Cryogenic pump and cryogenic pump regeneration method

Abstract

The present invention provides a cryopump capable of removing organic matter attached to a cryopanel. The cryopump (10) comprises: an ultra-low temperature surface such as at least one cryopanel (38), on which a photocatalyst layer (50) is provided; and an excitation light source (60) configured to irradiate the photocatalyst layer (50) with excitation light (62) for activating the photocatalyst layer (50). The photocatalyst layer (50) contains a visible light responsive photocatalyst material, and the excitation light source (60) can emit light in a visible light wavelength region that activates the visible light responsive photocatalyst material as the excitation light (62).

Description

[0001] This application claims priority based on Japanese Patent Application No. 2020-187235 filed on November 10, 2020. The entire contents of the Japanese Patent Application are incorporated herein by reference. Technical Field

[0002] The invention relates to a cryogenic pump and a cryogenic pump regeneration method. Background Art

[0003] A cryopump is a vacuum pump that captures gas molecules on a cryopanel cooled to an ultra-low temperature by condensation or adsorption and then discharges them. Generally, cryopumps are used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes, etc. Since cryopumps are so-called gas capture vacuum pumps, they need to be regenerated regularly to discharge the captured gas to the outside.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-79823

[0005] During the vacuum exhaust operation, various chemical substances will flow into the cryopump as gases from the semiconductor manufacturing equipment, and such gases include, for example, vapors of organic substances such as organic solvents used in the photoresist coated on the wafer and various surface treatments of the wafer. The gas will adhere to the cryopanel through condensation, which may contaminate the cryopanel. Once such organic attachments are attached to the cryopanel, it is difficult to easily discharge them from the cryopanel through the existing cryopanel regeneration method, and they will gradually accumulate on the cryopanel. If the attachments exist between the cryopanel and the ice layer such as water or argon accumulated on the cryopanel, the adhesion between the ice layer and the cryopanel will decrease, causing the ice layer to easily break on the cryopanel or peel off from the cryopanel. The rupture and peeling of the ice layer will cause a gap between the ice layer and the cryopanel, thereby hindering good thermal contact between the two. As a result, the cooling of the ice layer by the cryopanel is weakened, which may cause the temperature of the ice layer to rise and the vapor pressure in the cryopanel to rise. As a result, the exhaust performance of the cryopanel may eventually decrease. Summary of the invention

[0006] One of the exemplary objects of one embodiment of the present invention is to provide a cryopump capable of removing organic matter attached to a cryopanel.

[0007] According to one embodiment of the present invention, a cryopump includes: at least one cryopanel having a photocatalyst layer on a surface thereof; and an excitation light source arranged to irradiate the photocatalyst layer with excitation light for activating the photocatalyst layer.

[0008] According to one embodiment of the present invention, a cryopump comprises: at least one cryopanel having a photocatalyst layer on its surface; and a cryopump container having a window for inputting excitation light for activating the photocatalyst layer, and the cryopump container accommodates the cryopanel.

[0009] According to one embodiment of the present invention, a cryopump regeneration method comprises the following steps: irradiating a photocatalyst layer on a cryopanel with excitation light to activate a photocatalyst; and decomposing organic matter attached to the photocatalyst layer by irradiation with the excitation light to remove the organic matter from the cryopanel.

[0010] In addition, any combination of the above-mentioned constituent elements or any form of substitution of constituent elements or expressions of the present invention in the form of methods, apparatuses, systems, etc. may also be practiced as additional embodiments of the present invention.

[0011] According to the present invention, a cryopump capable of removing organic matter adhering to a cryopanel is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A cryopump according to an embodiment is schematically shown.

[0013] Figure 2 1 is a flowchart showing a method for regenerating a cryopump according to an embodiment.

[0014] Figure 3 Another example of the cryopump according to the embodiment is schematically shown.

[0015] In the figure: 10 - cryopump, 16 - cryopump container, 36 - radiation shielding, 37 - inlet cryopanel, 38 - cryopanel, 50 - photocatalyst layer, 60 - excitation light source, 62 - excitation light, 70 - window. DETAILED DESCRIPTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, identical or equivalent components, parts and processes are marked with the same symbols, and repeated descriptions are appropriately omitted. For ease of description, in each of the accompanying drawings, the proportions and shapes of each part are appropriately set, and unless otherwise specified, they are not interpreted as limiting. The embodiments are examples and do not limit the scope of the present invention in any way. All features or combinations thereof described in the embodiments are not necessarily the essence of the invention.

[0017] Figure 1 The cryopump 10 according to the embodiment is schematically shown. The cryopump 10 is installed in a vacuum chamber of, for example, an ion implantation device, a sputtering device, an evaporation device, or other vacuum processing device, and is used to increase the vacuum degree inside the vacuum chamber to a level required for a desired vacuum process. -5 Pa to 10 -8 High vacuum degree of about Pa.

[0018] The cryopump 10 includes a compressor 12, a refrigerator 14, and a cryopump housing 16. The cryopump housing 16 has a cryopump air intake port 17. The cryopump 10 also includes a roughing valve 18, a purge valve 20, a vent valve 22, and a switching control valve 24, which are provided on the cryopump housing 16. The cryopump 10 also includes a radiation shield 36 and at least one cryopanel 38 accommodated in the cryopump housing 16.

[0019] The compressor 12 is configured to recover refrigerant gas from the refrigerator 14 and to supply the recovered refrigerant gas to the refrigerator 14 after increasing the pressure. The refrigerator 14 is also called an expander or a cold head, and together with the compressor 12, it constitutes an ultra-low temperature refrigerator. The circulation of the refrigerant gas between the compressor 12 and the refrigerator 14 is accompanied by appropriate pressure changes and volume changes of the refrigerant gas in the refrigerator 14, thereby constituting a thermodynamic cycle that produces coldness, and the refrigerator 14 can provide ultra-low temperature cooling. The refrigerant gas is usually helium, but other suitable gases can also be used. For ease of understanding, Figure 1 Arrows are used to indicate the flow direction of the refrigerant gas. As an example, the cryogenic refrigerator is a two-stage Gifford-McMahon (GM) refrigerator, but it can also be a pulse tube refrigerator, a Stirling refrigerator or other types of cryogenic refrigerators.

[0020] The refrigerator 14 includes a room temperature portion 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 to cool 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 to 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 referred to as a high temperature cooling stage and a low temperature cooling stage, respectively.

[0021] 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, 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 sequentially arranged in a straight line.

[0022] In the case where the refrigerator 14 is a two-stage GM refrigerator, a first displacer and a second displacer (not shown) are respectively arranged inside the first cylinder 28 and the second cylinder 32 in a manner that allows them to reciprocate. A first cold storage device and a second cold storage device (not shown) are respectively assembled in the first displacer and the second displacer. In addition, the room temperature section 26 has a driving mechanism (not shown) such as a motor for reciprocating the first displacer and the second displacer. The driving mechanism includes a flow path switching mechanism that switches the flow path of the working gas so as to periodically repeat the supply of working gas (e.g., helium) to the inside of the refrigerator 14 and the discharge of working gas from the inside of the refrigerator 14.

[0023] The cryopump container 16 has a container body 16a and a refrigerator housing tube 16b. The cryopump container 16 is a vacuum container designed to maintain vacuum during the vacuum exhaust operation of the cryopump 10 and to withstand the pressure of the surrounding environment (e.g., atmospheric pressure). The container body 16a has a cylindrical shape having a cryopump air intake port 17 at one end thereof and the other end being closed. The radiation shield 36 is housed in the container body 16a, and the second cooling stage 34 and the cryopanel 38 are housed together in the radiation shield 36. One end of the refrigerator housing tube 16b is connected to the container body 16a, and the other end is fixed to the room temperature portion 26 of the refrigerator 14. The refrigerator 14 is inserted into the refrigerator housing tube 16b, and the first cylinder 28 is housed.

[0024] In this embodiment, the cryopump 10 is a so-called horizontal cryopump in which a refrigerator 14 is arranged on the side of a container body 16a. A refrigerator insertion port is provided on the side of the container body 16a, and a refrigerator receiving tube 16b is connected to the side of the container body 16a at the refrigerator insertion port. Similarly, a hole for passing the refrigerator 14 is also provided on the side of the radiation shield 36 adjacent to the refrigerator insertion port of the container body 16a. 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 connected to the first cooling stage 30 around the hole on its side.

[0025] The cryopump can be set in various postures at the site of use. As an example, the cryopump 10 can be set in the horizontal posture shown in the figure (i.e., the posture with the cryopump air intake port 17 facing upward). In this case, the bottom of the container body 16a is located below the cryopump air intake port 17, and the refrigerator 14 extends in the horizontal direction.

[0026] The radiation shield 36 is thermally connected to the first cooling stage 30 and is therefore cooled to the first cooling temperature, thereby providing an ultra-low temperature surface that protects the cryopanel 38 from radiant heat from the outside of the cryopump 10 or the cryopump container 16. The radiation shield 36 has a cylindrical shape, for example, that surrounds the cryopanel 38 and the second cooling stage 34. The end of the radiation shield 36 on the side of the cryopump air intake port 17 is open, allowing gas to enter the radiation shield 36 from the outside of the cryopump 10 through the cryopump air intake port 17. The end of the radiation shield 36 on the opposite side of the cryopump air intake port 17 can be closed, or can have an opening, or can be open. There is a gap between the radiation shield 36 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.

[0027] An inlet cryopanel 37 fixed to the open end of the radiation shield 36 may be provided at the cryopump air inlet 17. The inlet cryopanel 37 is cooled to the same temperature as the radiation shield 36 so that the so-called Class 1 gas (gas that condenses at a relatively high temperature, such as water vapor) can be condensed on its surface. The inlet cryopanel 37 is, for example, a shutter or a baffle, but may also be a plate or component, such as a circular or other shape, configured to occupy a portion of the cryopump air inlet 17.

[0028] The cryopanel 38 is thermally connected to the second cooling stage 34, and is therefore cooled to the second cooling temperature, thereby providing an ultra-low temperature surface for condensing the second type of gas (e.g., argon, nitrogen, etc., which condenses at a relatively low temperature). The cryopanel 38 may have a plate-like or umbrella-like shape, for example, and may be arranged so that its upper surface faces the cryopump air intake port 17. Figure 1 As shown, a plurality of cryopanels 38 may be provided, and these cryopanels 38 may be arranged from the cryopump air inlet 17 toward the bottom of the radiation shield 36. In addition, in order to adsorb the third type of gas (for example, non-condensable gas such as hydrogen), activated carbon or other adsorbent materials are disposed on at least a portion of the surface of the cryopanel 38 (for example, the surface on the opposite side of the cryopump air inlet 17). The gas entering the radiation shield 36 from the outside of the cryopump 10 through the cryopump air inlet 17 is captured by the cryopanel 38 by condensation or adsorption.

[0029] The radiation shield 36 and the inlet cryopanel 37 cooled to the first cooling temperature may be collectively referred to as a high-temperature cryopanel. The cryopanel 38 is cooled to a second cooling temperature lower than the first cooling temperature, and therefore may be referred to as a low-temperature cryopanel. As for the configuration and shape of the radiation shield 36 and the cryopanel 38, various known structures may be appropriately adopted, and therefore will not be described in detail here.

[0030] A photocatalyst layer 50 is provided on at least a portion of the surface of the cryopanel 38. The photocatalyst layer 50 may be, for example, a coating layer containing particles of a photocatalyst material. The configuration of the photocatalyst layer 50 is not particularly limited. Figure 1 As shown, the photocatalyst layer 50 can be provided on the low-temperature cryopanel, for example, it can be formed on at least a portion of the upper surface (the surface on the side of the cryopanel air inlet 17) of the cryopanel 38 closest to the cryopump air inlet 17. The photocatalyst layer 50 can also be formed on at least a portion of the lower surface of the uppermost cryopanel 38, or can also be formed on at least a portion of the surface of another cryopanel 38.

[0031] As described above, when an adsorption material is disposed on at least a portion of the surface of the cryopanel 38 to form an adsorption region, the photocatalyst layer 50 can be disposed on a portion of the cryopanel 38 that avoids the adsorption region. That is, the photocatalyst layer 50 can be formed on at least a portion of the region other than the adsorption region on the cryopanel 38. Typically, the adsorption material is bonded to the cryopanel 38 using a binder. By not arranging the photocatalyst layer 50 in the adsorption region, it is possible to prevent the photocatalyst layer 50 from acting on the binder and causing it to deteriorate.

[0032] The photocatalyst layer 50 may also be formed on other parts cooled to the second cooling temperature (for example, at least a portion of the outer surface of the second cooling stage 34 of the refrigerator 14 ). The photocatalyst layer 50 may also be formed on at least a portion of the outer surface of the second cylinder 32 .

[0033] The photocatalyst layer 50 may also be provided on a high temperature cryopanel, for example, may be formed on at least a portion of the surface of the inlet cryopanel 37. The photocatalyst layer 50 may also be formed on at least a portion of the surface (e.g., the inner surface) of the radiation shield 36. If necessary, the photocatalyst layer 50 may also be formed on at least a portion of the outer surface of the first cooling stage 30 and the first cylinder 28 of the refrigerator 14. The photocatalyst layer 50 may also be formed on at least a portion of the inner surface of the cryopump container 16.

[0034] The photocatalyst layer 50 may contain an ultraviolet light-responsive photocatalyst material that exhibits a photocatalytic effect under ultraviolet light irradiation, such as titanium oxide.

[0035] However, in recent years, visible light responsive photocatalyst materials that can exhibit photocatalytic effects under visible light irradiation have been discovered. Therefore, the photocatalyst layer 50 may also contain a visible light responsive photocatalyst material instead of an ultraviolet light responsive photocatalyst material. As visible light responsive photocatalyst materials, for example, iron-based compound-modified titanium oxide, copper-based compound-modified titanium oxide, copper-based compound-modified tungsten oxide, etc. are known.

[0036] Furthermore, the cryopump 10 includes an excitation light source 60 for irradiating the photocatalyst layer 50 with an excitation light 62 for activating the photocatalyst layer 50. The excitation light source 60 is disposed in the cryopump container 16 in such a manner as to irradiate the excitation light 62 toward the inside of the cryopump container 16. For example, the excitation light source 60 may be disposed in the container body 16a of the cryopump container 16 in such a manner as to irradiate the excitation light 62 toward the space between the cryopump air intake port 17 and the cryopanel 38. An opening 36a for allowing the excitation light 62 irradiated from the excitation light source 60 toward the inside of the cryopump container 16 to pass may be formed on the radiation shield 36. As long as the excitation light 62 can be irradiated to the photocatalyst layer 50, the configuration of the excitation light source 60 is not particularly limited. Furthermore, a plurality of excitation light sources 60 may also be provided.

[0037] When the photocatalyst layer 50 contains a visible light responsive photocatalyst material, the excitation light source 60 is configured to emit light including a visible light wavelength region that activates the visible light responsive photocatalyst material as the excitation light 62. When the photocatalyst layer 50 contains an ultraviolet light responsive photocatalyst material, the excitation light source 60 is configured to emit ultraviolet light that activates the ultraviolet light responsive photocatalyst material as the excitation light 62.

[0038] When the excitation light source 60 emits ultraviolet light, there is a risk that the adhesive bonding the adsorbent to the cryopanel 38 will deteriorate over a long period of time. The excitation light source 60 of visible light can reduce this risk and is easy to handle.

[0039] The excitation light source 60 may also be configured to emit infrared light. For example, the excitation light source 60 may include a broadband light source (such as a halogen lamp) that emits the excitation light 62 and infrared light. Alternatively, the excitation light source 60 may include a first light emitting element that emits the excitation light 62 and a second light emitting element that emits infrared light, and the light emitting element may be, for example, an LED. Thus, the excitation light source 60 can heat the irradiated object such as the cryopanel 38 during the regeneration period of the cryopump 10 using infrared light.

[0040] 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 mounted on the first cooling stage 30. The second temperature sensor 42 is mounted on the second cooling stage 34. 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 can be provided, for example, in the refrigerator housing tube 16b to measure the internal pressure of the cryopump container 16 and output a measured pressure signal indicating the measured pressure.

[0041] Furthermore, the cryopump 10 further includes a controller 46 for controlling the cryopump 10. The controller 46 may be provided integrally with the cryopump 10, or may be configured as a control device separate from the cryopump 10.

[0042] 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 may be connected to the second temperature sensor 42 to receive a second measured temperature signal from the second temperature sensor 42. The controller 46 may be connected to the pressure sensor 44 to receive a measured pressure signal from the pressure sensor 44.

[0043] During the vacuum exhaust operation of the cryopump 10, the controller 46 may control the refrigerator 14 according to the cooling temperature of the radiation shield 36 and / or the cryopanel 38. Furthermore, during the regeneration operation of the cryopump 10, the controller 46 may control the refrigerator 14, the roughing valve 18, the purge valve 20, the vent valve 22, and the excitation light source 60 according to the pressure in the cryopump housing 16 (or, as required, according to the temperature of the cryopanel 38 and the pressure in the cryopump housing 16).

[0044] The roughing valve 18 is provided on the cryopump container 16 (for example, the refrigerator housing cylinder 16b). The roughing valve 18 is connected to a roughing pump (not shown) provided outside the cryopump 10. The roughing pump is a vacuum pump for vacuuming the cryopump 10 to its operation start pressure. When the roughing valve 18 is opened by the control of the controller 46, the cryopump container 16 is connected to the roughing pump, and when the roughing valve 18 is closed, the cryopump container 16 is disconnected from the roughing pump. If the roughing valve 18 is opened and the roughing pump is operated, the cryopump 10 can be depressurized.

[0045] The purge valve 20 is disposed on the cryopump container 16 (for example, the container body 16a). The purge valve 20 is connected to a purge gas supply device (not shown) disposed outside the cryopump 10. When the purge valve 20 is opened by the control of the controller 46, the purge gas is supplied to the cryopump container 16, and when the purge valve 20 is closed, the supply of the purge gas to the cryopump container 16 is cut off. The purge gas can be, for example, nitrogen or other dry gases, and the temperature of the purge gas can be, for example, adjusted to room temperature or heated to a temperature higher than room temperature. By opening the purge valve 20 to introduce the purge gas into the cryopump container 16, the cryopump 10 can be pressurized. In addition, the cryopump 10 can be heated from an ultra-low temperature to room temperature or a temperature higher than room temperature.

[0046] The vent valve 22 is disposed on the cryopump container 16 (e.g., the refrigerator housing cylinder 16b). The purpose of providing the vent valve 22 is to discharge fluid from the interior of the cryopump 10 to the outside. The vent valve 22 can be connected to a storage tank (not shown) outside the cryopump 10 that receives the discharged fluid. Alternatively, in the case where the discharged fluid is harmless, the vent valve 22 can also be configured to release the discharged fluid directly into the surrounding environment. The fluid discharged from the vent valve 22 is basically a gas, but can be a liquid or a gas-liquid mixture.

[0047] The vent valve 22 opens and closes according to a command signal input from the controller 46. For example, when the fluid is released from the cryopump container 16 during regeneration, the controller 46 opens the vent valve 22. When the fluid should not be released, the controller 46 closes the vent valve 22. The vent valve 22 can be, for example, a normally closed control valve. Furthermore, the vent valve 22 is configured to also function as a so-called safety valve that opens mechanically based on a specified pressure difference. Therefore, when the inside of the cryopump becomes high pressure for some reason, the vent valve 22 does not need to be controlled and is mechanically opened. In this way, the internal high pressure can be released.

[0048] The internal structure of the controller 46 can be realized by components or circuits represented by a CPU or memory of a computer in terms of hardware structure, and can be realized by computer programs, etc. in terms of software structure, but in the figure, it is appropriately depicted as a functional block realized by their cooperation. It should be understood by those skilled in the art that these functional blocks can be realized in various forms by combining hardware and software.

[0049] For example, the controller 46 may be implemented by a combination of a processor (hardware) such as a CPU (Central Processing Unit) or a microcomputer and a software program executed by the processor (hardware). The software program may be a computer program for causing the controller 46 to execute regeneration of the cryopump 10 .

[0050] Figure 2 1 is a flowchart showing a regeneration method of the cryopump 10 according to the embodiment. The regeneration sequence of the cryopump 10 according to the embodiment includes a heating step (S10), a discharge step (S40) and a cooling step (S60) similar to the conventional cryopump regeneration, and further includes steps (S20, S30, S50) of decomposing and removing organic attachments using the photocatalyst layer 50 and the excitation light 62. The regeneration sequence is executed by the controller 46.

[0051] In the temperature raising step (S10), the cryopump 10 is heated from ultra-low temperature to room temperature or a higher regeneration temperature (e.g., about 290K to about 300K) by using a purge gas supplied to the cryopump housing 16 via the purge valve 20 or other heating means. The temperature raising of the cryopump 10 may also be performed by, for example, reverse temperature raising by the refrigerator 14, and when an electric heater is provided on the cryopump 10, the electric heater may also be used. Thus, the gas captured by the cryopanel 38 is re-gasified.

[0052] The excitation light source 60 is turned on (S20). The excitation light source 60 emits excitation light 62, which is irradiated to the photocatalyst layer 50 on the cryopanel 38 or other parts in the cryopump 10 (for example, the inlet cryopanel 37, the cryopanel 38). As a result, the photocatalyst layer 50 can exhibit a photocatalytic effect.

[0053] Furthermore, when the excitation light source 60 is capable of emitting infrared light, ultra-low temperature surfaces such as the cryopanel 38 can be heated by irradiation with infrared light. In the heating based on the reverse heating of the refrigerator 14, the parts where the heat transfer distance from the refrigerator 14 becomes longer (for example, the end of the cryopanel 38, the inlet cryopanel 37, etc.) are not easily heated compared to the parts close to the refrigerator 14, but the heating based on infrared light irradiation can make up for this. Furthermore, in the heating based on the electric heater, if the thermal contact between the heater and the heating object is not sufficient, the heater may overheat, but it can be considered that this risk is very small in the heating based on infrared light irradiation. Therefore, heating based on infrared light irradiation may be more effective than other heating mechanisms.

[0054] The excitation light source 60 may be turned on at the same time as the start of the heating process, during the heating process, or after the heating process is completed. When the excitation light source 60 is used as one of the heating mechanisms, in order to shorten the heating time, the excitation light source 60 is turned on at the same time as the start of the heating process or during the heating process, and is preferably used in conjunction with other heating mechanisms.

[0055] The organic matter attached to the photocatalyst layer 50 is decomposed under the irradiation of the excitation light 62 and is removed from the cryopanel 38 (S30). The organic attachment is an attachment that flows into the cryopump container 16 from the vacuum chamber of the vacuum processing device equipped with the cryopump 10 together with other exhausted gases (such as water or argon gas) and accumulates on the cryopanel 38, for example, from the photoresist coated on the wafer or the organic chemical substances used in various surface treatments of the wafer. Such organic attachment is almost or completely non-volatile at the above-mentioned regeneration temperature, so it cannot be removed from the cryopanel 38 by simply raising the temperature to the regeneration temperature.

[0056] Under the irradiation of the excitation light 62, the organic matter is decomposed into carbon dioxide and water based on the photocatalytic action of the photocatalyst layer 50. Carbon dioxide and water can be discharged from the cryopump container 16 as gas through the vent valve 22 or the roughing valve 18. If the photocatalyst layer 50 is provided at other locations in the cryopump 10, such as the inlet cryopanel 37, the organic matter attached to the photocatalyst layer 50 at that location can also be decomposed and removed. As long as the excitation light 62 is irradiated, the decomposition and removal process of the organic attachment can be generated in both the heating process and the discharge process.

[0057] In the exhaust process (S40), the gas is exhausted to the outside from the cryopump container 16 through the vent valve 22 or the roughing valve 18. In the exhaust process, so-called roughing and purging can be performed. Roughing and purging refer to: by alternately and repeatedly performing roughing of the cryopump container 16 based on the roughing valve 18 and supplying purge gas to the cryopump container 16 based on the purge valve 20, the gas remaining in the cryopump container 16 (for example, the gas (for example, water vapor, etc.) adsorbed by the adsorbent material (for example, activated carbon, etc.) on the cryopanel 38) is exhausted from the cryopump container 16.

[0058] The pressure rise rate test is used to determine whether the discharge process is completed. The pressure rise rate test is also called the RoR (Rate of Rise) test. In the pressure rise rate test, the pressure rise from the reference pressure when the cryopump container 16 is kept in vacuum for a specified time is detected. If the pressure rise is less than the threshold, it is judged as qualified, and if it is above the threshold, it is judged as unqualified. In order to keep the cryopump container 16 in vacuum, all valves provided in the cryopump 10 are closed.

[0059] The excitation light source 60 is turned off (S50). The excitation light source 60 can be turned off at any time during the regeneration of the cryopump 10. When the excitation light source 60 is used as one of the heating mechanisms, the excitation light source 60 is turned off before starting the cooling process so as not to hinder the cooling.

[0060] In the temperature reduction step ( S60 ), the cryopump 10 is cooled down from the regeneration temperature to a very low temperature. The regeneration is completed in this way, and the cryopump 10 can resume the vacuum pumping operation.

[0061] As mentioned at the beginning of this specification, if the ultra-low temperature surface of the cryopanel 38, etc. is contaminated by organic attachments and the organic attachments exist between the ultra-low temperature surface and the ice layer such as water or argon condensed on the ultra-low temperature surface, the adhesion between the ice layer and the ultra-low temperature surface will decrease, causing the ice layer to easily break or peel off. The rupture or peeling of the ice layer will hinder the good thermal contact between the ice layer and the ultra-low temperature surface, and as a result, it may cause the temperature of the ice layer to rise and the vapor pressure in the cryopump container to rise. As a result, the exhaust performance of the cryopump may eventually decrease. For example, in a vacuum processing device equipped with a cryopump, it is required to restore the vacuum degree temporarily dropped when replacing the processed wafer and the unprocessed wafer to the target vacuum degree within a desired time. However, if the organic matter attached to the ultra-low temperature surface is not removed, the time required to restore the vacuum degree will be extended, and in the worst case, it may not be able to be restored to the target vacuum degree.

[0062] In the past, contaminated cryogenic surfaces had to be disassembled from the cryopump and cleaned during cryopump maintenance. If the cleaned cryopanel can be reused, it needs to be reassembled and used. If it cannot be reused, it is scrapped and replaced with a new cryopanel. In either case, this maintenance is time-consuming and laborious.

[0063] In contrast, according to the embodiment, in the cryopump 10, by irradiating the photocatalyst layer 50 provided on the surface of the low-temperature cryopanel (or high-temperature cryopanel) with the excitation light 62 from the excitation light source 60, the organic matter attached to the cryopanel can be decomposed and removed. Thus, the above-mentioned problem can be alleviated or eliminated. For example, it is possible to suppress the deterioration of the exhaust performance of the cryopump 10 caused by organic matter contamination.

[0064] Furthermore, in most cases, organic deposits are harmful substances. If the organic deposits are directly discharged from the cryopump 10, the organic deposits may re-adhere to the roughing valve 18, the vent valve 22, or even the discharge path further downstream to cause adverse effects. However, according to the embodiment, the organic deposits can be decomposed into water and carbon dioxide to make them harmless, so that this risk can be alleviated or eliminated.

[0065] Figure 3 Another example of the cryopump 10 according to the embodiment is schematically shown. Figure 3 The cryopump 10 shown in the figure has a window 70 instead of the excitation light source 60. The other structures are similar to those of FIG. Figure 1The cryopump 10 shown in the figure is the same. A window 70 is provided in the cryopump container 16 so as to input excitation light 62 from the outside to activate the photocatalyst layer 50. The window 70 may be, for example, a viewing window provided in the container body 16a. In this way, the excitation light 62 can be input from the window 70 and the photocatalyst layer 50 can be irradiated with the excitation light 62, so that organic matter attached to the low-temperature cryopanel (or high-temperature cryopanel) can be decomposed and removed. In addition, in one embodiment, the cryopump 10 may also have both the excitation light source 60 and the window 70.

[0066] The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and various design changes and variations are possible, and these variations are also included in the scope of the present invention.

Claims

1. A cryogenic pump, characterized in that: have: a cryopump container having a cryopump air intake port; a high-temperature cryopanel, housed in the cryopump housing and cooled to a first cooling temperature; a low-temperature cryopanel surrounded by the high-temperature cryopanel and cooled to a second cooling temperature lower than the first cooling temperature; a photocatalyst layer located on a surface of at least one of the high-temperature cryopanel and the low-temperature cryopanel; and The excitation light source is arranged to irradiate the photocatalyst layer with excitation light for activating the photocatalyst layer in a space between the cryopump air intake port and the low-temperature cryopanel.

2. The cryopump according to claim 1, characterized in that The photocatalyst layer contains a visible light responsive photocatalyst material, and the excitation light source emits light including a visible light wavelength region that activates the visible light responsive photocatalyst material as the excitation light.

3. The cryopump according to claim 1 or 2, characterized in that: The excitation light source emits infrared light.

4. The cryopump according to claim 1 or 2, characterized in that: The photocatalyst layers are respectively disposed on the high-temperature cryopanel and the low-temperature cryopanel.

5. A cryopump, characterized in that: have: a cryopump container having a cryopump air intake port; a high-temperature cryopanel, housed in the cryopump housing and cooled to a first cooling temperature; a low-temperature cryopanel surrounded by the high-temperature cryopanel and cooled to a second cooling temperature lower than the first cooling temperature; A photocatalyst layer is located on the surface of at least one of the high-temperature cryopanel and the low-temperature cryopanel; and The window is used to input excitation light for activating the photocatalyst layer into the space between the cryopump air intake port and the low-temperature cryopanel.

6. A cryopump regeneration method, characterized in that: The following steps are required: Start the cryopump regeneration sequence; During the regeneration, the photocatalyst layer on the cryopanel is irradiated with excitation light for activating the photocatalyst layer; and By irradiation with the excitation light, organic matter adhering to the photocatalyst layer is decomposed and removed from the cryopanel.

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