JPH10141225A - Regenerating method of cryopump and cryopump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a time for regeneration by directly heating, by an inner heater, an expander for expanding a high pressure refrigerant gas from a compressor part and a pump body enclosing a cryoarray, in a regeneration step. SOLUTION: In a pump acting part 52, primary and secondary cryoarrays are connected to an expander for expanding high pressure helium, and they are enclosed and shut-out from an outer environment by a pump body 56. An inner heater 61 is arranged on the pump body 56 by being brought into contact with a body outer surface. When the pump acting part 52 is regenerated, nitrogen gas heated to about 120 deg.C by a heater 26 is supplied from a purge tube 60 until the cryoarray exceeds a normal temperature. Simultaneously, the pump body 56 is directly heated by the inner heater 61. As a result, a temperature of the pump acting part 52 is raised to the normal temperature at a short time, and regeneration is carried out. Especially, a material which is condensed to the pump body 56 is gasifyed easily and is exhausted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cryopump regeneration method and a cryopump apparatus for realizing the regeneration method. More specifically, when the cryopump is regenerated at regular intervals, a method that can increase the regeneration efficiency,
And a cryopump device having a structure suitable for carrying out the method.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, processes such as low pressure chemical vapor deposition and sputtering require a vacuum environment. The vacuum environment is generally achieved by a method in which gas inside the chamber is exhausted by a pump connected to the process chamber. Vacuum pumps are classified into low vacuum pumps and high vacuum pumps according to the degree of vacuum in the vacuum environment. Diffusion pumps, turbo molecular pumps, cryopumps, and the like using oil can be listed as those used for the high vacuum pump.

The cryopump used for the high vacuum pump does not immediately exhaust gas existing in the process space, but fixes the gas on a cooling surface formed in the pump and collectively after the process is completed. This is a unique form of vacuum pump that employs a method of exhausting air. A cryopump that creates a clean vacuum by a method of collecting gas particles on a cooling surface and exhausting the gas particles collectively includes a compressor section and a pump action section.

Hereinafter, the configuration of a cryopump will be described with reference to FIGS.

[0005] The compressor section 11 has a function similar to that of a refrigerator motor. The compressor section 11 compresses helium used as a refrigerant at a high pressure, and supplies high-pressure, high-purity room temperature helium gas to a pump action section. It serves to supply to the 12 expanders 13. Since a large amount of heat is generated in the compression process, the cooling water removes the heat while flowing inside the compressor section.

[0006] The pump operating section 12 is composed of the compressor section 1.
A cryoarray comprising an expander 13 for expanding the high-pressure helium gas supplied from 1, a baffle 14 cooled by the expander 13, and a cold head 15;
And a pump body 16 that holds a space surrounding these. Further, a temperature monitor 17, a pressure replacement valve 18, and the like are added.

Considering the operation of the cryopump in view of its structure, it can be seen that there are many similarities with the phenomenon that water vapor condenses on the cooling plate of a refrigerator. First, in order for the cryopump to operate, a roughing pump 22 for creating a low vacuum state operates to bring the chamber 21 which is a process space to which the cryopump is connected into a low vacuum state. The reason why the low vacuum state is formed in advance is to increase the efficiency of the cryopump. When a low vacuum state is formed in the chamber 21, the roughing valve 2 connected to the roughing pump 22
3 tightens to close the space and activate the cryopump.

The cryopump first has a compressor section 1
In step 1, helium as a refrigerant is compressed at a high pressure. The heat generated at this time is discharged by the cooling water flowing through the inside of the compressor unit 11. High pressure helium is connected hose 19
Is sent to the expander 13 of the pump action section 12 and expands in the expander 13 to cause a temperature drop due to adiabatic expansion. Such a decrease in temperature causes the baffle 14 that is in contact with the expander, that is, the first stage to be cooled to the 70K level, and the cold head 15 that is the second stage to be cooled to the 10K level, thereby collecting gas molecules existing inside the space. Fix it.

In principle, the function of fixing gas is divided into cryo-condensation in which a gas having a high freezing point is condensed into a solid, and cryosorption in which a gas having a low freezing point is confined in the internal space of a porous material having a large surface area. . In each case, the gas in the space is fixed and removed on the surface of the low-temperature array.

When the cryopump is fully operated, a process is performed in a process chamber. At this time, a process gas or the like may flow into the process chamber from the outside. In this case, if the ratio of fixing the gas generated due to the gas flow into the cryopump or the process reaction is larger than the gas generation rate due to the gas flow into the process space or the reaction, a stable high vacuum state is maintained. can do.

In principle, the cryopump does not directly exhaust the gas inside the space to the outside, but temporarily fixes the gas on the surface of the cryogenic array located in the space. Accordingly, as the process continues, the gas fixed on the surface accumulates, and the efficiency of the pump for removing gas in the process space decreases, as does the cooling efficiency of the frosted refrigerator cooling plate. I do. Therefore, it is necessary to take measures to stop the use of the cryopump every predetermined use period, remove and release the gas fixed to the array, and increase the gas fixing ability of the pump array again. Such measures include regeneration of the cryopump.

The regeneration of the cryopump is an operation of increasing the temperature of the array to exhaust condensed matter fixed on the surface of the array and gas fixed by cryosorption to the outside of the pump. First, the process is stopped in order to regenerate the cryopump. Then, the operation of the compressor section 11 of the cryopump is stopped in a state where the high vacuum valve 24 connecting the process space and the pump action section 12 is shut off. Then, heated dry nitrogen is blown into the pump body 16 to warm the cryoarray and the pump body. Then, the fixed gas or the like moves actively, comes off the array surface, and is exhausted from the pump through the pressure alternation valve 18.

Referring to FIG. 5, nitrogen gas flows into the internal space of the pump through a purge tube 20 for regeneration of the pump action section 12. The nitrogen gas is heated through a separate heater 26 before exiting the nitrogen gas supply 25 and flowing into the pump. Therefore, the temperature of the inflowing nitrogen is about 120 ° C., which is higher than room temperature, and the time required for regeneration can be reduced. During the regeneration phase, the pump temperature is generally raised until the array temperature is at room temperature. Thus, the flow of nitrogen through the heater is continued until the temperature of the array is equal to room temperature.

However, the conventional regeneration process is an indirect heating method in which the temperature rise of the array of pumps and other pump bodies depends only on the nitrogen gas that is heated and flows in, so that a long time is required for the temperature rise. . For this reason, the operation time of a process performed using a vacuum pump had to be shortened. Also, it was difficult to sufficiently exhaust the residual gas in the pump body of the cryopump.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for regenerating a direct heating type cryopump capable of shortening the time required for regeneration as compared with the conventional indirect heating type cryopump. To provide.

Another object of the present invention is to provide a cryopump device having a configuration suitable for carrying out the above-mentioned regeneration method.

[0017]

According to the present invention, there is provided a method for regenerating a cryopump according to the present invention, wherein in the step of regenerating the cryopump, an expander for expanding a high-pressure refrigerant gas supplied from a compressor section is provided. ,
This is performed by directly heating the pump body forming a space surrounding the cryoarray in contact with the expander with an internal heater.

It is desirable that the pump body be heated by uniformly disposing a resistance wire on the pump body and supplying current thereto to generate Joule heat. Further, the heating by the internal heater is preferably performed until the temperature of the pump body reaches room temperature, but it is also possible to perform heating until the temperature becomes higher than that. While the above-described direct heating according to the present invention is performed, it is preferable to perform indirect heating by introducing a high-temperature nitrogen gas in order to shorten the time required for regeneration, but it is preferable to perform regeneration only with direct heating. it can.

Further, the cryopump device according to the present invention includes a compressor section and a pump action section, and
The pump action section expands a high-pressure refrigerant gas supplied from the compressor section, a cryoarray that is cooled by contacting the expander, and forms a space surrounding the expander and the cryoarray. And an internal heater in contact with the pump body.

It is desirable that the cryopump device of the present invention be provided with a temperature monitor for sensing the temperature of the pump operating section. In addition, it is desirable to provide a pressure change valve that can release the internal gas to the outside when the internal pressure increases. Further, it is preferable that the apparatus is provided with a purge tube for regeneration used in the conventional indirect heating system, and is capable of simultaneously performing indirect heating and direct heating during regeneration. Further, the internal heater of the present invention may be one in which an electric resistance wire connected to a power supply is provided on a pump body.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of a specific embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

Referring to FIG. 1, the pump action section 52 includes
An expander 53 that expands high-pressure helium as before,
It includes primary and secondary cryoarrays connected to the expander 53 and cooled, and a pump body 56 that surrounds them while isolating them from the external environment. Further, a pressure change valve 58, a purge tube 60 for regeneration, and a temperature monitor 57 are also provided. The pump body 56 is provided with an internal heater 61 which is a feature of the present invention in contact with the outer surface of the body. The internal heater 61 is connected to an external power supply, and generates Joule heat when the cryopump is regenerated.

When the gas present in the space of the primary and secondary arrays is fixed and accumulated by condensation or the like by the operation of the pump, the pump efficiency for removing the gas from the space also decreases. At this time, playback is started. For regeneration, first, the high vacuum valve connecting the process chamber and the pump is closed, and the operation of the compressor of the cryopump is also stopped. Then, the nitrogen gas supply source 25 is connected to the purge tube 60 for regeneration of the pump action section.

The supplied nitrogen gas is heated to about 120 ° C. via the heater 26 during the supply. The supply of nitrogen gas continues until the cryoarray reaches room temperature. At the same time, the power switch connected to the internal heater 61 is closed to directly heat the pump body 56. Therefore,
The cryopump is heated indirectly and directly by the nitrogen gas and the internal heater 61, and the temperature of the pump action section 52 is raised to room temperature in a short time to perform regeneration. Especially,
The substances condensed in the pump body 56 are also easily vaporized and exhausted. In the regeneration process, the gas fixed to the array or the pump body 56 is purged with the supplied nitrogen gas and exhausted through the pressure altering valve 58.

[0025]

As described above, according to the present invention, the pump body is directly heated to shorten the regeneration time, and the substance fixed to the pump body can be more easily and completely evacuated.

[Brief description of the drawings]

FIG. 1 is a diagram showing how regeneration is performed in a cryopump device according to one embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a vacuum system including a general cryopump.

FIG. 3 is a cross-sectional view schematically showing a configuration of a pump operation section of a conventional cryopump.

FIG. 4 is a cross-sectional view showing in detail a configuration of an expander and a cryo-array among pump operation parts of a conventional cryopump.

FIG. 5 is a diagram showing how regeneration is performed in a conventional cryopump.

[Explanation of symbols]

 11 Compressor part 19 Connecting hose 21 Chamber 22 Roughing pump 23 Roughing valve 24 High vacuum valve 25 Nitrogen gas supply source 26 Heater 52 Pump action part 53 Expander 56 Pump body 57 Temperature monitor 58 Pressure replacement valve 60 Purge tube 61 Internal heater

Claims (8)

[Claims] In the step of regenerating a cryopump, an expander for expanding a high-pressure refrigerant gas supplied from a compressor section, and a pump body forming a space surrounding the cryogenic array in contact with the expander. Is a method of regenerating a cryopump, in which is heated directly by an internal heater. 2. The method according to claim 1, wherein the heating of the pump body is performed by energizing the internal heater formed by uniformly arranging resistance wires on the pump body. 3. The method according to claim 1, wherein the heating is performed until the temperature of the pump body reaches room temperature. 4. The method according to claim 1, wherein at the same time as the heating is performed, indirect heating is performed by flowing hot nitrogen gas into the inside of the pump body through a purge tube for regeneration. 5. An expander comprising a compressor section and a pump action section, wherein the pump action section expands a high-pressure refrigerant gas supplied from the compressor section;
A cryopump device comprising: a cryoarray cooled by contacting the expander; and a pump body forming a space surrounding the expander and the cryoarray, wherein an internal heater in contact with the pump body is further provided. Equipped cryopump device. 6. The pump operating section further includes a temperature monitor for sensing a temperature of the pump operating section, and a pressure change valve for discharging an internal substance to the outside when an internal pressure of the pump operating section increases. The cryopump device according to claim 5, wherein 7. The cryopump device according to claim 5, wherein the pump action unit further includes a purge tube for regeneration for allowing high-temperature nitrogen gas to flow into the inside of the pump body during regeneration of the pump. 8. The cryopump apparatus according to claim 5, wherein the internal heater is configured by installing an electric resistance wire connected to a power supply on a pump body.