JP3444971B2 - Turbo molecular pump - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo molecular pump used in semiconductor manufacturing equipment and the like.

[0002]

2. Description of the Related Art Conventionally, a turbo molecular pump of this type is often used for evacuation in a film forming apparatus for semiconductor production, for example, there is one disclosed in Japanese Utility Model Laid-Open No. 1-124396. The pump described in the publication is composed of a rotor having a plurality of moving blades rotatably arranged in a pump casing having an intake port and an exhaust port, and a stator having stationary blades fixed between the moving blades. A stage is formed, and the inside of the vacuum chamber connected to the intake port of the turbo molecular pump is exhausted by the cooperation of the moving blade and the stationary blade due to the rotation of the rotor.

[0003]

In the conventional film forming apparatus, particles such as reaction products and dust are generated in the apparatus. In this case, the particles are sucked into the turbo molecular pump side which is the exhaust system. The Rukoto. When the particles are sucked into the turbo molecular pump, they collide with the rotor blades rotating at high speed and are pulverized into fine dust. A part of the fine dust may be scattered into the vacuum chamber due to the impact of colliding with the moving blade and adhere to the wafer during the film forming operation.

When the fine dust adheres to the wafer in this manner, the wafer becomes defective or its quality is deteriorated, so that the generation of the fine dust greatly affects the yield of semiconductors.

Therefore, as a means for preventing fine dust from entering the vacuum chamber, it is conceivable to separate the vacuum chamber and the turbo molecular pump from each other through a suction pipe having a bent portion. In this case, However, the pipe conductance is reduced and the effective pumping speed tends to be halved, which is not preferable.

There is a case where a baffle 40 separate from the above-mentioned device is arranged on the upstream side of the above-mentioned device. This baffle 40 is for preventing the backflow of fluid, and as shown in FIG.
Are arranged in parallel at intervals, or as shown in (b), a plurality of conical plates 42 are arranged concentrically at intervals. However, these baffles 40 cannot completely prevent the fine dust from entering the vacuum chamber. That is, in the baffle 40 in which the flat plates 41 are arranged in parallel, the fine dust that has collided with the moving blade is almost scattered in the tangential direction of the collision portion, and the fine dust that is scattered in the flat plate 41 direction easily passes between the flat plates 41. I will end up. Further, also in the baffle 40 in which a plurality of conical plates 42 are arranged, similarly, fine dust can be scattered along the conical plates 42, so that it passes between the conical plates 42 and enters the vacuum chamber for the fine dust. Intrusion of can not be effectively prevented.

The present invention has been made in view of the above-mentioned conventional problems, and it is possible to prevent the effective exhaust speed from being lowered as much as possible, and the fine dust generated in the apparatus is stored in the vacuum chamber. An object of the present invention is to provide a turbo molecular pump that can prevent intrusion and improve the yield of semiconductors and the like.

[0008]

The technical means taken by the present invention to solve the above-mentioned problems are the intake port 2 and the exhaust port 3.
A turbo molecular pump including a rotor 9 having a rotor blade 11 rotatably arranged in a pump casing 1 having a rotor, and a stator 14 having a stator blade 13 fixed between the rotor blades 11. The stationary blade disk 22 for preventing fine dust for preventing the fine dust scattered by 11 from entering the vacuum chamber 4 side is positioned so as to be located upstream of the moving blade 11a at the most upstream stage. It is provided in the pump casing 1.

Furthermore, the vane disk 22 for preventing the minute dust
Has a plurality of stationary blade blades 25 radially provided from the central disk portion 23, and each stationary blade blade 25 has a predetermined gap L1 with respect to the moving blades 11 of the moving blade 11. In the two vane blades 25 that are inclined with respect to the direction of rotation A and that are forward and backward, the front portion 26 of the front vane blade 25 and the rear portion 27 of the rear vane blade 25 are It is that they overlap each other.

Moreover, the vane disk for preventing the fine dust
The gap L between the stationary blade blade 25 of 22 and the moving blade 11a of the most upstream stage
Is preferably set below the mean free path of the sucked gas molecules.

Further, the vane disk 22 for preventing the minute dust is also provided.
Gap between the stationary blade blade 25 and the rotor blade 11a of the most upstream stage Lmm
Is set to L ≦ 0.05 / P, where PTorr is the suction pressure at the suction port 2.

[0012]

In the turbo molecular pump of the present invention, when minute dust is generated from the constituent members including the vacuum chamber 4,
The minute dust collides with the moving blade 11a at the most upstream stage rotating at a high speed and scatters in the rotating direction A of the moving blade 11a and in the vertical direction. The minute dust scattered to the vacuum chamber 4 side comes into contact with and is blocked by the stationary blade disc 22 for stopping the minute dust, and the minute dust crosses over the stationary blade disc 22 for preventing the minute dust, and the vacuum chamber 4 There is no invasion to the side. Therefore, when the film forming operation is performed in the vacuum chamber 4, there is no possibility that fine dust is inadvertently attached to the wafer.

Further, the vane disk 22 for preventing the fine dust
The gap L between the stationary blade blade 25 and the rotor blade 11a at the most upstream stage is
When the average free path of the gas to be sucked is set to be equal to or less than the mean free path, the stationary blade blade 25 for preventing fine dust exerts a pump function similarly to the stationary blade 13, and the stationary blade blade 25 for preventing fine dust is provided.
Even though the blade is provided at the upstream stage of the moving blade 11, it is possible to effectively prevent the effective exhaust speed from decreasing.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 4, reference numeral 1 denotes a pump casing, and a flange attached to the vacuum chamber 4 at the upper portion thereof.
An intake port 2 is formed in the flange 1a, and an exhaust port 3 is formed below the intake port 2 on the opposite side.

6 is a turbo molecular pump stage on the intake port 2 side,
Denoted at 7 are thread groove pump stages arranged below the turbo molecular pump stage 6 (at the rear side on the downstream side), and a rotatable rotor 9 is a rotor blade 9 at the intake port 2 side and an exhaust port 3 side. It is a composite type integrally formed with a cylindrical thread groove rotor 15.

That is, the rotor 9 is rotatably attached to the shaft 12 of the drive motor fixed to the pump casing 1 side, and the rotor blades 11 are arranged in a plurality of stages on the outer periphery of the upper portion thereof. And it is projected horizontally. Further, below the rotor blade 11 of the rotor 9, the cylindrical thread groove rotor 15 having a spiral thread groove formed on the outer periphery is integrally suspended.

On the inner circumference of the pump casing 1, there are stationary blades 13 which are alternately positioned with the multi-stage moving blades 11, a distance piece 13a interposed between the stationary blades 13 and the thread groove rotor 15.
A stator portion 17 whose inner peripheral surface has a small gap with the thread groove rotor 15 so as to surround the stator blade 17, the distance piece 13a, and the stator portion 17.
14 are configured.

The turbo molecular pump stage 6 is constituted by the moving blades 11 and the stationary vanes 13, and the screw groove pump stage 7 is constituted by the screw groove rotor 15 and the stator portion 17.
Is configured. In the screw groove pump stage 7, a screw groove is provided on the inner peripheral surface of the stator portion 17, and the rotor facing the screw groove is provided.
The outer peripheral surface of 15 may be simply a cylindrical surface.

Reference numeral 22 denotes a stationary blade disk for preventing fine dust, which is provided at a position upstream of the moving blade 11a in the uppermost stream stage. As shown in FIGS. 1 to 3, the stationary vane disk 22 is composed of a circular disk portion 23 in the central portion and a plurality of flat blade vane blades 25 radially provided. The outer peripheral portion of 25 is fixed to the inner peripheral surface of the pump casing 1.

Each stationary blade blade 25 is inclined parallel to the rotation direction A of the moving blade 11a as shown in FIG.
The stationary blade blades 25 have a predetermined distance L1 from each other. Further, in the two front and rear vane blades 25, the front portion 26 of the front vane blade 25 and the rear vane blade 25 are arranged.
The rear portion 27 and the rear portion 27 are overlapped with each other, and by providing the overlap 28, when the stationary vane disk 22 for preventing fine dust is viewed from the upstream side in a plan view, the uppermost stage moving blade 11a cannot be visually observed. It is like this. In addition, it is preferable that the diameter D of the disk portion 23 of the vane disk 22 for preventing the minute dust is set to be equal to the inner diameter of the turbo molecular pump stage 6 (the central portion having no exhaust function). There is.

A gap L (mm) between the downstream end surface of the stationary blade blade 25 of the stationary blade disk 22 for preventing fine dust and the upstream end surface of the moving blade 11b formed on the most upstream blade 11a. Is L
≦ 0.05 / P (where P is the pressure at the intake port (Torr)) is set. Here, 0.05 / P is the mean free path (mm) of air at the intake port 2 when the gas to be exhausted is air.
By setting the gap L to 0.05 / P or less,
The above-mentioned vane disk 22 for preventing fine dust can function as a vane stage of a turbo molecular pump stage, and it is possible to prevent a decrease in exhaust speed by providing the vane disk 22 for preventing fine dust. Becomes

For example, a turbo molecular pump is generally operated at an intake port pressure P of 0.1 Torr or less. In this case, if P = 0.1 is substituted into the above conditional expression, L
≤ 0.5 mm. On the other hand, the mean free path of air at P = 0.1 corresponds to 0.5 mm. Therefore, the gap L is set to L = 0.
By setting it to 5 mm, the stationary blade disk 22 for preventing fine dust can be made to function as the stationary blade stage of the turbo-molecular pump stage, and setting the gap L to 0.5 mm is effective for processing and It is not a value that causes difficulty during assembly.

The turbo-molecular pump of the present embodiment has the above-mentioned structure. Next, the case where the turbo-molecular pump is used to perform the film forming operation in the vacuum chamber 4 will be described. First, in the exhaust process, the rotor 9 rotates at high speed due to the operation of the drive motor, and the turbo molecular pump stage 6
And the screw groove pump stage 7 perform the vacuum evacuation action, and the gas in the vacuum chamber 4 is exhausted.

During this evacuation step, as shown in FIG. 3B, particles such as reaction products and dust generated in the film forming apparatus are assumed.
When 30 is sucked by the turbo molecular pump, high speed (peripheral speed about 30
The blade 11b of the blade 11 rotating at 0 m / s) collides and is crushed. Since the moving blade 11 rotates at a high speed, the particles 30 are almost crushed by colliding with the most upstream moving blade 11a, and the pulverized fine dust receives momentum from the moving blade 11b. Although it scatters, the scattering range of the fine dust is the range in the rotation direction A and the vertical direction of the moving blade 11a.

Therefore, the stationary blade blades provided radially are provided.
Since 25 is overlapped with each other as described above, the fine dust scattered on the upstream side must be the stationary blade blade.
The fine dust that collides with the 25 and is reliably shut off and scatters in any direction is used to remove the fine blade dust of the static blade blades 22 of the static blade disc 22.
There is no invasion from the stationary vane disk 22 to the vacuum chamber 4 side via the gap L1 of the blade 25.

Since the stationary blade blades 25 of the stationary blade disk 22 for preventing fine dust are provided in a thin flat plate shape and parallel to each other, the exhausted gas passes through the gap L1 and conducts. Can be prevented as much as possible.
Further, since the gap L between the stationary blade blade 25 and the moving blade 11a is set to be equal to or less than the mean free path of air molecules, the pump function is also provided between the stationary blade blade 25 and the moving blade 11a. Is exhibited, and it becomes possible to effectively prevent a decrease in the effective pumping speed.

Further, in the above embodiment, since the vane disk 22 for preventing the fine dust is provided in the pump casing 1, as compared with the case where the vacuum chamber 4 and the turbo molecular pump are connected by piping. The exhaust system becomes compact, the number of flanges to be connected is reduced, and the manufacturing cost can be significantly reduced, and the entire device can be made compact, and the manufacturing cost of the device can be reduced.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the stationary blade blade 25 of the stationary blade disk 22 for preventing fine dust is fixed to the disk portion 23. As an example, the inclination angle α of each vane blade 25 is changeably provided, and the inclination angle α of each vane blade 25 is adjusted so that the vane disk 22 for preventing fine dust can be used. It is also possible to provide the function of a conductance valve.

As the pump stage, the turbo molecular pump stage 6 and the thread groove pump stage 7 are exemplified, but it goes without saying that a turbo molecular pump having only the turbo molecular pump stage 6 may be used.

[0030]

INDUSTRIAL APPLICABILITY As described above, in the present invention, at the upstream position with respect to the uppermost stage moving blade, it is possible to prevent fine dust scattered by the moving blade from entering the vacuum chamber side. Since the stationary blades for preventing minute dust are provided, it is possible to reliably prevent minute dust from entering the vacuum chamber and adhering to the wafers during the film forming work in the vacuum chamber, thus improving the semiconductor yield. It becomes possible to improve.

Moreover, since the stationary blades for preventing minute dusts are provided in the pump casing, the whole apparatus can be compared with the conventional structure in which the vacuum chamber and the turbo molecular pump are connected by piping. It is possible to achieve simplification and size reduction, and it is possible to shorten the distance between the vacuum stage and the pump stage constituted by the moving blades and the stationary blades, and it is possible to prevent the effective pumping speed from decreasing.

Further, when the gap between the stationary blade blade of the stationary blade disc for preventing fine dust and the moving blade of the most upstream stage is set to be equal to or less than the mean free path of sucked gas, Even though the vane disk for preventing fine dust exerts a pumping function similar to the vane between blade stages, and the vane for preventing fine dust is provided on the upstream side of the blade, effective exhaust It is possible to effectively prevent a decrease in speed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an essential part of an embodiment of the present invention.

FIG. 2 is a plan view of a vane disk for preventing fine dust.

FIG. 3 shows an embodiment of the present invention, (a) is a cross-sectional view showing a relationship between a stationary blade disk for preventing fine dust and a moving blade in the most upstream stage, and (b) is a moving blade in the most upstream stage. FIG. 6 is a cross-sectional view showing a state in which minute dust is scattered.

FIG. 4 is a sectional front view showing the whole of the present invention.

FIG. 5 is a schematic cross-sectional view of a baffle showing a conventional example, and (a) and (b).

[Explanation of symbols]

1 ... Pump casing, 2 ... Intake port, 3 ... Exhaust port, 11 ...
Rotor blade, 11a ... most upstream rotor blade, 13 ... stationary blade, 15 ... rotor, 14
... Stator, 22 ... Stator blade disk for preventing fine dust, 23 ... Disc part, 25 ... Stator blade blade, A ... Rotation direction

Claims (4)

(57) [Claims] 1. A rotor (9) having a rotor blade (11) rotatably arranged in a pump casing (1) having an intake port (2) and an exhaust port (3), and the rotor blade (11). In a turbo molecular pump provided with a stator (14) having a stationary blade (13) fixed in between, a minute dust scattered by the moving blade (11) is prevented from entering the vacuum chamber (4) side. The vane disk (22) for preventing minute dust to prevent
So that it is located upstream of the rotor blade (11a) at the most upstream stage,
A turbo-molecular pump, wherein the turbo-molecular pump is provided in the pump casing (1). 2. A vane disk (22) for preventing the minute dust.
Has a plurality of stationary blade blades (25) radially provided from the central disk portion (23), and each stationary blade blade (25) is
In the two vane blades (25) and (25) that are inclined with respect to the rotation direction (A) of the moving blade (11) and are arranged in front of and behind each other so as to have a predetermined gap (L1), The turbomolecular pump according to claim 1, wherein the front portion (26) of the front vane blade (25) and the rear portion (27) of the rear vane blade (25) overlap each other. . 3. A vane disk (22) for preventing the fine dust.
3. The turbo-molecular pump according to claim 2, wherein the gap L between the stationary blade blade (25) and the rotor blade (11a) at the most upstream stage is set to be equal to or less than the mean free path of the sucked gas molecules. 4. A vane disk (22) for preventing the minute dust.
The gap (L (mm)) between the stationary blade blade (25) and the rotor blade (11a) at the most upstream stage is L ≦ 0.05 / P, where P (Torr) is the suction at the suction port (2). The turbo molecular pump according to claim 2, which is set to (pressure).