Method for purifying organic solvent and purification apparatus

Abstract

Provided are a purification method and purification apparatus that deplete the metal impurities in an organic solvent. This organic solvent purification method is a purification method that depletes the metal impurities in an organic solvent, said organic solvent purification method is characterized by comprising: a filtration step for filtering the organic solvent with a particle removal filter; and an ion-exchange step for passing the organic solvent yielded by the filtration step through an ion exchanger.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for purifying an organic solvent.

Background Art

[0002] Semiconductor devices are manufactured through hundreds of complex processes. The line width of a semiconductor device is determined by a photoresist process. The photoresist process includes a process of applying a resist to a silicon wafer, an exposure process of irradiating light with a short wavelength from a light source through a mask, and a process of developing a resist mask. Further, it includes a process of etching an exposed portion through the resist mask and a process of peeling off the resist mask. The resist applied to the wafer is a composition in which an acid generator, a resin solution, and an additive are dissolved in an organic solvent. As the organic solvent, those containing PGMEA (propylene glycol monomethyl ether acetate) or PGME (propylene glycol monomethyl ether) as main components are used. In addition, various organic solvents are also used in a developer, a rinse solution, a stripping solution, a chemical mechanical polishing (CMP) slurry, and a cleaning solution after CMP.

[0003] In recent years, for the promotion of miniaturization and high functionality technologies of IT devices, further miniaturization of the line width of semiconductor devices has been required. However, when the line width is miniaturized, even a small amount of impurities may have an adverse effect on the semiconductor device. In particular, when a large amount of metal elements remain among the impurities contained in the organic solvent, the metal elements adhere to the wafer, leading to a deterioration in the performance of the semiconductor device. Therefore, it is inevitable to reduce the metal elements in the organic solvent.

[0004] Patent Document 1 discloses a purifier for removing Cr from an organic solvent. The purifier includes an ion exchange resin and a porous membrane downstream of the ion exchange resin in a housing having a fluid inlet and a fluid outlet in fluid communication therewith.

[0005] In Patent Document 2, in order to efficiently remove metal ions in the water to be treated, a depth filter including a porous molded body which is a sintered product of a mixed powder containing a dry gel powder and a thermoplastic resin powder or a swollen body thereof is disclosed.

[0006] In Patent Document 3, a method for producing a chemical solution is disclosed, which includes a filtration step of filtering a product to be purified, an ion removal step of subjecting the product to be purified to an ion exchange method or ion adsorption by a chelating group, and a distillation step of distilling the product to be purified, in any order. This is to provide a chemical solution having excellent defect suppression performance when used in the manufacturing process of semiconductor devices even after long-term storage. In the examples, it is described that a purification apparatus is installed in the order of a distillation step, an ion removal step using an ion exchange resin, a distillation step, and a filtration step using a filter.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the inventors of the present invention have clarified that even if a particle removal filter is installed downstream of the ion exchange resin as in Patent Document 1 or Patent Document 3 and an attempt is made to remove metal elements in the organic solvent by purifying the organic solvent, it may not be possible to reduce metal elements, particularly Cr.

[0009] Therefore, an object of the present invention is to provide a purification method and a purification apparatus for reducing metal impurities in an organic solvent.

Means for Solving the Problems

[0010] As a result of intensive studies by the present inventors, by installing a slow particle filter in the front stage of the ion exchange resin, solid metal impurities in the organic solvent were removed in advance by the particle removal filter. Thereafter, it has been found that reduction of metal elements, particularly Cr, becomes possible by treating the organic solvent with the ion exchange resin.

[0011] The present invention is a purification method for reducing metal impurities in an organic solvent, comprising a filtration step of filtering the organic solvent of the liquid to be treated with a particle removal filter, and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger. It is a purification method for an organic solvent, characterized by including the above.

[0012] Further, the present invention is a purification apparatus for reducing metal impurities in an organic solvent, comprising a particle removal filter for filtering the organic solvent, and an ion exchange means for purifying the organic solvent obtained after the filtration by passing it through an ion exchanger. It is a purification apparatus for an organic solvent, characterized by including the above.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a purification method and a purification apparatus for reducing metal impurities in an organic solvent.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0015] The purification method for reducing metal impurities in an organic solvent according to the present invention has a filtration step of filtering the organic solvent of the liquid to be treated with a particle removal filter, and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger.

[0016] (organic solvent) In the present invention, the organic solvent to be purified is not particularly limited as long as it is an organic solvent used in the manufacturing process of electronic devices such as semiconductor devices, but an EL-grade organic solvent is preferred. According to the studies of the present inventors, even in the case of EL-grade organic solvents, metal impurities in IPA (isopropyl alcohol) and thinner (PGMEA / PGME) can be removed by an ion-exchange resin. However, it has been found that in the case of PGMEA alone and in the case of nBA (normal butyl acetate), the removal of metal impurities, particularly Cr, is insufficient only by an ion-exchange resin. As disclosed in the background art, even if a particle-removing filter is provided after the ion-exchange step, Cr ions remain in the organic solvent. From this, it is presumed that in these solvents, due to the contact between the ion-exchange resin and particulate Cr, Cr has changed into a form in which it is difficult to be removed by the filter. This phenomenon is not limited to PGMEA and nBA, and can also occur in organic solvents having solubility parameters (SP values) close to these. The SP value of PGMEA is 19.26 (MPa) 0.5 and the SP value of nBA is 17.41 (MPa) 0.5 . In solvents having an SP value of 20 or less, the effects of the present invention are more exerted. The SP value is a value cited from "Hansen Solubility Parameters: A User’s Handbook, Second Edition, published in 2007".

[0017] In the stage prior to purification, the upper limit of the concentration of each metal element in the organic solvent is not particularly limited. For example, EL grade PGMEA manufactured by Tokyo Ohka Kogyo Co., Ltd. contains Na, Ca, Cr, and Fe as metal impurities, and the concentration of each is 100 ppt or less. In addition, Kanto Chemical Co., Inc.'s Raku Special Grade PGMEA contains Na, Ca, Cr, Fe, Ni, Cu, and Zn. The concentration of Na is 10 ppb or less, and the concentration of Ca, Cr, Fe, Ni, Cu, and Zn is 200 ppt or less. The lower limit is above the target concentration for purification, specifically above the detection limit of concentration measurement. Examples of metal impurities contained in the organic solvent include Li, Na, Mg, Al, K, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sr, Ag, Cd, Ba, Pb, etc. In the purification method and production apparatus of the present invention, Cr can be particularly reduced.

[0018] (Particle removal filter) The particle removal filter is not particularly limited as long as it can remove metal impurity particles. Preferably, the pore diameter on the surface is 1000 nm or less, and more preferably 100 nm or less. The lower limit of the pore diameter is preferably at a level where the pressure load on the apparatus is not a problem, preferably 2 nm or more, and more preferably 5 nm or more. Here, the pore diameter indicates the average value of the pore diameters of the porous membrane and is measured by the bubble point method using IPA or HFE-7200 (manufactured by 3M). The material of the particle removal filter is not particularly limited as long as it is resistant to the organic solvent to be purified. Specifically, PE (polyethylene), UPE (ultra-high molecular weight polyethylene), PTFE (polytetrafluoroethylene), PI (polyimide), PAI (polyamideimide), etc. can be mentioned. In addition, in order to avoid elution of metal elements from the particle removal filter, it is preferable to wash the particle removal filter with a solvent containing no metal elements before use, and then confirm by measurement that there is no metal elution from the particle removal filter before use.

[0019] (Ion exchanger) The ion exchanger of the present invention is not particularly limited as long as it is a substance that exhibits an ion exchange phenomenon, but is preferably an ion exchange resin. Examples of ion exchange resins include chelating resins, cation exchange resins, and anion exchange resins, and any of these resins may be used in the present invention. In addition, the ion exchanger of the present invention includes a monolithic ion exchanger composed of a continuous skeleton and continuous pores.

[0020] Before use, chelating resins and cation exchange resins preferably have a content of metal impurities of 1 mg / L or less and are purified by contacting them with a mineral acid solution having a concentration of 5% by mass or more to obtain a purified ion exchange resin. Examples of mineral acids include hydrochloric acid, sulfuric acid, and nitric acid.

[0021] Furthermore, when hydrochloric acid with a concentration of 3% by mass is passed through the purified ion exchange resin in a volume ratio of 25 times, the total amount of eluted metal impurities eluted is preferably 5 μg / mL-R or less. Here, "a volume ratio of 25 times" means passing hydrochloric acid with a volume 25 times that of the ion exchange resin. The unit " / mL-R" means "per 1 mL of the volume of the ion exchange resin in the saturated equilibrium state". The saturated equilibrium state refers to a state in which the ion exchange resin is brought into contact with air at 25°C and a relative humidity of 100% for 30 minutes or more to reach a saturated state. Passing hydrochloric acid means not only passing hydrochloric acid through the ion exchange resin but also including immersing the ion exchange resin in hydrochloric acid. The amount of total metal impurities per 1 mL of the ion exchange resin (μg / mL-R) can be calculated by the following formula from the amount of each eluted metal impurity (μg / L), the volume of the eluent used for elution (L), and the volume of the chelating resin (mL). Amount of total metal impurities (μg / mL-R) = (amount of each metal impurity (μg / L) × volume of eluent (L)) / volume of ion exchange resin (mL)

[0022] The ion exchange resin according to the present invention can be a single bed of a chelating resin or a cation exchange resin, or a mixed bed or a multiple bed of these two types. When the cation exchange resin is used as a single bed, the cation exchange resin is preferably weakly acidic. From the viewpoint of reducing metal impurities, the cation exchange resin and the chelating resin may be used in a mixed bed or a multiple bed. In that case, the amount of the chelating resin used is preferably 50% or more and 99% or less based on the total amount of the chelating resin and the cation exchange resin.

[0023] The chelating resin used in the present invention is a resin having a functional group (chelating group) capable of forming a chelate (complex) with a metal ion. Since the chelating resin does not have strongly acidic and strongly basic functional groups, high-purity purification of an ester-based organic solvent that is prone to hydrolysis is possible. Therefore, it is preferable to use the chelating resin as a single bed. Examples of the functional group of the chelating resin include an aminomethylphosphonic acid group, an iminodiacetic acid group, a thiol group, and a polyamine group having a weakly anionic exchange group. From the viewpoint of selectivity for a plurality of metal species, etc., as the chelating resin, those having an aminomethylphosphonic acid group or an iminodiacetic acid group as a functional group are preferable.

[0024] The chelating resin preferably has an H form as the initial ionic form. For example, Orlite (registered trademark) DS-21 (product name, manufactured by Organo Corporation, chelating group: aminomethylphosphonic acid group), Orlite (registered trademark) DS-22 (product name, manufactured by Organo Corporation, chelating group: iminodiacetic acid group), AmberSep (registered trademark) IRC747UPS (product name, manufactured by DuPont, chelating group: aminomethylphosphonic acid group), AmberSep (registered trademark) IRC748 (product name, manufactured by DuPont, chelating group: iminodiacetic acid group), AmberSep (registered trademark) IRC743 (product name, manufactured by DuPont, chelating group: N-methylglucamine), Diaion (registered trademark) CR11 (product name, manufactured by Mitsubishi Chemical Corporation, chelating group: iminodiacetic acid group), S930 (product name, manufactured by Purolite Corporation, chelating group: iminodiacetic acid group), S950 (product name, manufactured by Purolite Corporation, chelating group: aminophosphoric acid group), etc. can be mentioned, but it is not limited thereto. When the initial ionic form of the above resin is a salt form other than the H form (for example, sodium ion form), it can be converted to the H form by a known method and used. It can be converted from the salt form to the H form by washing with the above-mentioned mineral acid.

[0025] Examples of the cation exchange resin used in the present invention include a strongly acidic cation exchange resin having a sulfonic acid group (-SO3H) and a weakly acidic cation exchange resin having a carboxylic acid group (-COOH). Further, the cation exchange resin may be either a gel type having a small pore diameter and being transparent or a macroporous type (also called a macroporous type or a hyperporous type) having a large pore diameter among the resin pores.

[0026] Examples of the cation exchange resin used in the present invention include, but are not limited to, Orlite (registered trademark) DS-1 (trade name, manufactured by Organo Corporation), Orlite (registered trademark) DS-4 (trade name, manufactured by Organo Corporation), Amberlite (registered trademark) IRC76 (trade name, manufactured by DuPont), Amberlite (registered trademark) HPR8400H (trade name, manufactured by DuPont), Orlite (registered trademark) 15JS-HG·DRY (trade name, manufactured by Organo Corporation), Amberlite (registered trademark) IRN99H (trade name, manufactured by DuPont), Amberlite (registered trademark) CR99 K / 350 (trade name, manufactured by DuPont), etc.

[0027] In the present invention, the anion exchange resin can also be used as a single bed. In that case, the anion exchange resin is preferably weakly basic. Further, the chelating resin and the cation exchange resin can also be used in combination with an anion exchange resin. In this case, the anion exchange resin may be a mixed bed or a multiple bed with at least one of the chelating resin and the cation exchange resin. From the viewpoint of reducing metal impurities, the cation exchange resin, the chelating resin, and the anion exchange resin may be used in a mixed bed or a multiple bed. In that case, the usage amount of the anion exchange resin is preferably 25% or more and 100% or less with respect to the total amount of the cation exchange resin and any chelating resin.

[0028] Examples of the anion exchange resin include strongly basic anion exchange resins having a quaternary ammonium base and weakly basic anion exchange resins having a primary to tertiary amino group. Examples of the anion exchange resin include, but are not limited to, Orlite (registered trademark) DS-2, DS-6, Orlite (registered trademark) B20-HG·DRY (all are trade names of products manufactured by Organo Corporation), etc.

[0029] (Pretreatment step) For cation exchange resins, chelating resins, and anion exchange resins (hereinafter collectively referred to as "ion exchange resins"), before being used for the purification of organic solvents, if necessary, in order to suppress the elution of moisture from the ion exchange resins, the ion exchange resins may be dried, or pretreatment may be performed on the dried or undried products. That is, the purification method according to the present invention may have a pretreatment step of performing a drying step or pretreatment for suppressing the elution of moisture from the ion exchange resin before the filtration step and the ion exchange step.

[0030] As the drying method, heating drying by drying with hot air below the maximum operating temperature of the ion exchange resin, freeze drying, and vacuum drying combining heating and reduced pressure are common. In particular, vacuum drying has the advantage that it does not require extremely high temperatures, so it can be applied to anion exchange resins with low heat resistance and is the most common. Also, vacuum drying may be combined after replacing the resin-containing moisture with a non-aqueous solution or the like.

[0031] Examples of the pretreatment method include contacting the ion exchange resin with the organic solvent to be purified or contacting the ion exchange resin with a pretreatment organic solvent having a higher relative permittivity than the organic solvent to be purified. Specifically, a method of passing the organic solvent to be purified through a column filled with the ion exchange resin before purification and continuing the passage until the moisture concentration in the solvent at the inlet and outlet of the column becomes approximately the same can be mentioned. Also, a method of passing a pretreatment organic solvent having a higher relative permittivity than the organic solvent to be purified through a column filled with the ion exchange resin before purification and continuing the passage until the moisture concentration in the solvent at the inlet and outlet of the column becomes approximately the same can be mentioned. In this case, after passing the pretreatment organic solvent, the organic solvent to be purified may be further passed until the moisture concentration in the solvent at the inlet and outlet of the column becomes approximately the same. As the pretreatment organic solvent, alcohols such as methanol and ethanol having a relative permittivity of 20 or more at 25°C are preferably used.

[0032] (Ion Exchange Step) The method of bringing the organic solvent after passing through the particle filter into contact with the ion exchange resin is not particularly limited, and examples include a batch treatment method and a continuous flow-through treatment method using a column. From the viewpoints of operability and efficiency, the continuous flow-through treatment method is preferred.

[0033] In the batch treatment method, first, the organic solvent is filtered through a particle filter, and the filtered organic solvent is recovered. Next, the recovered organic solvent is charged into a reaction tank equipped with a stirrer filled with ion exchange resin. The volume ratio is not particularly limited, but an organic solvent of 2 to 200 with respect to a resin amount of 1 is preferred. Then, it is left for about 0.5 to 24 hours, for example. After leaving, the stirrer is operated to uniformly mix the ion exchange resin and the organic solvent. The stirring speed and stirring time may be appropriately determined according to the size of the reaction tank, the throughput, etc. After completion of stirring, filtration or the like is performed to separate the ion exchange resin and the organic solvent, whereby metal impurities are reduced and a purified organic solvent can be obtained.

[0034] In the continuous flow-through treatment method, the ion exchange resin is filled in a purification column such as a column. The height of the resin filling layer in the purification column is not particularly limited, and can be, for example, 100 to 1500 mm. Next, the organic solvent is passed through at, for example, an SV (space velocity, h -1 ) of 2 to 20 for 2 to 100 BV. Here, BV (Bed volume) represents the flow rate multiple of the solvent to be passed through with respect to the resin amount. From the viewpoint of metal reduction, the passage of the organic solvent is preferably carried out at an SV of 2 to 20, and more preferably at an SV of 5 to 10. The direction of the flow-through may be either downward flow or upward flow. By flowing through in this way, the metal impurities in the organic solvent are adsorbed by the ion exchange resin and reduced.

[0035] Regarding the ion exchange resin, when a pretreatment for suppressing the elution of moisture from the above-described ion exchange resin is carried out before purifying the organic solvent, the purification member such as a column used in the pretreatment can be used as it is to perform an ion exchange step of bringing the organic solvent into contact with the ion exchange resin.

[0036] (Purification apparatus for organic solvent) Hereinafter, an apparatus for purifying an organic solvent according to an embodiment of the present invention will be described, but the present invention is not limited thereto.

[0037] FIG. 1 shows a schematic diagram of an apparatus for purifying an organic solvent according to the present invention, which includes a storage tank 2 for storing an organic solvent 1 to be purified, a line for passing the organic solvent from the storage tank 2 to a particle removal filter 3 for filtering the organic solvent, and a purification means for purifying the filtered organic solvent by passing it through a column 4 filled with an ion exchange resin. Further, it can have a cleaning line for cleaning the particle removal filter and a cleaning line for cleaning the ion exchange resin. The purified organic solvent is measured by a metal content measuring means (not shown) to determine whether the metal concentration has reached a reference value and then recovered.

[0038] The apparatus for purifying an organic solvent may perform processing by a circulation system as shown in FIG. 2. The organic solvent purified by passing through the particle removal filter 3 and the column 4 filled with the ion exchange resin is returned from the circulation line CL to the storage tank 2 and repeatedly purified. The metal content in the storage tank 2 is measured, and when it is confirmed that the metal concentration has reached the reference value, it is recovered. By purifying in the circulation system, metal impurities can be removed with higher purity.

[0039] In order to prevent an inert gas or air dissolved in the organic solvent inside the filter and in the column from generating as bubbles, it is preferable to apply backpressure from the fine particle filter to the outlet of the column filled with the ion exchanger during liquid flow. At this time, the backpressure is preferably 0.01 MPa to 1 MPa, and more preferably 0.05 MPa to 0.1 MPa. Furthermore, it is preferable to adjust and operate so that the backpressure at the outlet of the column filled with the ion exchanger is higher than the backpressure at the outlet of the fine particle filter. When the backpressure at the outlet of the column filled with the ion exchanger is lower than the pressure at the outlet of the fine particle filter, gas dissolved in the organic solvent may generate as bubbles in the column. If bubbles are present in the column filled with the ion exchanger, the contact between the impurities and the ion exchange groups is inhibited, and the impurities may leak into the purified liquid without being ion-exchanged. In particular, the ion exchange resin, which is a granular ion exchanger, has more functional groups inside the resin than on the surface, so it is easily affected by the short path caused by the generation of bubbles. Also, in highly refined purification at the ppt level, such a short path is particularly undesirable because it destabilizes the performance. Also in purification in the circulation system, it is preferable to apply backpressure from the fine particle filter into the column filled with the ion exchanger so that no bubbles are generated in the column filled with the ion exchanger. It is also preferable that no bubbles are generated in the fine particle filter.

[0040] In the purification of an organic solvent containing a large amount of metal impurities, a distillation column capable of distilling the organic solvent can be provided before the organic solvent purification apparatus. In distillation, it is also possible to remove inorganic fine particles and the like. Thereby, after separating metal impurities to some extent by distillation, the organic solvent purification apparatus can further reduce trace metals and purify the organic solvent to a high purity.

[0041] Also, before the organic solvent purification apparatus, a particle removal filter and an ion exchanger can be provided in this order as rough purification. Thereby, after separating the amount of metal impurities in the organic solvent to some extent, the organic solvent purification apparatus can further reduce trace metals and purify the organic solvent to a high purity. Further, a particle removal filter may be further combined after the ion exchanger of the organic solvent purification apparatus. FIG. 3 shows a configuration in which a second particle removal filter 5 is disposed after the purification means.

[0042] In the production of high-purity organic solvents, after purifying the organic solvent for the purpose of reducing metal impurities, the amount of metal impurities is measured. In the present invention, the metal content is monitored online, and when the metal content is higher than the reference value, it is automatically returned to the organic solvent purification apparatus, and the organic solvent is purified again.

[0043] With the organic solvent purification apparatus according to the present invention, metal impurities in the organic solvent used immediately before the use point in the semiconductor manufacturing process can be reduced and highly purified. A filter using an ion exchange membrane may be combined after the purification means using an ion resin of the organic solvent purification apparatus. When an ion exchange membrane is provided after the purification means, since the load due to metal impurities in the subsequent stage is reduced by resin purification, an effect of extending the life of the ion exchange membrane in the subsequent stage can be expected.

Example

[0044] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

[0045] Details of each ion exchange resin, organic solvent, and particle removal filter used in the following examples are as follows. (Ion exchange resin) · Chelating resin (trade name: Orlite (registered trademark) DS-21, manufactured by Organo Corporation) · Cation exchange resin (trade name: Orlite (registered trademark) DS-4, manufactured by Organo Corporation) · Anion exchange resin (trade name: Orlite (registered trademark) DS-6, manufactured by Organo Corporation) (Organic solvent) · PGMEA (propylene glycol monomethyl ether acetate, manufactured by Kanto Chemical Co., Inc.) · nBA (Normal Butyl Acetate, manufactured by Taiwan Maxwave) (Particle Removal Filter) Particle Removal Filter: Disposable filter made of UPE (pore size: 5 nm, membrane area: 2300 cm 2 )

[0046] (Example 1) A column made of PFA (inner diameter: 16 mm, height: 300 mm) was connected in series after the particle removal filter.

[0047] Pretreatment Process The PFA column was filled with a total of 72 mL of chelating resin, cation exchange resin, and anion exchange resin. The volume ratio of chelating resin, cation exchange resin, and anion exchange resin is 75:25:100. When hydrochloric acid with a concentration of 3% by mass was passed through the purified ion exchange resin at a volume ratio of 25 times, the total amount of eluted metal impurities was 5 μg / mL-R or less. Next, alcohol with a moisture concentration of 50 ppm or less was passed through until the moisture at the column outlet reached 200 ppm or less. Then, PGMEA with a moisture concentration of 50 ppm or less was passed through until the moisture concentrations in the PGMEA at the column inlet and outlet became equal, removing the moisture in the ion exchange resin.

[0048] Filtration Process and Ion Exchange Process PGMEA was passed through the particle removal filter and the PFA column filled with the pretreated ion exchange resin for purification. During the passage, the back pressure was adjusted to be 0.01 MPa or more from the particle removal filter to the outlet of the PFA column filled with the ion exchange resin for purification. The treatment liquid before and after purification was sampled to measure the Cr concentration. The Cr concentration was measured using an inductively coupled plasma mass spectrometer (ICP-MS). The flow rate of passing PGMEA was set to 5 times the volume per hour with respect to the total volume of chelating resin, cation exchange resin, and anion exchange resin.

[0049] (Example 2) PGMEA was purified in the same manner as in Example 1, except that a chelating resin and a cation exchange resin were used for the ion exchange resin, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0050] (Comparative Example 1) PGMEA was purified in the same manner as in Example 1, except that only a particle removal filter was used without using an ion exchange resin, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0051] (Example 3) PGMEA was purified in the same manner as in Example 1, except that only a chelating resin was used for the ion exchange resin, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0052] (Comparative Example 2) PGMEA was purified in the same manner as in Example 3, except that a PFA column and a particle removal filter were connected in series in this order, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0053] (Comparative Example 3) PGMEA was purified in the same manner as in Example 3, except that only an ion exchange resin was used without using a particle removal filter, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0054] (Comparative Example 4) PGMEA was purified in the same manner as in Comparative Example 3, except that a chelating resin and an anion exchange resin were used for the ion exchange resin, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0055] (Example 4) PGMEA was purified in the same manner as in Example 1, except that a particle removal filter with a pore size of 100 nm was used, and the treatment liquids before and after purification were sampled to measure the Cr concentration.

[0056] (Comparative Example 5) PGMEA was purified in the same manner as in Comparative Example 1, except that a particle removal filter with a pore size of 1000 nm was used. The treatment liquid before and after purification was sampled to measure the Cr concentration.

[0057] (Comparative Example 6) PGMEA was purified in the same manner as in Comparative Example 5, except that a particle removal filter with a pore size of 3000 nm was used. The treatment liquid before and after purification was sampled to measure the Cr concentration.

[0058] (Example 5) PGMEA was purified in the same manner as in Example 4, except that a particle removal filter with a pore size of 1000 nm was used. The treatment liquid before and after purification was sampled to measure the Cr concentration.

[0059] (Example 6) Purification was carried out in the same manner as in Example 2, except that nBA was used as the organic solvent. The treatment liquid before and after purification was sampled to measure the Cr concentration. However, chelating resin and anion exchange resin were used as the ion exchange resins.

[0060] (Example 7) nBA was purified in the same manner as in Example 6, except that a particle removal filter with a pore size of 1000 nm was used. The treatment liquid before and after purification was sampled to measure the Cr concentration.

[0061] (Example 8) Purification was carried out in the same manner as in Example 3, except that the PFA column and the storage tank were connected in series after the particle removal filter. The treatment liquid before and after purification was sampled to measure the Cr concentration. A PFA storage tank with a volume of 1 L was used. The PGMEA in the tank was returned to the particle removal filter by pumping, and a circulating continuous flow treatment was performed. The flow rate of PGMEA was set to 5 times the volume of the chelating resin per hour, and the flow was carried out for 18 hours. Then, the treatment liquid was recovered after 18 hours of flow.

[0062]

Table 1

[0063] In Example 1, when a chelating resin, a cation exchange resin, and an anion exchange resin were used in the ion exchange resin, in Example 2, when a chelating resin and a cation exchange resin were used, and in Example 3, when only a chelating resin was used, it was revealed that Cr in the organic solvent could be reduced. Also, in Examples 4 and 5, when the pore diameter of the particle removal filter was 100 nm or 1000 nm, it was revealed that Cr in the organic solvent could be reduced. Furthermore, in Examples 6 and 7, it was revealed that Cr could be reduced even when nBA was used instead of PGMEA in the organic solvent. In Example 8, it was revealed that Cr could be reduced even when PGMEA was purified by circulating continuous liquid passing treatment.

[0064] In Comparative Example 1, even when the organic solvent was purified using only a particle removal filter without using an ion exchange resin, Cr could not be reduced. In Comparative Example 2, even when the organic solvent was purified in the order of an ion exchange resin and a particle removal filter, Cr could not be reduced. In Comparative Example 3, even when only a chelating resin was used as the ion exchange resin without using a particle removal filter, Cr could not be reduced. Also, in Comparative Example 4, similar to Comparative Example 3, only an ion exchange resin was used without using a particle removal filter, and even when a chelating resin and an anion exchange resin were used as the ion exchange resin, Cr could not be reduced. In Comparative Example 5, when the pore diameter of the particle removal filter was 1000 nm, it was revealed that a part of Cr in the organic solvent could be reduced. In Comparative Example 6, when the pore diameter of the particle removal filter was 3000 nm, Cr in the organic solvent could not be reduced at all.

[0065] Reference Example For a thinner of PGMEA 30%:PGME 70% (volume ratio) and IPA, purification was performed using only an ion exchange resin. As the resin used, a mixed bed of a chelating resin (DS-21), a cation exchange resin (DS-1), and an anion exchange resin (DS-3) was used. The results are shown in Table 2 below.

[0066]

Table 2

[0067] In the case of thinner, Cr can be reduced to less than 2 ppt only with chelating resin. Also, in the case of IPA, Cr can be reduced to below the detection limit with a mixed bed of cation exchange resin and anion exchange resin.

[0068] Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. This application claims priority based on Japanese Patent Application No. 2022-072311 filed on April 26, 2022, and incorporates all of its disclosures herein.

[0069] The present invention includes the following methods. [Method 1] A purification method for reducing metal impurities in an organic solvent, comprising a filtration step of filtering the organic solvent with a particle removal filter, and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger. A purification method for an organic solvent, characterized by including these steps. [Method 2] The purification method for an organic solvent according to [Method 1], wherein the solution after passing through the ion exchanger is passed through the particle removal filter to circulate and purify the solution. [Method 3] The purification method for an organic solvent according to [Method 1] or [Method 2], including a post-filtration step of filtering the organic solvent obtained in the ion exchange step with a second particle removal filter. [Method 4] The purification method for an organic solvent according to any one of [Method 1] to [Method 3], wherein the pore diameter of the particle removal filter is 5 nm or more and 1000 nm or less. [Method 5] The purification method for an organic solvent according to any one of [Method 1] to [Method 4], wherein the metal impurity is Cr. [Method 6] The purification method of an organic solvent according to any one of [Method 1] to [Method 5], wherein the ion exchanger is an ion exchange resin. [Method 7] The purification method of an organic solvent according to [Method 6], wherein the ion exchange resin is used as a single bed of any one of a chelating resin, a cation exchange resin, and an anion exchange resin, or a mixed bed or a multiple bed of two or more kinds thereof. [Method 8] The purification method of an organic solvent according to [Method 6] or [Method 7], wherein the ion exchange resin is a purified ion exchange resin having a total metal impurity elution amount of 5 μg / mL-R or less when passed through with 25 times the volume of 3 mass% hydrochloric acid. [Method 9] The purification method of an organic solvent according to any one of [Method 1] to [Method 8], wherein the organic solvent is propylene glycol monomethyl ether acetate or normal butyl acetate.

[0070] The present invention includes the following configurations. [Configuration 1] A purification apparatus for reducing metal impurities in an organic solvent, comprising a particle removal filter for filtering the organic solvent, and a purification means for purifying the organic solvent obtained after the filtration by passing it through an ion exchanger.

Explanation of Signs

[0071] 1 Organic solvent to be purified 2 Storage tank 3 Particle removal filter 4 Ion exchange resin column 5 Second particle removal filter

Claims

1. A purification method for reducing metal impurities in an organic solvent, comprising a filtration step of filtering the organic solvent with a particle removal filter, and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger. The filtration step is a step of filtering the organic solvent to be filtered with the particle removal filter before passing it through the ion exchanger to remove metal impurities in the organic solvent. The organic solvent to be filtered contains Cr as the metal impurity, and the SP value of the organic solvent is 20 or less. The pore diameter of the particle removal filter is 5 nm or more and 1000 nm or less. The ion exchanger is an ion exchange resin, and the ion exchange resin is used as a mixed bed of a chelating resin and an anion exchange resin, or a mixed bed of a chelating resin, a cation exchange resin, and an anion exchange resin. A method for purifying an organic solvent, characterized in that.

2. The method for purifying an organic solvent according to claim 1, wherein the organic solvent after passing through the ion exchanger is passed through the particle removal filter to circulate and purify the organic solvent.

3. The method for purifying an organic solvent according to claim 1, further comprising a post-filtration step of filtering the organic solvent obtained in the ion exchange step with a second particle removal filter.

4. The ion exchange resin is a purified ion exchange resin having a total metal impurity elution amount of 5 μg / mL-R or less when passed through hydrochloric acid having a concentration of 3% by mass in a volume ratio of 25 times. The method for purifying an organic solvent according to any one of claims 1 to 3.

5. The method for purifying an organic solvent according to any one of claims 1 to 3, wherein the organic solvent is propylene glycol monomethyl ether acetate or normal butyl acetate.

6. A purification apparatus used in the method for purifying an organic solvent according to any one of claims 1 to 3, which reduces metal impurities in the organic solvent, comprising a particle removal filter for filtering the organic solvent, and a purification means for purifying the organic solvent obtained after the filtration by passing it through an ion exchanger.

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