Method and apparatus for removing active particles from vacuum environment, process system for manufacturing monocrystalline silicon ingots

Abstract

A method for removing active particles from a vacuum environment (14) in which a process gas is conveyed from the vacuum environment (14) by means of a vacuum pump (21, 22). A process gas is conducted between a vacuum environment (14) and a vacuum pump (21, 22) through a first filter (31) and a second filter (32) in order to filter active particles from the process gas. Particles are discharged from the first filter (31) and the second filter (32) by means of a liquid ring pump (35). In a first stage of the method, the first filter (31) is active and the second filter (32) is passive, and in a second stage of the method, the first filter (31) is passive and the second filter (32) is active. In a first stage, a process gas is conducted through a first filter (31) and a liquid ring pump (35) discharges particles from a second filter (32). In a second stage, the process gas is conducted through the second filter (32), and the liquid ring pump (35) discharges particles from the first filter (31). The invention further relates to a device for removing active particles from a vacuum environment and to a process system for producing monocrystalline silicon ingots.

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for removing active particles from a vacuum environment. The present invention also relates to a process system for manufacturing a single crystal silicon ingot. Background Art

[0002] In a process system from which process gas is discharged, there is often a need to remove active particles from a vacuum environment. An example is the production of a single crystal silicon ingot formed from a silicon melt. The silicon melt is disposed in a vacuum chamber, and argon is introduced into the vacuum chamber as a purge gas. During the formation of the silicon ingot, a continuous flow of process gas is generated in such a way that argon is continuously introduced into the chamber and is withdrawn from the vacuum chamber by a vacuum pump.

[0003] The process gas contacts the silicon ingot, the silicon melt, and other surfaces in the vacuum chamber and thereby carries active particles when leaving the vacuum chamber.

[0004] Hitherto, it has been common to accumulate the active particles in a filter disposed between the vacuum chamber and the vacuum pump until the formation of the silicon ingot is completed. Removing the silicon ingot from the vacuum chamber or renewing the stage where the silicon melt is located can be used to clean the filter and remove the active particles.

[0005] If a large amount of active particles accumulates in the filter, problems may occur when cleaning the filter. For example, dust agglomerates may form, which cannot be eliminated by simple purging. In addition, a chemical reaction may be triggered by the contact of the active particles with oxygen, in which heat energy is released. In the case of a large amount of active particles, the heat released will become so large that the filter will be damaged. Summary of the Invention

[0006] The object underlying the present invention is to provide a method and an apparatus for removing active particles from a vacuum environment and an associated process system with which these disadvantages can be avoided. This object is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0007] The subject matter of the present invention is a method for removing active particles from a vacuum environment, wherein process gas is conveyed from the vacuum environment by means of a vacuum pump, and wherein the process gas is guided between the vacuum environment and the vacuum pump through a first filter and a second filter in order to filter the active particles from the process gas. The particles are discharged from the first filter and the second filter by means of a liquid ring pump. In a first stage of the method, the first filter is active and the second filter is passive. In a second stage of the method, the first filter is passive and the second filter is active. In the first stage, the process gas is guided through the first filter, and the liquid ring pump discharges the particles from the second filter. In the second stage, the process gas is guided through the second filter, and the liquid ring pump discharges the particles from the first filter.

[0008] By alternately using two parallel filters between the vacuum environment and the vacuum pump, it is possible to determine the cleaning time points of the filters independently of the process in the vacuum housing. While one of the filters is in the active state and filters the active particles from the process gas conveyed by the vacuum pump, the other filter can be brought into the passive state, in which it does not contribute to the operation in the vacuum housing. In the passive state, the active particles can be discharged from the filter by means of a liquid ring pump. By means of the alternating operation in which one of the filters is accordingly active and the other filter is passive, the process gas can be continuously conveyed from the vacuum environment without an excessive accumulation of active particles in one of the filters.

[0009] The method is preferably carried out such that the process gas is continuously conveyed from the vacuum environment between the first stage and the second stage. One or more transition stages can exist between the first stage of the method and the second stage of the method. The transition stage can include a section in which the process gas is guided not only through the first filter but also through the second filter in parallel. The time period required to discharge the particles from the passive filter can be shorter than the time period for filtering the process gas with the active filter. The transition stage can then include a section in which the passive filter is completely deactivated, i.e., it is neither used for filtering the process gas nor for cleaning.

[0010] The first filter can be designed to filter the active particles from the process gas by guiding the process gas through a filter material on which the active particles are deposited. The filter material can in particular be a porous material. The primary filter chamber and the secondary filter chamber can be separated by the filter material. The process gas from the vacuum environment can be introduced into the primary filter chamber and pass through the porous material into the secondary filter chamber. The filtered process gas can be discharged from the secondary filter chamber by means of a vacuum pump.

[0011] The porous material can form a tubular structure. The outside of the tubular structure can be adjacent to the primary filtration chamber, and the inside of the tubular structure can be adjacent to the secondary filtration chamber. The tubular structure can be vertically oriented. The first end of the tubular structure can be closed, and the second end of the tubular structure can be open. The second end can communicate with the secondary filtration chamber. The second end can be the upper end of the tubular structure. The second filter can have the same characteristics as the first filter.

[0012] During the filtration of the process gas using the active filter, a vacuum is applied in the active filter. After transitioning to the passive state, oxygen-containing gas can be introduced into the passive filter during a first transition phase, so that the pressure in the passive filter increases. In one embodiment, ambient air is introduced into the passive filter to bring the passive filter to atmospheric pressure. Compressed air with a pressure higher than atmospheric pressure can also be introduced into the passive filter, or a gas with an oxygen content higher than that of air can be introduced into the passive filter. For this purpose, the filter can include a ventilation valve that opens to allow gas to enter and closes in the active state of the filter. The entry of the gas can occur at the beginning of the passive state of the filter, i.e., before the particles are discharged from the filter using a liquid ring pump.

[0013] The entry of the gas causes a chemical reaction, in particular between the active particles and oxygen, in which heat energy is released. The active particles at least partially lose their activity, thus reducing the risk of ignition or explosion.

[0014] The oxygen-containing gas used to fill the interior space of the passive filter can enter the secondary filtration chamber. In this way, a countercurrent can be generated through the filter material, which is opposite to the flow direction that the process gas has in the active state of the filter. The countercurrent can extend from the secondary filtration chamber through the filter material into the primary filtration chamber. The ventilation valve can be quickly opened, thus generating a sudden flow into the interior space of the passive filter. The particles that have been deposited at the filter material are separated by the countercurrent. At the same time, the active particles can react (abreagieren) through strong contact with the incoming gas, thereby reducing the activity of the particles. The particles separated from the porous material are first distributed in the primary filtration chamber and then sink to the bottom.

[0015] The liquid ring pump can be connected to the lower section of the first filter and / or the second filter, so that the liquid ring pump can be used to discharge the particles accumulated there. The liquid ring pump can be connected to the primary filtration chamber of the first filter and / or the second filter. The bottoms of the first filter and the second filter can be configured as inclined planes to guide the particles to the connection of the liquid ring pump. The connection of the liquid ring pump can be arranged at the lower end of the inclined plane. During the discharge of particles from the passive filter, free air exchange can exist between the internal space of the passive filter and the surrounding environment, thus avoiding a vacuum in the internal space of the passive filter.

[0016] If the particles accumulated at the bottom of the passive filter are put into a fluidized state, the discharge of particles from the passive filter can be made easier. A fluidizing device can be provided to introduce a fluidizing gas stream into the accumulated particles.

[0017] The particles discharged towards the liquid ring pump are mixed with the operating liquid forming the liquid ring inside the liquid ring pump. The chemical reaction between the particles and the operating liquid can help to further reduce the activity of the particles. The particles can be discharged from the liquid ring pump together with the operating liquid of the liquid ring pump. The operating liquid can be replaced during the operation of the liquid ring pump, so that the operating liquid with a higher particle proportion is discharged from the liquid ring pump and the operating liquid with a lower particle proportion is supplied to the liquid ring pump.

[0018] The replacement of the operating liquid can be carried out continuously during the operation of the liquid ring pump. The operating liquid can be water. Fresh water or treated water can be supplied to the liquid ring pump. It is also feasible that the particles accumulate in the operating liquid until a pre-given concentration is reached and the operating liquid is replaced when the concentration is reached.

[0019] The feature "liquid ring pump" in the sense of the present invention does not include a limitation in terms of the number of structural units. The liquid ring pump according to the present invention can be composed of two structural units, so that the first structural unit is connected to the first filter and the second structural unit is connected to the second filter. Preferably, the liquid ring pump is implemented as a single structural unit that communicates alternately with the first filter and the second filter.

[0020] The gas transported by the liquid ring pump can be collected or discharged to the surrounding environment. The gas can contain active gaseous components, such as hydrogen for example. In order to avoid danger, after leaving the liquid ring pump, the gas can be diluted by supplying air, for example, until the concentration of combustible substances in the gas is lower than the lower explosion limit (UEG).

[0021] After the removal of the granules, in a second transition phase, the passive filter can be prepared for transition into the active state. To this end, the connection between the interior space of the passive filter and the liquid ring pump can be closed. The ventilation valve can likewise be closed, through which the interior space of the passive filter communicates with the surroundings. A vacuum can be applied in the interior space of the passive filter, which vacuum corresponds to the vacuum in the interior space of the active filter. Once the same pressure is applied in both filters, the hitherto passive filter can be connected into the process gas flow between the vacuum housing and the vacuum pump. After this has been achieved, the hitherto active filter can be separated from the process gas flow between the vacuum housing and the vacuum pump, so that the hitherto active filter transitions into the passive state.

[0022] The cleaning interval, i.e. the time period for which the filter operates in the active state, can be determined based on the state of the active filter. The criterion can be, for example, that the pressure difference between the primary filtration chamber and the secondary filtration chamber exceeds a pre-given threshold. A high pressure difference can indicate a sign that a certain amount of active particles has been deposited in the filter. As an additional or alternative solution, a certain amount of active particles in the active filter can be deduced from the weight of the active filter, and a transition to the passive state can be made when a pre-given threshold of the weight is exceeded. In a further variant, a transition from the active state to the passive state is made after a pre-given time period has elapsed.

[0023] Before the transition into the active state, the passive filter can be evacuated using the same vacuum pump that also generates the vacuum for the vacuum environment. This mode of operation can have a negative impact on the process stability in the vacuum environment, since pressure fluctuations in the vacuum environment can occur when the passive filter is evacuated. Therefore, in one embodiment, an auxiliary vacuum pump is provided, using which the passive filter is evacuated before the transition into the active state.

[0024] The auxiliary vacuum pump can have an additional function, namely to evacuate the lock chamber through which an object is introduced into the vacuum environment or removed from the vacuum environment. Before the transfer of an object between the vacuum environment and the lock chamber, the lock chamber is evacuated to the same pressure as that applied in the vacuum environment. This is also the pressure to which the passive filter is brought before the transition into the active state, so that the same requirements apply to the auxiliary vacuum pump in both cases.

[0025] It is possible to supply the process gas conveyed by the (main) vacuum pump to a treatment station, where the process gas is treated such that it is suitable for reuse in a vacuum environment. In particular, argon can be regenerated from the process gas in the treatment station and provided for reuse. A connection line can exist between the treatment station and the vacuum environment, so that the treated process gas is led back to the vacuum environment in a closed loop.

[0026] The feature "vacuum pump" in the sense of the present invention does not imply a limitation with respect to the number of structural units. The vacuum pump according to the present invention can consist of two structural units, such that the first structural unit is connected to the first filter and the second structural unit is connected to the second filter. Preferably, the vacuum pump is implemented as a single structural unit that alternately communicates with the first filter and the second filter.

[0027] In one embodiment, the vacuum pump according to the present invention is designed as a series configuration of two successively connected vacuum pump - structural units. The inlet of the second vacuum pump - structural unit can be connected to the outlet of the first vacuum pump - structural unit, such that only a part of the pressure difference between the vacuum environment and the atmospheric pressure is exerted by each of the vacuum pump - structural units in the vacuum pump - structural units. In this way, the energy efficiency of the vacuum pump can be improved.

[0028] To avoid contamination of the process gas by the operating liquid or lubricant of the vacuum pump, the vacuum pump is preferably constructed as a dry - running vacuum pump. In a preferred embodiment, the vacuum pump is a scroll pump. The same can apply to the auxiliary vacuum pump and / or the vacuum pump - structural unit.

[0029] The present invention also relates to a device for removing active particles from a vacuum environment, the device having a vacuum housing and a vacuum pump connected to the vacuum housing. A first filter and a second filter are arranged between the vacuum housing and the vacuum pump in order to filter active particles from the process gas conveyed by the vacuum pump. The device includes a liquid ring pump for extracting particles from the first filter and the second filter. The device is brought into a first switching state and a second switching state by means of a switching device, such that in the first switching state the process gas is guided through the first filter and the liquid ring pump discharges particles from the second filter, and in the second switching state the process gas is guided through the second filter and the liquid ring pump extracts particles from the first filter.

[0030] The invention furthermore relates to a process system having a vacuum housing and a device according to the invention coupled to the vacuum housing for removing active particles from the vacuum environment of the vacuum housing. The process system can include a lock chamber for introducing an object into and / or removing an object from the vacuum housing. The process system can include an auxiliary vacuum pump designed to evacuate the lock chamber and designed to evacuate the passive filter before transitioning to the active state. The process system can include a closed process gas circuit that extends from the vacuum housing through a vacuum pump to a process gas treatment station and returns from the process gas treatment station to the vacuum housing.

[0031] The process system can be designed for manufacturing single crystal ingots. A melting furnace can be arranged in the vacuum housing, and the silicon melt is produced by using the melting furnace. The lock chamber can be designed for introducing a silicon core into the vacuum housing and removing the finished silicon ingot from the vacuum housing. The invention also relates to a method for operating such a process system.

[0032] The present disclosure includes improvements to the devices and process systems described in connection with the method according to the invention. The present disclosure includes improvements to the methods described in connection with the device according to the invention or the process system according to the invention. Description of the Drawings

[0033] The invention will be described below by way of example with reference to the accompanying drawings according to advantageous embodiments. Among them: Figure 1 A first embodiment of a process system according to the invention is shown, Figure 2 is shown in an enlarged view of the filter from Figure 1 of, Figure 3 A second embodiment of a process system according to the invention is shown. Detailed Description

[0034] Figure 1 The process system shown in includes a vacuum housing 14, in which a vacuum is applied by a system consisting of a first screw pump 21 and a second screw pump 22. The system consisting of the screw pumps 21, 22 forms a vacuum pump in the sense of the present invention. The screw pump 21 obtains information about the pressure in the vacuum housing 14 from a first pressure sensor 41, so that a predetermined pressure can be generated in the vacuum housing 14 during regulated operation. A crucible 16 made of ceramic material is arranged in the vacuum housing 14, and the crucible is open upward. The crucible 16 is surrounded by a heating device 17, so that a silicon melt 18 can be provided in the crucible 16.

[0035] The process system includes a lock chamber 19 into which a silicon seed crystal is introduced at atmospheric pressure. After closing the lock chamber 19, a vacuum is created in the lock chamber 19 using a third vacuum pump 20. The third vacuum pump 20, which constitutes an auxiliary vacuum pump in the sense of the present invention, obtains information about the pressure in the lock chamber 19 from a second pressure sensor 38, so that a pre-given pressure can be generated in the lock chamber 19 during regulated operation. Once the pressure in the lock chamber 19 is equal to the pressure in the vacuum housing 14, the lock chamber 19 is opened towards the vacuum housing 14. The seed crystal is lowered at the wire until it contacts the surface of the melt 18. When the wire is slowly pulled back, silicon material from the melt 18 is deposited at the seed crystal, thereby producing a silicon ingot 15. The finished silicon ingot is transferred into the lock chamber 19. The lock chamber 19 is separated from the vacuum housing 14, the valve 40 is closed and the lock chamber 19 is placed under atmospheric pressure again, so that the silicon ingot 15 can be removed.

[0036] Argon is continuously introduced as a process gas into the vacuum housing 14 from an argon reservoir 39. The argon acts as a purge gas through which interfering particles and other components of the atmosphere are discharged from the vacuum housing 14. When the interfering particles react with oxygen as they come out of the melt, the interfering particles appear, for example, in the form of silicon oxide. The presence of oxygen in the vacuum environment cannot be completely prevented, for example, due to gas evolution from the components in the vacuum housing 14.

[0037] The melt may contain materials for doping the silicon ingot. In the case of an N-type doped single crystal, for example, red phosphorus is regarded as the doping material. Highly reactive dust may form from the red phosphorus, which interferes with the formation of the silicon ingot.

[0038] The active particles are received and discharged from the vacuum housing 14 by an argon purge gas flow maintained by the spiral pumps 21, 22. Before the argon purge reaches the first spiral pump 21, the enriched argon purge gas is used to remove the active particles by the device according to the present invention.

[0039] For this purpose, a first filter 31 and a second filter 32 are arranged between the vacuum housing 14 and the first spiral pump 21. The filters 31, 32 are parallel to each other, so that the process gas can pass through the first filter 31 or through the second filter 32. This enables the following feasible solution, i.e., bringing one of the two filters 31, 32 into a passive state in which the corresponding filter can be cleaned. The valves 23, 24, 25, 26, 27, 28, 29, 30, 33, 34, 44 are controlled by a control unit 57 so that these valves respectively assume the desired states. The control unit 57 forms a switching device in the sense of the present invention.

[0040] In the first stage of the operating cycle, the first filter 31 is active and the second filter 32 is passive. Valves 27, 37 are open, while valves 28, 30, 44, 33 are closed, so that process gas can flow from the vacuum chamber 14 through the first filter 31 to the first scroll pump 21. Valves 25, 26 are closed, so that no process gas can flow through the second filter 32.

[0041] The first filter 31 has a stainless steel housing in which a separating wall 49 is constructed, and the primary filter chamber 47 is separated from the secondary filter chamber 48 by means of this separating wall. An inlet opening 45 is constructed in the primary filter chamber 47, and this inlet opening communicates with the vacuum housing 14. An outlet opening 46 is constructed in the secondary filter chamber 48, and this outlet opening communicates with the first scroll pump 21. Between the primary filter chamber 47 and the secondary filter chamber 48, the process gas passes through a filter core 52 made of a porous material. The active particles contained in the enriched process gas are deposited on the outer side and in the pores of the filter core 52, so that the process gas entering the inner space of the filter core 52 is freed of active particles. The cleaned process gas leaves the first filter 31 through the secondary filter chamber 48 and is guided to the first scroll pump 21. Since the process gas has been freed of the active components, this process gas can be safely discharged into the surrounding environment at the outlet of the second scroll pump 22. Over time, more and more particles are deposited on the filter core 52, which results in the filter having to be cleaned at regular intervals to remove the particles from the filter.

[0042] The second filter 32 is constructed identically to the first filter 31. After the stage in the active state, the second filter 32 is brought into the passive state in order to perform the cleaning. After closing valves 25, 26, there is no longer any process gas flow between the inlet opening 45 and the outlet opening 46. In a first step, the ventilation valve 24 is opened, so that air from the atmosphere enters the secondary filter chamber 48 through the supply opening 50. As an alternative, a compressed air source or an oxygen reservoir can also be connected to the ventilation valve 24. Due to the pressure difference between the atmospheric pressure and the pressure in the inner space of the second filter 32, a strong flow is generated from the secondary filter chamber 48 into the primary filter chamber 47, and this flow passes through the filter core 52 in a countercurrent manner. The particles adhering to the filter core 52 are loosened and are first distributed in the primary filter chamber 47 with the air flow and then sink to the bottom.

[0043] Upon contact with air-oxygen, the particles react, thereby releasing heat. The cleaning cycle is set such that the heat output is not large enough to damage the second filter 32. A grid plate 55 is arranged parallel to the bottom of the inclined surface 53 of the second filter 32. An air stream is introduced into the second filter 32 through a fluidization opening 54 by means of a fluidization device coupled to a valve 27. The air stream is distributed between the inclined surface 53 and the grid plate 55 and passes through the grid plate from below. The particles accumulated at the bottom of the second filter 32 are put into a fluidized state by the air stream.

[0044] The fluidized particles are withdrawn from the second filter 32 through a cleaning opening 51 by means of a liquid ring pump 35. The stage in which the liquid ring pump 35 is in operation to discharge the particles from the second filter 32 is the first stage of the operating cycle in the sense of the present invention. The previous stage is called the first transition stage, and the stage following the first stage is called the second transition stage.

[0045] Fresh water is continuously supplied as operating liquid to the liquid ring pump 35 during operation. A corresponding amount of the operating liquid is discharged through the outlet of the liquid ring pump 35 and conveyed to a collection container 36. The particles discharged from the second filter 32 are mixed with the operating liquid and enter the collection container 36 together with the operating liquid. The particles that have not completely lost their activity yet can react further by contact with the operating liquid. The gaseous components are discharged upward from the collection container 36. If active gaseous components are included, the discharged gas can be diluted with air and then released into the surrounding environment. The operating liquid enriched with particles is also taken out of the collection container 36 and supplied to a treatment unit.

[0046] After the particles are removed from the second filter 32, the valves 24, 27, 34 are closed again, and in the second transition stage, the second filter 32 is prepared for transition to the active state. For this purpose, the valve 23 is first opened, so that the internal space of the second filter 32 is evacuated by the third vacuum pump 20. Once the pressure in the internal space of the second filter 32 is the same as the pressure in the internal space of the first filter 31, the second filter 32 is prepared for transition to the active state, and the valve 23 is closed again.

[0047] A pressure sensor is used to monitor the pressure difference between the inlet opening 45 and the outlet opening 46 of the first filter 31. The more particles accumulate in the first filter 31, the greater the pressure difference, so that a threshold value of the pressure difference can be determined, at which the first filter 31 needs to be cleaned. If the threshold value is reached, the valves 25, 26 are opened, so that the second filter 32 transitions to the active state. The valves 29, 37 are closed in order to bring the first filter 31 to the passive state.

[0048] The cleaning of the first filter 31 starts as described with the valve 30 being opened, so that air from the surroundings enters the secondary filtration chamber 48. After activating the fluidizing device coupled to the valve 28 and opening the valve 44, the first filter 31 is connected to the liquid ring pump 35 so that particles can be extracted. Subsequently, the valves 28, 30, 44 are closed and the valve 33 is opened in order to evacuate the interior space of the first filter 31, so that the first filter 31 is ready to transition again into the active state. The respective valves are actuated in a buffered manner in order to keep the influence on the pressure of the process gas as low as possible. With the exception of the vent valves 24, 30, these are opened quickly in order to generate as sudden a flow as possible into the interior spaces of the filters 31, 32.

[0049] In an alternative embodiment according to Figure 3 , the vacuum pump used to generate a vacuum in the vacuum housing 14 is a single screw pump 21. The processing device 43 is coupled to the outlet of the screw pump 21, in which the process gas conveyed from the vacuum housing 14 and freed of active particles is processed. The pure argon gas generated by the processing is led back to the vacuum housing 14 and can be reused there as a purge gas. The other components of the process gas are output to the surroundings.

[0050] The cleaning interval is obtained not based on the pressure difference across the filters 31, 32, but based on a time period. If the process gas has passed through the active filters within a pre-given time period, it is considered that a sufficient amount of particles has accumulated and thus cleaning should be carried out.

Claims

1. A method for removing active particles from a vacuum environment (14), wherein, Process gas is conveyed from the vacuum environment (14) using vacuum pumps (21, 22), wherein the process gas is guided between the vacuum environment (14) and the vacuum pumps (21, 22) through a first filter (31) and a second filter (32) in order to filter the active particles from the process gas, and wherein a liquid ring pump (35) is used to discharge particles from the first filter (31) and the second filter (32), wherein, in a first stage of the method, the first filter (31) is active and the second filter (32) is passive, and wherein, in a second stage of the method, the first filter (31) is passive and the second filter (32) is active, and wherein, in the first stage, the process gas is guided through the first filter (31), and the liquid ring pump (35) discharges particles from the second filter (32), and wherein, in the second stage, the process gas is guided through the second filter (32), and the liquid ring pump (35) discharges particles from the first filter (31).

2. The method according to claim 1, wherein, Process gas is continuously conveyed from the vacuum environment (14) between the first stage and the second stage.

3. The method according to claim 1 or 2, wherein The first filter (31) and / or the second filter (32) includes a primary filtration chamber (47) and a secondary filtration chamber (48) separated from each other by a filter material (52), and wherein the process gas is transferred from the primary filtration chamber (47) through the filter material (52) into the secondary filtration chamber (48).

4. The method according to any one of claims 1 to 3, wherein, In a first transition stage, an oxygen-containing gas is introduced into the passive filter (31, 32).

5. The method according to claim 4, wherein, The oxygen-containing gas is introduced into the secondary filtration chamber (48), thereby creating a countercurrent flow through the filter material (25).

6. The method according to claim 4 or 5, wherein, The liquid ring pump (35) is connected to the primary filtration chamber (47) of the first filter (32) and / or the second filter (32).

7. The method according to any one of claims 1 to 6, wherein, Particles discharged from the passive filter (31, 32) are discharged from the liquid ring pump together with the operating liquid of the liquid ring pump (35).

8. The method according to any one of claims 1 to 7, wherein The process gas leaving the vacuum pumps (21, 22) is treated for reuse in the vacuum environment (14).

9. The method according to claim 8, wherein Argon is regenerated from the process gas.

10. An apparatus for removing active particles from a vacuum environment, the apparatus having: A vacuum housing (14); and A vacuum pump (21, 22) coupled to the vacuum housing (14), wherein, A first filter (31) and a second filter (32) are arranged between the vacuum housing (14) and the vacuum pumps (21, 22) in order to filter active particles from the process gas conveyed by the vacuum pumps (21, 22); A liquid ring pump (35) for extracting particles from the first filter (31) and the second filter (32); and A switching device (57) for bringing the device into a first switching state and a second switching state, such that in the first switching state, the process gas is guided through the first filter (31), and the liquid ring pump (35) discharges particles from the second filter (32), and in the second switching state, the process gas is guided through the second filter (32), and the liquid ring pump (35) extracts particles from the first filter (31).

11. A process system, comprising the apparatus according to claim 10, wherein, A single crystal silicon ingot is manufactured in the vacuum housing (14), and wherein the process gas output by the vacuum pumps (21, 22) is treated and returned to the vacuum housing (14).

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