Cryopump and cryopump regeneration method

Abstract

To suppress a danger gas concentration discharged from a cryopump during regeneration of the cryopump.SOLUTION: A method for regenerating a cryopump comprises supplying a diluent gas to a cryopump 10 during cooling operation, accumulating the diluent gas on a cryogenic surface in the cryopump 10, revaporizing other gases captured on the cryogenic surface together with the diluent gas, and discharging a mixture of the revaporized gas and the diluent gas from the cryopump 10. The diluent gas may be a purge gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cryopump and a cryopump regeneration method.

Background Art

[0002] A cryopump is a vacuum pump that captures gas molecules by condensation or adsorption on a cryopanel cooled to an extremely low temperature and exhausts them. Cryopumps are generally used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes and the like. Since a cryopump is a so-called gas storage type vacuum pump, it requires regeneration to periodically discharge the captured gas to the outside.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In semiconductor manufacturing processes, dangerous gases with various hazards such as explosiveness, corrosiveness, and toxicity may be used. The dangerous gases stored in the cryopump are discharged from the cryopump by regeneration. Immediately after the start of regeneration, due to the temperature rise of the cryopump, the stored dangerous gases rapidly revaporize, and the concentration of the dangerous gases in the cryopump can increase significantly.

[0005] One exemplary object of an aspect of the present invention is to suppress the concentration of dangerous gases discharged from the cryopump during regeneration of the cryopump.

Means for Solving the Problems

[0006] According to one aspect of the present invention, the cryopump comprises a cryopump vessel, a cryopanel disposed within the cryopump vessel, a refrigerator installed in the cryopump vessel and thermally coupled to the cryopanel, a body purge valve for supplying purge gas to the cryopump vessel, and a regeneration controller configured to control the body purge valve so that purge gas is supplied to the cryopump vessel during the cooling operation of the refrigerator for cooling the cryopanel.

[0007] According to one aspect of the present invention, a cryopump regeneration method comprises supplying a diluent gas to a cryopump during the cooling operation of the cryopump's refrigerator, accumulating the diluent gas on the cryogenic surface inside the cryopump, revaporizing other gases trapped on the cryogenic surface together with the diluent gas, and discharging a mixed gas of the revaporized gas and the diluent gas from the cryopump.

[0008] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0009] According to the present invention, the concentration of hazardous gases discharged from the cryopump during cryopump regeneration can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] A schematic diagram of a cryopump system according to an embodiment is shown. [Figure 2] A schematic diagram of a cryopump system according to an embodiment is shown. [Figure 3] This flowchart shows an exemplary cryopump regeneration method according to an embodiment. [Figure 4] Figure 3 is a flowchart showing an example of a cryopump regeneration method. [Figure 5]This flowchart shows an exemplary cryopump regeneration method according to an embodiment. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0012] Figures 1 and 2 schematically illustrate a cryopump system according to an embodiment. Figure 1 schematically shows the external appearance of the cryopump 10, and Figure 2 schematically shows the internal structure of the cryopump 10. The cryopump 10 is used to raise the vacuum level inside the vacuum chamber 100 to the level required for a desired vacuum process, for example, by being installed in a vacuum chamber 100 of an ion implantation apparatus, sputtering apparatus, deposition apparatus, or other vacuum process apparatus. -5 Pa~10 -8 A high vacuum level of approximately Pa is achieved in the vacuum chamber 100.

[0013] The cryopump 10 comprises a compressor 12, a refrigerator 14, and a cryopump vessel 16. The cryopump vessel 16 has a cryopump intake port 17. The cryopump 10 also includes a rough valve 18, a body purge valve 20, a discharge valve 22, and a discharge purge valve 24, which are installed in the cryopump vessel 16.

[0014] The compressor 12 is configured to recover refrigerant gas from the chiller 14, pressurize the recovered refrigerant gas, and supply it back to the chiller 14. The chiller 14, also called the expander or cold head, together with the compressor 12 constitutes a cryogenic chiller. The circulation of refrigerant gas between the compressor 12 and the chiller 14 occurs with a combination of appropriate pressure and volume fluctuations of the refrigerant gas within the chiller 14, thereby creating a thermodynamic cycle that generates cold, and the chiller 14 can provide cryogenic cooling. The refrigerant gas is usually helium, but other suitable gases may be used. For understanding, the direction of refrigerant gas flow is indicated by arrows in Figure 1. The cryogenic chiller is, as an example, a two-stage Gifford-McMahon (GM) chiller, but may be a pulse tube chiller, a Stirling chiller, or other type of cryogenic chiller.

[0015] As shown in Figure 2, the refrigerator 14 comprises a room temperature section 26, a first cylinder 28, a first cooling stage 30, a second cylinder 32, and a second cooling stage 34. The refrigerator 14 is configured to cool the first cooling stage 30 to a first cooling temperature and the second cooling stage 34 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage 30 is cooled to about 65K to 120K, preferably 80K to 100K, and the second cooling stage 34 is cooled to about 10K to 20K. The first cooling stage 30 and the second cooling stage 34 may also be called a high-temperature cooling stage and a low-temperature cooling stage, respectively. By cooling the first cooling stage 30 and the second cooling stage 34 to their respective target cooling temperatures, the cryopump 10 can perform vacuum evacuation operation.

[0016] The first cylinder 28 connects the first cooling stage 30 to the room temperature section 26, whereby the first cooling stage 30 is structurally supported by the room temperature section 26. The second cylinder 32 connects the second cooling stage 34 to the first cooling stage 30, whereby the second cooling stage 34 is structurally supported by the first cooling stage 30. The first cylinder 28 and the second cylinder 32 extend coaxially along the radial direction, and the room temperature section 26, the first cylinder 28, the first cooling stage 30, the second cylinder 32, and the second cooling stage 34 are linearly arranged in this order in a row.

[0017] When the refrigerator 14 is a two-stage GM refrigerator, a first displacer and a second displacer (not shown) are reciprocally arranged inside the first cylinder 28 and the second cylinder 32, respectively. A first regenerator and a second regenerator (not shown) are incorporated in the first displacer and the second displacer, respectively. Further, the room temperature section 26 has a drive mechanism (not shown) such as a motor 26a for reciprocating the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically repeat the supply and discharge of the working gas to the inside of the refrigerator 14.

[0018] In addition, the cryopump 10 includes a radiation shield 36 and a cryopanel 38. The radiation shield 36 ,nine is thermally coupled to the first cooling stage 30 and cooled to the first cooling temperature in order to provide a cryogenic surface for protecting the cryopanel 38 from the radiant heat from the outside of the cryopump 10 or the cryopump container 16.

[0019] The radiation shield 36 has, for example, a cylindrical shape and is arranged to surround the cryopanel 38 and the second cooling stage 34. The end of the radiation shield 36 on the side of the cryopump intake port 17 is open, and gas entering from outside the cryopump 10 through the cryopump intake port 17 can be received into the radiation shield 36. The end of the radiation shield 36 on the side opposite to the cryopump intake port 17 may be closed, or may have an opening, or may be open. The radiation shield 36 has a gap between it and the cryopanel 38, and the radiation shield 36 is not in contact with the cryopanel 38. The radiation shield 36 is also not in contact with the cryopump container 16.

[0020] An inlet baffle 37 may be provided at the cryopump intake port 17 or between the cryopump intake port 17 and the cryopanel 38 to protect the cryopanel 38 from radiant heat from a heat source outside the cryopump 10 (for example, a heat source within the vacuum chamber 100 to which the cryopump 10 is attached). The inlet baffle 37 may be fixed to the open end of the radiation shield 36 and thermally coupled to the first cooling stage 30 of the refrigerator 14 through the radiation shield 36. Alternatively, the inlet baffle 37 may be attached to the first cooling stage 30. The inlet baffle 37 is cooled to the same temperature as the radiation shield 36 and can condense a so-called type 1 gas (a gas that condenses at a relatively high temperature such as water vapor) on its surface.

[0021] The cryopanel 38 is thermally coupled to the second cooling stage 34 and cooled to a second cooling temperature in order to provide a cryogenic surface for condensing type 2 gases (e.g., gases that condense at relatively low temperatures, such as argon and nitrogen). In addition, at least a portion of the surface of the cryopanel 38 (e.g., the surface opposite the cryopump intake port 17) is fitted with, for example, activated carbon or other adsorbent material to adsorb type 3 gases (e.g., non-condensable gases, such as hydrogen). Gases entering the radiant shield 36 from outside the cryopump 10 through the cryopump intake port 17 are captured by condensation or adsorption on the cryopanel 38. The arrangement and shape of the radiant shield 36 and the cryopanel 38 can take various known configurations as appropriate, so they will not be described in detail here.

[0022] The cryopump vessel 16 has a vessel body 16a and a refrigerator housing cylinder 16b. The cryopump vessel 16 is a vacuum vessel designed to maintain a vacuum during the vacuum evacuation operation of the cryopump 10 and to withstand the pressure of the surrounding environment (e.g., atmospheric pressure). The vessel body 16a has a cylindrical shape with a cryopump intake port 17 at one end and the other end closed. The vessel body 16a houses a radiation shield 36, and as described above, the cryopanel 38 is housed inside the radiation shield 36 together with the second cooling stage 34. The refrigerator housing cylinder 16b is connected at one end to the vessel body 16a and fixed at the other end to the room temperature section 26 of the refrigerator 14. The refrigerator 14 is inserted into the refrigerator housing cylinder 16b and houses the first cylinder 28.

[0023] In this embodiment, the cryopump 10 is a so-called horizontal cryopump in which the refrigerator 14 is located on the side of the container body 16a. A refrigerator inlet is provided on the side of the container body 16a, and the refrigerator housing cylinder 16b is coupled to the side of the container body 16a at this refrigerator inlet. Similarly, adjacent to the refrigerator inlet of the container body 16a, a hole for passing the refrigerator 14 is also provided on the side of the radiation shield 36. The second cylinder 32 and the second cooling stage 34 of the refrigerator 14 are inserted into the radiation shield 36 through these holes, and the radiation shield 36 is thermally coupled to the first cooling stage 30 around the holes on its side.

[0024] The cryopump 10 can be installed in the vacuum chamber 100 in various orientations at the site of use. For example, the cryopump 10 can be installed in the lateral orientation shown in the figure, i.e., with the cryopump intake port 17 facing upward. In this case, the bottom of the container body 16a is located below the cryopump intake port 17, and the refrigerator 14 extends horizontally.

[0025] The cryopump 10 includes a first temperature sensor 40 for measuring the temperature of the first cooling stage 30 and a second temperature sensor 42 for measuring the temperature of the second cooling stage 34. The first temperature sensor 40 is attached to the first cooling stage 30. The second temperature sensor 42 is attached to the second cooling stage 34. The temperature of the first cooling stage 30 measured by the first temperature sensor 40 can be considered as the temperature of the radiation shield 36, and the temperature of the second cooling stage 34 measured by the second temperature sensor 42 can be considered as the temperature of the cryopanel 38. Therefore, the first temperature sensor 40 can measure the temperature of the radiation shield 36 and output a first measured temperature signal indicating the measured temperature of the radiation shield 36. The second temperature sensor 42 can measure the temperature of the cryopanel 38 and output a second measured temperature signal indicating the measured temperature of the cryopanel 38. In addition, a pressure sensor 44 is provided inside the cryopump container 16. The pressure sensor 44 is installed, for example, in the refrigerator housing cylinder 16b, and can measure the internal pressure of the cryopump container 16 and output a measured pressure signal indicating the measured pressure.

[0026] Furthermore, the cryopump 10 is equipped with a controller 46 that controls the cryopump 10. The controller 46 may be integrated with the cryopump 10, or it may be configured as a separate control device from the cryopump 10.

[0027] The controller 46 may control the refrigerator 14 based on the cooling temperature of the radiant shield 36 and / or cryopanel 38 during vacuum evacuation operation of the cryopump 10. The controller 46 may be connected to the first temperature sensor 40 to receive a first measured temperature signal from the first temperature sensor 40, and to the second temperature sensor 42 to receive a second measured temperature signal from the second temperature sensor 42.

[0028] Furthermore, the controller 46 can operate as a regeneration controller for the cryopump 10. During the regeneration operation of the cryopump 10, the controller 46 may control the chiller 14, rough valve 18, body purge valve 20, discharge valve 22, and discharge purge valve 24 based on the pressure in the cryopump vessel 16 (or, if necessary, based on the temperature of the cryopanel 38 and the pressure in the cryopump vessel 16). The controller 46 may be connected to the pressure sensor 44 to receive the measured pressure signal from the pressure sensor 44.

[0029] The internal configuration of the controller 46 is realized in hardware form by components and circuits such as the CPU and memory of a computer, and in software form by computer programs, etc., but in the diagram, it is depicted as functional blocks realized through the coordination of these components as appropriate. It will be understood by those skilled in the art that these functional blocks can be realized in various ways by combinations of hardware and software.

[0030] For example, the controller 46 can be implemented as a combination of a processor (hardware) such as a CPU (Central Processing Unit) or microcontroller, and a software program executed by the processor (hardware). The software program may be a computer program that causes the controller 46 to perform regeneration of the cryopump 10.

[0031] The rough valve 18 is installed in the cryopump container 16, for example, the refrigerator housing cylinder 16b. The rough valve 18 is connected to a rough pump (not shown) installed outside the cryopump 10. The rough pump is a vacuum pump used to evacuate the cryopump 10 to its operating pressure. When the rough valve 18 is opened under the control of the controller 46, the cryopump container 16 is connected to the rough pump, and when the rough valve 18 is closed, the cryopump container 16 is disconnected from the rough pump. By opening the rough valve 18 and operating the rough pump, the cryopump 10 can be depressurized.

[0032] The body purge valve 20 enables "body purging," which involves supplying purge gas to the container body 16a of the cryopump container 16. In an exemplary configuration, the body purge valve 20 is installed in the cryopump container 16, for example, in the container body 16a. The body purge valve 20 is also connected to a purge gas source 48 or purge gas supply device installed outside the cryopump 10.

[0033] When the body purge valve 20 is opened under the control of the controller 46, purge gas is supplied from the purge gas source 48 to the cryopump container 16, and when the body purge valve 20 is closed, the supply of purge gas to the cryopump container 16 is cut off. By opening the body purge valve 20 and introducing purge gas into the cryopump container 16, the cryopump 10 can be pressurized. In addition, the cryopump 10 can be heated from cryogenic temperatures to room temperature or higher. Alternatively, as described later, by adjusting the flow rate of purge gas with the body purge valve 20, the pressure and temperature inside the cryopump 10 can be maintained, or a significant increase can be suppressed, while supplying purge gas to the cryopump 10.

[0034] The purge gas may be, for example, nitrogen gas or other dry gas, and the temperature of the purge gas may be adjusted to, for example, room temperature (above 0°C, for example 15°C to 30°C), or heated to a temperature higher than room temperature (for example 50°C or below or 80°C or below). Alternatively, the temperature of the purge gas may be cooled to a temperature lower than room temperature (for example, below 0°C). Cooling the purge gas may be preferable in suppressing the temperature rise of the cryopanel 38 when the purge gas is supplied to the cryopump vessel 16 during the cooling operation of the refrigerator 14, as described later.

[0035] The discharge valve 22 is installed in the cryopump container 16, for example, in the chiller housing cylinder 16b. The discharge valve 22 is provided as the outlet of the cryopump container 16 to discharge fluid from the inside of the cryopump 10 to the outside. The discharge valve 22 is also the inlet to the discharge line 50, which will be described later. When the discharge valve 22 is opened by the control of the controller 46, fluid is discharged from the cryopump container 16, and when the discharge valve 22 is closed, the discharge of fluid from the cryopump container 16 is shut off. The fluid discharged from the discharge valve 22 is basically a gas, but it may be a liquid or a mixture of gas and liquid. The discharge valve 22 may be, for example, a normally closed control valve.

[0036] In addition, the discharge valve 22 may function as a vent valve or safety valve and may be configured to open mechanically when a predetermined differential pressure is applied. In that case, if the inside of the cryopump becomes high pressure for any reason, the discharge valve 22 will open mechanically without requiring any control. This will allow the high pressure inside to be released into the discharge line 50.

[0037] The discharge purge valve 24 enables "discharge purging," which supplies purge gas to the discharge line 50. In an exemplary configuration, the discharge valve 22 and the discharge purge valve 24 may be provided separately, with the discharge purge valve 24 connected by piping downstream of the discharge valve 22. Alternatively, the discharge purge valve 24 may be provided integrally with the discharge valve 22 to supply purge gas to the discharge valve 22 or downstream of it. The discharge purge valve 24 may be installed in the cryopump vessel 16, for example, the chiller housing cylinder 16b. The discharge purge valve 24 is connected to the purge gas source 48 or another purge gas source.

[0038] When the discharge purge valve 24 is opened by the control of the controller 46, purge gas is supplied from the purge gas source 48 to the discharge line 50, and when the discharge purge valve 24 is closed, the supply of purge gas to the discharge line 50 is cut off. The purge gas supplied from the discharge purge valve 24 is usually the same type of gas as the purge gas supplied from the body purge valve 20 (for example, nitrogen gas), but a suitable different type of gas may be used.

[0039] The discharge line 50 is provided to discharge the discharge fluid from the cryopump 10 to the processing unit 60, and is connected to the discharge valve 22 and the discharge purge valve 24 at its upstream end and to the processing unit 60 at its downstream end.

[0040] The treatment device 60 may be, for example, a pollution control device that treats hazardous gases contained in the discharge fluid (e.g., hydrogen gas, or other explosive gases, or other corrosive or toxic gases such as fluorine-based gases or halogen-based gases) to produce harmless gases, or it may be a treatment device that treats hazardous gases to reduce their hazard. As such a treatment device 60, known pollution control devices or treatment devices can be appropriately adopted, so their details will not be described here.

[0041] As the vacuum evacuation operation of the cryopump 10 continues, gas accumulates in the cryopump 10. To discharge the accumulated gas to the outside, the cryopump 10 is regenerated. The regeneration of the cryopump 10 generally includes a heating process, a discharge process, and a cool-down process.

[0042] A gate valve 102 is installed between the cryopump 10 and the vacuum chamber 100 that is evacuated. When regeneration of the cryopump 10 is started, the gate valve 102 is closed, and the cryopump 10 is isolated from the vacuum chamber 100 (the internal volume of the cryopump 10 is isolated from the vacuum chamber 100).

[0043] The heating step includes heating the cryopump 10 to the boiling point of the hazardous gas among the gases captured in the cryopump 10, or a temperature above that, and further heating the cryopump 10 to the regeneration temperature. The hazardous gas is typically, for example, a type 2 gas or a type 3 gas, and the boiling point of the hazardous gas is, for example, below 100K. The regeneration temperature is, for example, room temperature or higher. Therefore, in many cases, the hazardous gas revaporizes in the first half of the heating step, especially immediately after the start, and is discharged from the cryopump 10 and flows into the treatment device 60. The hazardous gas is removed from the cryopump 10 in the heating step.

[0044] The heat source for raising the temperature is, for example, the refrigerator 14. The refrigerator 14 enables heating operation (so-called reverse heating). That is, the refrigerator 14 is configured such that when the drive mechanism provided in the room temperature section 26 operates in the opposite direction to the cooling operation (i.e., the motor 26a rotates in reverse), adiabatic compression occurs in the working gas. The heat of compression thus obtained allows the refrigerator 14 to heat the first cooling stage 30 and the second cooling stage 34. The radiant shield 36 and the cryo panel 38 are heated using the first cooling stage 30 and the second cooling stage 34 as heat sources, respectively. In addition, the purge gas supplied into the cryopump container 16 from the body purge valve 20 can also contribute to raising the temperature of the cryopump 10. Alternatively, the cryopump 10 may be provided with a heating device such as an electric heater. For example, an electric heater that can be controlled independently of the operation of the refrigerator 14 may be attached to the first cooling stage 30 and / or the second cooling stage 34 of the refrigerator 14.

[0045] In the discharge process, the gas captured by the cryopump 10 is re-vaporized or liquefied and discharged as gas, liquid, or a mixture of gas and liquid through the discharge line 50 or through the rough valve 18. Since type 2 and type 3 gases can already be easily discharged from the cryopump 10 in the heating process, the discharge process is mainly for discharging type 1 gas. Once the discharge process is complete, the cool-down process begins. In the cool-down process, the cryopump 10 is re-cooled to an extremely low temperature for vacuum evacuation operation. Once regeneration is complete, the gate valve 102 is opened again, and the cryopump 10 can start vacuum evacuation operation again.

[0046] Incidentally, one of the main applications of the cryopump 10 is the vacuum evacuation of ion implantation equipment. In this case, hydrogen gas is mainly stored in the cryopump 10. The hydrogen gas captured in the cryopanel 38 can re-vaporize all at once during regeneration, especially immediately after the start of regeneration (heating process). In existing regeneration methods, the hydrogen gas is diluted by body purging in the cryopump vessel 16, but even so, the discharge fluid flowing from the cryopump vessel 16 through the discharge line 50 to the treatment device 60 can temporarily contain hydrogen gas at a fairly high concentration.

[0047] Because high concentrations of hydrogen gas pose an explosion or combustion risk, it is desirable to keep the hydrogen gas concentration peak in the discharge fluid as low as possible for safety management of the cryopump 10 and discharge line 50. The hydrogen gas concentration peak may be desirable to keep below 4%, for example, considering the explosion limit. Alternatively, considering a safety factor, the hydrogen gas concentration peak may be desirable to keep it even lower, for example, below 2%. Diluting the inside of the cryopump vessel 16 to such low concentrations by body purging may require a fairly large flow rate of purge gas (e.g., several hundred liters per minute) immediately after the start of regeneration. Similarly, for other types of hazardous gases, a temporarily large flow rate of purge gas may be required to suppress the concentration peak immediately after the start of regeneration. However, such measures may not be practical considering the increased costs involved.

[0048] Figure 3 is a flowchart illustrating an exemplary cryopump regeneration method according to an embodiment. The cryopump regeneration method comprises supplying a diluent gas to the cryopump 10 (S10), accumulating the diluent gas on the cryogenic surface inside the cryopump 10 during the cooling operation (S11), revaporizing other gases trapped on the cryogenic surface together with the diluent gas (S12), and discharging a mixed gas of the revaporized gas and diluent gas from the cryopump 10 (S13). The revaporization of the gas (S12) and the discharge of the mixed gas (S13) may be included in the heating step described above. This method may further include the discharge step (S14) and the cool-down step (S15) described above.

[0049] In this way, the diluent gas can be pre-stored on the cryogenic surface within the cryopump 10. Therefore, even if a hazardous gas is absorbed within the cryopump 10, the diluent gas will re-vaporize along with the hazardous gas during regeneration. This allows for dilution of the hazardous gas within the cryopump 10, thereby suppressing the concentration of the hazardous gas discharged from the cryopump 10 during regeneration. This improves the safety of the cryopump 10 regeneration.

[0050] The dilution gas may be a purge gas. The cryogenic surface is a surface cooled to the temperature at which the dilution gas condenses, and may be, for example, the surface of the cryopanel 38 or the second cooling stage 34. Alternatively, the cryogenic surface may be any other surface within the cryopump 10, as long as it is cooled to the temperature at which the dilution gas condenses, and may be, for example, the radiation shield 36, the inlet baffle 37, or the surface of the refrigerator 14 (e.g., the first cooling stage 30, the second cylinder 32). Any other gas trapped on the cryogenic surface may include hazardous gases (e.g., hydrogen gas).

[0051] In the exemplary implementation of the regeneration method shown in Figure 3 for the cryopump 10, body purging is performed while the cryopump 10 is cooling, that is, during the cooling operation of the refrigerator 14. This allows the purge gas to condense on the cryogenic surface, such as the cryopanel 38, and be absorbed into the cryopump 10. In this way, a large amount of purge gas can be introduced into the cryopump 10 in advance before the heating step in the regeneration of the cryopump 10 and temporarily stored in the cryopump container 16 in a solid or liquid state. During the heating step, a large amount of purge gas is revaporized along with other gases, such as hazardous gases, that were captured on the cryopanel 38 by the vacuum evacuation operation of the cryopump 10.

[0052] Therefore, compared to existing regeneration methods that do not involve the prior introduction of such purge gas, the regeneration method according to this embodiment can reduce the concentration of hazardous gas in the cryopump 10. As a result, the concentration of hazardous gas in the gas discharged from the cryopump 10 and flowing through the discharge line 50 can also be reduced.

[0053] Therefore, the controller 46 may be configured to control the body purge valve 20 so that purge gas is supplied to the cryopump vessel 16 during the cooling operation of the chiller 14 that cools the cryopanel 38. The controller 46 may be configured to know the operating status of the chiller 14, for example, by receiving or generating a chiller status signal indicating the operating status of the chiller 14. The chiller status signal may indicate the current state of the chiller 14 from among several states, including cooling operation, stop, and reverse heating operation. Alternatively, the controller 46 may receive the measured temperatures of the first temperature sensor 40 and / or the second temperature sensor 42 and determine whether the chiller 14 is in cooling operation based on these measured temperatures. The controller 46 may be configured to open the body purge valve 20 when the chiller 14 is in cooling operation based on the chiller status signal or based on the measured temperature.

[0054] Generally, the body purge valve 20 is configured to allow a relatively large purge gas flow rate desired for the regeneration heating and discharge processes. As mentioned above, the purge gas has a temperature near room temperature and is considerably hotter than the cryopanel 38 under cooling, so the cryopanel 38 can be heated by body purging even though the refrigerator 14 is operating in cooling mode. Excessive heating can prevent the condensation of the purge gas onto the cryopanel 38.

[0055] Therefore, the controller 46 may be configured to control the body purge valve 20 so that purge gas is supplied to the cryopump vessel 16 even after the cooling operation of the refrigerator 14 is completed (i.e., during the heating process and / or discharge process), and the flow rate of purge gas supplied during the cooling operation may be less than the flow rate of purge gas supplied after the cooling operation is completed. In this way, preferably, the flow rate of purge gas in the pre-introduction of purge gas for dilution according to the embodiment can be suppressed compared to the normal body purging (i.e., during the heating process and / or discharge process). This makes it possible to suppress the heat input to the cryopump 10 associated with the pre-introduction of purge gas.

[0056] In the exemplary cryopump 10, from the viewpoint of cost reduction, the body purge valve 20 may be an on / off valve, and the purge gas flow rate of the body purge valve 20 is constant. In this case, in order to suppress the purge gas flow rate, the controller 46 may be configured to control the body purge valve 20 so that the purge gas is intermittently supplied to the cryopump vessel 16 during the cooling operation of the chiller 14.

[0057] Furthermore, the controller 46 may be configured to control the chiller 14 so that its cooling capacity increases when purge gas is supplied compared to before the supply of purge gas. As an exemplary configuration of the chiller 14 with adjustable cooling capacity, the motor 26a that drives the chiller 14 may be configured to have a variable operating frequency, and an inverter may be provided to control the operating frequency of the motor 26a. In this case, the controller 46 may control the inverter so that the operating frequency of the motor 26a increases compared to before the supply of purge gas when purge gas is supplied. In this way, the cooling capacity of the chiller 14 can be increased when purge gas is supplied, thereby suppressing the temperature rise of the cryopump 10 associated with the pre-introduction of purge gas.

[0058] Figure 4 is a flowchart illustrating an example of the cryopump regeneration method shown in Figure 3. The purge gas pre-introduction process shown in Figure 4 may be executed by the controller 46 upon receiving a regeneration start command. The regeneration start command may be input to the controller 46 from the user of the cryopump 10, or from a higher-level controller such as the control unit of a vacuum process apparatus on which the cryopump 10 is installed.

[0059] As shown in Figure 4, when this process is started, the cooling capacity of the refrigerator 14 is first increased (S20). For example, the controller 46 may control the motor 26a to increase the operating frequency of the motor 26a that drives the refrigerator 14. Generally, before the regeneration of the cryopump 10 starts, the refrigerator 14 is operated at a relatively low operating frequency (e.g., lower than 50 Hz or 60 Hz) to stably maintain the temperature of the cryopanel 38 cooled to an extremely low temperature. Therefore, the controller 46 may increase the operating frequency of the motor 26a to an operating frequency that exceeds such a relatively low operating frequency. The operating frequency of the motor 26a may be increased to, for example, an operating frequency higher than 50 Hz or 60 Hz, or to the maximum operating frequency that the motor 26a can take. The maximum operating frequency of the motor 26a may be, for example, in the range of 70 Hz to 100 Hz.

[0060] Then, the body purge valve 20 is opened for a predetermined time (S22). The controller 46 controls the body purge valve 20 to open, keep it open for this predetermined time, and close the body purge valve 20 when the predetermined time has elapsed.

[0061] Here, the predetermined time for opening the body purge valve 20 may be set in advance so that the amount of purge gas supplied to the cryopump vessel 16 through the body purge valve 20 during that time is, for example, within approximately 1 liter, or within approximately 0.5 liters, or within approximately 0.2 liters, under standard conditions (e.g., 0°C and 1 atm). This can be achieved by selecting the predetermined time for opening the body purge valve 20 from a range of, for example, 0.1 seconds to 2 seconds (or, for example, 0.5 seconds to 1 second). This predetermined time may be obtained in advance based on the empirical knowledge of the designer of the cryopump 10 or experiments and simulations conducted by the designer, and stored in the controller 46. In this way, it is expected that the temperature rise of the cryopanel 38 caused by the purge gas supplied to the cryopump vessel 16 through the body purge valve 20 can be made sufficiently small for practical use.

[0062] Next, the controller 46 determines whether the predetermined conditions for the completion of purge gas supply have been met (S24). The supply completion conditions may be set based on the amount of purge gas required to dilute the maximum specified amount of hazardous gas (e.g., hydrogen gas) that can be stored in the cryopump 10 to a desired low concentration. For example, the supply completion condition may be that the number of times or duration of openings of the body purge valve 20 to supply this required amount of purge gas has been completed. For example, if it is necessary to open the body purge valve 20 for a predetermined duration 10 times to supply the required amount of purge gas, the supply completion condition is met when the body purge valve 20 has been opened 10 times. Alternatively, if it is necessary to open the body purge valve 20 for a total of 10 seconds for a predetermined duration to supply the required amount of purge gas, the supply completion condition is met when the body purge valve 20 has been opened for a total of 10 seconds. The conditions for completing supply may be obtained in advance based on the empirical knowledge of the designer of the cryopump 10 or through experiments or simulations conducted by the designer, and may be stored in the controller 46 beforehand.

[0063] If the supply completion condition is not met (No. in S24), the controller 46 obtains the measured temperature T2 of the cryopanel 38 by the second temperature sensor 42 and compares the measured temperature T2 with a cryogenic temperature threshold Ts (S26). This temperature threshold Ts is preset from a range lower than the boiling point of the purge gas, for example from 10K to 30K (or for example from 10K to 20K), to ensure that the cryopanel 38 is at a temperature low enough to condense the purge gas, and is stored in the controller 46.

[0064] The controller 46 is configured to control the body purge valve 20 so that purge gas is supplied when the measured temperature T2 falls below the cryogenic temperature threshold Ts. That is, if the measured temperature T2 is equal to or greater than the temperature threshold Ts (No in S26), the controller 46 waits for a predetermined time, then takes the measured temperature T2 again and compares it with the temperature threshold Ts (S26). On the other hand, if the measured temperature T2 is lower than the temperature threshold Ts (Yes in S26), the controller 46 opens the body purge valve 20 again (S22).

[0065] In this way, after confirming that the measured temperature T2 of the cryopanel 38 is lower than the temperature threshold Ts, the body purge valve 20 can be opened and purge gas can be supplied to the cryopump vessel 16. If the measured temperature T2 of the cryopanel 38 is higher than the temperature threshold Ts, the body purge valve 20 can be closed and the system can wait until the measured temperature T2 falls below the temperature threshold Ts.

[0066] Subsequently, it is determined again whether the conditions for completion of purge gas supply are met (S24). If the conditions for completion of supply are not met (No in S24), temperature measurement and comparison and intermittent supply of purge gas are performed again as described above. On the other hand, if the conditions for completion of supply are met (Yes in S24), this process is terminated. In this case, the cooling operation of the refrigerator 14 is stopped, and the heating process (S12, S13 in Figure 3), discharge process (S14), and cool-down process (S15) described above are performed.

[0067] In the above-described embodiment, the case in which the body purge valve 20 is an on / off valve that supplies purge gas at a fixed constant flow rate is described as an example. However, in one embodiment, the body purge valve 20 may be a variable flow rate valve that can adjust the flow rate of the purge gas. In this case, the controller 46 may be configured to control the body purge valve 20 so that purge gas is continuously supplied to the cryopump vessel 16 during the cooling operation of the chiller 14. The controller 46 may also control the body purge valve 20 so that the flow rate of purge gas continuously supplied during the cooling operation is less than the flow rate of purge gas supplied after the cooling operation is completed (i.e., the heating process and / or discharge process).

[0068] The flow rate of the purge gas continuously supplied during the cooling operation may be, for example, less than half or less than one-tenth of the flow rate of the purge gas supplied after the cooling operation has finished. The flow rate of the purge gas continuously supplied during the cooling operation may be, for example, within approximately 3 liters per minute, within approximately 2 liters per minute, or within approximately 1 liter per minute under standard conditions (e.g., 0°C and 1 atm). In this way, it is expected that the temperature rise of the cryopanel 38 caused by the purge gas supplied to the cryopump vessel 16 through the body purge valve 20 can be made sufficiently small for practical use.

[0069] Even when purge gas is continuously supplied to the cryopump container 16, the measured temperature T2 of the cryopump container 38 may be monitored, similar to S26 in Figure 4. That is, the controller 46 may acquire the measured temperature T2 of the cryopump container 38 using the second temperature sensor 42 and compare the measured temperature T2 with a cryogenic temperature threshold Ts. The controller 46 controls the body purge valve 20 so that purge gas is supplied when the measured temperature T2 falls below the cryogenic temperature threshold Ts. On the other hand, if the measured temperature T2 is above the temperature threshold Ts, the controller 46 controls the body purge valve 20 to interrupt the supply of purge gas. In this way, after confirming that the measured temperature T2 of the cryopump container 38 is below the temperature threshold Ts, the body purge valve 20 can be opened and purge gas can be supplied to the cryopump container 16. If the measured temperature T2 of the cryopump container 38 is higher than the temperature threshold Ts, the body purge valve 20 can be closed and the controller can wait until the measured temperature T2 falls below the temperature threshold Ts.

[0070] Furthermore, the purge gas source 48 may have a function to adjust the purge gas flow rate, thereby adjusting the flow rate of the body purge supplied to the cryopump vessel 16. In this case, instead of adjusting the body purge flow rate using the body purge valve 20, the controller 46 may control the purge gas source 48 to obtain the desired purge gas flow rate.

[0071] Figure 5 is a flowchart illustrating an exemplary cryopump regeneration method according to an embodiment. The cryopump regeneration method comprises supplying a first diluent gas to the cryopump 10 while discharging a mixed gas of the gas revaporized in the cryopump 10 and the first diluent gas from the cryopump 10 (S30), and diluting the discharged mixed gas with a second diluent gas while discharging the mixed gas from the cryopump 10 (S32). Although both steps (S30 and S32) are performed in spatially different locations (S30 at the body purge valve 20 and the cryopump container 16, and S32 at the discharge valve 22), they occur simultaneously in time.

[0072] In this way, even if a hazardous gas is stored in the cryopump 10, it is first diluted by the first diluent gas within the cryopump 10, and at the same time, the mixture of the hazardous gas discharged from the cryopump 10 and the first diluent gas is diluted by the second diluent gas. This two-stage dilution suppresses the concentration of hazardous gas discharged from the cryopump 10 during its regeneration.

[0073] The dilution discharge treatment (S30, S32) shown in Figure 5 is performed in the initial stage of regeneration. The dilution discharge treatment (S30, S32) may also be performed after the cooling operation of the refrigerator 14 is completed, i.e., in the heating process (S12, S13 in Figure 3). Therefore, the dilution discharge treatment (S30, S32) may be performed together with the purge gas pre-introduction treatment described above (i.e., after the purge gas pre-introduction treatment). After the dilution discharge treatment, the discharge process (S14 in Figure 3) and the cool-down process (S15) described above may be performed.

[0074] The first dilution gas may be a purge gas supplied from the body purge valve 20 to the cryopump container 16, and the second dilution gas may be a purge gas supplied from the discharge purge valve 24 to the discharge line 50.

[0075] In the exemplary operation of the body purge valve 20, the body purge valve 20 may remain open while the discharge valve 22 is closed, because if the discharge valve 22 is closed, no discharge occurs from the cryopump container 16 to the discharge line 50. The body purge valve 20 may repeatedly open and close while the discharge valve 22 is open. The proportion of the open time in the opening and closing cycle of the body purge valve 20 may be constant. Alternatively, the proportion of the open time in the opening and closing cycle of the body purge valve 20 may change over time. For example, as the concentration of hazardous gas in the cryopump container 16 decreases over time due to discharge, the proportion of the open time in the opening and closing cycle of the body purge valve 20 may increase over time, and eventually the body purge valve 20 may remain open continuously.

[0076] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. Various features described in relation to one embodiment are applicable to other embodiments. New embodiments resulting from combinations will possess the combined effects of each of the embodiments combined.

[0077] In the above-described embodiment, the diluent gas (e.g., first diluent gas) is supplied to the cryopump container 16 from the body purge valve 20. However, in some embodiments, other diluent gas sources may be used. For example, the diluent gas may be supplied to the cryopump container 16 from the vacuum chamber 100 of a vacuum processing apparatus in which the cryopump 10 is installed, through the gate valve 102 and the cryopump intake port 17. Since vacuum processing apparatuses typically have a gas source that supplies, for example, argon gas or other inert gases to the vacuum chamber 100, these may be used as the diluent gas.

[0078] Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate one aspect of the principle and application of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, as long as they do not depart from the spirit of the present invention as defined in the claims. [Explanation of Symbols]

[0079] 10 cryopumps, 14 chillers, 16 cryopump vessels, 20 body purge valves, 24 discharge purge valves, 38 cryopanels, 46 controllers, 50 discharge lines.

Claims

1. Cryopump container and A cryopump container is provided with a cryopanel, A refrigerator installed in the cryopump vessel and thermally coupled to the cryopanel, the refrigerator performing a cooling operation to cool the cryopanel to an extremely low temperature in which the purge gas condenses on the cryopanel, A body purge valve that supplies the purge gas to the cryopump container, A cryopump comprising: a regeneration controller configured to control the body purge valve so that the purge gas is supplied to the cryopump container and condensed on the cryopump during the cooling operation of the refrigerator that cools the cryopanel.

2. The cryopump according to claim 1, characterized in that the regeneration controller is configured to control the body purge valve so that purge gas is intermittently supplied to the cryopump vessel during the cooling operation of the refrigerator.

3. The regeneration controller is further configured to control the body purge valve so that purge gas is supplied to the cryopump vessel even after the cooling operation of the refrigerator has finished. The cryopump according to claim 1, characterized in that the flow rate of the purge gas supplied during the cooling operation is less than the flow rate of the purge gas supplied after the cooling operation is completed.

4. The cryopump according to claim 1, characterized in that the regeneration controller is configured to control the refrigerator so that when purge gas is supplied, the refrigerator's cooling capacity is increased compared to before the supply of purge gas.

5. The system further includes a temperature sensor for measuring the temperature of the cryopanel, The aforementioned playback controller, The temperature measured by the temperature sensor of the cryopanel is acquired, The measured temperature is compared with a cryogenic temperature threshold, The cryopump according to claim 1, characterized in that it is configured to control the body purge valve so that a purge gas is supplied when the measured temperature falls below the cryogenic temperature threshold.

6. The cryopump according to any one of claims 1 to 5, characterized in that the regeneration controller is configured to perform the cooling operation before the heating step in the regeneration of the cryopump.

7. The cooling operation of the cryopump refrigerator is performed such that the cryogenic surface is cooled to an extremely low temperature in which the dilution gas condenses on the cryogenic surface inside the cryopump, The dilution gas is supplied to the cryopump during the cooling operation of the cryopump's refrigerator, The dilution gas is accumulated on the cryogenic surface within the cryopump, The other gases trapped on the cryogenic surface are re-vaporized together with the diluent gas, A cryopump regeneration method characterized by comprising: discharging a mixed gas of the re-vaporized gas and the diluent gas from the cryopump.

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