Gas purification apparatus and gas purification method

Abstract

The present invention addresses the problem of providing a gas purification apparatus (100) capable of purifying, with high controllability, a laser gas for use in a laser beam generation device (1).　The gas purification apparatus (100) purifies a recovery gas recovered from the laser beam generation device (1) that uses a laser gas, and supplies the purified gas to the laser beam generation device (1). The gas purification apparatus is characterized by comprising: a mass flow controller (MFC) that controls the flow rate of a recovery gas; a constant volume supply device (15) that is provided downstream from the mass flow controller (MFC) and that supplies an additive gas; and a purifier (16) that is provided downstream from the constant volume supply device (15).

Description

Gas purification device and gas purification method

[0001] The present invention relates to a gas purification device and a gas purification method for a laser device.

[0002] Laser light generating devices such as excimer laser devices are used in lithography processes in the manufacture of semiconductor devices. Repeated use of an excimer laser device can result in the generation of impurities (e.g., fluorine carbides) in the laser gas within the laser chamber, making it impossible to obtain the desired laser light output. In such cases, the laser gas must be replaced. However, because laser gas contains expensive gases, devices that purify and reuse the laser gas are known.

[0003] Japanese Patent Application Publication No. 11-54851 WO2015 / 076415

[0004] Laser gas contains a component (e.g., xenon) at a very small concentration of a few ppm to stabilize the discharge. The concentration of this component may fall below a predetermined concentration range, making it necessary to add (replenish) it. However, controlling such a small concentration is difficult.

[0005] In view of the above problems, an object of the present invention is to provide a gas purification device that can purify laser gas used in a laser light generating device with good controllability.

[0006] The gas purification device according to the present invention is a gas purification device that purifies recovered gas recovered from a laser light generation device that uses laser gas and supplies the purified gas to the laser light generation device, and is characterized by comprising: a flow rate control device that controls the flow rate of the recovered gas; a constant volume supply device that is provided downstream of the flow rate control device and that supplies an additive gas; and a purifier that is provided downstream of the constant volume supply device.

[0007] By configuring the gas purification apparatus in this manner, it is possible to provide a gas purification apparatus that purifies with good controllability.

[0008] In the gas purification device according to the present invention having the above configuration, the constant volume supply device may supply the additive gas discretely.

[0009] By using a gas purification device with such a configuration, the amount of additive gas to be added can be controlled by the number of times the additive gas is ejected.

[0010] Furthermore, in the gas purification apparatus according to the present invention, in the above configuration, the constant-volume supply device may have a constant-volume section, a first valve, and a second valve, and the first valve and the second valve may be located at both ends of the constant-volume section.

[0011] By using a constant volume supply device having such a configuration, the amount of added gas can be accurately determined by the volume of the constant volume section which is determined geometrically.

[0012] Furthermore, in the above-described configuration, the gas purification device according to the present invention may further include a first storage tank provided upstream of the flow control device and a second storage tank provided downstream of the purifier, and the first storage tank and the second storage tank may be connected so as to be communicable or disconnectable.

[0013] By using a gas purification device with such a configuration, it becomes possible to purify the recovered gas again, and the quality of the recovered gas can be further assured.

[0014] Moreover, in the gas purification device according to the present invention having the above configuration, the gas purification device may further include a gas analyzer, which analyzes the components of the gas in the first storage tank.

[0015] By using a gas purification device with such a configuration, it is possible to control the quality of the recovered gas.

[0016] Furthermore, the method for purifying laser gas according to the present invention is characterized by comprising: a recovery step of recovering laser gas from a laser light generating device; a recovered gas analysis step of analyzing the recovered gas and determining whether or not it is necessary to add an additive gas; an addition step of adding the additive gas using a constant volume supply device if it is determined in the recovered gas analysis step that it is necessary to add the additive gas; a purification step of purifying the recovered gas; a purified gas analysis step of analyzing the components of the recovered gas purified in the purification step and determining whether or not it is necessary to re-purify it; and a re-purification step of carrying out the purification step if it is determined in the purified gas analysis step that it is necessary to re-purify it.

[0017] By using a gas purification method having such a configuration, it is possible to accurately control the components of the recovered gas and improve quality control and assurance.

[0018] According to the present invention, it is possible to provide a gas purification device that can purify laser gas used in a laser light generating device with good controllability.

[0019] FIG. 1 schematically illustrates the main components of a gas purification device 100. FIG. 2 illustrates the purification flow of gas recovered from a laser chamber. FIG. 3 is a cross-sectional view illustrating the main components of a gas supply control device 15. FIG. 3(A) illustrates the connections of the gas supply control device 15 in the gas purification device 100, and FIGS. 3(B), 3(C), and 3(D) are cross-sectional views illustrating the operation of the gas supply control device 15. FIG. 4 illustrates non-limiting examples of the configuration of the purifier 16. FIG. 4(A) illustrates an example of a configuration including a first purifier 16a, a second purifier 16b, and a third purifier 16c, and FIG. 4(B) illustrates an example of a configuration including a first purifier 16a, a second purifier 16b, a third purifier 16c, and a fourth purifier 16d.

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are not intended to limit the scope of the present invention. Furthermore, the same or similar components will be designated by the same reference numerals, and their description may be omitted.

[0021] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," "same," "vertical," and "horizontal," as well as values ​​of length and angle (orientation), are not to be bound by strict meanings but are to be interpreted to include a range within which similar functions can be expected.

[0022] (Embodiment 1) Hereinafter, an example of an embodiment of a gas purification device 100 will be described with reference to the drawings. FIG. 1 schematically shows the main components of the gas purification device 100. As shown in FIG. 1, the gas purification device 100 is connected to a laser chamber of an excimer laser light generator 1 by a pipe 10 (recovery pipe) and a pipe 20 (supply pipe). The pipe 10 and the pipe 20 are connected by a pipe 30 (main pipe). Note that the number of excimer laser light generators 1 connected to one gas purification device 100 is not necessarily limited to one, and multiple excimer laser light generators 1 may be connected to one gas purification device.

[0023] The gas purification device 100 includes, in order from the piping 10 side, a first tank 2, a first pump 3, a second tank 4, a second pump 5, a third tank 6, a fourth tank 7, a third pump 8, and a fifth tank 9. A purifier 16 (impurity removal device) is provided between the third tank 6 and the fourth tank 7. The purifier 16 removes impurities (e.g., CF) contained in the laser gas. ４ These components are connected by piping 30.

[0024] The first tank 2 is connected to the laser chamber via a pipe 10, and the fifth tank 9 is connected to the laser chamber via a pipe 20. The laser gas used to generate laser light is recovered from the laser chamber of the laser light generator 1 to the gas purification device 100 via the pipe 10, and after purification processing, is returned from the gas purification device 100 to the laser chamber via the pipe 20. Hereinafter, the pipe 10 side may be referred to as the upstream side, and the pipe 20 side may be referred to as the downstream side.

[0025] The laser light generating device 1 can be a known device and includes a laser chamber filled with a laser gas. Known laser gases are used as the laser gas, and non-limiting examples include neon (Ne) and halogen gas (F ２ The filling pressure is usually about 200 to 600 kPa. The component ratio (mixing ratio) of the laser gas can be any known ratio.

[0026] The gas purification apparatus 100 includes a control device 12, which controls the opening and closing of each valve provided in the piping and can also control the operation and stopping of the first pump 3, the second pump 5, and the third pump 8 based on a predetermined pressure. The first, second, and third pumps may be configured to operate autonomously while detecting pressure without relying on the control device 12, or may be configured to operate autonomously and be controlled by the control device 12 simultaneously. Each tank may have a pressure gauge, which may measure the pressure of the gas in that tank. The control device 12 can input the values ​​of each pressure gauge and monitor the pressure of the gas in that tank. Furthermore, the measurement results of the gas analyzer 11 provided in the gas purification apparatus 100 are input to the control device 12.

[0027] The following is a detailed description of the operation of purifying laser gas by the gas purifying device 100. Figure 2 shows the purification flow of gas recovered from the laser chamber.

[0028] When the control device 12 receives a request to purify the gas discharged from the laser light generating device 1, it executes the purification flow described below. The control device 12 can communicate with each valve and each pump by wireless or wired communication means, and in each step, the opening and closing control of each valve and the driving and stopping control of each pump are executed by the control device 12. In the following description, valves that are not specifically mentioned are in a closed state.

[0029] Step 1 (Gas Recovery Step) Valves V1 and V2 located upstream and downstream of first tank 2, and valve V3 located downstream of first pump 3, are opened, and gas (hereinafter referred to as recovered gas) recovered from laser light generator 1 (laser chamber) is introduced into first tank 2 (recovery tank) via piping 10 (recovery piping), and then pressure-fed to second tank 4 (first storage tank) by first pump 3. When the recovered gas stored in second tank 4 reaches a predetermined pressure (storage pressure), for example, but not limited to, a pressure of 100 kPa or more and 400 kPa or less, valve V3 is closed, first pump 3 is stopped, and the process proceeds to Step 2.

[0030] Step 2 (Gas Pressurization Step) Valve V3 is closed, and valves V4 and V5, which are upstream and downstream of the second pump 5, are opened. The recovered gas in the second tank 4 is pressurized by the second pump 5 to the third tank 6 (pressurization tank) and pressurized in the third tank 6. A pressure gauge G6 is provided in the third tank 6, and the pressure gauge G6 measures the gas pressure in the third tank 6. The control device 12 acquires the measurement value P6 of the pressure gauge G6. If the control device 12 determines that the pressure P6 has reached a predetermined threshold Pt1 (e.g., 600 kPa to 900 kPa) (P6≧Pt1), the control device 12 closes valve V5, stops the second pump 5, and proceeds to step 3. Note that if the increase in pressure in the third tank 6 saturates and does not reach the predetermined threshold, the process returns to step 1. The control device 12 repeats steps 1 and 2 until the pressure in the third tank 6 reaches the predetermined threshold. Note that a pump capable of operating over a wide pressure range may be used as the second pump 5, thereby eliminating the need for the first tank 2, the first pump 3, and the valves V1 and V2. In this case, a step (gas recovery and pressurization step) that combines step 1 and step 2 may be executed. Specifically, the valves V3, V4, and V5 may be opened, and the valve V6 may be closed, and the recovered gas may be pumped to the third tank 6 by the second pump 5. When the control device 12 determines that the measured gas pressure P6 in the third tank 6 has reached the threshold value Pt1 (P6 or greater Pt), the control device 12 closes the valves V3 and V4, stops the second pump 5, and proceeds to step 3.

[0031] Step 3 (Recovered Gas Analysis Step) Valve V5 and valve V6 downstream of the third tank 6 are closed, and valve VA1 installed in pipe A1 connecting the third tank 6 to the gas analyzer 11 is opened. The gas analyzer 11 measures the concentrations of the components of the recovered gas in the third tank 6. The output of the gas analyzer 11 is output to the control device 12. A mass spectrometer, for example, can be used as the gas analyzer 11. For each measured component, the control device 12 determines whether the concentration of the component constituting the laser gas (e.g., neon, krypton, xenon, argon, etc.) is within a predetermined concentration range and determines whether or not an additive gas needs to be added. For components whose concentrations are lower than the predetermined concentration range, the control device 12 determines that addition (replenishment) is necessary, calculates the amount of additive gas to be added (doping amount) so that the component falls within the predetermined concentration range, and proceeds to step 4. For example, the gas analyzer 11 measures the xenon concentration of the recovered gas, and if it is determined that the xenon concentration is lower than a predetermined concentration, the control device 12 determines that xenon addition (replenishment) is necessary and calculates the amount of xenon to be added (doped) to the recovered gas so that the xenon concentration falls within a predetermined concentration range. Then, the process proceeds to step 4. If it is determined that addition of all of the constituent components is unnecessary, the process proceeds to step 5.

[0032] Step 4 (Addition Process) With valve V5 and valve V8 downstream of the fourth tank 7 (second storage tank) in a closed state, and valve V6 and valve V7 upstream of the fourth tank 7 in an open state to connect the third tank 6 and the fourth tank 7, the recovered gas accumulated in the third tank 6 is allowed to flow into the downstream pipe 30. The recovered gas is adjusted to a predetermined pressure (PG1) by the pressure regulator RG1, and the flow rate is controlled by a flow rate control device (mass flow controller) MFC provided downstream of the pressure regulator RG1.

[0033] The gas cylinder 14 filled with the additive gas is connected to a pipe 31 (addition pipe), which is connected to a pipe 30 downstream of the flow rate control device MFC. The pipe 31 is provided with a pressure regulator RG2 (RG2a, RG2b) and a gas supply control device 15 (constant-volume supply device) described later. The additive gas in the gas cylinder 14 is adjusted to a predetermined pressure (PG2) by the pressure regulator RG2 and flows into the gas supply control device 15. The control device 12 controls the gas supply control device 15 based on the calculated addition amount to cause the additive gas (e.g., xenon, argon, etc.) to flow from the gas cylinder 14 to the pipe 31. The recovery gas and the additive gas merge at the connection point between the pipe 31 and the pipe 30. Note that, to add a trace concentration of a component, such as xenon, xenon gas diluted with neon (a mixed gas of neon and xenon) may be used.

[0034] In addition, when supplying multiple types of additive gases, for example, two types, the gas cylinder 14 may have a first gas cylinder 14a and a second gas cylinder 14b, and pipes 31a and 31b may be connected to the first gas cylinder 14a and the second gas cylinder 14b, respectively, and pressure regulators RG2a and RG2b and gas supply control devices 15a and 15b may be provided on the pipes 31a and 31b, respectively, to control the amount of each additive gas added. Figure 1 shows an example having the first gas cylinder 14a and the second gas cylinder 14b.

[0035] As will be described later, the gas supply control device 15 is a constant-volume supply device that controls the volume of the additive gas required by causing a predetermined volume of additive gas to flow into the pipe 30 via the pipe 31 with each ejection operation, and by performing the ejection operation a predetermined number of times. In other words, the gas supply control device 15 discretely supplies a predetermined volume of gas.

[0036] The volume of the recovered gas flowing through the pipe 30 per unit time is determined by the flow rate control device MFC, so the control device 12 can calculate the amount of added gas (replenishment amount) per unit time and the number of ejections per unit time, thereby allowing the necessary amount of added gas to be added to the recovered gas.

[0037] The pipe 30 may have a mixer 13 downstream of the communicating point with the pipe 31. In the mixer 13, the uniformity of the mixing of the additive gas and the recovered gas is improved.

[0038] The mixed gas to which the additive gas has been added is subjected to the purification process of step 5. Since the flowing recovered gas is subjected to the processes of steps 4 and 5 consecutively, the gas purification apparatus 100 proceeds with steps 4 and 5 simultaneously.

[0039] Preferably, the temperature may be kept constant by covering the entire system with a housing 40. In particular, by maintaining the temperatures of the flow rate control device MFC and the gas supply control device 15 at the same temperature, more stable control of the addition amount becomes possible.

[0040] Step 5 (Purification Step) Valves V6 and V7 are opened, and the mixed gas of the recovered gas and the added gas is introduced to the purifier 16 via the pipe 30 and purified by the purifier 16. If it is determined in step 3 that the added gas is not necessary, the recovered gas, not the mixed gas, is purified by the purifier 16. Hereinafter, the term "mixed gas" refers to the "recovered gas" when it is determined in step 3 that the added gas is not necessary.

[0041] The refiner 16 may include a plurality of refiners, as shown in Fig. 4. Fig. 4 shows non-limiting examples of the configuration of the refiner 16. Fig. 4(A) shows an example of a configuration including a first refiner 16a, a second refiner 16b, and a third refiner 16c, and Fig. 4(B) shows an example of a configuration including a first refiner 16a, a second refiner 16b, a third refiner 16c, and a fourth refiner 16d. For example, in the example shown in Fig. 4(A), the first refiner 16a is a fluorocarbon (CF ４The first purifier 16a is a purifier that removes impurities such as argon, nitrogen, and argon, and the third purifier 16c is a purifier that removes oxygen. The example shown in FIG. 4B further includes a fourth purifier 16d, which is a purifier (getter) that removes impurities that were not completely removed. The configuration shown in FIG. 4A or 4B can be selected depending on the application of the laser gas used, for example, for a KrF laser or an ArF laser. Each purifier can be a known purifier and can be operated under known conditions. The configuration of the purifier 16 is not limited to the above, and any purifier necessary to maintain the quality of the laser gas can be used.

[0042] The mixed gas purified by the purifier 16 is accumulated in the fourth tank 7, and the pressure in the fourth tank 7 increases. Meanwhile, the pressure P6 of the gas in the third tank 6 decreases, and when it becomes equal to or lower than a predetermined threshold value Pt2 (e.g., a value 100 kPa to 200 kPa lower than Pt1) (P6≦Pt2), the valves V6 and V7 close, the purification step ends, and the process proceeds to step 6.

[0043] In addition, since the purifier 16 generally employs a catalyst or adsorbent that comes into contact with the gas to remove impurities from the gas, the uniformity of the mixture of the recovered gas and the additive gas is further improved by passing the mixed gas through the purifier 16. In addition, since the mixed gas is accumulated in the fourth tank 7, the uniformity of the mixture of the recovered gas and the additive gas within the fourth tank 7 is further improved. As described above, the gas supply control device 15 supplies the additive gas discretely, but the purifier 16 and the fourth tank 7 have the effect of further improving the uniformity of the mixture.

[0044] Step 6 (Purified Gas Analysis Step) With valves V7 and V8 closed, valve VA2 on pipe A2 connecting the fourth tank 7 with the gas analyzer 11 is opened, and the recovered gas (mixed gas) accumulated in the fourth tank 7 is subjected to component analysis (impurity analysis) by the gas analyzer 11. The output from the gas analyzer 11 is input to the control device 12, which makes it possible to calculate the concentration of each component and the concentration of other impurities. When the component analysis is complete, valve VA2 is closed.

[0045] The control device 12 compares the measured impurity concentration with the judgment value, and if the impurity concentration is greater than the judgment value, determines that further refinement is necessary, and if the impurity concentration is equal to or less than the judgment value, determines that further refinement is not necessary. If the control device 12 determines that further refinement is necessary, it proceeds to step 7. If the control device 12 determines that further refinement is not necessary, it proceeds to step 8. The judgment value is determined based on the range within which the laser light generating device 1 can operate normally.

[0046] In this way, the purified mixed gas (recovered gas) is stored in the fourth tank 7 and the components are analyzed, thereby enabling quality control of the mixed gas.

[0047] The concentration of each component (additive gas) of the mixed gas may be analyzed (measured) in step 6. If the concentration of the additive gas does not reach the predetermined range, step 7 is executed, and the process may proceed to step 4 for adding the additive gas again, and then proceed to step 5.

[0048] Step 7 (Repurification Step) Valves V3 and V6 are closed, and valves VB, V4, and V5 are open. The recovered gas accumulated in the fourth tank 7 is guided to the second tank 4 via pipe B (bypass pipe), and then pumped to the third tank 6 by the second pump 5. The mixed gas accumulates in the third tank 6. When the pressure P6 of the third tank 6 reaches a predetermined pressure Pt3 (e.g., the same value as Pt1) (P6≧Pt3), the control device 12 closes valves VF, V4, and V5. If it is determined that repurification of the recovered gas is necessary, the fourth tank 7 and the second tank 4 are connected via pipe B in this step 7, allowing the movement of the recovered gas. In other steps, the movement of the recovered gas is blocked by valve VB. Then, the process proceeds to step 5.

[0049] As described above, the fourth tank 7 and the second tank 4 are connected by the pipe B and the valve VB so as to be selectively communicable or disconnected depending on the results of the gas analysis in step 6. Here, "communicable" means that the valve VB is open and allows gas to move, and "disconnected" means that the valve VB is closed and prevents gas from moving.

[0050] Step 8 (Purified Gas Supply Step) If it is determined in step 6 that re-purification is not necessary, the mixed gas stored in the fourth tank 7 is pressure-fed to the fifth tank 9 by the third pump 8 with the valve V10 located downstream of the fifth tank 9 (supply tank) closed and the valves V8 and V9 located upstream and downstream of the third pump 8 open. The mixed gas is stored in the fifth tank 9. When the pressure P9 of the mixed gas in the fifth tank 9 reaches a predetermined pressure Pt4 (e.g., the same as Pt1) (P9 ≧ Pt4), the valves V8 and V9 are closed. Thereafter, the valve V10 is opened, and the mixed gas stored in the fifth tank 9 is supplied to the laser light generator 1 via the second pipe 20 (supply pipe). Note that before opening the valve V10, the components of the mixed gas stored in the fifth tank 9 may be analyzed by the gas analyzer 11. In this case, valves V10 and V9 are closed, and valve VA3 of pipe A3 connecting the fifth tank 9 and gas analyzer 11 is opened, and the components of the mixed gas in the fifth tank 9 are analyzed by the gas analyzer 11. This contributes to quality control and quality assurance of the purified recovered gas.

[0051] By purifying the recovered gas and replenishing it with additive gas through the above steps, the laser gas is recycled, which can contribute to reducing the operating costs of the laser light generating device 1.

[0052] Note that multiple third tanks 6 may be provided and used alternately. For example, two third tanks 6A and 6B may be provided, and steps 1 and 2 may be performed in one third tank 6A, and then steps 3 and subsequent steps may be performed while steps 1 and 2 are performed in the other third tank 6B, and the recovered gas may be accumulated and pressurized in the third tank 6B. After step 10 is completed in one third tank 6A or while step 10 is being performed, steps 3 and subsequent steps may be performed in the other third tank 6B. Alternate use of multiple third tanks 6 can contribute to improving the utilization efficiency of the gas purification device 100.

[0053] Note that multiple purifiers 16 may be provided in parallel and used alternately. For example, the second purifier 16b may be a purifier that adsorbs water, and the third purifier 16c may be a purifier that adsorbs oxygen. Two second purifiers 16b, 16b' and two third purifiers 16c, 16c' may be connected in parallel, and the purification operation and the purifier regeneration operation may be performed alternately in parallel. By purifying the recovered gas using one purifier 16 (e.g., the second purifier 16b and the third purifier 16c) and regenerating the other purifier 16 (e.g., the second purifier 16b' and the third purifier 16c'), the gas purification system 100 can be continuously performed without having to stop operation for the regeneration of the purifiers 16. For example, when the second purifier 16b is a purifier that adsorbs water and is to be regenerated, the second purifier 16b is evacuated using a vacuum pump (not shown) to remove adsorbed materials and the like from the second purifier 16b, and then laser gas is supplied from a gas cylinder (not shown) into the second purifier 16b to fill the second purifier 16b. For example, in the piping 30 connected to the second purifier 16b, valves are provided on the upstream and downstream sides of the second purifier 16b, and these valves are closed. A vacuum pump is connected to the piping 30 between the second purifier 16b and the upstream valve, and the second purifier 16b is evacuated. Then, a purge gas (e.g., argon) is supplied to the second purifier 16b from the piping 30 between the second purifier 16b and the downstream valve. Thereafter, the supply of the purge gas may be stopped, the second purifier 16b may be evacuated, and then the vacuum pump may be stopped and the laser gas may be filled into the second purifier 16b through the piping 30 between the second purifier 16b and the downstream valve. The same applies to the third purifier 16c (e.g., a purifier that adsorbs oxygen).

[0054] The gas supply control device 15, which is a constant-volume gas supply device, will be described in detail below with reference to the drawings. A constant-volume supply device is a device that supplies a predetermined volume of gas with a single operation (ejection). Figure 3 is a cross-sectional view showing the main configuration of the gas supply control device 15. Figure 3(A) shows the connections of the gas supply control device 15 in the gas purification device 100, and Figures 3(B), (C), and (D) are cross-sectional views showing the operation of the gas supply control device 15.

[0055] The gas supply control device 15 has an inlet 151, an outlet 152, an inlet channel 153, a constant volume section 154 (storage area), an outlet channel 155, a first valve 156 (inlet valve), and a second valve 157 (outlet valve). The first valve 156 and the second valve 157 are located at both ends of the constant volume section 154. The first valve 156 has a first valve body 156a and a first valve seat 156b, and the second valve 157 has a second valve body 157a and a second valve seat 157b. When the first valve body 156a and the first valve seat 156b are separated from each other, the first valve 156 is in an open state, and when the first valve body 156a and the first valve seat 156b are in contact with each other, the first valve 156 is in a closed state. Similarly, when the second valve element 157 a and the second valve seat 157 b are separated, the second valve 157 is in an open state, and when the second valve element 157 a and the second valve seat 157 b are in contact, the second valve 157 is in a closed state. It should be noted that a known configuration can be used as the valve that operates. For example, a diaphragm or the like can be used as the valve element, and the valve can be operated by, for example, an air (gas) drive system using compressed air or the like, or an electromagnetic drive system using an electromagnet or the like.

[0056] The inlet 151 is connected to the gas cylinder 14 via piping 31 (addition piping), and the outlet 152 is connected to piping 31. The additive gas from the gas cylinder 14 is supplied to the gas supply control device 15 via a pressure regulator RG2. The pressure regulator RG2 adjusts the additive gas to a pressure (PG2 = PG1 + Pd) that is higher by a predetermined amount Pd (e.g., 100 kPa) than the pressure of the recovered gas (PG1) set by the pressure regulator RG1 of the piping 30. The additive gas that flows out from the outlet 152 of the gas supply control device 15 flows into the piping 30 via the piping 31.

[0057] 3B, 3C, and 3D, the gas supply operation by the gas supply control device 15 will be described. For gas supply, a shot has the following steps.

[0058] 3B, the second valve 157 is closed and the first valve 156 is opened. As shown by the arrows in the figure, the additive gas whose pressure is adjusted by the pressure regulator RG2 flows into the constant volume section 154 via the inlet 151, the inlet path 153, and the first valve 156.

[0059] Step 2 (Accommodation Step) As shown in FIG. 3C, the first valve 156 is closed and the second valve 157 is closed. The additive gas is sealed in the constant-volume section 154 by the first valve 156 and the second valve 157. The sealed additive gas has a pressure PG2 (accommodation pressure) adjusted by the volume of the constant-volume section 154 and the pressure regulator RG2. The amount of additive gas is determined by the gas accommodated in the constant-volume section 154. This makes it possible to deliver a predetermined volume of gas in one ejection. The volume (capacity) of the constant-volume section 154 can be determined geometrically and can be, for example, but not limited to, 0.1-1 cc for the purpose of minute amount control. This step results in a quantitative determination of the additive gas.

[0060] 3D, the first valve 156 is kept closed, and the second valve 157 is opened. Since the pressure PG2 of the additive gas contained in the constant-volume section 154 is higher than the pressure PG1 of the recovered gas in the piping 30, the additive gas flows out of the gas supply control device 15 via the second valve 157, the outlet 155, and the outlet port 152, and then flows into the piping 30.

[0061] The amount of additive gas added per jet can be controlled by the volume and pressure of the constant-volume section 154. By setting the volume of the constant-volume section 154 according to the amount (volume) to be controlled, even minute amounts can be controlled. By controlling the number of jets, the amount of additive gas can be adjusted, and the necessary amount of additive gas can be mixed into the recovered gas. The control device 12 calculates the number of jets per unit time from the component concentrations of the recovered gas and the target component concentrations, and the control device 12 controls the number of jets per unit time by controlling the opening and closing of the first valve 156 and the second valve 157. The control device 12 digitally controls the opening and closing of the first valve 156 and the second valve 157, and the constant-volume supply device jets gas discretely (in pulses).

[0062] Conventionally, additive gas is controlled by a flow control device, specifically a mass flow controller, by controlling the continuous amount of gas flow. However, a mass flow controller requires a finite amount of time until the flow rate stabilizes, making it difficult to accurately control minute doping amounts. Furthermore, a mass flow controller has a small amount of residual gas in the space (dead space) between the flow rate control unit and the open / close valve located downstream. Because this residual gas exists downstream of the flow rate control unit, its flow rate cannot be controlled, making it difficult to accurately control the additive amount. In other words, with flow rate control using a conventional mass flow controller, it is difficult to accurately control the supply amount of minute additive gas from the gas cylinder 14.

[0063] On the other hand, the gas supply control device 15 determines the amount of gas added by a constant volume section 154 separated by two valves, so there is no dead space like in a mass flow controller, and no finite time is required to stabilize the flow rate. Therefore, the gas supply control device 15 is excellent at controlling minute amounts of gas added.

[0064] The gas supply control device 15 can be used not only to add gas during the purification process of the recovered gas, but also to supply laser gas when starting up the laser light generating device 1. Because it can control the amount of small amounts of additive gas added, it can also be used to generate laser gas with an optimal component concentration and fill it into the laser chamber. By generating laser gas and removing impurities with the purifier 16, it is possible to fill the laser chamber with laser gas of even higher purity.

[0065] According to the present invention, it is possible to accurately control the amount of additive gas added to the laser gas used in the laser light generator, and by enabling re-purification, it is possible to improve the impurity removal performance of the recovered gas and supply high-quality recovered gas. Recycling of laser gas can contribute to reducing the operating costs of the laser light generator, and has high industrial applicability.

[0066] REFERENCE SIGNS LIST 100 Gas purification device 1 Laser light generator 2 First tank (recovery tank) 3 First pump (recovery pump) 4 Second tank (first storage tank) 5 Second pump (booster pump) 6 Third tank (booster tank) 7 Fourth tank (second storage tank) 8 Third pump (supply pump) 9 Fifth tank (supply tank) 10 Piping (recovery piping) 11 Gas analyzer 12 Control device 13 Mixer 14 Gas cylinder 14a First gas cylinder 14b Second gas cylinder 15, 15a, 15b Gas supply control device (constant volume supply device) 151 Inlet 152 Outlet 153 Inlet channel 154 Constant volume section (storage area) 155 Outlet channel 156 First valve (inlet valve) 156a First valve body 156b First valve seat 157 Second valve (outlet valve) 157a Second valve body 157b Second valve seat 16 Purifier (impurity removal device) 16a First purifier (impurity removal device) 16b Second purifier (impurity removal device) 16c Third purifier (impurity removal device) 16d Fourth purifier (impurity removal device) 20 Piping (supply piping) 30 Piping (main piping) 31, 31a, 31b Piping (addition piping) 40 Housing A1 Piping A2 Piping B Piping (bypass piping) MFC Flow rate control device (mass flow controller) G6 Pressure gauge RG1 Pressure regulator RG2, RG2a, RG2b Pressure regulators V1-V10 Valves VA1, VA2 Valves

Claims

1. A gas purification device that purifies gas recovered from a laser light generating device that uses laser gas, and supplies the gas to the laser light generating device, comprising: a flow control device that controls the flow rate of the recovered gas; a constant-volume supply device that is provided downstream of the flow control device and that supplies an additive gas; and a purifier that is provided downstream of the constant-volume supply device.

2. A gas purification system according to claim 1, wherein said constant volume supply device supplies the additive gas in a discrete manner.

3. The gas purification apparatus according to claim 2, characterized in that the constant-volume supply device has a constant-volume section, a first valve and a second valve, the first valve and the second valve being located at both ends of the constant-volume section.

4. A gas purification device as claimed in any one of claims 1 to 3, characterized in that it comprises a first storage tank provided upstream of the flow control device and a second storage tank provided downstream of the purifier, the first storage tank and the second storage tank being connected in a manner that allows communication or disconnection.

5. The gas purification system according to claim 4, further comprising a gas analyzer, said gas analyzer performing a composition analysis of the gas in said first storage tank.

6. A method for purifying laser gas, comprising: a recovery step of recovering laser gas from a laser light generating device; a recovered gas analysis step of analyzing the recovered gas and determining whether or not an additive gas needs to be added; an addition step of adding the additive gas by a constant volume supply device if it is determined in the recovered gas analysis step that the addition of the additive gas is necessary; a purification step of purifying the recovered gas; a purified gas analysis step of analyzing the components of the recovered gas purified in the purification step and determining whether or not re-purification is necessary; and a re-purification step of carrying out the purification step if it is determined in the purified gas analysis step that re-purification is necessary.

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