Organic solvent concentration method

Abstract

The present invention dehydrates a liquid mixture while suppressing significant shortening of the service life of a separation membrane. This organic solvent concentration method comprises: a first step for setting, to a first concentration that is higher than a reference concentration, the concentration of an organic solvent in a first liquid which is a liquid mixture of pure water and the organic solvent, and storing the first liquid in a tank; a second step for setting, to a second concentration that is lower than the reference concentration, the concentration of the organic solvent in a second liquid which is a liquid mixture of pure water and the organic solvent, and supplying the second liquid to the first liquid stored in the tank to generate a third liquid in which the concentration of the organic solvent is equal to or higher than the reference concentration; and a third step for concentrating the third liquid by means of a separation membrane. In the second step, the liquid amount of the second liquid supplied to the first liquid is determined on the basis of the first concentration, the liquid amount of the first liquid stored in the tank, and the second concentration.

Description

Organic solvent concentration method

[0001] The technology disclosed in the present specification relates to a concentration technology for a mixture of pure water and an organic solvent.

[0002] Typical substrate processing includes a chemical process in which a chemical solution is discharged onto the substrate, a rinse process in which the chemical solution is rinsed with pure water, and a drying process in which the pure water is replaced with an organic solvent such as IPA (isopropyl alcohol) liquid (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2017-41505

[0004] In the drying process, a mixed liquid of pure water and an organic solvent (organic effluent) is discharged, but in order to reduce the environmental load, it is desirable to separate (dehydrate) the pure water and the organic solvent. Unless otherwise specified, the "mixed liquid" described in this specification refers to a mixed liquid of an organic solvent (IPA) and pure water, or a mixed liquid of an organic solvent (IPA) and water.

[0005] On the other hand, when dehydration is performed using a separation membrane, if the concentration of the organic solvent in the mixed solution is lower than the standard concentration, the service life of the separation membrane may be significantly shortened, resulting in a problem of reduced throughput. Here, the standard concentration refers to the concentration of the organic solvent that is predetermined depending on the type of separation membrane and is recommended for using the separation membrane within an appropriate service life.

[0006] The technology disclosed in the present specification has been made in consideration of the problems described above, and is a technology for dehydrating a mixed liquid while preventing the service life of a separation membrane from being significantly shortened.

[0007] A first aspect of the technology disclosed herein is a method for concentrating an organic solvent, comprising: a first step of storing a first liquid, which is a mixture of pure water and an organic solvent, at a first concentration higher than a reference concentration; a second step of storing a second liquid, which is a mixture of pure water and an organic solvent, at a second concentration lower than the reference concentration; a second step of supplying the second liquid to the first liquid stored in the tank to produce a third liquid having a concentration of the organic solvent equal to or higher than the reference concentration; and a third step of concentrating the third liquid using a separation membrane, wherein the second step supplies the second liquid to the first liquid in an amount determined based on the first concentration, the amount of the first liquid stored in the tank, and the second concentration. A second aspect of the organic solvent concentrating method disclosed herein is related to the first aspect of the organic solvent concentrating method, and the first concentration is 99 wt % or higher. An organic solvent concentrating method as a third aspect of the technology disclosed herein is related to the organic solvent concentrating method as the first or second aspect, and the third step is a step of concentrating the third liquid using the separation membrane in a circulation path including the tank. An organic solvent concentrating method as a fourth aspect of the technology disclosed herein is related to the organic solvent concentrating method as the first or second aspect, and the second step is a step of storing a portion of the third liquid, which has been concentrated to an organic solvent concentration of 99 wt%, in the tank as the first liquid, and discharging the second liquid into the first liquid in an amount that makes the organic solvent concentration equal to or greater than the reference concentration, to produce the third liquid. An organic solvent concentrating method as a fifth aspect of the technology disclosed herein is related to the organic solvent concentrating method as the first or second aspect, and the third step is a step of discharging the pure water separated from the third liquid using the separation membrane. A method for concentrating an organic solvent according to a sixth aspect of the technology disclosed herein is related to the method for concentrating an organic solvent according to the first or second aspect, in which the third step is a step of discharging the organic solvent separated from the third liquid by the separation membrane.A method for concentrating an organic solvent according to a seventh aspect of the technology disclosed herein is related to the method for concentrating an organic solvent according to the first or second aspect, in which the organic solvent is IPA.An organic solvent concentrating method which is an eighth aspect of the technology disclosed in the present specification is related to the organic solvent concentrating method which is the first aspect, in which the first liquid is the mixed liquid which has been recovered from a substrate processing apparatus and then dehydrated by the separation membrane, and the second liquid is recovered from the substrate processing apparatus.

[0008] According to at least the first aspect of the technology disclosed in the present specification, the concentration of the organic solvent in the mixed liquid dehydrated by the separation membrane can be maintained at or above the reference concentration, thereby preventing the service life of the separation membrane from being significantly shortened.

[0009] Furthermore, objects, features, aspects, and advantages associated with the technology disclosed herein will become more apparent from the detailed description and accompanying drawings set forth below.

[0010] FIG. 1 is a plan view schematically showing an example of a substrate processing apparatus; FIG. 2 is a side view schematically showing an example of a processing unit; FIG. 3 is a view schematically showing an example of a first storage box 50a and a second storage box 50b; FIG. 4 is a view showing an example of the relationship between the amount of mixed liquid circulating through a dehydration circulation pipe and the circulation time; FIG. 5 is a view showing an example of the relationship between the concentration of IPA liquid in the mixed liquid circulating through a dehydration circulation pipe and the circulation time; FIG. 6 is a flow chart showing an example of the relationship between the amount of pure water separated by a separation membrane and the circulation time; and FIG. 7 is a flow chart showing an example of an operation in a first storage box.

[0011] Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following embodiments, detailed features are shown for the purpose of explaining the technology, but these are merely examples and are not necessarily essential features for enabling the embodiments to be implemented.

[0012] The drawings are schematic, and for the sake of convenience, components may be omitted or simplified as appropriate. The relative sizes and positions of components shown in different drawings are not necessarily accurately depicted and may be changed as appropriate. Hatching may also be used in drawings such as plan views that are not cross-sectional views to facilitate understanding of the embodiments.

[0013] In the following description, the same components are denoted by the same reference numerals, and their names and functions are also the same. Therefore, detailed descriptions of them may be omitted to avoid duplication.

[0014] Furthermore, in the description given in this specification, when a certain component is described as "comprising," "including," or "having," unless otherwise specified, this is not an exclusive expression that excludes the presence of other components.

[0015] Furthermore, in the description of this specification, even if ordinal numbers such as "first" or "second" are used, these terms are used for convenience to make it easier to understand the contents of the embodiments, and the contents of the embodiments are not limited to the order that may result from these ordinal numbers.

[0016] Furthermore, in the description provided in this specification, terms that indicate specific positions or directions, such as "top," "bottom," "left," "right," "side," "bottom," "front," or "back," may be used, but these terms are used for convenience to facilitate understanding of the contents of the embodiments and have no relation to the positions or directions when the embodiments are actually implemented.

[0017] Furthermore, in the description of the present specification, when "the upper surface of ..." or "the lower surface of ..." is used, it is intended to include not only the upper surface or lower surface of the target component itself, but also a state in which another component is formed on the upper surface or lower surface of the target component. For example, when it is described as "B provided on the upper surface of A," it does not preclude the interposition of another component "C" between A and B.

[0018] <Embodiment> A substrate processing apparatus 100 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a plan view schematically showing an example of the substrate processing apparatus 100.

[0019] The substrate processing apparatus 100 is a so-called single-wafer processing apparatus that processes substrates W to be processed one by one. The substrates W to be processed by the substrate processing apparatus 100 are, for example, semiconductor substrates. The shape of the substrates W to be processed is, for example, a disk shape. Substrates to be processed include, for example, semiconductor wafers, glass substrates for liquid crystal display devices, substrates for flat panel displays (FPDs) such as organic electroluminescence (EL) display devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, glass substrates for photomasks, ceramic substrates, substrates for field emission displays (FEDs), and substrates for solar cells.

[0020] The substrate processing apparatus 100 includes a load port 1 , an indexer robot 2 , a main transport robot 3 , a processing unit 4 , a first storage box 50 a , a second storage box 50 b , and a control unit 6 .

[0021] The load port 1 is an interface for loading and unloading substrates W into and from a carrier C, which is a type of storage container that stores multiple substrates. For example, multiple load ports 1 (three in the example shown in the figure) are provided. The multiple load ports 1 are, for example, arranged in a horizontal row. The carrier C may be of a type that stores substrates W in an enclosed space (for example, a FOUP (Front Opening Unified Pod), a SMIF (Standard Mechanical Inter Face) pod, etc.), or may be of a type that exposes substrates W to the outside air (for example, an OC (Open Cassette), etc.).

[0022] The indexer robot 2 is a transport device that transports substrates W. As an example, the indexer robot 2 is a horizontal articulated robot that includes a pair of hands 21 that hold substrates W and arms 22 connected to each hand 21. The indexer robot 2 also includes a drive mechanism (not shown) for rotating each hand 21 and bending and extending, rotating, and raising and lowering each arm 22. The indexer robot 2 transports substrates W between a carrier C placed on the load port 1 and the main transport robot 3. That is, the indexer robot 2 accesses a carrier C placed on the load port 1 to perform an unloading operation (i.e., an operation of removing a substrate W contained in the carrier C with the hand 21) and a loading operation (i.e., an operation of placing a substrate W held by the hand 21 into the carrier C). The indexer robot 2 also accesses a transfer position 40 to transfer substrates W between the indexer robot 2 and the main transport robot 3.

[0023] The main transport robot 3 is a transport device that transports substrates W. As an example, the main transport robot 3 is a horizontal articulated robot that includes a pair of hands 31 that hold substrates W and arms 32 connected to each hand 31. The main transport robot 3 also includes a drive mechanism (not shown) for rotating each hand 31 and bending and extending, rotating, and raising and lowering each arm 32. The main transport robot 3 transports substrates W between the indexer robot 2 and each processing unit 4. That is, the main transport robot 3 accesses the transfer position 40 to transfer substrates W to and from the indexer robot 2. The main transport robot 3 also accesses the processing unit 4 to perform a load operation (i.e., an operation of loading a substrate W held by the hand 31 into the processing unit 4) and an unload operation (i.e., an operation of unloading a substrate W from the processing unit 4 using the hand 31).

[0024] The processing units 4 perform predetermined processing using processing liquids (e.g., chemical liquids, rinse liquids, and IPA liquids) on the substrates W. Here, for example, a plurality of (e.g., three) processing units 4 stacked vertically form a tower, and a plurality of such towers (four in the illustrated example) are provided so as to surround the main transport robot 3. The specific configuration of the processing units 4 will be described later.

[0025] In the first storage box 50a, the organic solvent (IPA liquid in this embodiment) mixed with pure water is recovered from the processing unit 4, and the recovered organic solvent is concentrated and purified before being supplied to the second storage box 50b and further to the processing unit 4. The supplied organic solvent can be reused for substrate processing. As an example, a first storage box 50a may be provided in one-to-one correspondence with each of a plurality of towers, and each first storage box 50a may recover and supply IPA liquid to each processing unit 4 included in the corresponding tower. The specific configuration of the first storage box 50a will be described later.

[0026] The control unit 6 controls the operation of each component of the substrate processing apparatus 100 (the load port 1, the indexer robot 2, the main transport robot 3, the processing unit 4, and each component in the first storage box 50a). The control unit 6 is configured, for example, by a general computer having electrical circuits. As an example, the control unit 6 is configured to include a CPU (Central Processor Unit) as a central processing unit that performs various arithmetic processing (data processing), a ROM (Read Only Memory) in which basic programs and the like are stored, a RAM (Random Access Memory) used as a working area when the CPU performs predetermined processing (data processing), a storage device configured by a nonvolatile storage device such as a flash memory or a hard disk drive, and a bus line connecting these components to each other. A program that defines the processing executed by the control unit 6 may be stored in the storage device or RAM. In this case, for example, the CPU may execute the program, causing each unit of the substrate processing apparatus 100 to be controlled by the control unit 6, and the processing defined by the program may be performed in the substrate processing apparatus 100. That is, the CPU may execute the program, causing a circuit that performs the processing defined by the program to be realized in the control unit 6. However, part or all of the control performed by the control unit 6 (part or all of the circuit realized by the control unit 6) may be executed (realized) by hardware such as a dedicated logic circuit.

[0027] <Processing Unit> The processing unit 4 will be described with reference to Fig. 2. Fig. 2 is a side view schematically showing an example of the processing unit 4.

[0028] <Configuration of Processing Unit> The processing unit 4 performs a predetermined process using a processing liquid (e.g., a chemical liquid, a rinse liquid, and an IPA liquid) on the substrate W. The processing unit 4 includes, for example, a spin chuck 41, a cup 42, and a nozzle 43. The spin chuck 41, the cup 42, and the nozzle 43 are housed in a processing chamber 44.

[0029] The spin chuck 41 holds the substrate W in a horizontal position (the thickness direction of the substrate W is aligned with the up-down direction (vertical direction)) and rotates the substrate W around an axis (rotation axis) A extending vertically through the center of its main surface. Specifically, the spin chuck 41 includes, for example, a spin base 411. The spin base 411 is a disk-shaped member and is positioned with its thickness aligned with the up-down direction. A plurality of chuck pins 412 are provided on the upper surface of the spin base 411. The plurality of chuck pins 412 are arranged at equal intervals along a circumference corresponding to the periphery of the substrate W. A link mechanism (not shown) that moves the plurality of chuck pins 412 between an abutment position and an release position is connected to the plurality of chuck pins 412. The "abutment position" is a position where the chuck pins 412 abut (contact) with the periphery of the substrate W. The "release position" is a position where the chuck pins 412 are spaced apart from the periphery of the substrate W. When each of the chuck pins 412 is positioned at the abutment position, the substrate W is held (chucked) in a horizontal position above the spin base 411. When each of the chuck pins 412 is positioned at the release position, the substrate W is released from its hold. The link mechanism switches the positions of the chuck pins 412 in response to instructions from the control unit 6. That is, the timing of holding the substrate W, the timing of releasing the substrate W, and the like are controlled by the control unit 6. The spin base 411 is connected to a spin motor 414 via a shaft 413 that is provided coaxially with the rotation axis A. The shaft 413 and the spin motor 414 are housed in a cover 415. The spin motor 414 rotates the shaft 413 about the rotation axis A. This causes the spin base 411, and ultimately the substrate W held above it, to rotate about the rotation axis A. The spin motor 414 rotates the spin base 411 in response to instructions from the control unit 6. That is, the rotation speed of the spin base 411 (and thus the substrate W), the timing at which the rotation starts, the timing at which the rotation ends, etc. are controlled by the control unit 6 .

[0030] The cup 42 receives the processing liquid discharged from the substrate W held and rotated by the spin chuck 41. Specifically, the cup 42 includes, for example, a cylindrical guide portion 421 arranged coaxially with the rotation axis A, an inclined portion 422 connected to the upper end of the guide portion 421 and tapering upward (approaching the radially inner side of the spin chuck 41), and a liquid receiving portion 423 connected to the lower end of the guide portion 421 and forming an upwardly opening annular groove. The liquid receiving portion 423 is provided with cup-side recovery pipes (specifically, a cup-side recovery pipe (not shown) for the chemical liquid and a cup-side recovery pipe 424 for the IPA liquid) for recovering the liquid received therein. A cup lifting mechanism 425 is connected to the cup 42, which raises and lowers the cup 42 between a lower position and an upper position. The "lower position" is a position where the upper end of the cup 42 (specifically, the upper end of the inclined portion 422) is located below the substrate W held by the spin chuck 41. The "upper position" is a position where the upper end of the cup 42 is located above the substrate W held by the spin chuck 41. The cup lifting mechanism 425 lifts and lowers the cup 42 in response to an instruction from the control unit 6. That is, the position of the cup 42 is controlled by the control unit 6.

[0031] The nozzles 43 eject the processing liquid toward the upper surface of the substrate W held by the spin chuck 41. Here, for example, a separate nozzle 43 is provided for each type of processing liquid. That is, a nozzle 43 that ejects a chemical liquid (hereinafter also referred to as a "chemical liquid nozzle 43a"), a nozzle 43 that ejects a rinse liquid (hereinafter also referred to as a "rinse liquid nozzle 43b"), and a nozzle 43 that ejects an IPA liquid (hereinafter also referred to as an "IPA nozzle 43c") are provided.

[0032] The chemical nozzle 43a discharges a chemical solution toward the upper surface of the substrate W held on the spin chuck 41. The chemical nozzle 43a is connected to a chemical solution supply source 433a via a chemical solution pipe 432a having a chemical solution valve 431a inserted therein. When the chemical solution valve 431a is opened, the chemical solution is supplied to the chemical solution nozzle 43a through the chemical solution pipe 432a, and the chemical solution is discharged from the chemical solution nozzle 43a. The chemical solution valve 431a is opened and closed in response to an instruction from the control unit 6. That is, the discharge timing of the chemical solution from the chemical solution nozzle 43a is controlled by the control unit 6. The chemical solution is, for example, hydrofluoric acid. However, the chemical solution is not limited to hydrofluoric acid, and may be a solution containing at least one of sulfuric acid, acetic acid, nitric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, ammonia water, hydrogen peroxide water, organic acid (e.g., citric acid, oxalic acid, etc.), organic alkali (e.g., TMAH: tetramethylammonium hydroxide, etc.), surfactant, and corrosion inhibitor.

[0033] The rinse liquid nozzle 43b ejects a rinse liquid toward the upper surface of the substrate W held on the spin chuck 41. For example, the rinse liquid is water or pure water. The rinse liquid nozzle 43b is connected to a rinse liquid supply source 433b via a rinse liquid pipe 432b in which a rinse liquid valve 431b is inserted. When the rinse liquid valve 431b is opened, the rinse liquid is supplied to the rinse liquid nozzle 43b through the rinse liquid pipe 432b, and the rinse liquid is ejected from the rinse liquid nozzle 43b. The rinse liquid valve 431b is opened or closed in response to instructions from the control unit 6.

[0034] The IPA nozzle 43c ejects IPA liquid (i.e., a liquid containing IPA as a main component) toward the upper surface of the substrate W held on the spin chuck 41. The IPA nozzle 43c is connected to the second storage box 50b via an IPA pipe 432c having an IPA valve 431c inserted therein. When the IPA valve 431c is opened, the IPA liquid is supplied to the IPA nozzle 43c through the IPA pipe 432c, and the IPA liquid is ejected from the IPA nozzle 43c. The IPA valve 431c is opened and closed in response to instructions from the control unit 6. That is, the ejection timing of the IPA liquid from the IPA nozzle 43c is controlled by the control unit 6.

[0035] At least one of the chemical liquid nozzle 43 a, the rinse liquid nozzle 43 b, and the IPA nozzle 43 c may be connected to a nozzle moving mechanism that moves the nozzle between a processing position and a retracted position. The "processing position" is a position where the processing liquid ejected from the nozzles 43 a, 43 b, and 43 c is supplied to the substrate W held on the spin chuck 41. The "retracted position" is a position where the nozzles 43 a, 43 b, and 43 c are located outside (radially outward from) the periphery of the substrate W held on the spin chuck 41 when viewed from above. In this case, the nozzle moving mechanism moves the nozzles 43 a, 43 b, and 43 c in response to an instruction from the control unit 6. That is, the positions of the nozzles 43 a, 43 b, and 43 c are controlled by the control unit 6.

[0036] <Operation of Processing Unit> A description will be given of an example of the operation of the processing unit 4. The operation performed in the processing unit 4 is performed under the control of the control unit 6 (i.e., by the control unit 6 controlling the chuck pin 412, the spin motor 414, the cup lifting mechanism 425, the chemical liquid valve 431 a, the rinse liquid valve 431 b, the IPA valve 431 c, etc.).

[0037] When the substrate W is carried into the processing chamber 44 by the main transport robot 3, the spin chuck 41 holds the substrate W. Then, the spin chuck 41 starts to rotate.

[0038] In this state, the chemical valve 431a is opened. Then, the chemical nozzle 43a ejects the chemical toward the upper surface of the substrate W, which is held and rotated by the spin chuck 41. This causes the chemical to be supplied to the entire upper surface of the substrate W, and the substrate W is treated with the chemical (chemical treatment process). For example, when hydrofluoric acid is used as the chemical, foreign matter such as particles is removed from the substrate W. During the chemical treatment process, the cup 42 is positioned in the upper position. Therefore, the chemical that has splashed around the substrate W is received by the cup 42. That is, the chemical that has splashed around the substrate W is received by the inclined portion 422, guided downward by the guide portion 421, and collected in the liquid receiving portion 423. The chemical received by the cup 42 (i.e., the chemical collected in the liquid receiving portion 423) is collected through a cup-side chemical recovery pipe (not shown).

[0039] When a predetermined time has elapsed since the start of the discharge of the chemical liquid, the chemical liquid valve 431a is closed. This stops the discharge of the chemical liquid from the chemical liquid nozzle 43a. Subsequently, the rinse liquid valve 431b is opened. This causes the rinse liquid to be discharged from the rinse liquid nozzle 43b toward the upper surface of the substrate W held and rotated by the spin chuck 41. This causes the rinse liquid to be supplied to the entire upper surface of the substrate W, and the chemical liquid adhering to the substrate W is washed away by the rinse liquid (rinse processing step). The cup 42 remains in the upper position even during the rinse processing step. Therefore, the chemical liquid and rinse liquid splashed around the substrate W are received by the cup 42. The chemical liquid and rinse liquid received by the cup 42 are collected through a cup-side chemical liquid recovery pipe (not shown).

[0040] After a predetermined time has elapsed since the start of the discharge of the rinse liquid, the rinse liquid valve 431b is closed. This stops the discharge of the rinse liquid from the rinse liquid nozzle 43b. Subsequently, the IPA valve 431c is opened. This causes the IPA nozzle 43c to discharge the IPA liquid toward the upper surface of the substrate W held and rotated by the spin chuck 41. This causes the IPA liquid to be supplied to the entire upper surface of the substrate W, and the rinse liquid adhering to the substrate W is replaced with the IPA liquid (IPA supplying step). The cup 42 remains in the upper position even during the IPA supplying step. Therefore, the mixture of the rinse liquid and the IPA liquid splashed around the substrate W is collected by the cup 42. The mixture of the rinse liquid and the IPA liquid collected by the cup 42 is collected through the cup-side recovery pipe 424 for IPA.

[0041] After a predetermined time has elapsed since the start of the supply of IPA liquid, the IPA valve 431c is closed. This stops the IPA liquid from being discharged from the IPA nozzle 43c. At this stage, the rinse liquid on the substrate W is completely replaced with the IPA liquid, and a liquid film of the IPA liquid is formed covering the entire upper surface of the substrate W. The spin chuck 41 then starts rotating at high speed. This causes the substrate W to rotate at high speed, and the IPA liquid on the substrate W is scattered around the substrate W by centrifugal force (spin-drying process). The cup 42 remains in the upper position while the substrate W is being rotated at high speed. Therefore, the IPA liquid splashed around the substrate W is collected by the cup 42. The IPA liquid collected by the cup 42 is collected through the IPA cup-side recovery pipe 424.

[0042] When a predetermined time has elapsed since the high-speed rotation of the spin chuck 41 began, the rotation of the spin chuck 41 is stopped. At this stage, the IPA liquid has been removed from the substrate W, and the substrate W has been dried. The dried substrate W is then transported out of the processing chamber 44 by the main transport robot 3.

[0043] This completes the series of processes for one substrate W. In the processing unit 4, the series of operations described above is repeated to process a plurality of substrates W one by one.

[0044] <First Storage Box, Second Storage Box> The configuration of the first storage box 50a and the second storage box 50b will be described with reference to Fig. 3. Fig. 3 is a diagram schematically illustrating an example of the first storage box 50a and the second storage box 50b.

[0045] The first storage box 50a accommodates a recovery tank 502, a purification tank 504, and a wastewater tank 1002. The second storage box 50b accommodates a supply tank 506. As an example, the first storage box 50a is arranged outside the outer wall 100a of the substrate processing apparatus 100 (for example, below (underground) the clean room in which the substrate processing apparatus 100 is installed), and the second storage box 50b is arranged inside the outer wall 100a of the substrate processing apparatus 100 ( FIG. 1 ).

[0046] <Recovery Tank> The recovery tank 502 is connected to the cup 42 through a recovery pipe 512. That is, the recovery tank 502 is connected to one end of the recovery pipe 512, and the cup 42 (specifically, the cup-side recovery pipe 424 connected to the cup 42) is connected to the other end of the recovery pipe 512. Here, for example, the recovery pipe 512 is connected to the cups 42 provided in each of a plurality of processing units 4 belonging to the same tower. A valve 511 is inserted in the recovery pipe 512. The mixed liquid recovered from the cup 42 is stored in the recovery tank 502 via the recovery pipe 512. The concentration and liquid volume of the mixed liquid flowing through the recovery pipe 512 may be measured by a concentration sensor (not shown) and a flow rate sensor (not shown) provided in the recovery pipe 512, or may be determined from the processing conditions of the substrate processing.

[0047] A circulation pipe (spin-dry circulation pipe 514) is connected to the recovery tank 502. The spin-dry circulation pipe 514 forms a circulation path through which the liquid stored in the recovery tank 502 flows out of the recovery tank 502 and returns to the recovery tank 502. A drainage tank 1002 is also connected to the recovery tank 502 via a pipe 1003. The drainage tank 1002 stores the liquid drained from the recovery tank 502 when a valve 1003A is opened under the control of the control unit 6.

[0048] A dehydrator 516 is inserted into the dehydration circulation pipe 514. The dehydrator 516 includes a separation membrane 516a that separates the deionized water from the mixture of IPA and deionized water, and a dehydration housing 516b that houses the separation membrane 516a. A discharge pipe 515 is connected to the dehydrator 516 for discharging the deionized water (DIW) separated from the mixture. For example, the separation membrane 516a is a separation membrane that dehydrates the mixture by utilizing the difference in size between IPA molecules and water molecules. The separation membrane 516a may be a membrane that is permeable to water molecules but not to IPA molecules.

[0049] The separation membrane 516a is, for example, a zeolite membrane formed of zeolite. Zeolite is a tetrahedral structure consisting of basic units (e.g., (SiO ４ ) ４－ and (AlO ４ ) ５－ The separation membrane 516a has a crystalline structure in which water molecules and IPA molecules (basic units containing at least one of the above) are interconnected. The separation membrane 516a separates the two by utilizing the difference in size between the two (allowing only water molecules to pass through), and is expected to be used when the concentration (reference concentration) of the IPA liquid in the liquid is 50 wt % or higher. Zeolite membranes have the property of allowing water molecules to pass through but not IPA molecules to pass through.

[0050] The separation membrane 516a is not limited to a zeolite membrane. For example, the separation membrane 516a may be an organic separation membrane. The organic separation membrane is an organic membrane formed of, for example, polyvinyl alcohol, chitosan, polyimide, or the like. The separation membrane 516a may also be a CNT (carbon nanotube) separation membrane. The CNT separation membrane is a membrane obtained by adding carbon nanotubes to a membrane such as polyamide. The separation membrane 516a may also be formed of a two-dimensional material. The two-dimensional material is a material composed of one layer of atoms, and specifically, molybdenum sulfide (MoS ２), a composite atomic layer compound of an early transition metal (titanium, vanadium, etc.) and a light element (carbon or nitrogen), etc. The separation membrane 516a may be formed of a metal organic framework (MOF) material or a carbon material (e.g., graphene, graphene oxide, etc.).

[0051] In the dehydration circulation pipe 514, a valve 522, a dehydration-side liquid pump 518, a temperature regulator 524 having cooling and heating capabilities, a dehydrator 516, and a valve 520 are arranged in this order from the recovery tank 502 along the dehydration circulation pipe 514. Note that a heater may be provided instead of the temperature regulator 524.

[0052] Various sensors are inserted in the dehydration circulation pipe 514. For example, a concentration sensor 526 that measures the concentration of an organic solvent (here, for example, an IPA liquid) in the fluid flowing through the dehydration circulation pipe 514, a flow rate sensor 532 (flow meter) that measures the flow rate of the fluid flowing through the dehydration circulation pipe 514, a pressure sensor 528 that detects the pressure of the fluid flowing through the dehydration circulation pipe 514, a temperature sensor 530 that detects the temperature of the fluid flowing through the dehydration circulation pipe 514, and the like are inserted in the dehydration circulation pipe 514.

[0053] The concentration sensor 526 is inserted, for example, downstream of the dehydrator 516 and upstream of the recovery tank 502. The flow rate sensor 532 is inserted, for example, downstream of the recovery tank 502 and upstream of the dehydration-side liquid feed pump 518. The pressure sensor 528 is inserted, for example, downstream of the dehydration-side liquid feed pump 518 and upstream of the temperature regulator 524. The temperature sensor 530 is inserted, for example, upstream of the dehydrator 516 and downstream of the temperature regulator 524.

[0054] <Purification Tank> Purification tank 504 is connected to dehydration circulation pipe 514 through first liquid supply pipe 534. That is, purification tank 504 is connected to one end of first liquid supply pipe 534, and dehydration circulation pipe 514 is connected to the other end of first liquid supply pipe 534. As an example, the other end of first liquid supply pipe 534 is connected to a position in dehydration circulation pipe 514 that is downstream of temperature sensor 530 and upstream of dehydrator 516. A valve 536 is inserted in first liquid supply pipe 534.

[0055] A circulation pipe (purification circulation pipe 538) is connected to the purification tank 504. The purification circulation pipe 538 forms a circulation path through which the mixed liquid stored in the purification tank 504 flows out of the purification tank 504 and returns to the purification tank 504.

[0056] A purification-side liquid transfer pump 540, a temperature regulator 546, a filter 544, a particle detector 543, and a valve 542 are arranged in this order along the purification circulation pipe 538 from the purification tank 504. An air vent pipe 539 is connected to the filter 544.

[0057] The particle detector 543 is, for example, an optical detector, and is a device that samples the concentrated mixed liquid flowing through the purification circulation pipe 538 and detects particles present in the sampled concentrated mixed liquid based on a response wavelength obtained by measuring the concentrated mixed liquid, etc. The filter 544 is, for example, a filter that removes metal elements from the fluid flowing through the purification circulation pipe 538, or a filter that removes particles from the fluid flowing through the purification circulation pipe 538. The filter 544 is made of, for example, polytetrafluoroethylene (PTFE).

[0058] The temperature regulator 546 is a device having both cooling and heating capabilities, and may be, for example, a device that performs electronic cooling using a Peltier element (a so-called electronic cooling / heating unit).

[0059] Various sensors are inserted in the purification circulation pipe 538. For example, a temperature sensor 548 that detects the temperature of the fluid flowing through the purification circulation pipe 538, a pressure sensor 550 that detects the pressure of the fluid flowing through the purification circulation pipe 538, and the like are inserted in the purification circulation pipe 538. The temperature sensor 548 is inserted, for example, in a position upstream of the filter 544 and downstream of the temperature regulator 546. The pressure sensor 550 is inserted, for example, in a position downstream of the purification-side liquid feed pump 540 and upstream of the temperature regulator 546.

[0060] <Supply Tank> The supply tank 506 is connected to the purification circulation pipe 538 through the second liquid supply pipe 552. That is, the supply tank 506 is connected to one end of the second liquid supply pipe 552, and the purification circulation pipe 538 is connected to the other end of the second liquid supply pipe 552.

[0061] As an example, the other end of the second liquid supply pipe 552 is connected to the purification circulation pipe 538 at a position upstream of the filter 544 and downstream of the temperature regulator 546. A valve 555 is inserted in the second liquid supply pipe 552.

[0062] The supply tank 506 is connected to an IPA supply source 558 through an IPA supply pipe 556. That is, one end of the IPA supply pipe 556 is connected to the supply tank 506, and the other end of the IPA supply pipe 556 is connected to the IPA supply source 558. The IPA supply source 558 is a supply source of unused IPA liquid (e.g., IPA liquid with a concentration of 99.8 wt % or more) that has never been supplied to a substrate W. An IPA supply valve 560 is inserted into the IPA supply pipe 556.

[0063] The supply tank 506 is connected to the IPA nozzle 43c through a third liquid supply pipe 562. That is, the supply tank 506 is connected to one end of the third liquid supply pipe 562, and the IPA nozzle 43c (specifically, the IPA pipe 432c connected to the IPA nozzle 43c) is connected to the other end of the third liquid supply pipe 562. Here, for example, the third liquid supply pipe 562 is connected to the IPA nozzles 43c provided in each of the multiple processing units 4 belonging to the same tower.

[0064] A pump (supply-side liquid feed pump 564) is inserted into the third liquid feed pipe 562. A filter 566 is inserted into the third liquid feed pipe 562 at a position downstream of the supply-side liquid feed pump 564. A temperature regulator 568 is inserted into the third liquid feed pipe 562 at a position upstream of the filter 566 and downstream of the supply-side liquid feed pump 564. The filter 566 is, for example, a filter that removes metal elements from the fluid flowing through the third liquid feed pipe 562, or a filter that removes particles from the fluid flowing through the third liquid feed pipe 562. The filter 566 is made of, for example, polytetrafluoroethylene (PTFE).

[0065] Various sensors are inserted in the third liquid feed pipe 562. For example, a temperature sensor 570 that detects the temperature of the fluid flowing through the third liquid feed pipe 562, a pressure sensor 572 that detects the pressure of the fluid flowing through the third liquid feed pipe 562, and the like are inserted in the third liquid feed pipe 562. The temperature sensor 570 is inserted, for example, at a position upstream of the filter 566 and downstream of the temperature regulator 568. The pressure sensor 572 is inserted, for example, at a position downstream of the supply-side liquid feed pump 564 and upstream of the temperature regulator 568.

[0066] <Operations in First Storage Box 50a> An example of operations in the first storage box 50a will be described. The operations performed in the first storage box 50a are performed under the control of the control unit 6 (i.e., by the control unit 6 controlling the valve 511, the spinning-side liquid supply pump 518, the valves 520, 522, the temperature regulator 524, the valves 536, 542, and 555, etc.). Figure 7 is a flowchart showing an example of operations in the first storage box.

[0067] First, a first liquid, which is a mixed liquid having a higher concentration than the reference concentration, is stored (step ST1 in FIG. 7 ). The first liquid may be a mixed liquid recovered from the cup 42, passed through the recovery pipe 512, and stored in the recovery tank 502. Alternatively, the first liquid may be a mixed liquid recovered from the cup 42, passed through the recovery pipe 512, stored in the recovery tank 502, and then dehydrated in the dehydrator 516 provided in the dehydration circulation pipe 514. The concentration of IPA in the first liquid is higher than the reference concentration (e.g., 99 wt %). In other words, the first liquid is a mixed liquid stored in the recovery tank 502 and has a higher concentration than the reference concentration. Although not shown, the volume of the first liquid stored in the recovery tank 502 may be measured by a liquid volume sensor, a liquid level sensor, a level sensor, or the like. The concentration of IPA (organic solvent) contained in the first liquid corresponds to the first concentration in the present invention. The first concentration may be measured by a concentration sensor (not shown) provided inside the recovery tank 502, or may be determined from the processing conditions for substrate processing. Information on the first concentration and the amount of the first liquid is sent to the control unit 6. The step of storing the first liquid in the recovery tank 502 corresponds to the first step in the present invention.

[0068] Next, valve 511 is opened, and the second liquid, which is a mixed liquid flowing through recovery pipe 512, is supplied to recovery tank 502. The second liquid is, for example, a liquid recovered from the substrate processing apparatus by mixing IPA liquid, an organic solvent, after being used in substrate processing with deionized water that was also used in substrate processing. The proportion of IPA liquid in the second liquid can vary greatly. The concentration of IPA liquid (organic solvent) contained in the second liquid corresponds to the second concentration in the present invention, and the second concentration is lower than the reference concentration. In other words, the second liquid is a mixed liquid recovered from cup 42 via recovery pipe 512 and has a lower concentration than the reference concentration. The second concentration and the flow rate (liquid volume) of the second liquid are measured by a concentration sensor (not shown) and a flow rate sensor (not shown) provided in recovery pipe 512 and sent to control unit 6. Based on the volume, first concentration, and second concentration of the first liquid, the second liquid is supplied to the first liquid stored in the recovery tank 502 to generate a third liquid having a reference concentration or higher (step ST2 in FIG. 7 ). The process of generating the third liquid corresponds to the second process in the present invention. The volume of the second liquid to be supplied to the first liquid is determined by the control unit 6 based on the volume, first concentration, and second concentration of the first liquid, as described below. The reference concentration of the separation membrane 516a may also be preset in the control unit 6.

[0069] Next, the third liquid is brought into contact with the separation membrane 516a and concentrated to an IPA concentration of 99 wt %, thereby producing a concentrated IPA liquid (step ST3 in FIG. 7). The process of bringing the third liquid into contact with the separation membrane 516a and dehydrating it corresponds to the third step in the present invention.

[0070] Next, a portion of the concentrated IPA liquid circulating through the dehydration circulation pipe 514 is sent to the purification circulation pipe 538 (step ST4-1 in FIG. 7), or is drained into the drain tank 1002 (step ST4-2 in FIG. 7). The concentrated IPA liquid sent to the purification circulation pipe 538 in step ST4-1 in FIG. 7 is purified by a filter 544 provided in the purification circulation pipe 538 and is re-discharged onto the substrate in the substrate processing apparatus.

[0071] Next, the concentrated IPA liquid (first liquid) remaining in the recovery tank 502 is mixed with the second liquid flowing through the recovery pipe 512 to generate a third liquid, and the generated third liquid is brought into contact with the separation membrane 516a (step ST5 in Figure 7).

[0072] Steps ST1 to ST5 in FIG. 7 are repeatedly performed.

[0073] In the recovery tank 502, the third liquid is circulated through a dehydration circulation pipe 514, and a dehydrator 516 provided in the dehydration circulation pipe 514 dehydrates the mixed liquid into pure water. That is, at least a portion of the third liquid is passed through (contacted with) a separation membrane 516a in the dehydrator 516 to separate the IPA liquid, which is the organic solvent in the third liquid, from the pure water (step ST3 in FIG. 7 above). The concentration of the dehydrated third liquid is measured appropriately by a concentration sensor 526, and the dehydrated third liquid is repeatedly circulated through the dehydration circulation pipe 514 and dehydrated until the IPA concentration of the third liquid reaches a desired concentration. Meanwhile, the pure water separated from the third liquid is discharged through a discharge pipe 515. Although not shown, the amount of the third liquid stored in the recovery tank 502 may be measured by a liquid volume sensor, a liquid level sensor, a level sensor, or the like provided in the recovery tank 502. The concentration of the third liquid stored in the recovery tank 502 may be measured by a concentration sensor (not shown) provided in the recovery tank 502. Information on the measured volume and concentration of the third liquid is sent to the control unit 6.

[0074] When the concentration of the IPA liquid in the third liquid measured by the concentration sensor 526 reaches the desired concentration (for example, 99 wt % as the concentration of the IPA liquid to be used for substrate processing), the valve 536 is opened, and as described below, a portion of the third liquid (concentrated IPA liquid) circulating through the dehydration circulation pipe 514 is stored in the purification tank 504 via the first liquid supply pipe 534 (step ST4 in Figure 7 above).

[0075] In the purification tank 504, the concentrated IPA liquid is circulated through a purification circulation pipe 538 and purified by a filter 544 provided in the purification circulation pipe 538. That is, by passing the concentrated IPA liquid through the filter 544, metal elements, particles, and the like in the concentrated IPA liquid are removed. The concentrated IPA liquid is repeatedly purified by circulating through the purification circulation pipe 538 until the cleanliness measured by the particle detector 543 reaches a desired value.

[0076] After the cleanliness of the concentrated IPA liquid measured by the particle detector 543 reaches a desired value, the valve 555 is opened to allow the concentrated IPA liquid to be stored in the supply tank 506 via the second liquid supply pipe 552 .

[0077] As described above, the second liquid used in substrate processing mixes with the first liquid stored in the recovery tank 502 to become the third liquid, which is then circulated through the dehydration circulation pipe 514 to be dehydrated (concentrated) to become concentrated IPA liquid, and is further purified by circulating through the purification circulation pipe 538. However, the concentration of the IPA liquid in the second liquid at the time it is supplied to the recovery tank 502 varies greatly depending on the type of substrate processing, etc.

[0078] On the other hand, the separation membrane 516a of the dehydrator 516 provided in the dehydration circulation pipe 514 has a concentration range suitable for use. For example, it is recommended to use a mixed solution with an IPA liquid concentration of 50 wt% or more as the reference concentration of the zeolite membrane (i.e., the IPA liquid concentration that is predetermined depending on the type of separation membrane and recommended for using the separation membrane within an appropriate service life). Zeolite membranes do not allow IPA to pass through, but allow water to pass through. If used with a mixed solution with an IPA liquid concentration of less than 50 wt%, the proportion of water molecules passing through the separation membrane 516a exceeds the allowable value, causing partial dissolution of the crystalline structure that constitutes the separation membrane 516a, and significantly shortening the service life of the separation membrane 516a.

[0079] Therefore, in this embodiment, as described above, the third liquid is circulated through the spin circulation pipe 514, and a portion of the concentrated IPA liquid is sent to the purification tank 504 through the first liquid sending pipe 534, while a portion of the concentrated IPA liquid remains in the recovery tank 502 as the first liquid (step ST4 in FIG. 7 described above). The amount of the first liquid remaining in the recovery tank 502 is measured, for example, by a liquid volume sensor or a level sensor provided in the recovery tank 502, and information on the amount of the first liquid is sent to the control unit 6. The first concentration is measured by the concentration sensor provided in the recovery tank 502 described above, and information on the first concentration is sent to the control unit 6. In other words, the control unit 6 obtains information on the amount of the first liquid and information on the first concentration. In addition, the control unit 6 obtains information on the second concentration from a concentration sensor provided in the recovery pipe 512 and the processing conditions for substrate processing. By acquiring information on the volume of the first liquid, the first concentration, and the second concentration, the control unit 6 calculates the volume of the second liquid to be supplied to the first liquid remaining in the recovery tank 502 so that the third liquid has a reference concentration or higher. A mixed liquid of IPA and pure water (second liquid) is added to the first liquid remaining in the recovery tank 502 from the recovery pipe 512 so that the concentration of the first liquid is equal to or higher than the reference concentration determined for the separation membrane 516a (step ST5 in FIG. 7 above). In this case, the control unit 6 controls the volume of the second liquid to be added to the recovery tank 502.

[0080] Specifically, first, the amount of concentrated IPA liquid (for example, an IPA liquid with a concentration of 99 wt %) to be left in the recovery tank 502 is determined. For example, assume that 25.3 L of concentrated IPA liquid with a concentration of 99 wt % is stored in the recovery tank 502, which has a capacity of 50 L (liters). Then, the control unit 6 adjusts the opening / closing degree of the valve 536 to send a portion of the concentrated IPA liquid, 6.3 L, to the purification tank 504, and 19 L of concentrated IPA liquid (first liquid) is left in the recovery tank 502.

[0081] Next, the control unit 6 adjusts the opening / closing degree of the valve 511 to control the amount of the second liquid, which is newly added via the recovery pipe 512 after the substrate processing, so that the concentration of the IPA liquid will be equal to or higher than the reference concentration when added to the concentrated IPA liquid (first liquid) remaining in the recovery tank 502. Specifically, the control unit 6 acquires information on the amount of the first liquid and information on the first concentration, and calculates the amount of the second liquid to be supplied to the first liquid by acquiring information on the second concentration. More specifically, the control unit 6 calculates the amount of the second liquid so that the value obtained by dividing the sum of the amount of IPA liquid contained in the first liquid and the amount of IPA liquid contained in the second liquid by the amount of the third liquid is equal to or higher than the reference concentration. In other words, the control unit 6 calculates the volume of the second liquid so that the sum of the first concentration multiplied by the volume of the first liquid and the second concentration multiplied by the volume of the second liquid, divided by the volume of the third liquid, is equal to or greater than the reference concentration. More specifically, supplying 31 L of the second liquid with an IPA concentration of 20 wt% to 19 L of the first liquid produces 50 L of the third liquid with a concentration equal to or greater than the reference concentration (50 wt%). The total volume of the concentrated IPA (first liquid) remaining in the recovery tank 502 plus the second liquid is preferably adjusted to correspond to the capacity of the recovery tank 502, for example. Furthermore, if it is expected that the IPA concentration of the second liquid will become even lower, the volume of the first liquid remaining in the recovery tank 502 can be increased.

[0082] 4 is a diagram showing an example of the relationship between the amount of the mixed liquid circulating through the dehydration circulation pipe 514 and the circulation time. In FIG. 4, the vertical axis represents the amount of the mixed liquid (unit: relative value), and the horizontal axis represents the circulation time. The circulation time is defined as the time it takes for the mixed liquid to be sufficiently concentrated and for the IPA concentration to approach 99 wt %. A zeolite membrane is assumed to be used as the separation membrane for dehydrating the pure water from the mixed liquid, and the reference concentration is assumed to be 50 wt %.

[0083] 4 , the mixed liquid circulating through the dehydration circulation pipe 514 gradually decreases in volume over each circulation unit time 1000 as the pure water is separated by the separation membrane 516a and discharged from the discharge pipe 515, and when the concentration of the IPA liquid sufficiently increases from the reference concentration, the volume becomes approximately constant. Then, when a concentrated mixed liquid (IPA liquid concentration is 99 wt %) is generated, a portion of it is sent to the purification tank 504 by the control unit 6, and the volume of the liquid decreases at the end of each circulation unit time, and at approximately the same time (in other words, at the start of the next circulation unit time), the unconcentrated mixed liquid after substrate processing is added via the recovery pipe 512, thereby increasing the volume of the liquid.

[0084] 5 is a diagram showing an example of the relationship between the concentration of the IPA liquid in the mixed solution circulating through the dehydration circulation pipe 514 and the circulation time. In FIG. 5, the vertical axis represents the concentration [%] of the IPA liquid in the mixed solution, and the horizontal axis represents the circulation time. Note that the circulation time is defined as 1, which is the time it takes for the mixed solution to be sufficiently concentrated and for the IPA liquid concentration to approach 99 wt %. In addition, a zeolite membrane is assumed to be used as the separation membrane for dehydrating the pure water from the mixed solution, and the reference concentration is assumed to be 50 wt %.

[0085] 5 , the concentration of the IPA liquid circulating through the dehydration circulation pipe 514 gradually increases from the reference concentration over each circulation unit time of 1000 as the pure water is separated by the separation membrane 516a and discharged from the discharge pipe 515. When the concentration of the IPA liquid reaches approximately 99 wt % at the end of each circulation unit time (when a concentrated mixture is produced), the concentration of the IPA liquid becomes substantially constant. Then, a portion of the IPA liquid is sent to the purification tank 504 by the control unit 6, and the unconcentrated mixture after substrate processing is added via the recovery pipe 512, so that the concentration of the IPA liquid decreases to the reference concentration at the start of the next circulation unit time.

[0086] 6 is a diagram showing an example of the relationship between the amount of pure water separated by the separation membrane 516a and the circulation time. In FIG. 6, the vertical axis represents the amount of pure water separated (unit: relative value), and the horizontal axis represents the circulation time. The circulation time is defined as the time it takes for the mixed liquid to be sufficiently concentrated and the IPA concentration to approach 99 wt %. A zeolite membrane is assumed to be used as the separation membrane for removing pure water from the mixed liquid, and the reference concentration is assumed to be 50 wt %.

[0087] 6, the amount of pure water separated by dehydration of the mixed solution circulating through the dehydration circulation pipe 514 by the separation membrane 516a gradually increases over each circulation unit time of 1000. When the concentration of the IPA solution increases sufficiently from the reference concentration at the end of each circulation unit time, dehydration ceases and the amount of solution becomes approximately constant. Then, when a concentrated mixed solution (IPA solution concentration of 99 wt %) is produced, the control unit 6 adds the unconcentrated mixed solution used after substrate processing via the recovery pipe 512, thereby increasing the amount of pure water in the mixed solution. Therefore, the amount of pure water separated again increases at the start of the next circulation unit time.

[0088] It is desirable to mix the mixed liquid supplied to the recovery tank 502 with the concentrated mixed liquid remaining in the recovery tank 502 by stirring, so that the concentration of the IPA liquid in the mixed liquid in the recovery tank 502 becomes uniform.

[0089] With the above-described configuration, the concentration of the IPA liquid in the mixed liquid dehydrated by the separation membrane 516a can be maintained at or above the reference concentration, thereby making it possible to separate the pure water and the IPA liquid in the mixed liquid while preventing the service life of the separation membrane 516a from being significantly shortened.

[0090] In the above example, the concentration of the IPA liquid in the newly supplied mixed liquid was set to 20 wt %, but the concentration may be lower than that, or a concentration meter may be installed in the recovery pipe 512 to measure the concentration of the IPA liquid in the newly supplied mixed liquid.

[0091] In addition, although the reference concentration of the separation membrane 516a is 50 wt % in the above example, the reference concentration may be changed depending on the type of separation membrane 516a.

[0092] <Regarding Modifications of the Embodiments Described Above> In the embodiments described above, the material, composition, dimensions, shape, relative positional relationship, or implementation conditions of each component may be described, but these are merely examples in all aspects and are not limiting.

[0093] Thus, numerous variations and equivalents not shown are contemplated within the scope of the technology disclosed herein, including, for example, the modification, addition, or omission of at least one component.

[0094] Furthermore, in at least one embodiment described above, when a material name or the like is stated without being specifically specified, unless a contradiction arises, it is assumed that the material in question includes other additives, such as alloys.

[0095] 6 Control unit 502 Recovery tank 504 Purification tank 506 Supply tank 516a Separation membrane 534 First liquid transfer pipe 552 Second liquid transfer pipe 562 Third liquid transfer pipe

Claims

1. A method for concentrating an organic solvent, comprising: a first step of setting the concentration of an organic solvent in a first liquid, which is a mixture of pure water and an organic solvent, to a first concentration higher than a reference concentration, and storing the first liquid in a tank; a second step of setting the concentration of an organic solvent in a second liquid, which is a mixture of pure water and an organic solvent, to a second concentration lower than the reference concentration, and supplying the second liquid to the first liquid stored in the tank to produce a third liquid having a concentration of the organic solvent equal to or higher than the reference concentration; and a third step of concentrating the third liquid using a separation membrane, wherein the second step supplies the second liquid to the first liquid in an amount determined based on the first concentration, the amount of the first liquid stored in the tank, and the second concentration.

2. The organic solvent concentrating method according to claim 1, wherein the first concentration is 99 wt % or more.

3. The organic solvent concentrating method according to claim 1 or 2, wherein the third step is a step of concentrating the third liquid using the separation membrane in a circulation path including the tank.

4. A method for concentrating an organic solvent according to claim 1 or 2, wherein the second step is a step of storing a portion of the third liquid, which has been concentrated to an organic solvent concentration of 99 wt%, in the tank as the first liquid, and discharging the second liquid into the first liquid in an amount sufficient to achieve the reference concentration or higher, to produce the third liquid.

5. The organic solvent concentrating method according to claim 1 or 2, wherein the third step is a step of discharging the pure water separated from the third liquid by the separation membrane.

6. The organic solvent concentrating method according to claim 1 or 2, wherein the third step is a step of discharging the organic solvent separated from the third liquid by the separation membrane.

7. The method for concentrating an organic solvent according to claim 1 or 2, wherein the organic solvent is IPA.

8. A method for concentrating an organic solvent according to claim 1, wherein the first liquid is the mixed liquid that has been recovered from a substrate processing apparatus and then dehydrated by the separation membrane, and the second liquid is recovered from the substrate processing apparatus.

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