JPH0718410B2 - Cryopump - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cryopump having an improved pumping speed for hydrogen gas, helium gas, and neon gas.

(Problems to be Solved by the Prior Art and the Present Invention) A cryopump is a pump that exhausts gas by condensing or adsorbing gas on a cryogenic surface, but the mechanism of exhausting depends on the vapor pressure of the gas to be exhausted. Since it is different, it is necessary to provide several cryogenic exhaust surfaces with different temperatures and surface materials to exhaust any gas. Especially hydrogen,
Since three kinds of gases such as helium and neon (hereinafter referred to as hydrogen) have a relatively high vapor pressure, the surface of an adsorbent such as activated carbon cooled to an extremely low temperature is usually used as an exhaust surface.

However, since the exhaust capacity for these gases decreases significantly as the surface temperature of the adsorbent increases, in order to prevent the exposure of radiant heat from the outside of the cryopump, the surface of the adsorbent is covered with another cryogenic surface. It is necessary to provide. Further, when a large amount of gas other than hydrogen or the like is condensed on the surface of the adsorbent, the exhaust capacity of the adsorbent with respect to the hydrogen or the like is impaired. It is necessary to cover the adsorbent surface with another cryogenic surface for protection.

For this reason, in the conventional cryopump, it was usual to arrange the activated carbon surface inside the other cryopanel as much as possible as shown in FIG.

FIG. 2 shows the structure of a conventional cryopump.

The first stage 2a of the refrigerator 2 hermetically attached to the pump container 1 has a radiation shield 4 cooled to a low temperature of about 80K.
Is attached. Then, the louver 3 is attached to the opening 7 of the radiation shield 4 as necessary,
It is cooled to a low temperature of about 80K.

Further, the second stage 2b of the refrigerator 2 is provided with a pair of cryopanels, a condensing panel 5 and an activated carbon panel 6, which are cooled to about 15K. Activated carbon 6a is attached to the inside of the activated carbon panel 6 with an adhesive having good thermal conductivity, and gas such as hydrogen is condensed on the activated carbon 6a and exhausted.

According to this configuration, the radiant heat from the room temperature wall that enters the pump container 1 through the opening 7 is louver 3 and the condensing panel 5.
Since it is blocked by the activated carbon 6a, the temperature of the surface of the activated carbon 6a can be prevented from rising without reaching the activated carbon 6a. Moreover, since gases other than hydrogen and the like collide with the outside of the condensation panel 5 or the activated carbon panel 6 at least once before they reach the activated carbon 6a and are condensed, they do not reach the activated carbon 6a, and therefore the activated carbon is It doesn't get stuck.

However, since the activated carbon surface is arranged inside the condensation panel 5 and the activated carbon panel 6 as described above,
In order for gases such as hydrogen to reach the surface of activated carbon and be exhausted,
The gas passage 9 must be passed through and the cryopanel opening 8 that is narrower must be passed through. Therefore, there is a drawback that the exhaust speed for these gases is small.

Therefore, the cryopump shown in FIG. 3 has been put into practical use as a means for improving the exhaust rate for gases such as hydrogen, which is the above-mentioned drawback.

The cryopump includes an activated carbon panel 6 and a pump container 1
It is installed radially toward the lower end of the, and the path for the gas such as hydrogen to reach the activated carbon 6a is relatively short, and although the exhaust speed has been improved, gases other than hydrogen and the like are activated carbon 6a. It has a high possibility of reaching the target, and in particular, when used for sputtering, there is a drawback that a large amount of Ar clogs the activated carbon and loses its ability to exhaust gas such as hydrogen. That is, a gas such as Ar which is not condensed and exhausted at a temperature of 80K collides with the radiation shield 4 and is then re-emitted to easily reach the activated carbon 6a.

(Object of the Invention) The present invention aims to provide a cryopump that prevents clogging due to a gas other than hydrogen and that has an improved pumping speed for the gas such as hydrogen. Means for Means) In order to achieve the above object, the present invention provides a radiation shield which is cooled to a predetermined cryogenic temperature by a refrigerator provided in a pump container having an opening, and a radiation shield provided in the opening. Inside a space surrounded by the louver, a condensation panel cooled by the refrigerator to a temperature lower than the temperature of the radiation shield and an activated carbon panel connected to the condensation panel are provided, and
Gas that condenses at temperatures above K is condensed and attached to the condensation panel, and gases such as hydrogen that do not condense at temperatures above approximately 15K are adsorbed on the activated carbon on the surface of the activated carbon panel and exhausted. In a manner along the inner surface of the, and in a manner to open toward the pump opening having a louver, the condensing panel is arranged, and is connected to the condensing panel, the activated carbon panel is provided, the pump opening and Arranging activated carbon on the activated carbon panel in a position that is not directly visible from the louver and the radiation shield, and
A gap is provided between the condensation panel and the activated carbon panel,
Each of the gas enters through the louver from the pump opening so as to enter at least once into the condensation panel or the surface of the activated carbon panel on which the activated carbon is not arranged, or both before reaching the activated carbon. It composes the panel.

(Function) With the above-mentioned configuration, the activated carbon surface is located in a position that is not visible from the direct radiation shield or any part of the pump opening. Always, in a condensing panel or an activated carbon panel, it collides with a surface on which activated carbon is not attached and is condensed and exhausted. In addition, the activated carbon is not exposed to the radiant heat from the room temperature or the radiant heat from the radiant shield or louver of about 80K.

Further, since the gap that communicates with the activated carbon is provided facing the opening of the pump, it is possible to increase the exhaust speed for the gas such as hydrogen.

(Embodiment) FIG. 1 shows an embodiment of the present invention. In addition,
The same components as those described in the related art are designated by the same reference numerals, and detailed description thereof will be omitted.

A radiation shield 4 that is cooled to a low temperature of about 80K is attached to the first freezing stage 2a of the refrigerator 2 that is airtightly attached to the pump container 1. And further radiation shield 4
A louver 3 is attached to the side facing the pump opening 7 as required and is cooled to a low temperature of about 80K.
On the second freezing stage 2b of the refrigerator 2, a condensing panel 5 cooled to about 15K is attached. The condensation panel 5 is arranged close to the radiation shield 4 along the inside of the radiation shield 4 and surrounds the activated carbon panel 6 which is also attached to the second freezing stage 2b.
Activated carbon 6a is attached to the activated carbon panel 6 with an adhesive having good heat conduction, and contributes to exhaust of gases such as hydrogen, helium, and neon.

Between the condensing panel 5 and the activated carbon panel 6, an activated carbon panel opening 8 is secured toward the pump opening 7,
It serves as a passage for the gas such as hydrogen to reach the activated carbon 6a. The activated carbon 6a is not attached to the entire surface of the activated carbon panel 6, and when any portion of the activated carbon surface is seen from the upper end of the pump opening 7, the louver 3, and the radiation shield 4 into the pump container 1, the activated carbon panel is shown. The part hidden by 6 and not visible, that is, the upper end of the condensation panel 5 and the activated carbon panel 6
Activated carbon panel 6 above the dashed lines 10 and 11 connecting the ends of
And is attached to the inside surrounded by the condensation panel 5. Further, from the side surface and the lower end portion of the radiation shield 4, it is blocked by the condensing panel 5 and neither of the activated carbon surfaces can be seen.

According to such a structure, the activated carbon surface is not directly visible from the radiation shield 4, the louver 3, and the pump opening 7 against the clogging of the activated carbon, which has been a problem in the past. The gas must be activated carbon in the condensation panel 5 or activated carbon panel 6 before it reaches the activated carbon surface.
These gases do not reach the activated carbon surface because they collide with the portion where 6a is not attached and are exhausted by solidification, so that clogging of the activated carbon can be prevented. Further, since the activated carbon panel opening 8 for the gas such as hydrogen to reach the activated carbon surface is arranged facing the pump opening 7, the conductance with respect to the gas such as hydrogen is large, and therefore the exhaust speed is improved. Is possible.

(Effects of the Invention) According to the present invention, a gas other than hydrogen or the like is condensed and exhausted by an activated carbon panel at a stage before reaching the activated carbon surface, thereby preventing clogging of the activated carbon and a cryopump for the gas such as hydrogen. The exhaust speed can be improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a cryopump showing an embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams of a conventional cryopump. 1 ... Pump container, 2 ... Refrigerator, 2a ... 1st freezing stage, 2b ... 2nd freezing stage, 3 ... Louver, 4 ...
… Radiation shield, 5 …… Condensing panel, 6 …… Activated carbon panel, 7 …… Opening, 10,11 …… Looking line.

Claims (1)

[Claims] 1. A radiation shield, which is cooled to a predetermined cryogenic temperature by a refrigerator provided in a pump container having an opening, and a louver provided at the opening, the radiation is provided inside the space. A condensing panel cooled by the refrigerator to a temperature lower than the temperature of the shield and an activated carbon panel connected to the condensing panel are provided, and a gas condensing at a temperature of about 15 K or more is condensed and adhered to the condensing panel to a temperature of about 15 K or more. In a cryopump in which a gas such as hydrogen that does not condense is adsorbed by the activated carbon on the surface of the activated carbon panel and exhausted, a mode is formed along the inner surface of the radiation shield and opened toward a pump opening having a louver. , Arranging the condensing panel and connecting to the condensing panel,
The activated carbon panel is provided, the activated carbon is disposed on the activated carbon panel in a position that is not directly visible from the pump opening, the louver and the radiation shield, and a gap is provided between the condensation panel and the activated carbon panel. Gas entering through the louver through the pump opening impinges on the surface of the condensation panel or the surface of the activated carbon panel where the activated carbon is not placed, or both at least once before reaching the activated carbon. A cryopump characterized in that each panel is configured as described above.