CN116576110A

CN116576110A - Vacuum pump

Info

Publication number: CN116576110A
Application number: CN202310073318.1A
Authority: CN
Inventors: 杉浦哲郎; 大渕真志; 盐川笃志
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2022-02-09
Filing date: 2023-02-07
Publication date: 2023-08-11
Also published as: EP4239197A1; JP2023116194A; TW202346713A; KR20230120576A

Abstract

Provided is a vacuum pump capable of satisfactorily discharging powder contained in a gas from a rotor chamber. A vacuum pump (1) is provided with: a pump housing (6) having a rotor chamber (5) inside; a pair of Roots rotors (8) disposed in the rotor chamber (5); and a pair of rotation shafts (9) supporting a pair of Roots rotors (8). The pump housing (6) has a gas inlet (12) and a gas outlet (13) that communicate with the rotor chamber (5), and a connection (25) between an inner wall (22) forming the rotor chamber (5) and an inner wall (23) forming the gas outlet (13) is located on or outside a rotor Center Line (CL) extending through the Rotation Center (RC) and the bottom dead center (LP) of each Roots rotor (8).

Description

Vacuum pump

Technical Field

The present invention relates to a vacuum pump, and more particularly, to a vacuum pump suitable for use in exhausting a process gas used for manufacturing a semiconductor device, a liquid crystal panel, an LED, a solar cell, and the like.

Background

In the manufacturing process of manufacturing semiconductor devices, liquid crystal panels, LEDs, solar cells, and the like, a process gas is introduced into a process chamber to perform various processes such as etching and CVD. The process gas introduced into the process chamber is exhausted by a vacuum pump. In general, the vacuum pump used in these manufacturing processes requiring high cleanliness is a so-called dry vacuum pump that does not use oil in a gas flow path. As a typical example of such a dry vacuum pump, there is a positive displacement vacuum pump in which a pair of roots rotors disposed in a rotor chamber are rotated in opposite directions to each other to transfer a gas.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2010-101321

Technical problem to be solved by the invention

The process gas may contain a powder composed of by-products. Such powder flows into the vacuum pump together with the process gas. Most of the powder is discharged from the vacuum pump together with the process gas, but a part of the powder stays in the rotor chamber and gradually accumulates in the rotor chamber. Powder is deposited on the inner wall of the rotor chamber and the outer surface of the roots rotor, and as a result, rotation of the roots rotor may be hindered.

Disclosure of Invention

Accordingly, the present invention provides a vacuum pump capable of satisfactorily discharging powder contained in a gas from a rotor chamber.

Technical means for solving the technical problems

In one embodiment, there is provided a vacuum pump including: a pump housing having at least one rotor chamber therein; at least one pair of roots rotors disposed within the rotor chamber; and at least one pair of rotation shafts supporting the at least one pair of roots rotors, the pump housing having a gas inlet and a gas outlet communicating with the rotor chambers, a connection portion between an inner wall forming the rotor chambers and an inner wall forming the gas outlet being located on a rotor center line extending through a rotation center and a bottom dead center of each roots rotor or located outside the rotor center line.

In one embodiment, the width of the gas outlet is greater than the width of the gas inlet.

In one embodiment, the at least one pair of roots rotors is at least one pair of two-lobe roots rotors, and an angle of a straight line from the rotation center to the connecting portion with respect to the rotor center line is in a range of 0 degrees to 35 degrees.

In one embodiment, the at least one pair of roots rotors is at least one pair of three-lobe roots rotors, and an angle of a straight line from the rotation center to the connecting portion with respect to the rotor center line is in a range of 0 degrees to 45 degrees.

In one embodiment, the at least one pair of roots rotors includes a pair of first roots rotors and a pair of second roots rotors disposed on a downstream side of a center line of the first roots rotors extending in a gas conveying direction, the at least one rotor chamber includes a first rotor chamber in which the pair of first roots rotors are disposed and a second rotor chamber in which the pair of second roots rotors are disposed, the pump housing has a first gas inlet and a first gas outlet communicating with the first rotor chamber and a second gas inlet and a second gas outlet communicating with the second rotor chamber, a first connection portion forming an inner wall of the first rotor chamber and an inner wall of the first gas outlet is located outside a center line of the first rotors extending through a rotation center and a bottom dead center of each first roots rotor, a second connection portion forming an inner wall of the second rotor chamber and an inner wall of the second gas outlet is located on a second center line extending through a rotation center and a bottom dead center of each second roots rotor, or a width of the second rotor is located outside the second gas outlet.

Effects of the invention

According to the present invention, the width of the gas outlet communicating with the rotor chamber becomes large, and powder contained in the gas is less likely to stay in the rotor chamber. As a result, the powder is discharged from the rotor chamber together with the gas, and the amount of powder deposited in the rotor chamber can be reduced.

Drawings

Fig. 1 is a cross-sectional view showing an embodiment of a vacuum pump apparatus.

Fig. 2 is a cross-sectional view taken along line A-A of fig. 1.

Fig. 3 is a cross-sectional view showing another embodiment of a connection portion between an inner wall forming the rotor chamber and an inner wall forming the gas outlet.

Fig. 4 is a cross-sectional view showing still another embodiment of a connection portion between an inner wall forming a rotor chamber and an inner wall forming a gas outlet.

Fig. 5 is a cross-sectional view showing another embodiment of the gas outlet.

Fig. 6 is a cross-sectional view showing one embodiment of a three-lobe roots rotor.

Fig. 7 is a cross-sectional view showing another embodiment of the vacuum pump apparatus.

Fig. 8 is a sectional view taken along line B-B of fig. 7.

Fig. 9 is a cross-sectional view taken along line C-C of fig. 7.

Symbol description

1. Vacuum pump

2. Motor with a motor housing having a motor housing with a motor housing

2A motor rotor

2B motor stator

5. 5A-5E rotor chambers

6 pump housing

8. 8A-8E Roots rotor

9 rotation shaft

12. 12A-12E gas inlets

13. 13A-13E gas outlets

14. Motor casing

16. Gear housing

17. Bearing

18. Bearing

20. Gear wheel

22. Inner wall of pump housing

23. Inner wall of gas outlet

25. Connecting part

CL rotor center line

Center of rotation of RC Roots rotor

Bottom dead center of LP Roots rotor

Center point of CP rotor chamber

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a cross-sectional view showing an embodiment of a vacuum pump apparatus. The vacuum pump apparatus of the embodiments described below is a positive displacement vacuum pump apparatus. In particular, the vacuum pump apparatus shown in fig. 1 is a so-called dry vacuum pump apparatus that does not use oil in a gas flow path. The vaporized oil in the dry vacuum pump apparatus does not flow to the upstream side, and thus can be applied to a manufacturing apparatus of a semiconductor device that requires high cleanliness.

As shown in fig. 1, the vacuum pump apparatus includes a vacuum pump 1 and a motor 2 for driving the vacuum pump 1. The vacuum pump 1 includes a pump housing 6 having a rotor chamber 5 therein, a pair of roots rotors 8 disposed in the rotor chamber 5, and a pair of rotary shafts 9 supporting the pair of roots rotors 8. Each roots rotor 8 and each rotation shaft 9 may be an integral structure. In fig. 1, only one roots rotor 8 and one rotation shaft 9 are illustrated, but a pair of roots rotors 8 are disposed in the rotor chamber 5 and supported by a pair of rotation shafts 9, respectively. The motor 2 is coupled to one of a pair of rotation shafts 9. In one embodiment, the pair of motors 2 may be coupled to the pair of rotation shafts 9.

The roots rotor 8 of the present embodiment is a single stage pump rotor, but in one embodiment, the roots rotor 8 may be a multistage pump rotor.

The pump housing 6 has a gas inlet 12 and a gas outlet 13 communicating with the rotor chamber 5. The gas inlet 12 is connected to a chamber (not shown) that should be filled with a feed. In one example, the gas inlet 12 is connected to a process chamber of a semiconductor device manufacturing apparatus, and the vacuum pump 1 is used for exhausting a process gas introduced into the process chamber.

The vacuum pump 1 further includes a gear housing 16 located outside the side wall 6A of the pump housing 6. A pair of gears 20 that mesh with each other are disposed inside the gear housing 16. In addition, only one gear 20 is depicted in fig. 1. These gears 20 are fixed to the rotation shaft 9. The motor 2 is rotated by a motor driver, not shown, and one rotation shaft 9 coupled to the motor 2 is rotated in the opposite direction with respect to the other rotation shaft 9 not coupled to the motor 2 via the gear 20.

The rotation shaft 9 is rotatably supported by a bearing 17 held by one side wall 6A of the pump housing 6 and a bearing 18 held by the other side wall 6B of the pump housing 6. The motor 2 has a motor housing 14 located outside the side wall 6B of the pump housing 6, and a motor rotor 2A and a motor stator 2B disposed in the motor housing 14.

In one embodiment, a pair of motors 2 are provided, each coupled to a pair of rotation shafts 9. The pair of motors 2 are rotated in opposite directions in synchronization by a motor driver, not shown, and the pair of rotary shafts 9 and the pair of roots rotors 8 are rotated in opposite directions in synchronization. The gear 20 in this case functions to prevent the synchronous rotation of the roots rotor 8 from being out of order due to sudden external factors.

When the roots rotor 8 rotates by the motor 2, gas is sucked into the pump housing 6 from the gas inlet 12. By means of the rotating roots rotor 8, gas is transported from the gas inlet 12 to the gas outlet 13.

Fig. 2 is a cross-sectional view taken along line A-A of fig. 1. As shown in fig. 2, each roots rotor 8 of the present embodiment is a two-lobe roots rotor. The gas inlet 12 is located on one side of the pump housing 6 and the gas outlet 13 is located on the opposite side of the pump housing 6. A pair of roots rotors 8 are located between the gas inlet 12 and the gas outlet 13. The roots rotor 8 is not in contact with the inner wall 22 of the pump housing 6 forming the rotor chamber 5, and the two roots rotors 8 are not in contact with each other either. The roots rotors 8 rotate in opposite directions as indicated by arrows in the rotor chamber 5.

As the roots rotor 8 rotates, a closed space is formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5. The gas flowing in from the gas inlet 12 fills the closed space, and the gas is transported from the gas inlet 12 to the gas outlet 13 by rotating the pair of roots rotors 8 in opposite directions. By continuously carrying out the transportation of the gas in such a closed space, the gas is exhausted by the vacuum pump 1.

The gas inlet 12 and the gas outlet 13 communicate with the rotor chamber 5. The inner wall 23 forming the gas outlet 13 is connected to the inner wall 22 forming the rotor chamber 5. As shown in fig. 2, the connection 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is located outside the rotor center line CL. The rotor center line CL is a straight line extending through the rotation center RC and the bottom dead center LP of each roots rotor 8. The bottom dead center LP of the roots rotor 8 corresponds to the lowermost end of the rotating roots rotor 8. Here, "located outside of the rotor center line CL" means at a position crossing the rotor center line CL from the center point CP of the rotor chamber 5.

The width W2 of the gas outlet 13 is larger than the width W1 of the gas inlet 12. For example, the width W2 of the gas outlet 13 is 1.1 to 2.0 times, preferably 1.7 times, the width W1 of the gas inlet 12.

Examples of the gas to be processed by the vacuum pump 1 of the present embodiment include a process gas used in a semiconductor device manufacturing apparatus such as a CVD apparatus and an etching apparatus. The process gas contains a powder composed of by-products. As can be seen from fig. 2, since the width W2 of the gas outlet 13 is larger than the width W1 of the gas inlet 12, powder is difficult to stay in the rotor chamber 5, and as a result, powder is difficult to accumulate in the rotor chamber 5. Therefore, according to the present embodiment, it is possible to prevent the occurrence of a rotation failure (for example, a rotation stop) of the roots rotor 8 due to the accumulation of the powder in the rotor chamber 5.

In the present embodiment, each roots rotor 8 is a two-lobe roots rotor. In order to convey the gas from the gas inlet 12 to the gas outlet 13, a closed space needs to be formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5. From this point of view, the connection 25 forming the inner wall 22 of the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is closer to the gas outlet 13 than to the gas inlet 12. The angle α of the straight line NL from the rotation center RC to the connecting portion 25 with respect to the rotor center line CL is in the range of 0 degrees to 35 degrees. In one embodiment, the connection 25 may also be located on the rotor centerline CL.

Although the width W2 of the gas outlet 13 is larger than the width W1 of the gas inlet 12, as described above, a closed space is formed between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5, and therefore, the exhaust performance of the vacuum pump 1 is not substantially reduced.

In the embodiment shown in fig. 2, the arrangement of the rotor center line CL and the connection portion 25 associated with one of the two roots rotors 8 is described, but the arrangement of the rotor center line and the connection portion associated with the other roots rotor 8 is also the same, and therefore, the repetitive description and the illustration of the symbols are omitted.

As shown in fig. 3, the connection portion 25 forming the inner wall 22 of the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 may have a circular arc-shaped cross section. Alternatively, as shown in fig. 4, the connection portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 may have a chamfered cross section. According to the shapes shown in fig. 3 and 4, turbulence of the gas is less likely to occur, and the powder can be smoothly conveyed to the gas outlet 13.

In the embodiment shown in fig. 2 to 4, the inner wall 23 forming the gas outlet 13 is parallel to the rotor center line CL, and the width of the gas outlet 13 is constant. As shown in fig. 5, in one embodiment, the inner wall 23 forming the gas outlet 13 may be inclined outward with the distance from the center point CP of the rotor chamber 5. That is, the width of the gas outlet 13 may be gradually increased together with the distance from the center point CP of the rotor chamber 5. By forming the shape as described above, the gas containing the powder can smoothly pass through the gas outlet 13.

As shown in fig. 6, the roots rotor 8 may be a three-lobe roots rotor. In the embodiment shown in fig. 6, the connection portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is also located on or outside the rotor center line CL extending through the rotation center RC and the bottom dead center LP of each roots rotor 8. The configuration of the embodiment of fig. 6, which is not specifically described, is the same as that of the embodiment described with reference to fig. 2, and thus, a repetitive description thereof will be omitted.

As in the embodiment described with reference to fig. 2, it is necessary to form a closed space between the outer surface of the roots rotor 8 and the inner wall 22 forming the rotor chamber 5. From this point of view, in the embodiment shown in fig. 6, the angle α of the straight line NL from the rotation center RC to the connecting portion 25 with respect to the rotor center line CL is in the range of 0 degrees to 45 degrees.

Although not shown, the roots rotor 8 may be a four-lobe or more roots rotor. In this case, the connection portion 25 between the inner wall 22 forming the rotor chamber 5 and the inner wall 23 forming the gas outlet 13 is also located on or outside the rotor center line CL extending through the rotation center RC and the bottom dead center LP of each roots rotor 8. Since the width of the gas outlet 13 is larger than the width of the gas inlet 12, the powder is difficult to stay in the rotor chamber 5, and as a result, the powder is difficult to accumulate in the rotor chamber 5.

Fig. 7 is a cross-sectional view showing another embodiment of the vacuum pump 1. The vacuum pump 1 of this embodiment is a multistage vacuum pump. The description of the embodiment with reference to fig. 1 to 6 is also applicable to the structure and operation of the present embodiment, and thus, the repetitive description thereof is omitted.

As shown in fig. 7, the vacuum pump 1 includes: a pump housing 6 having a plurality of rotor chambers 5A to 5E therein; a plurality of pairs of Roots rotors 8A-8E disposed in the rotor chambers 5A-5E, respectively; and a pair of rotation shafts 9 supporting the pairs of roots rotors 8A to 8E. The roots rotors 8A to 8E and the rotation shaft 9 may be an integral structure. In fig. 1, only one set of roots rotors 8A to 8E and a rotary shaft 9 are shown, but a plurality of pairs of roots rotors 8A to 8E are disposed in the rotor chambers 5A to 5E, respectively, and supported by a pair of rotary shafts 9. The motor 2 is coupled to one of a pair of rotation shafts 9. In one embodiment, the pair of motors 2 may be coupled to the pair of rotation shafts 9, respectively.

The roots rotors 8A to 8E and the rotor chambers 5A to 5E are arranged along the gas transport direction. That is, the roots rotor 8A and the rotor chamber 5A are located on the most upstream side in the conveying direction of the gas in the pump housing 6. The Roots rotor 8B and the rotor chamber 5B are located on the downstream side of the Roots rotor 8A and the rotor chamber 5A, the Roots rotor 8C and the rotor chamber 5C are located on the downstream side of the Roots rotor 8B and the rotor chamber 5B, the Roots rotor 8D and the rotor chamber 5D are located on the downstream side of the Roots rotor 8C and the rotor chamber 5C, and the Roots rotor 8E and the rotor chamber 5E are located on the downstream side of the Roots rotor 8D and the rotor chamber 5D. The roots rotor 8E and the rotor chamber 5E are located at the most downstream side in the gas conveying direction in the pump housing 6.

The pump housing 6 has: a gas inlet 12A and a gas outlet 13A communicating with the rotor chamber 5A; a gas inlet 12B and a gas outlet 13B communicating with the rotor chamber 5B; a gas inlet 12C and a gas outlet 13C communicating with the rotor chamber 5C; a gas inlet 12D and a gas outlet 13D communicating with the rotor chamber 5D; and a gas inlet 12E and a gas outlet 13E communicating with the rotor chamber 5E. The gas outlet 13A communicates with the gas inlet 12B via a flow path not shown, the gas outlet 13B communicates with the gas inlet 12C via a flow path not shown, the gas outlet 13C communicates with the gas inlet 12D via a flow path not shown, and the gas outlet 13D communicates with the gas inlet 12E via a flow path not shown.

When the motor 2 rotates the roots rotors 8A to 8E, gas is sucked into the rotor chamber 5A through the gas inlet 12A. The gas is compressed in sequence by the roots rotors 8A to 8E in the rotor chambers 5A to 5E, and is discharged from the pump housing 6 through the gas outlet 13E.

Fig. 8 is a sectional view taken along line B-B of fig. 7. As shown in fig. 8, the roots rotors 8A to 8E of the present embodiment are three-lobe roots rotors. The connection portion 25A of the inner wall 22A forming the rotor chamber 5A and the inner wall 23A forming the gas outlet 13A is located outside the rotor center line CL1 passing through the rotation center RC1 and the bottom dead center LP1 of the roots rotor 8A. The angle α1 of the straight line NL1 from the rotation center RC1 of the roots rotor 8A to the connecting portion 25A with respect to the rotor center line CL1 is in the range of 0 degrees to 45 degrees. The width W4 of the gas outlet 13A is larger than the width W3 of the gas inlet 12A.

Fig. 9 is a cross-sectional view taken along line C-C of fig. 7. As shown in fig. 9, the connection portion 25E of the inner wall 22E forming the rotor chamber 5E and the inner wall 23E forming the gas outlet 13E is located outside the rotor center line CL2 passing through the rotation center RC2 and the bottom dead center LP2 of the roots rotor 8E. In one embodiment, the connection portion 25E may be located at the rotor center line CL2. The angle α2 of the straight line NL2 from the rotation center RC2 of the roots rotor 8E to the connection portion 25E with respect to the rotor center line CL2 is in the range of 0 degrees to 45 degrees, and is smaller than the angle α1 shown in fig. 8. The width W6 of the gas outlet 13E is larger than the width W5 of the gas inlet 12E.

Although not shown, the connection portion between the inner wall forming the rotor chamber 5B and the inner wall forming the gas outlet 13B, the connection portion between the inner wall forming the rotor chamber 5C and the inner wall forming the gas outlet 13C, and the connection portion between the inner wall forming the rotor chamber 5D and the inner wall forming the gas outlet 13D are located outside the rotor center line or on the rotor center line, respectively.

According to the embodiment described with reference to fig. 7 to 9, the width of the gas outlets 13A to 13E is larger than the width of the gas inlets 12A to 12E, respectively, and therefore, powder is difficult to stay in the rotor chambers 5A to 5E, and as a result, powder is difficult to accumulate in the rotor chambers 5A to 5E.

As can be seen from a comparison of fig. 8 and 9, the width W4 of the gas outlet 13A shown in fig. 8 is larger than the width W6 of the gas outlet 13E shown in fig. 9. This is based on the simulation results of the following powder flows: the simulation result of the powder flow shows that when the width of the gas outlet is increased on the low pressure side and the width of the gas outlet is made relatively small on the atmospheric pressure side, the discharge of the powder is promoted. According to the present embodiment, powder can be discharged from the pump housing 6 through the rotor chambers 5A to 5E in order.

The relation gas of the widths of the gas outlets 13A to 13E is not particularly limited as long as the width of the gas outlet 13A is larger than the width of the gas outlet 13E. For example, the width of the gas outlets 13A, 13B, 13C may be equal to each other and larger than the width of the gas outlets 13D, 13E. In other examples, the widths of the gas outlets 13A, 13B, 13C, 13D, and 13E may be gradually reduced in accordance with the conveying direction of the gas in the pump housing 6.

The vacuum pump 1 shown in fig. 7 is a five-stage vacuum pump, but the number of stages of the roots rotor 8 is not particularly limited. For example, the vacuum pump 1 may be a two-stage vacuum pump having two pairs of roots rotors, or may be a multi-stage vacuum pump having six or more pairs of roots rotors.

The above-described embodiments are described with the object that a person having ordinary knowledge in the art to which the present invention pertains can practice the present invention. As long as those skilled in the art are able to implement the respective modifications of the above-described embodiments, the technical idea of the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the described embodiments, but is to be construed as the broadest scope of the technical idea defined according to the scope of the claims.

Claims

1. A vacuum pump is characterized by comprising:

a pump housing having at least one rotor chamber therein;

at least one pair of roots rotors disposed within the rotor chamber; and

at least one pair of rotating shafts supporting the at least one pair of Roots rotors,

the pump housing has a gas inlet and a gas outlet in communication with the rotor chamber,

the connection portion of the inner wall forming the rotor chamber and the inner wall forming the gas outlet is located on a rotor center line extending through the rotation center and the bottom dead center of each Roots rotor, or is located outside the rotor center line.

2. A vacuum pump according to claim 1, wherein,

the width of the gas outlet is greater than the width of the gas inlet.

3. A vacuum pump according to claim 1 or 2, wherein,

the at least one pair of roots rotors is at least one pair of two-lobe roots rotors, and an angle of a straight line from the rotation center to the connecting portion with respect to the rotor center line is in a range of 0 degrees to 35 degrees.

4. A vacuum pump according to claim 1 or 2, wherein,

the at least one pair of roots rotors is at least one pair of three-lobe roots rotors, and an angle of a straight line from the rotation center to the connecting portion with respect to the rotor center line is in a range of 0 degrees to 45 degrees.

5. A vacuum pump according to claim 1 or 2, wherein,

the at least one pair of Roots rotors includes a pair of first Roots rotors and a pair of second Roots rotors disposed downstream of the pair of first Roots rotors in a gas transport direction,

the at least one rotor chamber includes a first rotor chamber configured with the pair of first roots rotors and a second rotor chamber configured with the pair of second roots rotors,

the pump housing has a first gas inlet and a first gas outlet in communication with the first rotor chamber and a second gas inlet and a second gas outlet in communication with the second rotor chamber,

the first connection portion forming the inner wall of the first rotor chamber and the inner wall of the first gas outlet is located outside a first rotor center line extending through the rotation center and bottom dead center of each first roots rotor,

the second connection portion forming the inner wall of the second rotor chamber and the inner wall of the second gas outlet is located on a second rotor center line extending through the rotation center and the bottom dead center of each second Roots rotor, or is located outside the second rotor center line,

the width of the first gas outlet is greater than the width of the second gas outlet.