JP2007315192A - Cryopump and its regeneration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve regeneration efficiency, by increasing the heat receiving area of solid-state gas during regeneration, in regard to a cryopump and its regeneration method. <P>SOLUTION: This regeneration method of the cryopump comprises a vacuum vessel 4, a cryopanel 10 and a shield 9 arranged in this vacuum vessel 4, a refrigerator 5 condensing introducing gas in the vacuum vessel 4 by cooling the cryopanel 10 and the shield 9, a purge gas supply means for supplying and processing purge gas to and in the vacuum vessel 4, and a roughing vacuum pump 13 sucking the introducing gas in the vacuum vessel 4; and performs pre-rough and purge processing for repeatedly performing supply processing of the purge gas to the vacuum vessel 4 by the purge gas supply means and suction processing of the introducing gas from the inside of the vacuum vessel 4 by the roughing vacuum pump 13, before performing ordinary regeneration processing. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cryopump and a regeneration method thereof, and more particularly to a cryopump capable of improving regeneration efficiency and a regeneration method thereof.

  For example, it is necessary to realize a high vacuum in a semiconductor manufacturing facility, and a cryopump is frequently used as a vacuum pump that can realize this high vacuum. This cryopump requires a refrigerator on the principle of vacuum generation. As a refrigerator used for this cryopump, a Gifford-McMahon cycle type refrigerator (hereinafter referred to as a GM type refrigerator) is known. Then, the GM type refrigerator and the cryopanel and the shield disposed in the vacuum vessel are thermally connected, and the gas (for example, argon gas) in the vacuum vessel is condensed in the cryopanel and the like in the cooling process. High vacuum is achieved by adsorption.

  The cryopump configured as described above needs to be regenerated due to its structure. This regeneration is a process in which heat is applied to a gas condensed to a cryopanel or the like during the cooling process (hereinafter referred to as solid gas), and the temperature is raised to liquefy and vaporize the solid gas and release it outside the vacuum vessel. Say.

At the time of regeneration of the cryopump, the cryopanel and the shield are heated by a heating device such as a heater, and a purge gas such as nitrogen gas is introduced into the vacuum vessel. As a result, the gas condensed and adsorbed on the cryopanel and the shield is liquefied and spontaneously falls and remains in the shield. In this state, when all the liquefied gas (hereinafter referred to as liquefied gas) is vaporized and exhausted, it takes a long time for the liquefied gas to vaporize, and thus the regeneration efficiency decreases. is there. Therefore, as disclosed in Patent Document 1, a cryopump has been proposed in which a hole is formed in the shield and liquid gas flows into the vacuum vessel through this hole.
Japanese Patent Laid-Open No. 05-033766

  In the cryopump with this configuration, the heat of the vacuum vessel, which is the atmospheric temperature, can be used for vaporization of the liquefied gas, and the regeneration efficiency can be improved as compared with the cryopump in which no hole is formed in the shield.

  However, in a configuration in which regeneration is performed using heat from the purge gas and heat from the atmosphere flowing in through the walls of the vacuum vessel, the heat receiving surface from the purge gas of the liquid gas is only the upper surface of the liquid gas, and from the vacuum vessel The heat receiving surface is only the surface where the liquid gas is in contact with the vacuum vessel. For this reason, there is a problem that the heat receiving area from the purge gas and the vacuum vessel is narrow, so that quick regeneration cannot be performed. This becomes a problem particularly in the case of so-called full regeneration in which all the gas condensed on the cryopanel and the shield is removed.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a cryopump that improves the regeneration efficiency by increasing the heat receiving area of the solid gas during regeneration and a regeneration method thereof. .

  In order to solve the above-described problems, the present invention is characterized by the following measures.

The cryopump according to the invention of claim 1 is:
A vacuum vessel;
A cryopanel disposed in the vacuum vessel;
A refrigerator that condenses the gas in the vacuum vessel by cooling the cryopanel;
Purge gas supply means for supplying a purge gas to the vacuum vessel;
A suction means for sucking the gas in the vacuum vessel;
Control means for repeatedly performing the supply process of the purge gas to the vacuum container by the purge gas supply means and the suction process of the gas from the inside of the vacuum container by the suction means during the temperature rise in the regeneration. It is a feature.

The invention according to claim 2
The cryopump according to claim 1,
While providing a temperature sensor in the vacuum vessel,
When the control means determines that the temperature in the vacuum vessel is a temperature at which the gas coexists in a solid-liquid two-phase, based on the output of the temperature sensor, a supply process of a purge gas to the vacuum vessel, and the vacuum vessel The gas suction process from the inside is repeatedly performed.

The invention according to claim 3
The cryopump according to claim 1 or 2,
The time for sucking the gas from the vacuum vessel is set to a time during which the liquefied gas can be boiled under reduced pressure in the vacuum vessel.

The invention according to claim 4
A vacuum vessel, a cryopanel disposed in the vacuum vessel, a refrigerator for condensing the gas in the vacuum vessel by cooling the cryopanel, and a purge gas supply means for supplying a purge gas to the vacuum vessel And a cryopump regeneration method having suction means for suctioning the gas in the vacuum vessel,
During the temperature increase in the regeneration, the purge gas supply process by the purge gas supply means and the gas suction process from the vacuum container by the suction means are repeatedly performed. is there.

The invention according to claim 5
In the regeneration method of the cryopump according to claim 4,
When the temperature of the gas condensed on the cryopanel reaches a temperature in which two phases of solid and liquid coexist, the supply process of the purge gas to the vacuum container and the suction process of the gas from the vacuum container are repeatedly performed. The processing is started.

Further, the invention described in claim 6
In the regeneration method of the cryopump according to claim 4 or 5,
The time for sucking the gas from the vacuum vessel is set to a time during which the liquefied gas can be boiled under reduced pressure in the vacuum vessel.

  According to the present invention, the solid gas condensed in the cryopanel is liquefied in the temperature raising process in the regeneration by overheating due to the reverse operation of the heater or the refrigerator, or by supplying the purge gas to the vacuum vessel by the purge gas supply means. The liquid gas falls from the cryopanel and accumulates at the bottom of the vacuum vessel or shield.

  In this state, when the gas is sucked from the vacuum vessel by the suction means, the inside of the vacuum vessel becomes equal to or lower than the saturated vapor pressure, and the liquid gas boils (reduced pressure boiling). The gas generated by boiling the liquid gas is discharged to the outside of the vacuum container along with the suction process.

  In addition, the droplets scattered due to the intensity of boiling are condensed immediately into a solid gas because the pressure at the point of jump (the gap between the vacuum vessel and the shield, each part of the vacuum vessel, etc.) is low. This solid gas is in a condensed state in various parts of the cryopanel, shield, and vacuum vessel. Further, since the temperature of the gap between the vacuum vessel and the shield is quite high (near the atmospheric temperature), a part of the solid gas is sublimated (vaporized) and is discharged outside the vacuum vessel by the suction means.

  Thereafter, when the purge gas is supplied from the purge gas supply means to the vacuum vessel, the solid gas is liquefied again, part of which is vaporized and discharged from the vacuum vessel, and the rest falls to the bottom of the vacuum vessel or shield. It collects in. At this time, since the solid gas is condensed in a widely dispersed state in the cryopanel, the shield, and the vacuum vessel, the heat receiving area from the purge gas and the heat receiving area with the vacuum vessel are simply set on the cryopanel. It is wider than the state accumulated at the bottom. Therefore, the melted solid gas can be efficiently received from the purge gas and the vacuum vessel (the shield when the temperature of the shield is raised), and the vaporization of the melted solid gas can be promoted.

  Therefore, it is possible to shorten the temperature rise time by repeatedly performing the purge gas supply process to the vacuum container and the gas suction process from the inside of the vacuum container during the temperature rise in the regeneration as described above. Become.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a cryopump 1 according to an embodiment of the present invention. The cryopump 1 is attached to a processing chamber (not shown) (for example, a processing chamber of a semiconductor manufacturing apparatus) and evacuates the processing chamber.

  The cryopump 1 generally includes a compressor 3, a vacuum vessel 4, a refrigerator 5, a shield 9, a cryopanel 10, various valves 25 and 26, a controller 30, and the like. Further, the regeneration process of the cryopump 1 in the present embodiment is performed by raising the temperature of the shield 9 and the cryopanel 10 by reversing the cooling cycle of the refrigerator 5 (so-called reverse temperature rise), and by purging the purge gas (at atmospheric temperature) For example, nitrogen gas) is introduced into the vacuum container 4.

  The compressor 3 has a function of increasing the pressure of the refrigerant gas such as helium gas and sending it to the refrigerator 5 and collecting the refrigerant gas adiabatically expanded by the refrigerator 5 and increasing the pressure again. The vacuum vessel 4 is attached to the processing chamber described above, and the cylinders 14 and 15 of the refrigerator 5, the shield 9, the cryopanel 10, and the like are disposed therein.

  A roughing pipe 13A, a purge pipe 17 and a pressure sensor 28 are connected to the vacuum vessel 4. The roughing pipe 13A is connected to a roughing pump 13 (vacuum pump), and roughs the gas in the vacuum vessel 4 at the start of vacuum processing. The roughing pipe 13A is provided with a rough valve 26. When the rough valve 26 is turned off (closed), roughing is stopped, and when it is turned on (opened), roughing is performed. The rough valve 26 is configured such that ON / OFF control is performed by the controller 30.

  The purge pipe 17 is connected to a nitrogen gas supply means (not shown), and supplies a purge gas (nitrogen gas) at an atmospheric temperature into the vacuum vessel 4 during regeneration, which will be described later. The purge pipe 17 is provided with a purge valve 25. The purge of the nitrogen gas is stopped when the purge valve 25 is turned off (closed), and the purge of the nitrogen gas is performed when the purge valve 17 is turned on (opened). Is called. The purge valve 25 is configured such that ON / OFF control is performed by the controller 30.

  The pressure sensor 28 is configured to detect the pressure in the vacuum vessel 4. The pressure sensor 28 is connected to a controller 30, and the controller 30 is configured to recognize the pressure in the vacuum vessel 4 through the pressure sensor 28.

  Note that a gate valve (not shown) is disposed between the vacuum vessel 4 and the processing chamber, and the vacuum vessel 4 is airtightly isolated from the processing chamber by closing the gate valve.

  The refrigerator 5 is a GM refrigerator, and includes a first stage cylinder 14, a second stage cylinder 15, a reversible motor 16, and the like. A first stage displacer 14A is disposed inside the first stage cylinder 14 so as to be capable of reciprocating in the left-right direction in the figure, and a second stage displacer 15A is arranged in the left-right direction in the figure. It is arrange | positioned so that reciprocation is possible. The first stage displacer 14A and the second stage displacer 15A are connected and reciprocate in the cylinders 14 and 15 as described above using the reversible motor 16 as a drive source.

  A first stage expansion chamber is formed between the first stage cylinder 14 and the first stage displacer 14A, and a second stage expansion chamber is formed between the second stage cylinder 15 and the second stage displacer 15A. It is formed. The first and second stage expansion chambers are configured such that their volumes change as the displacers 14A and 15A reciprocate.

  The reversible motor 16 is a motor capable of forward rotation and reverse rotation. The reversible motor 16 is connected to a controller 30 and performs forward rotation during vacuum processing and reverse rotation during reproduction according to instructions from the controller 30.

  A first stage refrigeration stage 7 is disposed on the outer periphery of the first stage cylinder 14. The first stage refrigeration stage 7 is provided with a shield 9 (thermally connected). The shield 9 functions to prevent external radiant heat from conducting heat to the cryopanel 10.

  The shield 9 is provided with a louver 12 and an outflow hole 29. The louver 12 is disposed on the upper part of the shield 9 having a cup shape (bottomed shape). The louver 12 is disposed in the vicinity of the upper opening of the vacuum vessel 4. The outflow hole 29 is formed on the bottom surface of the shield 9 having a cup shape (bottomed shape).

  On the other hand, a second-stage refrigeration stage 8 is disposed on the outer periphery of the second-stage cylinder 15. The second stage refrigeration stage 8 is provided with a cryopanel 10. The cryopanel 10 is provided with activated carbon 11 on its inner peripheral surface.

  Further, the first stage cylinder 14 is provided with a first stage temperature sensor 18, and the second stage cylinder 15 is provided with a second stage temperature sensor 19. The first stage temperature sensor 18 detects the temperature of the first stage cylinder 14 (this temperature is substantially the same as the temperature of the shield 9), and the second stage temperature sensor 19 is the second stage temperature sensor 15. The temperature (this temperature is substantially the same as the temperature of the cryopanel 10) is detected. The first stage temperature sensor 18 and the second stage temperature sensor 19 are connected to a controller 30.

  A configuration in which the first stage temperature sensor 18 is directly disposed on the shield 9 and a structure in which the second stage temperature sensor 19 is disposed directly on the cryopanel 10 are also conceivable, but more gas in the processing chamber is used. In the present embodiment, the temperature sensors 18 and 19 are disposed on the refrigeration stages 7 and 8 in terms of condensation and adsorption to increase the degree of vacuum. It is set as the structure which judges.

  FIG. 2 is a diagram illustrating a hardware configuration of the controller 30. The controller 30 is constituted by a microcomputer, and as shown in the figure, a CPU 21, a ROM 22, a RAM 23, and an interface device 24 are connected by a bus line 25. Various sensors 18, 19, 28 and valves 25, 26 are connected to the CPU 21 via the interface device 24.

When vacuum processing is performed in the cryopump 1 configured as described above, the purge valve 25 is first turned off (closed) and the rough valve 26 is turned on (opened), and the roughing pump 13 is driven to operate the processing chamber and the vacuum. The gas in the container 4 is roughly evacuated (for example, pressure reduction is performed to about 10 ⁻² Torr). When this roughing process is completed, the roughing pump 13 is stopped and the reversible motor 16 is rotated in the forward direction.

  When the reversible motor 16 rotates in the forward direction, the refrigerator 5 enters the cooling mode, and the refrigerant gas supplied from the compressor 3 to the first stage expansion chamber and the second stage expansion chamber moves to the displacers 14A and 15A. Accompanying this, adiabatic expansion occurs, generating cold. Thereby, the 1st stage freezing stage 7 is cooled to 30-100K (shield 9 is 100K or less), for example, and the 2nd stage freezing stage 8 is cooled to 4-20K (cryo panel 10 is 20K or less), for example.

  When various gases in the processing chamber enter the cryopump 1 in this state, carbon dioxide is mainly condensed by the louver 12 and the shield 9, and argon and nitrogen are mainly condensed by the cryopanel 10, and further, hydrogen, neon, Helium or the like is mainly adsorbed on the activated carbon 11. As a result, the processing chamber is evacuated to achieve a high vacuum.

  In the following description, various gases (carbon dioxide, argon, nitrogen, hydrogen, neon, helium, etc.) condensed by the cryopump 1 are collectively referred to as introduced gas. The introduced gas condensed or adsorbed on the shield 9 and the cryopanel 10 is referred to as a solid gas 21.

  Incidentally, the introduced gas exhausted from the processing chamber as described above is condensed or adsorbed on the shield 9, the cryopanel 10, the activated carbon 11, and the like. FIG. 5 shows a state where the solid gas 21 is condensed on the shield 9 and the cryopanel 10. When the amount of the solid gas 21 condensed in the shield 9 and the cryopanel 10 increases, the exhaust performance of the cryopump 1 is lowered. For this reason, as described above, it is necessary to regenerate the solid gas 21 condensed in the cryopump 1 from the vacuum vessel 4.

  Next, a regeneration method in the cryopump 20 which is an embodiment of the present invention will be described.

  In normal regeneration processing, purge gas is introduced into the vacuum vessel 4 and the shield 9 is heated by a heating means (in this embodiment, the refrigerating machine 5 in which the reversible motor 16 is rotated in the reverse direction) such as reverse operation of a heater or a refrigerating machine. Then, the regeneration process is performed by raising the temperature of the cryopanel 10 (hereinafter referred to as a normal regeneration process). On the other hand, in the regeneration method according to the present embodiment, a process of supplying a purge gas to the vacuum vessel 4 during the temperature rise in the regeneration (purge process) and a process of sucking the introduced gas from the vacuum vessel 4 by the roughing pump 13 ( The roughing step) is repeatedly performed. The process of repeatedly performing the purge process and the roughing process is referred to as a pre-rough & purge process in the following description.

  FIG. 3 is a flowchart showing the pre-rough & purge process performed by the controller 30, and FIG. 4 is a state transition diagram of the cryopump 1 when the pre-rough & purge process is executed. Hereinafter, the pre-rough & purge process performed by the controller 30 will be described with reference to the state transition diagram shown in FIG. 4 and the diagrams showing the state of the cryopump 1 shown in FIGS.

  The reproduction processing program shown in FIG. 3 is stored in the RAM 23 shown in FIG. Also, the state transition diagram shown in FIG. 4 shows a temperature indicated by T1 (thick solid line) in the present embodiment, which is the temperature detected by the first stage temperature sensor 18 in this embodiment, and is indicated by T2 (thick one-dot chain line). Is the temperature detected by the second stage temperature sensor 19 in this embodiment.

  In FIG. 4, Tc1 (thin alternate long and short dash line) indicates the temperature detected by the second-stage temperature sensor in the comparative example of the present embodiment, and Tc2 (thin alternate long and short dash line) indicates the first in the comparative example. This is the temperature detected by the two-stage temperature sensor.

  FIG. 4 also shows the pressure in the vacuum vessel 4 detected by the pressure sensor 28. Further, in the comparative example shown in FIG. 4, the supply process of the purge gas to the vacuum vessel 4 and the suction process of the introduced gas from the vacuum vessel 4 are repeatedly performed during the temperature rise in the regeneration as in this embodiment. This is a playback process that does not.

  The regeneration process shown in FIG. 4 is started by an instruction from a main computer of a semiconductor manufacturing apparatus having a processing chamber or by an operator's manual operation. The state of the cryopump 1 at which this regeneration process is started is a state in which the solid gas 21 is condensed on the shield 9 and the cryopanel 10 as shown in FIG.

  When the regeneration process shown in FIG. 4 is started, first, the gate valve is closed and the vacuum vessel 4 and the processing chamber are hermetically isolated. Subsequently, in step 10 (step is abbreviated as S in the figure), the controller 30 turns on (opens) the purge valve 25 and turns off (closes) the rough valve 26. Thereby, a purge gas (nitrogen gas) having an atmospheric temperature is introduced into the vacuum vessel 4. Further, the controller 30 controls the reversible motor 16 to rotate in the reverse direction, whereby the refrigerator 5 enters a regeneration mode and the shield 9 and the cryopanel 10 are heated (hereinafter referred to as reverse temperature rising). At the same time, temperature detection of the second stage refrigeration stage 8 is started using the second stage temperature sensor 19.

In subsequent step 12, the controller 30 determines whether the temperature T2 detected by the second stage temperature sensor 19 has reached the first predetermined temperature Temp1. Here, the first predetermined temperature Temp1 is the temperature of the cryopanel 10 where the introduced gas exists in a solid-liquid two-phase at atmospheric pressure. Further, since the cryopanel 10 is disposed in the second stage refrigeration stage 8 of the second stage cylinder 15, the first predetermined temperature Temp 1 is substantially equal to the second stage refrigeration stage 8. A specific value of the first predetermined temperature Temp1 is about 84K when the introduced gas is argon (Ar), and about 63K when the introduced gas is nitrogen (N ₂ ).

  The controller 30 waits until the temperature T2 of the second stage refrigeration stage 8 reaches the predetermined temperature Temp1 by the process of step 12, and advances the process to step 14 when the temperature T2 of the second stage refrigeration stage 8 reaches the predetermined temperature Temp1. In this step 12, the time to wait until the temperature T2 of the second stage refrigeration stage 8 reaches the predetermined temperature Temp1 corresponds to the time from time 0 to time t1 in FIG. Further, during this time, the temperature rises with the introduced gas condensed in the cryopanel 10. When the temperature T2 of the second stage refrigeration stage 8 reaches the predetermined temperature Temp1, the pre-rough & purge process is started under certain conditions as will be described later.

  In step 14, the controller 30 determines whether the temperature T2 detected by the second stage temperature sensor 19 has reached the second predetermined temperature Temp2. Here, the second predetermined temperature Temp2 is a temperature at which the internal pressure of the vacuum vessel 4 becomes the reference pressure Pres1. In addition, the reference pressure Pres1 stops the repeated processing of the purge gas supply processing to the vacuum vessel 4 and the introduction gas suction processing from the vacuum vessel 4 performed by executing steps 16 to 24 described later. This is the reference pressure. Details of the second predetermined temperature Temp2 and the reference pressure Pres1 will be described later for convenience of explanation.

  If it is determined in step 14 that the detected temperature T2 is lower than the second predetermined temperature Temp2 (T2 <Temp2), the controller 30 turns on (opens) the purge valve 25 and turns off the rough valve 26 (step 16). Close the valve). Thereby, a purge gas (nitrogen gas) at an atmospheric temperature is introduced into the vacuum vessel 4 (purge process). Further, the controller 30 starts a timer provided in the CPU 21 when the purge gas is introduced into the vacuum container 4 and counts the purge time T.

As the purge gas is introduced into the vacuum container 4 in this way, the pressure in the vacuum container 4 rises to about atmospheric pressure (1.0133 × 10 ⁵ Pa). The solid gas 21 is heated by the purge gas and the shield 9 and the cryopanel 10 which are heated by the reverse heating. Thereby, the solid gas 21 is liquefied and falls to the bottom of the shield 9 or the bottom of the vacuum vessel 4. In this embodiment, since the outflow hole 29 is formed in the shield 9, the liquefied gas in the shield 9 flows into the vacuum vessel 4 through the outflow hole 29. FIG. 6 shows a state in which the solid gas 21 is liquefied and accumulated at the bottom of the vacuum vessel 4.

  In the following step 18, (1) whether the internal pressure P of the vacuum vessel 4 detected by the pressure sensor 28 is equal to or lower than the reference pressure Pres1 (P ≦ Pres1), (2) the internal pressure P of the vacuum vessel 4 is the reference pressure. It is determined whether Pres1 is exceeded (P> Pres1) and the purge time T is equal to or longer than the first predetermined purge time Time1. Here, the predetermined purge time Time1 is a time required for almost all of the solid gas in the vacuum vessel 4 to be changed to a liquid gas by performing the purge process in Step 16. The predetermined purge time Time1 is a value obtained empirically or experimentally.

  If it is determined in step 18 that the internal pressure P of the vacuum vessel 4 exceeds the reference pressure Pres1 and the purge time T is equal to or longer than the first predetermined purge time Time1, the controller 30 turns on (opens) the rough valve 26 in step 20. Valve), the roughing process (roughing step) of the vacuum vessel 4 using the roughing pump 13 is started. Accordingly, the purge valve 25 is turned off (closed) in step 22 to stop the introduction of the purge gas into the vacuum vessel 4.

  As a result, the vacuum container 4 is sucked by the roughing pump 13, and the pressure in the vacuum container 4 is reduced. Then, when the pressure in the vacuum vessel 4 becomes equal to or lower than the saturated vapor pressure, the liquid gas boils (reduced pressure boiling). FIG. 7 shows a state where vacuum boiling occurs in the vacuum vessel 4.

  As described above, when the liquid gas is boiled under reduced pressure in the vacuum vessel 4, a part thereof is evaporated and discharged to the outside of the vacuum vessel 4 through the roughing pipe 13 </ b> A along with the suction processing of the roughing pump 13. Further, since the temperature of the gap between the vacuum vessel 4 and the shield 9 is quite high (near the atmospheric temperature), a part of the solid gas is sublimated (vaporized), and the vacuum vessel is passed through the roughing pipe 13A in accordance with the suction process. 4 is discharged to the outside.

  Further, the liquid gas scattered by the boiling under reduced pressure has a low pressure at the point where the liquid gas has jumped, and thus is condensed in various places of the vacuum vessel 4, the shield 9, and the cryopanel 10. At this time, the solid gas is generated in a frost form on the side wall of the vacuum vessel 4 or the like.

  The roughing process in steps 20 and 22 is performed in step 24 for a predetermined roughing time Time2. Then, when the predetermined roughing time Time2 has elapsed, the controller 30 returns to step 14. When an affirmative determination (YES) is made in step 14, the above-described purge process of step 16 is performed again.

  In the purge process, the purge pipe 17 supplies the purge gas to the vacuum vessel 4 as described above, so that the solid gas is liquefied again, part of which is vaporized and discharged from the vacuum vessel 4, and the rest falls. In the bottom of the vacuum vessel 4. FIG. 9 shows a state where the liquid gas has accumulated again at the bottom of the vacuum vessel 4.

  At this time, after the roughing process shown in Steps 20 to 24 is performed, the solid gas is condensed in a state of being widely dispersed in the vacuum vessel 4, the shield 9, and the cryopanel 10 as described above. The heat receiving area from the purge gas and the heat receiving area with the vacuum container are wider than the state where the heat receiving area is simply accumulated on the cryopanel at the bottom of the vacuum container or shield. Therefore, since the heat of the purge gas, the vacuum vessel 4, the shield 9, and the cryopanel 10 can be efficiently transferred to and received from the molten solid gas, vaporization of the molten solid gas is promoted. be able to.

  On the other hand, when it is determined in step 18 that the internal pressure P of the vacuum vessel 4 has become equal to or lower than the reference pressure Pres1 (P ≦ Pres1), the controller 30 turns off (closes) the purge valve 25 to thereby turn off the purge gas vacuum vessel 4. The rough valve 26 is turned on (opened) to start the roughing process, and the pre-rough & purge process is terminated. This pre-rough & purge process corresponds to the period between time t1 and time t2 in the state transition diagram in FIG. Since the purge process and the roughing process are repeatedly performed between the time t1 and the time t2, the internal pressure P of the vacuum vessel 4 periodically varies.

  Here, the reference pressure Pres1 will be described with reference to FIG.

  After the time t1, when the roughing process is performed at the time indicated by the arrow A, the amount of the introduced gas is small because the introduced gas exists in a solid-liquid two-phase state at atmospheric pressure immediately after the start of the pre-rough & purge process. Therefore, the amount of decrease in the internal pressure P of the vacuum vessel 4 is also small. However, after the time A, the amount of gas introduced is increased, and the internal pressure P of the vacuum vessel 4 during the roughing step is greatly reduced. A threshold value at which the internal pressure P of the vacuum vessel 4 becomes difficult to decrease even when the pre-rough & purge process is performed is set as the reference pressure Pres1.

  That is, when the amount of introduced gas remaining in the vacuum vessel 4 decreases, it becomes necessary to carry out the roughing process for a long time in order to discharge it. However, if the roughing time becomes longer, a small amount of the introduced gas remaining on the shield 9 and the cryopanel 10 is solidified again to become a solid gas and takes away latent heat for evaporation, so that the shield 9 and the cryopanel 10 The temperature will drop. Further, when the introduced gas is solidified again to become a solid gas, the time until the temperature of the second-stage refrigeration stage 8 is raised to the regeneration target temperature (shown as T2 target temperature in FIG. 4) is extended.

  In other words, when the internal pressure P of the vacuum vessel 4 after the roughing process is lower than a certain pressure, even if the pre-rough & purge process is further performed, the regeneration efficiency is lowered. The pressure serving as the threshold is the reference pressure Pres1. This reference pressure Pres1 is obtained empirically and experimentally.

  Here, returning to the flowchart of FIG. 3 again, the description will be continued. As described above, when it is determined in step 18 that the internal pressure P of the vacuum vessel 4 has become equal to or lower than the reference pressure Pres1 (P ≦ Pres1), if the pre-rough & purge process is further continued as described above, the process returns. Since the regeneration efficiency is lowered, the pre-rough & purge process is completed through the process of step 26.

  On the other hand, from the state transition diagram shown in FIG. 4, the temperature of the second stage refrigeration stage 8 at which the internal pressure P of the vacuum vessel 4 becomes the reference pressure Pres1 is Temp2 (hereinafter referred to as the reference temperature). Therefore, in step 14, in order to increase the reliability of the cryopump 1, the temperature of the second stage refrigeration stage 8 measured by the second stage temperature sensor 19 is equal to or higher than the reference temperature Temp2 (T2 ≧ Temp2). In addition, the pre-rough & purge process is terminated. Thereby, the pre-rough & purge process is performed more than necessary, and this can more reliably prevent the regeneration efficiency from decreasing.

  When the pre-rough & purge process shown in FIG. 3 is completed, the cryopump 1 performs a normal regeneration process. That is, the purge gas is introduced into the vacuum vessel 4 and the reversible motor 16 is rotated in the reverse direction to place the refrigerator 5 in the regeneration mode, whereby the temperature of the shield 9 and the cryopanel 10 is increased. This normal regeneration process is performed until the temperature of the second stage refrigeration stage 8 measured by the second stage temperature sensor 19 reaches the target regeneration temperature (shown as T1 target temperature in FIG. 4).

  Here, the reproduction time according to the present embodiment is compared with the reproduction time in the comparative example with reference to FIG. Specifically, the time when the temperature Tc2 of the comparative example (temperature of the second stage refrigeration stage) and the temperature T2 (second stage refrigeration stage 8 temperature) according to the present embodiment reach the T1 target temperature is compared. Then, in the comparative example, the T1 target temperature is reached at time t4, whereas in the cryopump 1 according to the present embodiment, the T1 target temperature is reached at time t3. Therefore, it can be seen that the reproduction time can be shortened by the time ΔT in this embodiment as compared with the comparative example. This is because, in the cryopump 1 according to the present embodiment, the pre-rough & purge process with high introduced gas discharge efficiency is performed before the normal regeneration process is performed. Thus, according to the cryopump 1 and the regeneration method according to the present embodiment, it is possible to improve the efficiency of the regeneration process, thereby shortening the temperature rising time.

FIG. 1 is a configuration diagram of a cryopump according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a hardware configuration of the controller. FIG. 3 is a flowchart of the regeneration process of the cryopump according to the embodiment of the present invention. FIG. 4 shows a cryopump according to an embodiment of the present invention, and is a diagram showing a state where solid gas is condensed on a cryopanel or the like. FIG. 5 is a transition diagram of a cryopump that is an example of the present invention. FIG. 6 shows a cryopump according to an embodiment of the present invention, and is a diagram showing a state in which liquid gas is accumulated in the vacuum vessel by the regeneration process. FIG. 7 shows a cryopump according to an embodiment of the present invention, and is a diagram showing a vacuum boiling state. FIG. 8 shows a cryopump according to an embodiment of the present invention, and is a diagram showing a state where the liquid gas scattered by the boiling under reduced pressure is condensed again. FIG. 9 shows a cryopump according to an embodiment of the present invention, and is a diagram showing a state in which a solid gas scattered and condensed by boiling under reduced pressure becomes a liquid gas again.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cryo pump 3 Compressor 4 Vacuum vessel 5 Refrigerator 7 First stage refrigeration stage 8 Second stage refrigeration stage 9 Shield 10 Cryo panel 13 Roughing pump 13A Roughing piping 14 First stage cylinder 14A First stage displacer 15 First Second stage cylinder 15A Second stage displacer 16 Reversible motor 17 Purge piping 18 First stage temperature sensor 19 Second stage temperature sensor 21 Solid gas 22 Liquid gas 25 Purge valve 26 Rough valve 27 Vent valve 28 Pressure sensor 30 Controller

Claims (6)

A vacuum vessel;
A cryopanel and a shield disposed in the vacuum vessel;
A refrigerator that condenses the gas in the vacuum vessel by cooling the cryopanel and the shield;
Purge gas supply means for supplying a purge gas to the vacuum vessel;
A suction means for sucking the gas in the vacuum vessel;
Control means for repeatedly performing the supply process of the purge gas to the vacuum container by the purge gas supply means and the suction process of the gas from the inside of the vacuum container by the suction means during the temperature rise in the regeneration. Features a cryopump. While providing a temperature sensor in the vacuum vessel,
When the control means determines that the temperature in the vacuum vessel is a temperature at which the gas coexists in a solid-liquid two-phase, based on the output of the temperature sensor, a supply process of a purge gas to the vacuum vessel, and the vacuum vessel The cryopump according to claim 1, wherein the gas suction process from the inside is repeatedly performed.   The cryopump according to claim 1, wherein the time for sucking the gas from the vacuum container is set to a time during which the liquefied gas can be boiled under reduced pressure in the vacuum container. A vacuum vessel, a cryopanel and a shield disposed in the vacuum vessel, a refrigerator that condenses the gas in the vacuum vessel by cooling the cryopanel and the shield, and a supply of purge gas to the vacuum vessel A cryopump regeneration method comprising: a purge gas supply means for carrying out; and a suction means for sucking the gas in the vacuum vessel.
A cryopump characterized by repeatedly performing a purge gas supply process to the vacuum container by the purge gas supply means and a suction process of the gas from the vacuum container by the suction means in the middle of temperature increase in regeneration. How to play.   When the temperature of the gas condensed on the cryopanel reaches a temperature in which two phases of solid and liquid coexist, the supply process of the purge gas to the vacuum container and the suction process of the gas from the vacuum container are repeatedly performed. The cryopump regeneration method according to claim 4, wherein the processing is started. 6. The cryopump according to claim 4, wherein the time for sucking the gas from the vacuum container is set to a time during which the liquefied gas can be boiled under reduced pressure in the vacuum container. Playback method.

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