinding composition, preferably 0.003 to 3% by mass, and more preferably 0.005 to 0.5% by mass.

[0099] The polishing composition of this embodiment comprises the above-mentioned alkaline aqueous solution for semiconductors and abrasive grains. In the polishing composition, the remainder, excluding the abrasive grains, the above-mentioned components, and any other additives, is the above-mentioned alkaline aqueous solution for semiconductors. The polishing composition of this embodiment can be used directly, or it can be used after being diluted with water in a temporarily prepared form.

[0100] There are no particular limitations on the wafers from which the polishing composition of this embodiment can be applied, and examples include silicon wafers, SiC wafers, GaN wafers, GaAs wafers, GaP wafers, glass wafers, aluminum wafers, and sapphire wafers.

[0101] The method for manufacturing alkaline aqueous solutions for semiconductors is not particularly limited. From the viewpoint of suppressing halide ion concentration, it is preferable to obtain them by electrolysis of a quaternary ammonium halide aqueous solution. That is, it is preferable to include an electrolysis step that electrolyzes the quaternary ammonium halide aqueous solution. Specifically, it is preferable to include an electrolysis step that electrolyzes the quaternary ammonium halide aqueous solution containing (A), (B), and (D) below. (A), (B), and (D) can be the substances described above.

[0102] (A) The quaternary ammonium ion represented by the following formula (1)

[0103] (B) Halide ions

[0104] (D) Water

[0105]

[0106] (where R) 1 R 2 R 3 and R 4 Each is independently an alkyl group having 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4), wherein R 1 R 2 R 3 and R 4 In this embodiment, the number of carbon atoms in one or more alkyl groups is 2 to 16 (preferably 2 to 8, more preferably 2 to 4).

[0107] An electrolytic cell can be used to manufacture alkaline aqueous solutions for semiconductors. This cell has one or more cation exchange membranes disposed between the anode and cathode, and includes a feed chamber for supplying a quaternary ammonium halide aqueous solution as raw material and an alkaline chamber (cathode chamber) for generating an aqueous solution of quaternary ammonium hydroxide. In the manufacturing method using this electrolytic cell, during electrolysis, quaternary ammonium ions contained in the quaternary ammonium halide aqueous solution pass through the cation exchange membrane disposed on the cathode side. This generates an aqueous solution of quaternary ammonium hydroxide in the alkaline chamber.

[0108] The above example is an example of configuring more than one cation exchange membrane, but as long as an aqueous solution of quaternary ammonium hydroxide can be generated, an electrolyzer with multiple membranes selected from the group consisting of cation exchange membranes, anion exchange membranes and bipolar membranes (composite membranes composed of cation exchange membranes and anion exchange membranes) can be used.

[0109] At this point, the halide ions, which are anions of quaternary ammonium halides, move towards the anode side, but some halide ions also move towards the cathode side due to diffusion. Therefore, although it also depends on the concentration of the liquid used in the feedstock, it is still possible for about 1 to tens of ppm of halide ions to be mixed into the aqueous solution of quaternary ammonium hydroxide.

[0110] The method for manufacturing alkaline aqueous solutions for semiconductors may include a preparation step of preparing an aqueous solution of quaternary ammonium halide, which will be used as a raw material in the electrolysis process, prior to the electrolysis process described above.

[0111] The preparation process is not particularly limited; for example, it can be prepared by manufacturing an aqueous solution of a quaternary ammonium halide. Furthermore, the method for manufacturing the aqueous solution of the quaternary ammonium halide is not particularly limited. For example, from the viewpoint of productivity and quality, the process of reacting a trialkylamine with a haloalkane in ultrapure water to obtain the quaternary ammonium halide is preferred.

[0112] The trialkylamine and haloalkane used as raw materials are not particularly limited as long as the quaternary ammonium ion shown in the above formula (1) can be obtained. Specifically, substances in which one or more of the alkyl groups contained in the trialkylamine and the alkyl groups contained in the haloalkane are alkyl groups with 2 to 16 carbon atoms (preferably 2 to 8, more preferably 2 to 4), and the other alkyl groups are alkyl groups with 1 to 16 carbon atoms (preferably 1 to 8, more preferably 1 to 4).

[0113] In addition, the halide ion that serves as the anion of the haloalkane can be the same ion as described in (B) above.

[0114] Impurities contained in quaternary ammonium halides can diffuse and mix into the aqueous solution of quaternary ammonium hydroxide; therefore, high-purity quaternary ammonium halides are preferred. Specifically, the concentration of alcohol in the aqueous solution of quaternary ammonium halide is preferably 0.1 to 10,000 ppm by mass, and the concentration of amine is preferably 0.1 to 10,000 ppm by mass.

[0115] Example

[0116] The following embodiments are shown to illustrate the present invention in detail, but the present invention is not limited to these embodiments. It should be noted that the evaluation of the implementation in the embodiments and comparative examples was obtained by the following methods.

[0117] (Examples 1-13, Comparative Example 1)

[0118] [Alkaline aqueous solution for semiconductors]

[0119] The aqueous solution of quaternary ammonium hydroxide was prepared to the concentrations shown in Table 1, and various evaluations were performed.

[0120] • Ethyltrimethylammonium hydroxide (ETMAH, made from raw materials)

[0121] • Diethyldimethylammonium hydroxide (DEDMAH, manufactured by Sigma-Aldrich)

[0122] • Propyltrimethylammonium hydroxide (PTMAH, made from raw materials)

[0123] Butyltrimethylammonium hydroxide (BTMAH, produced from raw materials)

[0124] Tetraethylammonium hydroxide (TEAH, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0125] Tetrapropylammonium hydroxide (TPAH, manufactured by Tokyo Chemical Industry)

[0126] Tetrabutylammonium hydroxide (TBAH, manufactured by Tokyo Chemical Industry Co., Ltd.)

[0127] • Hexadecyltrimethylammonium hydroxide (HTMAH, manufactured by Tokyo Chemical Industry)

[0128] Tetramethylammonium hydroxide (TMAH, manufactured by TOKUYAMA CORPORATION)

[0129] [surfactant]

[0130] Surfynol 465 (registered trademark) (manufactured by Nissin Chemical Co., Ltd.)

[0131] Preparation of Quaternary Ammonium Hydroxide Aqueous Solution

[0132] ETMAH, PTMAH, and BTMAH are prepared according to the following steps. A quaternary ammonium halide aqueous solution is prepared from trialkylamine and haloalkanes as raw materials, and then used as a raw material to produce a quaternary ammonium hydroxide aqueous solution by electrolysis. Specifically, in the case of ETMAH, trimethylamine and chloroethane are added in a 1:1 molar ratio to a reaction vessel containing ultrapure water, and the reaction is maintained at 60°C to prepare a 50% (w / w) ethyltrimethylammonium chloride aqueous solution. The solution is then subjected to reduced pressure until the unreacted trimethylamine and chloroethane, and the byproduct ethanol, are each below 100 ppm. Figure 1 The electrolytic cell shown is used to fabricate ETMAH. Figure 1 In the diagram, 1 represents the anode, 2 represents the cathode, 3 represents the power source, 4 represents the anode chamber, 5 represents the raw material chamber, 6 represents the intermediate chamber, 7 represents the cathode chamber, 8 represents the anion exchange membrane, and 9 represents the cation exchange membrane.

[0133] The cathode uses a platinum-plated nickel plate, the anode uses a platinum-plated titanium plate, the cation exchange membrane uses two Nafion N324 membranes (manufactured by Chemours), and the anion exchange membrane uses ASE (manufactured by Astom). Specifically, 0.5 equivalence (N) hydrochloric acid is circulated in the anode chamber, 50% (w / w) ethyltrimethylammonium chloride aqueous solution is circulated in the feed chamber between the anion exchange membrane and the cation exchange membrane on the cathode side, and ultrapure water is circulated in the intermediate chamber between the cathode chamber and the two cation exchange membranes. The current density is gradually increased and eventually maintained at 30 A / dm³. 2 Electrolysis was continuously performed simultaneously at a current density of 40°C and a temperature of 40°C. During electrolysis, an aqueous solution of ethyltrimethylammonium chloride (ETMAH) was added to maintain the ETMAH concentration in the feed chamber at above 40% by mass. Electrolysis was terminated when the ETMAH concentration in the cathode chamber reached 30% by mass, yielding an ETMAH aqueous solution. This ETMAH aqueous solution was diluted with ultrapure water and used in Examples 1, 2, 12, and 13 at the concentrations listed in Table 1.

[0134] For the preparation of PTMAH and BTMAH, chloropropane and chlorobutane are used as alkyl halides, respectively. Otherwise, the preparation is carried out in the same manner as that of ETMAH.

[0135] In addition, for ETMAH in Example 3, Figure 1 The number of cation exchange membranes was reduced from two to one, and an electrolyzer without an intermediate chamber was used. Otherwise, the preparation of the ETMAH used in Examples 1, 2, 12, 13, and 14 was carried out in the same manner to obtain the ETMAH used in Example 3. Additionally, the surfactants listed in Table 1 were added to Examples 14-16 and Comparative Example 2.

[0136] Furthermore, the concentrations of amines in the alkaline aqueous solutions of Examples 1-16 and Comparative Examples 1 and 2 were all below 100 ppm by mass. Moreover, the concentrations of alcohols in the alkaline aqueous solutions of Examples 1-16 and Comparative Examples 1 and 2 were all below 100 ppm by mass.

[0137] [Evaluation Method]

[0138] 1) Determination of halide ion concentration

[0139] When the concentration of quaternary ammonium hydroxide in the alkaline aqueous solution for semiconductors is below 5% by mass, it can be used directly. When the concentration exceeds 5% by mass, it should first be diluted to 5% by mass with ultrapure water before being passed into an OnGuard Cartridge II H+ type 2.5cc (manufactured by Thermo Fisher Scientific). The liquid is then recovered, and the anion concentration of the recovered liquid is determined by an ion chromatograph (Integrion, manufactured by Thermo Fisher Scientific).

[0140] 2) Hydroxide ion concentration

[0141] For 1 mL of the aqueous solution prepared in the examples and comparative examples, a neutralization titration was performed using a Hiranuma automatic titration apparatus (COM-1700, manufactured by HIRANUMA) with 0.1 mol / L hydrochloric acid. The hydroxide ion concentration of the alkaline aqueous solution for semiconductors was determined based on the volume of 0.1 mol / L hydrochloric acid required for neutralization.

[0142] 3) Acute oral toxicity

[0143] Data on median lethal dose (LD50) were collected in toxicity studies using rats. For samples with unpublished data, an OECD-based acute oral toxicity study of TG420 was conducted to obtain data.

[0144] The obtained median lethal dose (LD50) was converted to 100% by mass of quaternary ammonium hydroxide aqueous solution and evaluated based on the following criteria. When mixing two or more quaternary ammonium hydroxide aqueous solutions, the LD50 was calculated by multiplying the mixing ratio by the LD50 of each quaternary ammonium hydroxide aqueous solution and summing the results. The results are shown in Table 1.

[0145] A: The median lethal dose exceeds 300 mg / kg

[0146] B: Median lethal dose (LD50) exceeding 50 mg / kg but below 300 mg / kg

[0147] C: The median lethal dose is below 50 mg / kg.

[0148] As a low-toxicity alkaline aqueous solution for semiconductors, it is preferably evaluated as A to B, and more preferably as A.

[0149] 4) Ecotoxicity (acute)

[0150] Data on the half-maximal effective concentration (EC50) of daphnia in the acute activity inhibition test were collected. For samples with unpublished data, toxicity tests based on the OECD TG202 daphnia acute activity inhibition test were performed to obtain data.

[0151] The obtained median lethal dose (LD50) was converted to 100% by mass of quaternary ammonium hydroxide aqueous solution and evaluated based on the following criteria. When mixing two or more quaternary ammonium hydroxide aqueous solutions, the LD50 was calculated by multiplying the mixing ratio by the LD50 of each quaternary ammonium hydroxide aqueous solution and summing the results. The results are shown in Table 1.

[0152] A: The half-maximal effective concentration exceeds 10 mg / L

[0153] B: The half-maximal effective concentration is greater than 3 mg / L but less than 10 mg / L

[0154] C: The half-maximal effective concentration is below 3 mg / L.

[0155] If the evaluation is A to B, it can be described as a low-toxicity alkaline aqueous solution for semiconductors, with evaluation A being preferred.

[0156] Furthermore, even if the ecotoxicity is C, if the acute oral toxicity is rated A to B, it can still be evaluated as low toxicity.

[0157] 5) Development test

[0158] Prepare a 4-inch silicon wafer and clean its surface with a sulfuric acid-hydrogen peroxide solution (volume ratio 4:1). Then, bake it on a hot plate at 200°C for 60 seconds. Next, using a spin coater, apply a positive photoresist to the silicon wafer to obtain a positive photoresist film with a thickness of 3.5 μm. Then, irradiate these photoresist films with g, h, and i rays at wavelengths of 300–500 μm through a mask pattern, followed by the addition of various alkaline aqueous solutions for semiconductors. Set the development time to 8 or 12 minutes, allow it to stand at 23°C, rinse with ultrapure water, and dry to obtain a 20 μm contact hole pattern.

[0159] The presence of scum and the shape of the obtained corrosion-resistant patterns were confirmed by SEM, and the results were evaluated based on the following criteria. The results are shown in Table 2.

[0160] A: No scum was produced at development times of 8 minutes and 12 minutes, and the sidewalls of the recessed areas of the pattern remained upright.

[0161] B: At a development time of 8 minutes, scum was observed in a portion of the recesses, but no scum was observed at a development time of 12 minutes, and the sidewalls of the recesses in the pattern remained upright.

[0162] C: Scum formation and / or non-vertical sidewalls of the recessed areas of the pattern occurred at both 8-minute and 12-minute development times.

[0163] As a developer for semiconductors, an A rating is preferred, but even a B rating can be used under appropriate conditions.

[0164] 6) Etching test

[0165] Prepare 100 mL of an alkaline aqueous solution for semiconductors, heat it to 40 °C, and then immerse a 2 × 2 cm single-crystal silicon substrate (silicon 100 facet) in the solution for 10 minutes. Calculate the etching amount based on the mass change before and after etching, and divide it by the etching time to determine the silicon etching rate.

[0166] The obtained etching rates were evaluated based on the following criteria. The results are shown in Table 1.

[0167] A: Etching rate is above 50 nm / min

[0168] B: Etching rate is above 10 nm / min and below 50 nm / min

[0169] C: Etching rate is above 1 nm / min and below 10 nm / min

[0170] D: Etching rate is less than 1 nm / min

[0171] If the etchant is rated A to C, it can be used as an etchant for semiconductors, preferably rated A to B, and more preferably rated A.

[0172] In addition, the surface of the etched silicon substrate was observed using a field emission scanning electron microscope (JSM-7800F Prime, manufactured by Nippon Electron Ltd.) to confirm the presence or absence of surface roughness, and was evaluated according to the following criteria. The surface roughness was ranked from least to most rough as A to D, and evaluations A to C were all acceptable levels. Evaluations A to B were preferred, and evaluation A was more preferred.

[0173] A: No surface roughness was observed.

[0174] B: Some surface roughness was observed (surface roughness is less than 30% of the total surface roughness).

[0175] C: The surface is generally rough (the surface roughness is 30-100% of the overall surface roughness).

[0176] D: The surface is generally rough, and the roughness is deep (with bumps and depressions greater than 1×1μm).

[0177] [Table 1]

[0178]

[0179] [Table 2]

[0180]

[0181] <Preparation of Grinding Compositions>

[0182] Colloidal silica (primary particle size 35 nm, secondary particle size 70 nm) used as abrasive particles was mixed and dispersed with water in advance using a mixer to prepare a slurry with a colloidal silica concentration of 4% by mass. 50 parts by mass of this slurry, 40 parts by mass of ultrapure water, and 10 parts by mass of an alkaline aqueous solution of the quaternary ammonium hydroxide compound shown in Table 3 (7.5 parts by mass in Examples 20 and 21, respectively) were mixed to prepare a grinding composition with the composition shown in Table 3.

[0183] (Grinding)

[0184] Grind a 4-inch p-type low-resistivity silicon substrate (100 sides) under the following conditions.

[0185] (Grinding conditions)

[0186] Grinding machine: Engis EJ-380IN

[0187] Grinding pressure: 100gf / cm 2

[0188] Grinding pad: SUBA-800 NITTA HAAS

[0189] Rotation speed: 100 rpm

[0190] Feed rate of the grinding composition: 200 ml / min

[0191] Grinding time: 20 minutes

[0192] In the evaluation of the characteristics of the surface being ground, the quality before and after grinding is measured, and the grinding speed is calculated using the following formula.

[0193] Grinding speed = (Substrate mass before grinding - Substrate mass after grinding) ÷ Grinding area of ​​substrate ÷ Density ÷ Grinding time

[0194] [Table 3]

[0195]

[0196] Appearance Confirmation: Evaluation Results Based on Surface Projection Observation

[0197] ○: Confirmed as good.

[0198] △: A few grinding marks can be seen during the inspection.

[0199] ×: Clear abrasive damage can be confirmed.

[0200] When performing CMP processing on silicon substrates using the grinding composition of the alkaline aqueous solution for semiconductors utilizing the present invention, a practical grinding speed is achieved, and the halide ion concentration is low, minimizing concerns about contamination of the workpiece. TMAH, as shown in Experimental Example 23, has high toxicity, posing handling problems. Furthermore, among low-toxicity quaternary ammonium ions, substances with quaternary ammonium structures that differ only in a portion of their structure achieve good grinding speeds.

[0201] Explanation of reference numerals in the attached figures

[0202] 1: Anode

[0203] 2: Cathode

[0204] 3: Power supply

[0205] 4: Anode Chamber

[0206] 5: Raw Material Room

[0207] 6: Intermediate Room

[0208] 7: Cathode Chamber

[0209] 8: Anion exchange membrane

[0210] 9: Cation exchange membrane

Claims

1. An alkaline aqueous solution for semiconductors, comprising the following (A) to (D): (A) The quaternary ammonium ion shown in formula (1) below, (B) Halogen ions, (C) hydroxide ions, (D) Water, In equation (1), R 1 R 2 R 3 and R 4 Each is an alkyl group having 1 to 16 carbon atoms, wherein, R 1 R 2 R 3 and R 4 In this context, the number of carbon atoms in one or more alkyl groups is 2 to 16.

2. The alkaline aqueous solution for semiconductors according to claim 1, wherein, R in equation (1) 1 R 2 R 3 and R 4 Not all of them are the same alkyl group.

3. The alkaline aqueous solution for semiconductors according to claim 1 or 2, wherein, R in equation (1) 1 R 2 and R 3 For methyl, R in formula (1) 4 It is an alkyl group with 2 to 16 carbon atoms.

4. The alkaline aqueous solution for semiconductors according to any one of claims 1 to 3, wherein, The (B) halide ion is a chloride ion or a bromide ion.

5. The alkaline aqueous solution for semiconductors according to any one of claims 1 to 4, wherein, When the mass of hydroxide ions in the alkaline aqueous solution for semiconductors is set to 1 part by mass, the mass of halide ions is 0.0000001 to 0.01 parts by mass.

6. The alkaline aqueous solution for semiconductors according to any one of claims 1 to 5, wherein, In an OECD-based acute oral toxicity test of TG420 using rats, the LD50 value, calculated with the hydroxide of the quaternary ammonium ion as 100% by mass, exceeded 50 mg / kg.

7. The alkaline aqueous solution for semiconductors according to any one of claims 1 to 6, wherein, In the OECD's TG202 acute activity inhibition test for daphnia, the EC50 value, calculated with the hydroxide of the quaternary ammonium ion as 100% by mass, exceeded 3 mg / L.

8. The alkaline aqueous solution for semiconductors 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. The alkaline aqueous solution for semiconductors according to any one of claims 1 to 8, further comprising a surfactant, wherein the concentration of the surfactant in the alkaline aqueous solution for semiconductors is less than 100 ppm by mass.

10. A polishing composition comprising an alkaline aqueous solution for semiconductors and abrasive grains as described in any one of claims 1 to 9.

11. A method for using the alkaline aqueous solution for semiconductors according to any one of claims 1 to 9 as a low-toxicity alkaline aqueous solution for semiconductors.

12. A method for manufacturing an alkaline aqueous solution for semiconductors according to any one of claims 1 to 7, comprising an electrolysis step of electrolyzing an aqueous solution of a quaternary ammonium halide containing (A), (B), and (D) below. (A) The quaternary ammonium ion shown in formula (1) below, (B) Halogen ions, (D) Water, In equation (1), R 1 R 2 R 3 and R 4 Each is an alkyl group having 1 to 16 carbon atoms, wherein, R 1 R 2 R 3 and R 4 In this context, the number of carbon atoms in one or more alkyl groups is 2 to 16.

13. The method for manufacturing an alkaline aqueous solution for semiconductors according to claim 12, wherein, Prior to the electrolysis process, a preparation step is included to prepare the quaternary ammonium halide aqueous solution. The preparation step is a process of reacting trialkylamine with haloalkanes in ultrapure water to obtain the aqueous solution of the quaternary ammonium halide.

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