JPH11230086A - Vacuum pump and circulatory vacuum system therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent particles from flowing to the outside of a vacuum pump even when the particles are generated at a particle generation section in the vacuum pump by providing a particle outflow preventing means in the vacuum pump. SOLUTION: When a main spindle 4 is dropped on the upper and lower emergency bearings 21, 22 in a turbo-molecular pump, particles may be possibly generated. Particle filters 23, 24 are provided on the plane communicated with the exhaust passages of the emergency bearings 21, 22 so that the generated particles do not flow to the outside of the turbo-molecular pump. Even if an unexpected accident such as a rush of the atmospheric air occurs and the main spindle 4 drops on the upper and lower emergency bearings 21, 22 to generate particles, the particles can be arrested by the particle filters 23, 24, thereby the particles are prevented from flowing to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vacuum pump,
In particular, the present invention relates to a vacuum pump suitable for a circulating vacuum system that circulates and reuses a process gas, and a circulating vacuum system using the vacuum pump.

[0002]

2. Description of the Related Art A recent semiconductor manufacturing apparatus tends to use a large amount of process gas as the diameter of a semiconductor wafer increases, but only a part of the introduced process gas contributes to the reaction. And most of the remaining is discharged unreacted. Therefore, development of a circulating vacuum system in which a part of the discharged process gas is returned to the vacuum chamber again to increase the utilization rate of the unreacted process gas has been advanced.

[0003]

One of the problems of the above circulating vacuum system is that particles generated in the vacuum chamber, the exhaust line, and the circulating line enter the vacuum chamber together with the circulating gas. Since mixing of particles into the vacuum chamber causes deterioration of characteristics of a device to be manufactured, it is required to minimize mixing of the particles.

[0004] Considering the generation of particles in a vacuum pump, when a magnetic bearing is used for the bearing portion, a small amount of particles are generated in a normal operation state.
If an unexpected accident such as entry into the atmosphere occurs and the rotor falls onto an emergency bearing (such as a ball bearing or a slide bearing), particles may be generated. If such particles are generated in a vacuum pump used in the circulating vacuum system, the particles may enter the vacuum chamber together with the circulating gas.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents particles from flowing out of the vacuum pump even when the particles are generated in a particle generating portion such as an emergency bearing in a vacuum pump. It is an object of the present invention to provide a vacuum pump capable of performing the above-described operations and a circulating vacuum system using the vacuum pump.

[0006]

According to the first aspect of the present invention, there is provided a vacuum pump having a particle outflow preventing means for preventing particles generated in the vacuum pump from flowing out. The vacuum pump is characterized by being provided.

According to a second aspect of the present invention, there is provided the vacuum pump according to the first aspect, wherein the vacuum pump is a turbo molecular pump, and the means for preventing particle outflow is a particle filter and / or a labyrinth structure. I do.

According to a third aspect of the present invention, in the vacuum pump according to the first aspect, the vacuum pump is a molecular drag pump, and the particle outflow preventing means is a particle filter and / or a labyrinth structure. I do.

According to a fourth aspect of the present invention, a process gas is introduced into a vacuum chamber to react with an object to be processed in the vacuum chamber, and the process gas is exhausted from the vacuum chamber by a vacuum pump. A circulating vacuum system configured to return a part of the exhausted process gas into the vacuum chamber again, wherein the vacuum pump according to claim 1 is used as a vacuum pump. Circulating vacuum system.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a structural example of a turbo-molecular pump which is a vacuum pump of the present invention. As shown in the drawing, the turbo molecular pump has a blade exhaust portion L formed by a rotor R and a stator S inside a pump casing 1.
₁ and a screw groove exhaust portion L ₂ , and the exhaust side of the screw groove exhaust portion L ₂ is an exhaust port 2 of the pump casing 1.
It communicates with 0. The rotor R includes a main shaft 4 and a rotating tubular portion 5 that rotates integrally therewith. The stator S is composed of a stator main body having a fixed cylindrical portion 3 surrounding the main shaft 4 and a base 2.

On the outer peripheral portion of the upper portion of the rotary cylindrical portion 5, a rotary blade 12 is provided.
Are integrally provided to constitute the impeller 13. On the other hand, on the inner surface of the pump casing 1, stationary blades 15 are arranged alternately with the rotating blades 12 with fixed blade spacers 14 interposed therebetween.
Thus, the blade pumping section L ₁ which performs exhaust by interactions with a stationary blade 15 which is stationary and the rotating blades 12 rotating at a high speed is formed. Further, the rotary tubular portion 5 is integrally provided with a screw groove portion 18 extending downward. On the other hand, a thread groove spacer 19 surrounding the outer periphery of the thread groove 18 is arranged on the stator S. This thread groove pumping section L ₂ which performs exhaust by dragging action of the screw groove 18 rotating at a high speed is formed.

A drive motor 6 is provided between the main shaft 4 and the fixed cylindrical portion 3, and an upper radial bearing (magnetic bearing) 7 and a lower radial bearing (magnetic bearing) 8 are provided above and below the driving motor 6. An axial bearing 11 having a target disk 9 and upper and lower electromagnets 10a and 10b provided on the stator S side is arranged. An upper radial sensor 16 is arranged near the upper part of the upper radial bearing 7, and a lower radial sensor 17 is arranged near the lower part of the lower radial bearing 8. In addition, emergency bearings (for example, ball bearings and slide bearings) are provided vertically to support the main shaft 4 in an emergency.
21 and 22 are arranged.

With the above configuration, the main shaft 4 is supported by the upper radial bearing 7, the lower radial bearing 8 and the axial bearing 11 in a non-contact manner, and rotates at a high speed under active control of five shafts.

In the turbo-molecular pump having the above structure, in a normal operation state, the main shaft 4 is supported by the upper radial bearing 7, the lower radial bearing 8, and the axial bearing 11 in a non-contact manner. However, if an unexpected accident such as entry into the atmosphere occurs as described above and the main shaft 4 falls on the upper and lower emergency bearings 21 and 22, particles may be generated.

In order to prevent the generated particles from flowing out of the turbo molecular pump, particle filters 23 and 24 are provided on the surfaces of the emergency bearings 21 and 22 communicating with the exhaust passage. As a result, when an unexpected accident such as entry into the atmosphere occurs, the main shaft 4 falls on the upper and lower emergency bearings 21 and 22 and particles are generated.
It is captured at 24 and does not flow out.

As means for preventing the particles generated by the emergency bearings 21 and 22 from flowing out to the outside, in addition to the provision of the particle filters 23 and 24, the emergency bearings 21 and 22 may be connected to a portion communicating with the exhaust passage of the pump. The provision of the labyrinth portion 25 is also suitable as a means for preventing particles from flowing out. That is, by providing the labyrinth portion 25, particles generated in the emergency bearings 21 and 22 are removed from the labyrinth portion 25.
Does not flow out into the exhaust passage.

In the above-described example, the emergency bearings 21 and 22 are assumed as the particle generation unit. By providing the particle outflow prevention means, the particles can be effectively prevented from flowing out to the outside.

FIG. 2 is a view showing a structural example of a molecular drag pump which is a vacuum pump of the present invention. This molecular drag pump has a casing 3 as shown in the figure.
1, a rotor R and a stator S are provided inside the rotor R.
A screw shaft 36 is formed on the outer periphery of a main shaft 34 and a rotary cylindrical portion 35 that rotates integrally with the main shaft 34, and is composed of an impeller 33. The stator S is composed of a stator main body having a fixed cylindrical portion 32 surrounding a main shaft 34.

A driving motor 37 is provided between the main shaft 34 and the fixed cylindrical portion 32, and upper and lower radial bearings (magnetic bearings) are provided above and below the driving motor 37.
38 and a lower radial bearing (magnetic bearing) 39 are provided.
And upper and lower electromagnets 40a, 40 provided on the stator S side
An axial bearing 42 having a point b is disposed. An upper radial sensor 43 is arranged near the upper part of the upper radial bearing 38, and a lower radial sensor 44 is arranged near the lower part of the lower radial bearing 39. In addition, emergency bearings (for example, ball bearings and slide bearings) 45 and 46 are arranged vertically to support the main shaft 34 in an emergency.

With the above configuration, the main shaft 34 is supported in a non-contact manner by the upper radial bearing 38, the lower radial bearing 39, and the axial bearing 42, and rotates at a high speed under active control of five shafts. As a result, the impeller 33 rotates at a high speed, and exhaust is performed by the drag action of the screw groove 36.

In the molecular drag pump having the above structure, in a normal operation state, the main shaft 34 is supported by the upper radial bearing 38, the lower radial bearing 39, and the axial bearing 42 in a non-contact manner. However, if an unexpected accident such as entry into the atmosphere occurs and the main shaft 34 falls on the upper and lower emergency bearings 45 and 46, generation of particles is considered.

To prevent the generated particles from flowing out of the molecular drag pump, particle filters 47 and 48 are provided on the surfaces communicating with the exhaust passages of the emergency bearings 45 and 46. As a result, when an accident such as intrusion into the atmosphere occurs and the main shaft 34 falls on the upper and lower emergency bearings 45 and 46 and particles are generated, the particles are caught by the particle filters 47 and 48 and externally. No spill.

As means for preventing the particles generated by the emergency bearings 45 and 46 from flowing out to the outside, in addition to the provision of the particle filters 47 and 48, the emergency bearings 45 and 46 may be connected to a portion communicating with the exhaust passage of the pump. The provision of the labyrinth part 49 is also suitable as a means for preventing particles from flowing out. That is, by providing the labyrinth portion 49, particles generated by the emergency bearings 45 and 46 are removed from the labyrinth portion 25.
Does not flow out into the exhaust passage.

In the above example, the emergency bearings 45 and 46 are assumed as the particle generating portion. However, a portion such as a particle filter or a labyrinth portion is connected to a portion communicating with the exhaust passage where a particle is expected to be generated by the molecular drag pump. By providing the particle outflow prevention means, the particles can be effectively prevented from flowing out to the outside.

In the above-described example, both the particle filter and the labyrinth portion are provided. However, if either of the particles can be sufficiently prevented from flowing out, either one of them may be used.

FIG. 3 is a diagram showing an example of the configuration of a circulating vacuum system configured to return a part of the process gas into the vacuum chamber again. In FIG. 3, 51 is a vacuum chamber, 54 is an APC valve, 55 is a vacuum pump, 56 is a foreline valve, 57 is a roughing pump, 58 is a circulation line, 59 is a shutoff valve, and 60 is a flow control valve. A shower head 53 for injecting a process gas and a wafer 52 as an object to be processed are arranged in a vacuum chamber 51.

In the circulating vacuum system having the above structure, the roughing pump 57 operates with the shut-off valve 59 closed.
After the inside of the vacuum chamber 51 is roughly evacuated, the vacuum pump is activated to evacuate the inside of the vacuum chamber 51 to a predetermined degree of vacuum. Subsequently, a process gas is supplied from the shower head 53 to the surface of the wafer 52 to form a film on the surface of the wafer 52. At the same time, the process gas in the vacuum chamber 51 is exhausted by the vacuum pump 55, and a part of the flow rate of the process gas Q ₂ Is returned into the vacuum chamber 51 through the circulation line 58 and the shutoff valve 59. Thereby, the vacuum chamber 51
The sum of the flow rate Q _{1 of the} process gas supplied from the outside from the shower head 53 inside and the above-mentioned circulation flow rate Q ₂ , Q ₁ + Q ₂
Is injected and the flow rate Q ₁ adjusted by the flow adjustment valve 60 is
Is discharged outside through the roughing pump.

In the circulating vacuum system having the above-described structure, the vacuum pump 55 is provided with the particle outflow prevention means such as the particle filter and the labyrinth portion, and the air enters the vacuum pump 55 by using a turbo molecular pump or a molecular drag pump. Even if an unexpected accident occurs and particles are generated in the vacuum pump 55,
Since the generated particles are prevented from flowing out by the particle outflow prevention means, the particles pass through the circulation line 58 together with the process gas and pass through the vacuum chamber 51.
And the inside of the vacuum chamber 51 is not contaminated by particles.

[0029]

As described above, according to the first to third aspects of the present invention, a particle filter, a labyrinth structure and the like for preventing particles generated in the vacuum pump from flowing out of the vacuum pump. Is provided, it is possible to prevent the particles from flowing out, and to provide a vacuum pump suitable when the region into which the gas exhausted by the vacuum pump flows is an environment that dislikes particle contamination. .

According to the fourth aspect of the present invention, the vacuum pump of the circulating vacuum system is provided with a particle outflow prevention means such as a particle filter or a labyrinth structure inside the vacuum pump according to the first to third aspects. The inside of the chamber is not contaminated by particles generated in the vacuum pump.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structural example of a turbo-molecular pump of the present invention.

FIG. 2 is a view showing a structural example of a molecular drag pump of the present invention.

FIG. 3 is a diagram showing a configuration example of a circulation vacuum system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pump casing 2 Base 3 Fixed cylindrical part 4 Main shaft 5 Rotating cylindrical part 6 Driving motor 7 Upper radial bearing 8 Lower radial bearing 9 Target disk 10a, b Electromagnet 11 Axial bearing 12 Rotating blade 13 Impeller 14 Fixed blade spacer 15 Fixed blade 16 Upper radial sensor 17 Lower radial sensor 18 Screw groove 19 Screw groove spacer 20 Exhaust port 21 Emergency bearing 22 Emergency bearing 23 Particle filter 24 Particle filter 25 Labyrinth part 26 Hermetic connector 31 Casing 32 Fixed cylindrical part 33 Impeller 34 Main shaft 35 Rotating cylindrical portion 36 Screw groove 37 Drive motor 38 Upper radial bearing 39 Lower radial bearing 40a, b Electromagnet 41 Target disk 42 Axial bearing 43 Upper bearing Arusensa 44 lower radial sensor 45 emergency bearings 46 emergency bearing 47 particle filter 48 the particle filter 49 labyrinth portion R rotor S stator L ₁ blade pumping section L ₂ thread groove exhaust portion 51 vacuum chamber 52 the wafer 53 showerhead 54 APC valve 55 vacuum Pump 56 Foreline valve 57 Roughing pump 58 Circulation line 59 Shutoff valve 60 Flow control valve

Claims (4)

[Claims] 1. A vacuum pump comprising a vacuum pump provided with a particle outflow preventing means for preventing particles generated in the vacuum pump from flowing out. 2. The vacuum pump according to claim 1, wherein the vacuum pump is a turbo-molecular pump, and the particle outflow prevention means has a particle filter and / or a labyrinth structure. 3. The vacuum pump according to claim 1, wherein the vacuum pump is a molecular drag pump,
A vacuum pump wherein the particle outflow prevention means has a particle filter and / or labyrinth structure. 4. A process gas is introduced into a vacuum chamber and reacted with an object to be processed in the vacuum chamber. The process gas is exhausted from the vacuum chamber by a vacuum pump, and a part of the exhausted process gas is removed. A circulating vacuum system configured to return to the inside of the vacuum chamber again, wherein the vacuum pump according to any one of claims 1 to 3 is used as the vacuum pump.