JP3553310B2 - Evacuation system - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vacuum exhaust system used to evacuate a vacuum chamber of a semiconductor manufacturing apparatus or the like.
[0002]
[Prior art]
A conventional evacuation system will be described with reference to FIG. Here, the vacuum chamber 101 is a process chamber used for a semiconductor manufacturing process such as an etching apparatus or a chemical vapor deposition apparatus (CVD). The vacuum chamber 101 is connected to a vacuum pump 103 through a pipe 102. The vacuum pump 103 is for raising the pressure of the exhaust gas of the process from the vacuum chamber 101 to the atmospheric pressure. Conventionally, an oil rotary pump is used, and at present, a dry pump is mainly used.
[0003]
When the degree of vacuum required by the vacuum chamber 101 is higher than the ultimate degree of vacuum of the dry pump 103, an ultra-high vacuum pump such as a turbo molecular pump may be further arranged upstream of the dry pump. Exhaust gas from the process cannot be released to the atmosphere as it is because it is toxic or explosive depending on the type of process. Therefore, an exhaust gas treatment device 104 is provided downstream of the vacuum pump 103. Among the exhaust gas of the process whose pressure has been increased to the atmospheric pressure, those which cannot be released to the atmosphere as described above are subjected to treatments such as adsorption, decomposition, absorption and the like, and only harmless gases are released to the atmosphere. The pipe 102 is provided with a valve at an appropriate position as needed.
[0004]
[Problems to be solved by the invention]
By the way, for example, PFC (Perfluorocarbon) gas such as CF ₄ or C ₂ F ₆ used in a semiconductor manufacturing process is harmless to the human body, but harmful to the global environment (has a high global warming potential). Therefore, it is desired to prevent the release to the atmosphere by some means. However, in the conventional evacuation system as described above, the PFC gas cannot be processed by the exhaust gas treatment device and is discharged into the atmosphere, and it has not been possible to meet this demand.
[0005]
In order to dilute the reaction by-products in the vacuum pump so as not to be solidified, an inert gas such as N ₂ gas is injected into the pump as a purge gas, but this N ₂ gas is also discharged to the atmosphere as it is. Therefore, it is not desirable from the viewpoint of energy saving.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents the emission of gases such as PFC into the atmosphere, saves purging gas, protects the environment, improves the reliability and safety of operation, and furthermore, An object of the present invention is to provide a vacuum evacuation system capable of reducing equipment and operation costs.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 includes a vacuum chamber using a PFC gas as a process gas, a vacuum pump for exhausting the vacuum chamber, an exhaust gas treatment device disposed downstream of the vacuum pump, and an exhaust gas treatment device. A gas storage unit disposed further downstream to store the PFC gas that could not be processed by the exhaust gas processing apparatus.
[0008]
Thereby, for example, PFC gas contained in the exhaust gas which cannot be processed by the exhaust gas treatment device is stored in the gas storage unit to prevent the release into the atmosphere, and furthermore, purify the same and promote its reuse. be able to.
[0009]
The vacuum chamber is, for example, a process chamber for a semiconductor manufacturing apparatus in which a PFC gas such as CF ₄ or C ₂ F ₆ flows. As the vacuum pump, it is preferable to use a dry pump that does not use lubricating oil in order to prevent contamination of the chamber due to back diffusion by oil. As the gas storage unit, a compression container such as a cylinder, a storage unit that is condensed and stored at a low temperature, or a storage unit such as a porous gas absorber is used.
[0010]
The invention according to claim 2 is the vacuum evacuation system according to claim 1, wherein the gas storage unit traps the PFC gas at a low temperature. As a result, a large amount of gas can be stored by effectively utilizing the narrow space, and it is easy to regenerate by heating.
[0013]
According to a third aspect of the present invention, there is provided a vacuum chamber using a PFC gas as a process gas, a vacuum pump for exhausting the vacuum chamber, and a PFC gas discharged from the vacuum pump for collecting and purging in the vacuum pump. A vacuum gas circulating line for purging gas returned as gas. This makes it possible to reuse a PFC gas or the like that is difficult to process as a pump purge gas, thereby reducing the processing cost and saving the purge gas.
According to a fourth aspect of the present invention, there is provided a vacuum chamber using a PFC gas as a process gas, a vacuum pump for exhausting the vacuum chamber, and gasification of only the PFC from a liquefied gas discharged from the vacuum pump and collected. A vacuum exhaust system comprising: a regenerating unit for regenerating PFC gas regenerated by the regenerating unit; and a circulating line for a source gas for returning the PFC gas regenerated as the source gas into the vacuum chamber.
The invention according to claim 5 is the vacuum exhaust system according to claim 3 or 4, wherein the PFC gas that has passed through an exhaust gas treatment device disposed downstream of the vacuum pump is recovered. .
The invention according to claim 6 is characterized in that a gas storage unit for storing PFC gas that cannot be treated by the exhaust gas treatment device is disposed downstream of the exhaust gas treatment device. System.
The invention according to claim 7 is the vacuum exhaust system according to claim 6, wherein a compressor for promoting storage of the PFC gas in the gas storage unit is provided downstream of the exhaust gas treatment device. .
[0014]
The invention according to claim 8 is the vacuum exhaust system according to any one of claims 3 to 7, wherein a compressor for pressurizing PFC gas is provided in the circulation line.
The invention according to claim 9 is the vacuum exhaust system according to any one of claims 3 to 9, wherein a dehumidifier is provided in the circulation line.
The invention described in claim 10 is the vacuum exhaust system according to any one of claims 3 to 9, wherein a filter for removing solid matter is provided in the circulation line.
According to an eleventh aspect of the present invention, a gas storage unit for storing a PFC gas is disposed downstream of the vacuum pump, and a PFC gas and / or a gas storage unit between the gas storage unit and the vacuum pump is provided. The vacuum evacuation system according to claim 3, wherein the stored PFC gas is recovered .
According to a twelfth aspect of the present invention, there is provided the vacuum evacuation system according to the eleventh aspect, wherein a compressor for promoting storage of the PFC gas in the gas storage unit is provided in front of the gas storage unit. .
The invention according to claim 13 is the vacuum exhaust system according to claim 11 or 12, wherein a compressor for pressurizing PFC gas is provided in the circulation line.
The invention according to claim 14 is the vacuum exhaust system according to any one of claims 11 to 13, wherein a dehumidifier is provided in the circulation line.
The invention described in claim 15 is the vacuum exhaust system according to any one of claims 11 to 14, wherein a filter is provided in the circulation line.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 10 denotes a chamber for performing processes such as film formation and etching in a semiconductor manufacturing process. Here, a PFC gas such as CF ₄ or C ₂ F ₆ is used as a process gas. A vacuum pump 14 is connected to the exhaust path 12 of the vacuum chamber 10, and an exhaust gas treatment device 16 is provided downstream of the vacuum pump 14. The vacuum pump 14 may be provided with an external purge gas line for supplying an inert gas such as N ₂ from the outside as a purge gas. Although the vacuum pump 14 has one stage in this example, it may have multiple stages.
[0016]
The exhaust gas treatment device 16 chemically or physically treats toxic components in the exhaust gas. For example, in dry etching of SiO ₂ using CF ₄ and O ₂ as process gases, CF ₄ , O ₂ , CO, CO ₂ , F ₂ , SiF _{4 and the} like are generated after the process. Of these, SiF ₄ and F ₂ are toxic and are treated by an exhaust gas treatment device, and CF ₄ , O ₂ , CO, and CO ₂ are discharged downstream of the exhaust gas treatment device 16. Downstream of the exhaust gas treatment device 16 is disposed a gas storage unit 18 for storing such components, particularly a stable gas such as PFC gas. As the gas storage unit 18, a high-pressure container such as a cylinder or a porous gas absorber is used.
[0017]
A purge gas circulation line is provided between the gas storage unit 18 and the vacuum pump 14 for returning PFC gas and the like accumulated in the gas storage unit 18 to the vacuum pump 14 and using the same as a purge gas for the pump 14. 20 are provided. The purge gas circulation line 20 is provided with a dehumidifier 22 and, if necessary, a pressure reducing valve (not shown).
[0018]
In the vacuum exhaust system having such a configuration, the exhaust gas including the PFC gas exhausted from the vacuum chamber 10 flows along the exhaust path 12 and flows into the exhaust gas treatment device 16, where many components are removed. It is transformed into a form that is harmless to humans and the environment. Components such as CF ₄ , O ₂ , CO, and CO ₂ that cannot be processed by the exhaust gas processing device are stored in the gas storage unit 18. In order to facilitate storage, a compressor may be further provided downstream of the abatement apparatus 16.
[0019]
These gases stored in the gas storage unit 18 are in a state in which impurities have been removed by the exhaust gas treatment device 16, and are therefore reused as a material gas when stored in the gas storage unit 18. You can also. In this way, it is possible to prevent a gas such as PFC contained in the exhaust gas, which has an adverse effect on the global environment, from being released into the atmosphere, and to recover and reuse the gas.
[0020]
Then, a part of the PFC gas or the like accumulated in the gas storage unit 18 is adjusted at a flow rate according to the fluid resistance of the dehumidifier 22 or by a flow rate regulating valve, so that the purge gas circulation line 20 and the dehumidifier 22 The components in the vacuum pump 14 are supplied to a portion on the exhaust side where the components are easily solidified. In particular, PFC gas is a chemically stable gas, does not precipitate or deteriorate even when the temperature or pressure changes, and is suitable for use as a purge gas for the vacuum pump 14.
[0021]
The purge gas supplied from the purge gas circulation line 20 is supplied to the vacuum pump 14 in a dry state with moisture removed by a dehumidifier 22. Therefore, the vacuum pump 14, the abatement apparatus 16, the gas storage unit 18 and the like are not adversely affected by moisture. Incidentally, by providing an external purge gas lines as necessary, it may be used in combination with other inert gas ₂ such future N. By thus reusing the PFC gas stored in the gas storage unit 18 as a purge gas, the time and effort for preparing another inert gas can be omitted or reduced.
[0022]
FIG. 2 shows a second embodiment of the present invention, in which a gas storage unit 24 traps and stores gas in a liquid or solid form using a low temperature. Here, it is liquefied for easy handling. That is, storage container 24a piping 24b for circulating the refrigerant of the liquefaction temperature below the predetermined temperature of the exhaust gas is provided in the bottom of the storage container 24a is accumulated regeneration vessel partially reproducing section 25 a of the liquefied gas A discharge line 24c is provided at 25.
[0023]
The regeneration vessel 25a is provided with a pipe 25b through which a heating medium having a temperature equal to or higher than the vaporization temperature of the gas to be regenerated is provided, and is connected to the circulation line 20 for guiding the regenerated gas to the vacuum pump 14 via the dehumidifier 22. The circulation line 20 may be provided with an opening / closing / flow rate adjusting valve, an extraction pump, a vaporization heater, and the like, as necessary.
[0024]
In the apparatus of this embodiment, CF ₄ (boiling point: 145 ° K), O ₂ (90 ° K), CO (82 ° K), and CO ₂ (195 ° K) are discharged downstream of the exhaust gas treatment device 16. The following describes an example of the case in which this is done. When the gas storage unit 24 is set to about 110 ° K by flowing liquefied nitrogen through the pipe 24b or using a helium refrigerator, CF ₄ and CO ₂ are trapped, and O ₂ and CO are released from a discharge port (not shown). You. A part of the liquefied CF ₄ and CO ₂ is led to the regeneration container 25a of the regeneration unit 25 via the discharge line 24c.
[0025]
The liquefied gas is regenerated at a temperature of 110 ° K or more in the regenerating section 25 and returned to the vacuum pump 14 from the gas circulation line 20 via the dehumidifier 22, so that it can be used as a purge gas.
[0026]
FIG. 3 shows still another embodiment of the present invention, in which a circulation line 20 connected to a vacuum pump 14 is provided in an exhaust path 12 between an exhaust gas treatment device 16 and a storage container 24a. The circulation line 20 is provided with a dehumidifier 22, a filter 26 for solid matter, and a compressor 28. As a result, a part of the PFC gas or the like that has passed through the exhaust gas treatment device 16 is branched into a circulation line, dehumidified and solid matter is removed, and supplied to the vacuum pump 14 as a purge gas. The accumulated liquefied gas is transferred to another container or the like via the discharge line 24c and collected.
[0027]
FIG. 4 shows a fourth embodiment of the present invention, in which a raw material circulation line 30 for guiding the regeneration container 25a of the apparatus of FIG. 2 to the vacuum chamber 10 via the dehumidifier 22 is connected. The raw material circulation line 30 may be provided with an opening / closing / flow rate adjusting valve, an extraction pump, a vaporization heater, and the like, as necessary. In such a configuration, only the CF ₄ is gasified and regenerated by regenerating the liquefied gas in the regenerating section 25 at about 170 ° K. Therefore, it is possible to effectively use a PFC gas that is difficult to treat as a raw material, to prevent an adverse effect on the environment, and to reduce the processing cost and the raw material cost.
[0028]
In the above, the operation of the embodiment of the present invention has been described by using the PFC gas as an example. However, the present invention is not limited to this, and the processing in the exhaust gas processing apparatus 16 is impossible or difficult. Any gas component may be used. Although only one storage unit is provided in the above description, two storage units may be provided so as to be switchable in parallel to enable continuous operation.
[0029]
For example, an exhaust gas component such as a PFC gas is not exhausted depending on the contents of processing in the vacuum chamber, but N ₂ gas is used as a purge gas of the vacuum pump 14. Such N ₂ gas is also inert and passes through the exhaust gas treatment device 16. This is not harmful even if released into the atmosphere, Kasami cost of N ₂ gas, raising the cost of the process. Therefore, the apparatus of the embodiment shown in FIGS. 1 to 3 may be used for N ₂ gas. In this case also, the steps are essentially the same except for the liquefaction temperature and the like, and detailed description is omitted.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent a gas, such as PFC gas, which is difficult to treat by an exhaust gas treatment device and has a bad influence on the global environment from being released into the atmosphere. . Further, by reusing the PFC gas or the like stored in the gas storage unit as a purge gas for a vacuum pump or as a high-purity material gas, it is possible to save energy and reduce operation costs.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of a vacuum evacuation system according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a structure of a vacuum evacuation system according to a second embodiment of the present invention.
FIG. 3 is a diagram showing a structure of a vacuum evacuation system according to a third embodiment of the present invention.
FIG. 4 is a diagram showing a structure of an evacuation system according to a fourth embodiment of the present invention.
FIG. 5 is a diagram showing a structure of a conventional evacuation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Vacuum chamber 12 Exhaust path 14 Vacuum pump 16 Exhaust gas treatment device 18 Gas storage unit 20 Purging gas circulation line 22 Dehumidifier 24 Gas storage unit 30 Raw material gas circulation line

Claims (15)

A vacuum chamber using PFC gas as a process gas ;
A vacuum pump that evacuates the vacuum chamber;
An exhaust gas treatment device disposed downstream of the vacuum pump;
A gas storage unit that is disposed further downstream of the exhaust gas treatment device and stores PFC gas that cannot be treated by the exhaust gas treatment device. The vacuum exhaust system according to claim 1, wherein the gas storage unit traps the PFC gas at a low temperature. A vacuum chamber using PFC gas as a process gas ;
A vacuum pump that evacuates the vacuum chamber;
A vacuum gas circulating line for collecting a PFC gas discharged from the vacuum pump and returning the gas to the vacuum pump as a purge gas. A vacuum chamber using PFC gas as a process gas ;
A vacuum pump that evacuates the vacuum chamber;
A regeneration unit that gasifies and reproduces only PFC from the liquefied gas discharged from the vacuum pump and liquefied and collected;
An evacuation system comprising: a source gas circulation line that returns the PFC gas regenerated by the regenerating unit as the source gas into the vacuum chamber. The vacuum exhaust system according to claim 3, wherein PFC gas that has passed through an exhaust gas treatment device disposed downstream of the vacuum pump is recovered. The vacuum exhaust system according to claim 5, wherein a gas storage unit that stores PFC gas that cannot be processed by the exhaust gas processing device is disposed downstream of the exhaust gas processing device. The vacuum exhaust system according to claim 6, wherein a compressor that promotes storage of the PFC gas in the gas storage unit is provided at a subsequent stage of the exhaust gas treatment device. The vacuum exhaust system according to any one of claims 3 to 7, wherein a compressor for pressurizing the PFC gas is provided in the circulation line. The vacuum exhaust system according to any one of claims 3 to 8, wherein a dehumidifier is provided in the circulation line. The vacuum exhaust system according to any one of claims 3 to 9, wherein a filter is provided in the circulation line. A gas storage unit for storing a PFC gas is disposed downstream of the vacuum pump, and a PFC gas between the gas storage unit and the vacuum pump and / or a PFC gas stored in the gas storage unit is collected. The vacuum evacuation system according to claim 3 or 4, wherein: The vacuum evacuation system according to claim 11, wherein a compressor that promotes storage of PFC gas in the gas storage unit is provided before the gas storage unit. The vacuum exhaust system according to claim 11, wherein a compressor for pressurizing the PFC gas is provided in the circulation line. 14. The vacuum exhaust system according to claim 11, wherein a dehumidifier is provided in the circulation line. The vacuum evacuation system according to any one of claims 11 to 14, wherein a filter is provided in the circulation line.

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