JP4211320B2 - Vacuum pump - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum pump such as a turbo molecular pump used as a vacuum exhaust pump of a semiconductor manufacturing apparatus or the like.
[0002]
[Prior art]
Semiconductor manufacturing is performed through various processes such as optical processing and chemical processing. As a typical process example of the optical process, for example, an exposure process for printing a circuit pattern on the wafer surface can be mentioned. As a typical process example of the chemical process, for example, a surface process for forming a thin film on the wafer surface, An etching process, a cleaning process, etc. are mentioned.
In the surface treatment, there is a CVD (Chemical Vapor Deposition) technique as a manufacturing technique indispensable in semiconductor manufacturing. This CVD is a technique in which a raw material gas is supplied onto a substrate such as a wafer, and a thin film is formed on the substrate through gas adsorption and chemical reaction on the substrate. This technology is indispensable for realizing high integration of semiconductors.
[0003]
Among the above-mentioned CVDs, vacuum CVD and plasma CVD are performed in a vacuum atmosphere, so a vacuum exhaust device is required. In this vacuum evacuation device, a configuration in which a plurality of pumps are appropriately combined, such as a rotary pump, a diffusion pump, and a turbo molecular pump, that enable multistage exhaust from atmospheric pressure is generally employed.
[0004]
Here, an example of a turbo molecular pump, which is a type of vacuum pump, will be briefly described with reference to the perspective view of FIG.
As shown in the figure, the turbo molecular pump P has a configuration in which various components are housed in a casing 1 including divided casings 1a and 1b. An intake port 1c is formed in one divided casing 1a, and an exhaust port 1d is formed in the other divided casing 1b.
[0005]
In the rotor chamber 2 inside the casing 1, a rotating body 4 is arranged as a rotor constituting a pump mechanism. The rotating body 4 includes a rotor shaft 4a and moving blades 5 arranged and fixed radially around one end of the rotor shaft 4a.
Further, stationary vanes 3 constituting a pump mechanism together with the above-described rotating body 4 are fixed to the divided casing 1b side. The rotating body 4 described above is a member that rotates at a high speed of, for example, 90,000 rpm (1,500 revolutions / second). Therefore, generally, a lightweight and high stress strength aluminum alloy or the like is preferably used as the material. It is done.
[0006]
A thrust magnetic disk 6 is fixed to the other end of the rotor shaft 4a opposite to the one end. Corresponding to the thrust magnetic disk 6, a thrust magnetic bearing 8 is disposed so that the front and back surfaces are sandwiched between them. The thrust magnetic bearing 8 is a magnetic bearing that holds the axial position of the rotating body 4 by holding the thrust magnetic disk 6 when receiving power supply.
[0007]
The rotor shaft 4a is held inside a pair of radial magnetic bearings 7a and 7b fixed inside the split casing 1b. These radial magnetic bearings 7a and 7b are magnetic bearings that hold the rotor shaft 4a at the axial center position when supplied with electric power.
Further, ball bearings 9 and 10 are provided as protective bearings at both ends of the rotor shaft 4a. Further, the rotor shaft 4a is inserted into a rotor driving motor 11 (motor) positioned between the ball bearings 9 and 10 and fixed in the divided casing 1b. It is designed to rotate around.
[0008]
In such a vacuum pump, when the surface temperature of the gas passage formed inside the vacuum pump is lower than the sublimation temperature of the sucked gas, the gas may solidify and adhere to the gas passage wall surface or the like. And if this solidified material adheres to and accumulates in a narrow gap formed between the rotor blade on the rotating body side and the stationary blade on the stationary body side, it will of course cause a decrease in pump performance. Contacting the solidified material may cause damage to the structural members, and in the worst case, the moving blades and stationary blades may be damaged.
For this reason, in the conventional vacuum pump, for example, as disclosed in JP-A-10-205486, the outer periphery of the casing is directly heated by a heater to prevent solidification, or JP-A-9-72293. As disclosed in the publication, solidification is prevented by partially heating the downstream side of a gas flow path having a high sublimation temperature (high pressure).
[0009]
FIG. 6 is an enlarged view of a main part of a conventional vacuum pump P ′ provided with a heat radiating plate as a heating means.
In this vacuum pump P ′, in order to prevent the solidification by maintaining the passing gas at a temperature higher than the sublimation temperature, a heat radiating plate 12 is installed between the casing 1 and the rotating body 4 to which the rotor blades 5 are attached. It is configured. The vacuum pump P ′ in this case is a two-stage compression type composed of an axial flow stage and a screw groove stage, and a heat radiating plate 12 is disposed around a screw groove portion 13 that performs compression on the downstream side. In addition, the code | symbol 14 in a figure is a cooling water flow path for cooling the moving blade 5 by heat conduction, and the temperature rise of the moving blade 5 is prevented by circulating cooling water.
[0010]
In such a configuration, a part of the gas to be compressed may flow into the space part volume S of the gap formed between the split casing 1b and the heat sink 12 and solidify. When the amount of solidified deposit increases, the moving blade 5 rotating at a high speed in the upper part comes into contact and causes trouble. Therefore, the space part volume S may be quite small, and maintenance such as frequent disassembly and cleaning is necessary to prevent troubles.
[0011]
[Problems to be solved by the invention]
However, since the above-described measures for preventing solidification by heating are limited to a temperature lower than the allowable temperature of components constituting the vacuum pump, there is a limit to application to a vacuum pump used in a process that handles a gas having a high sublimation temperature. . For this reason, especially when handling a gas with a high sublimation temperature, it is necessary to stop the operation and perform maintenance of decomposition cleaning frequently (for example, every month) to prevent troubles due to accumulation of solidified substances. Improvement is desired because it causes a decrease in productivity.
[0012]
In addition, since a moving blade rotating at a high speed is required to be light and strong, an aluminum alloy is usually employed. However, aluminum alloys are vulnerable to temperature rise, and strength and creep life are problematic at high temperatures. For this reason, cooling including protection of electronic components is required, and a desired temperature (for example, about 40 ° C. to 50 ° C.) can be maintained by providing a cooling water flow path in the casing and circulating the cooling water. Has been done.
Therefore, when such cooling is performed, the above-mentioned gas solidified product is likely to be deposited particularly in the case of a gas having a high sublimation temperature. Therefore, the aluminum blade moving blade protection by cooling and the solidified product deposition by heating are performed. It is necessary to solve the conflicting issue of prevention.
[0013]
Although it is conceivable to provide a trap on the upstream side of the vacuum pump to remove the solidified material, such measures are generally not preferred by users for the following reasons.
(1) If a solidified material is deposited on the upstream side of the vacuum pump, the deposited material becomes a dust (particle) generation source, which may adversely affect the process side.
(2) The accumulated solid matter acts as a flow resistance and lowers the exhaust efficiency.
[0014]
The present invention has been made in view of the above circumstances, and is not affected by cooling for the purpose of protecting a moving blade made of an aluminum alloy or the like, and in particular, solidified deposits in a portion that causes damage or breakage of the pump mechanism. The purpose is to solve the problem of preventing the problem.
[0015]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
The vacuum pump according to claim 1 is provided with a pump mechanism including a rotating body provided with moving blades and a stationary body provided with stationary blades in a casing having a gas inlet and an outlet. A vacuum pump configured to discharge the gas sucked from the intake port from the exhaust port, communicated with a gas flow path in the casing from the intake port to the exhaust port, and in the casing or A trap portion that is a space that protrudes to the outside of the casing and is cooled by a cooling means so as to have a temperature lower than the sublimation temperature of the gas is provided.
[0016]
According to such a vacuum pump, a trap portion that is communicated with the gas flow path in the casing from the intake port to the exhaust port and has a temperature lower than the sublimation temperature of the gas is provided. It can be solidified and trapped.
In this case, it is preferable to set the space volume of the trap portion as large as possible. As a result, the amount of solidified deposit increases, so that the maintenance interval can be extended.
[0017]
2. The vacuum pump according to claim 1, wherein the rotating body includes an axial flow stage and a thread groove stage, and the trap portion is provided in communication with a gas flow path between the axial flow stage and the thread groove stage. It is preferable that the trapped portion can be provided in front of the region that is most easily solidified to trap the solidified material.
[0018]
3. The vacuum pump according to claim 1, wherein the trap portion is preferably provided at a position off the main flow path of the gas flow path, whereby the trap is disposed at a position substantially away from the compression mechanism. Therefore, even if the solidified material accumulates, the pump mechanism such as the moving blade is less likely to be damaged.
[0019]
In the vacuum pump according to a fourth aspect of the present invention, it is preferable that the trap portion is provided with an opening / closing means for removing the solidified material, and thereby maintenance for removing the accumulated solidified material is facilitated.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a vacuum pump according to the present invention will be described with reference to the drawings. A vacuum pump is a device that compresses low-pressure gas below atmospheric pressure and releases it to the atmosphere.
1 (a) and 1 (b) are schematic views showing a configuration example of a vacuum pump according to the present invention, and the technical idea of the present invention will be described below based on the drawings. This vacuum pump 20 is of a type called a turbo molecular pump, and is equipped as a part of an exhaust system together with a rotary pump, a diffusion pump, etc., for example, in a CVD apparatus (not shown) used for semiconductor manufacturing, It is a device used for exhaust. In such exhaust, for example, the gas after etching contains a solidified gas component such as AlCl ₃ .
Hereinafter, the handling fluid of the vacuum pump including the gas component of the solidified product is referred to as gas.
[0021]
The vacuum pump 20 described above has a configuration in which a pump mechanism 30 including a rotating body 31 and a stationary body 24 is disposed in a casing 21 having a gas inlet 22 and an exhaust 23.
In the configuration example shown in FIG. 1A, the rotating body 31 generally called a rotor includes a rotating shaft (not shown), one or a plurality of moving blades 32 fixed to the rotating shaft, And a thread groove 33 provided on the downstream side of the rotor blade 32. The rotating body 31 is supported by a thrust magnetic bearing and a radial magnetic bearing (not shown) so that an appropriate portion of the rotating shaft can rotate, and is rotated at a high speed by a rotor driving motor (not shown). That is, the illustrated vacuum pump 20 has a two-stage compression configuration in which the rotating body 31 includes an axial flow stage that performs compression by the moving blade 32 and a stationary blade that will be described later, and a thread groove stage that performs compression by the thread groove portion 33. It has become.
In the illustrated example, the three moving blades 32 are provided, but the present invention is not limited to this.
[0022]
One stationary body 24 includes a stationary blade 25 fixed to one or more stages on the inner peripheral side of the casing 21, a stator 26 fixed to the casing 21 so as to support the rotating shaft of the rotating body 31, and the stator. 26 and various bearings (not shown) installed in the interior. Each stationary blade 25 is alternately arranged with the moving blade 32 provided on the rotating body 31 side in the axial direction of the rotating shaft.
[0023]
In this vacuum pump 20, the rotating body 31 rotates at a high speed, so that the gas sucked from the intake port 22 passes between the moving blade 32 and the stationary blade 25 in the axial flow stage and is compressed. After passing through and being compressed, it flows out from the exhaust port 23. As a result, the intake port 22 becomes a high vacuum and the exhaust port 23 becomes a low vacuum.
[0024]
In the present invention, a trap portion 27 that communicates with a gas flow path (indicated by an arrow G in the figure) in the casing 21 from the intake port 22 to the exhaust port 23 is provided for the vacuum pump 20 having the above-described configuration. . The trap portion 27 is a space portion set to be lower than the sublimation temperature of the gas to be sucked. For example, a space portion that protrudes to the outer peripheral side of the casing 21 is formed, and a wall surface or the like is formed by cooling with the outside air temperature. Some maintain the internal temperature below the sublimation temperature. Alternatively, a cooling water flow path may be provided around the trap portion 27 to allow water to flow and actively cool by heat conduction.
Moreover, the trap part 27 shown to Fig.1 (a) is provided in communication with the gas flow path between the axial flow stage in the rotary body 31, and a thread groove step.
[0025]
With the vacuum pump 20 having such a configuration, a part of the gas sucked from the intake port 22 flows into the trap part 27 and is cooled below the sublimation temperature in the trap part 27. Accordingly, since the gas is solidified and accumulated in the trap portion 27, the trap portion 27 becomes a space portion having a function of positively solidifying and trapping the gas.
[0026]
Further, in the case where the rotating body 31 includes an axial flow stage and a thread groove stage, such a trap portion 27 has a gas flow path between the axial flow stage and the thread groove stage, that is, the moving blade 32 in the axial direction. It is preferable to provide a gas flow path located between the screw groove portion 33 and the screw groove portion 33. This is because the trap portion 27 can be provided in front (upstream side) of the region that is most easily solidified.
That is, since the sublimation temperature of the gas also increases on the downstream side of the gas passage having a high pressure, in the pump mechanism 30 of the vacuum pump 20, the gas substantially increases in pressure and the sublimation temperature also increases. The solidified material is positively trapped from the upstream side of the thread groove step, which is an easily depositing region, and troubles due to the accumulation of the solidified material on the downstream side of the trap portion 27 are prevented or suppressed in advance.
Further, since the temperature in the vicinity of the downstream stage of the moving blade 32 close to the thread groove stage tends to be lowered due to the influence of the cooling of the moving blade by cooling water or the like, gas is actively supplied from the trap portion 27 close to this region. By solidifying and depositing the solidified product, damage and breakage of the rotor blade 32 and the like can be prevented or suppressed.
[0027]
By the way, it is preferable that the trap part 27 mentioned above takes the space volume as large as possible. This is because by securing a large space volume, the solidified material deposition allowance increases and the maintenance interval can be lengthened. That is, since the continuous operation time of the vacuum pump 20 is extended, the operation stop interval of a process using the vacuum pump 20 can be extended to reduce the number of operation stops.
[0028]
FIG. 1B shows a single-stage compression type vacuum pump 20 ′, in which the rotating body 31 ′ of the pump mechanism 30 ′ is not provided with a thread groove step and is compressed only by an axial flow step. Has been.
In the vacuum pump 20 ′ thus configured, the gas flow path indicated by the arrow G communicates between the stationary blades 32 arranged in a plurality of stages in the axial direction, preferably between the stationary blades 32 that are downstream. In this way, a space serving as the trap portion 27 is provided outside the casing 21.
[0029]
Even in such a configuration, the trap portion 27 provided to communicate with the gas flow path in the region where the gas is compressed and on the high pressure side has a high sublimation temperature so as to positively solidify the gas and deposit the solidified product. Therefore, the occurrence of troubles due to the accumulation of solidified substances can be prevented or suppressed in advance. Further, since the temperature in the vicinity of the downstream stage of the moving blade 32 tends to be lowered due to the cooling effect of the moving blade by cooling water or the like, the gas is positively solidified by the trap portion 27 near this region. Can be prevented from being damaged or broken.
Even in this case, it is preferable to set the space volume of the trap portion 27 as large as possible in consideration of the maintenance interval.
[0030]
FIG. 2 is a cross-sectional view showing a specific configuration example of the vacuum pump according to the present invention, and a new reference numeral 20A is given to the vacuum pump.
Reference numeral 21 in the figure denotes a casing, which has a configuration in which upper and lower divided casings 21a and 21b are integrated. The casing 21 is provided with an intake port 22 and an exhaust port 23, and a stationary blade 25 is fixedly provided inside the divided casing 21 a side where the intake port 22 is provided. The position of the stationary blade 25 is fixed by a spacer 28.
[0031]
A rotating body 31 is installed in the casing 21 so as to be capable of high-speed rotation with respect to the stationary side including the casing 21 and the stationary blade 25 described above. The rotating body 31 includes a plurality of rotor blades 32 and a thread groove portion 33 provided in a rotor portion 35 integrally connected to a rotating shaft 34. Accordingly, the rotor 31 includes two axial flow stages and a thread groove stage. It has a stage compression structure. The moving blades 32 on the rotating body 31 side are alternately arranged in the axial direction of the stationary blade 25 and the rotating shaft 34 described above.
The rotating shaft 34 of the rotating body 31 includes a magnetic bearing 29a as an upper bearing, a magnetic bearing 29b as a lower bearing, and an axial bearing as an upper bearing attached to the inner peripheral surface of the stator 26 fixed to the split casing 21b. It is supported by the magnetic bearing 29c and can rotate at high speed. In addition, the code | symbol M in a figure is the motor for a rotor drive provided between the internal peripheral surface of the stator 26 and the rotating shaft 34. FIG.
[0032]
The vacuum pump 20A is provided with a heat radiating plate 41 connected to the heating unit 40 as a heating means in order to prevent the compressed gas from becoming below the sublimation temperature. The heat radiating plate 41 is a substantially cylindrical member that is disposed between the screw groove portion 33 of the rotating body 31 and the casing 21 and includes a bottom surface portion 42. The heat radiating plate 41 is heated by heat transfer, with the bottom surface portion 42 connected to the heating unit 40. In addition, the clearance gap between the heat sink 41 and the thread groove part 33 is maintained to the minimum necessary in order to obtain compression efficiency.
[0033]
On the other hand, between the outer peripheral surface of the heat radiating plate 41 and the inner peripheral surface of the divided casing 21b, a space portion that communicates with the gas flow path and becomes the trap portion 27A is formed over the entire circumference. For example, as shown in FIG. 3 in which the main portion is enlarged, the trap portion 27A has a large volume by securing a large dimension in the axial direction of the rotary shaft 34 while increasing the outer diameter of the casing 21. Has been. That is, the diameter of the casing 21 is increased without changing the pump mechanism 30, and in particular, the diameter of the casing 21 serving as the outer peripheral portion of the thread groove portion 33 and the heat radiating plate 41 is increased to ensure the radial dimension W of the trap portion 27A. In addition, by lowering the locking position between the heat radiating plate 41 and the divided casing 21b to ensure the axial dimension H, the trap portion 27A having a large space volume is formed as a result.
In addition, the code | symbol 45 in a figure is the cooling water flow path which passes through the appropriate place in the division | segmentation casing 21b, and cools the moving blade 32 and the trap part 27A to below the sublimation temperature of gas.
[0034]
With such a configuration, the gas sucked from the intake port 22 passes between the stationary blade 25 and the moving blade 32 and is compressed by the axial flow stage, and then between the screw groove portion 33 and the heat radiating plate 41. It flows through the main flow (indicated by arrow G in FIG. 3) of the gas flow path that passes through and is compressed by the thread groove step, and flows out from the exhaust port 23.
At this time, the gas passing through the thread groove step is maintained at a temperature higher than the sublimation temperature by heating the heat radiating plate 41, and therefore flows out from the exhaust port 23 without solidifying. However, a part of the gas (indicated by the arrow g in FIG. 3) guided from the axial flow stage to the thread groove stage flows into the trap part 27A communicating with the gas flow path and is cooled. Then, the gas cooled below the sublimation temperature is solidified. Accordingly, the trap portion 27A has a function of positively generating and depositing the solidified substance of the sucked gas. Note that reference numeral 46 shown in FIG. 3 denotes a seal portion, which is appropriately selected from, for example, an O-ring or a metal touch, and closes the bottom surface portion side of the trap portion 27A.
[0035]
The trap portion 27A having the configuration shown in FIGS. 2 and 3 is separated from the main flow path of the gas passing through the axial flow stage and the thread groove stage, in other words, from a pump mechanism that performs compression via the heat radiating plate 41. Since it is provided at a distant position, it is difficult to be damaged by contact because it is separated from a moving blade rotating at high speed even if solidified material is accumulated. In particular, since the space portion volume S of the conventional structure shown in FIG. 6 is greatly expanded, the allowable amount for depositing the solidified material can be increased and a long-term maintenance interval can be secured.
[0036]
Next, a modified example of the trap part 27A described above will be described with reference to FIG. In this modification, an opening / closing lid 47 is provided at the opening portion as an opening / closing means for removing the solidified substance in the trap portion 27A.
The opening / closing lid 47 is usually attached so that the trap portion 27A is hermetically sealed with an O-ring 48 or the like as a sealing means, and can be opened / closed or detached when necessary to form an opening. Therefore, if the opening / closing lid 47 is opened to form an opening, the solidified material accumulated in the trap portion 27A can be easily scraped and removed, so that the solidified material can be removed with a short shutdown. The maintenance frequency for disassembling the vacuum pump can be greatly reduced.
[0037]
Now, the vacuum pump provided with the trap portions 27 and 27A having the above-described configuration is, for example, a gas after etching in which aluminum is mixed in a gas phase and an AlCl ₃ solidified product is generated. This is particularly effective for the treatment of gas containing gas components such as InCl ₃ which is a highly solidified product. That is, even when the upper limit of the heating temperature is limited in order to cool and protect the rotating body made of an aluminum alloy such as the rotor blade 32, in other words, it is not possible to heat to a temperature higher than the sublimation temperature. However, since the trap portions 27 and 27A are positively solidified and trapped, it is possible to treat even a gas containing a solidified gas component having a high sublimation temperature.
[0038]
In addition, since the trap portions 27 and 27A are both provided in the casing 21 of the vacuum pump, the solidified material does not flow backward to the upstream side (for example, the process chamber side) of the vacuum pump. Contamination of the upstream process due to the solidified product can be prevented.
[0039]
In addition, the structure of this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.
[0040]
【The invention's effect】
The vacuum pump of the present invention has the following effects.
According to the first aspect of the present invention, since the trap portion that communicates with the gas flow path in the casing from the intake port to the exhaust port and has a temperature lower than the sublimation temperature of the gas is provided, Can be solidified and trapped. As a result, since the solidified material is less likely to adhere to the pump mechanism periphery and components on the downstream side of the trap, it is possible to extend the maintenance interval such as disassembly and cleaning performed so that troubles due to the solidified material do not occur, The economic effect of improving productivity is extremely high.
Therefore, the solidified material is positively deposited in the trap part without being affected by cooling for the purpose of protecting the rotor blade made of aluminum alloy or the like, and the solidified material is prevented from being deposited in a part that causes damage or breakage of the pump mechanism. As a result, it can be applied to a gas containing a gas component of a solidified product having a high sublimation temperature.
In this case, since the amount of solidified deposit increases by setting the space volume of the trap portion large, the optimum value may be determined in consideration of the miniaturization of the vacuum pump and the maintenance interval.
[0041]
Further, in a two-stage compression type vacuum pump in which the rotating body includes an axial flow stage and a thread groove stage, a trap portion is provided in communication with a gas flow path between the axial flow stage and the thread groove stage. Thus, the trapped portion can be provided in front of the region that is most likely to be solidified to trap the solidified material efficiently.
In addition, by providing the trap part at a position away from the main flow path of the gas flow path, the trap part is provided at a position substantially away from the compression mechanism. Damage to pump mechanisms such as blades is difficult.
Moreover, by providing an opening / closing means for removing the solidified substance in the trap part, it is possible to remove the accumulated solidified substance without carrying out decomposition cleaning or reducing the number of executions. The economic effect due to the ease of maintenance work is extremely high.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration example of a vacuum pump as one embodiment of the present invention, in which (a) is a two-stage compression type and (b) is a one-stage compression type.
FIG. 2 is a cross-sectional view showing a specific configuration example of a two-stage compression type vacuum pump according to the present invention.
3 is an enlarged cross-sectional view of the main part of FIG. 2;
4 is an enlarged cross-sectional view of a main part showing a modified example of FIG. 3;
FIG. 5 is a partial sectional perspective view showing a configuration example of a conventional vacuum pump.
FIG. 6 is a cross-sectional view of a main part of a vacuum pump showing a conventional example.
[Explanation of symbols]
20, 20 ', 20A Vacuum pump 21 Casing 22 Intake port 23 Exhaust port 24 Stationary body 25 Stationary blades 27, 27A Trap unit 30, 30' Pump mechanism 31, 31 'Rotating body 32 Rotor blade 33 Screw groove portion 41 Heat sink 45 Cooling Water channel 47 Opening / closing lid (opening / closing means for removing solidified material)

Claims (4)

A pump mechanism comprising a rotating body having a moving blade and a stationary body having a stationary blade is disposed in a casing having a gas inlet and an exhaust port, and the gas sucked from the inlet is A vacuum pump configured to exhaust from an exhaust port,
It communicates with the gas flow path in the casing from the intake port to the exhaust port, protrudes into the casing or the outside of the casing, and is cooled by the cooling means so that the temperature becomes lower than the sublimation temperature of the gas. A vacuum pump characterized in that a trap part is provided.   The rotary body includes an axial flow step and a thread groove step, and the trap portion is provided in communication with a gas flow path between the axial flow step and the screw groove step. Vacuum pump.   The vacuum pump according to claim 1 or 2, wherein the trap portion is provided at a position outside the main flow path of the gas flow path.   The vacuum pump according to any one of claims 1 to 3, wherein the trap section includes an opening / closing means for removing a solidified substance.

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