JP2001032789A - Molecular pump - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the exhaust performance with respect to water and to greatly improve the exhaust efficiency with respect to gases having a small molecular weight such as hydrogen and helium, on the other hand, other gases other than water To provide a molecular pump which does not cause a problem of a decrease in exhaust performance due to the effect of conductance on the molecular pump. SOLUTION: The rotor includes a rotor having rotor blades rotatably disposed in a pump container having an inlet and an outlet, and a stator having fixed blades disposed between the rotor blades, and rotates the rotor. Thus, the problem has been solved by a molecular pump in which a very low-temperature cooling surface is formed in a part of a stator in a molecular pump for exhausting gas molecules.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molecular pump for exhausting gas molecules by rotating a rotor at an ultra-high speed. The present invention relates to a molecular pump having improved exhaust performance for a gas having a low molecular weight.

[0002]

2. Description of the Related Art As a means for complementarily improving the exhaust performance of a molecular pump, a method has been proposed in which a cooling trap is combined with the inlet side of the molecular pump.

For example, as shown in FIG. 5, a turbo blade 11 as a moving blade rotatably arranged in a pump container 1 having an intake port 2 and an exhaust port 3 and a thread groove portion 14 on the exhaust port 3 side. , A stator blade 19 as a fixed blade disposed between the turbo blades 11 and a stator ring 2
0, a combined molecular pump composed of a stator 15 and a separate nipple-shaped trap container 5 on the suction port 2 side thereof, connected to a refrigerator 24 in the trap container 5 and cooled to a very low temperature. A cooling panel (cooling trap surface) 25 for freezing and collecting water molecules has been proposed (JP-A-6-58291). In this conventional example, the cooling panel (cooling trap surface) 25 can greatly improve the exhaust performance with respect to water.
For other gases, there is a problem that the exhaust performance deteriorates due to the conductance effect. Further, there is also a problem that there is almost no effect of improving the exhaust performance with respect to a gas having a small molecular weight such as hydrogen or helium.

FIG. 6 shows an arrangement in which a cooling panel 25 is arranged inside a container (pump container) 1 of a molecular pump (Japanese Patent Laid-Open No. 6-330886). The effect of improving the exhaust performance and the like are basically the same as the configuration shown in FIG. 5 (Japanese Patent Laid-Open No. 6-58291).

[0005] The structure of the cooling surface of the cooling panel 25 uses a refrigerant such as liquid nitrogen, and recently uses a one-stage helium refrigerator.

[0006] The function of the cooling panel (cooling trap surface) in the above-described configuration of the conventional example is an exhaust performance for water contained in the atmosphere and discharged in large quantities from the surface of a constituent material such as the wall surface of a vacuum vessel or from inside the material. The substantial complementation improves the exhaust performance of the vacuum exhaust pump system as a whole.

[0007]

However, in the combination of the conventional molecular pump and the cooling panel (cooling trap surface) as shown in the above example, the molecular pumping performance is greatly improved, although the water pumping performance is greatly improved. A cooling panel (cooling trap surface) is placed between the air intake port of the vacuum processing device and the vacuum processing device, so that the conductance of the gas by the cooling panel (cooling trap surface) decreases. The problem is that the exhaust performance is reduced.

Further, in a vacuum processing apparatus to be used for the production of semiconductors and electronic parts in the future, the ultimate pressure of the apparatus should be reduced in order to eliminate as much as possible residual gas in the apparatus from adversely affecting various uses as impurities. In view of the necessity of further lowering, it is important to improve the exhaust performance of gas having a small molecular weight such as hydrogen or helium. In combination with the trap surface, there is also a problem to be solved in that it has little effect on improving the exhaust performance with respect to gas having a small molecular weight such as hydrogen or helium.

[0009] For the molecular pump, while improving the pumping speed with respect to water, the pumping performance with respect to gas having a small molecular weight such as hydrogen and helium is improved.
A major challenge in the future is to prevent the exhaust performance of gases other than gases having a low molecular weight, such as hydrogen and helium, from lowering.

An object of the present invention is to solve the above-mentioned problems and problems, and to improve the exhaust performance for gases having a small molecular weight such as hydrogen and helium, and to reduce the exhaust performance for gases other than these. The object of the present invention is to provide a molecular pump which does not have any problem.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a rotor having rotor blades rotatably disposed in a pump container having an inlet and an outlet, and a fixed blade disposed between the rotor blades. In a molecular pump comprising a stator and exhausting gas molecules by rotating a rotor, the above problem is solved by forming a cryogenic cooling surface in a part of the stator.

That is, in the molecular pump according to the present invention, gas molecules entering from the suction port connected to the vacuum processing apparatus 4 can be used at a temperature of about 60 K to 123 K suitable for freezing and collecting water molecules.
By colliding with the stator surface cooled by K, thermal kinetic energy is lost, and a structure is adopted in which the thermal kinetic velocity of gas molecules is greatly reduced. Thus, according to the molecular pump of the present invention, the exhaust efficiency of the molecular pump for gas having a small molecular weight such as hydrogen or helium can be greatly improved.

For example, a gas at room temperature of about 300K is 100K
When it hits the cooling panel of about 1/3 of the temperature,
The thermal motion velocity of the gas molecules is reduced to one third, and the exhaust efficiency of light gas molecules can be improved by the amount corresponding to the decrease in the velocity. Actually, the ratio of the rotational speed of the rotor turbo wing to the thermal motion velocity of the gas molecules affects the exhaust performance of the molecular pump, so the exhaust performance does not necessarily improve as the temperature of the gas molecules decreases. However, the ability to lower the temperature of gas molecules entering from the inlet is the first measure for improving exhaust performance.

[0014] Even when a cooling panel (cooling trap surface) is formed on the pump suction port side as in the configuration of a conventional molecular pump, gas molecules undergo thermal motion at the time of collision with the cooling panel (cooling trap surface). Although the speed is reduced, in the configuration of the conventional molecular pump, gas molecules that do not collide with the cooling panel (cooling trap surface), or after collision with the cooling panel (cooling trap surface), are further cooled to room temperature of the container of the molecular pump. Since there are many gas molecules that collide with the surface and receive energy again, as a whole, there was almost no improvement in the exhaust performance of the molecular pump for gases with small molecular weights such as hydrogen and helium. . Further, in the configuration of the conventional molecular pump, there is a problem that the effect of the decrease in conductance on other gases is large, and conversely, the exhaust performance on other gases is reduced.

However, according to the molecular pump of the present invention in which a cryogenic cooling surface is formed in a part of the stator, the molecular pump directly acts on gas molecules entering from the suction port connected to the vacuum processing apparatus 4 side. As a result, the temperature of the gas molecules can be reduced, and the thermal motion velocity can be reduced. Thus, as in the configuration of the conventional molecular pump, the rate at which gas molecules whose thermal motion velocity has been reduced once again receives energy is extremely high. Few. Also, there is no conductance effect on gases other than water.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings. The molecular pump of the present invention has a rotor blade rotatably arranged in a pump container 1 having an inlet 2 and an outlet 3. In a molecular pump including a rotor 14 and a stator having fixed vanes disposed between the rotor blades, and rotating the rotor 14, gas molecules are exhausted. Are formed.

In the above description, the molecular pump has a structure of a compound molecular pump or a screw groove in which the intake port 2 side is a turbo blade 11 as a moving blade, and the exhaust port 3 side is a thread groove portion of a rotor 14. Either a drag-type molecular pump configured with a shape or a turbo-type molecular pump configured with only turbo blades can be used. Either structure can improve the exhaust performance with respect to water, and directly acts on gas molecules entering from the suction port connected to the vacuum processing device 4 to lower the temperature,
Reducing the rate of thermal motion can significantly improve the pumping efficiency of molecular pumps for gases of low molecular weight, such as hydrogen and helium, while reducing the pumping performance due to the effects of conductance on gases other than water. The problem does not arise.

In the molecular pump, which part of the stator and in which range of the stator the cryogenic cooling surface is formed, that is, the number of stages of the stator to be cooled is required for the molecular pump. It can be arbitrarily determined in consideration of the balance between the exhaust performance and the refrigerating capacity of the refrigerator used. However, in order to directly act on the gas molecules entering from the suction port connected to the vacuum processing apparatus 4 side to lower the temperature and reduce the thermal motion speed, the gas molecules are moved to a region near the suction port 2 side of the molecular pump. It is desirable to form a cryogenic cooling surface of the stator.

For example, in the above-described molecular pump, the cryogenic cooling surface of the stator may be formed so as to extend in the direction closer to the molecular pump inlet than the position of the rotor closer to the molecular pump inlet. According to this structure, in addition to the effect of improving the exhaust performance for the gas having a small molecular weight such as hydrogen and helium, the exhaust performance for water on the inlet side of the molecular pump can be further greatly improved.

In the above molecular pump, the cryogenic cooling surface can be formed by using a one-stage helium refrigerator.

Here, as a one-stage helium refrigerator,
If a pulse tube refrigerator is used, the shape can be made compact, which makes it very easy to mount it from the side of the molecular pump.Furthermore, since the refrigerator has no moving parts, it requires almost no maintenance. In addition, the merit in industrial implementation is increased.

In the molecular pump described above, a portion between the portion where the cryogenic cooling surface of the stator is formed in the molecular pump container and a portion where the cryogenic cooling surface of the stator is not formed in the molecular pump container. A heat-insulating seal ring can be interposed in the housing. In this way, by appropriately changing the position where the heat-insulating seal ring is inserted, an appropriate range can be considered in consideration of the balance between the exhaust performance required for the molecular pump and the refrigerating capacity of the refrigerator used. Thus, a cryogenic cooling surface of the stator can be formed. Further, with this configuration, the inside of the molecular pump container in which the extremely low-temperature cooling surface of the stator is formed can be vacuum-connected only to the intake port side, so that the molecular weight of hydrogen, helium, or the like is small. Gases can be prevented from back-diffusing to the inlet side of the molecular pump, and the exhaust performance for these gases can be further improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. 1 to 4 illustrating the embodiment of the present invention, the same components as those shown in FIGS. 5 and 6 showing the configuration of a conventional molecular pump are shown in FIGS. Have the same reference numerals.

The molecular pump according to the present invention shown in FIG. 1 is provided between a rotor 14 having rotating blades rotatably arranged in a pump container 1 having an inlet 2 and an outlet 3 and a rotating blade. In a molecular pump of a type that exhausts gas molecules by rotating a rotor 14 via a shaft 12 of a rotary drive motor, the structure of the rotor is 1 shows an example of a compound molecular pump having a turbo blade 11 as a component and a threaded groove-shaped component portion 14a of a rotor 14 on the exhaust port 3 side.

In the molecular pump of the present invention, a cryogenic cooling surface is formed in a part of the stator. In the embodiment shown in FIG. A cooling surface is formed.

That is, the stator of the portion of the turbo blade 11 has a structure in which the cooling stator blade 13 as a fixed blade is supported by the cooling stator rings 16 and 17a, and has the same structure as that of a normal turbo type molecular pump. The whole is cooled to a very low temperature (about 60K to 123K) by the refrigerator 24.

On the other hand, since the stator 15 and the pump container 1 in the portion of the thread groove-shaped component 14a of the rotor 14 are at room temperature, the cooling stator rings 16, 17a are formed by the heat insulating seal ring 21 and the upper and lower heat insulating materials 22, By using 23a, it is assembled in a structure that can maintain a heat insulating state.

The heat-insulating seal ring 21 has a shape sealed in a vacuum, so that the space between the pump stator 1 and the cooling stator blades 13 and the cooling stator rings 16 and 17 a forming a cryogenic cooling surface of the stator is provided. This space and the inside of the refrigerator 24 are connected only to the intake port 2 side of the molecular pump, and are evacuated to a vacuum.

The heat-insulating seal ring 21 is formed for heat insulation of the cooling stator ring 16, and is provided for the pump container 1.
And a gas having a small molecular weight, such as hydrogen or helium, is prevented from back-diffusing into the intake port 2 side of the molecular pump through the gap between the two. If such a heat-insulating seal ring 21 is employed, it is possible to further improve the exhaust performance of the molecular pump of the present invention for a gas having a small molecular weight such as hydrogen or helium.

As shown in FIG. 4, which shows an enlarged cross-sectional shape of the heat-insulating seal ring 21, for example, a stainless steel seal bellows 27 having a small thermal conductivity is formed in an appropriate size, and the stainless Heat-insulating ring 26
By welding or brazing to a and 26b, a structure sealed in a vacuum can be easily formed.

If the heat insulating material 22 is of an integral ring shape and can take a closed structure in vacuum, the seal bellows 2
The part 7 can be omitted.

The heat insulating members 22, 23a and 23b are made of ceramic or the like, and are arranged at appropriate locations at several locations on the inner circumference.

The portion of the stator where the cryogenic cooling surface is formed, that is, the number of stages of the stator to be cooled can be arbitrarily determined by changing the position where the heat insulating seal ring 21 is inserted. It can be set in consideration of the balance between the exhaust performance required for the molecular pump and the refrigerating capacity of the refrigerator 24 used.

In the embodiment shown in FIG. 1, the basic structure of the molecular pump is such that turbo blades 11 as moving blades are provided on the intake port 2 side.
A thread groove-shaped component part 14a of the rotor 14 on the exhaust port 3 side
I explained using the compound type molecular pump,
By extending the structure of the turbo-blade 11 part to the whole molecular pump, even a turbo-type molecular pump in which the basic structure of the rotor and the stator is composed only of the turbo-blade, a part of the stator can be easily cooled to a very low temperature May be formed.

FIG. 2 shows an embodiment of a molecular pump in which a rotor and a stator have a cryogenic cooling surface formed in a part of a stator in a drag-type molecular pump having a basic structure having only a thread groove shape. It is the longitudinal cross-sectional view shown. As in the example of FIG. 1, the range of the extremely low-temperature cooling surface of the stator can be arbitrarily set by arbitrarily changing the insertion position of the heat insulating seal ring 21.

FIG. 3 shows that, in the same type of molecular pump structure as that of FIG. 1, the cryogenic cooling surface of the stator is set closer to the molecular pump inlet 2 than the position of the molecular pump inlet 2 of the rotor. It shows an embodiment formed to be extended. 1 can be easily configured by adding the upper cooling stator ring 18 to the configuration of the embodiment shown in FIG. 1 and changing the shape of the heat insulating material 23a in the case of FIG. 1 like the heat insulating material 23b.

In any of the configurations shown in FIGS. 1 to 3,
Also, in a turbo-type molecular pump in which the basic structure of a rotor and a stator (not shown) is constituted only by turbo blades, according to the molecular pump of the present invention, a part of the stator has an extremely low temperature (about 60K to 123K). Since the cooling surface is formed, the gas exhausted by the molecular pump is not affected at all by a decrease in conductance, and on the other hand, it is possible to have an improved exhaust performance for water.

[0038]

As apparent from the above description, according to the present invention, a conventional molecular pump is combined with a cooling panel (cooling trap) in order to obtain a structure in which a cryogenic cooling surface is provided in a part of the stator. The exhaust performance of gases other than water does not decrease as the conductance of the gas by the cooling panel decreases as in the case of the conventional structure. The exhaust performance for gas having a small molecular weight such as hydrogen or helium can be further improved by direct and effective cooling.

Exhaust performance of gas having a small molecular weight such as hydrogen and helium can be improved by adopting a structure in which a heat insulating seal ring 21 for preventing these gases from being diffused back to the inlet side of the molecular pump is adopted. It can be further improved.

According to the molecular pump of the present invention, it is possible to improve the exhaust performance for all kinds of gas in one molecular pump structure, and to provide a molecular pump having a very useful design structure in industry. Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating the structure of a molecular pump according to the present invention in a composite molecular pump.

FIG. 2 is a longitudinal sectional view for explaining the structure of the molecular pump according to the present invention in a drag type molecular pump.

FIG. 3 is a longitudinal sectional view illustrating a structure of a molecular pump according to the present invention in which a cooling surface of a stator is extended toward an intake port side in a compound molecular pump.

FIG. 4 is an enlarged longitudinal sectional view of a heat insulating seal structure in the molecular pump according to the present invention.

FIG. 5 is a longitudinal sectional view showing an example of a combination of a molecular pump and a cooling trap according to a conventional technique.

FIG. 6 is a longitudinal sectional view showing an example of a conventional molecular pump in which a cooling trap is arranged inside a pump container.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump container 2 Intake port 3 Exhaust port 4 Vacuum processing apparatus 11 Turbo blade 13 Cooling stator blade 14 Rotor 15 Stator 16, 17a, 17b, 18 Cooling stator ring 21 Heat insulating seal ring 22, 23a, 23b Heat insulating material 24 Refrigerator 26a, 26b Insulation ring 27 Seal bellows

Claims (5)

[Claims] A rotor having rotor blades rotatably disposed in a pump container having an inlet and an outlet, and a stator having fixed blades disposed between the rotor blades;
A molecular pump of a type in which gas molecules are exhausted by rotating a rotor, wherein an extremely low-temperature cooling surface is formed in a part of a stator. 2. A compound molecular pump having a turbo-blade structure on the intake side and a thread groove on the exhaust port side, or a drag-type molecular pump having a thread groove shape on the exhaust port side. 2. The molecular pump according to claim 1, wherein the molecular pump is any one of a turbo type molecular pump including only turbo blades. 3. The cryogenic cooling surface of the stator is formed so as to extend in the direction toward the inlet of the molecular pump from the position of the rotor closer to the inlet of the molecular pump. The molecular pump as described. 4. The cryogenic cooling surface is formed using a one-stage helium refrigerator.
The molecular pump according to any one of claims 1 to 3. 5. The molecular pump according to claim 4, wherein a pulse tube refrigerator is used as the one-stage helium refrigerator.