JP3156409B2 - Evacuation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pumping system for creating an ultra-high vacuum.

[0002]

2. Description of the Related Art In a field requiring a very clean atmosphere such as a surface analyzer or an epitaxial growth apparatus, an ultra-high vacuum of 10 ^-8 Pa or less is used. A sublimation pump using Ti (titanium) or the like may be used to create the ultra-high vacuum. As is well known, the Ti sublimation pump utilizes the fact that when Ti atoms are vapor-deposited, the vapor-deposited surface has an adsorbing effect. When the function stops, the next new vapor deposition surface is created on this vapor deposition surface, and the active gas is again adsorbed on the new vapor deposition surface. It creates a vacuum.

FIG. 2 shows a conventional evacuation system using a Ti sublimation pump. In the figure, a vacuum evacuation system A and an ultra-high vacuum evacuation system C are connected to a vacuum vessel 1 in which an ultra-high vacuum is created. The roughing exhaust system A is constituted by an oil rotary pump 13 as a main pump, and is attached to the vacuum vessel 1 via a valve 10. The ultra-high vacuum evacuation system C is composed of a Ti sublimation pump 31 and a turbo molecular pump 32 as main pumps, and an oil rotary pump 33 and the like are additionally provided as auxiliary pumps. And, like the roughing system A, it is connected to the vacuum vessel 1 via the valve 30.

In the vacuum evacuation system having such an evacuation system, the vacuum vessel 1 is first evacuated from atmospheric pressure to about 10 Pa by the oil rotary pump 13 by opening the valve 10. Subsequently, the valve 10 is closed and the valve 30 is closed.
open. At this time, the sublimation pump 31 is not operated. In this state, the gas is exhausted to about 10 ⁻⁴ Pa by the turbo molecular pump 32 and the oil rotary pump 33. The turbo-molecular pump to create a molecular flow by exhausting gas molecules from the pump outlet by a high-speed rotation of the rotor blades, 10 ^-4 Pa
The following high vacuum is created, and it is not a method of condensing gas molecules such as a cryopump on the low-temperature solid surface provided in the exhaust pipe. (Cryopump regeneration) A high vacuum can be created without worrying about the timing, and a relatively long maintenance time for re-emission work is not required. Suitable as a pump. When a high vacuum of about 10 ^-4 Pa is reached, the sublimation pump 31 is operated intermittently to gradually exhaust the gas to 10 ^-8 Pa by the adsorption action.

[0005]

In the conventional vacuum evacuation system, after rough evacuation is completed and a medium vacuum region of about 10 Pa is reached, a vacuum from the medium vacuum region to an ultra-high vacuum region of 10 ⁻⁸ Pa or less is obtained. It will be evacuated all at once with an ultra-high vacuum evacuation system. In this case, a large amount of gas molecules are adsorbed on the pipe wall of the piping constituting the ultrahigh vacuum evacuation system during the evacuation, particularly immediately after the start of evacuation with a low degree of vacuum. Then, 10 ^{−4 is obtained} by the above-described process.
When the gas is evacuated only by the turbo-molecular pump 22 to Pa, and then the sublimation pump 31 is operated to start ultra-high vacuum evacuation, these adsorbed molecules are gradually re-emitted little by little. Therefore, the sublimation pump 31 also adsorbs the gradually re-released molecules, so that the burden on the sublimation pump 31 has to be increased. Therefore, even if a new deposition surface is formed by operating the sublimation pump, the adsorption capacity of the deposition surface is reduced in a short time, and the next new deposition surface must be formed. Therefore, the operation interval (evaporation interval) of the sublimation pump 31 must be shortened, and the life of the sublimation pump is also shortened. In order to solve such a problem, as shown in FIG. 2, a cold trap made of liquid nitrogen or the like is provided between the sublimation pump 31 and the valve 30 to adsorb condensable gas such as moisture in the residual gas component. By doing so, the burden on the sublimation pump may be reduced. However, in a system provided with a liquid nitrogen cold trap in an ultra-high vacuum evacuation system, the liquid surface of the liquid nitrogen fluctuates due to evaporation of the liquid nitrogen in the cold trap, and the adsorbed gas may be released again. It is sufficient if this re-emitted gas can be completely adsorbed by the sublimation pump.However, if the evaporation of liquid nitrogen proceeds, a large amount of re-emitted gas molecules may be generated at one time. Could cause unexpected troubles. Therefore, there has been another problem that an operator must constantly monitor the liquid nitrogen so as not to cause such a fluctuation, or an additional automatic liquid nitrogen supply device must be provided.

The present invention solves the above-mentioned problems caused by gas molecules adsorbed on an ultra-high vacuum pumping system at once, and provides a vacuum pumping system capable of maintaining an ultra-high vacuum stably for a long time. Aim.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an ultra-high vacuum exhaust system using a sublimation pump and a turbo molecular pump as a main pump, and a rough pump using an oil rotary pump as a main pump. A vacuum exhaust system including a vacuum exhaust system is provided with an intermediate exhaust system having a higher exhausting performance than the rough exhaust system, and after performing exhaust by the intermediate exhaust system following the rough exhaust system. A means for switching to an ultra-high vacuum exhaust system is provided. Hereinafter, how the sputtering apparatus having this configuration operates will be described.

[0008]

In the ultra-high vacuum evacuation system of the present invention, after exhausting up to about 10 Pa in the rough evacuation system, before exhausting in the ultra-high vacuum evacuation system, an intermediate evacuation system consisting of another piping system is used. Exhaust. Then, the gas is evacuated to a high vacuum of about 10 ⁻⁴ Pa by the intermediate exhaust system and then exhausted by the ultra-high vacuum exhaust system. Therefore, the ultra-high vacuum evacuation system is not exposed to an atmosphere from medium vacuum to high vacuum where there are many adsorbed gas molecules, but is exposed only to a high vacuum atmosphere where there are relatively few adsorbed gas molecules. Therefore, the amount of gas adsorbed on the piping of the ultra-high vacuum evacuation system becomes very small, so that the subsequent load on the sublimation pump is reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing an example of the evacuation system according to the present invention. In the figure, a vacuum evacuation system A, an intermediate evacuation system B, and an ultra-high evacuation system C are connected to a vacuum vessel 1 in which an ultra-high vacuum is created. An oil rotary pump 13 is attached to the roughing exhaust system A as a main pump, and is connected to the vacuum vessel 1 via a valve 10. The intermediate exhaust system is provided with a liquid nitrogen cold trap 21 and a turbo molecular pump 22 as main pumps, an oil rotary pump 23 as an auxiliary pump, and a vacuum vessel 1 through a valve 20.
Connected to. The ultra-high vacuum evacuation system C is provided with a Ti sublimation pump 31 and a turbo molecular pump 32 as main pumps, and an oil rotary pump 3 as an auxiliary pump.
3 is attached and connected to the vacuum vessel 1 via the valve 30.

In the vacuum exhaust system having such an exhaust system, the vacuum vessel 1 is first evacuated from atmospheric pressure to about 10 Pa by the oil rotary pump 13 by opening the valve 10. Subsequently, the valve 10 is closed and the valve 20 is opened,
The gas is evacuated to about 10 ⁻⁶ Pa by the adsorption action of the liquid nitrogen cold trap 21 and the exhaust action of the turbo molecular pump 22. Subsequently, the valve 20 is closed and the valve 30 is opened, and the sublimation pump 31 is operated simultaneously with the exhaustion by the turbo molecular pump 32. By evacuating in such a process, the ultra-high vacuum evacuation system is only exposed to a high vacuum atmosphere of 10 ⁻⁶ Pa or less, and the sublimation pump 31 almost eliminates the influence of re-release of adsorbed gas molecules from the exhaust pipe. Since it can be used only for adsorption and exhaustion of residual gas molecules in the vacuum vessel 1, an ultra-high vacuum of 10 ^-8 Pa can be achieved quickly. In addition, since the load on the sublimation pump 31 is reduced, the Ti evaporation interval can be extended, and the T
The consumption of i is reduced, and the life up to replacement can be extended. Further, since a liquid nitrogen cold trap or the like is not required in the ultra-high vacuum evacuation system, there is no need to monitor the amount of liquid nitrogen evaporated during ultra-high vacuum evacuation, and the burden on the operator is reduced. In this embodiment, a turbo molecular pump is used as a main pump of the intermediate exhaust system. However, the present invention is not limited to this. For example, an oil diffusion pump may be used. In short, the pump of the intermediate evacuation system only needs to be able to evacuate from the middle vacuum to the high vacuum after receiving the rough evacuation system.

[0011]

As described above, according to the present invention, in addition to the rough exhaust system and the ultra-high vacuum exhaust system, an ultra-high vacuum exhaust system is provided by providing an intermediate exhaust system composed of another piping system. The amount of adsorbed gas to the system piping can be drastically reduced, and the load on the sublimation pump can be reduced, so that ultra-high vacuum can be reached in a short time, and the consumption of the sublimation pump evaporation source such as Ti is reduced. The life until replacement can be extended. In addition, since the liquid nitrogen cold trap is not provided in the ultra-high vacuum evacuation system, it is not necessary to monitor the evaporation amount of liquid nitrogen even during ultra-high vacuum evacuation, and the burden on the operator is reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ultra-high vacuum evacuation system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional ultra-high vacuum evacuation system.

[Explanation of symbols]

 1: vacuum vessel 10, 20, 30: valve 21: liquid nitrogen cold trap 22, 32: turbo molecular pump 31: Ti sublimation pump 13, 23, 33: oil rotary pump

Claims (1)

(57) [Claims] 1. A vacuum evacuation system comprising an ultrahigh vacuum evacuation system using a sublimation pump and a turbo molecular pump as a main pump, and a rough evacuation system using a pump capable of evacuating from atmospheric pressure as a main pump. An intermediate exhaust system having an exhaust performance with a higher degree of ultimate vacuum than the rough exhaust system is provided, and means for switching to an ultra-high vacuum exhaust system after performing exhaust by the intermediate exhaust system following the rough exhaust system is provided. Vacuum evacuation system.