Apparatus and method for verification and reuse of process fluids

Abstract

The disclosed embodiments generally relate to an apparatus and method for verification and reuse of process fluids. The apparatus generally includes a tool for performing lithography and a recirculation path connected to the tool. The recirculation path generally includes a collection unit having a first end connected to a first end of the tool, and a probe having a first end connected to a second end of the collection unit for determining one or more properties of the fluid flowing from the tool. The recirculation path of the apparatus generally further includes a purification unit having a first end connected to a third end of the collection unit and a second end connected to the second end of the probe for modifying the properties of the fluid.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to apparatuses and methods for verifying process fluids and reusing process fluids.

Background Art

[0002] During the processing of a substrate, the process fluid comes into contact with the photoresist and is consequently contaminated. The contamination can be particles or photochemical by-products eluted from the substrate and photoresist material, the processing environment, and the components of the processing chamber. Such contamination degrades the electrical properties of the process fluid, such as resistivity. Furthermore, the contamination adversely affects the control of semiconductor structures and the like in the lithography process. As a result, controlling the contamination of the process fluid is an important factor in substrate processing.

[0003] Conventionally, due to the above-mentioned contamination problems, such process fluids have been discarded once used. However, since process fluids are expensive and the supply is limited, single-use is a hurdle in substrate manufacturing. Furthermore, the characteristics / properties of the process fluid may vary depending on the supplier and batch, leading to inconsistent substrate processing.

[0004] There is a need for apparatuses and methods for verifying process fluids and reusing process fluids.

Summary of the Invention

[0005] Embodiments of the present disclosure generally relate to apparatuses and methods for verifying and reusing process fluids.

[0006] In one embodiment, an apparatus is provided. The apparatus includes a tool for performing lithography and a recirculation path connected to the tool. The recirculation path includes a collection unit having a first end connected to a first end of the tool, and a probe having a first end connected to a second end of the collection unit for determining one or more characteristics of the fluid flowing from the tool. The recirculation path of the apparatus further includes a purification unit having a first end connected to a third end of the collection unit and a second end connected to a second end of the probe, the purification unit for changing the characteristics of the fluid.

[0007] In other embodiments, a method is provided. The method includes flowing fluid from a tool to a collection unit disposed along a recirculation path, the recirculation path further including a purification unit fluidly coupled to the collection unit. The method further includes flowing fluid from the collection unit to a probe disposed along the recirculation path, determining a first value of a characteristic of the fluid, comparing the first value of the characteristic to a threshold or threshold range, and changing a flow path of the fluid based on the first value.

[0008] In other embodiments, a non-transitory computer-readable medium storing instructions is provided, the instructions, when executed on a processor, perform steps for fluid verification or fluid recycling. The steps include flowing fluid from a tool to a collection unit disposed along a recirculation path, the recirculation path further including a probe fluidly coupled to the collection unit and a purification unit fluidly coupled to the collection unit. The steps further include flowing fluid from the collection unit to the probe, determining a first resistivity of the fluid, comparing the first resistivity to a threshold or threshold range, and changing a flow path of the fluid based on the first resistivity.

[0009] To better understand the above-described features of the present disclosure, a more detailed description of the present disclosure, briefly summarized above, can be obtained by referring to the embodiments. Some embodiments are shown in the accompanying drawings. However, it should be noted that the accompanying drawings illustrate only exemplary embodiments and should not be considered as limiting the scope of the present disclosure, and other equally valid embodiments may be permitted.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0011] For ease of understanding, the same reference numerals are used to denote the same elements common to each figure, where possible. The components and features of one embodiment are assumed to be beneficially incorporated into other embodiments without further description.

[0012] The inventors have found an apparatus and method for the verification and reuse of process fluids. Briefly, the embodiments described herein utilize a recirculation path through which the process fluid flows. The path includes a probe for monitoring / measuring one or more characteristics of the process fluid to verify the process fluid, and a purification unit or readjustment system for cleaning the process fluid. The embodiments described herein enable control of the electrical characteristics and cleanliness of the process fluid and can be integrated with various tools for substrate processing. The process fluid can be purified to meet the conditions for substrate processing and reused for processing, thereby reducing the costs associated with substrate processing and mitigating the impact of changes in the supply of the process fluid. Further, since the process fluid can vary between suppliers, the apparatus and method described herein can also be used to maintain consistency between the process fluids entering the substrate processing tool.

[0013] FIG. 1 is a schematic diagram of an exemplary apparatus 100 for verifying the characteristics of a process fluid and for the recycling or reuse of the process fluid, according to at least one embodiment. The apparatus 100 enables monitoring of the characteristics of the used process fluid entering and exiting the tools utilized for substrate processing and purification of the used process fluid. The apparatus 100 also enables monitoring of the characteristics of the unused process fluid and purification of the unused process fluid.

[0014] Device 100 generally includes a circulation path 105 for circulating process fluid 101. Components along the recirculation path 105 include a collection unit 103 for collecting used or unused process fluid 101, a probe 109 for determining one or more characteristics of the process fluid 101, and a purification unit 111 for purifying, cleaning, or otherwise removing impurities from the process fluid 101. The process fluid 101 can be used process fluid exiting from a tool 116 for substrate processing. Additionally or alternatively, the process fluid 101 can be unused process fluid. The process fluid, whether used or unused, is connected to the inlet line 102 via line 114. The line 114 and the inlet line 102 can be the same line or different lines.

[0015] The process fluid 101 enters the recirculation path 105 via an inlet line 102 connected to the collection unit 103 and exits the recirculation path 105 via an outlet line 112b. The recirculation path 105 fluidly couples each of the collection unit 103, the probe 109, and the purification unit 111 to the inlet line 102 and the outlet line 112b. Upon exiting the recirculation path 105, the process fluid 101 can flow directly to a tool 115 for substrate processing or can be collected in a reservoir 113 where it can be stored for use in a tool 115 for substrate processing. Additionally or alternatively, although not shown, the process fluid 101 can flow directly from the recirculation path 105 to a tool 116 or can be collected in a reservoir, such as reservoir 113 (and / or a separate reservoir), where it can be stored for use in a tool 116 for substrate processing. In such an embodiment, the outlet line 112b (or a separate outlet line) can be connected to the tool 116 by a valve.

[0016] The collection unit 103 collects the used processing liquid 101 from the substrate processing tool and / or collects the unused process fluid. In some examples, the collection unit 103 includes a replenishment tank that holds or otherwise stores the process fluid 101 and a pump element that draws the process fluid 101 into the collection unit 103 via the inlet line 102. The collection unit 103 is connected to the probe 109 via lines 106a, 106b. A schematic diagram of the probe 109 is shown in FIG. 3. Briefly, the probe 109 makes it possible to determine one or more characteristics of the process fluid 101 regarding whether the process fluid 101 can be used for substrate processing. Based on the above determination, the process fluid can be purified. Accordingly, the embodiments described herein can be utilized for verification of the process fluid and / or detection of the state of the process fluid.

[0017] The collection unit 103 is also connected to the purification unit 111 by lines 104a, 104b. The purification unit 111 includes devices for purifying, cleaning, or otherwise removing impurities from the process fluid 101. Such impurities can include water, metals, organic compounds, and particulates. The devices within the purification unit 111 are capable of performing various methods including guard bed treatment, membrane treatment, carbon bed treatment, cooling, filtration, electrostatic filtration, polishing filtration, scrubbing, purification, chemical cleaning, vacuum distillation, fractional distillation, evaporation, extraction, or combinations thereof. Thus, the purification unit 111 can include, among other suitable devices for purifying, cleaning, or otherwise removing impurities from the process fluid 101, a guard bed, carbon bed, ion exchange resin, membrane, heat exchanger, cooler, filter, scrubber, purifier, chemical, and distillation apparatus for cleaning the fluid. The guard bed, carbon bed, ion exchange resin, membrane, and similar devices can be selected for particle size, molecular weight, and other suitable parameters. In some embodiments, the purification unit 111 includes a polishing filter, carbon bed, molecular sieve, desiccant, and / or distillation apparatus. The polishing filter can be used to remove suspended or fine solids from the process fluid 101. The carbon bed containing activated carbon can be utilized to remove impurities from the process fluid 101. In some examples, the molecular sieve and / or desiccant are used to remove moisture from the process fluid 101. The distillation apparatus can be used to separate the components of the process fluid 101 based on differences in boiling points. The distillation apparatus can be equipped with a vacuum to enable purification of substances that cannot be easily distilled at ambient pressure.

[0018] As shown in FIG. 1, the probe 109 is also connected to the purification unit 111 by lines 108, 110, and 104b, enabling the reuse of the process fluid 101 entering the probe 109. An optional filter unit 107 can be disposed between the collection unit 103 and the probe 109. The optional filter unit 107 can include a device or apparatus for removing species (e.g., contaminants and / or particles) that may impede or block the fluid entering and leaving the probe 109 from the process fluid 101. Additionally or alternatively, the optional filter unit 107 can also include a device for removing species that may impair the function of the probe 109 from the process fluid 101. Additionally or alternatively, the filter unit can be used as a coarse filter for protecting components within the purification unit 111. In some examples, the optional filter unit 107 includes a filter for removing or substantially removing species having a size from about 10 nm to about 100 nm from the process fluid 101.

[0019] During operation, the process fluid 101 exiting the tool or chamber (if used) is flowed to the collection unit 103 by opening the valve 120. A portion of the process fluid 101 is flowed to the probe 109 via lines 106a, 106b, where processes for determining one or more characteristics of the process fluid 101 are performed. The processes performed by the probe 109 and other processes are described below in connection with FIG. 2.

[0020] If one or more characteristics of the process fluid 101 do not meet one or more threshold values of the characteristic, the valve 122 is opened, lines 104a and 104b are connected, and the process fluid 101 flows into the purification unit 111. After purification, the process fluid 101 exiting the purification unit 111 can flow out of the recirculation path 105 via lines 110, 112a, and 112b and into the reservoir 113. Here, the valve 124 is opened to connect lines 110 and 112a. Valves 126 and 122, and valve 128 are also opened to connect lines 112a and 112b, whereby the purified or otherwise suitable process fluid 101 for substrate processing can enter the reservoir 113.

[0021] If one or more characteristics of the process fluid 101 meet one or more threshold values regarding the above characteristics, the valve 122 is opened and line 104a is connected to line 112. Valve 128 is also opened to connect lines 104a and 112b, and the process fluid 101 is supplied to the reservoir 113. Thereafter, the process fluid 101 can be flowed to a tool 115 (or chamber) for use in substrate processing or a tool 116 (or chamber) for use in substrate processing. Exemplary tools 115, 116 include, among others, tools for performing post-exposure bake (PEB) and field enhanced post-exposure bake (FE-PEB). Other tools include tools for performing lithography, cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), and / or other substrate processes. In some aspects, the process fluid 101 that exits tool 116 and flows past one or more components of the recirculation path 105 (e.g., for verification and / or purification) can re-enter the same tool 116 or enter a different tool, such as tool 115.

[0022] A portion of the process fluid 101 flowing through the probe 109 can also be purified. Here, the process fluid 101 exits the probe 109 via line 108. Valve 124 is opened and lines 108 and 112 are connected. Valves 126 and 122 are also opened, whereby the process fluid can flow from line 112a to line 104b. Thereafter, the process fluid 101 can flow to the purification unit 111. The process fluid can flow out of the purification unit 111 and into the reservoir 113 as described above. It is contemplated that one or more of the elements described in FIG. 1 can be connected to a controller (e.g., controller 344 shown in FIG. 3).

[0023] Although not shown in FIG. 1, it should be understood that, for example, there are additional devices for controlling the temperature, pressure, and flow of the process fluid 101, as well as one or more components of the device 100. For example, a heat exchanger can be used to cool or heat the process fluid 101 as it moves along the various lines of the device 100 or within the various units, and pumps and motors can be utilized to control the flow rate of the materials within the device 100. Various process controls such as pressure gauges, differential pressure cells, thermometers, thermocouples, temperature switches, resistance temperature detectors, solenoids, flow meters, flow regulators and valves, humidity sensors, ammeters, flow velocity meters, liquid level detectors, supply level probes, and / or electric drive devices can also be used.

[0024] Figure 2 is a flowchart showing selected high-level steps of method 200 for verifying the characteristics of a process fluid and for recycling or reusing the process fluid. The process fluid, for example process fluid 101, can be a used fluid or an unused fluid obtained from a vendor. The discussion in Figure 2 relates to the resistivity of process fluid 101, but other characteristics such as the concentration of water in the process fluid, the dielectric constant of the process fluid, and the gas content of the process fluid can be determined. Optionally, a particulate measurement system can be added along recirculation path 105 to verify that the process fluid is free or substantially free of contaminants.

[0025] In step 210, one or more characteristics of process fluid 101 used for substrate processing are determined. A voltage is applied to a probe (e.g., probe 300 shown in Figures 3 and 4) configured to flow process fluid 101 therethrough for measurement of the resistivity of the fluid. Probe 300 is a non-limiting example of a probe that can be used in the embodiments described herein, and other probes and variations thereof are contemplated.

[0026] The voltage generates a current that flows from metal bar 332 through process fluid 101 to ground electrode 336. The resistivity of process fluid 101 is calculated based on the current flowing through process fluid 101 within probe 300. For example, a voltage (V) is applied by a voltage source (not shown) to metal bar 332 surrounded by ground electrode 336. A current (I) flows from metal bar 332 through gap 400 to ground electrode 336. The cross-section of gap 400 is substantially toroidal in shape. A voltage from about 50V to about 500V is applied to metal bar 332, for example, a voltage from about 100V to about 450V, for example from about 150V to about 400V, for example from about 200V to about 350V, for example from about 250V to about 300V is applied to metal bar 332. In other embodiments, a voltage from about 75V to about 150V is applied to metal bar 332, for example, a voltage from about 100V to about 125V is applied to metal bar 332. In other embodiments, the voltage is less than about 500V.

[0027] A controller 344, electrically connected to a ground electrode 336 via a contact 340 as shown in FIG. 3, measures a current and calculates a resistance (R). Since the metal bar 332 and the ground electrode 336 are made of known metals, the controller 344 can be programmed to filter out the resistance inherent to the metal used in the metal bar 332 or the ground electrode 336.

[0028] The resistivity of the process fluid 101 (ρ = RA / L) is determined based on the calculated resistance, where R is the calculated resistance, A is the surface area of the ground electrode 336, and L is the distance between the metal bar 332 and the ground electrode 336. In one example, the resistivity (ρ) is proportional to the surface area of the inner surface of the ground electrode 336 (A = 2πr*l1), where r is equal to the inner diameter 408, l1 is equal to the length 416, and L is equal to the length of the gap 400.

[0029] In step 220, a characteristic of the process fluid 101 (e.g., resistivity ρ) is compared with a threshold value of the characteristic (e.g., ρ th ). The threshold value ρ th can be a specific value or range of values determined based on normal operating data of the process fluid. The normal operating data can be reference data collected for normal (or proper) substrate processing. The threshold value ρ th can be a data set stored in a memory device such as the memory 352.

[0030] The threshold value ρth is stored in a memory device such as the memory 352. The threshold value corresponds to the level of particle contamination in the process fluid 101. If the measured resistivity of the process fluid 101 (ρ m ) is determined to be less than the threshold value ρ th (indicating that the process fluid is suitable for substrate processing), the process fluid 101 can be flowed to the reservoir 113. Here, the controller 344 can send a signal indicating that the process fluid can be flowed to the reservoir 113 to an input / output device such as a display unit or an audio device (not shown). The measured resistivity of the process fluid 101 (ρ m) is equal to or greater than the threshold value (ρ m ≧ρ th ), when it is determined, the controller 344 sends an alarm to an input / output device such as a display unit or an audio device (not shown). The alarm indicates that an action is being performed on the process fluid 101.

[0031] An example of the action performed in step 230 may include purifying the process fluid 101. Here, this action may further include opening the valve 122 to allow the process fluid 101 to flow from line 104a to line 104b, thereby supplying the process fluid 101 from the collection unit 103 to the purification unit 111. By means of the device in the purification unit 111, the measured resistivity ρ of the process fluid 101 m becomes smaller than the threshold value ρ th , the concentration of contaminants in the process fluid 101 is reduced. The resistivity of the process fluid 101 can be determined in a new time iteration. The method 200 can be repeated for a predetermined period or a predetermined number of determination cycles. In addition, in some embodiments, at least a portion of the process fluid 101 measured for the second, third, or nth iteration may include a new amount of process fluid from the collection unit 103.

[0032] FIG. 3 is a schematic cross-sectional view of a probe 300 for measuring one or more properties of a process fluid, according to at least one embodiment. As a non-limiting example, probe 300 may be utilized to measure the fluid resistivity of process fluid 101. Probe 300 (e.g., probe 109) includes a measurement section 328 disposed between an upstream coupling 304 coupled to an inlet 301 and a downstream coupling 316 coupled to an outlet 302. In connection with FIG. 1, inlet 301 may be line 106b for supplying process fluid to probe 109, and outlet 302 may be line 108 for the process fluid to exit probe 109. In one example, inlet 301 is disposed along and in line with fluid inlet 334a, and outlet 302 is disposed along and in line with fluid outlet 334b. Each of upstream coupling 304 and downstream coupling 316 is fluidly coupled to inlet 301 and outlet 302.

[0033] Upstream coupling 304 includes an upstream vertical coupling 308 and an upstream horizontal coupling 312. Upstream vertical coupling 308 is directly coupled to inlet 301. Upstream horizontal coupling 312 is physically connected to upstream vertical coupling 308 and is disposed substantially orthogonal to upstream vertical coupling 308. Upstream horizontal coupling 312 is fluidly coupled to inlet 301 and outlet 302. In one example, upstream vertical coupling 308 is press-fit into inlet 301. In another example, upstream vertical coupling 308 is thermally welded to inlet 301.

[0034] The upstream vertical coupling 308 can include a threaded surface and a threaded nut, whereby by inserting and rotating the threaded nut relative to the threaded surface, the inlet 301 fits compressively within the upstream vertical coupling 308. In yet another example, the upstream vertical coupling 308 has a quick connect or push - in fitting that includes a collet, an O - ring surrounding the collet, and a body disposed within the upstream vertical coupling 308. By passing the inlet 301 through the collet and into the body of the upstream vertical coupling 308, it is possible to couple the inlet 301 to the upstream vertical coupling 308 and form a seal. The inlet 301 is disengaged from the upstream vertical coupling 308 by relative movement between the collet, the body, and the inlet 301.

[0035] The downstream coupling 316 has a downstream vertical coupling 320 and a downstream horizontal coupling 324. The downstream vertical coupling 320 is directly coupled to the outlet 302. The downstream horizontal coupling 324 is disposed substantially orthogonally to the downstream vertical coupling 320. The downstream vertical coupling 320 is physically connected to the downstream horizontal coupling 324, and the downstream horizontal coupling 324 is fluidly coupled to the inlet 301 and the outlet 302. Suitable materials for the upstream coupling 304 and the downstream coupling 316 include polymers, plastics, and other non - conductive or non - metallic materials.

[0036] Similar to the previous example regarding the upstream vertical coupling 308, each of the upstream horizontal coupling 312, the downstream vertical coupling 320, and the downstream horizontal coupling 324 can be configured as a threaded surface and a threaded nut. In other examples, the upstream horizontal coupling 312, the downstream vertical coupling 320, and the downstream horizontal coupling 324 can be configured as quick connects or push-in fittings. In yet another example, each of the upstream horizontal coupling 312, the downstream vertical coupling 320, and the downstream horizontal coupling 324 can be thermally welded.

[0037] The measurement system 300 has a measurement section 328 fluidly coupled between the upstream coupling 304 and the downstream coupling 316. The measurement section 328 is physically coupled to the upstream horizontal coupling 312 and the downstream horizontal coupling 324. The process fluid is configured to flow through the inlet 301, pass through the upstream coupling 304, then proceed through the measurement section 328, the downstream coupling 316, and exit through the outlet 302.

[0038] The measurement section 328 includes a metal rod 332 and a ground electrode 336. The metal rod 332 is connected to a voltage source (not shown). The ground electrode 336 surrounds the metal rod 332. Thus, the metal rod 332 and the ground electrode 336 are substantially coaxial. The surface area of the measurement section 328 is defined by the overlap of the surface area of the metal rod 332 and the surface area of the ground electrode 336. Therefore, the length of the measurement section 328 is less than or equal to the length of the ground electrode 336. Although the measurement section 328 is shown substantially linearly, the measurement section 328 is not limited to this shape. As long as the distance between the metal rod 332 and the ground electrode 336 is substantially equal over the entire length of the measurement section 328, a suitable configuration of the measurement section 328 includes bends or U - shaped configurations.

[0039] In one example, the metal rod 332 extends horizontally through the upstream horizontal coupling 312 and through each end of the downstream horizontal coupling 324. In one example, the metal rod 332 has a solid cylindrical structure. Exemplary materials include conductive metals such as aluminum, copper, and iron-containing metals. However, the metal rod 332 is not limited to these materials and can be any conductive metal.

[0040] The ground electrode 336 is a conductive metal. The ground electrode 336 is connected to ground (not shown), and there is a contact 340 on the surface of the ground electrode 336 that is connected to the controller 344. The ground electrode 336 extends horizontally through at least a portion of the upstream horizontal coupling 312 and through at least a portion of the downstream horizontal coupling 324. The ground electrode 336 is a hollow tube that surrounds the metal rod 332. The ground electrode 336 is a conductive metal such as aluminum, copper, or an iron-containing metal.

[0041] A spacer 360 is shown having an outer diameter that is substantially equal to the outer diameter of the ground electrode 336. The inner diameter of the spacer 360 has an inner diameter that is substantially equal to the outer diameter of the metal rod 332. The spacer 360, which is a substantially hollow rod, is used to compress the metal rod 332 within the upstream horizontal coupling 312 and / or within the downstream horizontal coupling 324 as shown. The spacer 360 is made of a non-conductive material such as plastic or polymer. In this way, the ground electrode 336 and the metal rod 332 are compressively fitted to the upstream horizontal coupling 312 and the downstream horizontal coupling 324.

[0042] The controller 344 is electrically connected to a contact 340 on the surface of the ground electrode 336 of the measurement unit 328. A wire 364 electrically connects the controller to the ground electrode 336 via the contact 340. The controller 344 includes a processor 348, a memory 352, and a support circuit 356. The processor 348 can be any form of general-purpose microprocessor, or a general-purpose central processing unit (CPU) that can be used in an industrial environment, such as a programmable logic controller (PLC), a supervisory control and data acquisition (SCADA) system, or other suitable industrial controller.

[0043] The memory 352 is non-transitory and can be one or more of local or remote digital storage in the form of a random access memory (RAM), a read only memory (ROM), or any other form. The memory 352 contains instructions that, when executed by the processor 348, facilitate the operation of the measurement unit 328. The instructions in the memory 352 are in the form of a program product, such as a program for executing the method of the present disclosure. The program code of the program product can conform to any one of several different programming languages. Exemplary computer-readable storage media include, but are not limited to, (i) non-writable storage media where information is permanently stored (e.g., a CD-ROM disk readable by a CD-ROM drive, a flash memory, a ROM chip, or any type of solid-state non-volatile semiconductor memory, i.e., a read-only memory device in a computer), and (ii) writable storage media where changeable information is stored (e.g., a floppy disk in a disk drive or a hard disk drive, or any type of solid-state random access semiconductor memory). Such a computer-readable storage media becomes an embodiment of the present disclosure when carrying computer-readable instructions that direct the functions of the methods described herein. In one example, the present disclosure can be implemented as a program product stored on a computer-readable storage media (e.g., the memory 352) used in a computer system (not shown). The program of the program product defines the functions of the present disclosure described herein.

[0044] FIG. 4 is an isometric cross-sectional view of the measurement portion 328 of the probe 300 cut along A-A of FIG. 3. The gap 400 is defined by the space between the metal bar 332 and the ground electrode 336. The cross-sectional area of the gap 400 is substantially toroidal in shape. The metal bar 332 has an outer diameter 404, and the metal bar 332 is at least as long as the length 416. As described above, the total length of the metal bar 332 may be greater than the length 416. The ground electrode 336 has an inner diameter 408 and a thickness 412. The gap 400 is the space between the outer diameter 404 of the metal bar 332 (i.e., the outer surface of the metal bar 332) and the inner diameter 408 of the ground electrode 336 (i.e., the inner surface of the ground electrode 336). The ground electrode 336 is as long as the length 416. While the resistivity of the fluid is being measured by the measurement portion 328, the process fluid flows through the gap 400. While the resistivity is being determined, the inner surface of the ground electrode 336 and the outer surface of the metal bar 332 are each in fluid contact with the process fluid 101.

[0045] In some embodiments, one or more operations of the apparatus 100 and / or one or more steps of the method 200 described herein can be performed using a programmable logic controller (PLC) and / or, as instructions, can be included in a computer-readable medium for execution by a control unit (e.g., one or more processors) or any other processing system. The computer-readable medium can include any suitable memory for storing instructions, such as, for example, read-only memory (ROM), random access memory (RAM), flash memory, EEPROM (electrically erasable programmable ROM), compact disc ROM (CD-ROM), floppy disk, punch card, magnetic tape, and the like.

[0046] Embodiments described herein generally relate to an apparatus and method for verifying a process fluid. By the embodiments described herein, for example, reuse of the process fluid and determination of whether unused process fluid is suitable for substrate processing can be achieved. By the embodiments described herein, lower manufacturing costs and higher consistency between substrates can be achieved as compared with conventional apparatuses and methods.

[0047] In the foregoing description, embodiments of the present disclosure have been referred to. However, it should be understood that the present disclosure is not limited to the particular described embodiments. Instead, any combination of the following features and elements, whether or not related to various embodiments, is contemplated for implementing and practicing the present disclosure. Further, embodiments of the present disclosure can realize advantages over other possible solutions and / or the prior art, but whether a particular advantage is realized by a given embodiment is not limiting of the present disclosure. Accordingly, the foregoing aspects, features, embodiments, and advantages are illustrative only and are not to be regarded as elements or limitations of the appended claims unless expressly set forth therein. Similarly, references to "the present disclosure" should not be construed as a generalization of the inventive subject matter disclosed herein and are not to be regarded as elements or limitations of the appended claims unless expressly set forth therein. As used herein, the indefinite articles "a" or "an" shall mean "at least one" unless specifically stated to the contrary or the context clearly indicates otherwise.

[0048] Although the foregoing description has been directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope thereof, and the scope of the present disclosure is defined by the following claims.

Claims

1. An apparatus comprising: a tool for performing lithography; a recirculation path connected to the tool; a processor; wherein the recirculation path comprises: a collection unit having a first end connected to a first end of the tool; a probe having a first end connected to a second end of the collection unit, the probe for determining one or more characteristics of a fluid flowing from the tool; a purification unit having a first end connected to a third end of the collection unit and a second end connected to a second end of the probe, the purification unit for changing the characteristics of the fluid; and wherein the processor is configured to: control the flow of the fluid from the collection unit to the probe; determine a first resistivity of the fluid; compare the first resistivity of the fluid with a threshold value or a threshold range; and when the first resistivity is equal to or greater than the threshold value or the threshold range, the processor is further configured to: determine a second resistivity of the fluid; compare the second resistivity of the fluid with the threshold value or the threshold range; when the second resistivity is equal to or greater than the threshold value or the threshold range, cause the fluid to flow from the collection unit to the purification unit; when the second resistivity is less than the threshold value or the threshold range, cause the fluid to flow from the collection unit to a reservoir connected to the recirculation path. An apparatus.

2. The apparatus of claim 1, wherein the one or more characteristics include resistivity.

3. The apparatus of claim 1, wherein when the first resistivity of the fluid is less than the threshold value or the threshold range, the processor is further configured to cause the fluid to flow from the collection unit to a reservoir connected to a second end of the tool.

4. The apparatus of claim 1, wherein when the first resistivity is equal to or greater than the threshold value or the threshold range, the processor is further configured to cause the fluid to flow from the collection unit to the purification unit.

5. ​ The apparatus according to claim 1, wherein the purification unit includes a polishing filter coupled to a filter including activated carbon, an ion exchange resin, a molecular sieve, or a membrane.

6. The apparatus according to claim 5, wherein the purification unit further includes a vacuum distillation column coupled to the filter.

7. A method comprising: flowing fluid from a tool to a collection unit disposed along a recirculation path, the recirculation path further including a purification unit fluidly coupled to the collection unit; flowing the fluid from the collection unit to a probe disposed along the recirculation path; determining a first value of the resistivity of the fluid; comparing the first value of the resistivity with a threshold value or a threshold range; changing a flow path of the fluid based on the first value; when the first value of the resistivity is equal to or greater than the threshold value or the threshold range, flowing the fluid to the purification unit; determining a second value of the resistivity of the fluid; comparing the second value of the resistivity of the fluid with the threshold value or the threshold range; when the second value of the resistivity is equal to or greater than the threshold value or the threshold range, flowing the fluid to the purification unit; when the second value of the resistivity is less than the threshold value or the threshold range, flowing the fluid to a reservoir connected to the recirculation path; A method comprising the steps above.

8. The method according to claim 7, further comprising flowing the fluid to the reservoir connected to the recirculation path when the first value of the resistivity is below the threshold value or the threshold range.

9. The method according to claim 7, wherein the reservoir is further connected to the tool.

10. The method according to claim 7, wherein the tool is configured to perform lithography.

11. Determining the first value of the resistivity comprises: applying a voltage to the probe having a space through which the fluid flows; measuring a current flowing through the fluid; calculating the first value of the resistivity of the fluid based on the voltage and the current. The method according to claim 7, comprising the steps above. **Claim 12**: The method according to claim 7, wherein the purification unit comprises a polishing filter coupled to a filter comprising activated carbon, an ion exchange resin, a molecular sieve, or a membrane. **Claim 13**: The method according to claim 12, wherein the purification unit further comprises a vacuum distillation column coupled to the filter. **Claim 14** A non-transitory computer-readable medium storing instructions that, when executed on a processor, perform steps for validating a fluid or recycling the fluid, the steps comprising: Flowing the fluid from a tool to a collection unit disposed along a recirculation path, the recirculation path further comprising a probe fluidly coupled to the collection unit and a purification unit fluidly coupled to the collection unit; Flowing the fluid from the collection unit to the probe; Determining a first resistivity of the fluid; Comparing the first resistivity to a threshold or a threshold range; Changing a flow path of the fluid based on the first resistivity; Flowing the fluid to the probe; Determining a second resistivity of the fluid; Comparing the second resistivity of the fluid to the threshold or the threshold range; Flowing the fluid to the purification unit when the second resistivity is equal to or greater than the threshold or the threshold range; Flowing the fluid to a reservoir coupled to the tool when the second resistivity is less than the threshold or the threshold range; A non-transitory computer-readable medium comprising the above. **Claim 15** The steps further comprise: Flowing the fluid to the purification unit when the first resistivity is equal to or greater than the threshold or the threshold range; Flowing the fluid to a reservoir coupled to the recirculation path when the first resistivity is below the threshold or the threshold range; or Combinations thereof The non-transitory computer-readable medium according to claim 14, further comprising the above. **Claim 16** The non-transitory computer-readable medium according to claim 15, wherein the reservoir is further coupled to the tool. **Claim 17**: The non-transitory computer-readable medium according to claim 14, wherein the tool is configured to perform lithography. The non-transitory computer-readable medium according to claim 14, wherein the purification unit includes a polishing filter coupled to a filter including activated carbon, an ion exchange resin, a molecular sieve, or a membrane. The non-transitory computer-readable medium according to claim 18, wherein the purification unit further includes a vacuum distillation column coupled to the filter.

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