JPH0735041A - Cryopump - Google Patents

Abstract

(57) [Summary] [Purpose] To extend the cycle of the cryopanel regeneration process of the cryopump. [Structure] Cold head 13 and a disk-shaped cold head that contacts the peripheral wall of cold head 13 at its central hole
In a cryopump having a cryopanel 14 cooled by 13, the cryopanel 14 is divided into two panels 14A and 14B that are in contact with the cold head 13 and do not contact each other, and one of them is heated. The heating means 17 is provided or the two panels 14A and 14B are provided with a difference in heat conduction with the cold head 13. When the pump is operating, there is a difference in surface temperature between the two panels 14A and 14B. If the density of gas molecules reaching the surface is not uniform within the surface of the cryopanel 14, the surface temperature of the region of the cryopanel 14 where the gas molecules are relatively dense is made relatively high to make the accumulation of gas molecules uniform. Turn into.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cryopump. The cryopump is a vacuum pump that obtains a high vacuum by adsorbing gas molecules to a panel cooled to an extremely low temperature. Since it has a high pumping speed and is oil-free, it has been widely used in semiconductor wafer processing equipment in recent years. It became so. This vacuum pump stores the gas molecules adsorbed on the panel.When the gas molecules become saturated, the exhaust capacity decreases, so the panel temperature is raised after a certain period of use (by stopping cooling or by forced heating). ), The adsorbed gas molecules must be released from the panel and discharged outside the vacuum pump. This is called a regenerating process, and the vacuum device that uses the vacuum pump must stop operating while this regenerating process is being performed, which results in loss time, so the frequency of the regenerating process is low (long cycle). Is desired.

[0002]

2. Description of the Related Art An example of the structure of a conventional cryopump will be described with reference to FIG. 2A and 2B are explanatory views of a conventional example. FIG. 2A shows a cross section in a state where the vacuum chamber is mounted sideways, and FIG. 2B shows the directions A and A in FIG. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals. 1 is a vacuum chamber, 11 is a pump case, 12 is a refrigerator, 13 is a cold head, 15 is a shield panel, 16 is a front cryopanel, and 24 is a cryopanel.

The cryopanel 24 has a disk shape, and a plurality of cryopanels are fixed to the peripheral wall of the cold head 13 at their central holes in parallel at substantially equal intervals. The front cryopanel 16 is fixed to the shield panel 15, and the shield panel 15 is fixed to the cold head 13. When high-pressure helium gas cooled by the refrigerator 12 is supplied to the cold head 13, the cold head 13 expands and the cold head 13 is cooled to an extremely low temperature, and the cryopanel 24 and the shield panel 15, which are in contact with the cold head 13,
The front-stage cryopanel 16 in contact with the shield panel 15 is cooled.

The surface temperature of the front cryopanel 16 is 40 to 50.
It becomes K and mainly adsorbs H ₂ O, and the surface temperature of the cryopanel 24 becomes 10 to 20 K and adsorbs Ar, O ₂ , N _{2 and the} like.

[0005]

However, in such a cryopump, if the flow of gas molecules flowing into the pump is uneven (the density of gas molecules is not uniform in the plane of the cryopanel), the cryopanel will be affected. However, there is a problem that the adsorption of R is not uniform and the regeneration cycle is shortened. For example, when a cryopump is laterally attached to the lower side surface of the vacuum chamber of the sputtering apparatus and the inside of the vacuum chamber is evacuated, the gas molecule flow tends to be dense on the lower side of the pump and coarse on the upper side. The lower side of the cryopanel adsorbs more gas molecules than the upper side and reaches a saturated state earlier. Therefore, the regeneration process must be performed earlier than when the flow of gas molecules is uniform.

The present invention solves such a problem and uniformizes the adsorption of gas molecules to the cryopanel when the flow of gas molecules flowing into the pump is non-uniform, thereby extending the cycle of the regeneration process. The purpose is to provide a possible cryopump.

[0007]

According to the present invention, the object is to provide a cold head and a disk-shaped cryopanel which is in the form of a central hole and contacts the peripheral wall of the cold head and is cooled by the cold head. In the cryopump having, the disc-shaped cryopanel is divided into two panels that are in contact with the cold head and do not contact each other, and one of the divided two panels of the cryopanel. A heating means for heating the same or providing a difference in heat conduction with the cold head between the two panels to cause a difference in surface temperature during pump operation between the two divided panels. This is achieved by using a cryopump characterized by.

[0008]

The cryopump of the present invention has a structure in which a circular cryopanel is divided into two semicircular panels, and the cryopanel surface temperature during pump operation can be made different. Generally, the lower the surface temperature of the cryopanel, the higher the capture rate of gas molecules. Therefore, when the inflowing gas molecule density is non-uniform, the surface temperature of the portion of the cryopanel where the gas molecule density is relatively high is set higher than that of the rough portion in the temperature range for adsorbing gas molecules. In this case, the accumulation of gas molecules on the cryopanel is made uniform, and the cycle of the regeneration process is extended.

Further, when the gas molecules are nonuniformly accumulated in the surface of the cryopanel, if the gas molecules are desorbed by heating only the heavily accumulated part, the gas molecules are re-adsorbed to the non-heated part. In the first embodiment of the present invention, since the heating means for individually partially heating a large number of cryopanels is provided, the cryopanels are sequentially subjected to the above-described partial heating one by one for a short time. As a result, the accumulation of gas molecules in the cryopanel is made uniform and the cycle of the regeneration process is extended, without significantly lowering the degree of vacuum.

[0010]

Embodiment An embodiment of a cryopump according to the present invention is shown in FIG.
Will be described with reference to. In this embodiment, the vacuum device is a sputtering device, and since the pump is laterally mounted on the lower side surface of the vacuum chamber, the flow of gas molecules is dense on the lower side of the pump and coarse on the upper side.

FIG. 1 is an explanatory view of a first embodiment of the present invention. FIG. 1 (A) shows a cross section of a vacuum chamber of a vacuum apparatus mounted sideways, and FIG. 1 (B) is a sectional view of (A). The A / A direction is shown. 1 is a vacuum chamber exhausted by this pump, 11 is a pump case, 12 is a refrigerator, 13 is a cold head, 14 is a cryopanel, 15 is a shield panel, 16 is a pre-stage cryopanel, and 17 is a heating means.

The cryopanel 14 is disk-shaped, and a plurality of cryopanels are fixed to the peripheral wall of the cold head 13 at their central holes in parallel at substantially equal intervals. Each cryopanel 14 is divided into an upper part and a lower part. Panel 14A and panel 14B
(All are semi-circular). The two do not come into contact with each other and are individually fixed to the cold head 13. Of these, the lower panel 14B is provided with a heating means 17 composed of a heating wire along the outer periphery thereof. The other parts are the same as those of the conventional cryopump described above, and therefore the description thereof is omitted.

During the operation of this pump, a weak electric current is applied to all the heating means 17 so that the surface temperature of all the panels 14B is about 20.
By setting the temperature to K and maintaining the panel 14A at about 10K, the cycle of the regeneration process could be extended. Also, during operation of the pump, the panels 14B are sequentially and intermittently 100K each.
It was also possible to extend the cycle of the regeneration treatment by heating for a short time.

Next, a second embodiment of the present invention will be described.
In this example, as in the first embodiment, the cryopanel 14 is vertically divided into a semicircular panel 14A and a semicircular panel 14B, but there is no heating means 17 and instead the panel is used.
There is a difference in heat conduction between the cold head 13 and the panel 14A and the panel 14B. That is, the thickness of panel 14B is
The heat conduction of panel 14B can be reduced by making it thinner than A, making the contact length of panel 14B with cold head 13 shorter than panel 14A, and making the material of panel 14B lower in thermal conductivity than panel 14A. It is set smaller than 14A.

During operation of this pump, the surface temperature of all the panels 14B became slightly higher than that of the panel 14A, and the cycle of the regeneration treatment could be extended. The present invention is not limited to the above embodiments, and can be implemented with various modifications. For example, the present invention is effective even if the cryopanel 14 is not divided into two equal parts, the heating means 17 is other than the heating wire, and the mounting position is other than the peripheral portion of the panel 14B.

[0016]

As described above, according to the present invention,
When the flow of gas molecules flowing into the pump is non-uniform, it is possible to provide a cryo pump capable of extending the cycle of regeneration treatment by making the adsorption of gas molecules to the cryo panel uniform and using the pump. This contributes to improving the operating rate of the vacuum device.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 1 Vacuum chamber 11 Pump case 12 Refrigerator 13 Cold head 14, 24 Cryo panel 14A, 14B Panel 15 Shield panel 16 Previous cryo panel 17 Heating means

Claims (3)

[Claims] 1. A cold head (13) and a cryopanel (14) which is disk-shaped and contacts the peripheral wall of the cold head (13) at its central hole and is cooled by the cold head (13).
In the cryopump having, the disc-shaped cryopanel (14) is divided into two panels (14A, 14B) that are in contact with the cold head (13) and do not contact each other. A cryopump characterized in that there is a difference in surface temperature during pump operation between the two divided panels (14A, 14B). 2. The cryopump according to claim 1, further comprising heating means (17) for heating one of the two divided panels (14A, 14B) of the cryopanel (14). . 3. The cold head (13) is provided between two divided panels (14A, 14B) of the cryopanel (14).
The cryopump according to claim 1, wherein there is a difference in heat conduction from the cryopump.