Substrate processing apparatus and substrate processing method

Abstract

To provide a technique capable of more appropriately discharging hydrogen gas.SOLUTION: A substrate processing apparatus includes a processing unit 1, a tank Tk1, a circulation unit 3, a liquid discharge unit 4, a gas supply unit 5, an exhaust unit 6, and a control unit. The circulation unit 3 includes a circulation pipe 31 connected to the tank Tk1 and an electrolysis cell 32 that generates electrolytic sulfuric acid by electrolysis. The liquid discharge unit 4 discharges the processing liquid to the outside. The gas supply unit 5 supplies the first gas to the tank Tk1. The exhaust unit 6 exhausts the gas in the tank Tk1 to the outside. The control unit controls the circulation unit 3, the gas supply unit 5, and the exhaust unit 6 to adjust the pressure in the tank Tk1 to a negative pressure during electrolysis of the processing liquid.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a substrate processing apparatus and a substrate processing method. [Background technology]

[0002] Conventionally, cleaning systems have been proposed that electrolyze sulfuric acid to generate persulfuric acid, and then use the persulfuric acid to remove resist from substrates (see, for example, Patent Document 1). In Patent Document 1, the cleaning system includes an electrolysis device, a first circulation line, and an electrolyte storage tank. The electrolysis device is connected to the electrolyte storage tank through the first circulation line. A sulfuric acid solution circulates through the first circulation line, and the electrolysis device electrolyzes the sulfuric acid solution to generate persulfuric acid. Hydrogen gas is also generated during this electrolysis. The electrolyte containing persulfuric acid and the hydrogen gas are separated from each other in a gas-liquid separation tank provided in the first circulation line, and the hydrogen gas is discharged to the outside. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 155336 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology of Patent Document 1, there is a risk that a portion of the hydrogen gas may remain in the circulation path.

[0005] Therefore, an object of the present disclosure is to provide a technology that can more appropriately discharge hydrogen gas. [Means for solving the problem]

[0006] A first aspect is a substrate processing apparatus comprising: a processing unit for processing substrates using a processing liquid; a tank for storing the processing liquid containing sulfuric acid; a circulation piping connected to the tank; and a circulation section including an electrolytic cell inserted in the circulation piping for generating electrolytic sulfuric acid by electrolysis; a drainage section including a drain pipe connected to the tank or the circulation piping and discharging the processing liquid to the outside through the drainage pipe; a gas supply section including a first air supply pipe connected to the tank and supplying a first gas to the tank through the first air supply pipe; an exhaust section including an exhaust pipe connected to the tank and discharging gas in the tank to the outside through the exhaust pipe; and a control section that controls the circulation section, the gas supply section, and the exhaust section to adjust the pressure in the tank to negative pressure during electrolysis of the processing liquid.

[0007] A second aspect is a substrate processing apparatus according to the first aspect, wherein the control unit controls the drainage unit, the gas supply unit, and the exhaust unit to adjust the pressure in the tank to a positive pressure while the processing liquid is being discharged.

[0008] A third aspect is a substrate processing apparatus according to the first or second aspect, wherein the control unit controls the flow rate of the first gas during electrolytic decomposition of the processing liquid to be greater than the flow rate of the first gas during discharge of the processing liquid.

[0009] A fourth aspect is a substrate processing apparatus according to any one of the first to third aspects, wherein the gas supply unit includes a second air supply pipe having a downstream end connected to a connection position midway through the exhaust pipe, and supplies a second gas having a lower degree of purity than the first gas to the exhaust pipe through the second air supply pipe.

[0010] A fifth aspect is the substrate processing apparatus according to the fourth aspect, wherein the first gas is nitrogen gas and the second gas is air.

[0011] A sixth aspect is a substrate processing apparatus according to the fourth or fifth aspect, wherein the exhaust section includes a capture section provided in the exhaust pipe that captures a target to be captured in the gas flowing through the exhaust pipe, and the downstream end of the second air supply pipe is connected to the exhaust pipe at the connection position downstream of the capture section.

[0012] A seventh aspect is a substrate processing apparatus according to any one of the fourth to sixth aspects, comprising: a first hydrogen sensor provided in a portion of the tank and the exhaust pipe upstream of the connection position, the first hydrogen sensor measuring the hydrogen concentration of the gas; and a first flow rate adjustment unit provided in the first air supply pipe, adjusting the flow rate of the first gas, wherein the control unit controls the first flow rate adjustment unit based on the hydrogen concentration measured by the first hydrogen sensor.

[0013] An eighth aspect is a substrate processing apparatus according to the seventh aspect, wherein the exhaust section includes a capture section provided in the exhaust pipe for capturing a capture target in the gas flowing through the exhaust pipe, the downstream end of the second air supply pipe is connected to the exhaust pipe at the connection position downstream of the capture section, and the first hydrogen sensor is provided in a portion of the exhaust pipe between the connection position and the capture section.

[0014] A ninth aspect is a substrate processing apparatus according to any one of the fourth to eighth aspects, comprising a second hydrogen sensor provided in the exhaust pipe downstream of the connection position to measure the hydrogen concentration of the gas, and a second flow rate adjustment unit provided in the second air supply pipe to adjust the flow rate of the second gas, and the control unit controls the second flow rate adjustment unit based on the hydrogen concentration measured by the second hydrogen sensor.

[0015] A tenth aspect is the substrate processing apparatus according to any one of the second to ninth aspects, wherein the pressure in the circulation pipe is positive while the processing liquid is being discharged.

[0016] An eleventh aspect is a substrate processing method, comprising an electrolysis circulation step in which, while adjusting the pressure in a tank that stores a processing liquid used to process a substrate to a negative pressure, the processing liquid is circulated through a circulation pipe connected to the tank, and an electrolytic cell provided in the circulation pipe electrolyzes sulfuric acid in the processing liquid to generate electrolyzed sulfuric acid.

[0017] A twelfth aspect is a substrate processing method according to the eleventh aspect, further comprising a draining step of discharging the processing liquid through a drain pipe connected to the tank or the circulation piping while adjusting the pressure inside the tank to a positive pressure. [Effects of the Invention]

[0018] According to the first and eleventh aspects, the pressure inside the tank is negative during electrolysis of the treatment liquid. Therefore, hydrogen gas generated by electrolysis is drawn into the tank. This reduces the possibility of hydrogen gas accumulating in the electrolysis cell and the circulation piping. In other words, the exhaust unit can appropriately exhaust hydrogen gas to the outside.

[0019] According to the second, tenth, and twelfth aspects, the pressure inside the tank is positive while the processing liquid is being discharged. This reduces the possibility that external gases will enter the tank or the circulation piping through the drain pipe. This prevents contamination of the tank or the circulation piping by external gases.

[0020] According to the third aspect, the flow rate of the first gas is large during electrolysis. Therefore, the hydrogen concentration of the exhaust gas can be appropriately reduced during electrolysis. On the other hand, the flow rate of the first gas is small during discharge of the treatment liquid. Therefore, the amount of the first gas used can be reduced during discharge of the treatment liquid.

[0021] According to the fourth aspect, the gas supply unit supplies a first gas with high purity to the tank. This reduces the possibility of contamination of the treatment liquid. On the other hand, the gas supply unit supplies a second gas with low purity to the exhaust pipe. Since the second gas hardly flows into the circulation path, contamination of the treatment liquid by the second gas hardly occurs. Furthermore, the second gas with low purity is cheaper than the first gas with high purity. This makes it possible to more inexpensively reduce the hydrogen concentration of the exhaust gas flowing through the exhaust pipe.

[0022] According to the fifth aspect, nitrogen gas, which has a proven track record of being used in substrate processing, is used as the first gas, thereby more reliably reducing contamination of the processing liquid. Since air is very inexpensive, running costs can be further reduced.

[0023] According to the sixth aspect, the second gas does not pass through the capture part, and therefore the pressure loss occurring in the second gas can be reduced.

[0024] According to the seventh aspect, the hydrogen concentration of the gas in the tank can be controlled with higher precision.

[0025] According to the eighth aspect, the first hydrogen sensor can measure the hydrogen concentration with higher accuracy.

[0026] According to the ninth aspect, the hydrogen concentration of the gas in the exhaust pipe after joining with the second gas can be controlled with higher precision. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a plan view schematically showing an example of the configuration of a substrate processing apparatus. [Figure 2] FIG. 2 is a block diagram illustrating an example of the internal configuration of the control unit. [Figure 3] FIG. 3 is a side view schematically showing an example of the configuration of a part of the processing block and an electrolytic sulfuric acid supply unit according to the first embodiment. [Figure 4]FIG. 4 is a flowchart showing an example of the electrolytic sulfuric acid generating operation in the electrolytic sulfuric acid supply unit. [Figure 5] FIG. 5 is a flowchart showing an example of the treatment solution discharge operation in the electrolytic sulfuric acid supply unit. [Figure 6] FIG. 6 is a diagram showing an example of the change over time in the flow rate of the first dilution gas (dilution flow rate), the change over time in the flow rate of the exhaust gas (exhaust flow rate), and the change over time in the pressure inside the tank. [Figure 7] FIG. 7 is a diagram schematically illustrating an example of a more specific configuration of the electrolytic sulfuric acid supply unit. [Figure 8] FIG. 8 is a flowchart showing an example of the operation of the electrolytic sulfuric acid supply unit. [Figure 9] FIG. 9 is a diagram schematically illustrating an example of the electrolytic sulfuric acid supply unit. [Figure 10] FIG. 10 is a diagram schematically illustrating an example of the electrolytic sulfuric acid supply unit. [Figure 11] FIG. 11 is a diagram schematically illustrating an example of the electrolytic sulfuric acid supply unit. [Figure 12] FIG. 12 is a diagram schematically illustrating an example of the electrolytic sulfuric acid supply unit. [Figure 13] FIG. 13 is a diagram schematically illustrating an example of the configuration of the electrolytic sulfuric acid supply unit according to the second embodiment. [Figure 14] FIG. 14 is a flowchart showing an example of the operation of the electrolytic sulfuric acid supply unit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, the embodiments will be described in detail with reference to the drawings. Note that in the drawings, the dimensions and numbers of each part are exaggerated or simplified as necessary for ease of understanding. Parts having similar configurations and functions are assigned the same reference numerals, and duplicate explanations will be omitted below.

[0029] 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.

[0030] Furthermore, in the following description, even if ordinal numbers such as "first" or "second" are used, these terms are used for convenience to facilitate understanding of the contents of the embodiments, and are not limited to the order that may result from these ordinal numbers.

[0031] When expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) are used, unless otherwise specified, the expressions not only strictly represent the positional relationship but also represent a state in which there is a relative displacement in terms of angle or distance within a range in which tolerance or equivalent functionality is obtained. When expressions indicating an equal state (e.g., "identical," "equal," "homogeneous," etc.) are used, the expressions not only represent a state in which there is strict quantitative equality but also represent a state in which there is a difference in which tolerance or equivalent functionality is obtained, unless otherwise specified. When expressions indicating a shape (e.g., "rectangular shape" or "cylindrical shape," etc.) are used, the expressions not only represent a geometrically strict shape but also represent a shape with, for example, irregularities or chamfers within a range in which equivalent effects are obtained, unless otherwise specified. When the expressions "comprise," "include," "have," "includes," "includes," or "have" are used to describe one component, the expressions are not exclusive expressions that exclude the presence of other components. When the phrase "at least one of A, B, and C" is used, the phrase includes A only, B only, C only, any two of A, B, and C, and all of A, B, and C.

[0032] First Embodiment <Substrate processing equipment> 1 is a plan view schematically showing an example of the configuration of a substrate processing apparatus 100. The substrate processing apparatus 100 is a single-wafer processing apparatus that processes substrates W one by one.

[0033] The substrate W is, for example, a semiconductor wafer, a liquid crystal display substrate, an organic EL (Electroluminescence) substrate, an FPD (Flat Panel Display) substrate, an optical display substrate, a magnetic disk substrate, an optical disk substrate, a magneto-optical disk substrate, a photomask substrate, or a solar cell substrate. The substrate W has a thin, flat plate shape. In the following, the substrate W is assumed to be a semiconductor wafer. The substrate W has, for example, a disk shape. The diameter of the substrate W is, for example, about 300 mm, and the thickness of the substrate W is, for example, not less than about 0.5 mm and not more than about 3 mm.

[0034] 1, the substrate processing apparatus 100 includes an indexer block 110, a processing block 120, and a control unit 90. The processing block 120 is a section that mainly processes substrates W, and the indexer block 110 is a section that mainly transports substrates W between the outside of the substrate processing apparatus 100 and the processing block 120.

[0035] The indexer block 110 includes a load port 111 and a first transport part 112. A substrate container (hereinafter referred to as a carrier) C that has been carried in from outside is placed on the load port 111. The carrier C accommodates a plurality of substrates W, for example, arranged at intervals in the vertical direction. In the example of FIG. 1, a plurality of load ports 111 are arranged.

[0036] The first transport unit 112 is a transport robot and can remove an unprocessed substrate W from a carrier C placed on each load port 111. The first transport unit 112 may also be called an indexer robot. The first transport unit 112 transports the unprocessed substrate W removed from the carrier C to the processing block 120. The processing block 120 can process the unprocessed substrate W. The first transport unit 112 can also receive a processed substrate W from the processing block 120 and transport the processed substrate W to a carrier C in the load port 111.

[0037] In the example of FIG. 1, the processing block 120 includes a plurality of processing units 1 and a second transport part 122. The second transport part 122 is a transport robot and can transport substrates W between the first transport part 112 and the plurality of processing units 1. In the example of FIG. 1, the processing block 120 also includes a mounting part 123. The mounting part 123 is, for example, a shelf on which a plurality of substrates W can be placed in a vertically aligned state. The first transport part 112 mounts an unprocessed substrate W on the mounting part 123. The second transport part 122 removes the unprocessed substrate W from the mounting part 123 and transports the substrate W to the processing unit 1. The processing unit 1 processes the substrate W. The configuration of the processing unit 1 will be described later. The second transport part 122 removes the processed substrate W from the processing unit 1 and transports the substrate W to the mounting part 123. The first transport part 112 takes out the substrate W from the platform 123 and transports the substrate W to the carrier C of the load port 111 .

[0038] 1, a plurality of (for example, four) processing units 1 are arranged to surround the second transport section 122 in a plan view. This second transport section 122 may also be called a center robot. At each position in a plan view, a plurality of processing units 1 may be stacked vertically. In other words, a plurality of (four in the figure) towers TW each made up of a plurality of processing units 1 stacked vertically may be arranged to surround the second transport section 122.

[0039] The processing unit 1 supplies various processing liquids to the substrate W to perform various processes on the substrate W. One of the processing liquids contains electrolytic sulfuric acid. Electrolytic sulfuric acid is persulfuric acid (peroxodisulfuric acid (H2S2O8)) produced by electrolyzing sulfuric acid. Persulfuric acid has a stronger oxidizing power than Caro's acid (H2SO5) at the same temperature. Hereinafter, a liquid containing electrolytic sulfuric acid will be referred to as an electrolytic sulfuric acid liquid. When this electrolytic sulfuric acid liquid is supplied to the substrate W, it acts on organic matter on the surface of the substrate W, oxidizing and removing the organic matter. The organic matter may be, for example, a resist film.

[0040] As shown in Fig. 1, the substrate processing apparatus 100 further includes an electrolytic sulfuric acid supply unit 2. The electrolytic sulfuric acid supply unit 2 supplies electrolytic sulfuric acid solution to the processing unit 1. In the example of Fig. 1, the electrolytic sulfuric acid supply unit 2 is adjacent to the processing unit 1 in a plan view, but in reality, the electrolytic sulfuric acid supply unit 2 may be provided on a lower level (e.g., a lower floor) than the processing unit 1. The electrolytic sulfuric acid solution supplied to the substrate W in the processing unit 1 may be recovered in the electrolytic sulfuric acid supply unit 2 after processing of the substrate W.

[0041] The control unit 90 comprehensively controls the substrate processing apparatus 100. Specifically, the control unit 90 controls the first transfer unit 112, the second transfer unit 122, the processing unit 1, and the electrolytic sulfuric acid supply unit 2. FIG. 2 is a block diagram schematically illustrating an example of the internal configuration of the control unit 90. The control unit 90 is an electronic circuit and includes, for example, a data processing unit 91 and a memory unit 92. In the specific example of FIG. 2, the data processing unit 91 and the memory unit 92 are connected to each other via a bus 93. The data processing unit 91 may be, for example, an arithmetic processing device such as a CPU (Central Processor Unit). The memory unit 92 may include a non-transitory memory unit (e.g., a ROM (Read Only Memory)) 921 and a temporary memory unit (e.g., a RAM (Random Access Memory)) 922. The non-transitory memory unit 921 may store, for example, a program that defines the processing to be performed by the control unit 90. The data processing unit 91 executes the program, allowing the control unit 90 to perform the processing defined in the program. Of course, some or all of the processing performed by the control unit 90 may be performed by hardware such as a dedicated logic circuit.

[0042] As described above, the control unit 90 includes one or more processors. The processor includes, for example, one or more circuits or units configured to perform calculations or processes by executing instructions stored in a memory. The processor includes, for example, at least one of a central processor unit (CPU), an application-specific integrated circuit (ASCI), a field-programmable gate array (FPGA), a digital signal processor (DSP), a digital flow processor (DFP), a microcontroller unit (MCU), a graphics processing unit (GPU), and a neural processing unit (NPU). The control unit 90 may also be realized by multiple computers or processors working together, in which case the multiple computers or processors may be located remotely from one another.

[0043] 3 is a side view schematically showing an example of the configuration of a part of the processing block 120 according to the first embodiment and the electrolytic sulfuric acid supply unit 2. In the example of FIG. 3, one tower TW and the electrolytic sulfuric acid supply unit 2 are shown.

[0044] <Processing Unit 1> In the example of Figure 3, the tower TW is composed of three processing units 1. The number of processing units 1 constituting the tower TW can be changed as appropriate. The internal configurations of the processing units 1 may be the same. In the example of Figure 3, the processing unit 1 includes a chamber 11, a substrate holder 12, a discharge unit 13, and a guard 14. The chamber 11 has a box-like shape. The internal space of the chamber 11 corresponds to the processing space in which the substrate W is processed. A loading / unloading port and a shutter (not shown) are provided on the side wall of the chamber 11. The second transport unit 122 loads and unloads the substrate W into and out of the processing unit 1 through the loading / unloading port with the shutter open.

[0045] The substrate holder 12 is provided in the chamber 11 and holds the substrate W in a horizontal position. Here, the horizontal position means that the thickness direction of the substrate W is aligned with the vertical direction. The substrate holder 12 may rotate the substrate W around a rotation axis Q1. The rotation axis Q1 is an axis that passes through the center of the substrate W and is aligned with the vertical direction. The substrate holder 12 is also called a spin chuck. The substrate holder 12 may be a clamping type spin chuck or a suction type spin chuck. The substrate holder 12 is controlled by a control unit 90.

[0046] The discharge unit 13 discharges the electrolytic sulfuric acid solution onto a main surface (e.g., an upper surface) of the substrate W held by the substrate holding unit 12. In the example of FIG. 3, the discharge unit 13 includes a nozzle 131, a liquid supply pipe 132, and a supply valve 133. In the example of FIG. 2, the nozzle 131 is provided in the chamber 11 above the substrate W held by the substrate holding unit 12. The downstream end of the liquid supply pipe 132 is connected to the nozzle 131. The electrolytic sulfuric acid solution is supplied to the liquid supply pipe 132 from the electrolytic sulfuric acid supply unit 2. The supply valve 133 is inserted in the liquid supply pipe 132. The supply valve 133 is controlled by the control unit 90 to switch the liquid supply pipe 132 on or off.

[0047] The control unit 90 opens the supply valve 133 while the substrate W is rotating. This causes the electrolytic sulfuric acid solution to be discharged from the discharge port of the nozzle 131 toward the main surface of the rotating substrate W. The electrolytic sulfuric acid solution lands on the main surface of the substrate W. The electrolytic sulfuric acid solution flows radially outward on the main surface of the substrate W due to centrifugal force caused by the rotation of the substrate W, and is scattered outward from the periphery of the substrate W. The electrolytic sulfuric acid solution acts on the main surface of the substrate W, thereby oxidizing and removing organic matter present on the main surface of the substrate W. When the control unit 90 closes the supply valve 133, the discharge of the electrolytic sulfuric acid solution from the nozzle 131 ends.

[0048] The guard 14 has a cylindrical shape and is provided in the chamber 11 so as to surround the substrate holder 12. The guard 14 receives the electrolytic sulfuric acid solution that has splashed from the periphery of the substrate W. The electrolytic sulfuric acid solution flows down along the inner peripheral surface of the guard 14.

[0049] The discharge unit 13 may be provided to be able to supply various processing liquids. For example, the discharge unit 13 may be provided to be able to supply a rinse liquid such as pure water to the substrate W. When the discharge unit 13 supplies the rinse liquid to the main surface of the substrate W, the rinse liquid can wash away the electrolytic sulfuric acid liquid on the main surface of the substrate W.

[0050] <Electrolytic sulfuric acid supply section 2> Next, an example of the configuration of the electrolytic sulfuric acid supply unit 2 will be outlined, followed by an example of the operation of the electrolytic sulfuric acid supply unit 2. A more detailed example of the configuration of the electrolytic sulfuric acid supply unit 2 and a more detailed example of the operation of the electrolytic sulfuric acid supply unit 2 will be described later.

[0051] As shown in FIG. 3, the electrolytic sulfuric acid supply unit 2 includes a tank Tk1, a circulation unit 3, a liquid drainage unit 4, a gas supply unit 5, and an exhaust unit 6.

[0052] The tank Tk1 stores a treatment liquid containing sulfuric acid. The treatment liquid contains sulfuric acid and water. The tank Tk1 is, for example, a sealed tank.

[0053] The circulation unit 3 includes a circulation pipe 31 and an electrolytic cell 32. The circulation pipe 31 is connected to a tank Tk1. As an example, the upstream end of the circulation pipe 31 is connected to the bottom of the tank Tk1, and the downstream end of the circulation pipe 31 is connected to the ceiling of the tank Tk1. The circulation unit 3 circulates the treatment liquid through an electrolytic circulation path including the tank Tk1 and the circulation pipe 31. In the example of FIG. 3, the circulation unit 3 also includes a circulation valve 33 and a liquid delivery unit 34. The liquid delivery unit 34 is inserted into the circulation pipe 31. The liquid delivery unit 34 is controlled by a control unit 90 and delivers the treatment liquid from the upstream end to the downstream end of the circulation pipe 31. The liquid delivery unit 34 is, for example, a pump. The circulation valve 33 is inserted into the circulation pipe 31. The circulation valve 33 is controlled by the control unit 90 and switches the circulation pipe 31 between open and closed states. In the example of FIG. 3, the circulation valve 33 is inserted into the circulation pipe 31 downstream of the liquid delivery unit 34.

[0054] The electrolytic cell 32 is inserted into the circulation pipe 31. In the example of FIG. 3 , the electrolytic cell 32 is inserted into the circulation pipe 31 downstream of the liquid delivery section 34, more specifically, downstream of the circulation valve 33. A treatment liquid containing sulfuric acid flows into the electrolytic cell 32. The electrolytic cell 32 has an internal flow path, and the treatment liquid passes through the internal flow path of the electrolytic cell 32. The electrolytic cell 32 may be installed with the internal flow path extending vertically. In this case, the treatment liquid passes through the electrolytic cell 32 vertically. The electrolytic cell 32 includes a positive electrode and a negative electrode that apply a voltage to the treatment liquid passing through the internal flow path. The positive electrode and the negative electrode are connected to a DC power supply (not shown).

[0055] When the control unit 90 operates the solution delivery unit 34 while opening the circulation valve 33, the treatment solution in the tank Tk1 circulates through the electrolysis circulation path. Therefore, the treatment solution continues to pass through the electrolytic cell 32. When the control unit 90 operates the electrolytic cell 32, in other words, when it causes the DC power supply to output a DC voltage, the electrolytic cell 32 applies the DC voltage to the treatment solution. As a result, sulfuric acid is electrolyzed in the internal flow path of the electrolytic cell 32, and electrolyzed sulfuric acid is generated. In other words, an electrolyzed sulfuric acid solution is generated. The circulation unit 3 can also be said to be an electrolyzed sulfuric acid generation unit that generates electrolyzed sulfuric acid.

[0056] In the example of FIG. 3, the electrolytic sulfuric acid supply unit 2 further includes an external circulation pipe 21. The external circulation pipe 21 includes a portion of the circulation pipe 31, an outward pipe 211, and a return pipe 212. The upstream end of the outward pipe 211 is connected to the circulation pipe 31 between the liquid delivery unit 34 and the circulation valve 33. The portion between the upstream end of the circulation pipe 31 and the upstream end of the outward pipe 211 functions as part of the external circulation pipe 21. A portion of the outward pipe 211 extends vertically while being adjacent to the tower TW (plurality of processing units 1) in the horizontal direction. The downstream end of the outward pipe 211 is connected to the upstream end of the return pipe 212, and the downstream end of the return pipe 212 is connected to, for example, the ceiling of the tank Tk1. A portion of the return pipe 212 also extends vertically while being adjacent to the tower TW in the horizontal direction.

[0057] An external circulation valve 22 is inserted in the external circulation piping 21 (specifically, the outbound piping 211). The external circulation valve 22 is controlled by the control unit 90, and switches between opening and closing the external circulation piping 21. When the control unit 90 operates the liquid delivery unit 34 while opening the external circulation valve 22, the treatment liquid (electrolytic sulfuric acid solution) in the tank Tk1 circulates through an external circulation path including the tank Tk1 and the external circulation piping 21.

[0058] The upstream end of the liquid supply pipe 132 of each processing unit 1 is connected to the external circulation pipe 21. When the control unit 90 opens the supply valve 133, a portion of the electrolytic sulfuric acid solution circulating through the external circulation path is supplied to the substrate W through the liquid supply pipe 132 and the nozzle 131.

[0059] As described above, the electrolytic sulfuric acid supply section 2 electrolyzes sulfuric acid by circulation through the circulation section 3 to generate an electrolytic sulfuric acid solution, and supplies the electrolytic sulfuric acid solution to the treatment unit 1.

[0060] Meanwhile, hydrogen gas is also generated as a by-product of electrolysis. For example, water in the treatment solution is electrolyzed in the internal flow path of the electrolytic cell 32 to generate hydrogen gas. The hydrogen gas flows into the tank Tk1 together with the electrolytic sulfuric acid solution. The electrolytic sulfuric acid solution flows downward to the bottom of the tank Tk1, while the hydrogen gas flows above the electrolytic sulfuric acid solution within the tank Tk1. For this reason, the tank Tk1 can also be considered a gas-liquid separator that separates the electrolytic sulfuric acid solution from the hydrogen gas.

[0061] The gas supply unit 5 supplies the first gas to the tank Tk1. Because hydrogen gas also flows into the tank Tk1, the gas in the tank Tk1 contains the first gas and hydrogen gas. Because the first gas is supplied to the tank Tk1, the concentration of hydrogen gas in the tank Tk1 (hereinafter referred to as the hydrogen concentration) can be reduced. The exhaust unit 6 exhausts the gas from the tank Tk1. In other words, the exhaust unit 6 exhausts the gas with a reduced hydrogen concentration from the tank Tk1.

[0062] As shown in FIG. 3, the gas supply unit 5 includes a first gas supply pipe 511 and supplies a first gas to the tank Tk1 through the first gas supply pipe 511. The first gas is, for example, nitrogen gas. Since the first gas is a gas for reducing the hydrogen concentration, hereinafter the first gas will also be referred to as a first dilution gas. A downstream end of the first gas supply pipe 511 is connected to, for example, the ceiling of the tank Tk1, and an upstream end of the first gas supply pipe 511 is connected to a first gas supply source. The gas supply unit 5 also includes a flow rate adjuster 512 (corresponding to a first flow rate adjuster). The flow rate adjuster 512 is controlled by the control unit 90 and adjusts the flow rate of the first dilution gas flowing into the tank Tk1.

[0063] The exhaust unit 6 includes an exhaust pipe 61, and exhausts gas from the tank Tk1 to the outside (for example, a factory exhaust facility) through the exhaust pipe 61. The upstream end of the exhaust pipe 61 is connected to, for example, the ceiling of the tank Tk1, and the downstream end of the exhaust pipe 61 is connected to the outside. The exhaust unit 6 also includes a flow rate adjustment unit 62. The flow rate adjustment unit 62 is controlled by the control unit 90 and adjusts the flow rate of gas flowing out of the tank Tk1. Hereinafter, the gas flowing through the exhaust pipe 61 from the tank Tk1 will also be referred to as exhaust gas.

[0064] The drainage unit 4 includes a drainage pipe 41, and discharges the treatment liquid in the tank Tk1 to the outside (for example, to a drainage facility in a factory) through the drainage pipe 41. In the example of FIG. 3, the upstream end of the drainage pipe 41 is connected to, for example, the bottom of the tank Tk1. A drainage valve 42 is inserted in the drainage pipe 41. The drainage valve 42 is controlled by the control unit 90, and switches between opening and closing the drainage pipe 41. When the control unit 90 opens the drainage valve 42, the treatment liquid in the tank Tk1 can be discharged to the outside.

[0065] In the example of FIG. 3, the electrolytic sulfuric acid supply unit 2 also includes a recovery tank Tk2. The treatment liquid (electrolytic sulfuric acid liquid) received by the guard 14 of each treatment unit 1 is recovered in the recovery tank Tk2 through a recovery pipe 15. In the example of FIG. 3, the treatment liquid in the recovery tank Tk2 is supplied to the tank Tk1 through a liquid supply pipe 20. The upstream end of the liquid supply pipe 20 is connected to, for example, the bottom of the recovery tank Tk2, and the downstream end of the liquid supply pipe 20 is connected to, for example, the ceiling of the tank Tk1. A supply valve 201 and a liquid delivery unit 202 are inserted in the liquid supply pipe 20. The liquid delivery unit 202 is controlled by the control unit 90 and delivers the treatment liquid from the recovery tank Tk2 to the tank Tk1. The liquid delivery unit 202 is, for example, a pump. The supply valve 201 is controlled by the control unit 90 and switches the liquid supply pipe 20 on and off.

[0066] When the control unit 90 opens the supply valve 201 and operates the liquid delivery unit 202, the processing liquid is supplied from the recovery tank Tk2 to the tank Tk1. That is, the processing liquid supplied to the substrate W in the processing unit 1 is supplied again to the tank Tk1. This allows the processing liquid to be reused, thereby reducing the amount of processing liquid used.

[0067] <Outline of operation of electrolytic sulfuric acid supply unit 2> Next, the operation of the electrolytic sulfuric acid supply unit 2 will be outlined. FIG. 4 is a flowchart showing an example of the electrolytic sulfuric acid generation operation in the electrolytic sulfuric acid supply unit 2. First, the electrolytic sulfuric acid supply unit 2 starts adjusting the pressure in the tank Tk1 to negative pressure (step S1: negative pressure adjustment start step). Specifically, the control unit 90 controls the gas supply unit 5 and the exhaust unit 6 to adjust the pressure in the tank Tk1 to negative pressure. For example, the control unit 90 controls the flow rate adjustment unit 512 to adjust the flow rate of the first dilution gas to a predetermined negative pressure dilution flow rate value. The control unit 90 also controls the flow rate adjustment unit 62 to adjust the flow rate of the exhaust gas to a predetermined negative pressure exhaust flow rate value. The negative pressure dilution flow rate value and the negative pressure exhaust flow rate value can be set in advance so that the pressure in the tank Tk1 becomes negative pressure. In the next step S2, the electrolytic sulfuric acid supply unit 2 also adjusts the pressure in the tank Tk1 to negative pressure.

[0068] Next, the electrolytic sulfuric acid supply unit 2 electrolyzes the treatment solution to generate electrolytic sulfuric acid while circulating the treatment solution through the circulation unit 3 (step S2: electrolysis circulation step). Specifically, the control unit 90 opens the circulation valve 33 and activates the solution delivery unit 34 and the electrolytic cell 32. As a result, electrolytic sulfuric acid is generated in the internal flow path of the electrolytic cell 32, and hydrogen gas is also generated as a by-product. The electrolytic sulfuric acid and hydrogen gas flow into the tank Tk1.

[0069] The hydrogen gas that flows into the tank Tk1 is discharged to the outside as exhaust gas together with the first dilution gas through the exhaust pipe 61. Because the first dilution gas is supplied into the tank Tk1, the hydrogen concentration in the exhaust gas flowing through the exhaust pipe 61 can be reduced. The negative pressure dilution flow rate value of the first dilution gas is set in advance so that the hydrogen concentration of the gas in the tank Tk1 is equal to or less than a first reference value (e.g., 4 vol%). The negative pressure exhaust flow rate value of the exhaust gas is set in advance so that the pressure in the tank Tk1 becomes negative.

[0070] As described above, the control unit 90 controls the circulation unit 3, the gas supply unit 5, and the exhaust unit 6 to adjust the pressure inside the tank Tk1 to a negative pressure during electrolysis of the treatment solution. As a result, hydrogen gas generated in the internal flow path of the electrolytic cell 32 is drawn into the tank Tk1. This makes it easier for hydrogen gas to flow into the tank Tk1. In other words, this reduces the possibility that hydrogen gas will stagnate in the electrolytic cell 32 or the circulation piping 31. This allows the electrolytic sulfuric acid supply unit 2 to appropriately exhaust hydrogen gas to the outside.

[0071] The processing liquid in the tank Tk1 includes processing liquid that has been used to process substrates W. Therefore, the processing liquid in the tank Tk1 gradually deteriorates as the number of processed substrates W increases. When the degree of deterioration of the processing liquid in the tank Tk1 increases, it becomes necessary to replace the processing liquid in the tank Tk1. In other words, the electrolytic sulfuric acid supply unit 2 discharges the processing liquid in the tank Tk1 and supplies new processing liquid to the tank Tk1. Note that new liquid here refers to processing liquid that has never been supplied to a substrate W.

[0072] FIG. 5 is a flowchart showing an example of the treatment solution discharge operation in the electrolytic sulfuric acid supply unit 2. First, the electrolytic sulfuric acid supply unit 2 starts adjusting the pressure in the tank Tk1 to a positive pressure (step S11: positive pressure adjustment start step). Specifically, the control unit 90 controls the gas supply unit 5 and the exhaust unit 6 to adjust the pressure in the tank Tk1 to a positive pressure. For example, the control unit 90 controls the flow rate adjustment unit 512 to adjust the flow rate of the first dilution gas to a predetermined positive pressure dilution flow rate value. The control unit 90 also controls the flow rate adjustment unit 62 to adjust the flow rate of the exhaust gas to a predetermined positive pressure exhaust flow rate value. The positive pressure dilution flow rate value and the positive pressure exhaust flow rate value can be set in advance so that the pressure in the tank Tk1 becomes positive. In the next step S12, the electrolytic sulfuric acid supply unit 2 continues to adjust the pressure in the tank Tk1 to a positive pressure.

[0073] Next, the drainage unit 4 drains the treatment liquid in the tank Tk1 to the outside (step S12: drainage step). Specifically, the control unit 90 opens the drainage valve 42. This causes the treatment liquid in the tank Tk1 to be drained through the drainage pipe 41. When the tank Tk1 is empty, the control unit 90 closes the drainage valve 42.

[0074] Next, the electrolytic sulfuric acid supply unit 2 supplies new treatment liquid to the tank Tk1 by a new liquid supply unit (not shown), thereby allowing the electrolytic sulfuric acid supply unit 2 to replace the treatment liquid in the tank Tk1 with the new treatment liquid.

[0075] As described above, the control unit 90 controls the drain unit 4, the gas supply unit 5, and the exhaust unit 6 to adjust the pressure inside the tank Tk1 to a positive pressure while the treatment liquid is being discharged. Therefore, while the treatment liquid is being discharged, the gas presses the treatment liquid inside the tank Tk1 toward the drain pipe 41. This allows the drain unit 4 to quickly discharge the treatment liquid. The electrolytic sulfuric acid supply unit 2 adjusts the pressure inside the tank Tk1 to a positive pressure even after the tank Tk1 is substantially empty and before the drain valve 42 is closed. This reduces the possibility of external gas flowing into the tank Tk1 through the drain pipe 41. Because the purity of external gas is not high, if external gas flows into the tank Tk1, the tank Tk1 may be contaminated. If the tank Tk1 is contaminated, the treatment liquid flowing into the tank Tk1 may also be contaminated. In this embodiment, the pressure inside the tank Tk1 while the processing liquid is being discharged is positive, which reduces the possibility of external gases entering the tank Tk1 and suppresses contamination of the tank Tk1 and the processing liquid.

[0076] In the example of FIG. 3, the drainage unit 4 also includes a drainage pipe 43. The upstream end of the drainage pipe 43 is connected to the circulation pipe 31. In the example of FIG. 3, the upstream end of the drainage pipe 43 is connected to the circulation pipe 31 between the liquid delivery unit 34 and the circulation valve 33. The downstream end of the drainage pipe 43 is connected to the outside (for example, a drainage facility in a factory). A drainage valve 44 is inserted in the drainage pipe 43. The drainage valve 44 is controlled by the control unit 90 to switch the drainage pipe 43 between open and closed states.

[0077] The control unit 90 opens the drain valve 44, which allows the drain unit 4 to drain the treatment liquid from the circulation pipe 31. As an example, after the control unit 90 drains the treatment liquid from the tank Tk1 to the outside, it closes the drain valve 42 and opens the drain valve 44. As a result, the treatment liquid from the circulation pipe 31 is drained to the outside through the drain pipe 43. Even while the treatment liquid is being drained, the control unit 90 controls the gas supply unit 5 and the exhaust unit 6 to adjust the pressure in the tank Tk1 to a positive pressure. This allows the pressure in the circulation pipe 31 to also be made positive. This allows the treatment liquid from the circulation pipe 31 to be discharged more quickly. Furthermore, this reduces the possibility of external gases flowing into the circulation pipe 31 through the drain pipe 43. This also reduces contamination of the circulation pipe 31.

[0078] <Flow rate> 6 is a diagram showing an example of the change over time in the flow rate of the first dilution gas (dilution flow rate), the change over time in the flow rate of the exhaust gas (exhaust flow rate), and the change over time in the pressure in the tank Tk1. The example in FIG. 6 shows the flow rate and pressure during the generation of electrolytic sulfuric acid (i.e., during the electrolysis of the treatment liquid), and the flow rate and pressure during the discharge of the treatment liquid.

[0079] As shown in FIG. 6, the dilution flow rate of the first dilution gas assumes a negative pressure dilution flow rate value during the generation of electrolytic sulfuric acid and a positive pressure dilution flow rate value during the discharge of the treated solution. As shown in FIG. 6, the negative pressure dilution flow rate value may be set higher than the positive pressure dilution flow rate value. That is, the control unit 90 controls the dilution flow rate of the first dilution gas during the electrolysis of the treated solution to be higher than the dilution flow rate of the first dilution gas during the discharge of the treated solution. Because the negative pressure dilution flow rate value is high, the hydrogen concentration of the exhaust gas during the generation of electrolytic sulfuric acid can be appropriately reduced. On the other hand, since the electrolytic cell 32 does not operate during the discharge of the treated solution, hydrogen gas is not generated in the electrolytic cell 32. Therefore, even if the positive pressure dilution flow rate value is low during the discharge of the treated solution, the hydrogen concentration of the exhaust gas does not increase. Furthermore, a low positive pressure dilution flow rate value can effectively reduce the amount of first dilution gas used. Therefore, the running costs of the electrolytic sulfuric acid supply unit 2 can be reduced.

[0080] As shown in Figure 6, the exhaust flow rate of the exhaust gas takes a negative pressure exhaust flow rate value during the generation of electrolytic sulfuric acid and a positive pressure exhaust flow rate value during the discharge of the treated liquid. As shown in Figure 6, the negative pressure exhaust flow rate value can be set higher than the positive pressure exhaust flow rate value. Because the negative pressure exhaust flow rate value is higher, the pressure in tank Tk1 can be appropriately reduced during the generation of electrolytic sulfuric acid. In other words, the pressure in tank Tk1 can be appropriately adjusted to a negative pressure. On the other hand, because the positive pressure exhaust flow rate value is lower during the discharge of the treated liquid, the pressure in tank Tk1 can be appropriately adjusted to a positive pressure during the discharge of the treated liquid.

[0081] <Detailed example of electrolytic sulfuric acid supply unit 2> FIG. 7 is a diagram schematically illustrating an example of a more specific configuration of the electrolytic sulfuric acid supply unit 2. As shown in FIG.

[0082] <Gas supply section> 7, the gas supply unit 5 includes a first gas supply unit 51 and a second gas supply unit 52. The first gas supply unit 51 includes a first air supply pipe 511. In the example of FIG. 7, the first air supply pipe 511 includes a common pipe 513, a first branch pipe 514, and a second branch pipe 515, which will be described later. The first gas supply unit 51 supplies a first dilution gas to the tank Tk1 through the first air supply pipe 511.

[0083] The second gas supply unit 52 includes a second air supply pipe 521, and supplies a second gas (hereinafter also referred to as a second dilution gas) to the exhaust pipe 61 through the second air supply pipe 521. A downstream end of the second air supply pipe 521 is connected to a connection position P1 midway through the exhaust pipe 61, and an upstream end of the second air supply pipe 521 is connected to a second gas supply source. A supply valve 522 is inserted in the second air supply pipe 521. The supply valve 522 is controlled by the control unit 90, and switches between opening and closing the second air supply pipe 521. When the control unit 90 opens the supply valve 522, the second gas is supplied to the exhaust pipe 61 through the second air supply pipe 521.

[0084] The second diluent gas is a gas with a lower purity than the first diluent gas, such as air. For example, the particle content of the second diluent gas is higher than the particle content of the first diluent gas. Alternatively, the purity of the second diluent gas is lower than the purity of the first diluent gas. Thus, while the second diluent gas has a lower purity than the first diluent gas, the second diluent gas is less expensive than the first diluent gas.

[0085] The space within the tank Tk1 constitutes part of the circular circulation path and also constitutes part of the exhaust path. The first gas supply unit 51 supplies a highly clean first dilution gas into the tank Tk1, so contamination of the tank Tk1 by the first dilution gas is hardly caused. Consequently, contamination of the processing liquid flowing into the tank Tk1 is also hardly caused. Nitrogen gas has a proven track record of being used in processing substrates W, so using nitrogen gas as the first dilution gas can more reliably reduce contamination of the processing liquid.

[0086] On the other hand, the space inside the exhaust pipe 61 is not included in the annular circulation path. Therefore, even if the second diluent gas flows into the exhaust pipe 61, the second diluent gas hardly flows into the annular circulation path. Therefore, even if the cleanliness of the second diluent gas is low, the annular circulation path and the processing liquid are hardly contaminated.

[0087] Furthermore, by flowing the second dilution gas into the exhaust pipe 61, the hydrogen concentration of the exhaust gas flowing through the exhaust pipe 61 can be further reduced. For example, by supplying the first dilution gas, the hydrogen concentration of the exhaust gas in the tank Tk1 becomes equal to or less than a first standard value (e.g., 4 vol%), and by supplying the second dilution gas, the hydrogen concentration of the exhaust gas becomes equal to or less than a second standard value. The second standard value is lower than the first standard value, for example, equal to or less than one-fourth of the first standard value.

[0088] As described above, in the above example, in order to make the hydrogen concentration of the exhaust gas equal to or less than the second reference value, not only the first diluent gas but also the cheaper second diluent gas is used. Therefore, compared to using only the first diluent gas, the electrolytic sulfuric acid supply unit 2 can make the hydrogen concentration of the exhaust gas equal to or less than the second reference value more cheaply. Furthermore, since air is inexpensive, using air as the second diluent gas can more appropriately reduce running costs.

[0089] 7, the upstream end of the first branch pipe 514 and the upstream end of the second branch pipe 515 are connected to the downstream end of the common pipe 513, and the upstream end of the common pipe 513 is connected to the first gas supply source. The downstream ends of the first branch pipe 514 and the second branch pipe 515 are connected to, for example, the ceiling of the tank Tk1. A supply valve 516 is inserted in the first branch pipe 514, and a supply valve 517 is inserted in the second branch pipe 515. The supply valve 516 is controlled by the control unit 90 to switch the first branch pipe 514 between open and closed states. The supply valve 517 is controlled by the control unit 90 to switch the second branch pipe 515 between open and closed states.

[0090] The dilution flow rate of the first dilution gas flowing into the tank Tk1 when only one of the supply valves 516 and 517 is open is smaller than the dilution flow rate of the first dilution gas flowing into the tank Tk1 when both the supply valves 516 and 517 are open. In this way, the dilution flow rate can be changed by opening and closing the supply valves 516 and 517. For this reason, it can be said that the supply valves 516 and 517 form the flow rate adjustment unit 512.

[0091] 7, first branch pipe 514 is provided with flow meter Sn511, second branch pipe 515 is provided with flow meter Sn512, and second air supply pipe 521 is provided with flow meter Sn52. Flow meter Sn511 measures the flow rate of the first dilution gas flowing through first branch pipe 514 and outputs an electrical signal indicating the measurement result to control unit 90. Flow meter Sn512 measures the flow rate of the first dilution gas flowing through second branch pipe 515 and outputs an electrical signal indicating the measurement result to control unit 90. Flow meter Sn52 measures the flow rate of the second dilution gas flowing through second air supply pipe 521 and outputs an electrical signal indicating the measurement result to control unit 90.

[0092] <Exhaust section> In the example of FIG. 7, the exhaust section 6 also includes a capture section 63. In the example of FIG. 7, the capture section 63 includes a demister 631 and a filter 632. The capture section 63 is provided in the exhaust pipe 61 and captures a target substance in the exhaust gas flowing through the exhaust pipe 61. The demister 631 has a mesh shape. The demister 631 may be formed of, for example, a fluorine-based resin. When the exhaust gas passes through the mesh openings of the demister 631, mist (for example, sulfuric acid mist) contained in the exhaust gas is captured by the demister 631. This capture reduces the amount of mist in the exhaust gas flowing downstream of the demister 631.

[0093] In the example of FIG. 7, the filter 632 is provided downstream of the demister 631. The filter 632 also has a mesh shape. When the exhaust gas passes through the mesh openings of the filter 632, ozone gas in the exhaust gas is captured by the filter 632. Note that, like hydrogen gas, ozone gas is generated secondarily by the electrolysis of the treatment liquid in the electrolysis cell 32. The filter 632 can reduce the amount of ozone in the exhaust gas flowing downstream of the filter 632.

[0094] 7, a fan 621 is shown as the flow rate adjustment unit 62. The fan 621 is provided in the exhaust pipe 61 downstream of the capture unit 63. The fan 621 is controlled by the control unit 90, and adjusts the exhaust flow rate of the exhaust gas flowing through the exhaust pipe 61.

[0095] 7, the downstream end of the second air supply pipe 521 is connected to the exhaust pipe 61 downstream of the trapping section 63. Specifically, the downstream end of the second air supply pipe 521 is connected to the exhaust pipe 61 downstream of both the demister 631 and the filter 632. In the example of FIG. 7, the downstream end of the second air supply pipe 521 is connected to the exhaust pipe 61 between the trapping section 63 and the fan 621. Therefore, the second diluted gas does not pass through the trapping section 63.

[0096] Now, since the trapping section 63 has a mesh-like shape for trapping the target substance in the exhaust gas, the pressure loss in the trapping section 63 is relatively large. Therefore, if the downstream end of the second air supply pipe 521 is connected to the exhaust pipe 61 upstream of the trapping section 63, the second diluted gas will be subjected to a pressure loss by the trapping section 63. In contrast, in the above example, the second diluted gas does not pass through the trapping section 63. Therefore, the second gas supplying section 52 can supply a large flow rate of the second diluted gas to the exhaust pipe 61 with less energy. Therefore, for example, the power consumption of the fan 621 can be reduced.

[0097] 7, a flow meter Sn6 is provided in the exhaust pipe 61. Specifically, the flow meter Sn6 is provided in the exhaust pipe 61 downstream of the downstream end of the second air intake pipe 521. The flow meter Sn6 measures the flow rate of the exhaust gas flowing through the exhaust pipe 61, and outputs an electrical signal indicating the measurement result to the control unit 90.

[0098] <Circulation section> In the example of FIG. 7 , the circulation unit 3 further includes a temperature adjustment unit 35, a filter 36, and a flow rate adjustment unit 37. The temperature adjustment unit 35 is provided in the circulation pipe 31. The temperature adjustment unit 35 is controlled by the control unit 90 and adjusts the temperature of the treatment liquid flowing through the circulation pipe 31. The temperature adjustment unit 35 may have a heating function or both a heating function and a cooling function. That is, the temperature adjustment unit 35 may include a heating unit having only a heating function, a heating unit having only a heating function and a cooling unit having only a cooling function, or a Peltier element having both a heating function and a cooling function. The heating unit may be, for example, an electric resistance heater or a radiation heater. The cooling unit may include, for example, a heat exchanger through which a refrigerant such as water flows.

[0099] The filter 36 is provided in the circulation pipe 31. The filter 36 captures impurities from the treatment liquid. The impurities include, for example, particles. The filter 36 has, for example, a mesh shape. The filter 36 is provided in the circulation pipe 31 downstream of both the liquid delivery unit 34 and the temperature adjustment unit 35. In the example of FIG. 7, the filter 36 is provided between the set of the liquid delivery unit 34 and the temperature adjustment unit 35 and the electrolytic cell 32.

[0100] The flow rate adjustment unit 37 is inserted in the circulation pipe 31. In the example of FIG. 7, the flow rate adjustment unit 37 is provided in the circulation pipe 31 downstream of the filter 36. In the example of FIG. 7, the flow rate adjustment unit 37 is provided between the filter 36 and the electrolytic cell 32. The flow rate adjustment unit 37 is controlled by the control unit 90 and adjusts the flow rate of the treatment liquid flowing into the electrolytic cell 32. In the example of FIG. 7, the flow rate adjustment unit 37 includes a flow rate adjustment valve 371 and a regulator 372. In the example of FIG. 7, the regulator 372 is provided between the flow rate adjustment valve 371 and the electrolytic cell 32. The regulator 372 can adjust the flow rate with higher accuracy than the flow rate adjustment valve 371. The flow rate adjustment valve 371 can adjust the flow rate, for example, in a wider range than the regulator 372.

[0101] In the example of FIG. 7, the circulation unit 3 is also provided with a flow meter Sn33. The flow meter Sn33 is provided in the circulation pipe 31 downstream of the circulation valve 33. In the example of FIG. 7, the flow meter Sn33 is provided between the flow rate control valve 371 and the regulator 372. The flow meter Sn33 measures the flow rate of the treatment liquid flowing into the electrolytic cell 32 and outputs an electrical signal indicating the measurement result to the control unit 90. The control unit 90 may control the flow rate adjustment unit 37 based on the flow rate measured by the flow meter Sn33. This allows the flow rate adjustment unit 37 to adjust the flow rate of the treatment liquid flowing into the electrolytic cell 32 with high accuracy.

[0102] <Temperature control circulation section> Because the treatment liquid contains sulfuric acid, the viscosity of the treatment liquid increases as the temperature decreases. When the viscosity of the treatment liquid is high, the treatment liquid is less likely to pass through the filter 36. Therefore, in the example of FIG. 7, the electrolytic sulfuric acid supply unit 2 further includes a temperature-controlled circulation unit 45. The temperature-controlled circulation unit 45 adjusts the temperature of the treatment liquid to a temperature that allows the treatment liquid to easily pass through the filter 36. The temperature-controlled circulation unit 45 includes a temperature-controlled circulation pipe 46 and a temperature control unit 35. In the example of FIG. 7, the temperature-controlled circulation pipe 46 includes a portion of the circulation pipe 31 and a branch pipe 461. The upstream end of the branch pipe 461 is connected to the circulation pipe 31 at a connection position P1 between the temperature control unit 35 and the filter 36. In the example of FIG. 7, the downstream end of the branch pipe 461 is connected to the ceiling of the tank Tk1. In the example of FIG. 7, the portion of the circulation pipe 31 between the upstream end and the connection position P1 functions as part of the temperature-controlled circulation pipe 46. A circulation valve 47 is inserted in the branch pipe 461. The circulation valve 47 is controlled by the control unit 90 to switch the branch pipe 461 between open and closed states.

[0103] When the control unit 90 operates the liquid delivery unit 34 while opening the circulation valve 47, the treatment liquid circulates through a temperature-controlled circulation path that includes the tank Tk1 and the temperature-controlled circulation pipe 46. This temperature-controlled circulation path does not include a filter 36. Therefore, even if the treatment liquid has a high viscosity, the treatment liquid can flow appropriately through the temperature-controlled circulation path. The control unit 90 then controls the temperature adjustment unit 35 to heat the treatment liquid. This increases the temperature of the treatment liquid during circulation. As the temperature increases, the viscosity of the treatment liquid decreases. As the viscosity decreases, the treatment liquid is more likely to pass through the filter 36.

[0104] 7, a thermometer Sn32 is provided. The thermometer Sn32 is provided between the temperature adjustment unit 35 and the connection position P1. The thermometer Sn32 measures the temperature of the treatment liquid and outputs an electrical signal indicating the measurement result to the control unit 90. The control unit 90 may control the temperature adjustment unit 35 based on the temperature measured by the thermometer Sn32. This allows the temperature adjustment unit 35 to adjust the temperature of the treatment liquid with higher accuracy.

[0105] 7, a flow meter Sn31 is provided. The flow meter Sn31 is provided in the circulation pipe 31 upstream of the connection position P1. The flow meter Sn31 measures the flow rate of the treatment liquid flowing through the circulation pipe 31, and outputs an electrical signal indicating the measurement result to the control unit 90. The control unit 90 may control the liquid delivery unit 34 based on the flow rate measured by the flow meter Sn31.

[0106] <Measurement circulation section> In the example of FIG. 7, the electrolytic sulfuric acid supply unit 2 also includes a measurement circulation unit 8. The measurement circulation unit 8 includes a measurement circulation pipe 81. In the example of FIG. 7, the measurement circulation pipe 81 includes a part of the circulation pipe 31 and a branch pipe 811. In the example of FIG. 7, the upstream end of the branch pipe 811 is connected to the secondary side of the filter 36, and the downstream end of the branch pipe 811 is connected to the ceiling of the tank Tk1. In the example of FIG. 7, the part between the upstream end of the circulation pipe 31 and the filter 36 functions as part of the measurement circulation pipe 81.

[0107] The branch pipe 811 is provided with a concentration meter Sn81. The concentration meter Sn81 measures the sulfuric acid concentration of the treatment liquid flowing through the branch pipe 811, and outputs a signal indicating the measurement result to the control unit 90. The branch pipe 811 is also provided with a concentration meter Sn82. The concentration meter Sn82 measures the persulfuric acid concentration of the treatment liquid flowing through the branch pipe 811, and outputs a signal indicating the measurement result to the control unit 90.

[0108] The electrolytic sulfuric acid supply unit 2 does not necessarily have to include the measurement circulation unit 8, and for example, the concentration meter Sn81 and the concentration meter Sn82 may be provided in the tank Tk1.

[0109] <External circulation piping> In the example of FIG. 7, the electrolytic sulfuric acid supply unit 2 further includes a liquid delivery unit 23, a heating unit 24, a cooling unit 25, and a regulator 26. The liquid delivery unit 23 is provided in the external circulation piping 21 (specifically, the outward piping 211). The liquid delivery unit 23 is controlled by the control unit 90 and delivers the treatment liquid. The liquid delivery unit 23 is, for example, a pump. The heating unit 24 is provided in the outward piping 211 upstream of the connection points with the liquid supply pipes 132 of all the treatment units 1. The heating unit 24 is controlled by the control unit 90 and heats the treatment liquid flowing through the outward piping 211. The heating unit 24 is, for example, an electric resistance heater or a radiation heater. The heating unit 24 adjusts the temperature of the treatment liquid to within a temperature range suitable for treatment.

[0110] The cooling section 25 is provided on the return pipe 212 downstream of the connection point with the liquid supply pipes 132 of all the processing units 1. The cooling section 25 is controlled by the control section 90 and cools the treatment liquid flowing through the return pipe 212. The cooling section 25 includes a heat exchanger through which a refrigerant such as water flows. The cooling section 25 adjusts the temperature of the treatment liquid to a temperature range in which the electrolytic sulfuric acid is not easily deactivated.

[0111] The regulator 26 is provided in the return pipe 212 downstream of the connection point with the liquid supply pipes 132 of all the processing units 1. The regulator 26 is controlled by the control unit 90, and adjusts the flow rate of the processing liquid flowing through the return pipe 212 to be approximately constant.

[0112] <Pure water supply section> In the example of FIG. 7, the electrolytic sulfuric acid supply unit 2 also includes a pure water supply unit 85. The pure water supply unit 85 supplies pure water (e.g., new solution) to the tank Tk1. In the example of FIG. 7, the pure water supply unit 85 includes a liquid supply pipe 851 and a supply valve 852. In the example of FIG. 7, the downstream end of the liquid supply pipe 851 is connected to the ceiling of the tank Tk1, and the upstream end of the liquid supply pipe 851 is connected to a pure water supply source. The supply valve 852 is inserted into the liquid supply pipe 851. The supply valve 852 is controlled by the control unit 90 to switch the liquid supply pipe 851 between open and closed states.

[0113] When the control unit 90 opens the supply valve 852, pure water is supplied to the tank Tk1 through the liquid supply pipe 851. This makes it possible to reduce the sulfuric acid concentration of the processing liquid in the tank Tk1.

[0114] <Sulfuric acid supply section> In the example of FIG. 7, the electrolytic sulfuric acid supply unit 2 also includes a sulfuric acid supply unit 86. The sulfuric acid supply unit 86 supplies sulfuric acid (e.g., new solution) to the tank Tk1. In the example of FIG. 7, the sulfuric acid supply unit 86 includes a liquid supply pipe 861 and a supply valve 862. In the example of FIG. 7, the downstream end of the liquid supply pipe 861 is connected to the ceiling of the tank Tk1, and the upstream end of the liquid supply pipe 861 is connected to a sulfuric acid supply source. The supply valve 862 is inserted in the liquid supply pipe 861. The supply valve 862 is controlled by the control unit 90 to switch the liquid supply pipe 861 between open and closed states.

[0115] When the control unit 90 opens the supply valve 862, sulfuric acid is supplied to the tank Tk1 through the liquid supply pipe 861. This makes it possible to increase the sulfuric acid concentration of the treatment liquid in the tank Tk1.

[0116] <Detailed operation example of electrolytic sulfuric acid supply unit 2> Fig. 8 is a flowchart showing an example of the operation of the electrolytic sulfuric acid supply unit 2. Fig. 8 shows an example of the operation of generating electrolytic sulfuric acid. Fig. 9 to Fig. 12 are diagrams schematically showing an example of the state of the electrolytic sulfuric acid supply unit 2 in each step.

[0117] First, the electrolytic sulfuric acid supply unit 2 starts adjusting the pressure in the tank Tk1 to a positive pressure (step S31: positive pressure adjustment start step). That is, the control unit 90 controls the gas supply unit 5 and the exhaust unit 6 to adjust the pressure in the tank Tk1 to a positive pressure. Specifically, as shown in FIG. 9, the control unit 90 opens the supply valve 516 while keeping the supply valve 517 closed, and operates the fan 621. In the figure, valves in an open state are indicated by solid black valves. Also in the figure, the piping through which the fluid flows is schematically indicated by thick lines.

[0118] When the supply valve 516 opens, the first dilution gas flows into the tank Tk1 through the first branch pipe 514 at a positive pressure dilution flow rate. The positive pressure dilution flow rate is set to, for example, several hundred L (liters) / min (specifically, 700 L / min). The fan 621 sucks the exhaust gas from the tank Tk1. The control unit 90 controls the fan 621 so that the flow rate of the exhaust gas flowing through the exhaust pipe 61 becomes the positive pressure exhaust flow rate. This adjusts the pressure in the tank Tk1 to a positive pressure. The electrolytic sulfuric acid supply unit 2 continues to adjust the pressure in the tank Tk1 to a positive pressure until immediately before step S34, which will be described later.

[0119] In the example of Fig. 9, the tank Tk1 is provided with a pressure gauge Sn35. The pressure gauge Sn35 measures the pressure inside the tank Tk1 and outputs an electric signal indicating the measurement result to the control unit 90. The control unit 90 may control the fan 621 based on the pressure measured by the pressure gauge Sn35. This allows the electrolytic sulfuric acid supply unit 2 to adjust the pressure inside the tank Tk1 to a positive pressure with higher accuracy.

[0120] Once the pressure in the tank Tk1 is adjusted to a positive pressure, the electrolytic sulfuric acid supply unit 2 increases the temperature in the tank Tk1 (step S32: preliminary temperature adjustment process). Specifically, as shown in FIG. 10, first, the control unit 90 opens the circulation valve 47 and activates the liquid delivery unit 34. As a result, the treatment liquid circulates through a temperature-controlled circulation path including the tank Tk1 and the temperature-controlled circulation pipe 46. Because the viscosity of the sulfuric acid in the treatment liquid is high at room temperature, initially, the treatment liquid does not pass through the filter 36 very much. In other words, a highly viscous treatment liquid cannot pass through the fine-mesh filter 36 very much. Therefore, initially, as shown in FIG. 10, the treatment liquid mainly circulates through the temperature-controlled circulation path.

[0121] The control unit 90 controls the temperature adjustment unit 35 to heat the treatment liquid. As a result, the temperature of the circulating treatment liquid increases over time. As the temperature increases, the viscosity of the treatment liquid decreases. As a result, the amount of treatment liquid passing through the filter 36 increases over time. Therefore, some of the treatment liquid also flows through the measurement circulation pipe 81. In the example of FIG. 10 , the control unit 90 also opens the circulation valve 33 and the external circulation valve 22 in step S32. As a result, the treatment liquid also flows through the circulation pipe 31 and the external circulation pipe 21.

[0122] When the temperature of the treatment liquid measured by the thermometer Sn32 reaches a predetermined temperature at which the treatment liquid can sufficiently pass through the filter 36, the control unit 90 closes the circulation valve 47 as shown in Fig. 11. This causes the treatment liquid to stop flowing through the branch pipe 461. In the example of Fig. 11, the treatment liquid circulates through the measurement circulation path, the electrolysis circulation path, and the external circulation path.

[0123] Next, the electrolytic sulfuric acid supply unit 2 adjusts the sulfuric acid concentration, temperature, and flow rate of the treatment solution to values ​​suitable for generating electrolytic sulfuric acid (step S33: preparatory circulation process). Hereinafter, the range between a predetermined concentration lower limit and a predetermined concentration upper limit is considered to be the sulfuric acid concentration range suitable for generating electrolytic sulfuric acid. For example, the control unit 90 opens the supply valve 852 when the measured concentration of sulfuric acid measured by the concentration meter Sn81 is equal to or greater than a predetermined concentration upper limit. This causes pure water to be supplied into the tank Tk1, and the sulfuric acid concentration of the treatment solution in the tank Tk1 decreases. The control unit 90 closes the supply valve 852 when the measured concentration falls below the concentration upper limit. On the other hand, the control unit 90 opens the supply valve 862 when the measured concentration is equal to or less than a predetermined concentration lower limit. This causes sulfuric acid to be supplied to the tank Tk1, and the sulfuric acid concentration of the treatment solution in the tank Tk1 increases. The control unit 90 closes the supply valve 862 when the measured concentration exceeds a predetermined concentration lower limit. The concentration upper limit and concentration lower limit are, for example, set in advance.

[0124] The control unit 90 controls the flow rate adjustment unit 37 so that the flow rate measured by the flow meter Sn33 falls within a predetermined flow rate range. This flow rate range is a flow rate range suitable for producing electrolytic sulfuric acid and can be set in advance.

[0125] The control unit 90 controls the temperature adjustment unit 35 so that the temperature measured by the thermometer Sn32 falls within a predetermined temperature range. This temperature range is suitable for generating electrolytic sulfuric acid and may be set in advance. For example, this temperature range is between 40°C and 60°C.

[0126] Incidentally, persulfuric acid can self-decompose into Caro's acid and hydroxyl radicals (OH radicals). If persulfuric acid self-decomposes without reacting with organic matter on the substrate W, efficiency will decrease. Therefore, the temperature adjustment unit 35 may adjust the temperature of the processing solution to within a temperature range in which persulfuric acid is unlikely to self-decompose. The temperature range is, for example, 40°C or higher and 60°C or lower.

[0127] When the sulfuric acid concentration, flow rate, and temperature of the treatment solution reach values ​​appropriate for generating electrolytic sulfuric acid, the electrolytic sulfuric acid supply unit 2 starts adjusting the pressure in the tank Tk1 to a negative pressure (step S34: negative pressure adjustment start step). That is, the control unit 90 controls the gas supply unit 5 and the exhaust unit 6 to adjust the pressure in the tank Tk1 to a negative pressure. Specifically, as shown in FIG. 12, the control unit 90 opens the supply valves 516, 517, and 522. By opening the supply valves 516 and 517, the gas supply unit 5 supplies the first dilution gas to the tank Tk1 at a negative pressure dilution flow rate value greater than the positive pressure dilution flow rate value. The negative pressure dilution flow rate value is set to, for example, several thousand L (liters) / min (specifically, 2400 L / min). Furthermore, by opening the supply valve 522, the gas supply unit 5 supplies the second dilution gas to the exhaust pipe 61. Furthermore, the control unit 90 controls the fan 621 based on the measurement results from the flow meter Sn6 or the pressure meter Sn35. The electrolytic sulfuric acid supply unit 2 continues to adjust the pressure in the tank Tk1 to a negative pressure even during the generation of the next electrolytic sulfuric acid.

[0128] Next, the electrolytic sulfuric acid supply unit 2 electrolyzes the treatment solution to produce electrolytic sulfuric acid (step S35: electrolysis circulation step). Specifically, the control unit 90 operates the electrolytic cell 32. That is, the control unit 90 controls the DC power supply to output a DC voltage between the positive and negative electrodes of the electrolytic cell 32. As a result, sulfuric acid is electrolyzed in the internal flow path of the electrolytic cell 32 to produce persulfuric acid.

[0129] This electrolysis also generates hydrogen gas and ozone gas as by-products. The hydrogen gas and ozone gas flow into the tank Tk1 together with the treatment liquid (electrolytic sulfuric acid solution). Because the pressure in the tank Tk1 is negative, the hydrogen gas and ozone gas are sucked into the tank Tk1. This reduces the possibility that the hydrogen gas and ozone gas will remain inside the electrolysis cell 32 and in the circulation pipe 31.

[0130] Furthermore, since the flow rate value of the first dilution gas flowing into the tank Tk1 is greater than the positive pressure dilution flow rate value, the hydrogen concentration of the exhaust gas in the tank Tk1 can be more appropriately reduced. The exhaust gas in the tank Tk1 is discharged to the outside through the exhaust pipe 61. In the example of FIG. 12, the exhaust gas passes through a demister 631 and a filter 632. Mist (e.g., sulfuric acid mist) in the exhaust gas is captured by the demister 631, and ozone gas in the exhaust gas is captured by the filter 632. The second dilution gas joins the exhaust gas downstream of the capture section 63. This joining allows the hydrogen concentration of the exhaust gas to be further reduced.

[0131] Incidentally, heat may be generated due to electrolysis in the electrolytic cell 32. This heat may increase the temperature of the electrolytic sulfuric acid solution. Therefore, the temperature adjustment unit 35 may cool the treatment solution to adjust the temperature of the treatment solution to within a temperature range suitable for generating electrolytic sulfuric acid.

[0132] In step S35, the electrolytic sulfuric acid solution continues to flow into the electrolytic cell 32, so the concentration of persulfuric acid in the electrolytic sulfuric acid solution increases over time.

[0133] Then, when the persulfuric acid concentration measured by the concentration meter Sn82 falls within a concentration range suitable for processing the substrate W, the electrolytic sulfuric acid supply unit 2 adjusts the flow rate and temperature of the electrolytic sulfuric acid solution flowing through the external circulation pipe 21 (step S36: electrolytic external circulation step). Specifically, the control unit 90 operates the solution delivery unit 23, the heating unit 24, the cooling unit 25, and the regulator 26. The solution delivery unit 23 delivers the electrolytic sulfuric acid solution from the upstream side to the downstream side of the external circulation pipe 21. The heating unit 24 raises the temperature of the electrolytic sulfuric acid solution to a temperature suitable for processing the substrate W. For example, the heating unit 24 may raise the temperature of the electrolytic sulfuric acid solution to 60 degrees Celsius or higher. The regulator 26 adjusts the flow rate of the processing solution flowing through the external circulation pipe 21 to be approximately constant. The cooling unit 25 lowers the temperature of the electrolytic sulfuric acid solution. The cooling unit 25 adjusts the temperature of the electrolytic sulfuric acid solution to within the same temperature range as the temperature adjustment unit 35.

[0134] In step S36, the circulation valve 33 is also open, and the electrolytic cell 32 is operating. Specifically, the control unit 90 continues to control the temperature and flow rate of the electrolytic sulfuric acid solution and the electrolytic cell 32 so that the persulfuric acid concentration of the electrolytic sulfuric acid solution in the tank Tk1 falls within a range suitable for processing the substrates W.

[0135] As described above, the electrolytic sulfuric acid supply unit 2 can generate electrolytic sulfuric acid solution to be supplied to each processing unit 1. In the above example, in steps S32 and S33 before the electrolytic cell 32 is activated, the pressure inside the tank Tk1 is positive. This reduces the possibility of external gases flowing into each circulation path, thereby preventing contamination of each circulation path. On the other hand, in steps S35 and S36 when the electrolytic cell 32 is activated, the pressure inside the tank Tk1 is negative. This reduces the possibility of hydrogen gas and ozone gas remaining in the electrolytic cell 32 and the circulation pipe 31.

[0136] In the above example, the gas supply unit 5 constantly supplies gas to the tank Tk1, while the exhaust unit 6 constantly exhausts gas from the tank Tk1. Therefore, even if the amount of processing liquid stored in the sealed tank Tk1 fluctuates, the pressure inside the tank Tk1 can be appropriately adjusted.

[0137] Second Embodiment FIG. 13 is a diagram schematically illustrating an example of the configuration of the electrolytic sulfuric acid supply unit 2 according to the second embodiment. As shown in FIG. 13, the electrolytic sulfuric acid supply unit 2 may further include a first hydrogen sensor Sn61. The first hydrogen sensor Sn61 measures the hydrogen concentration in the gas and outputs an electrical signal indicating the measurement result to the control unit 90. The first hydrogen sensor Sn61 may also be called a hydrogen concentration meter. As shown in FIG. 13, the first hydrogen sensor Sn61 is provided in a portion of the tank Tk1 and the exhaust pipe 61 that is upstream of the connection position P1 with the second air intake pipe 521. Therefore, the first hydrogen sensor Sn61 can measure the hydrogen concentration in the exhaust gas before the second dilution gas is mixed therewith.

[0138] As shown in FIG. 13, the first hydrogen sensor Sn61 may be provided in a portion of the exhaust pipe 61 between the trapping portion 63 and the connection position P1. In other words, the first hydrogen sensor Sn61 may be provided downstream of both the demister 631 and the filter 632, and upstream of the connection position P1. In this manner, the first hydrogen sensor Sn61 measures the hydrogen concentration of the exhaust gas after the sulfuric acid mist and ozone gas have been removed by the trapping portion 63. This reduces the possibility that the sulfuric acid mist and ozone gas will act on the first hydrogen sensor Sn61. This increases the lifespan of the first hydrogen sensor Sn61 and improves the accuracy of hydrogen concentration measurements by the first hydrogen sensor Sn61.

[0139] The control unit 90 controls the flow rate adjustment unit 512 based on the hydrogen concentration measured by the first hydrogen sensor Sn61. That is, the control unit 90 controls the flow rate of the first dilution gas based on the hydrogen concentration measured by the first hydrogen sensor Sn61. The flow rate adjustment unit 512 may include, for example, a mass flow controller. For example, the control unit 90 controls the flow rate adjustment unit 512 so that the hydrogen concentration measured by the first hydrogen sensor Sn61 is equal to or less than a predetermined first reference value. The first reference value is set in advance to, for example, 4%.

[0140] This allows the control unit 90 to control the hydrogen concentration in the exhaust gas before the second dilution gas is mixed with it with higher precision.

[0141] As a more specific example of operation, the control unit 90 compares the hydrogen concentration measured by the first hydrogen sensor Sn61 with a first threshold value. The first threshold value is set in advance to a value equal to or less than a first reference value. When the hydrogen concentration is greater than the first threshold value, the control unit 90 controls the flow rate adjuster 512 to increase the flow rate of the first diluted gas. This causes the first diluted gas to flow through the tank Tk1 and the exhaust pipe 61 at a higher flow rate. This reduces the hydrogen concentration of the exhaust gas before the second diluted gas is mixed in, making it possible to reduce the hydrogen concentration to equal to or less than the first reference value.

[0142] As shown in FIG. 13, the electrolytic sulfuric acid supply unit 2 may further include a second hydrogen sensor Sn62. Like the first hydrogen sensor Sn61, the second hydrogen sensor Sn62 measures the hydrogen concentration in the gas and outputs an electrical signal indicating the measurement result to the control unit 90. The second hydrogen sensor Sn62 may also be called a hydrogen concentration meter. The second hydrogen sensor Sn62 is provided in a portion of the exhaust pipe 61 that is downstream of the connection position P1 with the second air intake pipe 521. Therefore, the second hydrogen sensor Sn62 can measure the hydrogen concentration in the exhaust gas after the second dilution gas has been mixed in.

[0143] 13, the electrolytic sulfuric acid supply unit 2 also includes a flow rate adjustment unit 523 (corresponding to a second flow rate adjustment unit). The flow rate adjustment unit 523 adjusts the flow rate of the second dilution gas flowing through the second air supply pipe 521. The flow rate adjustment unit 523 may be, for example, a mass flow controller. The flow rate adjustment unit 523 is controlled by the control unit 90.

[0144] The control unit 90 may control the flow rate adjuster 523 based on the hydrogen concentration measured by the second hydrogen sensor Sn62. That is, the control unit 90 controls the flow rate of the second dilution gas based on the hydrogen concentration measured by the second hydrogen sensor Sn62. For example, the control unit 90 controls the flow rate adjuster 523 so that the hydrogen concentration measured by the second hydrogen sensor Sn62 is equal to or less than a predetermined second reference value. The second reference value is smaller than the first reference value and is set in advance to, for example, 1%.

[0145] This allows the control unit 90 to control the hydrogen concentration in the exhaust gas after the second dilution gas has been mixed with the exhaust gas with higher precision.

[0146] As a more specific example of operation, the control unit 90 compares the hydrogen concentration measured by the second hydrogen sensor Sn62 with a second threshold value. The second threshold value is set in advance to a value equal to or less than a second reference value. The second threshold value is set to a value smaller than the first threshold value, and the first threshold value is set to a value greater than the second reference value. When the hydrogen concentration is greater than the second threshold value, the control unit 90 controls the flow rate adjustment unit 523 to increase the flow rate of the second diluted gas. This causes the second diluted gas to flow through the exhaust pipe 61 at a greater flow rate. This reduces the hydrogen concentration of the exhaust gas after the second diluted gas has merged, making it possible to reduce the hydrogen concentration to less than the second reference value.

[0147] Fig. 14 is a flowchart showing an example of the above-mentioned control of hydrogen concentration. The flowchart in Fig. 14 is executed in parallel with the electrolytic sulfuric acid production operation. More specifically, this flowchart is repeatedly executed at least during the electrolysis of the treatment liquid.

[0148] First, the first hydrogen sensor Sn61 and the second hydrogen sensor Sn62 measure the hydrogen concentration and output the measurement results to the control unit 90 (step S41).

[0149] Next, the control unit 90 determines whether the hydrogen concentration measured by the first hydrogen sensor Sn61 is greater than a first threshold value (step S42). If the hydrogen concentration is greater than the first threshold value, the control unit 90 controls the flow rate adjustment unit 512 to increase the flow rate of the first diluted gas (step S43). The amount of increase in the flow rate of the first diluted gas can be set in advance, for example. The increase in the flow rate of the first diluted gas reduces the hydrogen concentration of the exhaust gas before the second diluted gas is mixed in.

[0150] When the hydrogen gas concentration is equal to or less than the first threshold in step S42, or following step S43, the control unit 90 determines whether the hydrogen concentration measured by the second hydrogen sensor Sn62 is greater than the second threshold (step S44). When the hydrogen concentration is greater than the second threshold, the control unit 90 controls the flow rate adjustment unit 523 to increase the flow rate of the second diluted gas (step S45). The amount of increase in the flow rate of the second diluted gas can be set in advance, for example. By increasing the flow rate of the second diluted gas, the hydrogen concentration of the exhaust gas after the second diluted gas is mixed in decreases.

[0151] By repeatedly executing the flow of Figure 14, the hydrogen concentration of the exhaust gas before the second diluted gas is mixed can be kept below the first standard value, while the hydrogen concentration of the exhaust gas after the second diluted gas is mixed can be kept below the second standard value.

[0152] In the above example, when the hydrogen concentration measured by the first hydrogen sensor Sn61 is high, the electrolytic sulfuric acid supply unit 2 increases the flow rate of the first diluted gas, not the second diluted gas, so that the electrolytic sulfuric acid supply unit 2 can appropriately reduce the hydrogen concentration of the exhaust gas before the second diluted gas is mixed in.

[0153] On the other hand, when the hydrogen concentration measured by the second hydrogen sensor Sn62 is high, the electrolytic sulfuric acid supply unit 2 increases the flow rate of the second diluted gas rather than the first diluted gas. In other words, the electrolytic sulfuric acid supply unit 2 reduces the hydrogen concentration using the second diluted gas that flows away from the capture unit 63, which has a large pressure loss. Therefore, the hydrogen concentration of the exhaust gas after the second diluted gas is combined can be reduced with less energy.

[0154] Although the pressure inside the tank Tk1 may increase due to an increase in the flow rates of the first diluent gas and the second diluent gas, the control unit 90 can control the flow rate adjustment unit 62 (e.g., the fan 621) so that the pressure inside the tank Tk1 remains negative. As a result, similar to the first embodiment, the pressure inside the tank Tk1 can be made negative, reducing the possibility of hydrogen gas and ozone gas remaining inside the electrolysis cell 32 and the circulation pipe 31.

[0155] As described above, the substrate processing apparatus 100 and the substrate processing method have been described in detail. However, the above description is merely an example in all respects, and this disclosure is not limited thereto. Furthermore, the various modifications described above can be applied in combination as long as they are not mutually contradictory. Furthermore, it is understood that many modifications not exemplified can be envisioned without departing from the scope of this disclosure. [Explanation of symbols]

[0156] 1 Processing Unit 3 Circulation section 31 Circulation piping 32 Electrolysis Cell 4 Drainage section 41,43 Drainage tube 5 Gas supply section 511 No. 1 air intake pipe 512 1st flow rate adjustment section (flow rate adjustment section) 521 Second air intake pipe 523 2nd flow rate adjustment section (flow rate adjustment section) 6 Exhaust section 61 Exhaust pipe 63 Capture unit 90 Control Unit Sn61 1st hydrogen sensor Sn62 Secondary Hydrogen Sensor Tk1 Tank W substrate S2, S35 Electrolytic circulation process (step) S12 Drainage process (step)

Claims

1. a processing unit for processing a substrate using a processing liquid; a tank for storing the treatment liquid containing sulfuric acid; a circulation section including a circulation pipe connected to the tank and an electrolysis cell inserted in the circulation pipe to generate electrolyzed sulfuric acid by electrolysis; a drainage unit including a drainage pipe connected to the tank or the circulation pipe, and discharging the treatment liquid to the outside through the drainage pipe; a gas supply unit including a first air supply pipe connected to the tank and supplying a first gas to the tank through the first air supply pipe; an exhaust unit including an exhaust pipe connected to the tank and discharging gas in the tank to the outside through the exhaust pipe; a control unit that controls the circulation unit, the gas supply unit, and the exhaust unit to adjust the pressure in the tank to a negative pressure during electrolysis of the treatment liquid; A substrate processing apparatus comprising:

2. The substrate processing apparatus according to claim 1 , The control unit controls the drain unit, the gas supply unit, and the exhaust unit to adjust the pressure in the tank to a positive pressure while the processing liquid is being discharged.

3. 3. The substrate processing apparatus according to claim 1, The control unit controls the flow rate of the first gas during electrolysis of the processing liquid to be greater than the flow rate of the first gas during discharge of the processing liquid.

4. 3. The substrate processing apparatus according to claim 1, the gas supply unit includes a second air supply pipe having a downstream end connected to a connection position midway along the exhaust pipe, and supplies a second gas having a lower degree of cleanliness than the first gas to the exhaust pipe through the second air supply pipe.

5. 5. The substrate processing apparatus according to claim 4, The substrate processing apparatus, wherein the first gas is nitrogen gas and the second gas is air.

6. 5. The substrate processing apparatus according to claim 4, the exhaust unit includes a capture unit that is provided in the exhaust pipe and captures a target to be captured in the gas flowing through the exhaust pipe, The substrate processing apparatus, wherein the downstream end of the second air supply pipe is connected to the exhaust pipe at the connection position downstream of the capture unit.

7. 5. The substrate processing apparatus according to claim 4, a first hydrogen sensor provided in a portion of the tank and the exhaust pipe upstream of the connection position, the first hydrogen sensor measuring a hydrogen concentration in the gas; a first flow rate adjusting unit provided in the first air supply pipe and configured to adjust a flow rate of the first gas; Equipped with The control unit controls the first flow rate adjustment unit based on the hydrogen concentration measured by the first hydrogen sensor.

8. 8. The substrate processing apparatus according to claim 7, the exhaust unit includes a capture unit that is provided in the exhaust pipe and captures a target to be captured in the gas flowing through the exhaust pipe, the downstream end of the second air intake pipe is connected to the exhaust pipe at the connection position downstream of the capture portion, The substrate processing apparatus, wherein the first hydrogen sensor is provided in a portion of the exhaust pipe between the connection position and the trapping portion.

9. 5. The substrate processing apparatus according to claim 4, a second hydrogen sensor provided in the exhaust pipe downstream of the connection position, the second hydrogen sensor measuring the hydrogen concentration in the gas; a second flow rate adjusting unit provided in the second air supply pipe and configured to adjust the flow rate of the second gas; Equipped with The control unit controls the second flow rate adjustment unit based on the hydrogen concentration measured by the second hydrogen sensor.

10. 3. The substrate processing apparatus according to claim 2, In the substrate processing apparatus, the pressure in the circulation pipe is positive while the processing liquid is being discharged.

11. A substrate processing method comprising an electrolysis circulation step of circulating a processing liquid used for processing a substrate through a circulation pipe connected to a tank that stores the processing liquid while adjusting the pressure inside the tank to a negative pressure, and electrolyzing sulfuric acid in the processing liquid using an electrolytic cell provided in the circulation pipe to generate electrolyzed sulfuric acid.

12. 12. The substrate processing method according to claim 11, The substrate processing method further comprises a liquid draining step of draining the processing liquid through a drain pipe connected to the tank or the circulation pipe while adjusting the pressure inside the tank to a positive pressure.

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