JP3805073B2 - Excimer laser gas recovery equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an excimer laser gas recovery apparatus, and more particularly to an apparatus for recovering and purifying a rare gas in an excimer laser gas used in an excimer laser generator for reuse.
[0002]
[Prior art]
Excimer lasers are widely used in semiconductor manufacturing processes and the like as high-power ultraviolet light sources. In this excimer laser, an expensive rare gas is used as the excimer laser gas. For example, as described in Japanese Examined Patent Publication No. 7-60914, the excimer laser gas is extracted from the laser generator to purify the rare gas. Later, it has been proposed to reuse.
[0003]
In the method described in the above publication, the excimer laser gas extracted from the laser generator is reacted with a metal rich in reactivity with a fluorine-based gas (F ₂ , NF ₃ , ClF ₃ , ClF, etc.). After removing halogen gas such as fluorine with high activity, contact with alkali metal, alkaline earth metal compound, zeolite, metal alkali in order to make rare gas in excimer laser gas (Kr, Xe, He, Ne, etc.) The noble gas after purification is circulated to the laser generator.
[0004]
[Problems to be solved by the invention]
On the other hand, when collecting the entire amount of excimer laser gas used in the laser generator, it is necessary to suck the gas in the laser generator using a vacuum pump. However, an ordinary vacuum pump generates oil contamination and the like. In addition, outside air may be sucked in and oxygen, moisture, and other trace components may be mixed as impurities in the recovered gas, which may adversely affect the purification process of the recovered gas.
[0005]
For this reason, as a vacuum pump, a dry vacuum pump that is free from oil contamination and the like is used, and nitrogen gas is used as a seal gas so as not to suck in outside air. However, since the recovered gas discharged from this dry vacuum pump contains the nitrogen gas used as the seal gas, the nitrogen gas is separated and removed from the recovered gas in order to purify and reuse the rare gas. Need to be done.
[0006]
Therefore, the present invention can recover the entire amount of deteriorated excimer laser gas, can efficiently remove nitrogen gas used as a seal gas in a dry vacuum pump for gas recovery, and wastes expensive noble gas. It is an object of the present invention to provide an excimer laser gas recovery device that can be effectively reused without being discharged.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an excimer laser gas recovery apparatus of the present invention is an apparatus for recovering and purifying excimer laser gas containing a rare gas and a halogen gas extracted from an excimer laser generator, wherein the excimer laser gas is purified. Halogen removing means for removing halogen in the interior, dry vacuum pump for sucking excimer laser gas from the excimer laser generator through the halogen removing means, and nitrogen supply means for supplying sealing nitrogen gas to the dry vacuum pump; A nitrogen gas separation means for separating nitrogen gas in the recovered gas discharged from the dry vacuum pump; and a component gas replenishment unit for replenishing the component gas of the excimer laser gas to the purified gas separated from the nitrogen gas. It is a feature.
[0008]
Further, the excimer laser gas recovery device of the present invention is characterized in that the nitrogen gas separating means separates nitrogen gas by a low temperature adsorption method or a low temperature liquefaction rectification method, and the gas is discharged to the discharge side of the dry vacuum pump. And a timer for switching the gas flow direction of the gas discharge switching valve from the nitrogen gas separation means side to the discharge side when the operating time of the dry vacuum pump reaches a predetermined time. Further, the component gas replenishment unit includes a rare gas supply path for replenishing the purified gas with a rare gas in an excimer laser gas, an auxiliary tank provided downstream of the rare gas supply path, and an inside of the auxiliary tank. An analyzer for measuring the gas composition of the gas, flow rate adjusting means for adjusting the replenishment amount of the rare gas according to the measurement result of the analyzer, and a battery provided downstream of the auxiliary tank via a valve. Gas tank, a component gas supply path for replenishing the buffer tank with components other than the rare gas in the excimer laser gas, and a gas for controlling the gas replenishment amount from the component gas supply path according to the gas composition in the buffer tank And a replenishment amount control means.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a system diagram showing an embodiment of an excimer laser gas recovery apparatus according to the present invention. Hereinafter, the configuration of the apparatus will be described in accordance with the procedure until the excimer laser gas obtained by diluting KrF, which is a laser oscillation medium, with neon (Ne), which is a base gas, is collected, purified neon, and introduced into the laser generator 1 again. .
[0010]
The excimer laser gas in the laser generator 1 is sucked into the dry vacuum pump 4 through the recovery valve 1a, the halogen removal cylinder 2 and the filter 3. In the laser generator 1, as described above, the excimer laser gas obtained by adding the medium gas KrF to the base gas neon is filled in the chamber, and the filling pressure is generally about 0.4 MPa. That is, when the chamber volume is 25 liters, the amount of excimer laser gas used is about 100 liters.
[0011]
The halogen removal cylinder 2 is for removing the halogen gas in the excimer laser gas, and an adsorbent for halogen gas, for example, an adsorbent in which a metal mainly composed of copper or zinc is supported on activated carbon, What was packed in the stainless steel column can be used. By passing through the halogen removal cylinder 2, fluorine in the excimer laser gas is removed, and the fluorine concentration in the gas becomes 1 ppm or less. In addition, halogen gas such as fluorine is not only harmful to the human body, but also has high reactivity and strong corrosivity, so that the filter 3 and the dry vacuum pump 4 are not affected by the halogen gas. Thus, it is desirable to provide the halogen removal cylinder 2 at the beginning of the collection path.
[0012]
The filter 3 is for removing dust and the like generated by the reaction with fluorine (halogen gas) in the laser generator 1, and can be of any structure.
[0013]
The dry vacuum pump 4 is provided with nitrogen supply means 5 for supplying nitrogen gas used as seal gas and purge gas. Since this dry vacuum pump 4 does not use any lubricating oil in the pump chamber serving as a gas passage, the excimer laser gas in the laser generator 1 can be sucked and exhausted in its entirety without generating oil contamination. In addition, by supplying nitrogen gas as a seal gas, even if the laser generator 1 is sucked and exhausted to a high vacuum, the outside air containing impurities such as oxygen and moisture is not sucked.
[0014]
Further, the dry vacuum pump 4 is provided with a timer 6 for measuring the operation time of the dry vacuum pump 4, and on the downstream side of the dry vacuum pump 4, a discharge path 8 is connected via a gas discharge switching valve 7. A recovery gas storage tank 9 is provided.
[0015]
The timer 6 has a function of switching the gas flow direction of the gas discharge switching valve 7 from the recovered gas storage tank 9 side to the discharge path 8 side when the operation time of the dry vacuum pump 4 reaches a predetermined time. is doing. For example, since the dry vacuum pump 4 uses a pump having an exhaust capacity of 1500 liters / min or more so that the laser generator 1 can be sufficiently evacuated, a laser having a chamber volume of 25 liters (gas used amount: 100 liters). In the case of the generator 1, the excimer laser gas is exhausted in its entirety after 10 seconds from the start of exhaust, and the subsequent exhaust operation is expended for evacuating the laser generator 1.
[0016]
Therefore, after a certain amount of time has elapsed, most of the gas discharged from the dry vacuum pump 4 becomes nitrogen gas used as the seal gas. Therefore, the switching time of the gas discharge switching valve 7 by the timer 6 is set to, for example, 10 seconds from the start of exhaust, and the recovered gas discharged from the dry vacuum pump 4 is stored in the recovered gas for 10 seconds from the start of exhaust. The gas flows into the tank 9 and after 10 seconds, the gas flows in the discharge path 8. Thereby, unnecessary nitrogen gas can be prevented from flowing into the recovered gas storage tank 9. Further, when the dry vacuum pump 4 is operated for a predetermined time and the inside of the laser generator 1 reaches a sufficient degree of vacuum, the recovery valve 1 a can be closed and the dry vacuum pump 4 can be stopped by a signal from the timer 6. .
[0017]
The recovery gas storage tank 9 is provided as necessary depending on the recovery gas amount. As described above, when the recovery gas amount per one time is about 100 liters, the recovery gas storage tank 9 is purified depending on the purification method of the subsequent purification equipment. Since the efficiency is lowered, the recovered gas is introduced into the subsequent purification equipment when the amount of recovered gas corresponding to the purification method is stored. The composition of the gas stored in the recovered gas storage tank 9 varies depending on the composition and amount of the medium gas used, the capacity of the dry vacuum pump 4, etc., but is in a state where about 8% of nitrogen is mixed.
[0018]
A purification facility 12 is provided on the downstream side of the recovered gas storage tank 9 via a booster 10 and a carbon dioxide / water removal cylinder 11. The booster 10 is for boosting the recovered gas to a pressure necessary for reintroducing the purified gas into the laser generator 1. Depending on the purification method of the purification equipment 12, the booster 10 has a required operating pressure. Pressurize the recovered gas until Also in the booster 10, it is preferable to use a compressor in which lubricating oil or the like is not mixed in the gas, for example, a compressor of a diaphragm type or a bellows type.
[0019]
The carbon dioxide / water removal cylinder 11 is provided for removing carbon dioxide and water frozen in the pipe line from the recovered gas in advance in order to purify the rare gas in the purification facility 12 at a low temperature. It is filled with an adsorbent such as molecular sieves.
[0020]
The purification equipment 12 which is a nitrogen gas separation means uses a low temperature adsorption method using a difference in adsorption power between nitrogen gas and a rare gas at a low temperature, a low temperature liquefaction rectification method using a difference in boiling point, etc. It can be appropriately selected and used according to the composition, the recovered amount, the purity of the rare gas after purification, and the user's request.
[0021]
This embodiment shows an example in which nitrogen is separated by a low temperature adsorption method. The purification equipment 12 by this low temperature adsorption method includes a heat insulating tank 14 containing an adsorption cylinder 13 filled with a nitrogen adsorbent such as activated carbon, and a cold source for cooling the adsorption cylinder 13, for example, liquefied nitrogen in the heat insulating tank 14. A liquefied nitrogen supply means 15 for introducing, an analyzer 16 for analyzing the gas component flowing out from the adsorption cylinder 13, and a switching valve 17 for switching the gas flow path according to the analysis result of the analyzer 16; A recovery gas inlet valve 18 and a purified gas outlet valve 19 are respectively provided before and after the purification facility 12.
[0022]
The separation of nitrogen gas by the purification equipment 12 can be performed as follows. First, liquefied nitrogen is injected into the heat insulation tank 14 from the liquefied nitrogen supply means 15, and the adsorption cylinder 13 is cooled to a predetermined temperature. Next, the operation of the booster 10 is started, and the recovered gas introduction valve 18 and the purified gas outlet valve 19 are opened, and the recovered gas in the recovered gas storage tank 9 is supplied to the adsorption cylinder 13 through the carbon dioxide / water removal cylinder 11. To introduce.
[0023]
The analyzer 16 analyzes the gas component derived from the adsorption cylinder 13 based on thermal conductivity and the like, and when the gas is neon, switches the gas flow path of the switching valve 17 to the purified gas outlet valve 19 side. Further, when the state of the gas led out from the adsorption cylinder 13 changes, that is, when the purity of neon becomes lower than the predetermined purity, the gas flow path of the switching valve 17 is switched to the nitrogen release path 20 side to discharge the gas. At the same time, the recovered gas introduction valve 18 and the purified gas outlet valve 19 are closed, the booster 10 is stopped, and the purification operation is finished.
[0024]
After completion of the refining operation, the liquefied nitrogen in the heat insulating tank 14 is extracted from the passage 21, and nitrogen gas heated to a predetermined temperature is introduced into the heat insulating tank 14 to heat the adsorption cylinder 13, or heated by a heater or the like, Further, if necessary, the inside of the adsorption cylinder 13 is evacuated by a vacuum pump provided in the nitrogen release path 20 to desorb nitrogen and krypton (Kr) adsorbed on the adsorbent and activate the adsorbent. Let
[0025]
The purified gas derived from the purification equipment 12 via the switching valve 17 and the purified gas outlet valve 19 is a component gas that replenishes each component gas according to the consumption, loss, and removal in the laser generator 1 and the recovery and purification route. It is introduced into the buffer tank 23 through the replenishing unit 22. The component gas replenishment unit 22 includes a neon supply path 24 and a krypton supply path 25 for replenishing neon and krypton as rare gas components in the excimer laser gas, and fluorine for replenishing fluorine as a component other than the rare gas. The auxiliary tank 28 having a mass spectrometer 27 is provided on the downstream side of the neon supply path 24 and the krypton supply path 25. The buffer tank 23 includes a pressure gauge 29 and a control unit. A container 30 is provided.
[0026]
The mass spectrometer 27 analyzes the gas composition in the auxiliary tank 28 and controls the flow regulators 24a and 25a provided in the neon supply path 24 and the krypton supply path 25, respectively, according to the analysis result. Neon, which is a gas, and krypton, which is a medium gas, are stored in the auxiliary tank 28 with a predetermined composition, and are introduced into the buffer tank 23 by opening the valve 31. At this time, the replenishment amount of neon from the neon supply path 24 is set according to the flow rate and pressure of the purified neon derived from the refining facility 12, and only the amount of krypton to be replenished from the krypton supply path 25 is You may make it control by the measured value of the mass spectrometer 27. FIG.
[0027]
The pressure gauge 29 measures the amount of gas introduced from the auxiliary tank 28 through the valve 31 into the buffer tank 23 with pressure, and measures the pressure in the buffer tank 23 measured by the pressure gauge 29. Based on the increase, the controller 30 calculates the replenishment amount of fluorine, thereby controlling the flow rate regulator 26a and replenishing a predetermined amount of fluorine from the fluorine supply path 26, whereby a predetermined gas composition in the buffer tank 23 is obtained. Excimer laser gas is stored. Each supply path may be connected to each tank without being connected to the pipe.
[0028]
The excimer laser gas stored in the buffer tank 23 in this manner is filled into the laser generator 1 at a predetermined pressure via the filling valve 1b.
[0029]
In this way, the excimer laser gas deteriorated from the laser generator 1 is recovered using the dry vacuum pump 4 sealed with nitrogen gas, and the mixed nitrogen is removed by a method such as low-temperature adsorption, so that the excimer laser gas contains Neon (rare gas) can be efficiently recovered and reused.
[0030]
In addition, this invention is not limited to the said example of a form, Various modifications can be considered. For example, the low temperature liquefaction rectification method can be employed as the purification equipment 12 as described above. In this low temperature liquefaction rectification method, a recovered gas whose pressure has been increased to a predetermined pressure is introduced into a rectifying cylinder, a reflux liquid is generated using liquefied nitrogen or the like as a cold source, and the reflux gas and the rising gas composed of the recovered gas are gasified. The rectification operation is carried out in liquid contact, neon having a low boiling point is obtained from the top of the rectification cylinder, and nitrogen and krypton having a high boiling point are obtained from the bottom of the column. It is also possible to rectify and separate krypton by providing multiple rectification tubes and appropriately setting conditions such as pressure. The rectification conditions such as pressure include the composition, throughput, and sampling of the recovered gas. It can be set according to the purity and the like desired for the rare gas.
[0031]
In addition, the buffer tank 23 may be provided between the purification equipment 12 and the component gas replenishment unit 22. In this case, since the gas stored in the buffer tank 23 is purified neon, when the excimer laser gas is filled in the laser generator 1, it corresponds to the amount derived from the buffer tank 23. What is necessary is just to set the replenishment amount of each gas from each supply path. The gas to be replenished from each supply path naturally varies depending on the composition of the excimer laser gas, for example, the type of medium gas such as ArF, KrF, XeF, NeF, XeCl, and the number of paths can be increased or decreased depending on the gas type.
[0032]
Further, the recovery and filling of the excimer laser gas of the laser generator 1 and the purification process of the recovered gas are performed in a batch system, so that, for example, a plurality of recovery valves 1a and filling valves 1b are provided. Thus, it is possible to cope with a plurality of laser generators, the recovered gas can be merged in the recovered gas storage tank 9 portion, and the purified gas can be branched in the purified gas outlet valve 19 portion.
[0033]
The nitrogen gas or liquefied nitrogen used in each part can be one filled in a gas container, but can be supplied from an air separation device installed in a semiconductor manufacturing factory or the like, and the purification equipment 12 The nitrogen gas and liquefied nitrogen derived from the discharge path 20 and the path 21 may be returned to the air separation device.
[0034]
【The invention's effect】
As described above, according to the excimer laser gas recovery device of the present invention, the deteriorated excimer laser gas is sucked by the dry vacuum pump, so that the entire amount can be recovered and the amount of expensive rare gas discarded can be reduced. This can greatly reduce the operating cost of the laser generator.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of an excimer laser gas recovery apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laser generator, 1a ... Recovery valve, 1b ... Filling valve, 2 ... Halogen removal cylinder, 3 ... Filter, 4 ... Dry vacuum pump, 5 ... Nitrogen supply means, 6 ... Timer, 7 ... Switching valve for gas discharge, DESCRIPTION OF SYMBOLS 8 ... Release path, 9 ... Recovery gas storage tank, 10 ... Booster, 11 ... Carbon dioxide and moisture removal cylinder, 12 ... Purification equipment, 13 ... Adsorption cylinder, 14 ... Heat insulation tank, 15 ... Liquid nitrogen supply means, 16 ... Analyzer: 17 ... Switching valve, 18 ... Collected gas introduction valve, 19 ... Purified gas outlet valve, 20 ... Nitrogen release path, 22 ... Component gas replenishment section, 23 ... Buffer tank, 24 ... Neon supply path, 25 ... Krypton supply Path, 26 ... fluorine supply path, 24a, 25a, 26a ... flow rate regulator, 27 ... mass spectrometer, 28 ... auxiliary tank, 29 ... pressure gauge, 30 ... controller

Claims (4)

An apparatus for recovering and purifying an excimer laser gas containing a rare gas and a halogen gas extracted from an excimer laser generator, wherein the halogen is removed from the excimer laser gas, and the halogen is removed from the excimer laser generator. A dry vacuum pump for sucking excimer laser gas through the removing means, a nitrogen supply means for supplying sealing nitrogen gas to the dry vacuum pump, and a nitrogen gas for separating nitrogen gas in the recovered gas discharged from the dry vacuum pump An excimer laser gas recovery apparatus comprising: a separation unit; and a component gas replenishment unit that replenishes a component gas of the excimer laser gas to a purified gas from which nitrogen gas has been separated. The excimer laser gas recovery apparatus according to claim 1, wherein the nitrogen gas separation means separates the nitrogen gas by a low temperature adsorption method or a low temperature liquefaction rectification method. A gas discharge switching valve is provided on the discharge side of the dry vacuum pump, and when the operating time of the dry vacuum pump reaches a predetermined time, the gas flow direction of the gas discharge switching valve is changed to the nitrogen gas separating means. The excimer laser gas recovery apparatus according to claim 1, further comprising a timer for switching from the side to the discharge side. The component gas replenishment unit includes a rare gas supply path for replenishing the purified gas with a rare gas in excimer laser gas, an auxiliary tank provided downstream of the rare gas supply path, and a gas composition in the auxiliary tank. An analyzer to be measured, a flow rate adjusting means for adjusting the replenishment amount of the rare gas according to the measurement result of the analyzer, a buffer tank provided via a valve downstream of the auxiliary tank, and an excimer in the buffer tank A component gas supply path for replenishing components other than the rare gas in the laser gas, and a gas replenishment amount control means for controlling the gas replenishment amount from the component gas supply path according to the gas composition in the buffer tank are provided. The excimer laser gas recovery apparatus according to claim 1.

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