JPH074384A - Compound molecular pump - Google Patents

Abstract

(57) [Abstract] [Purpose] In addition to suppressing the temperature rise of precision mechanical parts such as bearings, the simple structure prevents condensation and adhesion of reaction products to the rotor and stator of the thread groove pump part for durability, Improve reliability. [Structure] The stators 7a, 7b of the thread groove pump portion 3 are fixed by supports 9a, 9b, 9c made of a heat insulating material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite molecular pump used in a pressure range from a medium vacuum to an ultrahigh vacuum in an experimental research apparatus, an analytical measuring apparatus, and an industrial vacuum apparatus in the field of film formation in the semiconductor manufacturing industry. Regarding

[0002]

2. Description of the Related Art A conventional composite molecular pump used for exhausting a film forming apparatus such as an etching apparatus or a CVD apparatus is constructed as shown in FIG.

Reference numeral 1 denotes a housing, and the housing 1 is a housing cylindrical portion 1
c and a base 1d having a bottom cover,
An intake port 1a is formed in the upper part and an exhaust port 1b is formed in the lower part, and the turbo molecular pump unit 2, from the intake port 1a side,
And the thread groove pump portion, that is, the SGP portion 3 are sequentially arranged.

Reference numeral 4 denotes a rotary shaft, which is rotatably supported by magnetic bearings 5a and 5b. Ball bearings 5c and 5d are emergency bearings, and 10 is a motor.

Reference numeral 6 denotes a rotor of the composite molecular pump, which is fixed to the upper part of the rotary shaft 4 and includes a rotor blade 2a of the turbo molecular pump portion 2 and a cylindrical rotor 3a of the SGP portion 3. Have.

Reference numeral 7a denotes an outer stator of the SGP portion 3, 7b denotes an inner stator, and the stators 7a and 7b are provided with thread grooves 8a and 8b.

Further, the outer stator 7a is disposed inside the casing cylindrical portion 1c via a stationary blade fixing ring and the casing base portion 1d.
The inner stator 7b is fixed on the housing base 1d.

Here, all of these parts are made of aluminum alloy except for the casing inner cylindrical portion 1c.

Thus, when the composite molecular pump of this prior art is operated, the rotor 6 rotates, the gas is sucked and sucked from the intake port 1a, compressed and exhausted by the turbo molecular pump unit 2, and further in the SGP unit 3. The pressure is increased and the gas is discharged from the exhaust port 1b.

At this time, the rotor 3a rises in temperature due to frictional heat with the flowing gas, and this heat is transmitted to the opposing 7a and 7b.

However, the heat of the stators 7a and 7b is easily transferred to the housing 1, and the temperature of the stators 7a and 7b does not rise so much.

Therefore, there is a problem that the reaction products are condensed and adhered to the rotor facing surfaces of the stators 7a and 7b, and these are accumulated to hinder the rotation of the rotor and cause a failure.

Therefore, the stator of the SGP portion is heated and heated by a heater to prevent the adhesion to the gap.

[0014]

Since the conventional composite molecular pump described above is heated and heated by the heater, the temperature of the bearings (especially magnetic bearings) rotating at high speed and the precision mechanical parts such as the motor rises, and the parts are heated. Of the SGP inside the pump as well as the reliability and durability of the rotor are deteriorated, and the rotor is made of an aluminum alloy, which causes thermal expansion and strength deterioration at high temperatures.
When heating the stator, a large heater capacity is required, a temperature rise in the precision mechanism unit is suppressed to a minimum, and complicated temperature detection and control are required to raise the temperature of the SGP stator higher. Had the problem of.

The present invention solves the above problems, suppresses the temperature rise of the precision mechanical portion such as the bearing, and prevents the condensation and adhesion of the reaction products by raising the temperature of the SGP rotor and the SGP stator. Accordingly, it is an object of the present invention to provide a composite molecular pump having improved durability and reliability.

[0016]

In order to achieve the above object, the present invention is a composite structure in which a turbo molecular pump unit and a thread groove pump unit are sequentially arranged from the intake side in a housing having an intake port and an exhaust port. In the molecular pump, the stator of the thread groove pump portion is fixed by a support made of a heat insulating material.

[0017]

The temperature of the rotor rotating at a high speed rises due to the frictional heat generated by the heat generated from the motor and the bearing and the friction with the sucked gas, and the temperature of the opposing SGP stator is raised. Heat conduction is suppressed by the support made of a heat insulating material, and the SGP stator is kept at a high temperature.

Therefore, the condensation and deposition of reaction products on the SGP stator are prevented, and the heat of the SGP stator is not transmitted to the bearing and the motor side, so that the obstacle due to the temperature rise of the precision mechanism such as the bearing is avoided.

Further, since the outer surface of the pump does not reach a high temperature, the operator's burn is prevented and the safety is improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS.

Since the entire structure of the pump is substantially the same as that of the conventional pump, the different structure will be described below.

Reference numerals 9a and 9b denote supports for fixing the outer stator 7a, 9c denotes supports for fixing the inner stay 7b, and these supports 9a, 9b, 9c are made of ceramics having a small thermal conductivity, for example, Ibiden The ceramic composite has a trade name “Ceracom”, and one end surface is fixed to the outer stator 7a and the inner stator 7b, and the other end surface is fixed to the housing 1 and the like.

Next, the operation of this embodiment will be described.

When input to the motor 10, the rotor 6 rotates and gas is sucked from the intake port 1a, compressed and exhausted by the turbo molecular pump unit 2, further boosted in the SGP unit 3 and exhausted from the exhaust port 1b.

At this time, the cylindrical rotor 3a of the SGP portion 3
Rises in temperature due to frictional heat generated by friction with the flowing gas to a high temperature (around 100 ° C.) and the facing stator 7
The heat of a and 7b is the support 9a, 9b and 9c made of a heat insulating material.
As a result, the conduction is blocked, and the heat conduction to the bearings 5a, 5b, 5d, etc. which are kept at a high temperature and separated from each other is blocked.

Here, the stators 7a and 7b of the SGP portion 3 generate heat due to friction of the gas flowing through the SGP portion 3 and the rotor 3
It is heated by radiant heat from a and is radiated to the housing 9 and the like and radiated by heat conduction to the contact member. From this heat balance relational expression, when the gas flow rate is 500 SCCM, the support 9
The graph of FIG. 3 shows the relationship between the temperature Ta of the stator 7a and the temperature Tb of the stator 7b with respect to the thermal conductivity λ of a, 9b and 9c.

The temperature of the rotor 3a was 100 ° C. as a normal temperature when a gas was loaded.

In order to prevent the condensable gas sucked by the pump from adhering to the stators 7a and 7b, the temperature of these stators 7a and 7b must be set to 80 ° C. or higher.
From the graph of FIG. 3, λ needs to be 0.25 (W / mK) or less.

However, a material having a λ of 0.25 (W / mK) or less is practically unavailable.

Therefore, considering the respective shape factors Aa / ta, Ab / tb and Ac / tc of the support members 9a, 9b and 9c, the thermal conductivity λ is multiplied by this shape factor to obtain the converted thermal conductivity. λ (Aa / ta), λ (Ab / tb), λ
It has been found that the object is achieved when (Ac / tc) is 0.25 (W / mK) or less.

Aa, Bb and Cc are the support members 9a,
The cross-sectional areas of 9b and 9c, ta, tb, and tc are the respective support members 9
It is the length in the heat conduction direction of a, 9b, and 9c.

Therefore, the inventor of the present invention uses these support members 9a, 9
By adopting low thermal conductivity ceramics of λ = 0.96 (W / mK) as the materials of b and 9c, and by adopting the shapes of FIGS. 1 and 2, the converted thermal conductivity of each support member is 0.2.
It is expected to be 5 (W / mK) or less.

FIG. 4 shows the relationship between the gas flow rate during operation and the temperature Ta of the outer stator 7a and the temperature Tb of the inner stator 7b.

In FIG. 4, the horizontal axis represents the stators 7a and 7b.
Powers La and Lb due to the friction of the gas.

The vertical axis represents Ta and Tb, and shows the curves of Ta and Tb when the flow rate is changed.

L when the gas is N ₂ and the flow rate is 500 SCCM
a is 17 W and Lb is 56.5 W, at which time Ta is maintained at 92 ° C and Tb is maintained at 124 ° C.

As shown in FIG. 4, even if the gas flow rate changes, especially when the gas flow rate decreases and becomes zero, the temperatures 7a and 7b of the stators 7a and 7b are 80 ° C. or higher.
It was confirmed that the condensation and deposition of the reaction product on the 7b and the rotor 3a did not occur.

The stators 7a and 7b thus heated prevent condensation of reaction products in the exhaust gas, and since the heater for heating the stator is not used, the bearing does not become high in temperature, and the temperature is controlled. No need for auxiliary equipment.

The rotor 3a and the stators 7a, 7 are
In order to improve the heat exchange with b, the rotor 3a is made of aluminum alloy or the like and the stators 7a and 7b are made of carbon steel or stainless steel or the like, or an appropriate surface treatment is applied to increase the emissivity of the facing surface. be able to.

In this embodiment, the magnetic bearing type composite molecular pump is applied, but the present invention can also be applied to the ball bearing type composite molecular pump.

Also, in a composite molecular pump that uses a disk-shaped rotor instead of a screw-shaped groove pump as a spiral groove pump, the heat insulating material support method according to the present invention is applied to the support structure of the stator facing the disk-shaped rotor. it can.

[0042]

As described above, according to the present invention, in the composite molecular pump in which the turbo molecular pump section and the thread groove pump section are sequentially arranged from the intake side in the housing having the intake port and the exhaust port, Since the stator of the screw groove pump part is fixed by the support made of a heat insulating material, the heater for heating the stator is not used and the temperature rise of the precision mechanism part such as the bearing is suppressed and an auxiliary device for temperature control is required. There is an effect that the reaction product can be prevented from condensing and adhering to the SGP rotor and the SGP stator with a simple structure to improve durability and reliability.

[Brief description of drawings]

FIG. 1 is a front view of an entire half-section of a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part thereof.

FIG. 3 is a graph showing the thermal conductivity of the support and the temperature T of the inner and outer stators.
It is a graph which shows the relationship with a and Tb.

FIG. 4 is a power La caused by friction of gas between the inner and outer stators,
It is a graph which shows the relationship between Lb and temperature Ta, Tb.

FIG. 5 is a cross-sectional view of a conventional composite molecular pump.

[Explanation of symbols]

 1 Case 1a Inlet 1b Exhaust 2 Turbo molecular pump 3 Thread groove pump 7a, 7b Stator 9a, 9b, 9c Support

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[Procedure amendment]

[Submission date] July 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008] Here, these components the housing circular cylindrical portion 1c
All except aluminum alloy.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Motoaki Iizuka 3-2-25 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Osaka Vacuum Equipment Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A composite molecular pump in which a turbo molecular pump unit and a screw groove pump unit are sequentially arranged from an intake side in a housing having an intake port and an exhaust port, and a stator of the screw groove pump unit is made of a heat insulating material. A composite molecular pump characterized by being fixed by a support. 2. The composite molecular pump according to claim 1, wherein the heat insulating material is made of ceramics.