JP2002285987A - Small-size vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-size vacuum pump, having a combined vacuum pump evacuating from atmospheric pressure to ultra-high vacuum using a single pump small-sized and preventing corrosive gas for CVD process or the like from intruding into a motor part and a bearing part and enabling low cost manufacturing. SOLUTION: In a combined vacuum pump having a turbo molecular pump 4, a screwed groove pump 5 and a peripheral pump 6 are arranged in the order, from a suction port side in a pump housing 1 having a suction port 2 and a discharge port 3 and fixing rotors 7 of these pumps on a common shaft 9, the shaft 9 is supported by static pressure gas bearings 10, 11, and a bearing discharge port 13 is connected to a peripheral pump discharge side part. The bearing discharge port 13 has a lip part 17, comprised of a flange 15 fixed on the pump housing 1 and a disc spring shaped ring 16 fixed on the shaft 9 and elastically contacting on the flange 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small vacuum pump, and more particularly to a vacuum pump for a semiconductor manufacturing apparatus which can evacuate from an atmospheric pressure (approximately 10 ⁵ Pa) to an ultra-high vacuum (approximately 10 ⁻⁶ Pa or less). The present invention relates to a small vacuum pump suitable for exhausting harmful gas in a device or the like and obtaining a clean ultra-high vacuum.

[0002]

2. Description of the Related Art As shown in, for example, Japanese Patent Publication No. 7-101039, a vacuum pump suitable for exhausting harmful gases and obtaining a clean ultra-high vacuum in a vacuum apparatus for semiconductor manufacturing equipment and the like is disclosed. 2. Description of the Related Art In a pump housing having an intake port and an exhaust port, there is a pump housing in which a turbo molecular pump, a screw groove pump, and an overflow pump are sequentially arranged from the intake port side to the exhaust port side. Such a vacuum pump in which two or more types of pumps are connected in series and integrated is called a composite vacuum pump.

A turbo molecular pump is composed of a number of rotating blades (moving blades) protruding from an outer peripheral surface of a rotor and a number of fixed blades (static vanes) protruding from an inner peripheral surface of a pump housing. In addition,
The rotating wing and the fixed wing are usually manufactured by cutting an Al alloy block material using a processing machine such as a machining center. The thread groove pump includes a cylindrical groove having a thread groove formed on an outer peripheral surface of the rotor and an inner peripheral surface opposed to a ridge of the thread groove with a small gap. The thread groove may be provided on the stator, or may be provided on both the rotor and the stator.

[0004] The overflow pump comprises a number of radial blades projecting from the outer peripheral surface of the rotor and having radial concave portions, and a stator having a suction channel opposed to each of the radial blades. The shaft of the rotor (rotor of the pump unit) extends into the motor housing below the pump housing, and the extended portion forms a rotor shaft of the motor. Is driven to rotate by a motor stator disposed in the motor. In addition, since the rotor shaft rotates at high speed (tens of thousands of rpm), in order to avoid frictional heat generation in the bearing part, a bearing using a method of floating the shaft by gas pressure and supporting the shaft (hydrostatic gas bearing) may be used. is there.

[0005] The three types of series combined vacuum pumps have the capability of evacuating from atmospheric pressure to ultra-high vacuum with one unit. In addition,
In Japanese Patent Publication No. 7-101039, a bypass is provided between the turbo-molecular pump section and the overflow pump section, and an opening communicating with the turbo-molecular pump section is closed in the bypass path by the elastic force of a spring. A valve is provided. According to this, a large pressure difference generated in the thread groove pump portion in the early stage of operation opens the valve beyond the elasticity of the spring, and as a result, the bypass passage is opened and the exhaust gas flow rate increases, so that the exhaust gas is exhausted in a shorter time. can do.

[0006]

The above-mentioned conventional composite vacuum pump has the capability of evacuating from atmospheric pressure to ultra-high vacuum by itself, but there is still room for improvement in terms of compactness. Further, when a corrosive gas used for a CVD process or the like is suctioned and discharged in a semiconductor manufacturing apparatus or the like, the corrosive gas enters a motor portion or a bearing portion to corrode these portions, thereby shortening the life of the composite vacuum pump. There was a problem. Further, there is a problem that cutting the rotor blades and the fixed blades from the block material takes several hours to several tens of hours, and it is difficult to reduce the cost.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a compact vacuum pump in which a combined vacuum pump for evacuating from atmospheric pressure to ultrahigh vacuum with one unit is further downsized. Another object of the present invention is to provide a small vacuum pump that prevents corrosive gas for CVD processing or the like from entering a motor unit and a bearing unit, and a small vacuum pump that can be manufactured at low cost.

[0008]

The above object has been achieved by the present invention described below. (1) A turbo molecular pump, a screw groove pump and an overflow pump are sequentially arranged in a pump housing having an intake port and an exhaust port from the intake port side, and the rotors of these pumps are fixed to a common rotating shaft. A small vacuum pump, wherein the rotary shaft is supported by a static pressure gas bearing, and an exhaust port of the static pressure gas bearing is connected to an outlet side of the overflow pump.

(2) The exhaust port of the hydrostatic gas bearing has a lip comprising a flange fixed to the pump housing and a disc spring-shaped ring fixed to the rotating shaft and resiliently abutting the flange. (1) The small vacuum pump according to (1), (3) The small vacuum pump according to (2), wherein the mutual contact surface between the ring and the flange is coated with a resin having excellent chemical resistance (for example, fluororesin).

(4) One or both of the rotor blade and the fixed blade of the turbo molecular pump are formed by etching or pressing a plate material and then bending the blade portion. The compact vacuum pump according to any one of 3).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention (1), a turbo-molecular pump, a screw groove pump and an overflow pump are sequentially arranged in a pump housing having an intake port and an exhaust port from the intake port side. In the compound vacuum pump in which the rotor is fixed to a common shaft (rotating shaft), the shaft is supported by a static pressure gas bearing, and a bearing exhaust port (exhaust port of the static pressure gas bearing) is connected to the outlet of the overflow pump. Connected to the side. As a result, the exhaust flow from the bearing exhaust port merges with the exhaust flow from the overflow pump and goes to the exhaust port of the pump housing. When the exhaust flow velocity at the bearing exhaust port is large, the exhaust flow therefrom removes the gas at the outlet of the overflow pump to the exhaust port of the pump housing to reduce the pressure. That is, the part where the bearing exhaust port is connected to the outlet side of the overflow pump acts as an ejector (ejector vacuum pump).

In such an ejector, the compression ratio is 5 to 5.
Since the compression ratio of the overflow pump can be increased to about 10 and about 1.5 to 2.0, it is possible to reduce the number of stages of the overflow pump to 3 to 3 with the addition of the ejector without lowering the exhaust performance. It can be reduced by five stages, and therefore according to the invention,
The entire composite vacuum pump can be made more compact and compact. Further, since the viscous resistance of the gas to the rotation of the rotor on the high pressure side which causes heat generation is reduced, the heat generation is also reduced. Also, the gas at the outlet side of the overflow pump is purged to the exhaust port of the pump housing by the exhaust flow from the bearing exhaust port, so that harmful gases such as corrosive gas enter the bearing side and the motor side. Can be prevented.

In order to obtain the above-described effect of the ejector, the flow velocity condition at which the ejector action occurs is determined based on a well-known fluid engineering theory, and the dimensional shape of the bearing exhaust port is set so as to satisfy the flow velocity condition. Can be designed.
Further, according to the present invention (2), in the present invention (1), the bearing exhaust port is provided with a flange fixed to the pump housing and a disc spring-shaped ring fixed to the shaft and elastically abutting against the flange. And a lip consisting of According to this, in order to obtain the effect of the ejector, the gap between the lips may be appropriately set, and the gap between the lips is determined by the elasticity of the ring (disc spring),
It changes only depending on the exhaust pressure of the hydrostatic gas bearing and the force relationship of the centrifugal force applied to the ring due to the high-speed rotation of the shaft. Become.

Even when the operation of the vacuum pump is stopped (when the rotation of the shaft is stopped or the air supply to the static pressure gas bearing is stopped),
Since the ring abuts on the flange by its own elastic force, the gap of the lip is eliminated and the bearing exhaust port is closed, so that harmful gas such as corrosive gas does not enter the bearing side or the motor side. In the present invention (3), the present invention (2)
In the lip, the resin (eg, fluororesin) with excellent chemical resistance is provided on the mutual contact surface between the ring and the flange.
Was coated. This is preferable because the corrosion resistance of the mutual contact surface between the ring and the flange of the lip is enhanced, and the adhesion of the lip (the sealing property of the bearing exhaust port) can be favorably maintained for a long time.

In the present invention (4), the present invention (1) to
In any one of (3), one or both (preferably both) of the rotor and the fixed wing of the turbo-molecular pump are
It was manufactured in a sequential process of "etching or press punching of plate material → bending of wing portion". By doing so, the manufacturing cost of the composite vacuum pump can be significantly reduced, and a more inexpensive small vacuum pump can be provided.

[0016]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention. As shown in the drawing, in this embodiment, according to the present invention (1), a turbo molecular pump 4, a thread groove pump 5 and an overflow are provided in a pump housing 1 having an intake port 2 and an exhaust port 3 from an intake port side 2. In a compound vacuum pump in which pumps 6 are sequentially arranged and the rotors 7 of these pumps are fixed to a common shaft (rotating shaft) 9, the shaft 9 is composed of hydrostatic gas bearings 10 and 11.
(10 is a radial bearing, 11 is a thrust bearing), and a bearing exhaust port 13 is connected to the outlet side of the overflow pump 6.

The shaft of the rotor 7 extends into the motor housing 14 below the pump housing 1, and the extended portion becomes the shaft of the motor rotor 18, and the hydrostatic gas bearings 10, 1
While being supported by the motor housing 14 via the motor 1, the motor 1 is rotated by a motor stator 19 disposed in the motor housing 14. The turbo molecular pump 4 includes a number of rotating blades (moving blades) 4A protruding from the outer peripheral surface of the rotor 7 and a number of stationary blades (stationary vanes) 4 protruding from the inner peripheral surface of the pump housing 1.
B, and has an exhaust performance of reducing the inlet pressure to about 10 ⁻⁶ Pa or less (ultra-high vacuum) when the outlet pressure is about 1 Pa or less.

The thread groove pump 5 comprises a cylindrical groove 7 formed on the outer peripheral surface of the stator 8 and a cylindrical rotor 7 having an inner peripheral surface opposing a ridge of the groove with a small gap. When the pressure is about 10 ³ Pa or less, it has an exhaust performance of reducing the inlet pressure to about 1 Pa. The overflow pump 6 is composed of a number of radial blades protruding from the outer peripheral surface of the hollow portion of the rotor 7 and having radial concave portions, and a stator 8 having a suction flow path facing each of these blades. (10
⁽ Approximately ⁵ Pa), and has an exhaust performance of setting the inlet pressure to approximately 10 ³ Pa.

The overflow pump 6 conventionally requires 6 to 10 stages because the compression ratio per stage is about 1.5 to 2.0. Since the ejector is connected to the outlet side of the overflow pump 6 and the ejector is configured, it is sufficient that the number of overflow pump stages is 4 to 7 stages. In the present embodiment, the number of stages of the overflow pump = 5. Further, in this embodiment, according to the present invention (2), the bearing exhaust port 1
A lip 17 is provided at a connection portion of the overflow pump 6 with the outlet side of the overflow pump 3. The lip 17 is formed of a flange 15 fixed to the pump housing 1 and a disc spring-shaped ring 16 fixed to the shaft 9 and resiliently abutting the flange 15. In this embodiment, further, according to the present invention (3),
The mutual contact surface between the ring 16 and the flange 15 was coated with a fluororesin.

When the exhaust is stopped, as shown in FIG.
The lip 17 closes due to the elastic force of the ring 16 and the bearing exhaust port 1
3 is sealed. At the time of exhaust, as shown in FIG. 2B, the lip 1 is rotated until the centrifugal force due to the rotation of the shaft 9 and the exhaust pressure from the bearing exhaust port balance the elasticity of the ring 16.
7 is opened, and an ejector effect is exerted by the exhaust gas flow discharged from the formed gap.

In this embodiment, the present invention (4)
Rotor blade 4A, fixed blade 4B of the turbo molecular pump 4
In both cases, a thin SUS304 stainless steel hollow disk was cut into a predetermined etching allowance 21 in the manner shown in FIG.
After etching, the wing portion 20 was bent and manufactured, so that the manufacturing cost of the turbo-molecular pump portion could be significantly reduced.

[0022]

As described above, according to the present invention, there is an excellent effect that a composite vacuum pump can be obtained which is more compact and compact, has no corrosive gas entering the rotary drive portion, and can reduce the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a state of a lip portion when exhaust is stopped (a) and when exhaust is performed (b).

FIG. 3 is an explanatory view showing an example of a manufacturing procedure of a rotary wing and a fixed wing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pump housing 2 Intake port 3 Exhaust port 4 Turbo molecular pump 4A Rotor blade 4B Fixed blade 5 Screw groove pump 6 Overflow pump 7 Rotor 8 Stator 9 Shaft (rotating shaft) 10 Static pressure gas bearing (radial bearing) 11 Static pressure gas Bearing (thrust bearing) 12 Bearing inlet 13 Bearing exhaust 14 Motor housing 15 Flange 16 Ring 17 Lip 18 Motor rotor 19 Motor stator 20 Blade part 21 Etching allowance

Continued on the front page F term (reference) 3H022 AA01 BA06 CA14 CA21 CA22 CA58 DA00 DA04 DA14 3H031 DA01 DA02 DA05 DA07 EA00 EA06 FA01 FA03 FA14 FA32 FA34 FA36

Claims (4)

[Claims] 1. A turbo-molecular pump, a thread groove pump, and an overflow pump are sequentially arranged in a pump housing having an intake port and an exhaust port from the intake port side, and the rotors of these pumps are fixed to a common rotating shaft. A small vacuum pump, wherein the rotary shaft is supported by a static pressure gas bearing, and an exhaust port of the static pressure gas bearing is connected to an outlet side of the overflow pump. 2. An exhaust port of the hydrostatic gas bearing includes a flange provided in the pump housing and a disc spring-shaped ring fixed to the rotating shaft and resiliently abutting the flange. The miniature vacuum pump according to claim 1, further comprising a lip. 3. The miniature vacuum pump according to claim 2, wherein a mutual contact surface between the ring and the flange is coated with a resin having excellent chemical resistance. 4. The turbomolecular pump according to claim 1, wherein one or both of the rotor blades and the stationary blades are formed by etching or press-cutting a plate material and then bending the blade portion. A small vacuum pump according to any of the above.