Gas processing device and gas processing method

Abstract

This gas processing device comprises: a buffer tank to which a gas to be processed is supplied; a first remover that removes impurities from the gas to be processed; and a circulation means that is provided between the buffer tank and the first remover and circulates the gas to be processed. The gas to be processed having a reduced impurity concentration is discharged from the buffer tank.

Description

Gas treatment device and gas production method

[0001] The present invention relates to a gas treatment device and a gas production method.

[0002] Gas treatment devices that remove impurities from gases to be treated are known for reuse or for purifying and releasing the gases. For example, Patent Document 1 (JP-A-2005-102626) discloses a purification device that purifies and reuses laser gas discharged from a laser device. One example of an application of the device disclosed in Patent Document 1 is semiconductor manufacturing. In the photolithography process, which is one step in semiconductor manufacturing, a circuit pattern is formed on a wafer by exposing a wafer coated with a resist. To finely refine the circuit pattern, an excimer laser capable of emitting short-wavelength light is used. Laser gases used in excimer lasers contain expensive rare gases (e.g., neon, xenon, argon, krypton, and helium), and therefore require reuse. Purifying and reusing laser gases can reduce manufacturing costs.

[0003] Patent No. 6770526

[0004] The impurity concentration in the gas to be treated may fluctuate. If a gas with an extremely high impurity concentration is supplied to a remover that removes impurities, it may cause significant damage to the remover's removal ability. In this case, it may be necessary to stop operation of the system and perform maintenance on the remover.

[0005] The object of the present invention is to provide a technology that prevents significant damage to the removal capability of a remover and enables continuous operation even when a gas to be treated with a high impurity concentration is supplied.

[0006] According to the present invention, there is provided a gas treatment device comprising: a buffer tank to which a gas to be treated is supplied; a first remover that removes impurities from the gas to be treated; and a circulation means that circulates the gas to be treated between the buffer tank and the first remover, wherein the gas to be treated with a reduced impurity concentration is discharged from the buffer tank.

[0007] According to the present invention, it is possible to provide a technology that prevents significant damage to the removal capability of the remover and enables continuous operation even when a gas to be treated with a high impurity concentration is supplied.

[0008] Fig. 2 is a block diagram of a laser processing system to which the present invention is applied. Fig. 3 is a block diagram of a gas treatment device according to an embodiment of the present invention. Fig. 4 is an explanatory diagram of operation modes of the gas treatment device of Fig. 2. Fig. 5 is an explanatory diagram of control states of each operation mode of the gas treatment device of Fig. 2. Fig. 6 is a flowchart showing a control example of the gas treatment device of Fig. 2. Fig. 7 is a flowchart showing a control example of the gas treatment device of Fig. 2.

[0009] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0010] <Laser Processing System> Figure 1 is a block diagram of a laser processing system 1 to which the present invention is applied. The laser processing system 1 includes a gas processing device 2 and a laser device 3. The laser device 3 constitutes, for example, a semiconductor manufacturing device that irradiates a wafer with an excimer laser to form fine grooves. Fresh laser gas is supplied to the laser device 3 from a supply source 4 via a pipe 5. Spent laser gas that has been used in the laser device 3 and contains impurities such as water and oxygen can be discharged to the outside via a pipe 9. Fresh laser gas is laser gas that has not been used in the laser device 3 and has an impurity content below a predetermined value. Note that used laser gas purified by the gas processing device 2 described below also has an impurity content and component ratio equivalent to that of fresh laser gas and can be reused.

[0011] The gas processing device 2 is a gas manufacturing device that treats used laser gas discharged from the laser device 3 as the gas to be processed and removes impurities from this used laser gas to purify the laser gas. The gas processing device 2 removes impurities from the used laser gas supplied from the laser device 3 via a pipe 7. The gas processing device 2 supplies the purified laser gas to the laser device 3 via a pipe 8. The laser processing system 1 can circulate the laser gas between the gas processing device 2 and the laser device 3 via the pipes 7 and 8. As a gas manufacturing device, the gas processing device 2 purifies used laser gas and produces new usable laser gas.

[0012] The amount of laser gas circulated between gas processing device 2 and laser device 3, the amount of fresh laser gas supplied from supply source 4 to laser device 3, and the amount of used laser gas discharged from piping 9 are controlled by laser device 3. By circulating and reusing laser gas between gas processing device 2 and laser device 3, the amount of fresh laser gas consumed can be reduced.

[0013] Fresh laser gas can be supplied to the gas processing device 2 from a supply source 4 via a pipe 6. This fresh laser gas is used, for example, when starting up the gas processing device 2. Details will be described later.

[0014] <Control Device> In FIG. 1 , the control device 10 is an electronic circuit that controls the gas treatment device 2. The control device 10 includes a processing unit 11, a memory unit 12, an input / output interface (I / O) 13, and a communication unit 14. The processing unit 11 is a processor, such as a CPU, that executes a program stored in the memory unit 12 to control the gas treatment device 2. The memory unit 12 is a storage device, such as a ROM, RAM, or HDD, that stores various control information in addition to the program executed by the processing unit 11. The I / O 13 is an interface that transmits and receives signals between the processing unit 11 and an external device. The external device is, for example, an actuator, such as a motor or solenoid, or a sensor, that is provided in the gas treatment device 2. The communication unit 14 is a communication device that communicates with a higher-level device or a control device of the laser device 3 via a communication line.

[0015] <Gas Treatment Device> The configuration of the gas treatment device 2 will be described with reference to Fig. 2. Fig. 2 is a block diagram of the gas treatment device 2. Each component of the gas treatment device 2 will be described along the flow direction of the laser gas, which is the gas to be treated. In the following description, the upstream side and downstream side are based on the flow direction of the laser gas.

[0016] The gas processing device 2 includes a pipe 2a connected to a pipe 7. A solenoid valve SV1 is provided in the pipe 2a. The solenoid valve SV1 switches the introduction of laser gas supplied from the laser device 3 via the pipe 7 into the gas processing device 2. When the solenoid valve SV1 is open, the laser gas is introduced, and when it is closed, the laser gas is not introduced. The impurity concentration of the introduced laser gas is, for example, 1000 ppm or more. The laser gas that has passed through the solenoid valve SV1 flows into the tank T1 via the pipe 2a. The tank T1 is maintained at a negative pressure (for example, 0.05 to 0.098 MPa) by a pump P1 on the pipe 2a.

[0017] Tank T1 accumulates laser gas. Even if used laser gas discharged from laser device 3 is intermittently supplied to gas processing device 2, storing laser gas in tank T1 allows for stable delivery of laser gas downstream from tank T1. Tank T1 is connected to pump P1 via solenoid valve SV2. When solenoid valve SV2 is open, tank T1 and pump P1 communicate with each other via pipe 2a, and when solenoid valve SV2 is closed, tank T1 and pump P1 are disconnected from each other.

[0018] Pump P1 is a supply pump that supplies laser gas to tank T2 connected to the end of pipe 2a. When solenoid valve SV2 is opened and pump P1 is operated, used laser gas stored in tank T1 is supplied to tank T2 via pipe 2a. Tank T2 is a buffer tank that stores laser gas. Tank T2 contains a mixture of used laser gas and laser gas from which impurities have been removed by remover 20. Because the used laser gas is diluted in tank T2, it is possible to prevent laser gas with an extremely high impurity concentration from being directly supplied to remover 20.

[0019] Tank T2 is maintained at a slightly positive pressure (e.g., 0.1 to 0.2 MPa) higher than atmospheric pressure by pumps P1 to P3. The volume of tank T2 is, for example, at least equal to or greater than that of tank T1, and the larger the volume, the greater the dilution effect of used laser gas. Tank T2 is connected to pipe 6 via solenoid valve SV14. When solenoid valve SV14 is controlled to be open, fresh laser gas can be supplied to tank T2 from supply source 4.

[0020] The remover 20 is an automatic regenerating purifier that removes impurities from the laser gas. The remover 20 alternates between two filters F1 and F2 using a switch SW. The filters F1 and F2 each include a physical filter that captures dust and other contaminants in the laser gas and an adsorbent that adsorbs the impurities in the laser gas. The switch SW connects one of the filters F1 and F2 to a supply pipe 211 and the other to a supply source 22 via a flow control valve FV2. The supply source 22 supplies the remover 20 with cleaning gas that cleans the filters F1 and F2. The cleaning gas removes impurities and other contaminants adhering to the filters F1 and F2, regenerating them. A pump P4 is connected to the remover 20. The pump P4 is, for example, a scroll pump, and suctions and removes the cleaning gas remaining in the filters F1 and F2.

[0021] The circulation unit 21 circulates the laser gas between the tank T2 and the remover 20. Repeatedly passing the laser gas in the tank T2 through the remover 20 improves the impurity removal effect and reduces the impurity concentration of the laser gas in the tank T2. The circulation unit 21 includes a supply pipe 211, a return pipe 212, and a pump P3. The supply pipe 211 is connected to the tank T2 and the remover 20 and is a pipe for supplying the laser gas from the tank T2 to the remover 20. The return pipe 212 is connected to the tank T2 and the remover 20 and is a pipe for supplying the laser gas from the remover 20 to the tank T2.

[0022] Pump P3 is a circulation pump that is provided in supply pipe 211 and pressure-feeds laser gas from tank T2 to remover 20. Pump P3 may also be provided in return pipe 212. In this case, pump P3 pressure-feeds laser gas from remover 20 to tank T2. Pump P3 may also be provided in both supply pipe 211 and return pipe 212.

[0023] The concentration sensor SR detects the impurity concentration of the laser gas in the tank T2. In this embodiment, the concentration sensor SR is provided in the pipe 23 branching off from the pipe 211. The pipe 23 is connected to the pipe between the solenoid valve SV2 and the pump P1. The laser gas that passes through the pipe 23 is returned to the tank T2 via the pump P1. The pipe 23 is provided with a flow sensor FM and a solenoid valve SV4. When detecting the impurity concentration of the laser gas in the tank T2, the solenoid valve SV4 is controlled to be open, which allows the laser gas in the tank T2 to flow through the pipe 23 and detect its impurity concentration with the concentration sensor SR. When not detecting the impurity concentration of the laser gas in the tank T2, the solenoid valve SV4 is controlled to be closed. Note that the location of the concentration sensor SR is not limited to this. For example, the concentration sensor SR may be provided in the tank T2.

[0024] Pump P2 is a discharge pump connected to tank T2 via pipe 2b and discharges laser gas from tank T2. When pump P2 is operated, used laser gas stored in tank T2 is discharged via pipe 2b to tank T3. Tank T3 is maintained at a positive pressure (e.g., 0.76 to 0.95 MPa) by pump P2. By removing impurities using remover 20, laser gas with an impurity concentration reduced to, for example, 10 ppm or less is accumulated in tank T3. Pipe 2c is connected downstream of tank T3, and pipe 2c is provided with a flow control valve FV1, a solenoid valve SV3, and a mass flow controller MFC1. Mass flow controller MFC1 controls the flow rate of laser gas supplied to remover 24.

[0025] The remover 24 is an in-line purifier that removes impurities from the laser gas. The remover 24 includes, for example, an adsorbent that adsorbs impurities. The remover 24 reduces the impurity concentration of the laser gas to, for example, 10 ppb or less. The laser gas from which the impurities have been removed by the remover 24 is supplied to the getter 25. The getter 25 includes a gettering material and removes inert impurities such as CF4. Here, the impurity concentration of the laser gas is reduced to, for example, 1 ppb or less.

[0026] Downstream of getter 25, pipe 2c branches into two, and the branched pipes are connected to solenoid valves SV51 and SV52, respectively. Laser gas discharged from getter 25 is allocated to and stored in tank T41 or T42 depending on the open / close states of solenoid valves SV51 and SV52. Analysis unit 26 and mixing unit 27 are provided downstream of tanks T41 and T42, and laser gas in tanks T41 and T42 is supplied to analysis unit 26 or mixing unit 27 by solenoid valves SV61 to SV64 via pipe 2d, which branches into multiple branches. Laser gas in tank T41 is analyzed by analysis unit 26, and while the laser gas in tank T41 is adjusted by mixing unit 27 based on the analysis results, laser gas is stored in tank T42. Conversely, the laser gas in tank T42 is analyzed by analysis unit 26, and while the laser gas in tank T42 is adjusted by mixing unit 27 based on the analysis results, the laser gas is accumulated in tank T41.

[0027] Analysis unit 26 is a device that analyzes the components of the laser gas. Mixing unit 27 is a device that mixes the laser gas with the gas components that make up the laser gas based on the analysis results of analysis unit 26. By analyzing the components of the laser gas stored in tank T41 or T42 and replenishing any missing components before supplying the laser gas to be reused to laser device 3, a high-quality reused gas can be produced.

[0028] The analysis unit 26 includes a mass analyzer 261 connected to the pipe 2d. The laser gas in the tank T41 or T42 is supplied to the mass analyzer 261 via a flow control valve FV3 on the pipe 2d. The mass analyzer 261 analyzes the components of the laser gas. A pump P5 is connected to the mass analyzer 261. The pump P5 is, for example, a scroll pump. By operating the pump P2, the laser gas to be analyzed is introduced from the tank T41 or T42 into the mass analyzer 261.

[0029] Mass analyzer 261 is configured to be able to introduce gases for analysis from supply sources 263 and 264. The gas from supply source 263 is a gas for background measurement, and is supplied to mass analyzer 261 via purifier 262, flow control valve FV5, and solenoid valve SV7 to measure the background. The gas from supply source 264 is a gas for calibration, and is supplied to mass analyzer 261 via flow control valve FV6 and solenoid valve SV8 when calibrating mass analyzer 261.

[0030] The mixing unit 27 includes a gas mixer 271 connected to pipe 2d. Laser gas in tank T41 or T42 is supplied to the gas mixer 271 via flow control valve FV4 and mass flow controller MFC2 on pipe 2d. The gas mixer 271 adjusts the laser gas components so that the components in the laser gas have a specified concentration ratio based on the component analysis results of mass spectrometer 261. Gases for mixing (e.g., argon gas and xenon gas) are supplied to the gas mixer 271 from supply sources 272 and 273. Gas from supply source 272 is supplied to the gas mixer 271 via flow control valve FV7, mass flow controller MFC3, and solenoid valve SV9. Gas from supply source 273 is supplied to the gas mixer 271 via flow control valve FV8, mass flow controller MFC4, and solenoid valve SV10. The laser gas whose components have been adjusted in the gas mixer 271 is accumulated in the tank T5 via the pipe 2d.

[0031] The laser gas stored in tank T5 is of such quality that it can be reused in laser device 3. Pipe 2e, which branches into multiple branches, is connected to tank T5 on its downstream side. Supply unit 28 is provided on pipe 2e. Supply unit 28 supplies the laser gas in tank T5 to laser device 3. Supply unit 28 has pump P6 on pipe 2e. Pump P6 pressure-feeds the laser gas in tank T5 to tank T62 via pipe 2e. Solenoid valve SV13 is provided between tank T62 and pipe 8. When solenoid valve SV13 is controlled to be open, laser gas is supplied from tank T62 to laser device 3 via pipe 8.

[0032] The supply unit 28 includes a tank T61 connected to a pipe 2e. The tank T61 functions as a pressure buffer that adjusts the pressure of the tank 62, and the tank T62 is maintained at a positive pressure (for example, 0.61 to 0.95 MPa). The tanks T61 and T62 are connected via solenoid valves SV11 and SV12 and a flow control valve FV9 on the pipe 2e.

[0033] The pressure of the laser gas supplied to the laser device 3 is adjusted by controlling the operation of the pump P6 and the opening and closing of the solenoid valves SV11 and SV12. For example, when the pressure of the tank T62 increases above a threshold, the gas in the tank T62 is released to the tank T61 via the flow control valve FV9. Conversely, when the pressure of the tank T62 drops below the threshold, the solenoid valve SV11 is opened and the gas in the tank T61 is sent to the tank T62, thereby maintaining the pressure in the tank T62.

[0034] With the above configuration, the laser processing system 1 circulates the laser gas between the gas treatment device 2 and the laser device 3, and the laser gas can be purified and reused in the gas treatment device 2. This reduces the consumption of fresh laser gas, thereby reducing manufacturing costs. By circulating the laser gas between the remover 20 and the tank T2, even if laser gas with a high impurity concentration is supplied from the laser device 3 to the gas treatment device 2, the laser gas is diluted in the tank T2. This prevents laser gas with an extremely high impurity concentration from being supplied to the remover 20, which would severely damage the removal ability of the remover 20, and extends the maintenance cycle of the filters F1 and F2, enabling continuous operation.

[0035] <Control of laser gas supply to remover> In this embodiment, by diluting the impurity concentration of the laser gas in tank T2 as described above, it is possible to prevent laser gas with an extremely high impurity concentration from being supplied to remover 20. However, if laser gas with a high impurity concentration is continuously supplied to tank T2, or if laser gas with an extremely high impurity concentration is supplied to tank T2, the effect of diluting the impurity concentration in tank T2 will decrease. Therefore, with regard to the removal of impurities in remover 20, gas processing device 2 has two operating modes.

[0036] FIG. 3 is an explanatory diagram of the operation, and FIG. 4 shows the control state of each operation mode (open / closed states of the solenoid valves SV1 to SV3 and operating states of the pumps P1 to P3).

[0037] State ST1 in FIG. 3 shows the operating state in mode 1. Mode 1 is selected under normal circumstances (when the impurity concentration of the laser gas in tank T2 is below a threshold value (e.g., 10 ppm)). The impurity concentration may be determined based on the highest impurity content detected by concentration sensor SR. In mode 1, solenoid valves SV1 to SV3 are controlled to be open, and pumps P1 to P3 are controlled to be ON (operated) (FIG. 4). In mode 1, the following operations are performed in parallel: a supply operation in which used laser gas is supplied from tank T1 to tank T2; a circulation operation in which laser gas is circulated between tank T2 and remover 20; and a discharge operation in which laser gas with a reduced impurity concentration is discharged from tank T2 to tank T3 and then supplied to remover 24.

[0038] State ST2 in Figure 3 shows the operating state in mode 2. Mode 2 is selected in an emergency (when the impurity concentration of the laser gas in tank T2 exceeds a threshold). In mode 2, solenoid valves SV1 to SV3 are controlled to be closed, pumps P1 and P2 are controlled to be OFF (stopped), and pump P3 is controlled to be ON (operated) (Figure 4). In mode 2, circulation operation is performed, and supply operation and discharge operation are not performed. That is, in mode 2, the supply of used laser gas from tank T1 to tank T2 is stopped. In mode 2, the discharge of laser gas from tank T2 to tank T3 is also stopped, and solenoid valve SV3 is controlled to be closed, thereby stopping the supply of laser gas to remover 24. Mode 2 continues the circulation of laser gas between tank T2 and remover 20 while preventing laser gas with a high impurity concentration from being supplied to remover 24. The impurity concentration of the laser gas in tank T2 decreases over time, making it possible to return to mode 1.

[0039] In this embodiment, when the impurity concentration of the laser gas in tank T2 becomes high, the introduction of new used laser gas into tank T2 is prohibited, and the discharge of laser gas downstream from tank T2 is also prohibited. This prevents laser gas with a high impurity concentration from directly hitting remover 20 or remover 24, which would require the operation of gas processing device 2 to be stopped for maintenance, etc. Furthermore, since the circulation of laser gas continues between tank T2 and remover 20, it will eventually be possible to return to mode 1, and the circulation of laser gas between laser device 3 and gas processing device 2 can continue, or can be restored after a temporary stop. Therefore, the continuous operating performance of system 1 can be improved.

[0040] The above-mentioned operating modes are merely examples, and it is possible to operate in various operating modes by controlling the solenoid valves SV1 to SV3 and the pumps P1 to P3. For example, there may be a mode (referred to as mode 3) in which the solenoid valves SV1 and SV2 are open, the solenoid valve SV3 is closed, the pumps P1 and P2 are OFF, and the pump P2 is ON. In mode 3, the supply operation and the circulation operation are performed, but the discharge operation is not performed. Mode 3 may be performed when the amount of laser gas accumulated in tank T2 is low (or is expected to decrease in the future).

[0041] <Example of Control by the Control Device> A description will be given of an example of processing by the control device 10 relating to the supply control of laser gas to the remover 20. Figures 5 to 7 are flowcharts showing an example of processing executed by the processing unit 11.

[0042] Assume that the entire laser processing system 1 is in the start-up or early stage of operation. In S1 of Fig. 5, the start-up operation of the gas treatment device 2 is performed. As a prerequisite for circulating the laser gas between the tank T2 and the remover 20, it is desirable that the laser gas stored in the tank T2 has a relatively low impurity concentration.

[0043] Therefore, as an example of a process included in the startup operation, fresh laser gas can be introduced into tank T2. For example, pump P4 is used to evacuate tank T2 while pumps P1 to P3 are stopped. When solenoid valve SV14 is controlled to open, fresh laser gas can be drawn into tank T2 from supply source 4. Then, solenoid valve SV14 is controlled to close, and the evacuation by pump P4 is terminated. By introducing fresh laser gas into tank T2 in advance in this way, it is possible to promote the dilution of the used laser gas that is initially introduced into tank T2 when laser device 3 starts operating, and it is possible to prevent laser gas with a high impurity concentration from being introduced into remover 20 (or remover 24).

[0044] As another example of processing included in the startup operation, the processing example of FIG. 6 may be executed at the stage when used laser gas begins to be supplied to the gas processing device 2 after the laser device 3 has started operating. In S11, the solenoid valves SV1 and SV2 are controlled to be open, and the solenoid valve SV3 is controlled to be closed. The pumps P1 and P3 are turned ON (operated), and the pump P2 is turned OFF (stopped). In other words, the above-mentioned mode 3 is executed. As a result, used laser gas is supplied from the tank T1 to the tank T2, and the laser gas is circulated between the tank T2 and the remover 20. By performing the supply operation and the circulation operation at the initial stage of operation of the laser device 3, the laser gas from which impurities have been removed can be accumulated in the tank T2, and laser gas with a high impurity concentration can be prevented from being introduced into the remover 20 (or the remover 24).

[0045] In S12, the detection result of the impurity concentration of the laser gas in tank T2 by concentration sensor SR is acquired. In S13, it is determined whether the detection result (impurity concentration) acquired in S12 is equal to or less than a threshold value, and if it exceeds the threshold value, the process returns to S12 and the same processing is repeated. If the detection result (impurity concentration) is equal to or less than the threshold value, it is considered that preparation is complete and the start-up operation is terminated.

[0046] 5, in S2, the solenoid valves SV1 to SV3 are controlled to be open and the pumps P1 to P3 are controlled to be ON (operated) to start operation in mode 1. When predetermined stop conditions are met, in S3, a stop operation of the gas treatment device 2 is performed. The solenoid valves SV1 to SV3 are controlled to be closed and the pumps P1 to P3 are controlled to be OFF (stopped).

[0047] Fig. 7 shows an example of processing after the processing of Fig. 5. Here, control is performed regarding switching between mode 1 and mode 2. This control is started when the operating state of gas processing device 2 changes to mode 1 (execution of S2), and is repeatedly performed until purification of laser gas by gas processing device 2 is completed (S3).

[0048] In S21, the detection result of the impurity concentration of the laser gas in tank T2 by concentration sensor SR is acquired. In S22, it is determined whether the detection result (impurity concentration) acquired in S21 is equal to or less than a threshold value, and if it is equal to or less than the threshold value, the process returns to S21 and repeats the same processing to continue mode 1. If the detection result (impurity concentration) exceeds the threshold value, the process of S23 is performed.

[0049] In S23, to operate in mode 2, the solenoid valves SV1 to SV3 are controlled to be closed, the pumps P1 and P2 are controlled to be OFF (stopped), and the pump P3 is controlled to be ON (operated).

[0050] In S24, the detection result of the impurity concentration of the laser gas in tank T2 by concentration sensor SR is obtained. In S25, it is determined whether the detection result (impurity concentration) obtained in S24 is equal to or less than a threshold value, and if it exceeds the threshold value, the process returns to S24 and the same processing is repeated. If the detection result (impurity concentration) is equal to or less than the threshold value, the process of S26 is executed. In S26, in order to resume operation in mode 1, solenoid valves SV1 to SV3 are controlled to open, and pumps P1 to P3 are controlled to be ON (operated).

[0051] Although the above embodiment illustrates an example in which the present invention is applied to the treatment of used laser gas, the present invention can be applied to the treatment of various gases. The treatment may include purification as well as purification for reuse.

[0052] Although the embodiments of the invention have been described above, the invention is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the invention.

Claims

1. A gas treatment device comprising: a buffer tank to which a gas to be treated is supplied; a first remover for removing impurities from the gas to be treated; and a circulation means for circulating the gas to be treated between the buffer tank and the first remover, wherein the gas to be treated with a reduced impurity concentration is discharged from the buffer tank.

2. A gas treatment device according to claim 1, further comprising a second remover for removing impurities from the gas to be treated discharged from the buffer tank.

3. A gas treatment device according to claim 1, comprising: an exhaust means for exhausting the gas to be treated from the buffer tank; a sensor for detecting the impurity concentration of the gas to be treated in the buffer tank; and a control means for controlling the exhaust means based on the detection result of the sensor.

4. The gas treatment device according to claim 1, wherein the gas to be treated is a laser gas discharged from a laser device.

5. A gas processing device according to claim 4, characterized in that said gas processing device is a gas production device which produces laser gas to be supplied to said laser device by reusing said laser gas.

6. A gas processing apparatus as claimed in claim 5, comprising: an analysis means for analyzing the components of the laser gas before supplying the laser gas to the laser apparatus; and a mixing means for mixing the laser gas with gases of the components that make up the laser gas based on the analysis results of the analysis means before supplying the laser gas to the laser apparatus.

7. A gas treatment device according to claim 4, further comprising a supply means for supplying the laser gas to the laser device, and wherein the laser gas is circulated between the gas treatment device and the laser device.

8. A gas treatment device as claimed in claim 1, characterized in that the circulation means comprises: a supply pipe connected to the buffer tank and the first remover for supplying the gas to be treated from the buffer tank to the first remover; a return pipe connected to the buffer tank and the first remover for supplying the gas to be treated from the first remover to the buffer tank; and a circulation pump provided on at least one of the supply pipe or the return pipe for pressurizing the gas to be treated.

9. A gas treatment device as described in claim 3, further comprising a supply means for supplying the gas to be treated to the buffer tank while the gas to be treated is circulated by the circulation means, and wherein the control means operates the supply means and the discharge means when the detection result of the sensor indicates a concentration below a threshold value, and stops the supply means and the discharge means when the detection result of the sensor indicates a concentration above the threshold value.

10. A gas treatment device according to claim 1, characterized in that the buffer tank stores in advance a gas having a lower impurity concentration than the gas to be treated that is supplied to the buffer tank.

11. A gas production method comprising: a supply process for supplying a gas to be treated to a buffer tank; a circulation process for circulating the gas to be treated between the buffer tank and a first remover for removing impurities from the gas to be treated; and a discharge process for discharging the gas to be treated, with a reduced impurity concentration, from the buffer tank.

12. The gas production method according to claim 11, wherein the supplying step is carried out during the circulating step.

13. A gas production method according to claim 11, further comprising a step of supplying the gas to be treated discharged in the discharge step to a second remover which further removes impurities from the gas to be treated.

14. A gas production method as claimed in claim 11, comprising: a detection step for detecting an impurity concentration of the gas to be treated in the buffer tank; and a determination step for determining whether or not to execute the discharge step based on the detection result of the detection step.

15. A gas production method as claimed in claim 11, characterized in that the gas to be treated is laser gas exhausted from a laser device, and the gas production method is a method for producing laser gas to be supplied to the laser device by reusing the laser gas.