JP7482621B2 - Method for producing a quaternary ammonium hydroxide solution in an organic solvent - Google Patents

Description

The present invention relates to a method for producing an organic solvent solution of quaternary ammonium hydroxide, and a method for producing a processing liquid composition for semiconductor manufacturing.

Solutions containing quaternary ammonium hydroxide are used in the manufacturing process of semiconductor devices, liquid crystal display devices, etc. as a developer for photoresist (sometimes simply called "resist"), a stripper and cleaning solution for modified photoresist (e.g. photoresist after an ion implantation process, photoresist after ashing, etc.), a silicon etching solution, etc.

For example, in the photoresist development process, a negative or positive photoresist containing a resin such as novolac resin or polystyrene resin is applied to the surface of a substrate, and the applied photoresist is irradiated with light through a photomask for pattern formation, causing the irradiated photoresist to harden or solubilize, and the unhardened or solubilized photoresist is removed using a developer to form a photoresist pattern.

The photoresist pattern thus formed allows the areas not covered by the photoresist pattern to be selectively processed in subsequent processes (e.g., etching, doping, ion implantation, etc.). The photoresist pattern, which is no longer needed, is then removed from the substrate surface using a resist stripper, after an ashing process if necessary. If necessary, the substrate is further washed with a cleaning solution to remove resist residues.

Traditionally, aqueous solutions of quaternary ammonium hydroxide have been used for these applications. However, when a photoresist pattern undergoes processes such as ion implantation, the photoresist pattern is altered and a carbonaceous crust forms on its surface. Modified photoresist with a crust formed on its surface is not easy to remove with conventional aqueous solutions of quaternary ammonium hydroxide. Furthermore, ashing residues of photoresist patterns also have properties similar to those of carbonaceous materials, and are not easy to remove with conventional aqueous solutions of quaternary ammonium hydroxide.

Therefore, in order to more effectively remove such modified photoresist or photoresist ashing residues, it has been proposed to use an organic solvent solution of quaternary ammonium hydroxide instead of an aqueous solution of quaternary ammonium hydroxide. The organic solvent solution of quaternary ammonium hydroxide is also advantageous in that it is less likely to corrode metal materials used in wiring and inorganic substrate materials such as Si, SiO _x , SiN _x , Al, TiN, W, and Ta, compared to aqueous solutions.

Japanese Patent No. 4673935 Patent No. 4224651 Patent No. 4678673 Patent No. 6165442 International Publication No. 2016/163384 International Publication No. 2017/169832 Brochure

From the viewpoint of enhancing the ability to remove modified photoresist or photoresist ashing residues, and from the viewpoint of compatibility with metal materials and inorganic substrate materials, it is desirable for the water content in the organic solvent solution of quaternary ammonium hydroxide to be low. Also, from the viewpoint of increasing the manufacturing yield of semiconductor devices, it is desirable for the content of metal impurities in the organic solvent solution of quaternary ammonium hydroxide to be low.

However, for example, tetramethylammonium hydroxide (TMAH), a type of quaternary ammonium hydroxide, is commercially available as an aqueous solution with a concentration of 2.38 to 25% by mass, or as a crystalline solid of TMAH pentahydrate (with a purity of about 97 to 98% by mass), but anhydrous TMAH, which is substantially free of water, is not commercially available.

Quaternary ammonium hydroxide is generally produced by electrolyzing an aqueous solution of a quaternary ammonium halide such as tetramethylammonium chloride (TMAC) (electrolysis method). This electrolysis exchanges the halide ions, which are the counterions of the quaternary ammonium ions, for hydroxide ions, producing an aqueous solution of quaternary ammonium hydroxide. For example, the concentration of the TMAH aqueous solution produced by the electrolysis method is usually about 20 to 25 mass %. The electrolysis method makes it possible to produce a high-purity aqueous solution of quaternary ammonium hydroxide with a metal impurity content of approximately 0.1 mass ppm or less for each metal, and in particular, for TMAH, it is possible to produce a high-purity aqueous solution of quaternary ammonium hydroxide with a metal impurity content of 0.001 mass ppm or less (i.e., 1 mass ppb or less) for each metal.

However, it is extremely difficult to obtain anhydrous quaternary ammonium hydroxide from an aqueous solution of quaternary ammonium hydroxide. For example, when the concentration of the aqueous TMAH solution becomes high, a crystalline solid of TMAH pentahydrate (TMAH content: approximately 50% by mass) precipitates. Heating a crystalline solid of TMAH pentahydrate may produce TMAH trihydrate (TMAH content: approximately 63% by mass), but at the same time, the decomposition of TMAH (generation and liberation of trimethylamine) progresses.

The salt exchange method is known as a method for producing an organic solvent solution of quaternary ammonium hydroxide. For example, by mixing tetramethylammonium chloride (TMAC) and potassium hydroxide (KOH) in methanol, TMAH and potassium chloride (KCl) are produced, and KCl, which has low solubility in methanol, precipitates. The precipitated KCl is filtered off to obtain a TMAH-methanol solution. Although the salt exchange method can produce a TMAH-methanol solution with a relatively low water content, the solution contains impurities such as KCl and water at a level of 0.5 to several mass percent. Thus, the salt exchange method cannot produce a high-purity TMAH-methanol solution that is useful in semiconductor manufacturing processes.

As another method for producing a solution of quaternary ammonium hydroxide in an organic solvent, Patent Document 1 describes a method for producing a concentrated solution of quaternary ammonium hydroxide, which is characterized by mixing quaternary ammonium hydroxide in the form of hydrous crystals or an aqueous solution with a water-soluble organic solvent selected from the group consisting of glycol ethers, glycols, and triols to prepare a mixed solution, and subjecting the mixed solution to thin-film distillation under reduced pressure to remove the distillate. Patent Document 1 describes, for example, that a propylene glycol solution of TMAH (TMAH content 12.6% by mass, water content 2.0% by mass) was obtained by thin-film distillation using a 25% by mass aqueous TMAH solution as the starting material.

However, when the present inventors retested the method described in Patent Document 1 using a high-purity aqueous solution of quaternary ammonium hydroxide as the starting material, metal impurities significantly exceeding 0.1 ppm by mass were detected in the organic solvent solution of quaternary ammonium hydroxide obtained by thin-film distillation. From the viewpoint of use in the manufacturing process of semiconductor devices, it is desirable that the metal impurity content in the organic solvent solution of quaternary ammonium hydroxide is at least 0.1 ppm by mass or less for each metal.

As such, a solution of quaternary ammonium hydroxide in an organic solvent with a purity high enough for use in semiconductor manufacturing processes has not yet been obtained.

The present invention aims to provide a method for producing an organic solvent solution of quaternary ammonium hydroxide with a high level of purity useful for semiconductor manufacturing process applications. It also provides a method for producing a processing liquid composition for semiconductor manufacturing.

The present invention includes the following embodiments [1] to [8].
[1] A method for producing a solution of a quaternary ammonium hydroxide in an organic solvent, comprising the steps of:
(a) subjecting the raw material mixture to thin-film distillation using a falling film type thin-film distillation apparatus,
The raw material mixture contains quaternary ammonium hydroxide, water, and a first organic solvent capable of dissolving the quaternary ammonium hydroxide,
the first organic solvent is a water-soluble organic solvent having a plurality of hydroxy groups,
The thin film distillation apparatus comprises:
An evaporation vessel;
a first flow path that introduces the raw material mixture into the evaporation container from an upper portion of the evaporation container;
Equipped with
the raw material mixture introduced into the evaporation vessel from the first flow path flows down along an inner wall surface of the evaporation vessel in the form of a liquid film,
The thin film distillation apparatus further comprises:
a heating surface disposed on the inner wall surface for heating the liquid film flowing down along the inner wall surface;
a condenser disposed inside the evaporation container to cool and liquefy the vapor generated from the liquid film;
a second flow path for recovering the distillate liquefied by the condenser from the evaporation vessel;
a third flow path for recovering from the evaporation container a residual liquid that does not evaporate on the heating surface and flows down from the heating surface;
The thin film distillation
the temperature of the raw material mixture immediately before entering the distillation vessel is a first temperature of 70° C. or less;
the temperature of the heating surface is a second temperature of 60 to 140° C., the second temperature being higher than the first temperature;
A method for producing an organic solvent solution of quaternary ammonium hydroxide, characterized in that the method is carried out under conditions in which the degree of vacuum in the evaporation vessel is 600 Pa or less.

In this specification, the "temperature of the heating surface" of the thin-film distillation apparatus means the temperature of the heat source that heats the liquid film.

[2] The thin film distillation apparatus is
The evaporation container further includes a wiper that is disposed in the evaporation container and rotates along the inner wall surface.
The method for producing an organic solvent solution of quaternary ammonium hydroxide according to [1], characterized in that the raw material mixture introduced into the evaporation container from the first flow path is applied to the inner wall surface by the wiper to form the liquid film.

[3] The method for producing an organic solvent solution of quaternary ammonium hydroxide according to [1] or [2], wherein the first organic solvent is one or more organic solvents selected from dihydric alcohols and trihydric alcohols that are composed of carbon atoms, hydrogen atoms, and oxygen atoms and have a boiling point of 150 to 300°C.

[4] The raw material mixture is, based on the total amount of the mixture,
The first organic solvent is 40 to 85% by mass,
The quaternary ammonium hydroxide is 2.0 to 30% by mass,
The method for producing an organic solvent solution of a quaternary ammonium hydroxide according to any one of [1] to [3], wherein the water is contained in an amount of 10 to 30 mass%.

[5] The contents of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn in the raw material mixture are each 50 ppb or less based on the total amount of the raw material mixture,
The method for producing an organic solvent solution of a quaternary ammonium hydroxide according to any one of [1] to [4], wherein the Cl content in the raw material mixture is 50 ppb or less based on the total amount of the raw material mixture.

[6] A method for producing a processing liquid composition for semiconductor manufacturing, comprising the steps of:
(i) obtaining a solution of quaternary ammonium hydroxide in an organic solvent by the method according to any one of [1] to [5];
(ii) determining the concentration of the quaternary ammonium hydroxide in the organic solvent solution; and (iii) adjusting the concentration of the quaternary ammonium hydroxide in the organic solvent solution by adding to the organic solvent solution an organic solvent having a water content of 1.0 mass% or less, a content of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn of 100 mass% or less, and a content of Cl of 100 mass% or less, based on the total amount of the solvent,
The composition comprises the quaternary ammonium hydroxide and the first organic solvent,
The water content in the composition is 1.0% by mass or less based on the total amount of the composition,
The content of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn in the composition is 100 ppb by mass or less, based on the total amount of the composition;
The method for producing a processing solution composition for semiconductor manufacturing, wherein the Cl content in the composition is 100 ppb by mass or less based on the total amount of the composition.

[7] The method for producing a processing liquid composition for semiconductor manufacturing according to [6], wherein in the step (iii), the content of the quaternary ammonium hydroxide in the organic solvent solution is adjusted to 5.0 mass% or more based on the total amount of the solution.

[8] The method for producing a processing liquid composition for semiconductor manufacturing according to [6], wherein in the step (iii), the content of the quaternary ammonium hydroxide in the organic solvent solution is adjusted to 2.38 to 25.0 mass % based on the total amount of the solution.

The method for producing an organic solvent solution of quaternary ammonium hydroxide according to the first aspect of the present invention makes it possible to produce an organic solvent solution of quaternary ammonium hydroxide having a high level of purity useful for semiconductor manufacturing process applications.

According to the method for producing a processing solution composition for semiconductor manufacturing according to the second aspect of the present invention, it is possible to produce a processing solution composition for semiconductor manufacturing based on a quaternary ammonium hydroxide organic solvent solution, which has a high level of purity useful for semiconductor manufacturing process applications.

FIG. 1 is a diagram illustrating a thin film distillation apparatus 10A according to one embodiment. 2 is a cross-sectional view for explaining the details of an evaporation container 37 in the device 10A. FIG. FIG. 11 is a diagram illustrating a thin film distillation apparatus 10B according to another embodiment. FIG. 10 is a diagram illustrating a thin film distillation apparatus 10C according to another embodiment.

The above-mentioned effects and benefits of the present invention will be made clear from the following description of the embodiment of the invention. Hereinafter, the embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. The drawings do not necessarily reflect accurate dimensions. In addition, some symbols and hatching may be omitted in the drawings. In this specification, unless otherwise specified, the notation "A to B" for numerical values A and B means "A or more and B or less". In such notation, when a unit is added only to numerical value B, the unit is also applied to numerical value A. In addition, the words "or" and "or" mean a logical sum unless otherwise specified. Furthermore, with respect to elements _E1 and _E2 , the expression " _E1 and/or _E2 " means " _E1 or _E2 , or a combination thereof", and with respect to elements _E1 , ..., E _N (N is an integer of 3 or more), the expression " _E1 , ..., E _N-1 , and/or E _N " means " _E1 , ..., E _N-1 , or E _N , or a combination thereof".

<1. Method for producing a solution of quaternary ammonium hydroxide in an organic solvent>
The method for producing an organic solvent solution of a quaternary ammonium hydroxide according to the first aspect of the present invention (hereinafter, may be referred to as a "solution producing method") includes a step (a) of thin-film distilling a raw material mixture using a falling film type thin-film distillation apparatus (hereinafter, may be referred to as "step (a)").

(1.1 Raw Material Mixture)
The raw material mixture contains quaternary ammonium hydroxide (hereinafter sometimes referred to as "QAH"), water, and a first organic solvent that dissolves the quaternary ammonium hydroxide. The first organic solvent is a water-soluble organic solvent having multiple hydroxy groups (hereinafter sometimes referred to as "water-soluble organic solvent").

(1.1.1 Quaternary ammonium hydroxide)
Quaternary ammonium hydroxide is an ionic compound composed of an ammonium cation in which four organic groups are bonded to a nitrogen atom, and a hydroxide ion (anion). The raw material mixture may contain only one type of quaternary ammonium hydroxide, or may contain two or more types of quaternary ammonium hydroxide. An example of the quaternary ammonium hydroxide is a compound represented by the following general formula (1).

一般式（１）において、Ｒ^１～Ｒ^４はそれぞれ独立に、ヒドロキシ基を有していてもよい炭化水素基であり、好ましくはヒドロキシ基を有していてもよいアルキル基である。レジスト及び変性レジストの除去性能及びエッチング性能等の観点からは、Ｒ^１～Ｒ^４は特に好ましくはヒドロキシ基を有していてもよい炭素数１～４のアルキル基である。Ｒ^１～Ｒ^４の具体例としては、メチル基、エチル基、プロピル基、ブチル基、２－ヒドロキシエチル基等を挙げることができる。

In general formula (1), R ¹ to R ⁴ are each independently a hydrocarbon group which may have a hydroxyl group, and preferably an alkyl group which may have a hydroxyl group. From the viewpoint of the removal performance and etching performance of the resist and modified resist, R ¹ to R ⁴ are particularly preferably an alkyl group having 1 to 4 carbon atoms which may have a hydroxyl group. Specific examples of R ¹ to R ⁴ include a methyl group, an ethyl group, a propyl group, a butyl group, and a 2-hydroxyethyl group.

In general formula (1), R ¹ to R ⁴ may be the same or different from each other. In one embodiment, R ¹ to R ⁴ may be the same group, preferably an alkyl group having 1 to 4 carbon atoms. In another embodiment, R ¹ to R ³ may be the same group (first group), and R ⁴ may be a group (second group) different from R ¹ to R ^3. In one embodiment, the first group and the second group may each independently be an alkyl group having 1 to 4 carbon atoms. In another embodiment, the first group may be an alkyl group having 1 to 4 carbon atoms, and the second group may be a hydroxyalkyl group having 1 to 4 carbon atoms.

Specific examples of quaternary ammonium hydroxides include tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), tetrabutylammonium hydroxide (TBAH), and trimethyl-2-hydroxyethylammonium hydroxide (also known as choline hydroxide).

Among these, TMAH is particularly preferred because it has excellent performance in removing resist and modified resist, excellent etching performance, and is inexpensive and versatile. Compounds in which some or all of the methyl groups in TMAH have been replaced with other groups such as ethyl groups, propyl groups, and butyl groups, i.e., the above-mentioned TEAH, TPAH, TBAH, and choline hydroxide, are inferior to TMAH in terms of performance in removing resist and modified resist, excellent etching performance, and the like, but are sometimes preferred at semiconductor device manufacturing sites because they are not toxic and are compatible with the resist materials used.

1.1.2 First Organic Solvent
The first organic solvent is a water-soluble organic solvent having a plurality of hydroxy groups. In the raw material mixture, as the first organic solvent, one type of solvent may be used alone, or two or more types of solvents may be used in combination.

Since a water-soluble organic solvent having two or more hydroxyl groups has a higher boiling point than water, it is possible to reduce the amount of water in the composition by distilling off water from the composition. The boiling point of the first organic solvent at a pressure of 0.1 MPa is preferably 150 to 300°C, more preferably 150 to 200°C. When the boiling point of the first organic solvent is 150°C or higher, the first organic solvent is less likely to be distilled off when water is distilled off, making it easier to reduce the amount of water in the composition. In addition, a first organic solvent having a boiling point equal to or lower than the above upper limit does not have a very high viscosity, making it possible to increase the efficiency of distilling off water.

As the first organic solvent, it is preferable to use one or more alcohols selected from dihydric or trihydric alcohols consisting of carbon atoms, hydrogen atoms, and oxygen atoms and having a boiling point of 150 to 300°C, more preferably dihydric or trihydric aliphatic alcohols. The melting point of the first organic solvent is preferably 25°C or lower, more preferably 20°C or lower.

Specific examples of preferred first organic solvents include dihydric alcohols such as ethylene glycol (boiling point 197°C), propylene glycol (boiling point 188°C), diethylene glycol (boiling point 244°C), dipropylene glycol (boiling point 232°C), tripropylene glycol (boiling point 267°C), and hexylene glycol (2-methyl-2,4-pentanediol) (boiling point 198°C); and trihydric alcohols such as glycerin (boiling point 290°C); and combinations thereof.

Among these, from the viewpoint of storage stability of the composition, alcohols having a hydroxyl group bonded to a secondary or tertiary carbon atom, such as propylene glycol, dipropylene glycol, tripropylene glycol, and hexylene glycol, can be preferably used as the first organic solvent. Among these, propylene glycol and hexylene glycol are particularly preferable from the viewpoint of the boiling point and storage stability of the composition described above, and are also preferable from the viewpoint of availability and cost.

(1.1.3 Composition of raw material mixture)
The ratio of the above three components in the raw material mixture is not particularly limited, but it is desirable that the amount of water is as small as possible. Quaternary ammonium hydroxides that are currently commercially available on an industrial scale are usually produced by electrolysis and are often distributed in the form of an aqueous solution. For example, the TMAH concentration of a concentrated aqueous solution of TMAH that is currently commercially available is typically about 20 to 25% by mass. Also, for example, the concentrations of concentrated aqueous solutions of TEAH, TPAH, TBAH, and choline hydroxide that are currently commercially available are typically about 10 to 55% by mass. The raw material mixture can be prepared, for example, by mixing an aqueous solution of quaternary ammonium hydroxide with the above water-soluble organic solvent. The mixing ratio of quaternary ammonium hydroxide and water in the raw material mixture thus prepared reflects the concentration of the aqueous solution of quaternary ammonium hydroxide used. From the viewpoint of reducing the amount of water to be distilled off in thin film distillation, it is desirable that the concentration of the aqueous solution of quaternary ammonium hydroxide used in the preparation of the raw material mixture is high. For example, a crystalline solid such as TMAH pentahydrate can be dissolved in a water-soluble organic solvent and used, but highly concentrated aqueous quaternary ammonium hydroxide solutions and crystalline solids are often expensive. The water content in the raw material mixture can be determined in consideration of the cost of obtaining the aqueous quaternary ammonium hydroxide solution and the crystalline solid, the impurity content, and the like.

The content of the first organic solvent in the raw material mixture may be, for example, preferably 30 to 85% by mass, more preferably 40 to 85% by mass, even more preferably 40 to 80% by mass, and particularly preferably 60 to 80% by mass, based on the total amount of the raw material mixture.

The content of quaternary ammonium hydroxide in the raw material mixture may be, for example, preferably 2.0 to 40 mass%, more preferably 2.0 to 30 mass%, even more preferably 2.0 to 25%, and particularly preferably 5.0 to 10 mass%, based on the total amount of the raw material mixture. The water content in the raw material mixture may be, for example, preferably 10 to 30 mass%, more preferably 15 to 30 mass%, based on the total amount of the raw material mixture.

It is desirable that the amount of impurities in the raw material mixture be small. In particular, it is desirable that the amount of impurities be small, since it is difficult to remove metal impurities and non-volatile impurities such as chloride ions, carbonate ions, nitrate ions, and sulfate ions by thin-film distillation.

Metal impurities exist as ions or fine particles in the solution. In this specification, metal impurities include both metal ions and metal particles. From the viewpoint of obtaining the high purity composition described above, the content of each metal impurity in the raw material mixture may be, for example, preferably 50 ppb by mass or less, more preferably 20 ppb by mass or less, and even more preferably 10 ppb by mass or less for each of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn, based on the total amount of the raw material mixture.

The content of chlorine impurities in the raw material mixture may be, for example, preferably 50 ppb by mass or less, more preferably 30 ppb by mass or less, and even more preferably 20 ppb by mass or less, based on the total amount of the raw material mixture.

The content of each metal impurity in the aqueous quaternary ammonium hydroxide solution used to prepare the raw material mixture is preferably 100 ppb by mass or less, more preferably 1 ppb by mass or less, based on the total amount of the aqueous solution. Also, when a crystalline solid raw material such as TMAH pentahydrate is used as the quaternary ammonium hydroxide source instead of an aqueous solution, it is preferable that the content of each metal impurity is 100 ppb by mass or less, based on the total amount of the crystalline solid raw material.

The content of each metal impurity in the first organic solvent used to prepare the raw material mixture is preferably 50 ppb by mass or less, more preferably 10 ppb by mass or less, based on the total amount of the first organic solvent. When the impurity content in a commercially available first organic solvent is high, the purity can be increased by distilling the first organic solvent alone.

The first organic solvent used to prepare the raw material mixture does not have to be an anhydrous solvent, but from the viewpoint of increasing the efficiency of thin-film distillation, the water content in the first organic solvent used to prepare the raw material mixture is preferably 1% by mass or less, more preferably 0.5% by mass or less, based on the total amount of the first organic solvent.

(1.2 Step (a): Thin-film distillation)
In step (a), the raw material mixture described above is thin-film distilled using a falling film type thin-film distillation apparatus. Thin-film distillation is a method in which a thin film of the raw material liquid is formed under reduced pressure, the thin film is heated, a part of the raw material liquid is evaporated according to the vapor pressure of the components contained in the raw material liquid, and the vapor is cooled and condensed, and the raw material liquid is separated into a distillate and a residual liquid (including a dissolved substance). By subjecting the raw material mixture described above to thin-film distillation, water can be distilled from the raw material mixture, and an organic solvent solution of quaternary ammonium hydroxide can be recovered as a residual liquid. A part of the organic solvent may be distilled together with the water. The water (and a part of the organic solvent) distilled from the raw material mixture is recovered as a distillate. According to thin-film distillation, it is possible to distill water while suppressing the thermal decomposition of the quaternary ammonium hydroxide.

(1.2.1 Thin Film Distillation Apparatus)
1 is a schematic diagram illustrating a falling film type thin film distillation apparatus 10A (hereinafter, sometimes referred to as "thin film distillation apparatus 10A" or simply "apparatus 10A") according to one embodiment that can be used in step (a). The apparatus 10A is a falling film type short-path thin film distillation apparatus.

The thin-film distillation apparatus 10A includes a raw material container 31 for storing the raw material mixture, an evaporation container (evaporator) 37 in which the actual distillation is performed, and a raw material pipe 33 for transferring the raw material mixture from the raw material container 31 to the evaporation container 37. As shown in FIG. 1, a needle valve 32 is provided midway along the raw material pipe 33. The device 10A further includes a residue liquid recovery container 12 connected to the evaporation container 37 for receiving the distillation residue liquid, a distillate recovery container 13 connected to the evaporation container 37 for receiving the distillate, a flow rate confirmation glass pipe 8 and a (residue liquid side) gear pump (liquid delivery pump) 10 provided in the middle of the flow path leading from the evaporation container 37 to the distillate liquid recovery container 12, a flow rate confirmation glass pipe 9 and a (distillate liquid side) gear pump (liquid delivery pump) 11 provided in the middle of the flow path leading from the evaporation container 37 to the distillate liquid recovery container 13, a vacuum pump 15 for reducing the pressure inside the evaporation container 37, and a cold trap 14 provided in the middle of the flow path leading from the evaporation container 37 to the vacuum pump 15.

The raw material mixture leaves the raw material container 31, passes through the needle valve 32 and raw material piping 33, and flows into the evaporation container (evaporator) 37. A constant degree of vacuum is maintained in the system including the evaporation container 37 by the action of the vacuum pump 15, needle valve 32, and gear pumps (liquid delivery pumps) 10, 11 (on the residue liquid side and distillate side). The raw material mixture in the raw material container 31 spontaneously flows into the raw material piping 33 through the needle valve 32 due to the pressure difference between the vacuum in the system and atmospheric pressure.

In the thin-film distillation apparatus 10A, the liquid contacting parts in the flow path of the raw material mixture from the raw material container 31 to the evaporation container 37, specifically, the liquid contacting parts of the inner surface of the raw material container 31 and the liquid contacting parts of the raw material pipe 33 (including the liquid contacting parts of the needle valve 32), are preferably made of resin. By making the liquid contacting parts from resin, it is possible to suppress the elution of metal materials from the liquid contacting parts. Quaternary ammonium hydroxide available as a raw material must contain water. Generally, water is involved in the elution reaction of metal materials. By making the liquid contacting parts in the flow path of the raw material mixture from the raw material container 31 to the evaporation container 37 from resin, the time during which the raw material mixture in which quaternary ammonium hydroxide and water coexist comes into contact with the metal material can be shortened, and it is possible to suppress the reaction in which the metal material elutes from the liquid contacting parts into the liquid and becomes a metal impurity in the liquid. From the viewpoint of further suppressing the elution of metal materials from the liquid contacting parts, it is preferable that the liquid contacting parts in the flow path from the evaporation container 37 to the residue liquid recovery container 12 are also made of resin.

As the resin constituting the liquid contact portion, a resin material having durability against alkaline aqueous solutions and water-soluble organic solvents can be preferably used. Examples of such resin materials include fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF); polyolefin resins such as polyethylene (PE) and polypropylene (PP); thermoplastic resins such as acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS resin), nylon, acrylic resin, acetal resin, and rigid polyvinyl chloride; and thermosetting resins such as melamine resin, furan resin, and epoxy resin. Among them, polyethylene, polypropylene, and fluororesins are particularly preferably used because they are easy to process and have a low amount of elution of metal impurities.

For small-diameter piping that does not require much structural strength, piping made only of resin may be used. On the other hand, for large-diameter piping and the raw material container 31 that require strength, it is preferable to construct the structural members from a metal material (such as stainless steel) and to cover the liquid-contacting parts with the above-mentioned resin material. The resin coating on the liquid-contacting parts only needs to be thick enough to prevent peeling, and can be preferably about 0.5 to 5 mm thick, for example.

Glass is also known to be resistant to chemicals, but a raw material mixture in which highly basic substances such as quaternary ammonium hydroxide coexist with water can gradually corrode even glass, so it is preferable to use resin rather than glass as the material for the liquid contact parts.

When the resin material has a porous structure, metal impurities may leach from inside the resin, so a non-porous resin material is preferred. The content of metal impurities in the resin material constituting the liquid-contacting part is preferably 1 mass ppm or less, more preferably 0.1 mass ppm or less, for each of Na, Ca, Al, and Fe, based on the total amount of resin. Such high-purity resins are commercially available.

Here, Na, Ca, Al, and Fe are listed as metal impurities in resin because, first, these four types of metal impurities are typical impurities that are mixed into resin, and if the content of each of these four types of metal impurities in a resin is 0.1 mass ppm or less, the content of other metal impurities in the resin is generally 0.1 mass ppm or less in most cases; and second, it is not easy to grasp the content of all types of metal impurities, and it is rare to obtain sufficient data from manufacturers for commercially available resins. Strictly speaking, the content of each of the above-mentioned Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn in a resin is preferably 1 mass ppm or less, and more preferably 0.1 mass ppm or less.

Figure 2 is a cross-sectional view that illustrates the details of the evaporation container 37 in the apparatus 10A. In Figure 2, elements that have already appeared in Figure 1 are given the same reference numerals as in Figure 1, and their explanations are omitted. The apparatus 10A includes an evaporation container 37 and a first flow path (raw material piping 33) that introduces the raw material mixture from the top of the evaporation container 37 into the evaporation container 37. The raw material mixture introduced from the first flow path (raw material piping 33) into the evaporation container 37 flows down along the inner wall surface of the evaporation container 37 as a liquid film. The apparatus 10A further includes a heating surface 24 arranged on the inner wall surface to heat the liquid film flowing down along the inner wall surface, a condenser (internal condenser) 22 arranged inside the evaporation container 37 to cool and liquefy the vapor generated from the liquid film, a second flow path to collect the distillate liquefied by the condenser 22 from the evaporation container 37 to the distillate recovery container 13, and a third flow path to collect the residual liquid that does not evaporate on the heating surface 24 and flows down from the heating surface 24 from the evaporation container 37 to the residual liquid recovery container 12. The apparatus 10A also includes a wiper (roller wiper) 21 arranged inside the evaporation container 37 and rotates along the inner wall surface of the evaporation container 37. The raw material mixture introduced into the evaporation container 37 from the first flow path (pipe 33) is applied to the inner wall surface by the rotating wiper 21 to form a liquid film.

The heating surface 24 is heated by the circulating heat medium 25. The flow rate of the raw material mixture 23 when introduced into the evaporation container 37 can be adjusted by the needle valve 32 or a flow rate regulator (not shown). A liquid film is formed on the inner wall of the evaporation container 37 by the roller wiper 21, and heat exchange occurs on the heating surface 24 arranged on the inner wall surface of the evaporation container 37, evaporating water. Usually, at the same time, a part of the organic solvent also evaporates according to the vapor pressure of the organic solvent. The evaporated water and organic solvent are condensed in a condenser (internal condenser) 22 arranged near the center of the evaporation container 37 and separated from the liquid film, to become a distillate. The condenser 22 is cooled by a circulating refrigerant 26.

From the viewpoint of the overall material properties such as heat resistance, abrasion resistance, corrosion resistance, thermal conductivity, and strength, it is generally preferable that the inner wall of the evaporation container 37 is made of a highly corrosion-resistant metal material such as stainless steel. From the viewpoint of further suppressing the elution of metal impurities, it is also possible to make the inner wall of the evaporation container 37 out of a resin member or a resin-coated metal member. However, if the inner wall of the evaporation container 37 is also made of a resin member or a resin-coated member, the efficiency of heat exchange between the liquid film on the heating surface 24 and the heat medium 25 decreases, so it becomes necessary to control the temperature of the heating surface 24 to a higher temperature, and as a result, there is a risk that the thermal decomposition of the quaternary ammonium hydroxide will progress during thin-film distillation. In addition, since the roller wiper 21 rotates inside the evaporation container 37, if the inner wall of the evaporation container 37 is also made of a resin member or a resin-coated member, resin may peel off from the inner wall of the evaporation container 37 when the roller wiper 21 comes into contact with the inner wall of the evaporation container 37, and resin pieces may be mixed into the residual liquid to be collected.

Even if the inner wall of the evaporation vessel 37 is made of a metal material, the content of metal impurities in the resulting composition (residual liquid) does not deteriorate significantly. The reasons for this are not fully understood, but the following three are considered: (1) The residence time of the liquid film on the inner wall surface of the evaporation vessel is several seconds to several minutes, which is a short time for metal impurities to dissolve; (2) Water is required for the reaction in which the metal material dissolves in the alkaline liquid, but in thin film distillation, most of the water is removed from the liquid film in a short time, so the time for the conditions for dissolving metal impurities to be met is very short; (3) The composition obtained by the manufacturing method of the present invention usually has a higher viscosity than the water-soluble organic solvent in the composition. In addition, the raw material mixture has a relatively high viscosity depending on the viscosity of the water-soluble organic solvent and the concentration of the quaternary ammonium hydroxide, but the viscosity increases further as the water is distilled off. That is, when the raw material mixture passes through the heated surface 24 of the evaporation container 37, most of the water is lost in a short time at the interface between the heated surface 24 and the liquid film, and the viscosity of the liquid increases, making it difficult for a flow to stir the liquid inside the liquid film to occur, making it difficult for water to come into contact with the heated surface 24, which is thought to result in suppression of the elution of metal impurities.

The roller wiper 21 may be made of resin, but it is preferable that the resin material constituting the roller wiper 21 does not contain reinforcing materials such as glass fibers. Since the roller wiper 21 is in continuous contact with the raw material mixture and the liquid film during thin-film distillation, if the resin constituting the roller wiper 21 contains glass fibers, metal impurities such as Al and Ca in the glass fibers may dissolve into the liquid. In addition, if the resin constituting the roller wiper 21 contains glass fibers, when the roller wiper 21 comes into contact with the inner wall surface of the evaporation container 37, glass fiber fragments and fine particles generated from the inner wall surface may be mixed into the residual liquid.

Preferred examples of the resin material constituting the roller wiper 21 include general-purpose engineering plastics such as polyacetal (POM), polyamide (PA), polycarbonate (PC), modified polyphenylene ether (m-PPE), polybutylene terephthalate (PBT), ultra-high molecular weight polyethylene (UHPE), and syndiotactic polystyrene (SPS); as well as heat-resistant and relatively high-strength resins such as super engineering plastics such as polyether ether ketone (PEEK), polyimide (PI), polyetherimide (PEI), and fluororesin. Among these, PEEK, PI, fluororesin, etc. are preferably used from the viewpoints of heat resistance, strength, purity, etc.

The distillate condensed by the condenser 22 is guided to the distillate recovery container 13 through a second flow path equipped with a gear pump (liquid delivery pump) 11 (distillate side) and recovered. The uncondensed steam is captured and recovered by a cold trap 14. The residual liquid that flows down from the heating surface 24 after the water is distilled off is guided to the residual liquid recovery container 12 through a third flow path equipped with a gear pump (liquid delivery pump) 10 (residue liquid side) and recovered.

In the thin-film distillation apparatus 10A (FIG. 1), a glass pipe 8 for checking the flow rate of the residue liquid side (hereinafter sometimes referred to as "glass pipe 8") is provided in the third flow path for recovering the residue liquid, and a glass pipe 9 for checking the flow rate of the distillate liquid side (hereinafter sometimes referred to as "glass pipe 9") is provided in the second flow path for recovering the distillate, for example. However, the glass pipes 8 and 9 are not necessarily required. Rather, the glass pipes 8 and 9 are made of glass and may be a source of contamination (a source of elution of metal impurities). From the viewpoint of further reducing the content of metal impurities in the composition (residual liquid) to be produced, for example, a thin-film distillation apparatus 10B (FIG. 3) in which the glass pipe 8 is removed from the third flow path of the thin-film distillation apparatus 10A can be preferably used instead of the thin-film distillation apparatus 10A (FIG. 1).

The thin-film distillation apparatus 10A (FIG. 1) is provided with a gear pump (liquid delivery pump) 10 (on the residue side) provided in the middle of the third flow path that guides the residue liquid from the evaporation container 37 to the residue liquid recovery container 12, and a gear pump (liquid delivery pump) 11 (on the distillate side) provided in the middle of the second flow path that guides the distillate from the evaporation container 37 to the distillate recovery container 13, as elements for maintaining airtightness in the system including the inside of the evaporation container 37. The gear pumps (liquid delivery pumps) 10 and 11 are liquid delivery pumps that push the liquid on the residue side or the distillate side toward the recovery container 12 or 13 while maintaining airtightness in the system. The material of each part (casing, gears, etc.) used in the liquid contact parts of these airtight liquid delivery pumps may be a metal material (e.g., stainless steel, etc.) having sufficient corrosion resistance. The reason is the same as the reason why the inner wall of the evaporation container does not need to be covered with resin. That is, the water content of the residual liquid that comes into contact with the liquid contact part of the liquid delivery pump 10 on the residue liquid side is sufficiently low, and the time that the residual liquid comes into contact with the liquid contact part of the liquid delivery pump 10 is sufficiently short, so that even if the liquid contact part of the liquid delivery pump 10 is made of a metal material such as stainless steel, it is considered that there is almost no elution of metal impurities from the liquid contact part of the liquid delivery pump 10 into the residual liquid. However, from the viewpoint of further reducing the content of metal impurities in the composition produced, it is also possible to use a liquid delivery pump having a liquid contact part made of resin such as engineering plastic or super engineering plastic as the liquid delivery pump 10 on the residue liquid side.

Examples of the vacuum pump 15 include known vacuum pumps such as an oil rotary pump, an oil diffusion pump, a cryopump, an oscillating piston type vacuum pump, a mechanical booster pump, a diaphragm pump, a roots type dry pump, a screw type dry pump, a scroll type dry pump, and a vane type dry pump. As the vacuum pump 15, one vacuum pump may be used alone, or multiple vacuum pumps may be used in combination.

The cold trap 14 condenses or solidifies the vapor that was not condensed in the condenser 22 into a liquid or solid, prevents the evaporated water or organic solvent from reaching the vacuum pump 15, and prevents the evaporated oil or oil mist from the vacuum pump 15, such as an oil rotary pump, from flowing into the evaporation vessel 37 and contaminating the system. A known cold trap device can be used as the cold trap 14. The cold trap 14 can be cooled using, for example, dry ice, a coolant made of a mixture of dry ice and an organic solvent (alcohol, acetone, hexane, etc.), liquid nitrogen, a circulating refrigerant, etc.

In the above description, thin-film distillation apparatuses 10A (FIG. 1) and 10B (FIG. 3) are shown as examples in which the liquid delivery pumps 10 and 11 are provided only downstream of the evaporation container 37. However, the thin-film distillation apparatus may also be provided with a liquid delivery pump upstream of the evaporation container 37. FIG. 4 is a schematic diagram of a thin-film distillation apparatus 10C (hereinafter, simply referred to as "apparatus 10C") according to another embodiment. In FIG. 4, the elements already shown in FIGS. 1 to 3 are given the same reference numerals as those in FIGS. 1 to 3, and their description is omitted. The thin-film distillation apparatus 10C differs from the thin-film distillation apparatus 10A (FIG. 1) in that it has a raw material pipe 3 instead of the raw material pipe 33 that guides the raw material mixture from the raw material container 31 to the evaporation container 37, and further has a raw material gear pump 4, a preheater (preheater) 5, and a degasser (degasser) 6 in this order from the upstream side, in the middle of the raw material pipe 3 and downstream of the needle valve 32. In the apparatus 10C, the liquid-contacting parts in the flow path of the raw material mixture from the raw material container 31 to the evaporation container 37, i.e., the liquid-contacting parts of the raw material pipe 3 (including the needle valve 32), the raw material gear pump 4, the preheater 5, and the degasser 6, are preferably made of a resin material. However, since making all of the liquid-contacting parts of the raw material gear pump 4, the preheater 5, and the degasser 6 out of a resin material generally leads to an increase in the cost of the apparatus, it is preferable to adopt a thin-film distillation apparatus that does not include the raw material gear pump 4, the preheater 5, and the degasser 6, as in the apparatuses 10A and 10B described above.

In the above explanation, thin film distillation apparatuses 10A (FIG. 1), 10B (FIG. 3), and 10C (FIG. 4) are given as examples in which valve 32 is provided with a needle valve. However, valve 32 does not necessarily have to be a needle valve, and other known valves such as a diaphragm valve, butterfly valve, ball valve, or gate valve can be used as valve 32 instead of a needle valve.

Examples of commercially available thin film distillation apparatuses that can be used in step (a) include short-path distillation apparatus (manufactured by UIC); Wiplen (registered trademark), Exeva (registered trademark) (both manufactured by Kobelco Environmental Solutions); Contro, Sebcon (registered trademark) (both manufactured by Hitachi Plant Mechanics); Viscon, Filmtruder (both manufactured by Buss-SMS-Canzler GmbH, available from Kimura Kakoki); Ebaracter, Hi-U Brusher, Wallwetter (all manufactured by Kansai Chemical Machinery Manufacturing Co., Ltd.); NRH (manufactured by Nichinan Machinery Co., Ltd.), etc. Since quaternary ammonium hydroxide decomposes when heated for a long time, from the viewpoint of increasing the distillation efficiency, among falling film type thin film distillation apparatuses, a short-path type thin film distillation apparatus can be preferably used.
In this specification, the falling film type thin film distillation apparatus means a thin film distillation apparatus in which a thin film (liquid film) of a liquid introduced into an evaporation vessel is formed on a heated surface inside the evaporation vessel (for example, by a rotor or the like), and distillation is performed while the liquid film flows down along the heated surface. The short-step type thin film distillation apparatus (short-step distillation apparatus) is a thin film distillation apparatus that has been developed to improve separation performance based on the technical concept of molecular distillation. In the short-step distillation apparatus, a condenser is arranged inside a cylindrical evaporation vessel so that the cooling surface of the condenser faces the heating surface of the evaporation vessel. Distillation using a short-step distillation apparatus (short-step distillation) is often performed under a pressure of about medium vacuum (on the order of 10 ⁻¹ to 10 ² Pa).

When using the commercially available thin-film distillation apparatus described above, it is preferable to use an apparatus that has been modified so that the liquid-contacting part upstream of the evaporation vessel is made of resin.

(1.2.2 Distillation conditions)
The properties of the organic solvent solution of quaternary ammonium hydroxide obtained by thin-film distillation can be mainly affected by the temperature of the raw material mixture immediately before it enters the evaporation vessel 37 (first temperature), the temperature of the heating surface 24 of the evaporation vessel 37 (second temperature), and the degree of vacuum of the system.

The temperature of the raw material mixture immediately before entering the evaporation container 37 (first temperature) must be 70°C or lower, and more preferably 60°C or lower. By having the first temperature be equal to or lower than the upper limit value, it is possible to reduce the elution of metal impurities from the evaporation container 37 when the raw material mixture with a high moisture content comes into contact with the inner wall surface of the evaporation container 37. In addition, the first temperature is preferably 5°C or higher, and more preferably 15°C or higher. By having the first temperature be equal to or higher than the lower limit value, it is possible to suppress the generation of precipitates containing quaternary ammonium hydroxide and further increase the evaporation efficiency.

The temperature of the heating surface 24 (second temperature) must be higher than the first temperature, 60 to 140°C, and more preferably 70 to 120°C. By making the second temperature equal to or higher than the lower limit, the evaporation efficiency can be increased and the amount of water in the liquid film can be quickly reduced, making it possible to reduce the elution of metal impurities from the evaporation container 37. Furthermore, by making the second temperature equal to or lower than the upper limit, it is possible to reduce the evaporation of the organic solvent and to reduce the elution of metal impurities from the evaporation container 37. In this specification, the "temperature of the heating surface" of the thin-film distillation apparatus means the temperature of the heat source that heats the liquid film.

The degree of vacuum of the system (the degree of vacuum inside the evaporation container 37 or from the evaporation container 37 to the vacuum pump) must be 600 Pa or less, preferably 550 Pa or less, more preferably 400 Pa or less, and in one embodiment, may be 200 Pa or less. By having the degree of vacuum of the system be equal to or less than the above upper limit, the evaporation efficiency can be increased and the amount of water in the liquid film can be quickly reduced, so that it is possible to reduce the elution of metal impurities from the evaporation container 37. The lower limit of the degree of vacuum is not particularly limited, but may be 0.1 Pa or more in one embodiment, and 1 Pa or more in another embodiment. By having the degree of vacuum of the system be equal to or more than the above lower limit, it becomes easy to avoid clogging of the exhaust system piping due to the evaporant condensing or solidifying in the cold trap 14. The degree of vacuum of the system can be measured using a pressure measuring device (not shown) such as a manometer or vacuum gauge installed in the middle of the exhaust system piping connecting the evaporation container 37 and the vacuum pump 15. In one embodiment, the pressure measuring device can be installed between the cold trap 14 and the vacuum pump 15.

The preferred supply amount (feed rate) of the raw material mixture to the evaporation vessel 37 may vary depending on the scale of the thin film distillation apparatus. If the feed rate is too high, the evaporation efficiency decreases, and if the feed rate is too low, the productivity decreases. If the distillation conditions such as the temperature of the heating surface 24 and the degree of vacuum in the evaporation vessel 37 are the same, the larger the heat transfer area (area of the heating surface 24) of the thin film distillation apparatus, the higher the feed rate can be. For example, when using a thin film distillation apparatus with a heat transfer area of 0.1 m ² , the feed rate can be preferably 1 to 10 kg/hour. When the temperature (first temperature) of the raw material mixture just before entering the evaporation vessel 37, the temperature (second temperature) of the heating surface 24, and the degree of vacuum of the system (the degree of vacuum inside the evaporation vessel 37 or from the evaporation vessel 37 to just before the vacuum pump) are within the above ranges, the feed rate per unit area of the heating surface 24 can be, for example, 10 to 100 kg/hour·m ² .

By going through step (a), water can be removed by evaporation from the raw material mixture to obtain an organic solvent solution of quaternary ammonium hydroxide.

(1.3 Step (b): Washing step)
In a preferred embodiment, the solution producing method of the present invention may further include a step (hereinafter sometimes referred to as "step (b)") of cleaning the liquid-contacting parts in the flow path of the raw material mixed solution from the raw material container 31 to the evaporation container 37 (for example, in the above-mentioned apparatus 10A, the liquid-contacting parts of the inner surface of the raw material container 31 and the liquid-contacting parts of the raw material pipe 33 (including the liquid-contacting parts of the needle valve 32)) before the step (a). Preferable examples of the solution (cleaning solution) used for the cleaning in the step (b) include water with very little metal impurities such as ultrapure water and pure water; and a solution containing the above-mentioned quaternary ammonium hydroxide, such as an aqueous solution of quaternary ammonium hydroxide used as a part of the raw material and the raw material mixed solution. Among these, a solution containing quaternary ammonium hydroxide can be preferably used as the cleaning solution, and a solution containing the same quaternary ammonium hydroxide as the quaternary ammonium hydroxide contained in the raw material mixed solution can be particularly preferably used as the cleaning solution. The content of metal impurities in the cleaning solution is preferably 0.05 ppm by mass or less, more preferably 0.02 ppm by mass or less, and even more preferably 0.01 ppm by mass or less, based on the total amount of the solution, for each of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn.

The washing of the liquid contact part can be carried out, for example, by circulating the above-mentioned washing liquid through the (e.g., resin) part constituting the liquid contact part for about 10 minutes to 2 hours, or by storing and holding the above-mentioned washing liquid in the (e.g., resin) part constituting the liquid contact part. By carrying out step (b) before step (a), metal impurities in a state capable of eluting are reduced or removed from the surface of the member constituting the liquid contact part, so that it is possible to further reduce the metal impurities eluted from the liquid contact part during thin-film distillation. In one preferred embodiment, after washing the liquid contact part with a quaternary ammonium hydroxide aqueous solution or a raw material mixture, the liquid contact part may be further washed (rinsed) for a short time with water having a very low metal impurity content, such as ultrapure water or pure water. According to this form of step (b), it is possible to further reduce the amount of metal impurities eluted from the liquid contact part in step (a). Note that, for example, when it is clear that elutable metal impurities have already been reduced or removed from the surface of the (e.g., resin) member constituting the liquid contact part, it is also possible to make a method for producing an organic solvent solution of quaternary ammonium hydroxide in a form in which step (b) is not carried out.

It is possible to wash the liquid-contacting parts with an acid aqueous solution, but when the acid aqueous solution is brought into contact with the liquid-contacting parts, the anions contained in the acid aqueous solution tend to remain on the resin surface, and it takes time to wash and remove the anions with ultrapure water or pure water. Therefore, it is preferable not to use an acid aqueous solution to wash the liquid-contacting parts, and it is preferable to wash the liquid-contacting parts with a solution containing quaternary ammonium hydroxide and/or water with a very low content of metal impurities, such as pure water or ultrapure water.

(1.4 Properties of Quaternary Ammonium Hydroxide Solutions in Organic Solvents)
(1.4.1 Quaternary Ammonium Hydroxide Content)
In one embodiment, the content of quaternary ammonium hydroxide in the organic solvent solution of quaternary ammonium hydroxide obtained by the solution production method of the present invention (hereinafter, sometimes simply referred to as "organic solvent solution" or simply "solution") may be preferably 5.0 mass% or more, more preferably 8.0 mass% or more, based on the total amount of the solution. When the content of quaternary ammonium hydroxide in the solution is equal to or more than the above lower limit, the distribution cost of the solution can be saved. The upper limit of the content is not particularly limited, but may be 72 mass% or less in one embodiment and 55 mass% or less in another embodiment. When the content of quaternary ammonium hydroxide in the solution is equal to or less than the above upper limit, the viscosity of the solution is suppressed from increasing, and handling, delivery, mixing, etc., when using the solution are facilitated.

The concentration of quaternary ammonium hydroxide in a solution can be accurately measured using a potentiometric titrator, liquid chromatography, etc. These measurement methods may be used alone or in combination. These measurement methods can also be applied to measuring the concentration of quaternary ammonium hydroxide in a raw material mixture.

In one embodiment, the content of quaternary ammonium hydroxide in the solution may be 2.38 to 25.0 mass% based on the total amount of the solution. In one preferred embodiment, TMAH may be used as the quaternary ammonium hydroxide, and the content of TMAH in the solution may be 2.38 to 25.0 mass% based on the total amount of the solution.

1.4.2 Moisture Content
The water content in the organic solvent solution obtained by the solution manufacturing method of the present invention is 1.0 mass% or less, preferably 0.5 mass% or less, more preferably 0.3 mass% or less, based on the total amount of the composition. By making the water content in the solution equal to or less than the above upper limit, it is possible to improve the removal performance of the modified photoresist and the ashing residue of the photoresist, and to reduce the corrosiveness to metal materials and inorganic substrate materials. The lower limit of the water content in the solution is not particularly limited, but may be, for example, 0.05 mass% or more.

The amount of water in an organic solvent solution can be measured by gas chromatography, or by combining a Karl Fischer moisture meter using the Karl Fischer method (hereinafter sometimes referred to as "Karl Fischer titration") with gas chromatography. The Karl Fischer moisture meter allows for simple measurements, but the measurements obtained by Karl Fischer titration may contain errors due to interference reactions in the presence of alkali. On the other hand, gas chromatography allows for accurate measurements of the amount of water regardless of the presence or absence of alkali, but the measurement procedure is not necessarily simple. For a solution having an alkali concentration similar to that of the organic solvent solution, a calibration curve is prepared in advance, plotting the moisture amount measured by the Karl Fischer moisture meter on the vertical axis and the moisture amount measured by gas chromatography on the horizontal axis, and the moisture amount can be accurately quantified by simple procedures by correcting the measurements by the Karl Fischer moisture meter using the calibration curve. Commercially available devices can be used for the gas chromatography and the Karl Fischer moisture meter.

The operation of correcting the moisture content measured by the Karl Fischer moisture meter using a calibration curve can be preferably carried out by the following steps (1) to (6).
(1) The amount of water in the same organic solvent as that in the solution to be measured is measured by Karl Fischer titration. For example, five types of solutions (hereinafter sometimes referred to as "water/organic solvent solutions") with different amounts of water are prepared by adding water to the organic solvent. The amount of water added to the organic solvent is selected so that the amount of water in the solution to be measured is included in the range of the amount of water in the water/organic solvent solution. For example, if the amount of water in the solution to be measured is considered to be 0.05 to 5.0% by mass, the amount of water added to the organic solvent can be determined so that the amount of water in the water/organic solvent solution is in five stages from 0.05 to 5.0% by mass. It is desirable to measure the amount of water in the five types of water/organic solvent solutions prepared by Karl Fischer titration and confirm that the obtained value shows good agreement with the theoretical value calculated from the amount of water in the organic solvent and the amount of water added.
(2) Each of the five types of water/organic solvent solutions prepared in (1) above is analyzed by gas chromatography (hereinafter sometimes referred to as "GC") to obtain a GC chart containing peaks of water and organic solvent. The area of the water peak in the obtained GC chart is plotted on the vertical axis (Y) and the amount of water in the water/organic solvent solution (theoretical value calculated from the amount of water in the organic solvent and the amount of water added) on the horizontal axis (X). A regression line is calculated by the least squares method using Y as the objective variable and X as the explanatory variable to obtain a calibration curve (hereinafter sometimes referred to as "first calibration curve") that gives the amount of water from the area of the water peak in the GC chart.
(3) Five types of mixed solutions are prepared as standard solutions by adding a concentrated aqueous solution of the same quaternary ammonium hydroxide (QAH) as the QAH in the solution to be measured (the QAH concentration in the concentrated aqueous solution may be as high as possible within the available range, for example, 10 to 25% by mass) to the same organic solvent as the organic solvent in the solution to be measured. The water content in the organic solvent is accurately measured by Karl Fischer titration in the above (1). The QAH concentration in the concentrated QAH aqueous solution is accurately measured by an automatic potentiometric titrator. This simultaneously determines the water content in the concentrated QAH aqueous solution. The mixing mass ratio of the organic solvent to the concentrated QAH aqueous solution is selected so that the water content in the mixed solution is in the same five stages as in the above (1).
(4) The five kinds of standard solutions prepared in (3) above are analyzed by gas chromatography, and the water content in each standard solution is obtained from the area of the water peak in the GC chart using the first calibration curve obtained in (2) above. In general, the measured water content by GC shows good agreement with the theoretical value of the water content in the standard solution calculated from the water content in the organic solvent, the water content in the concentrated aqueous solution of QAH, and the mixture mass ratio of the organic solvent and the concentrated aqueous solution of QAH.
(5) The water content of each of the five standard solutions prepared in (3) above is measured by Karl Fischer titration. For each standard solution, the water content measured by Karl Fischer titration is plotted on the vertical axis (Y) and the water content in the standard solution measured by GC in (3) above is plotted on the horizontal axis (X). A regression line is calculated by the least squares method using Y as the objective variable and X as the explanatory variable, to obtain a calibration curve (hereinafter sometimes referred to as a "second calibration curve") that corrects the water content measurement value by Karl Fischer titration to the water content measurement value by GC for the organic solvent solution containing QAH and water.
(6) The water content of the actual solution to be measured is measured by Karl Fischer titration, and the measured value is corrected to the water content measured by GC using the second calibration curve obtained in (5) above.

It is not essential to measure the amount of water in the organic solvent solution of ammonium hydroxide by Karl Fischer titration. By using the first calibration curve obtained by steps (1) and (2) above, the amount of water in the solution containing an alkali can be accurately measured by gas chromatography analysis. The above measurement method can also be applied to measuring the amount of water in a raw material mixture.

The ratio of the water content (unit: mass %) in the solution to the quaternary ammonium hydroxide content (unit: mass %) in the solution (water content/quaternary ammonium hydroxide content) is preferably 0.42 or less, more preferably 0.21 or less, and even more preferably 0.10 or less. By keeping this ratio below the upper limit, it becomes possible to further reduce corrosiveness to metal materials and inorganic substrate materials while maintaining or improving the performance of removing modified photoresist and ashing residues of photoresist. The lower limit of this ratio is not particularly limited, but can be, for example, 0.0007 or more.

1.4.3 Impurity Content
The content of metal impurities in the organic solvent solution obtained by the solution producing method of the present invention is preferably 100 mass ppb or less, more preferably 50 mass ppb or less, and even more preferably 20 mass ppb or less, based on the total amount of the solution, for each of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn. In this specification, the content of metal impurities in the solution means the total content of the metal element, regardless of whether it is a zero-valent metal or a metal ion.

The content of chlorine impurities (Cl) in the solution is preferably 100 mass ppb or less, more preferably 80 mass ppb or less, and further preferably 50 mass ppb or less, based on the total amount of the solution. In this specification, the content of chlorine impurities in the solution means the total content of chlorine element. In the solution, the chlorine impurities are usually present in the form of chloride ions (Cl ^- ).

The content of metal impurities in a solution can be measured using a microanalytical device such as an inductively coupled plasma mass spectrometer (ICP-MS). The content of chlorine impurities can be measured using a microanalytical device such as ion chromatography. These methods for measuring the content of metal impurities and chlorine impurities can also be applied to measuring the content of metal impurities and chlorine impurities in a raw material mixture.

The ratio of the content of the above metal impurities in the solution (unit: mass ppb) to the content of quaternary ammonium hydroxide in the solution (unit: mass %) (content of metal impurities/content of quaternary ammonium hydroxide) is preferably 42 or less for each of the above metal elements, more preferably 21 or less, and even more preferably 10 or less. By keeping this ratio below the upper limit, it becomes possible to further increase the manufacturing yield of semiconductor devices while maintaining or improving the removal performance of modified photoresist and ashing residue of photoresist. There is no particular lower limit for this ratio, and the lower the better, but taking into account the quantitative limit of the measuring device for metal impurities, it may be, for example, 0.0001 or more.

The ratio (chlorine content/quaternary ammonium hydroxide content) of the chlorine impurity content in the solution (unit: mass ppb) to the quaternary ammonium hydroxide content in the solution (unit: mass %) is preferably 42 or less, more preferably 34 or less, and even more preferably 21 or less. By keeping this ratio below the upper limit, it becomes possible to further increase the manufacturing yield of semiconductor devices while maintaining or improving the performance of removing modified photoresist and ashing residues of photoresist. There is no particular lower limit for this ratio, and the lower the better, but taking into account the quantitative limit of the chlorine impurity measuring device, it may be, for example, 0.001 or more.

1.4.4 Uses
The solution obtained by the solution producing method of the present invention can be preferably used as a chemical solution such as a photoresist developer, a stripping solution and a cleaning solution for modified photoresist, and a silicon etching solution used in the manufacturing process of semiconductor devices. In addition, it can be preferably used as a concentrated liquid that is a raw material for producing the above-mentioned chemical solution. For example, a chemical solution having a desired quaternary ammonium hydroxide concentration can be obtained by diluting the organic solvent solution obtained by the solution producing method of the present invention with a water-soluble organic solvent having multiple hydroxyl groups (first organic solvent), or an organic solvent other than the water-soluble organic solvent having multiple hydroxyl groups (hereinafter sometimes referred to as the "second organic solvent"), or a combination thereof.

In addition, by adding water to the solution obtained by the solution production method of the present invention, it is possible to produce various chemical solutions with a controlled water content. That is, the organic solvent solution obtained by the solution production method of the present invention can also be used as a raw material for producing a chemical solution having a controlled water content. As described in Section 1.1.3 above, simply diluting an aqueous quaternary ammonium hydroxide solution commercially available on an industrial scale with an organic solvent may not produce a solution having a composition in which the quaternary ammonium hydroxide concentration and the organic solvent concentration are within the desired range. The solution obtained by the solution production method of the present invention is useful as a raw material for obtaining a quaternary ammonium hydroxide solution with such a composition.
For example, in the case of an etching solution such as a silicon etching solution, it may be required to control the etching rate by the water content. In such applications, it is required to strictly control the water content in the chemical solution. By adding high-purity water such as ultrapure water to the solution obtained by the solution production method of the present invention, a solution with a strictly controlled water content can be obtained. In such applications, water can be added, for example, so that the water content in the solution is preferably 1.0 to 40 mass%, more preferably 2.0 to 30 mass%, and even more preferably 3.0 to 20 mass% based on the total amount of the solution. The water content that the solution should have after the addition of water is determined, for example, by the desired etching rate. In order to adjust both the water content and the concentration of the quaternary ammonium hydroxide, an organic solvent (a water-soluble organic solvent having a plurality of hydroxyl groups (first organic solvent), or an organic solvent other than a water-soluble organic solvent having a plurality of hydroxyl groups (second organic solvent), or a combination thereof) may be added together with water.

2. Method for producing processing liquid composition for semiconductor manufacturing
The method for producing a processing solution composition for semiconductor manufacturing according to the second aspect of the present invention (hereinafter, sometimes referred to as "composition production method") is a method for producing a processing solution composition for semiconductor manufacturing based on a quaternary ammonium hydroxide organic solvent solution (hereinafter, sometimes referred to as "processing solution composition for semiconductor manufacturing" or simply as "composition"). The composition production method of the present invention includes (i) a step of obtaining an organic solvent solution of quaternary ammonium hydroxide by the solution production method according to the second aspect of the present invention (hereinafter, sometimes referred to as "step (i)"), (ii) a step of determining the concentration of quaternary ammonium hydroxide in the organic solvent solution (hereinafter, sometimes referred to as "step (ii)"), and (iii) a step of adjusting the concentration of quaternary ammonium hydroxide in the organic solvent solution by adding an organic solvent to the organic solvent solution (hereinafter, sometimes referred to as "step (iii)").

(2.1 Step (i): Solution Preparation Step)
Step (i) is a step of obtaining a solution of quaternary ammonium hydroxide in an organic solvent by the solution producing method according to the first aspect of the present invention, the details of which are as described in Section 1 above.

(2.2 Step (ii): Concentration determination step)
Step (ii) is a step of grasping the concentration of quaternary ammonium hydroxide in the solution obtained in step (i). The measurement of the concentration of quaternary ammonium hydroxide in the solution can be preferably performed by the same method as described in Section 1.4.1 above in relation to the solution producing method according to the first aspect of the present invention. In addition, if there is a past record of producing an organic solvent solution of quaternary ammonium hydroxide by the solution producing method according to the first aspect of the present invention under the same conditions (composition of the raw material mixture and distillation conditions) as those under which step (i) was performed, and measuring the concentration of quaternary ammonium hydroxide in the obtained solution, the concentration of quaternary ammonium hydroxide in the solution measured in the past operation record may be regarded as the concentration of quaternary ammonium hydroxide in the solution obtained in step (i).

The concentration of quaternary ammonium hydroxide in a solution can be accurately measured using commercially available measuring devices such as potentiometric titrators and liquid chromatographs. These measuring methods may be used alone or in combination. The sample used for the measurement may be a sample taken from the solution as is, or a diluted sample obtained by accurately diluting a sample taken from the solution with a solvent (e.g., water, etc.) may be used.

A potentiometric titrator is a device that performs measurements by the potentiometric titration method specified in JIS K0113. Potentiometric titrators that can perform measurements automatically are commercially available and can be preferably used. Potentiometric titration is an electrochemical measurement method that determines the equivalent point of volumetric analysis based on the change in the electrode potential difference between an indicator electrode and a reference electrode that responds to the concentration (activity) of the target component in the titrated solution.
A potentiometric titrator comprises a titration tank in which the solution to be titrated is placed, a burette for adding a standard solution to the titration tank, an indicator electrode and a reference electrode to be placed in the solution, and a potentiometer for measuring the potential difference between the two electrodes. Measurements using a potentiometric titrator are performed, for example, as follows. The solution to be titrated is placed in the titration tank, and an appropriate indicator electrode and reference electrode are inserted therein, and the potential difference between the two electrodes is measured by the potentiometer. Next, a predetermined amount of standard solution is dropped from the burette into the titration tank, and the solution to be titrated is reacted with the standard solution by stirring well, and then the potential difference between the two electrodes is measured. This operation is repeated to record the potential difference between the two electrodes corresponding to the amount of standard solution added, thereby obtaining a potential difference-standard solution added amount curve (hereinafter sometimes referred to as a "potentiometric titration curve"). The end point of the titration can be determined by determining the amount of standard solution added corresponding to the point where the potential difference changes suddenly on the obtained potentiometric titration curve. The concentration of the target component in the titrated solution can be calculated from the amount and concentration of the standard solution dropped by the end point of the titration, and the reaction molar ratio of the titration reaction. When measuring the concentration of quaternary ammonium hydroxide, an acid such as sulfuric acid or hydrochloric acid (for example, 1.0 normal or less) is usually used as the standard solution. When the solution contains only one type of quaternary ammonium hydroxide, the concentration of quaternary ammonium hydroxide (mol/L) in the solution can be measured quickly and easily by potentiometric titration. Even when the solution contains two or more types of quaternary ammonium hydroxide, the total concentration of quaternary ammonium hydroxide (mol/L) in the solution can be measured quickly and easily by potentiometric titration.

When the mixture ratio of quaternary ammonium hydroxide in a solution containing two or more kinds of quaternary ammonium hydroxide is unknown, the mixture molar ratio of quaternary ammonium hydroxide in the solution can be accurately measured by using liquid chromatography.For example, prepare a standard sample with a known concentration for each quaternary ammonium hydroxide (the quaternary ammonium hydroxide concentration (mol/L) in the standard sample can be accurately measured by potentiometric titration); perform liquid chromatography measurement for each mixture obtained by mixing the standard samples in a plurality of different mixture ratios, and plot the ratio of peak intensity in the chromatogram against the mixture ratio to create a calibration curve; perform liquid chromatography measurement for an organic solvent solution of quaternary ammonium hydroxide containing two or more kinds of quaternary ammonium hydroxide with unknown mixture ratio; use the calibration curve to determine the mixture molar ratio of quaternary ammonium hydroxide in the solution from the ratio of peak intensity in the chromatogram. The total concentration (mol/L) of quaternary ammonium hydroxides in a solution can be measured by potentiometric titration as described above. Therefore, by combining measurement by potentiometric titration with measurement by liquid chromatography, the concentration of each quaternary ammonium hydroxide in a solution containing two or more types of quaternary ammonium hydroxides can be accurately measured.
However, when the raw material mixture containing two or more kinds of quaternary ammonium hydroxides is prepared, the mixing ratio of the quaternary ammonium hydroxides in the raw material mixture is often known. Furthermore, even if the raw material mixture is subjected to thin film distillation in step (i), the quaternary ammonium hydroxides do not evaporate. Therefore, in practice, it is often not necessary to perform measurement by liquid chromatography.

The measurement method described above can also be applied to measuring the concentration of quaternary ammonium hydroxide in the composition according to the first aspect of the present invention, and to measuring the concentration of quaternary ammonium hydroxide in a raw material mixture.

(2.3 Step (iii): Dilution Step)
Step (iii) is a step of adjusting the concentration of quaternary ammonium hydroxide in the solution obtained in step (i) by adding an organic solvent to the solution obtained in step (i). That is, step (iii) is a step of diluting the solution obtained in step (i) with an organic solvent. Through steps (i) to (iii), a processing liquid composition for semiconductor manufacturing is produced.

2.3.1 Diluent Solvent
As the organic solvent used in step (iii) (hereinafter sometimes referred to as "dilution solvent"), an organic solvent that is miscible with the first organic solvent contained in the solution obtained in step (i) above can be used. A preferred example of the dilution solvent is the water-soluble organic solvent having a plurality of hydroxy groups (first organic solvent) described in section 1.1.2 above in relation to the solution producing method according to the first aspect of the present invention, and the preferred aspects thereof are the same as those described above. In one embodiment, the same water-soluble organic solvent as the first organic solvent contained in the solution obtained in step (i) can be particularly preferably used as the dilution solvent.
The composition produced by the composition production method according to the second aspect of the present invention may further contain, as a solvent, an organic solvent (second organic solvent) other than the water-soluble organic solvent having a plurality of hydroxyl groups, in addition to the water-soluble organic solvent (first organic solvent) having a plurality of hydroxyl groups. In order to obtain a composition containing such a second organic solvent, the first organic solvent and the second organic solvent may be used in combination as a dilution solvent in the step (iii). As the second organic solvent, for example, an organic solvent known as an organic solvent blended in a processing liquid composition for semiconductor manufacturing can be mentioned. As a preferred example of the second organic solvent, a water-soluble organic solvent (water-soluble monohydric alcohol) having only one hydroxyl group, such as methanol, ethanol, 1-propanol, 2-propanol, or n-butanol, can be mentioned. These water-soluble monohydric alcohols having only one hydroxyl group can be preferably used, for example, to adjust the viscosity of the composition.

The proportion of the first organic solvent in the total organic solvent in the composition produced by the composition production method of the present invention is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 95% by mass or more, and particularly preferably substantially 100% by mass, based on the total amount of organic solvent. Here, the fact that the first organic solvent accounts for "substantially 100% by mass" of the total organic solvent in the composition means that the total organic solvent in the composition consists only of the first organic solvent, or that the total organic solvent in the composition consists of the first organic solvent and unavoidable impurities.

In step (iii), the amount of each organic solvent constituting the dilution solvent to be added can be determined so that the concentration of each component in the composition produced falls within the desired range.

The water content in the dilution solvent is 1.0% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, based on the total amount of the dilution solvent. By having the water content in the dilution solvent be equal to or less than the above upper limit, it is possible to improve the performance of the resulting composition in removing modified photoresist and ashing residues of photoresist, and to reduce the corrosiveness to metal materials and inorganic substrate materials, for example, in applications such as stripping solutions and cleaning solutions. The lower limit of the water content in the dilution solvent is not particularly limited, but may be, for example, 0.05% by mass or more.

The content of metal impurities in the dilution solvent is 100 ppb by mass or less, preferably 50 ppb by mass or less, and more preferably 20 ppb by mass or less, for each of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn, based on the total amount of the dilution solvent. In this specification, the content of metal impurities in the dilution solvent means the total content of the metal element, regardless of whether it is a zero-valent metal or a metal ion.

The content of Cl (chlorine impurity) in the dilution solvent is 100 mass ppb or less, preferably 80 mass ppb or less, more preferably 50 mass ppb or less, based on the total amount of the dilution solvent. In this specification, the content of chlorine impurities in the dilution solvent means the total content of chlorine element. In the dilution solvent, the chlorine impurity is usually present in the form of chloride ion (Cl ^- ).

The metal impurity content in the dilution solvent can be measured using a microanalytical device such as an inductively coupled plasma mass spectrometer (ICP-MS). The chlorine impurity content can be measured using a microanalytical device such as ion chromatography.

(2.3.2 Dilution Conditions)
In step (iii), the amount of dilution solvent to be added to the solution obtained in step (i) can be determined from the concentration of quaternary ammonium hydroxide in the processing liquid composition for semiconductor manufacturing to be produced and the concentration of quaternary ammonium hydroxide in the solution obtained in step (i).

(2.4 Processing liquid composition for semiconductor manufacturing)
The treating liquid composition for semiconductor manufacturing produced by the composition producing method according to the second aspect of the present invention comprises the above-described water-soluble organic solvent having a plurality of hydroxy groups, and a quaternary ammonium hydroxide.

(2.4.1 Quaternary Ammonium Hydroxide Content)
In one embodiment, the content of quaternary ammonium hydroxide in the composition may be preferably 5.0% by mass or more, more preferably 8.0% by mass or more, based on the total amount of the composition. When the content of quaternary ammonium hydroxide in the composition is equal to or more than the above lower limit, the distribution cost of the composition can be saved. The upper limit of the content is not particularly limited, but may be 72% by mass or less in one embodiment, and 55% by mass or less in another embodiment. When the content of quaternary ammonium hydroxide in the composition is equal to or less than the above upper limit, the viscosity of the composition is suppressed from increasing, and handling, delivery, mixing, etc., when using the composition are facilitated.

The concentration of quaternary ammonium hydroxide in the composition can be accurately measured using a potentiometric titrator, liquid chromatography, etc. These measurement methods may be used alone or in combination.

In one embodiment, the content of quaternary ammonium hydroxide in the composition may be 2.38 to 25.0% by mass. In one preferred embodiment, TMAH may be used as the quaternary ammonium hydroxide, and the content of TMAH in the composition may be 2.38 to 25.0% by mass based on the total amount of the composition.

(2.4.2 Water content in the composition)
The water content in the composition is 1.0% by mass or less, preferably 0.5% by mass or less, more preferably 0.3% by mass or less, based on the total amount of the composition. By making the water content in the composition equal to or less than the upper limit, it is possible to improve the performance of removing modified photoresist and ashing residue of photoresist, and to reduce the corrosiveness to metal materials and inorganic substrate materials. The lower limit of the water content in the composition is not particularly limited, but may be, for example, 0.05% by mass or more.

The water content in the composition can be preferably measured by a method similar to that described in Section 1.4.2 above in relation to the solution production method according to the first aspect of the present invention.

The ratio of the water content (unit: mass %) in the composition to the quaternary ammonium hydroxide content (unit: mass %) in the composition (water content/quaternary ammonium hydroxide content) is preferably 0.42 or less, more preferably 0.21 or less, and even more preferably 0.10 or less. By having this ratio be equal to or less than the above upper limit, it becomes possible to further reduce corrosiveness to metal materials and inorganic substrate materials while maintaining or improving the performance of removing modified photoresist and ashing residues of photoresist. The lower limit of this ratio is not particularly limited, but may be, for example, 0.0007 or more.

2.4.3 Impurities in the composition
The content of metal impurities in the composition is 100 mass ppb or less, preferably 50 mass ppb or less, more preferably 20 mass ppb or less, based on the total amount of the composition, for each of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn. In this specification, the content of metal impurities in the composition means the total content of the metal element, regardless of whether it is a zero-valent metal or a metal ion.

The content of chlorine impurities (Cl) in the composition is 100 mass ppb or less, preferably 80 mass ppb or less, more preferably 50 mass ppb or less, based on the total amount of the composition. In this specification, the content of chlorine impurities in the composition means the total content of chlorine element. In the composition, the chlorine impurities are usually present in the form of chloride ions (Cl ^- ).

The content of metal impurities in the composition can be measured using a microanalytical device such as an inductively coupled plasma mass spectrometer (ICP-MS). The content of chlorine impurities can be measured using a microanalytical device such as ion chromatography.

The ratio of the content of the above metal impurities in the composition (unit: mass ppb) to the content of quaternary ammonium hydroxide in the composition (unit: mass %) (content of metal impurities/content of quaternary ammonium hydroxide) is preferably 42 or less, more preferably 21 or less, and even more preferably 10 or less for each of the above metal elements. By having this ratio be equal to or less than the above upper limit, it becomes possible to further increase the manufacturing yield of semiconductor devices while maintaining or improving the removal performance of the modified photoresist and the ashing residue of the photoresist. There is no particular restriction on the lower limit of this ratio, and the lower the better, but taking into account the quantitative limit of the measuring device for metal impurities, it may be, for example, 0.0001 or more.

The ratio (chlorine content/quaternary ammonium hydroxide content) of the content of chlorine impurities in the composition (unit: mass ppb) to the content of quaternary ammonium hydroxide in the composition (unit: mass %) is preferably 42 or less, more preferably 34 or less, and even more preferably 21 or less. By keeping this ratio below the upper limit, it becomes possible to further increase the manufacturing yield of semiconductor devices while maintaining or improving the performance of removing modified photoresist and ashing residues of photoresist. There is no particular lower limit for this ratio, and the lower the better, but taking into account the quantitative limit of the measuring device for chlorine impurities, it may be, for example, 0.001 or more.

2.4.4 Uses
The composition produced by the composition production method of the present invention can be preferably used as a chemical liquid such as a developer for photoresist, a stripping liquid or cleaning liquid for modified resist, or a silicon etching liquid used in the production process of semiconductor devices.

In the field of semiconductor manufacturing, not only the various chemical solutions themselves but also the concentrated solutions used to prepare the various chemical solutions by diluting them with a solvent or the like are referred to as processing solutions. In this specification, not only compositions having a concentration that can be used as the various chemical solutions as they are, but also concentrated solutions that are based on such dilution are considered to fall under the category of "processing solution composition for semiconductor manufacturing". The composition obtained by the composition manufacturing method of the present invention can be preferably used as the concentrated solution. For example, a chemical solution having a desired quaternary ammonium hydroxide concentration and solvent composition can be obtained by diluting (adjusting the concentration) the composition obtained by the composition manufacturing method of the present invention with the first organic solvent, the second organic solvent, water, or an aqueous solution of quaternary ammonium hydroxide, or a combination thereof.

The composition production method of the present invention described above can also be applied to the production of a composition (chemical solution) modified so that the water content exceeds 1.0 mass% based on the total amount of the composition, such as the etching solution described in Section 1.4.4 above. In step (iii) (dilution step) described in Section 2.3 above, a composition modified so that the water content exceeds 1.0 mass% based on the total amount of the composition can be produced by further adding an amount of water (e.g., ultrapure water, etc.) as necessary. In such a modified production method, the organic solvent (dilution solvent) used in step (iii) (dilution step) may have a water content of more than 1.0 mass%, as long as the concentrations of metal impurities and chlorine impurities are within the ranges described in Section 2.3.1 above.

The present invention will be described in more detail below using examples and comparative examples. However, the following examples are merely examples for explaining the present invention, and the present invention is not limited to these examples.

(Measuring method)
In the examples and comparative examples, the concentration of quaternary ammonium hydroxide in the solution was measured by potentiometric titration using an automatic potentiometric titrator AT-610 (manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

The water content in the resulting solution was obtained by correcting the value measured by Karl Fischer titration using a calibration curve. The water content was measured by Karl Fischer titration using a Karl Fischer moisture meter MKA-510 (Kyoto Electronics Manufacturing Co., Ltd.). The water content was measured by gas chromatography (hereinafter sometimes simply referred to as "GC") using a Shimadzu gas chromatograph GC-2014 (column: DB-WAX (Agilent Technologies), detector: thermal conductivity detector).

The water content measured by Karl Fischer titration was corrected using a calibration curve according to the following steps (1) to (6).
(1) The amount of water in the same organic solvent as the organic solvent in the solution to be measured (propylene glycol if the organic solvent in the solution is propylene glycol (PG), or hexylene glycol if the organic solvent in the solution is hexylene glycol (HG)) was measured by Karl Fischer titration. Then, five types of solutions with different amounts of water (hereinafter sometimes referred to as "water/organic solvent solutions") were prepared by adding a small amount of water to the organic solvent. The amount of water added to the organic solvent was selected so that the water content in the water/organic solvent solution would be five levels from 0.25 to 5.0% by mass (0.25% by mass, 0.50% by mass, 1.0% by mass, 2.0% by mass, and 5.0% by mass). The amount of water in the five types of water/organic solvent solutions prepared was measured by Karl Fischer titration, and it was confirmed that the obtained value showed good agreement with the theoretical value calculated from the water content in the organic solvent and the amount of water added.
(2) Each of the five water/organic solvent solutions prepared in (1) above was analyzed by gas chromatography (GC) to obtain a GC chart containing water and organic solvent peaks. The area of the water peak in the obtained GC chart was plotted on the vertical axis (Y) and the amount of water in the water/organic solvent solution (theoretical value calculated from the amount of water in the organic solvent and the amount of water added) on the horizontal axis (X), and the two showed a good linear correlation. A regression line was calculated by the least squares method using Y as the objective variable and X as the explanatory variable to obtain a calibration curve (first calibration curve) that gives the amount of water from the area of the water peak in the GC chart.
(3) Five types of mixed solutions were prepared as standard solutions by adding a small amount of concentrated aqueous solution of the same quaternary ammonium hydroxide (QAH) as the QAH in the solution to be measured (25% by mass TMAH aqueous solution if the QAH in the solution is TMAH, 20% by mass TEAH aqueous solution if the QAH in the solution is TEAH, 10% by mass TPAH aqueous solution if the QAH in the solution is TPAH, and 10% by mass TBAH aqueous solution if the QAH in the solution is TBAH) to the same organic solvent as the organic solvent in the solution to be measured. The water content in the organic solvent was accurately measured by Karl Fischer titration in (1) above. The QAH concentration in the concentrated QAH aqueous solution was accurately measured by an automatic potentiometric titrator (the water content in the concentrated QAH aqueous solution was also determined at the same time). The mixing mass ratio of the organic solvent and the concentrated QAH aqueous solution was selected so that the water content in the mixed solution was in the five stages of 0.25 to 5.0% by mass, the same as in (1) above.
(4) The water content in the standard solution was measured by GC. That is, the five kinds of standard solutions prepared in (3) above were analyzed by gas chromatography, and the water content in each standard solution was obtained from the area of the water peak in the GC chart using the first calibration curve obtained in (2) above. It was confirmed that the measured water content by GC showed good agreement with the theoretical value of the water content in the standard solution calculated from the water content in the organic solvent, the water content in the concentrated QAH aqueous solution, and the mixture mass ratio of the organic solvent and the concentrated QAH aqueous solution.
(5) The water content of each of the five standard solutions prepared in (3) above was measured by Karl Fischer titration. For each standard solution, the water content measured by Karl Fischer titration was plotted on the vertical axis (Y) and the water content in the standard solution measured by GC in (3) above was plotted on the horizontal axis (X). A regression line was calculated by the least squares method using Y as the objective variable and X as the explanatory variable, to obtain a calibration curve (second calibration curve) for correcting the water content measurement value by Karl Fischer titration to the water content measurement value by GC for the organic solvent solution containing QAH and water.
(6) The water content of the actual solution to be measured was measured by Karl Fischer titration, and the measured value was corrected to the water content measured by GC using the second calibration curve obtained in (5) above.

The content of each metal impurity in the obtained solution was measured by inductively coupled plasma mass spectrometry (ICP-MS) using an Agilent Technologies ICP-MS 7500cx. The amount of chloride ions in the obtained solution was measured by ion exchange chromatography using a Thermo Fisher Scientific ion chromatography ICS-1100 (column: Dionex (registered trademark) Ionpac (registered trademark) AS7 anion exchange column, eluent: additive-containing NaOH aqueous solution, detector: electrical conductivity detector) after pretreating the solution using a cation removal pretreatment cartridge.

(Thin film distillation apparatus)
As the thin-film distillation apparatus, a commercially available falling-film type short-path thin-film distillation apparatus (UIC Corporation, KD-10, heat transfer area 0.1 m ² ) was used either as purchased or after modification. The apparatus configuration in each example and comparative example is as follows:

Apparatus C: As shown in FIG. 4 (thin film distillation apparatus 10C), from the upstream side, it has a raw material container 31, a valve 32, a pipe 3, a raw material gear pump 4, a preheater 5, a degasser 6, an evaporation container (including a roller wiper 21 and an internal condenser 22) 37, glass pipes 8 and 9 for checking flow rates (residue liquid side and distillate side), gear pumps 10 and 11 (residue liquid side and distillate side), a residue liquid recovery container 12, a distillate recovery container 13, a vacuum pump (rotary pump and roots pump) 15, a cold trap 14, and other pipes and valves connecting them.

Regarding the materials of the liquid-contacting parts in the device C, the roller wiper 21 is made of a composite material of PTFE and glass fiber, the other liquid-contacting parts are made of stainless steel (SUS304, SUS316L, SUS316Ti, SUS630 or equivalent), and the residual liquid recovery container 12 and the distillate recovery container 13 are made of PE. The area of the heating surface 24 is 0.1 ^m2 .

Apparatus A: As shown in Figure 1 (thin film distillation apparatus 10A), the raw material gear pump 4, preheater 5, and degasser 6 were removed from the configuration of apparatus C, and the valve 32 was changed to a needle valve.

As for the materials of the liquid-contacting parts in device A, the raw material container 31 was made of PE, the piping 33 was made of PFA, and the flow rate adjusting needle valve 32 was made of PTFE. In addition, the material of the roller wiper 21 inside the evaporation container 37 was changed from a composite material of PTFE and glass fiber to PEEK (without glass fiber).

Small samples were cut from the PE, PFA, PTFE, and PEEK resins used in the liquid-contacting parts of device A, decomposed, and the metal impurities of Na, Ca, Al, and Fe in each resin were measured using ICP-MS, and all were found to be below 1 ppm by mass.

Apparatus B: As shown in Figure 3 (thin film distillation apparatus 10B), the glass pipe 8 for checking the flow rate (on the residue liquid side) was removed from apparatus A. In addition, the pipes 38 from the outlet of the evaporation vessel 37 to the residue liquid recovery vessel 12 and the distillate recovery vessel 13 were each made of PFA.

In each of the devices A to C, the degree of vacuum within the system was measured using a vacuum gauge (not shown) installed between the cold trap 14 and the vacuum pump 15.

The abbreviations and sources of materials used in each of the examples and comparative examples are as follows.
25% by mass TMAH aqueous solution: Tetramethylammonium hydroxide (TMAH) aqueous solution having a TMAH concentration of 25% by mass (manufactured by Tokuyama)
PG: Propylene glycol (AGC)
HG: Hexylene glycol (Mitsui Chemicals)

In addition, TEAH aqueous solution, TPAH aqueous solution, and TBAH aqueous solution (all manufactured by Wako Pure Chemical Industries, Ltd.) were each purified by a two-tank electrolysis method using an aqueous solution system to prepare a TEAH aqueous solution with a TEAH concentration of 20% by mass (20% by mass TEAH aqueous solution), a TPAH aqueous solution with a TPAH concentration of 10% by mass (10% by mass TPAH aqueous solution), and a TBAH aqueous solution with a TBAH concentration of 10% by mass (10% by mass TBAH aqueous solution), which were used as the raw material quaternary ammonium hydroxide aqueous solution. In addition, the raw material quaternary ammonium hydroxide aqueous solution and the water-soluble organic solvent were stored in a room at room temperature of 23°C, and then used to prepare the raw material mixture.

The metal impurity contents of the raw material mixtures used in each Example and Comparative Example are shown in Table 1. In Table 1, "<1" means that the value was less than 1 ppb by mass.

<Comparative Example 1>
A solution of quaternary ammonium hydroxide in an organic solvent was produced by thin-film distillation using apparatus C (thin-film distillation apparatus 10C (FIG. 4)).

The piping of the device was disassembled, cleaned, and reassembled, and then cleaned by alternately passing an aqueous TMAH solution with a TMAH concentration of 25% by mass and ultrapure water twice each.

A raw material mixture prepared by mixing 4 kg of 25% by mass TMAH aqueous solution and 20 kg of PG in a PE clean bottle was placed in a raw material container made of SUS304 (TMAH aqueous solution/PG mixed mass ratio = 1/5). Thin film distillation was performed under the conditions of a preheater temperature of 70°C, a temperature of the raw material mixture immediately before entering the distillation container of 68°C, a temperature of the heating surface of the evaporation container (heat medium temperature) of 100°C, a vacuum degree of 1900 Pa, and a feed rate of 7.0 kg/hour (feed rate per unit area of the heating surface: 70 kg/hour·m ² ), and a PG solution (about 8 kg) containing TMAH was obtained in a residual liquid recovery container. Each condition is shown in Table 2. In Table 2, the "mixing ratio" of the raw material mixture means the mixing mass ratio of the quaternary ammonium hydroxide aqueous solution and the water-soluble organic solvent (quaternary ammonium hydroxide aqueous solution/water-soluble organic solvent). The TMAH concentration, water content, content of each metal impurity, and chloride ion content in the obtained solution are shown in Table 3. In Table 3, "TXAH concentration" means the concentration of quaternary ammonium hydroxide, and "<1" means that the value was less than 1 ppb by mass.

Example 1
An organic solvent solution of quaternary ammonium hydroxide was produced by thin-film distillation (step (a)) using apparatus A (thin-film distillation apparatus 10A (FIG. 1)).

The piping of the device was disassembled, cleaned, and reassembled in advance, and then cleaned by alternately passing an aqueous TMAH solution with a TMAH concentration of 25% by mass and ultrapure water twice each (step (b)).

A raw material mixture prepared by mixing 4 kg of 25% by mass TMAH aqueous solution and 16 kg of PG in a PE clean bottle was placed in a PE raw material container (TMAH aqueous solution/PG mixture mass ratio = 1/4). Thin film distillation was carried out under the following conditions: the temperature of the raw material mixture immediately before entering the distillation container was 23°C, the temperature of the heating surface of the evaporation container (heat medium temperature) was 100°C, the vacuum degree was 600 Pa, and the feed rate was 10.0 kg/hour (feed rate per unit area of the heating surface: 100 kg/hour·m ² ), to obtain a PG solution (about 5 kg) containing TMAH in the residual liquid recovery container (step (a)). The conditions and results are shown in Tables 2 and 3, respectively.

Example 2
Using apparatus A (thin film distillation apparatus 10A (FIG. 1)), the same apparatus cleaning (step (b)) as in Example 1 was carried out, and then thin film distillation (step (a)) was carried out to produce a solution of quaternary ammonium hydroxide in an organic solvent.

A raw material mixture prepared by mixing 4 kg of 25% by mass TMAH aqueous solution and 16 kg of PG in a PE clean bottle was placed in a PE raw material container (TMAH aqueous solution/PG mixture mass ratio = 1/4). Thin film distillation was carried out under the following conditions: the temperature of the raw material mixture immediately before entering the distillation container was 23°C, the temperature of the heating surface of the evaporation container (heat medium temperature) was 105°C, the vacuum degree was 500 Pa, and the feed rate was 7.0 kg/hour (feed rate per unit area of the heating surface: 70 kg/hour·m ² ), and a PG solution (about 4 kg) containing TMAH was obtained in a residue liquid recovery container. The conditions and results are shown in Tables 2 and 3, respectively.

Example 3
Using apparatus B (thin film distillation apparatus 10B (FIG. 3)), the same apparatus cleaning (step (b)) as in Example 1 was carried out, and then thin film distillation (step (a)) was carried out to produce a solution of quaternary ammonium hydroxide in an organic solvent.

A raw material mixture prepared by mixing 4 kg of 25 mass% TMAH aqueous solution and 16 kg of PG in a PE clean bottle was placed in a PE raw material container (TMAH aqueous solution/PG mixture mass ratio = 1/4). Thin film distillation was carried out under the following conditions: the temperature of the raw material mixture immediately before entering the distillation container was 23°C, the temperature of the heating surface of the evaporation container (heat medium temperature) was 105°C, the vacuum degree was 500 Pa, and the feed rate was 5.0 kg/hour (feed rate per unit area of the heating surface: 50 kg/hour·m ² ), and a PG solution (about 4 kg) containing TMAH was obtained in the residual liquid recovery container. The conditions and results are shown in Tables 2 and 3, respectively.

Example 4
A PG solution (about 3 kg) containing TMAH was obtained in a residual liquid recovery vessel by performing thin-film distillation in the same manner as in Example 3, except that the degree of vacuum was set to 300 Pa. The conditions and results are shown in Tables 2 and 3, respectively.

Example 5
Thin-film distillation was carried out in the same manner as in Example 3, except that the heating surface temperature (heat medium temperature) was 80° C., the vacuum degree was 16 Pa, and the feed rate was 2.5 kg/hour (feed rate per unit area of the heating surface: 25 kg/hour·m ² ), to obtain a PG solution (about 4 kg) containing TMAH in the residue liquid recovery vessel. The conditions and results are shown in Tables 2 and 3, respectively.

Example 6
Using apparatus B (thin film distillation apparatus 10B (FIG. 3)), the same apparatus cleaning as in Example 1 was carried out (step (b)), and then thin film distillation (step (a)) was carried out to produce a solution of quaternary ammonium hydroxide in an organic solvent.

A raw material mixture prepared by mixing 4 kg of 25 mass% TMAH aqueous solution and 8 kg of PG in a PE clean bottle was placed in a PE raw material container (TMAH aqueous solution/PG mixture mass ratio = 1/2). Thin film distillation was carried out under the following conditions: the temperature of the raw material mixture immediately before entering the distillation container was 23°C, the temperature of the heating surface of the evaporation container (heat medium temperature) was 105°C, the vacuum degree was 16 Pa, and the feed rate was 2.5 kg/hour (feed rate per unit area of the heating surface: 25 kg/hour· ^m2 ), and a PG solution (about 3 kg) containing TMAH was obtained in a residue liquid recovery container. The conditions and results are shown in Tables 2 and 3, respectively.

Example 7
Using apparatus B (thin film distillation apparatus 10B (FIG. 3)), the same apparatus cleaning (step (b)) as in Example 1 was carried out, and then thin film distillation (step (a)) was carried out to produce a solution of quaternary ammonium hydroxide in an organic solvent.

A raw material mixture prepared by mixing 4 kg of 25 mass% TMAH aqueous solution and 16 kg of HG in a PE clean bottle was placed in a PE raw material container (TMAH aqueous solution/HG mixture mass ratio = 1/4). Thin film distillation was carried out under the following conditions: temperature of the raw material mixture immediately before entering the distillation container: 23°C, temperature of the heating surface of the evaporation container (heat medium temperature): 105°C, degree of vacuum: 500 Pa, feed rate: 7.0 kg/hour (feed rate per unit area of the heating surface: 70 kg/hour·m ² ), and a HG solution (about 4 kg) containing TMAH was obtained in a residue liquid recovery container. The conditions and results are shown in Tables 2 and 3, respectively.

Example 8
Using the apparatus B (thin film distillation apparatus 10B (FIG. 3)), cleaning of the apparatus was carried out in the same manner as in Example 1 (step (b)). However, instead of the TMAH aqueous solution, a 20% by mass TEAH aqueous solution was used as the cleaning liquid. Then, thin film distillation (step (a)) was carried out in the following manner to produce an organic solvent solution of quaternary ammonium hydroxide.

A raw material mixture prepared by mixing 4 kg of 20% by mass TEAH aqueous solution and 16 kg of PG in a PE clean bottle was placed in a PE raw material container (TEAH aqueous solution/PG mixture mass ratio = 1/4). Thin film distillation was carried out under the following conditions: temperature of the raw material mixture immediately before entering the distillation container: 23°C, temperature of the heating surface of the evaporation container (heat medium temperature): 105°C, degree of vacuum: 100 Pa, feed rate: 5.0 kg/hour (feed rate per unit area of the heating surface: 50 kg/hour·m ² ), and a PG solution (about 4 kg) containing TEAH was obtained in a residue liquid recovery container. The conditions and results are shown in Tables 2 and 3, respectively.

<Examples 9 and 10>
Thin-film distillation was carried out in the same manner as in Example 8, except that the TEAH aqueous solution used for washing and preparation of the raw material mixture was changed to a 10% by mass TPAH aqueous solution (Example 9) or a 10% by mass TBAH aqueous solution (Example 10), and a PG solution containing TPAH (about 4 kg) or a PG solution containing TBAH (about 4 kg) was obtained in a residue liquid recovery vessel. The conditions and results are shown in Tables 2 and 3, respectively.

The TMAH PG solution obtained in Comparative Example 1 contained metal impurities, Na, Ca, and Fe, exceeding 100 ppb by mass, and also contained chlorine impurities exceeding 100 ppb by mass.
In Examples 1 to 10, various quaternary ammonium hydroxides were used to obtain high-purity organic solvent solutions of quaternary ammonium hydroxide with a water content of 1.0% by mass or less, metal impurities of 100 ppb by mass or less, and chlorine impurities of 100 ppb by mass or less. Such high-purity organic solvent solutions of quaternary ammonium hydroxide were not previously obtained. Depending on the conditions of thin-film distillation, it was also possible to obtain a water content of 0.3% by mass or less, metal impurities of 20 ppb by mass or less, and chlorine impurities of 50 ppb by mass or less (Examples 5-6). The organic solvent solutions of quaternary ammonium hydroxide obtained in Examples 1 to 10 above had a concentration and purity that allowed them to be used as a treatment liquid composition for semiconductor manufacturing as they are. It is also possible to obtain a treatment liquid composition for semiconductor manufacturing by further subjecting the organic solvent solutions of quaternary ammonium hydroxide obtained in Examples 1 to 10 above to the step (iii) of the composition production method according to the second aspect of the present invention described above (see Section 2.3 above).

3, 33 Raw material pipe 4 Raw material gear pump 5 Preheater (preheater)
6. Degasser
8, 9 Glass pipe for checking flow rate 10 Liquid delivery pump ((residue liquid side) gear pump)
11 Liquid delivery pump ((distillate side) gear pump)
12 Residual liquid recovery container 13 Distillate recovery container 14 Cold trap 15 Vacuum pump 21 Wiper (roller wiper)
22 Condenser (internal condenser)
23 Raw material mixture 24 Heating surface 25 (circulating) heat medium 26 (circulating) coolant 31 Raw material container 32 Valve (needle valve)
37 Evaporation vessel 38 Piping

Claims (12)

1. A method for preparing a solution of a quaternary ammonium hydroxide in an organic solvent, comprising the steps of:
(a) subjecting the raw material mixture to thin-film distillation using a falling film type thin-film distillation apparatus,
The raw material mixture contains quaternary ammonium hydroxide, water, and a first organic solvent capable of dissolving the quaternary ammonium hydroxide,
the first organic solvent is a water-soluble organic solvent having a plurality of hydroxy groups,
The thin film distillation apparatus comprises:
An evaporation vessel;
A raw material container for storing the raw material mixture;
a raw material pipe for transferring the raw material mixture from the raw material container to the evaporation container;
a first flow path that introduces the raw material mixture into the evaporation container from an upper portion of the evaporation container;
Equipped with
a liquid-contacting portion of an inner surface of the raw material container and a liquid-contacting portion of the raw material pipe are made of resin,
the raw material mixture introduced into the evaporation vessel from the first flow path flows down along an inner wall surface of the evaporation vessel in the form of a liquid film,
The thin film distillation apparatus further comprises:
a heating surface disposed on the inner wall surface for heating the liquid film flowing down along the inner wall surface;
a condenser disposed inside the evaporation container to cool and liquefy the vapor generated from the liquid film;
a second flow path for recovering the distillate liquefied by the condenser from the evaporation vessel;
a third flow path for recovering from the evaporation container a residual liquid that does not evaporate on the heating surface and flows down from the heating surface;
The thin film distillation
the temperature of the raw material mixture immediately before entering the evaporation vessel is a first temperature of 70° C. or less;
the temperature of the heating surface is a second temperature of 60 to 140° C., the second temperature being higher than the first temperature;
a feed rate of the raw material mixture to the evaporation vessel is 10 to 100 kg/hr· ^m2 in terms of a feed rate per unit area of the heating surface;
A method for producing an organic solvent solution of quaternary ammonium hydroxide, characterized in that the method is carried out under conditions in which the degree of vacuum in the evaporation vessel is 600 Pa or less. The thin film distillation apparatus comprises:
The evaporation container further includes a wiper that is disposed in the evaporation container and rotates along the inner wall surface.
2. The method for producing an organic solvent solution of quaternary ammonium hydroxide according to claim 1, wherein the raw material mixture introduced into the evaporation container from the first flow path is applied to the inner wall surface by the wiper to form the liquid film. The first organic solvent is one or more organic solvents selected from dihydric alcohols and trihydric alcohols consisting of carbon atoms, hydrogen atoms, and oxygen atoms and having a boiling point of 150 to 300° C.;
A method for producing the organic solvent solution of the quaternary ammonium hydroxide according to claim 1 or 2. The raw material mixture is, based on the total amount of the mixture,
The first organic solvent is 40 to 85% by mass,
The quaternary ammonium hydroxide is 2.0 to 30% by mass,
The method for producing an organic solvent solution of a quaternary ammonium hydroxide according to any one of claims 1 to 3, wherein the water is contained in an amount of 10 to 30 mass%. the contents of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn in the raw material mixture are each 50 ppb or less based on the total amount of the raw material mixture,
The Cl content in the raw material mixture is 50 ppb or less based on the total amount of the raw material mixture.
A method for producing an organic solvent solution of the quaternary ammonium hydroxide according to any one of claims 1 to 4. A method for producing a processing liquid composition for semiconductor manufacturing, comprising the steps of:
(i) obtaining a solution of a quaternary ammonium hydroxide in an organic solvent by the method according to any one of claims 1 to 5;
(ii) determining the concentration of the quaternary ammonium hydroxide in the organic solvent solution; and (iii) adjusting the concentration of the quaternary ammonium hydroxide in the organic solvent solution by adding to the organic solvent solution an organic solvent having a water content of 1.0 mass% or less, a content of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn of 100 mass% or less, and a content of Cl of 100 mass% or less, based on the total amount of the solvent,
The composition comprises the quaternary ammonium hydroxide and the first organic solvent,
The water content in the composition is 1.0% by mass or less based on the total amount of the composition,
The content of Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn in the composition is 100 ppb by mass or less, based on the total amount of the composition;
The Cl content in the composition is 100 ppb by mass or less based on the total amount of the composition.
A method for producing a processing liquid composition for semiconductor manufacturing. In the step (iii), the content of the quaternary ammonium hydroxide in the organic solvent solution is adjusted to 5.0 mass% or more based on the total amount of the solution.
A method for producing the processing liquid composition for semiconductor manufacturing according to claim 6. In the step (iii), the content of the quaternary ammonium hydroxide in the organic solvent solution is adjusted to 2.38 to 25.0 mass% based on the total amount of the solution.
A method for producing the processing liquid composition for semiconductor manufacturing according to claim 6. the ratio of the water content (unit: mass%) in the composition to the quaternary ammonium hydroxide content (unit: mass%) in the composition (water/quaternary ammonium hydroxide) is 0.42 or less;
A method for producing the processing liquid composition for semiconductor manufacturing according to any one of claims 6 to 8. the ratio of the Na content (unit: mass ppb) in the composition to the quaternary ammonium hydroxide content (unit: mass%) in the composition (Na content/quaternary ammonium hydroxide content) is 42 or less;
A method for producing the processing liquid composition for semiconductor manufacturing according to any one of claims 6 to 9. the ratio of the Ca content (unit: mass ppb) in the composition to the quaternary ammonium hydroxide content (unit: mass%) in the composition (Ca content/quaternary ammonium hydroxide content) is 42 or less;
A method for producing the treating liquid composition for semiconductor manufacturing according to any one of claims 6 to 10. the ratio of the Cl content (unit: mass ppb) in the composition to the quaternary ammonium hydroxide content (unit: mass%) in the composition (Cl content/quaternary ammonium hydroxide content) is 42 or less;
A method for producing the treating liquid composition for semiconductor manufacturing according to any one of claims 6 to 11.

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