JP7696502B2 - Method and apparatus for purifying organic solvents - Google Patents

Description

The present invention relates to a method and apparatus for purifying organic solvents.

Semiconductor devices are manufactured through hundreds of complex processes. The line width of a semiconductor device is determined by the photoresist process. The photoresist process includes a process of applying resist to a silicon wafer, an exposure process of irradiating short-wavelength light from a light source through a mask, and a process of developing the resist mask. It also includes a process of etching the exposed part through the resist mask, and a process of stripping 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, and the organic solvent used contains PGMEA (propylene glycol monomethyl ether acetate) or PGME (propylene glycol monomethyl ether) as the main component. In addition, various organic solvents are used for the developer, rinse solution, stripper, chemical mechanical polishing (CMP) slurry, and cleaning solution after CMP.

In recent years, there has been a demand for further miniaturization of semiconductor device line widths in order to promote technology for miniaturization and high performance of IT equipment. However, as line widths become finer, even small amounts of impurities can adversely affect semiconductor devices. In particular, if a large amount of metal elements remain among the impurities contained in the organic solvent, the metal elements will adhere to the wafer, leading to a decrease in the performance of the semiconductor device. For this reason, it is essential to reduce the amount of metal elements in the organic solvent.

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 with the fluid inlet.

Patent Document 2 discloses a depth filter that includes a porous molded body that is a sintered or swollen body of a mixed powder containing a dry gel powder and a thermoplastic resin powder in order to efficiently remove metal ions from the water being treated.

Patent Document 3 discloses a method for producing a chemical solution, which includes, in no particular order, a filtration step for filtering a product to be purified, an ion removal step for subjecting the product to ion exchange or ion adsorption using a chelating group, and a distillation step for distilling the product to be purified. This is to provide a chemical that has 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 the purification equipment is set up in the following order: a distillation step, an ion removal step using an ion exchange resin, a distillation step, and a filtration step using a filter.

JP 2015-521101 A JP 2019-209224 A International Publication No. 2020/013218

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

Therefore, the present invention aims to provide a purification method and purification apparatus for reducing metal impurities in an organic solvent.

As a result of intensive research, the inventors have found that by installing a particle-removing filter beforehand in the stage preceding the ion-exchange resin, solid metal impurities in the organic solvent are removed in advance by the particle-removing filter. Then, by treating the organic solvent with the ion-exchange resin, it is possible to reduce metal elements, particularly Cr.

The present invention is a purification method for reducing metal impurities in an organic solvent, characterized in that it includes a filtration step of filtering the organic solvent through a particle removal filter, and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger.

The present invention also relates to a purification apparatus for reducing metal impurities in an organic solvent, characterized in that the apparatus includes a particle removal filter for filtering the organic solvent, and an ion exchange means for passing the organic solvent obtained after the filtration through an ion exchanger to purify the organic solvent.

According to the present invention, a purification method and purification apparatus can be provided for reducing metal impurities in an organic solvent.

1 is a conceptual diagram showing one embodiment of a purification device according to the present invention. FIG. 1 is a conceptual diagram showing an embodiment of a purification apparatus according to the present invention in a circulating system. FIG. 4 is a conceptual diagram showing another embodiment of the purification device according to the present invention.

The purification method for reducing metal impurities in an organic solvent according to the present invention includes a filtration process for filtering the organic solvent of the treated liquid using a particle removal filter, and an ion exchange process for passing the organic solvent obtained in the filtration process through an ion exchanger.

(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 preferable. According to the study by the present inventors, even in the case of an EL grade organic solvent, metal impurities in IPA (isopropyl alcohol) and thinner (PGMEA/PGME) can be removed by ion exchange resin. However, in the case of PGMEA alone and nBA (normal butyl acetate), it was found that removal of metal impurities, especially Cr, is insufficient by ion exchange resin alone. As disclosed in the background art, even if a particle removal filter is provided after the ion exchange process, Cr ions remain in the organic solvent. From this, it is presumed that in these solvents, Cr changes into a form that is difficult to remove by a filter due to contact between the ion exchange resin and particulate Cr. This phenomenon is not limited to PGMEA or nBA, and can also occur in organic solvents with a solubility parameter (SP value) 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 . The effect of the present invention is more pronounced in a solvent having an SP value of 20 or less. The SP value is a value quoted from "Hansen Solubility Parameters: A User's Handbook, Second Edition, Published in 2007".

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, each of which has a concentration of 100 ppt or less. In addition, special grade PGMEA manufactured by Kanto Chemical Co., Ltd. contains Na, Ca, Cr, Fe, Ni, Cu, and Zn, with the respective concentrations of Na being 10 ppb or less, and Ca, Cr, Fe, Ni, Cu, and Zn being 200 ppt or less. The lower limit is equal to or greater than the purification target concentration, specifically equal to or greater than the detection limit of concentration measurement. Furthermore, 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, and Pb. The refining method and production apparatus of the present invention can particularly reduce Cr.

(Particle Removal Filter)
The particle filter is not particularly limited as long as it can remove metal impurity particles, but the pore size on the surface is preferably 1000 nm or less, more preferably 100 nm or less. The lower limit of the pore size is preferably at a level at which the pressure load on the device is not an issue, preferably 2 nm or more, more preferably 5 nm or more. Here, the pore size refers to the average value of the pore size of the porous membrane, and is measured by a bubble point method using IPA or HFE-7200 (manufactured by 3M). The material of the particle filter is not particularly limited as long as it is resistant to the organic solvent to be purified. Specific examples include PE (polyethylene), UPE (ultra-high molecular weight polyethylene), PTFE (polytetrafluoroethylene), PI (polyimide), PAI (polyamideimide), etc.
In addition, in order to avoid leaching of metal elements from the particle removal filter, it is preferable to wash the particle removal filter with a solvent that does not contain metal elements before use, and then confirm by measurement that no metal has been leached from the particle removal filter before use.

(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. 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. The ion exchanger of the present invention also includes a monolithic ion exchanger having a continuous skeleton and continuous pores.

Before use, the chelating resin and the cation exchange resin are preferably purified into a purified ion exchange resin by contacting them with a mineral acid solution having a metal impurity content of 1 mg/L or less and a concentration of 5% by mass or more. Examples of mineral acids include hydrochloric acid, sulfuric acid, and nitric acid.

Furthermore, when 3% by mass hydrochloric acid is passed through the purified ion exchange resin at a volume ratio of 25 times, the total amount of metal impurities eluted is preferably 5 μg/mL-R or less. Here, "volume ratio of 25 times" means that a volume of hydrochloric acid 25 times the volume of the ion exchange resin is passed through. The unit "/mL-R" means "per mL of the volume of the ion exchange resin in a saturated equilibrium state". The saturated equilibrium state refers to a state in which the ion exchange resin is saturated by contacting it with the atmosphere at 25° C. and a relative humidity of 100% for 30 minutes or more. Passing hydrochloric acid includes not only passing hydrochloric acid through the ion exchange resin, but also immersing the ion exchange resin in hydrochloric acid. The total amount of metal impurities (μg/mL-R) per mL of the volume of the ion exchange resin can be calculated 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) according to the following formula.
Total amount of metal impurities (μg/mL-R)=(amount of each metal impurity (μg/L)×volume of eluent (L))/volume of ion exchange resin (mL)

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 multiple beds of these two types. When a cation exchange resin is used as a single bed, it is preferable that the cation exchange resin is weakly acidic. From the viewpoint of reducing metal impurities, a mixed bed or multiple beds of a cation exchange resin and a chelating resin may be used. In that case, the amount of the chelating resin used is preferably 50% or more and 99% or less of the total amount of the chelating resin and the cation exchange resin.

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 a strongly acidic or strongly basic functional group, it is possible to highly purify ester-based organic solvents that are prone to hydrolysis. Therefore, it is preferable to use the chelating resin in a single bed. Examples of functional groups of the chelating resin include aminomethyl phosphate groups, iminodiacetic acid groups, thiol groups, and polyamine groups having weak anionic exchange groups. From the viewpoint of selectivity for multiple metal species, it is preferable that the chelating resin has an aminomethyl phosphate group or an iminodiacetic acid group as a functional group.

It is preferable that the initial ionic form of the chelating resin is H-type. For example, Orlite (registered trademark) DS-21 (trade name, manufactured by Organo Corporation, chelating group: aminomethyl phosphate group), Orlite (registered trademark) DS-22 (trade name, manufactured by Organo Corporation, chelating group: iminodiacetic acid group), AmberSep (registered trademark) IRC747UPS (trade name, manufactured by DuPont, chelating group: aminomethyl phosphate group), AmberSep (registered trademark) Examples of the chelating agent include, but are not limited to, IRC748 (trade name, manufactured by DuPont, chelating group: iminodiacetic acid group), AmberSep (registered trademark) IRC743 (trade name, manufactured by DuPont, chelating group: N-methylglucamine), Diaion (registered trademark) CR11 (trade name, manufactured by Mitsubishi Chemical Corporation, chelating group: iminodiacetic acid group), S930 (trade name, manufactured by Purolite Co., Ltd., chelating group: iminodiacetic acid group), and S950 (trade name, manufactured by Purolite Co., Ltd., chelating group: aminophosphate group). In addition, when the initial ion form of the above-mentioned resin is a salt form other than the H form (for example, a 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 mineral acid.

The cation exchange resin used in the present invention includes a strongly acidic cation exchange resin having a sulfonic acid group (-SO ₃ H) and a weakly acidic cation exchange resin having a carboxylic acid group (-COOH). The cation exchange resin may be either a transparent gel type resin having small pores, a macrolitercular type (MR type) resin having large pores, or a macroporous type (also called a porous type or high-porous type).

Examples of cation exchange resins 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), and Amberlite (registered trademark) CR99 K/350 (trade name, manufactured by DuPont).

In the present invention, the anion exchange resin can be used as a single bed. In that case, it is preferable that the anion exchange resin is weakly basic. In addition, the chelating resin and the cation exchange resin can 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 amount of the anion exchange resin used is preferably 25% or more and 100% or less of the total amount of the cation exchange resin and any chelating resin.

Examples of anion exchange resins include strongly basic anion exchange resins having quaternary ammonium bases and weakly basic anion exchange resins having primary to tertiary amino groups. Examples of anion exchange resins include, but are not limited to, Orlite (registered trademark) DS-2, DS-6, Orlite (registered trademark) B20-HG DRY (all trade names manufactured by Organo Corporation).

(Pretreatment process)
Before using a cation exchange resin, a chelating resin, or an anion exchange resin (hereinafter, these are also collectively referred to as "ion exchange resins") in the purification of an organic solvent, the ion exchange resin may be dried or pretreated to a dried or undried product in order to suppress water elution from the ion exchange resin, as necessary. That is, the purification method according to the present invention may have a pretreatment step in which a drying step or pretreatment step is performed to suppress water elution from the ion exchange resin, before the filtration step and the ion exchange step.

Common drying methods are heat drying, which uses hot air at a temperature below the maximum operating temperature of the ion exchange resin, freeze drying, and vacuum drying, which combines heating and reduced pressure. In particular, reduced pressure drying does not require extremely high temperatures, so it has the advantage of being applicable to anion exchange resins, which have low heat resistance, and is the most common method. Vacuum drying may also be combined with replacing the moisture contained in the resin with a non-aqueous solution, etc.

Examples of pretreatment methods include contacting the organic solvent to be purified with an ion exchange resin, or contacting the ion exchange resin with a pretreatment organic solvent having a higher dielectric constant than the organic solvent to be purified. Specifically, a method is used in which the organic solvent to be purified is passed through a column packed with ion exchange resin before use in purification, and the passing of the solvent is continued until the water concentration in the solvent at the inlet and outlet of the column is approximately the same. Another method is to pass a pretreatment organic solvent having a higher dielectric constant than the organic solvent to be purified through a column packed with ion exchange resin before use in purification, and the passing of the solvent is continued until the water concentration in the solvent at the inlet and outlet of the column is approximately the same. In this case, after passing the pretreatment organic solvent, the organic solvent to be purified may be passed through the column until the water concentration in the solvent at the inlet and outlet of the column is approximately the same. As the pretreatment organic solvent, an alcohol such as methanol or ethanol having a dielectric constant of 20 or more at 25°C is preferably used.

(Ion exchange process)
The method for contacting the organic solvent after passing through the particle removal filter with the ion exchange resin is not particularly limited, and examples thereof include a batch treatment method and a continuous liquid passing treatment method using a column. From the viewpoints of operability and efficiency, the continuous liquid passing treatment method is preferred.

In the batch processing method, first, the organic solvent is filtered through a particle filter, and the organic solvent after filtration is recovered. Next, the recovered organic solvent is filled into a reaction tank equipped with an agitator and loaded with an ion exchange resin. The volume ratio is not particularly limited, but a ratio of 2 to 200 organic solvent per 1 resin is suitable. Then, the mixture is left for, for example, 0.5 to 24 hours. After leaving the mixture, the agitator is operated to mix the ion exchange resin and organic solvent uniformly. The stirring speed and stirring time may be appropriately determined depending on the size of the reaction tank, the processing amount, etc. After stirring is completed, filtration or the like is performed to separate the ion exchange resin and the organic solvent, thereby reducing metal impurities and obtaining a purified organic solvent.

In the continuous liquid passing treatment method, the ion exchange resin is packed in a purification tower such as a column. The height of the resin-packed bed of the purification tower is not particularly limited, and can be, for example, 100 to 1500 mm. Next, the organic solvent is passed through at, for example, 2 to 100 BV at SV (space velocity, h ⁻¹ ) 2 to 20. Here, BV (Bed volume) represents the flow rate multiple of the solvent to be passed through relative to the amount of resin. From the viewpoint of reducing metals, the passing of the organic solvent is preferably performed at SV 2 to 20, more preferably SV 5 to 10. The direction of the passing may be either downward flow or upward flow. By passing the liquid in this manner, metal impurities in the organic solvent are adsorbed by the ion exchange resin and reduced.

In addition, if the ion exchange resin is subjected to a pretreatment to suppress the elution of water from the ion exchange resin before purifying the organic solvent, the purification component such as a column used in the pretreatment can be used as is to carry out the ion exchange process in which the organic solvent is brought into contact with the ion exchange resin.

(Organic solvent purification device)
Hereinafter, an organic solvent purification apparatus according to an embodiment of the present invention will be described, but the present invention is not limited thereto.

Figure 1 shows a schematic diagram of an organic solvent purification apparatus according to the present invention, and includes a storage tank 2 for storing 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 ion exchange resin. It may further have a washing line for washing the particle removal filter and a washing line for washing the ion exchange resin. The purified organic solvent is recovered by a metal content measuring means (not shown) which measures whether the metal concentration has reached a standard value.

The organic solvent purification device may perform treatment using a circulation system as shown in Figure 2. The organic solvent purified by passing it through a particle removal filter 3 and a column 4 filled with ion exchange resin is returned to the storage tank 2 via the circulation line CL for repeated purification. The metal content in the storage tank 2 is measured, and the metal is recovered when it is confirmed that the metal concentration has reached the standard value. By purifying using a circulation system, metal impurities can be removed to a higher degree of purity.

In order to prevent the inert gas or air dissolved in the organic solvent in the filter and column from being generated as bubbles, it is preferable to apply back pressure from the particle filter to the outlet of the column packed with ion exchanger during liquid flow. At this time, the back pressure is preferably 0.01 MPa to 1 MPa, and more preferably 0.05 MPa to 0.1 MPa. Furthermore, it is preferable to operate the column by adjusting the back pressure at the outlet of the column packed with ion exchanger so that it is higher than the back pressure at the outlet of the particle filter. If the back pressure at the outlet of the column packed with ion exchanger is lower than the pressure at the outlet of the particle filter, the gas dissolved in the organic solvent in the column may be generated as bubbles. If bubbles are present in the column packed with ion exchanger, contact between the impurities and the ion exchange group is hindered, and the impurities may leak into the purified liquid without being ion-exchanged. In particular, 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 short paths caused by the generation of bubbles. In addition, in advanced purification at the ppt level, such short paths are particularly undesirable because they destabilize performance. In the purification in the circulation system, it is also preferable to apply back pressure from the particle filter to the column packed with the ion exchanger so that air bubbles are not generated in the column packed with the ion exchanger. It is also preferable that air bubbles are not generated in the particle filter.

When purifying organic solvents that contain a large amount of metal impurities, a distillation column capable of distilling the organic solvent can be installed before the organic solvent purification device. Distillation can also remove inorganic fine particles. In this way, after separating a certain amount of metal impurities by distillation, the organic solvent purification device can further reduce trace metals and highly purify the organic solvent.

In addition, a particle filter and an ion exchanger can be provided in this order for rough purification before the organic solvent purification device, whereby after the amount of metal impurities in the organic solvent is separated to a certain extent, the organic solvent purification device can further reduce the amount of trace metals and increase the purity of the organic solvent.
In addition, a particle filter may be further combined in the downstream of the ion exchanger in the organic solvent purification device. In Fig. 3, a configuration in which a second particle filter 5 is disposed in the downstream of the purification means is shown.

In the production of high-purity organic solvents, the amount of metal impurities is measured after purifying the organic solvent to reduce the amount of metal impurities. In the present invention, the metal content is monitored online, and if the metal content is higher than the reference value, the organic solvent is automatically returned to the purification device and the organic solvent is purified again.

The organic solvent purification device according to the present invention can reduce metal impurities in the organic solvent used immediately before the point of use in the semiconductor manufacturing process, and purify it to a high degree of purity. A filter using an ion exchange membrane may be combined downstream of the purification means using an ion resin in the organic solvent purification device. When an ion exchange membrane is provided downstream of the purification means, the load of metal impurities on the downstream stage is reduced by resin purification, and the effect of extending the life of the ion exchange membrane in the downstream stage can be expected.

The present invention will be explained in detail below with reference to examples, but the present invention is not limited to these.

Details of the ion exchange resins, organic solvents and particle filters used in the following examples are as follows.
(Ion exchange resin)
Chelate resin (product name: Orlite (registered trademark) DS-21, manufactured by Organo Corporation)
Cation exchange resin (product name: Orlite (registered trademark) DS-4, manufactured by Organo Corporation)
Anion exchange resin (product name: Orlite (registered trademark) DS-6, manufactured by Organo Corporation)
(Organic solvent)
PGMEA (propylene glycol monomethyl ether acetate, manufactured by Kanto Chemical Co., Ltd.)
・nBA (normal butyl acetate, manufactured by Taiwan Maxwave Co., Ltd.)
(Particle Removal Filter)
Particle removal filter: UPE disposable filter (pore size: 5 nm, membrane area: 2300 cm ² )

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

Pretreatment step 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 the chelating resin, cation exchange resin, and anion exchange resin was 75:25:100. When 25 volumes of hydrochloric acid with a concentration of 3% by mass were passed through the purified ion exchange resin, the total amount of metal impurities eluted was 5 μg/mL-R or less. Next, alcohol with a water concentration of 50 ppm or less was passed through until the water at the column outlet was 200 ppm or less. Then, PGMEA with a water concentration of 50 ppm or less was passed through until the water concentrations in the PGMEA at the column inlet and column outlet became the same, and the water in the ion exchange resin was removed.

Filtration step and ion exchange step PGMEA was passed through a PFA column packed with a particle removal filter and a pretreated ion exchange resin, and purification was performed. 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 packed with the ion exchange resin, and purification was performed. 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 speed at which PGMEA was passed was set to a speed of 5 times the total volume of the chelating resin, cation exchange resin, and anion exchange resin per hour.

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 as the ion exchange resin, and the treated liquid before and after purification was sampled to measure the Cr concentration.

(Comparative Example 1)
PGMEA was purified in the same manner as in Example 1, except that no ion exchange resin was used and only a particle removal filter was used. The treated liquid before and after purification was sampled to measure the Cr concentration.

Example 3
PGMEA was purified in the same manner as in Example 1, except that only a chelating resin was used as the ion exchange resin, and the treated liquid before and after purification was sampled to measure the Cr concentration.

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

(Comparative Example 3)
PGMEA was purified in the same manner as in Example 3, except that no particle removal filter was used and only an ion exchange resin was used. The treated liquid before and after purification was sampled to measure the Cr concentration.

(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 as the ion exchange resin, and the treated liquid before and after purification was sampled to measure the Cr concentration.

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 treated liquid before and after purification was sampled to measure the Cr concentration.

(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, and the treated liquid before and after purification was sampled to measure the Cr concentration.

(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, and the treatment liquid before and after purification was sampled to measure the Cr concentration.

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, and the treated liquid before and after purification was sampled to measure the Cr concentration.

Example 6
Except for using nBA as the organic solvent, purification was performed in the same manner as in Example 2, and the treated liquid was sampled before and after purification to measure the Cr concentration. However, a chelating resin and an anion exchange resin were used as the ion exchange resin.

(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, and the treatment liquid before and after purification was sampled to measure the Cr concentration.

(Example 8)
Purification was performed 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, and the treated liquid before and after purification were sampled to measure the Cr concentration. A PFA tank with a capacity of 1 L was used as the storage tank. The PGMEA in the tank was returned to the particle removal filter by pumping, and a continuous circulation liquid passing process was performed. The rate at which PGMEA was passed was set to a rate of 5 times the volume of the chelating resin per hour, and the liquid was passed for 18 hours. After the 18 hours of liquid passing, the treated liquid was collected.

In Example 1, it was revealed that Cr in an organic solvent can be reduced when a chelating resin, a cation exchange resin, and an anion exchange resin are used as the ion exchange resin, in Example 2, when a chelating resin and a cation exchange resin are used, and in Example 3, when only a chelating resin is used. In addition, in Examples 4 and 5, it was revealed that Cr in an organic solvent can be reduced when the pore size of the particle removal filter is 100 nm or 1000 nm. Furthermore, in Examples 6 and 7, it was revealed that Cr can be reduced even when nBA is used as the organic solvent instead of PGMEA. In Example 8, it was revealed that Cr can be reduced even when PGMEA is purified by continuous circulation and liquid passing treatment.

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

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

In the case of thinner, Cr can be reduced to less than 2 ppt using chelating resin alone. In the case of IPA, Cr can be reduced to below the detection limit using a mixed bed of cation exchange resin and anion exchange resin.

Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various modifications 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, the disclosure of which is incorporated herein in its entirety.

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.
[Method 2]
The method for purifying 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 the solution and purify it.
[Method 3]
The method for purifying an organic solvent according to [Method 1] or [Method 2], further comprising a post-filtration step of filtering the organic solvent obtained in the ion exchange step through a second particle removal filter.
[Method 4]
The method for purifying an organic solvent according to any one of [Method 1] to [Method 3], wherein the pore size of the particle removal filter is 5 nm or more and 1000 nm or less.
[Method 5]
The method for purifying an organic solvent according to any one of [Method 1] to [Method 4], wherein the metal impurity is Cr.
[Method 6]
The method for purifying 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 method for purifying 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 as a mixed bed or multiple beds of two or more kinds of the ion exchange resin.
[Method 8]
The method for purifying an organic solvent according to [Method 6] or [Method 7], wherein the ion exchange resin is a purified ion exchange resin in which a total amount of eluted metal impurities when 25 times the volume of 3% by mass of hydrochloric acid is passed through the resin is 5 μg/mL-R or less.
[Method 9]
The method for purifying 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.

The present invention includes the following configurations.
[Configuration 1]
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 passing the organic solvent obtained after the filtration through an ion exchanger to purify the organic solvent.

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

Claims (6)

A purification method for reducing metal impurities in an organic solvent, comprising: a filtration step of filtering the organic solvent through a particle removal filter; and an ion exchange step of passing the organic solvent obtained in the filtration step through an ion exchanger,
the filtering step is a step of filtering the organic solvent to be filtered through the particle removal filter before passing the organic solvent 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 size of the particle filter is 5 nm or more and 1000 nm or less,
1. A method for purifying an organic solvent, comprising the steps of: (a ) preparing a mixture of a chelating resin and an anion exchange resin; and (b) preparing a mixture of a chelating resin, a cation exchange resin and an anion exchange resin . The method for purifying an organic solvent according to claim 1, in which the organic solvent is circulated and purified by passing the organic solvent through the ion exchanger and then through the particle removal filter. 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 through a second particle removal filter. The method for purifying an organic solvent according to any one of claims 1 to 3, wherein the ion exchange resin is a purified ion exchange resin in which the total amount of metal impurities eluted when 25 volumes of hydrochloric acid having a concentration of 3% by mass are passed through is 5 μg/mL-R or less. 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. A purification apparatus for reducing metal impurities in an organic solvent, which is used in the method for purifying an organic solvent according to any one of claims 1 to 3, and which is characterized in that it comprises a particle removal filter for filtering the organic solvent, and a purification means for passing the organic solvent obtained after the filtration through an ion exchanger to purify the organic solvent.

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