JP2019195758A - Gas separator and gas separation method - Google Patents

Abstract

To provide a gas separator and a gas separation method that recover noble gases such as xenon gas and krypton without using nitrogen gas for diluting PFC gas.SOLUTION: A gas separator 1 comprises a carrying pipe 12 for carrying exhaust gas containing at least noble gas discharged from a semiconductor wafer processing device 11, a noble gas supply pipe 16 connected to the carrying pipe 12 and introducing the same kind of noble gas as the noble gas to the carrying pipe 12, and a noble gas recovery device 21 connected with the carrying pipe 12 and recovering the noble gas by removing gas compositions except the noble gas contained in the exhaust gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas separation device and a gas separation method.

In the semiconductor manufacturing process, various gases are used corresponding to the process. For example, perfluoro compounds (PFCs) such as CF ₄ , NF ₃ , C ₂ F ₆ , C ₃ F ₈ , SF ₆ , and CHF ₃ are used as reactive gases in dry etching processes and thin film forming processes. And exhaust gas containing these is generated.
When exhaust gas is discharged, a large amount of nitrogen (N ₂ ) gas is introduced for the purpose of protecting the vacuum pump, and PFC gas not used in the reaction is diluted and discharged.
In recent years, an anisotropic etching technique has been developed to perform more precise etching while maintaining a fine and high aspect ratio for the production of highly stacked 3D (three-dimensional) -NAND flash memories. In this etching, in addition to PFC gas such as hexafluoro-1,3-butadiene (C ₄ F ₆ ) gas, octafluorocyclobutane (C ₄ F ₈ ) gas, or octafluorocyclopentene (C ₅ F ₈ ) gas, a rare gas is used. A technique using xenon (Xe) or krypton (Kr) as an assist gas is introduced. Since this technology uses expensive rare gases such as Xe gas and Kr gas, it has been demanded to collect and reuse these rare gases.
When collecting the rare gas, it is necessary not only to remove the PFC gas from the rare gas but also to separate a large amount of N ₂ gas used for diluting the PFC gas. The gas separation technology includes a cryogenic distillation method that separates by a difference in boiling point, a pressure swing adsorption (PSA) / temperature swing adsorption (TSA) method that repeats adsorption and desorption, and a membrane separation method that uses a gas separation membrane.
Further, in Patent Document 1, after removing impurities other than N ₂ by pretreatment such as catalytic decomposition method, plasma decomposition method, adsorption method, etc., from the gas exhausted from the vacuum exhaust system, activated carbon is used as an adsorbent. A method for recovering Xe from ₂ is described. Patent Document 2 describes a system using zeolite as an adsorbent in order to separate Xe and N ₂ .

JP 2005-336046 A JP 2010-043881 A

The rare gas and N ₂ are a combination that is difficult to separate from each other because their physical properties are relatively similar. For example, in a membrane separation method which is one of gas separation techniques, separation is performed based on the difference in pore diameter of zeolite, which is a membrane material, and the dynamic molecular diameter of noble gas and N ₂ . However, the dynamic molecular diameter of Xe, which is a rare gas, is 0.396 nm, and that of N ₂ is 0.36 nm, so the difference in dynamic molecular diameter is very small. Furthermore, since the dynamic molecular diameter of Kr, which is the same noble gas, is almost the same as that of N ₂ , their separation efficiency is very low. Not only in terms of dynamic molecular diameter, but also with respect to the adsorptive power to the adsorbent, it has relatively similar properties.

  The present invention provides a gas separation apparatus that processes exhaust gas from a semiconductor wafer processing apparatus that uses a rare gas as an assist gas, and that enables efficient recovery and reuse of an expensive rare gas. This is the issue. The present invention also provides a gas separation method for treating exhaust gas from a semiconductor wafer processing apparatus that uses a rare gas as an assist gas, the gas separation method enabling efficient recovery and reuse of expensive rare gas. The issue is to provide.

As a result of intensive studies in view of the above problems, the present inventors have used a rare gas instead of the conventionally used N ₂ gas as the dilution gas, thereby improving the separation and recovery efficiency of the rare gas from the exhaust gas. It was found that it can be improved. Furthermore, it has been found that if the collected rare gas is reused, the rare gas in the semiconductor wafer processing step can be circulated without loss, and as a result, the amount of rare gas used in the semiconductor wafer processing apparatus can be greatly reduced. The present invention has been further studied based on the above findings and has been completed.

That is, the said subject of this invention was solved by the following means.
[1]
A transfer pipe for transferring an exhaust gas containing at least a rare gas discharged from the semiconductor wafer processing apparatus;
A rare gas supply pipe connected to the carrier pipe and introducing the same kind of rare gas as the rare gas into the carrier pipe;
A gas separation device having a rare gas recovery device connected to the transfer pipe and removing a gas component other than the rare gas contained in the exhaust gas to recover the rare gas.
[2]
The rare gas recovery device is one of a water removal device, a plasma abatement device, a dry abatement device, an adsorption abatement device, a pressure swing adsorption device, a temperature swing adsorption device, a chromatographic separation device, and a membrane separation device, or The gas separation device according to [1], having a combination thereof.
[3]
The noble gas recovery device is connected to the moisture removal device for removing moisture from the exhaust gas, and a discharge side of the moisture removal device, and removes perfluoro compound gas and acid gas from the gas discharged from the moisture removal device. The gas separation device according to [2], including the adsorption and detoxification device to be removed.
[4]
[3] The gas separation device according to [3], further including a chromatographic separation device that is connected to a discharge side of the adsorption removal device and collects a rare gas by chromatographic separation of the gas discharged from the adsorption removal device.
[5]
The gas separation device according to [4], wherein the chromatographic separation device includes a plurality of chromatographic columns, and each chromatographic column performs chromatographic separation at different timings.
[6]
The gas separation device according to any one of [1] to [5], wherein the rare gas is xenon gas.

[7]
A gas separation method for recovering a rare gas from an exhaust gas containing at least a rare gas discharged from a semiconductor wafer processing step,
Introducing a rare gas of the same type as the rare gas discharged from the semiconductor wafer processing step into the exhaust gas;
A step of transferring exhaust gas into which the same kind of rare gas is introduced;
A gas separation method including a removal and recovery step of recovering the rare gas after removing gas components other than the rare gas from the exhaust gas into which the rare gas has been introduced.
[8]
The removal and recovery step is any one of a water removal step, a plasma removal step, a dry removal step, an adsorption removal step, a pressure swing adsorption step, a temperature swing adsorption step, a chromatographic separation step, and a membrane separation step or The gas separation method according to [7], which includes these combined steps.
[9]
The exhaust gas contains perfluoro compound gas, acid gas, noble gas and water,
[8] The removal and recovery step includes a water removal step for removing the water, and an adsorption removal step for removing the perfluoro compound gas and the acid gas from the exhaust gas discharged from the water removal step. Gas separation method.
[10]
[9] The gas separation method according to [9], further including a chromatographic separation step of collecting a rare gas by chromatographic separation of the gas discharged from the adsorption detoxification step after the adsorption detoxification step.

  As described above, according to the present invention, by removing the PFC gas from the rare gas, the rare gas can be reused not only as an assist gas but also as an introduction gas for protecting a vacuum pump. The amount of gas used can be greatly reduced.

It is the schematic block diagram which showed one preferable embodiment (1st Embodiment) of the gas separation apparatus of this invention. It is the schematic block diagram which showed preferable one Embodiment (2nd Embodiment) of the gas separation apparatus of this invention. It is the schematic block diagram which showed a preferable example of the chromatographic separation apparatus used for the gas separation apparatus of this invention. The branch pipes 212A to 212D in the upper diagram of FIG. 3 are connected to the branch pipes 212A to 212D in the lower diagram of FIG.

A preferred embodiment (first embodiment) of a gas separation apparatus according to the present invention will be described with reference to FIG.
As shown in FIG. 1, the semiconductor wafer processing apparatus 11 is connected to a transfer pipe 12 that transfers exhaust gas containing at least PFC gas and a rare gas discharged from the semiconductor wafer processing apparatus 11. For example, Xe gas is used as the rare gas. Examples of the semiconductor wafer processing apparatus 11 include a dry etching apparatus and a chemical vapor deposition apparatus. The semiconductor wafer processing apparatus 11 of the dry etching apparatus will be described below as an example.

  For example, a PFC gas supply pipe 13 that supplies PFC gas as an etching gas and an assist gas supply pipe 14 that supplies Xe gas as an etching assist gas are connected to the semiconductor wafer processing apparatus 11.

In the case of the dry etching process, PFC gas, acid gas such as carbon dioxide and hydrogen fluoride (HF), gas containing Xe gas and water (H ₂ O) are discharged as exhaust gas. A transport pipe 12 for transporting the exhaust gas is connected to the gas discharge side 11B of the semiconductor wafer processing apparatus, and a vacuum pump 15 is disposed in the transport pipe 12. Accordingly, the exhaust gas in the transfer pipe 12 is sucked from the suction side 15A of the vacuum pump 15 and sent out to the transfer pipe 12 on the discharge side 15B of the vacuum pump 15. A rare gas supply pipe 16 for introducing Xe gas of the same type as the Xe gas into the transport pipe 12 is connected to the transport pipe 12 on the suction side 15A of the vacuum pump.
A rare gas recovery device 21 that recovers Xe gas by removing gas components other than Xe gas contained in the exhaust gas is connected to the transport pipe 12.

The rare gas recovery device 21 is connected to a moisture removal device 22 that removes moisture in the exhaust gas and a discharge side of the moisture removal device 22 via a pipe 24, and removes acidic gas and PFC gas from the exhaust gas from the moisture removal device 22. It is preferable to have an abatement device 23 that adsorbs and discharges Xe gas. In the moisture removing device 22, at least one of silica gel, activated alumina, molecular sieves 3A to 5A (manufactured by Union Showa Co., Ltd .: trade name) and the like can be used as a moisture adsorbent. In the abatement apparatus 23, zeolite or activated carbon is used as an adsorbent for acid gas and PFC gas. A recovery rare gas supply pipe 17 that supplies the recovered Xe gas is connected to the rare gas supply pipe 16 and / or the assist gas supply pipe 14. It is preferable that one branch supply pipe 18 branched from the recovered rare gas supply pipe 17 is connected to the rare gas supply pipe 16 and the other branch supply pipe 19 is connected to the assist gas supply pipe 14.
As described above, after removing moisture in the exhaust gas by the moisture removing device 22, the exhaust gas is supplied to the abatement device 23, so that the heat generation of the abatement device 23 is suppressed and the acidic gas such as CO ₂ gas and the PFC are suppressed. The gas removal ability can be demonstrated stably.

It is preferable that the detoxification device 23 is composed of any one of or a combination of a plasma detoxification device, a dry detoxification device, and an adsorption detoxification device. Here, a mode in which a room temperature adsorption type adsorption detoxifying device is used as the detoxifying device 23 will be described.
The room temperature adsorption-type adsorption abatement removes carbon dioxide and PFC gas by physical adsorption and chemical adsorption using the gas adsorption properties of substances having a large surface area such as alumina, activated carbon and zeolite.
When hydrogen fluoride (HF) is generated by the PFC gas detoxification treatment, detoxification treatment using zeolite or activated carbon can be combined.

  The detoxifying device 23 removes acidic gas and PFC gas in the exhaust gas sent from the moisture removing device 22 and discharges Xe gas. The purity of the Xe gas is high, for example, 99.8% by mass or more.

  In the rare gas recovery device 21, the form using the room temperature adsorption adsorption removal device has been described, but instead of the room temperature adsorption removal device, for example, a plasma removal device, a dry removal device, and a heat adsorption device are used. At least one of an adsorption detoxifying device, a PSA device, a TSA device, a chromatographic separation device, and a membrane separation device can also be used. It is also preferable to combine at least one of the above devices in addition to the room temperature adsorption type adsorption exclusion device. Hereinafter, these apparatuses will be described.

[Plasma abatement system]
The plasma abatement apparatus introduces exhaust gas into a reactor that has generated plasma, and thermally decomposes the PFC gas in the exhaust gas with the plasma to remove the gas. Specifically, PFC gas is pyrolyzed using ultra high temperature (near 2000 ° C.) plasma heat. Examples of plasma generation methods include microwave discharge, radio frequency (RF) discharge, arc discharge, and the like.

[Dry-type abatement system (combustion type)]
A combustion-type dry abatement apparatus generally decomposes PFC gas in exhaust gas by using a combustion flame of gaseous fuel (city gas, propane, or hydrogen). PFC gas etc. is pyrolyzed by the combustion flame.

[Dry-type abatement device (electric heating type)]
The electric heating type dry-type abatement apparatus uses the heat of a heater to decompose and remove PFC gas in exhaust gas. Warm-up operation time of about 2 to 4 hours is required from the start of operation until processing is possible. Also, a large amount of air or water is required to cool the high temperature processing gas.
[Adsorption detoxification device (heat adsorption type)]
The adsorption detoxification device (heat adsorption type) detoxifies a gas that is difficult to adsorb at normal temperature by contacting it with a catalyst or the like at a high temperature, thereby adsorbing it as a gas that is easily adsorbed.

[Pressure swing adsorption (PSA) equipment]
The PSA device uses the fact that the adsorption capacity varies depending on the partial pressure of the gas to be adsorbed, and by removing the gas that is easily adsorbed by increasing and decreasing the pressure, the gas that is difficult to adsorb is concentrated. Specifically, the gas is adsorbed on the adsorbent by increasing the pressure, and the gas is desorbed from the adsorbent by decreasing the pressure to separate and recover the gas. For example, when the gas A has a larger adsorption capacity to the adsorbent than the gas B, the gas A is more adsorbed and removed than the gas B, and the gas B can be concentrated as a non-adsorbed gas.
Industrially, several kinds of mixed gases to be separated are pressurized and introduced into an adsorption tank filled with an adsorbent as a fixed bed. Separation is performed by preferentially adsorbing from a gas that has a high adsorption rate or is easily adsorbed. Thereafter, by reducing the pressure, the adsorbed gas (adsorbed gas) is desorbed to obtain product gas, or the gas that has not been adsorbed (non-adsorbed gas) is taken as product gas to the outside of the adsorption tank and obtained. Usually, each gas is taken out from the entrance / exit side of the adsorption tank in a separated or concentrated form.

[Temperature swing adsorption (TSA) equipment]
The TSA apparatus performs gas separation utilizing the fact that the adsorption amount is reduced by increasing the temperature, and simultaneously performs heating and carrying out the desorption component out of the system with a non-reactive gas. It is used to remove components with strong affinity such as water, hydrogen sulfide, carbon dioxide, the heating temperature reaches 200 ° C. to 350 ° C., and the regeneration time also takes several hours.
The TSA apparatus is used in combination with a cryogenic distillation apparatus, operates at room temperature and normal pressure, and separates adsorbed impure gas with a temperature increase of about 200 degrees. The TSA apparatus is often used for the purpose of removing water and carbon dioxide gas from a raw material gas when producing O ₂ and N ₂ by a cryogenic distillation apparatus.

[Membrane separator]
The membrane separation device is a device that separates a specific gas component by using the gas permeability of the gas separation membrane. The polymer material (molecular membrane) constituting the gas separation membrane has angstrom-order voids between molecules. When gas passes through this gap, it is possible to move a specific gas. For example, when a gas exists on both sides across a molecular film having no defect, the gas permeates from a higher partial pressure to a lower one. At that time, the gas is separated into a gas that can pass through the gap and a gas that cannot. An application of this principle is a membrane separation device using a gas separation membrane.

[Chromatograph separation device]
Chromatographic separation refers to a method of separating a specific chemical component from a mixture using an adsorption phenomenon or the like. This chromatographic separation is a technique for spatially separating gas components in the exhaust gas by a stationary phase, and is separated by being sequentially transported to a detection unit (region filled with a separating agent) fixed at a specific location. Therefore, since it is almost the case that the separation is performed on the time axis of the holding time, it is preferable to use a plurality of chromatographic separation apparatuses for continuous processing.

Moreover, it is preferable that the separation material used for a PSA apparatus, a TSA apparatus, and a chromatographic separation apparatus is a zeolite. The zeolite used in the present invention depends on the apparatus and the gas type. For example, in the case of a PSA apparatus that separates and recovers Xe gas, the pore diameter is 0.1 to 1.0 nm, preferably 0.2 to 0. .9 nm, more preferably 0.3 to 0.5 nm. Further, the surface area of pores per 1g, a 150～900M ^2, preferably 160～500M ^2, more preferably 170~300m ^2.
As such zeolite, synthetic zeolite or natural zeolite is used. As synthetic zeolite, Union Showa Co., Ltd. molecular sieve 13X (brand name), Tosoh HSZ-800 (brand name), etc. can be used, for example. Examples of natural zeolite include mordenite and chabazite.

Next, a gas separation method using the gas separation device 1A of the first embodiment shown in FIG. 1 will be described below.
The gas separation method according to the first embodiment of the present invention is a gas separation method for recovering a rare gas from an exhaust gas containing at least a rare gas discharged from a dry etching process which is a semiconductor wafer processing process.
As shown in FIG. 1, a rare gas of the same type as the rare gas contained in the exhaust gas is introduced into the exhaust gas discharged from the dry etching process through the transfer pipe 12 through the rare gas supply pipe 16 (rare gas introduction process). By introducing the rare gas, the PFC gas that may corrode the vacuum pump 15 can be diluted. Therefore, although the amount of Xe gas introduced depends on the amount of Xe gas contained in the exhaust gas discharged from the dry etching process, the constituent material of the vacuum pump 15, etc., at least the vacuum pump 15 is not corroded, for example. It is preferable to introduce an amount of Xe gas that can be protected at the same time and does not react with other gas components. Xe gas is introduced into the exhaust gas so that, for example, the PFC gas concentration is 0.1 mass% or less, preferably 0.05 mass% or less. And the exhaust gas which introduce | transduced the same kind of rare gas is transferred with the vacuum pump 15 (exhaust gas conveyance process). After removing gas components other than the rare gas from the exhaust gas introduced with the rare gas conveyed by the vacuum pump 15, the rare gas is recovered (removal and recovery step).

In the gas separation apparatus 1A, the Xe gas contained in the exhaust gas discharged from the dry etching apparatus (semiconductor manufacturing process) can be recovered at a high concentration. At that time, since the same kind of Xe gas as the Xe gas contained in the exhaust gas is introduced into the exhaust gas for diluting the PFC gas, it is not necessary to use N ₂ gas for protecting the vacuum pump 15. Since the PFC gas is diluted with the Xe gas in this way, the protection of the vacuum pump 15 by introducing the N ₂ gas can be performed by the introduced Xe gas. Thus, the vacuum pump 15 is protected without using the N ₂ gas, and the introduced Xe gas can be recovered together with the Xe gas used as the etching assist gas. Further, since it is not necessary to separate and discharge N ₂ gas, the gas separation process is simplified, the time required for gas separation can be reduced, and the recovery efficiency of Xe gas can be sufficiently increased.

  Further, in the gas separation apparatus 1A, it is possible to separate and collect almost 100% by mass of the Xe gas. For this reason, the recovered Xe gas can be reused as an assist gas for dry etching, and can also be reused as a dilution gas for protecting the vacuum pump for efficient circulation. Therefore, although initial investment of Xe gas is necessary, once Xe gas is supplied as the assist gas and as the dilution gas, the recovered Xe gas is circulated and used as the assist gas and as the dilution gas. be able to. Therefore, since it is not necessary to introduce new Xe gas into the semiconductor wafer processing process once processing is started, the amount of Xe gas used can be greatly reduced and wafer processing can be performed at low cost. Become.

Next, an example of a preferred embodiment (second embodiment) of the gas separation apparatus of the present invention will be described with reference to FIG.
As shown in FIG. 2, the gas separation apparatus 1 (1B) is connected to the discharge side of the abatement apparatus 23 with respect to the configuration of the gas separation apparatus 1A, and chromatographs the gas discharged from the abatement apparatus 23 A chromatographic separation device 31 is connected. The adsorption device 23 and the chromatographic separation device 31 are connected by a pipe 25. Therefore, the gas discharged from the detoxifying device 23 is supplied to the chromatographic separation device 31 through the pipe 25. Other configurations are the same as those of the gas separation apparatus 1A described with reference to FIG.

  As shown in FIG. 3, the chromatographic separation device 31 can take, for example, 20 minutes to process the exhaust gas by one gas separation means 102. That is, the time from the start of the exhaust gas supply to the gas separation means 102 to the end of the Xe gas discharge can be set to 20 minutes. Further, for example, the supply time of the exhaust gas to the gas separation means 102 can be set to 5 minutes. In order to continuously perform the gas separation process without interruption using the chromatographic separation means 102 as in the above example, four gas separation means 102 are required. Therefore, the chromatographic separation device 31 for continuously treating the exhaust gas is provided with four gas separation means 102 (102A to 102D).

  The chromatographic separation device 31 includes a supply pipe 212 to which exhaust gas (for example, a mixed gas containing Xe) is supplied from an exhaust gas supply source 211. The exhaust gas supply source 211 is the pipe 25 described above (see FIG. 2). A supply pipe 212 is connected to the exhaust gas supply source 211 and is branched into four on the upstream side. A supply valve 214 that opens and closes the flow path is provided in each branched supply pipe 212 (212A to 212D). It has been. Each of the supply pipes 212 </ b> A to 212 </ b> D is connected to the inlet 112 of the column 111 of each gas separation means 102. Therefore, a mixed gas containing Xe is supplied from the inlet 112 of the column 111 as, for example, exhaust gas.

  The size of the column 111 is appropriately determined depending on the processing amount. As an example, a cylinder (for example, a cylinder) having an inner diameter of 19 to 200 mm from the viewpoint of replacement of the packed column (or agent) and a length (height) of 0.25 to 2 m from the viewpoint of being installed in the vicinity of the semiconductor manufacturing line. ). A cylinder having an inner diameter of 50 to 180 mm and a length of 0.5 to 1.5 m is preferable, and a cylinder having an inner diameter of 120 to 160 mm and a length of 0.7 to 1 m is more preferable. The column 111 is filled with zeolite (not shown).

The outlet 113 of each column 111 is connected to the suction side 122 of a vacuum pump 121 as decompression means. As the vacuum pump 121, for example, nXDS10i (trade name) manufactured by Edwards (attainment pressure: 0.7 Pa, exhaust speed: 190 SLM) can be used.
A main pipe 134 to which an exhaust branch pipe 131 and a recovery branch pipe 132 are connected is connected to the exhaust side of the vacuum pump 121. Further, a QMS 143 is connected via an analysis piping valve 142 that branches the analysis piping 141 from the middle of the main piping 134 and opens and closes the flow path. As the QMS 143, for example, a quadrupole mass spectrometer with a differential exhaust system kit: Qule with YTP (trade name) manufactured by ULVAC, Inc. can be used.

Further, a branch pipe 131 that exhausts the hardly adsorbing gas separated by the column 111 is arranged in the main pipe 134 via a branch valve 135 that opens and closes the flow path. Examples of the hardly adsorptive gas include PFC gas (for example, CF ₄ gas) and carbon monoxide (CO) gas that cannot be removed by the abatement apparatus 23 in the previous stage. A branch pipe 132 that collects Xe gas separated by the column 111 is arranged via a branch valve 136 that opens and closes the flow path. Further, the main pipe 134 is used to send a mixed gas of PFC gas, CO gas and Xe gas to the next column, and a main pipe valve 138 is arranged. In the column 111, the hardly adsorbing gas is discharged first, then the mixed gas of the hardly adsorbing gas and the Xe gas is discharged, and then the Xe gas is discharged. For this reason, it is preferable that the branch pipe 131 for flowing the hardly adsorbing gas is branched from the main pipe 134 on the vacuum pump 121 side than the branch pipe 132 for collecting the Xe gas.
The branch pipe 132 is the recovered rare gas supply pipe 17 shown in FIGS. 1 and 2 and is branched in two directions. One branched in two directions is branched to a branch supply pipe 18 connected to the rare gas supply pipe 16, and the other is branched to a branch supply pipe 19 connected to the assist gas supply pipe 14. The branch supply pipes 18 and 19 are preferably provided with Xe branch valves (not shown) for opening and closing the flow paths.

  The analysis pipe 141 connected to the QMS 143 is preferably connected to the main pipe 134 at a position closer to the exhaust side 123 of the vacuum pump 121 than the branch pipe 131 through the analysis pipe valve 142. By arranging the QMS 143 in this way, it becomes possible to perform the valve operation based on the gas analysis result before the gas at the time of analysis reaches the branch valve 135 and the main piping valve 138 described later.

  Although not shown in the figure, when the three-component gas separation is performed by the chromatographic separation means 102, the number of branch pipes branched from the main pipe 134 is increased from two to three in the pipe configuration of the chromatographic separation apparatus 31. Is preferred. In this case, a branch valve is provided with a hardly adsorbable gas (for example, a two-component hardly adsorbable gas (for example, PFC gas and CO gas)) and Xe gas separated by a column 111 (for example, column 111A) in each branch pipe. It is also preferable to distribute and flow by the above operation. On the other hand, the main pipe 134 is preferably connected to the supply pipe 212B of the next gas separation means 102, and the mixed gas of Xe gas and other gas that has not been separated is preferably flowed together with the unseparated exhaust gas. By configuring each pipe in this way, each hardly adsorbable gas and Xe gas can be individually discharged from each branch pipe. Further, the mixed gas of the Xe gas and the other gas that has not been separated flowing through the main pipe 134 as described above is sent to the next column 111 (for example, the column 111B) to again separate the Xe gas. be able to. It is preferable that the gas type flowing through each pipe is determined by the valve operation of each pipe based on the analysis result of the QMS 143. In the chromatographic separation apparatus 31 having a piping configuration that sends a mixed gas of Xe gas and other gas that has not been separated to the next column as described above, Xe is reduced to approximately 100% by mass without discarding the Xe gas. Separation and recovery to near purity becomes possible.

The branch pipes 131 and 132 are preferably arranged from the vacuum pump 121 side in the order of the types of gas flowing from the vacuum pump 121.
By arranging the branch pipe 131 in this way, it is possible to prevent the hardly adsorbing gas from entering the main pipe 134 of the recovery system.
In order to prevent gas from being left in the main pipe 134, it is preferable to arrange a vacuum pump in the branch pipes 131 and 132 on the downstream side of the branch valves 135 and 136, although not shown.

First, supply of exhaust gas to the four gas separation means 102A to 102D will be described.
Keep all valves closed. When the operation starts, the supply valve 214 for supplying the exhaust gas to the column 111 (111A) and the branch valve 135 of the hardly adsorbing gas system are opened. At the same time, when the vacuum pump 121 (121A) is operated, exhaust gas is supplied to the column 111A from the supply pipe 212 (212A), and the gas separation means 102 (102A) performs chromatographic separation of the exhaust gas.

  The exhaust gas is supplied to each of the gas separation means 102A to 102D in the order of the gas separation means 102A to 102D by opening and closing the supply valve 214 as described above for a predetermined time. In each gas separation means 102A to 102D, the supply valve 214 is opened, and then the branch valve 135 of each gas separation means 102A to 102D is opened. In this way, exhaust gas is sequentially supplied to each of the gas separation means 102A to 102D. And after supplying exhaust gas to gas separation means 102D, continuous gas separation of exhaust gas can be performed by supplying exhaust gas again sequentially from gas separation means 102A.

  Next, each valve operation will be specifically described. First, all the branch valves 135 and 136 and the main piping valve 138 are closed. In this state, the vacuum pump 121 is operated, the supply valve 214 is opened, the branch valve 135 is opened, exhaust gas is introduced into the column 111 of each gas separation means 102, and exhaust gas is chromatographed. The exhaust gas supplied to the column 111 passes through the column 111, the hardly adsorbing PFC gas is discharged first, and is discharged (or recovered) through the opened branch valve 135 and branch pipe 131 of the exhaust system. The column 111 is exhausted while the hardly adsorbable PFC gas is discharged from the column 111 by the analysis of the QMS 143. When the hardly adsorptive PFC gas is no longer discharged from the column 111 by the analysis of the QMS 143, the branch valve 135 is closed, the branch valve 136 is opened, and the Xe gas is recovered from the branch pipe 132. When the Xe gas is no longer detected by the analysis of the QMS 143, the branch pipe valve 136 is closed. Thus, the chromatographic separation of one gas separation means 102 is completed. Thereafter, the exhaust gas is supplied again to the column 111, and the same gas separation process as described above is performed. In the case of the present embodiment, the PFC gas is substantially removed by the adsorption device 23 (see FIGS. 1 and 2), and is, for example, 0.05% by mass or less. Therefore, the hardly adsorbable PFC gas passing through the column 111 is relatively The peak is also narrow. Therefore, it becomes easy to collect | recover only noble gas from the branch piping 132, and the purity of the collect | recovered Xe gas can be 99.999 mass% or more. Thus, when it can isolate | separate into 2 components with the column 111, gas separation is performed with 2 piping. Therefore, the main piping valve 138 of the main piping 134 is always closed.

When Xe gas starts to be discharged from the column 111 while the hardly adsorbing PFC gas is discharged, the gas discharged from the column 111 becomes a mixed gas of the hardly adsorbing PFC gas and the Xe gas. When such a mixed gas is discharged, when the Xe gas is detected by the QMS 143, the branch valve 135 is closed and then the main piping valve 138 is opened. Then, the mixed gas is recovered from the main pipe 134. Thereafter, when the QMS 143 no longer detects the non-adsorbing PFC gas, the main piping valve 138 is closed and then the branch piping valve 136 is opened. Then, Xe gas is recovered from the branch piping valve 132. Thereafter, when the QMS 143 no longer detects Xe gas, the branch valve 136 is closed.
Furthermore, it is preferable to connect the main pipe 134 of the column 111A to the supply pipe 212B of the next column 111B. Accordingly, the mixed gas recovered through the main pipe 134 can be supplied to the column 111B through the supply pipe 212B together with the exhaust gas newly supplied to the supply pipe 212B. Then, Xe gas can be separated and recovered again by the column 111B.

  As described above, the chromatographic separation device 31 can sequentially perform the chromatographic separation process by sequentially supplying the exhaust gas from the exhaust gas supply source supply pipes 212A to 212D to the columns 111A to 111D. Therefore, exhaust gas chromatographic separation can be performed efficiently.

In each of the above embodiments, the Xe gas is used as the rare gas. However, even if Kr gas is used as the rare gas, the same processing as that of the Xe gas can be performed, and the same effect can be obtained.
In each of the above embodiments, a dry etching apparatus has been described as a semiconductor wafer processing apparatus. However, for a thin film forming apparatus (for example, a chemical vapor deposition apparatus), the exhaust gas includes a rare gas, water, and a PFC gas. For example, the same effect as that of the dry etching apparatus can be obtained.

The exhaust gas includes PFC gas, carbon dioxide gas, CO gas, HF gas, rare gas, and water. Examples of the PFC gas include carbon tetrafluoride (CF ₄ ) gas, C ₄ F ₆ gas, C ₄ F ₈ gas, and C ₅ F ₈ gas. Moreover, Xe gas or Kr gas is mentioned as a noble gas.

  In the second embodiment, the exhaust gas supply time to the column 111 is 5 minutes, and the time from the start of exhaust gas supply to the end of rare gas discharge is 20 minutes. It is appropriately changed depending on the column size, length, packing amount of the packing material, and the like. In order to treat exhaust gas continuously, the exhaust gas supply time Ts, the time from the start of exhaust gas supply until the end of Xe gas discharge is Tg, the number of columns is N, and the number of Tg / Ts = N It is preferable to determine Tg and Ts so that By doing so, it is possible to perform continuous chromatographic separation without interrupting the supply of exhaust gas to the column 111.

DESCRIPTION OF SYMBOLS 1, 1A, 1B Gas separation apparatus 11 Semiconductor wafer processing apparatus 11B Gas discharge side 12 Transfer piping 13 PFC gas supply piping 14 Assist gas supply piping 15 Vacuum pump 15A Suction side 15B Exhaust side 16 Noble gas supply piping 17 Recovery rare gas supply piping 18, 19 Branch supply pipe 21 Noble gas recovery device 22 Moisture removal device 23 Detoxification device 24, 25 Pipe 102, 102A-102D Gas separation means 111, 111A-111D Column 112 Inlet 113 Outlet 121, 121A-121D Vacuum pump 122 Suction Side 123 Exhaust side 131, 132 Branch piping 134 Main piping 135, 136 Branch valve 138 Main piping valve 141 Analysis piping 142 Analysis piping valve 143 QMS
211 Exhaust gas supply source 212, 212A to 212D Supply piping 214 Supply valve

Claims (10)

A transfer pipe for transferring an exhaust gas containing at least a rare gas discharged from the semiconductor wafer processing apparatus;
A rare gas supply pipe connected to the carrier pipe and introducing the same kind of rare gas as the rare gas into the carrier pipe;
A gas separation device having a rare gas recovery device connected to the transfer pipe and removing a gas component other than the rare gas contained in the exhaust gas to recover the rare gas.   The rare gas recovery device is any one of a water removal device, a plasma abatement device, a dry abatement device, an adsorption abatement device, a pressure swing adsorption device, a temperature swing adsorption device, a chromatographic separation device, and a membrane separation device or The gas separation device according to claim 1, comprising a combination of these.   The noble gas recovery device is connected to the moisture removal device for removing moisture from the exhaust gas, and a discharge side of the moisture removal device, and removes perfluoro compound gas and acid gas from the gas discharged from the moisture removal device. The gas separation device according to claim 2, further comprising the adsorption detoxifying device to be removed.   The gas separation device according to claim 3, further comprising a chromatographic separation device connected to a discharge side of the adsorption detoxification device and collecting the rare gas by chromatographic separation of the gas discharged from the adsorption detoxification device.   The gas separation device according to claim 4, wherein the chromatographic separation device includes a plurality of chromatographic columns, and each chromatographic column performs chromatographic separation at different timings.   The gas separation device according to any one of claims 1 to 5, wherein the rare gas is xenon gas. A gas separation method for recovering a rare gas from an exhaust gas containing at least a rare gas discharged from a semiconductor wafer processing step,
Introducing a rare gas of the same type as the rare gas discharged from the semiconductor wafer processing step into the exhaust gas;
A step of transferring exhaust gas into which the same kind of rare gas is introduced;
A gas separation method including a removal and recovery step of recovering the rare gas after removing gas components other than the rare gas from the exhaust gas into which the rare gas has been introduced.   The removal and recovery step is any one of a water removal step, a plasma removal step, a dry removal step, an adsorption removal step, a pressure swing adsorption step, a temperature swing adsorption step, a chromatographic separation step, and a membrane separation step or The gas separation method according to claim 7, comprising a combination of these. The exhaust gas contains perfluoro compound gas, acid gas, noble gas and water,
The said removal collection process has a water removal process which removes the said water, and an adsorption detoxification process which removes the said perfluoro compound gas and the said acidic gas from the waste gas discharged | emitted from the said water removal process. Gas separation method.   The gas separation method according to claim 9, further comprising a chromatographic separation step of recovering a rare gas by chromatographic separation of the gas discharged from the adsorption detoxification step after the adsorption detoxification step.

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