JPH08232840A - Extremely high vacuum pump system - Google Patents

Abstract

PURPOSE: To realize an extremely high vacuum pump system which can obtain target pressure lower than conventional one. CONSTITUTION: A bath 1 to be exhausted is set in a vacuum condition by means of a rotational vacuum pump such as a turbo molecule pump 3 and a getter pump 2 composed of a gas adsorption metal and a beater. In such a vacuum pump system, a conductance adjusting means 4 is arranged between the bath 1 and a rotational vacuum pump for adjusting conductance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high vacuum pump system used for evacuation to generate an ultra-high vacuum or an ultra-high vacuum in the production of accelerators, semiconductors and the like.

[0002]

2. Description of the Related Art As a conventional technique for generating a high vacuum, a rotary vacuum pump such as a turbo molecular pump is generally used to exhaust gas by utilizing the viscosity of gas.
However, the method using the rotary vacuum pump can obtain only a smaller compression ratio (exhaust port pressure / intake port pressure) for hydrogen gas than other gases, so hydrogen gas remains in the exhaust tank and is necessary. Extremely high vacuum cannot be obtained.

For this reason, a getter pump is separately installed in the tank to be evacuated, and the gas sorption metal portion of the getter pump sorbs and removes residual hydrogen gas to obtain a necessary extremely high vacuum.

[0004]

However, in the conventional installation method of the exhaust tank and the rotary vacuum pump, the gas is easily back-diffused from the rotary vacuum pump side to the exhaust tank side to obtain a lower ultimate pressure. There was a problem that it was difficult.

An object of the present invention is to solve these problems and to provide an extremely high vacuum pump system capable of obtaining a lower ultimate pressure.

[0006]

In order to achieve the above object, the present invention provides a rotary vacuum pump such as a turbo molecular pump and a getter pump including a gas sorption metal part and a heating heater part to create an exhaust gas inside the tank to be evacuated. A vacuum pump system of a vacuum type is characterized in that a conductance adjusting means for adjusting conductance is interposed in a passage between the exhaust tank and the rotary vacuum pump.

[0007]

In the ultra-high vacuum pump system according to claim 1, since the conductance adjusting means is provided in the flow path between the tank to be evacuated and the rotary vacuum pump, the rotary vacuum pump is capable of roughing the tank to be evacuated. During the operation, the conductance is made large so that the exhaust capacity of the rotary vacuum pump is sufficiently exhibited, and when the pressure in the exhaust tank is lowered to exhaust the residual gas by the getter pump, the conductance is made small. It is possible to prevent back diffusion of gas from the rotary vacuum pump.

In the extremely high vacuum pump system according to the present invention, since the valve body can be held and controlled at an arbitrary forward / backward position, the suction side conductance of the rotary vacuum pump can be kept constant, and the valve can be kept constant. Since the bellows is connected between the back surface of the valve body and the inner surface of the valve housing so as to surround the shaft, the outside air leaks into the exhaust tank through the insertion hole of the valve shaft in the valve housing. Can be prevented.

In the extremely high vacuum pump system according to claim 3, since the rotary vacuum pump, the getter pump and the sputter ion pump are installed in the tank to be evacuated, the rotary vacuum pump is used as a rough reference, and the rotary vacuum pump uses pressure. When the exhaust gas reaches the limit of the ratio, the tank to be evacuated and the rotary vacuum pump are disconnected, and the inside of the tank to be evacuated can be made extremely high vacuum by the sputter ion pump and the getter pump.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

In the system diagram of FIG. 1, a getter pump 2 and a turbo molecular pump 3 are connected to an exhaust tank 1 via a conductance adjusting means 4. In an actual configuration, as shown in FIG. 2, the getter pump 2 may be installed inside the exhaust tank 1 or may be directly connected to the exhaust tank. The turbo molecular pump 3 is connected to the outside of the exhaust tank 1 and installed.

The conductance adjusting means 4 is a plate-shaped valve body 4
a, a valve shaft 4b, a bellows 4c and a valve housing 4d,
The valve shaft 4b slides in a sleeve 4e fitted in a hole provided in the valve housing 4d to move forward and backward, and can hold and control the valve body 4a at an arbitrary forward and backward position. Also, the valve shaft 4b
Can be moved back and forth to a position where the valve body 4a is seated on the valve seat 1a provided on the valve housing 4d, and the valve seat 1a is connected to the suction port of the turbo-molecular pump 3 so as to communicate therewith. In addition, 3a shows the impeller of a turbo molecular pump.

Next, the operation of the first embodiment of the present invention will be described.

When the exhaust tank 1 is set to an extremely high vacuum, the turbo molecular pump 3 first rough-evacuates the exhaust tank 1. The turbo molecular pump 3 has a structure similar to that of an axial flow compressor, and is composed of an impeller 3a that rotates at a rotational speed that is the same as the peripheral speed of a gas molecular speed, and a fixed blade corresponding thereto.

However, there is a limit to the low vacuum pressure that can be achieved by the turbo molecular pump 3, and in particular, the exhaust performance for low-molecular-weight gas such as hydrogen gas is poor. To obtain an ultra-high vacuum.

FIG. 3 shows an example of the relationship between the achievable vacuum pressure of the turbo molecular pump 3 and the getter pump 2 and the exhaust performance for hydrogen gas and methane gas. The exhaust performance of the turbo molecular pump 3 for hydrogen gas is TH, and the same. The exhaust performance for methane gas is TC, and the getter pump 2
The exhaust performance for hydrogen gas is shown by GH, and the exhaust performance for methane gas is shown by GC.

The adjustment by the conductance adjusting means 4 is performed as follows.

The conductance is the reciprocal of the suction resistance with respect to the turbo molecular pump 3. During the rough evacuation, the conductance adjusting means 4 is adjusted to separate the valve body 4a from the valve seat 1a so that the conductance becomes large.

After the pressure in the evacuated tank 1 has dropped to near the limit of the pressure ratio of the turbo molecular pump 3, a residual gas containing hydrogen gas having a light molecular weight as a main component remains in the evacuated tank 1. Therefore, the getter pump 2 is operated to exhaust the residual gas.

The getter pump 2 is a pump for adsorbing hydrogen gas on a metal plate and exhausting it. When the getter pump 2 is operated, the valve body 4a of the conductance adjusting means 4 is located close to the valve seat 1a. Is kept at a low value to prevent the gas from back-diffusing from the inlet of the turbo molecule 3, and at the same time, a gas that is difficult to be exhausted by the getter pump, such as methane or an inert gas, is exhausted.

Further, in the getter pump 2, when the hydrogen gas is sufficiently sorbed on the metal plate, the hydrogen gas exhausting capability is lowered. Therefore, in order to recover the lowered exhausting capability, the metal plate is heated and baked. Perform the operation to release the sorbed hydrogen gas.

When the baking and getter pump 2 is activated, it is better to increase the conductance so that the exhaust performance of the turbo molecule 3 can be utilized. Therefore, the conductance adjusting means 4 adjusts the conductance. In this way, in the extremely high vacuum region, the exhausted tank 1 can be maintained in the extremely high vacuum state by adjusting the conductance by the conductance adjusting means 4 to the optimum conductance.

The second embodiment of the present invention will be described with reference to the system diagram of FIG.

In addition to the getter pump 2, the turbo molecular pump 3 is connected to the evacuated tank 1 via a shutoff valve 6 and the sputter ion pump 5 is connected via an adjustable vacuum valve 7.

Here, the turbo molecular pump 2 is used as a rough reference, and in the extremely high vacuum region, the shutoff valve 6 is closed and the getter pump 2 and the sputter ion pump 5 evacuate.

The sputtering ion pump 5 uses titanium or the like for the cathode, and residual gas molecules such as hydrogen are trapped on the adhering surface of the cathode material sputtered by the discharge, or the residual gas molecules are implanted as ions into the cathode. The exhaust gas is exhausted by adjusting the temperature of the exhausted tank 1. The adjustable vacuum valve 7 interposed between the exhausted tank 1 and the exhausted tank 1 is adjusted so that the residual gas in the exhausted tank 1 is exhausted.

[0027]

As described above, according to the present invention, there is an effect that a lower ultimate pressure can be obtained without back diffusion of gas from the turbo molecular pump suction port side to the exhaust tank side in the extremely high vacuum region.

[Brief description of drawings]

FIG. 1 is a system diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of the above.

FIG. 3 is a graph showing an example of exhaust performances of a turbo molecular pump and a getter pump.

FIG. 4 is a system diagram of a second embodiment of the present invention.

[Explanation of symbols]

 1 Exhaust tank 2 Getter pump 3 Turbo molecular pump 4 Conductance adjusting means 4a Valve body 4b Valve shaft 4c Bellows 4d Valve housing 5 Sputter ion pump 6 Shut-off valve 7 Vacuum valve

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

Claims (3)

[Claims] 1. A vacuum pump system of a type in which a rotary vacuum pump such as a turbo molecular pump and a getter pump composed of a gas sorption metal part and a heater part are used to evacuate the inside of the tank to be evacuated. An extremely high vacuum pump system characterized in that a conductance adjusting means for adjusting conductance is interposed in a flow path between the rotary vacuum pump and the rotary vacuum pump. 2. The conductance adjusting means comprises: a valve housing that moves forward and backward toward a valve housing and a valve seat thereof; a valve shaft that controls the valve body to move forward and backward; and a back surface of the valve body that surrounds the valve shaft. The extremely high vacuum pump system according to claim 1, comprising a bellows connected to seal the interior of the valve casing. 3. The extremely high vacuum pump system according to claim 1, further comprising a sputter ion pump connected to the exhaust tank via an adjustable vacuum valve.