JP2803039B2 - Multi-stage cryopump and method for regenerating adsorption surface of multi-stage cryopump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-stage cryopump and a method for regenerating an adsorption surface of the multi-stage cryopump.

[0002]

2. Description of the Related Art When manufacturing an LSI or a super LSI, etc.,
A multi-stage cryopump is used as a vacuum pump used to form an oilless clean vacuum. The cryopump is connected to a vacuum vessel and adsorbs and condenses the gas in the vacuum vessel on a cryogenic surface to create a vacuum.

As shown in FIG. 3, a cryopump with a refrigerator has a helium compressor 2 and a cryogenic refrigerator connected to the helium compressor 2 via a gas pipe 13, for example, a GM (Gifford McMahon) refrigerator. Consists of one,
A vacuum vessel (not shown) is connected to the refrigerator 1.

In the refrigerator 1, a first cryopanel 5 is attached to a first cooling stage 3, and a second cryopanel 6 is attached to a second cooling stage 4. An adsorbent such as activated carbon is placed on the second cryopanel 6.

The first cryopanel 5 is, for example, about 80
It is cooled to about K and solidifies and captures gas having a relatively high boiling point, such as water vapor or carbon dioxide gas in a vacuum vessel. The second cryopanel 6 is cooled to, for example, about 20 K, and solidifies and captures lower-boiling gas such as nitrogen and argon in the vacuum vessel, while the lowest-boiling gas such as hydrogen, neon, and helium is supplied to the second cryopanel. The adsorbent on the panel 6 is adsorbed. In this manner, the cryopump exhausts various gases in the vacuum vessel to create a high vacuum.

However, the displacement of the cryopump for each gas is different. That is, the adsorbing ability of the adsorbent is lost in a relatively short time, and the exhausting ability for gas such as hydrogen, neon, helium, etc. becomes zero. For this reason, a regenerating operation must be performed to raise the temperature of the adsorbent and discharge the adsorbed gas despite having sufficient exhaust capacity for other gases.

[0007]

Conventionally, the operation of regenerating the adsorbent has been performed by stopping the operation of the refrigerator and stopping the operation of each of the cryopanels 5,6.
Is carried out by raising the temperature of the gas to release the gas that has been solidified and trapped and adsorbed. When the regeneration operation is completed, the operation of the refrigerator is restarted, and each cryopanel 5, 6 is cooled to a predetermined temperature (for example, about 80K and about 20K).

However, the time required to cool each of the cryopanels 5 and 6 once again after the temperature is raised to a predetermined temperature is a loss of the cryopump. To solve this problem, Japanese Patent Publication No. 3-64717 discloses a cryopump in which a heater is attached to a cooling stage or a cryopanel and the cryopanel is heated by the heater during regeneration. Poor reliability due to disconnection and the like.

It is an object of the present invention to provide a multi-stage cryopump capable of reliably and quickly regenerating a suction surface of a cryopanel.

[0010]

According to the present invention, there is provided a multistage cryopump comprising: an expansion chamber for generating a low temperature; a cryopanel cooled by the expansion chamber; and a gas communicating with the expansion chamber during regeneration of the adsorption surface of the cryopanel. And a valve between the expansion chamber and the gas chamber.

Further, in the method for regenerating an adsorption surface of a multistage cryopump according to the present invention, the valve is opened to communicate the expansion chamber and the gas chamber to raise the temperature of the cryopanel to a predetermined temperature, thereby solidifying the cryopanel. Releasing the trapped and adsorbed gas, and closing the valve,
During the above steps, the operation of the cryopump is continued.

[0012]

When the operation of the refrigerator is started, the valve is closed. When the refrigerator enters a steady cooling state, the second cryopanel is cooled to, for example, about 20K, and solidifies and captures gas in the vacuum vessel.

When the exhaust capacity of the second cryopanel is depleted, a valve is opened to communicate the expansion chamber and the gas chamber in order to perform a regeneration operation. As a result, since the volume of the expansion chamber is connected as an invalid space, the cooling efficiency in the expansion chamber decreases,
The temperature of the second cryopanel rises.

When the temperature of the second cryopanel reaches about 40K, the gas solidified and captured and adsorbed on the cryopanel is released. During this regeneration operation, the operation of the refrigerator is continued, and the temperatures of the other expansion chambers and the first cryopanel are kept at a steady cooling temperature.

In this way, when the regeneration of the second cryopanel is completed, the valve is closed. Thereafter, the temperature of the second cryopanel is reduced to a predetermined temperature, for example, about 2
Returning to 0K, the refrigerator enters a steady cooling state.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-stage cryopump according to the present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 is a schematic view of an embodiment of a multi-stage cryopump according to the present invention, and FIG. 2 is a partially enlarged sectional view of the multi-stage cryopump shown in FIG. As shown in these figures, the cryopump includes a helium compressor 2 and a cryogenic refrigerator connected to the helium compressor 2, for example, GM.
(Gifford McMahon) The refrigerator 1 includes a vacuum vessel 20 connected to the refrigerator 1.

The refrigerator 1 has a first cryopanel 5 attached to a first cooling stage 3 and a second cryopanel 6 attached to a second cooling stage 4. An adsorbent 14 such as activated carbon is attached on the second cryopanel 6. Further, a chevron 15 is arranged above the second cryopanel 6.

The first and second cooling stages 3 and 4 and the first and second cryopanels 5 and 6 are surrounded by a vacuum outer cylinder 12. A gate valve 21 is provided between the vacuum outer cylinder 12 and the vacuum container 20. In addition, vacuum outer cylinder 1
2 is a vacuum pump 23 via a pipe 24 and a valve 22
It is connected to.

The first cooling stage 3 of the refrigerator 1 is cooled by helium gas, which has been cooled to a low temperature by the expansion action of helium gas in a first expansion chamber (not shown) that generates a low temperature. Further, as shown in FIG. 2, the helium gas expands in the second expansion chamber 7 that generates a low temperature, becomes low temperature, and cools the second cooling stage 4 of the refrigerator 1. Reference numeral 8 in the figure denotes a displacer for discharging low-temperature helium gas from the expansion chamber.

The second expansion chamber 7 is connected to a gas chamber 11 via a gas pipe 9 provided with a regulating valve 10. Helium gas is stored in the gas chamber 11. Refrigerator 1
When the operation is started, the regulating valve 10 and the valve 22 are closed, and the gate valve 21 is opened at an appropriate time. When the refrigerator 1 enters a steady cooling state, the first cryopanel 5 is cooled to, for example, about 80K,
On the surface (first adsorption surface) of the first cryopanel 5, a gas having a relatively high boiling point, such as water vapor or carbon dioxide gas, in the vacuum vessel 20 is solidified and captured.

The second cryopanel 6 is cooled to, for example, about 20K, and solidifies and traps a gas having a lower boiling point such as nitrogen or argon in the vacuum vessel 20 on the surface of the second cryopanel 6. Further, a gas such as hydrogen, neon, or helium having the lowest boiling point is adsorbed by the adsorbent 14 on the second cryopanel 6. Thus, the cryopump exhausts various gases in the vacuum vessel 20 to create a high vacuum.

The suction surface (second suction surface) of the second cryopanel 6 includes the surface of the second cryopanel 6 itself and the suction surface of the adsorbent 14. Thereafter, when the adsorbing capacity of the adsorbent 14 (the exhaust capacity of the second-stage cryopanel 6) is lost, a regenerating operation is performed. This reproduction operation is performed as follows.

First, the gate valve 21 is closed to shut off the inside of the vacuum outer cylinder 12 from the vacuum vessel 20. Next, the regulating valve 10 is opened. As a result, the gas chamber 11 becomes an ineffective space portion of the second expansion chamber 7, the cooling efficiency decreases, the temperature of the second cooling stage 4 immediately rises, and the temperature of the second cryopanel 6 also rises.

Next, the valve 22 is opened to connect the vacuum outer cylinder 12 to the vacuum pump 23, and the inside of the vacuum outer cylinder 12 is evacuated.
When the temperature of the second cryopanel 6 rises to about 40 K, the gas solidified and captured and adsorbed on the surface of the second cryopanel 6 and the adsorbent is released, and the pipe 24
Is sucked by the vacuum pump 23 through

Thus, the second cryopanel 6
Is played. During the regeneration operation, the operation of the refrigerator 1 is continued, so that the first cryopanel 5 is maintained at a temperature of about 80K.

When the regeneration of the second cryopanel 6 is completed, the regulating valve 10 is closed, and the valve 22 is also closed. Since the first cryopanel 5 is maintained at a temperature of about 80K,
The cryopanel 6 is cooled down to about 20K in a short time, the refrigerator 1 enters a steady cooling state, and the cryopump can be operated.

The value of the temperature rise of the second cryopanel 6 during regeneration is adjusted by the opening of the regulating valve 10 and the volume of the gas chamber 11. The regulating valve 10 of the gas pipe 9 may be arranged inside the vacuum outer cylinder 12 or outside the vacuum outer cylinder 12, and can be manually opened and closed. It can be opened and closed automatically. When it is arranged in the vacuum outer cylinder 12, it is preferable to open and close automatically.

Further, in the above embodiment, the example in which the adsorbent 14 is mounted on the second cryopanel 6 has been described.
It is also applicable to a device that adsorbs only on the surface of the cryopanel 6. In this case, the second cryopanel 6
When the adsorption ability of its own surface is lost, the above-described regeneration operation is performed.

Further, in the above-described embodiment, an example in which the gas chamber 11 is connected to the second expansion chamber 7 has been described. However, the gas chamber may be connected not only to the second expansion chamber 7 but also to the first expansion chamber. it can.

In the above embodiment, a cryopump for performing freezing using a two-stage cryopanel is described. However, the present invention is not limited to this, and a cryopump for performing freezing using three or more stages of cryopanel is also used. be able to. In this case, only the expansion chamber for freezing the last stage cryopanel can be connected to the gas chamber,
A gas chamber may be connected to each of the one or more expansion chambers via a gas pipe and a regulating valve.

When a gas chamber is connected to a plurality of expansion chambers, the cryopanel at each stage can be independently regenerated by opening and closing a control valve connected to each expansion chamber. For example, when it is necessary to regenerate only the adsorption surface of a specific cryopanel, the regulator valves corresponding to the cryopanel and the lower cryopanel are opened to release the gas adsorbed on the adsorption surface. Raise the adsorption surface to the required temperature. During this time, by keeping the operation of the refrigerator, the higher temperature of the cryopanel is maintained at a substantially constant temperature, so that the cryopump enters a steady state for a short time after the regeneration is completed.

As the refrigerator 1, not only the GM refrigerator but also various regenerative multistage refrigerators such as a Solvay cycle refrigerator and a Stirling refrigerator can be used.

[0034]

According to the present invention, the adsorption surface of the cryopump can be regenerated in a short time and reliably.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of a cryopump according to the present invention.

FIG. 2 is a partially enlarged sectional view of the cryopump shown in FIG.

FIG. 3 is a schematic view of a conventional cryopump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Refrigerator 2 Helium compressor 3 1st cooling stage 4 2nd cooling stage 5 1st cryopanel 6 2nd cryopanel 7 2nd expansion chamber 8 displacer 9 Gas piping 10 Adjustment valve (valve) 11 Gas chamber 12 Vacuum Outer cylinder 13 Gas pipe 14 Adsorbent 15 Chevron 20 Vacuum container 21 Gate valve 22 Valve 23 Vacuum pump 24 Pipe

Claims (2)

(57) [Claims] An expansion chamber that generates a low temperature; a cryopanel cooled by the expansion chamber; a gas chamber that communicates with the expansion chamber when a suction surface of the cryopanel is regenerated; the expansion chamber and the gas chamber A multistage cryopump, comprising: A step of opening the valve to communicate the expansion chamber and the gas chamber to raise the temperature of the cryopanel to a predetermined temperature, thereby releasing the gas solidified and trapped and adsorbed on the cryopanel; The method for regenerating an adsorption surface of a multi-stage cryopump according to claim 1, further comprising a closing step, wherein the operation of the cryopump is continued during the step.