Cryogenic pump

Abstract

The present invention relates to a cryopump capable of suppressing an influence on exhaust velocity and improving adsorption capacity. A cryopump (10) includes a radiation shield (30) thermally connected to a first cooling stage (22) of a refrigerator (14) and extending in an axial direction from a cryopump suction port (12) into a cryopump vessel (16), and a plurality of cryopanels thermally connected to a second cooling stage (24) of the refrigerator (14) and arranged in the axial direction inside the radiation shield (30). The plurality of cryopanels includes a top cryopanel (41) closest to the cryopump suction port (12) in the axial direction, and at least one cryopanel arranged in the axial direction apart from the top cryopanel (41) by a space. The top cryopanel (41) has an opening portion (46) allowing gas to pass through the space between the top cryopanel (41) and the at least one cryopanel.

Description

[0001] This application claims priority to Japanese Patent Application No. 2025-063571, filed on April 8, 2025. The entire contents of that Japanese application are incorporated herein by reference. Technical Field

[0002] This invention relates to a cryogenic pump. Background Technology

[0003] A cryogenic pump is a vacuum pump that captures gas molecules onto a cryogenic plate cooled to ultra-low temperatures through condensation or adsorption, and then exhausts the gas. Cryogenic pumps are commonly used to achieve the clean vacuum environment required for processes such as semiconductor circuit manufacturing.

[0004] Patent Document 1: Japanese Patent Application Publication No. 4-103885 Key performance indicators of cryogenic pumps include exhaust velocity and adsorption capacity. These depend on the design of the cryogenic plate and are interconnected. Changes in the performance indicators of the cryogenic pump due to design modifications can also affect the vacuum treatment that should be discharged by the cryogenic pump. For example, if the cryogenic plate design is changed to increase the adsorption capacity, the exhaust velocity will also change, which may affect the vacuum treatment. As a result, sometimes the outcome is less than ideal, requiring a redesign of the vacuum treatment. To avoid this, it is desirable to minimize the impact of cryogenic pump design changes on the vacuum treatment. Summary of the Invention

[0005] One exemplary objective of one embodiment of the present invention is to provide a cryogenic pump that can suppress the influence on the exhaust velocity while improving the adsorption capacity of the cryogenic pump.

[0006] According to one embodiment of the present invention, a cryogenic pump comprises: a cryogenic pump container defining a cryogenic pump suction port; a refrigerator disposed within the cryogenic pump container and having a first cooling platform and a second cooling platform capable of being cooled to a temperature lower than that of the first cooling platform; a radiation shield thermally connected to the first cooling platform and extending axially from the cryogenic pump suction port into the cryogenic pump container; and a plurality of cryogenic plates thermally connected to the second cooling platform and arranged axially inside the radiation shield. The plurality of cryogenic plates includes: a top cryogenic plate axially closest to the cryogenic pump suction port; and at least one cryogenic plate axially spaced from the top cryogenic plate. The top cryogenic plate has an opening allowing gas to pass through the space between the top cryogenic plate and the at least one cryogenic plate. Invention Effects

[0007] According to the present invention, the influence on the exhaust velocity can be suppressed, and the adsorption capacity of the cryogenic pump can be improved. Attached Figure Description

[0008] Figure 1This is a schematic side sectional view illustrating an embodiment of a cryogenic pump.

[0009] Figure 2 This is a top view schematically illustrating the embodiment of the top cryogenic plate.

[0010] Figure 3 Figures (a) to (c) are schematic diagrams illustrating the growth of a condensation layer on the top low-temperature plate of the embodiment.

[0011] Figure 4 Figures (a) and (b) are side sectional views schematically illustrating another example of the top cryogenic plate of the embodiment.

[0012] In the diagram: 10-Cryogenic pump, 12-Cryogenic pump suction port, 14-Refrigerator, 16-Cryogenic pump container, 22-First cooling platform, 24-Second cooling platform, 30-Radiation shield, 41-Top cryogenic plate, 46-Opening, 50-Straight path, 60-Cryogenic plate. Detailed Implementation

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description and drawings, the same or equivalent constituent elements, components, and processes are labeled with the same reference numerals, and repeated descriptions are omitted where appropriate. The proportions and shapes of the parts shown in the drawings are provided for convenience in simplifying the description and should not be interpreted as limiting unless otherwise specified. The embodiments are illustrative and do not limit the scope of the invention in any way. All features or combinations thereof described in the embodiments are not necessarily essential to the invention.

[0014] Figure 1 This is a schematic side sectional view illustrating an embodiment of the cryogenic pump 10. Figure 1 The diagram shows a cross-section including the central axis of the cryogenic pump (hereinafter also referred to as the central axis). For ease of understanding, in Figure 1 The central axis C is indicated by a single-dot dashed line.

[0015] A cryogenic pump 10 is installed, for example, in the vacuum chamber 100 of an ion implantation apparatus, sputtering apparatus, evaporation apparatus, or other vacuum processing apparatus, to increase the vacuum level inside the vacuum chamber 100 to the level required for the desired vacuum processing. The cryogenic pump 10 has a cryogenic pump suction port 12 for receiving gas to be vented from the vacuum chamber 100. The gas enters the internal space of the cryogenic pump 10 through the cryogenic pump suction port 12.

[0016] Furthermore, in the following explanation, to clearly illustrate the positional relationships of the constituent components of the cryogenic pump 10, terms such as "axial" and "radial" will sometimes be used. The axial direction of the cryogenic pump 10 refers to the direction through the cryogenic pump suction port 12 (i.e., along the central axis C in the figure), and the radial direction refers to the direction along the cryogenic pump suction port 12 (perpendicular to the central axis C). For ease of explanation, the position relatively close to the cryogenic pump suction port 12 in the axial direction is referred to as "upper," and the position relatively far from the cryogenic pump suction port 12 is referred to as "lower." That is, the position relatively far from the bottom of the cryogenic pump 10 is referred to as "upper," and the position relatively close to the bottom of the cryogenic pump 10 is referred to as "lower." Regarding the radial direction, the position close to the center of the cryogenic pump suction port 12 (the central axis C in the figure) is referred to as "inner," and the position close to the periphery of the cryogenic pump suction port 12 is referred to as "outer." Furthermore, the direction around the central axis C is referred to as "circumferential." The circumferential direction is the second direction along the periphery of the cryogenic pump suction port 12, and is a tangential direction orthogonal to the radial direction.

[0017] This representation of the positional relationship of the constituent components of the cryogenic pump 10 is independent of the configuration of the cryogenic pump 10 when it is installed in the vacuum chamber 100. As shown, the cryogenic pump 10 can be installed in the vacuum chamber 100 with its suction port 12 facing upwards in the vertical direction. Conversely, the cryogenic pump 10 can be installed in the vacuum chamber 100 with its suction port 12 facing downwards in the vertical direction. Alternatively, the cryogenic pump 10 can be installed in the vacuum chamber 100 with other orientations.

[0018] The cryogenic pump 10 includes a refrigerator 14, a cryogenic pump container 16, a first-stage cryogenic plate 18, and a cryogenic plate unit 20. The first-stage (or level) cryogenic plate 18 may also be referred to as a high-temperature cryogenic plate section or a 100K section, etc. The cryogenic plate unit 20 is the second-stage (or level) cryogenic plate, and may also be referred to as a low-temperature cryogenic plate section or a 10K section, etc.

[0019] The refrigerator 14 is, for example, a Gifford-McMahon type refrigerator (so-called GM refrigerator) or other cryogenic refrigerator. The refrigerator 14 is a two-stage refrigerator, comprising a first cooling stage 22 and a second cooling stage 24. The refrigerator 14 is configured to cool the first cooling stage 22 to a first cooling temperature and the second cooling stage 24 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage 22 is cooled to approximately 65K to 120K, preferably 80K to 100K, and the second cooling stage 24 is cooled to approximately 10K to 20K. The first cooling stage 22 and the second cooling stage 24 may also be referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0020] Furthermore, the refrigerator 14 includes a refrigerator structure 21 that structurally supports the second cooling platform 24 to the first cooling platform 22, and structurally supports the first cooling platform 22 to the room temperature section 26 of the refrigerator 14. Therefore, the refrigerator structure 21 includes a first cylinder 23 and a second cylinder 25 extending coaxially along the radial direction of the cryogenic pump 10. The first cylinder 23 connects the room temperature section 26 of the refrigerator 14 to the first cooling platform 22. The second cylinder 25 connects the first cooling platform 22 to the second cooling platform 24. Typically, the first cooling platform 22 and the second cooling platform 24 are formed of a highly thermally conductive metal material such as copper (e.g., pure copper), and the first cylinder 23 and the second cylinder 25 are made of other metal materials such as stainless steel. The room temperature section 26, the first cylinder 23, the first cooling platform 22, the second cylinder 25, and the second cooling platform 24 are arranged in a straight line.

[0021] A first displacement device and a second displacement device (not shown) are respectively arranged inside the first cylinder 23 and the second cylinder 25 in a reciprocating manner. A first accumulator and a second accumulator (not shown) are respectively assembled on the first displacement device and the second displacement device. Furthermore, the room temperature section 26 corresponds to the drive section of the refrigerator 14 and has a drive mechanism (not shown) for reciprocating the first displacement device and the second displacement device. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically and repeatedly supply and discharge the working gas into and out of the refrigerator 14.

[0022] The refrigerator 14 is connected to a compressor (not shown) for the working gas. The refrigerator 14 causes the working gas, pressurized by the compressor, to expand internally, thereby cooling the first cooling platform 22 and the second cooling platform 24. The expanded working gas is recovered by the compressor and repressurized. The refrigerator 14 achieves cooling by repeatedly performing a thermal cycle, which includes the supply / discharge of the working gas and the reciprocating movement of the first and second displacementrs synchronized therewith.

[0023] The cryogenic pump 10 shown in the figure is a so-called horizontal cryogenic pump. A horizontal cryogenic pump generally refers to a cryogenic pump in which the refrigeration unit 14 is arranged intersecting (usually orthogonal) with the central axis C of the cryogenic pump 10. However, the present invention is also applicable to so-called vertical cryogenic pumps. A vertical cryogenic pump refers to a cryogenic pump in which the refrigeration unit is arranged along the axial direction of the cryogenic pump.

[0024] The cryogenic pump container 16 is a vacuum container configured to maintain a vacuum seal within its internal space. The cryogenic pump container 16 houses a refrigerator 14, a first-section cryogenic plate 18, and a cryogenic plate unit 20.

[0025] The cryogenic pump container 16 defines a cryogenic pump suction port 12 at its front end. The cryogenic pump container 16 has a suction port flange 16a extending radially outward from its front end. The suction port flange 16a is provided around the entire circumference of the cryogenic pump container 16. The cryogenic pump 10 is mounted in the vacuum chamber 100 of the vacuum processing apparatus via the suction port flange 16a. Alternatively, the cryogenic pump 10 can also be mounted in the vacuum chamber 100 via a gate valve (not shown).

[0026] Furthermore, the cryogenic pump container 16 includes: a container body 16b extending axially from the suction port flange 16a; a container bottom 16c enclosing the container body 16b on the side opposite to the cryogenic pump suction port 12; and a refrigerator housing 16d extending laterally between the suction port flange 16a and the container bottom 16c. The end of the refrigerator housing 16d is mounted on the room temperature section 26 of the refrigerator 14 on the side opposite to the container body 16b, thereby allowing the cryogenic section of the refrigerator 14 (i.e., the first cylinder 23, the first cooling platform 22, the second cylinder 25, and the second cooling platform 24) to be disposed within the cryogenic pump container 16 in a non-contact manner. The first cylinder 23 is disposed within the refrigerator housing 16d, and the first cooling platform 22, the second cylinder 25, and the second cooling platform 24 are disposed within the container body 16b. The first low-temperature plate 18 and the low-temperature plate unit 20 are also disposed within the container body 16b.

[0027] The first cryogenic plate 18 includes a radiation shield 30 and an inlet cryogenic plate 32, and surrounds the cryogenic plate unit 20. The first cryogenic plate 18 provides an ultra-low temperature surface to protect the cryogenic plate unit 20 from radiant heat from the exterior of the cryogenic pump 10 or from the cryogenic pump container 16. The first cryogenic plate 18 is thermally connected to the first cooling stage 22. Therefore, the first cryogenic plate 18 is cooled to a first cooling temperature. Gases (e.g., moisture) condensing at the first cooling temperature are captured by its surface. The first cryogenic plate 18 is typically made of a highly thermally conductive metal material such as copper (e.g., pure copper), and if necessary, the surface may be coated with a metal layer such as nickel.

[0028] There is a gap between the first cryogenic plate 18 and the cryogenic plate unit 20, and the first cryogenic plate 18 does not contact the cryogenic plate unit 20. The first cryogenic plate 18 also does not contact the cryogenic pump container 16.

[0029] The radiation shield 30 is provided to protect the cryogenic plate unit 20 from the radiant heat of the cryogenic pump container 16. The radiation shield 30 extends axially in a cylindrical (e.g., cylindrical) shape from the cryogenic pump suction port 12 into the cryogenic pump container 16. The radiation shield 30 is located between the cryogenic pump container 16 and the cryogenic plate unit 20, and surrounds the cryogenic plate unit 20. The radiation shield 30 has a diameter slightly smaller than the cryogenic pump container 16, and an outer gap 31 is formed between the radiation shield 30 and the cryogenic pump container 16. Therefore, the radiation shield 30 does not contact the cryogenic pump container 16.

[0030] The first cooling platform 22 of the refrigerator 14 is directly mounted on the outer side surface of the radiation shield 30. Thus, the radiation shield 30 is thermally connected to the first cooling platform 22 and is therefore cooled to a first cooling temperature. Alternatively, the first cooling platform 22 can be disposed within the refrigerator housing 16d, and the radiation shield 30 is mounted on the first cooling platform 22 via suitable heat transfer components. Furthermore, the second cooling platform 24 and the second cylinder 25 of the refrigerator 14 are inserted into the radiation shield 30 from its side.

[0031] The radiation shielding member 30 may include multiple shielding components constituting the radiation shielding member 30. For example, the radiation shielding member 30 includes an upper shielding member 30a configured close to the cryogenic pump suction port 12 and a lower shielding member 30b configured away from the cryogenic pump suction port 12. The upper shielding member 30a is disposed on the side of the cryogenic pump suction port 12 relative to the second cooling platform 24 of the refrigerator 14, and the lower shielding member 30b is disposed on the side of the container bottom 16c relative to the second cooling platform 24.

[0032] In the illustrated example, the upper shielding part 30a is a cylinder open at both ends, surrounding the upper part of the cryogenic plate unit 20. The lower shielding part 30b is a bottomed cylinder open at the upper end and closed at the lower end, surrounding the lower part of the cryogenic plate unit 20. Furthermore, the lower end of the upper shielding part 30a and the upper end of the lower shielding part 30b are approximately at the same height. The diameter of the upper shielding part 30a is slightly smaller than the diameter of the lower shielding part 30b, and the outer gap 31 of the shielding part is wider on the outer side of the upper shielding part 30a than on the outer side of the lower shielding part 30b.

[0033] The lower part 30b of the shield can be axially separated from the upper part 30a of the shield. In this case, as shown in the figure, a shield gap 34 is formed between the upper part 30a and the lower part 30b of the shield. The outer side gap 31 of the shield communicates with the inner space 36 of the radiation shield 30 through the shield gap 34. The shield gap 34 can be used as a gas inlet opening provided on the side of the radiation shield 30. The exhaust gas can be introduced from the outer side gap 31 through the shield gap 34 into the inner space 36 of the radiation shield 30.

[0034] The inlet cryogenic plate 32 is provided at the cryogenic pump suction port 12 to protect the cryogenic plate unit 20 from radiant heat from external heat sources (e.g., heat sources inside the vacuum chamber 100 where the cryogenic pump 10 is installed). The inlet cryogenic plate 32 is positioned axially above the cryogenic plate unit 20 in a non-contact manner. The inlet cryogenic plate 32 is mounted on the upper part 30a of the shielding member via a mounting member (not shown). Thus, the inlet cryogenic plate 32 is fixed to the radiation shielding member 30 and is thermally connected to the radiation shielding member 30.

[0035] The inlet cryogenic plate 32 has a planar structure disposed at the cryogenic pump suction port 12. The inlet cryogenic plate 32 may have a grid structure with multiple louvers in a concentric circle or grid shape, such as a louvered or herringbone shape. The inlet cryogenic plate 32 occupies the central portion of the opening area of ​​the cryogenic pump suction port 12 and forms an annular open area 37 between itself and the radiation shield 30.

[0036] The diameter of the inlet cryogenic plate 32 can be smaller than the inner diameter of the radiation shield 30 (e.g., the upper part of the shield 30a). However, in order for the inlet cryogenic plate 32 to occupy most of the upper inner open area of ​​the radiation shield 30, the diameter of the inlet cryogenic plate 32 can be, for example, more than 70%, or more than 80%, or more than 90% of the inner diameter of the radiation shield 30 (e.g., the upper part of the shield 30a).

[0037] Alternatively, the inlet cryogenic plate 32 may have a flat plate (e.g., a circular plate) with at least one opening. The inlet cryogenic plate 32 may be configured to span the entire cryogenic pump suction port 12.

[0038] The cryogenic plate unit 20 includes a plurality of cryogenic plates (41, 42, 43) arranged axially. These cryogenic plates are thermally connected to the second cooling stage 24 and are cooled to a second cooling temperature lower than the first cooling temperature. Furthermore, the cryogenic plate unit 20 may include a connecting cryogenic plate 44 that connects at least one of the plurality of cryogenic plates (41, 42, 43) to the second cooling stage 24 of the refrigerator 14.

[0039] For ease of explanation, the portion of these cryogenic plates closest to the cryogenic pump suction port 12 is referred to as the top cryogenic plate 41. Therefore, in the cryogenic plate unit 20, the top cryogenic plate 41 is axially positioned closest to the inlet cryogenic plate 32. The top cryogenic plate 41 has a front surface facing the cryogenic pump suction port 12 and a back surface facing the opposite side. The front surface of the top cryogenic plate 41 faces the back surface of the inlet cryogenic plate 32, and no other cryogenic plate is disposed between the top cryogenic plate 41 and the inlet cryogenic plate 32. The top cryogenic plate 41 is, for example, a circular plate-shaped component configured perpendicular to the axial direction, with its center located on or near the central axis C of the cryogenic pump 10.

[0040] To condense more gas, the top cryogenic plate 41 can be relatively large, with a diameter that is, for example, more than 70% or 80% of the diameter of the radiation shield 30 (e.g., the upper part 30a of the shield). Alternatively, the diameter of the top cryogenic plate 41 can be less than 98% or 90% of the diameter of the radiation shield 30 (e.g., the upper part 30a of the shield). This ensures that the top cryogenic plate 41 does not contact the radiation shield 30.

[0041] The top cryogenic plate 41 can be disposed approximately axially near the center within the container body 16b of the cryogenic pump container 16. The center of the top cryogenic plate 41 can be directly mounted on the upper surface of the second cooling platform 24 of the refrigerator 14. The axial distance from the inlet cryogenic plate 32 to the top cryogenic plate 41 can, for example, be in the range of 30-70% or 40-60% of the axial distance from the inlet cryogenic plate 32 to the container bottom 16c. Thus, a relatively wide free space is formed axially between the cryogenic plate unit 20 (i.e., the top cryogenic plate 41) and the inlet cryogenic plate 32. The area in the inner space 36 of the radiation shield 30 that is above the top cryogenic plate 41 can be used as an upper receiving space 38 for accommodating the condensate layer of the exhaust gas condensed on the top cryogenic plate 41.

[0042] In addition to the top cryogenic plate 41, the cryogenic plate unit 20 is provided with at least one cryogenic plate, such as one or more intermediate cryogenic plates 42 and one or more lower cryogenic plates 43, which are arranged axially spaced from the top cryogenic plate 41. In this example, one intermediate cryogenic plate 42 and two lower cryogenic plates 43 are provided.

[0043] In the axial direction, the intermediate low-temperature plate 42 is located below the top low-temperature plate 41 and above the second cooling platform 24, while the lower low-temperature plate 43 is located further below the second cooling platform 24. For example, the intermediate low-temperature plate 42 can be sandwiched between the top low-temperature plate 41 and the second cooling platform 24. Alternatively, the intermediate low-temperature plate 42 can be located at the same height as the second cooling platform 24 (e.g., between the upper and lower surfaces of the second cooling platform 24).

[0044] The axial distance between the intermediate low-temperature plate 42 and the lower low-temperature plate 43 is wider than the axial distance between the lower low-temperature plates 43, thereby forming a relatively wide condensation layer receiving space between the intermediate low-temperature plate 42 and the lower low-temperature plate 43. This space can be used as a lower receiving space 39 for the condensation layer that condenses on the lower low-temperature plate 43.

[0045] The shield gap 34 can be positioned at an axial height lower than the top cryogenic plate 41. This facilitates the introduction of the exhaust gas from the outer gap 31 through the shield gap 34 into the lower receiving space 39.

[0046] In the illustrated example, the intermediate cryogenic plate 42 and the lower cryogenic plate 43 each have a frustum-shaped shape, with a flat, circular central portion and a radially outwardly inclined outer periphery. The centers of these cryogenic plates are located on or near the central axis C of the cryogenic pump 10. As an example, the diameters of both the intermediate cryogenic plate 42 and the lower cryogenic plate 43 can be smaller than the diameter of the top cryogenic plate 41. Furthermore, the diameter of the intermediate cryogenic plate 42 can also be smaller than the diameter of the lower cryogenic plate 43.

[0047] A connecting cryogenic plate 44 extends from the second cooling platform 24 to the lower cryogenic plate 43, and thermally connects the lower cryogenic plate 43 to the second cooling platform 24. The connecting cryogenic plate 44 can be a group of elongated plate-shaped components extending axially along both radial sides of the second cooling platform 24. The upper end of the connecting cryogenic plate 44 is mounted on the second cooling platform 24, and the lower end is mounted on the lower cryogenic plate 43.

[0048] Figure 2 This is a schematic top view illustrating the top low-temperature plate 41 of the embodiment. That is, in Figure 2 The image shows the top cryogenic plate 41 as viewed along the central axis C from the cryogenic pump suction port 12. Furthermore, for ease of understanding, in... Figure 2 The second cooling platform 24 and the second cylinder block 25 of the refrigeration unit 14 are also shown. Additionally, Figure 1 Equivalent to along Figure 2 The cross-section shown is cut by line AA.

[0049] like Figure 1 and Figure 2 As shown, the top cryogenic plate 41 has an opening 46. The opening 46 extends from the front surface to the back surface through the top cryogenic plate 41, allowing gas to pass through the space between the top cryogenic plate 41 and at least one cryogenic plate located below it, namely the lower receiving space 39. This facilitates the introduction of the exhaust gas from the upper receiving space 38 into the lower receiving space 39 through the opening 46.

[0050] like Figure 2 As shown, the opening 46 may include at least one through hole formed on the top cryogenic plate 41. As an example, as shown, the opening 46 may include a plurality of through holes formed on the outer periphery of the top cryogenic plate 41 and arranged circumferentially. These through holes may be evenly spaced circumferentially. In the illustrated example, a single row of through holes is arranged circumferentially, but multiple rows of through holes may also be arranged circumferentially. The shape of the opening 46 may be circular, but it is not limited to this; it may also have other shapes such as rectangular or elongated holes.

[0051] The opening 46 can be configured so that it does not overlap with the refrigerator 14 when viewed from the cryogenic pump suction port 12. For example, as Figure 2 As shown, the opening 46 can be positioned on the top low-temperature plate 41 in a manner that avoids the second cylinder 25 of the refrigerator 14. The reason is as follows.

[0052] A temperature distribution is generated on the surface of the second cylinder block 25, varying from the first cooling temperature of the first cooling platform 22 to the second cooling temperature of the second cooling platform 24, with a condensation temperature region for exhaust gases such as argon present in between. Figure 2 In the diagram, the condensation temperature region is denoted by the symbol 48. During the operation of the refrigerator 14, the heat loads of the first cooling platform 22 and the second cooling platform 24 change, and consequently, the temperature distribution on the surface of the second cylinder 25 also changes, and the condensation temperature region may shift. As a result, the temperature of areas on the surface of the second cylinder 25 where gas has already condensed may rise. Consequently, the condensate may re-vaporize due to the increased temperature, potentially leading to a deterioration of the vacuum level within the cryogenic pump 10. To address this problem, the opening 46 can be positioned on the top cryogenic plate 41, away from the location of the second cylinder 25 of the refrigerator 14. This prevents the exhaust gas from reaching the second cylinder 25 through the opening 46 and also inhibits the condensation of gas on the surface of the second cylinder 25.

[0053] Furthermore, since the second cooling platform 24 is positioned directly below the center of the top low-temperature plate 41, the opening 46 can be opened as follows: Figure 2 As shown, it is positioned on the top low-temperature plate 41, bypassing the second cooling platform 24 of the refrigerator 14. Furthermore, the top low-temperature plate 41 can be mounted to the second cooling platform 24 at its center using bolts or other fasteners.

[0054] At least one cryogenic plate of the cryogenic plate unit 20 is configured to allow a straight path 50 to be formed from the cryogenic pump suction port 12 through the opening 46 and the lower receiving space 39 to the cryogenic plate. Figure 1 In the diagram, as an example of this straight path 50, a dashed arrow illustrates the straight path from the open area 37 through the upper receiving space 38 to the opening 46, and further from the opening 46 through the lower receiving space 39 to the lower cryogenic plate 43. This configuration of the cryogenic plate facilitates the introduction of the exhaust gas from the upper receiving space 38 through the opening 46 into the lower receiving space 39.

[0055] The axial height H from the top cryogenic plate 41 to the cryogenic pump suction port 12 can be greater than the opening width W of the opening 46. The axial height H can be 2, 3, 5, or 10 times greater than the opening width W of the opening 46. When the opening 46 is circular, the opening width W refers to the diameter of the opening 46.

[0056] As described later, it is preferable that the opening 46 is blocked by the condensate layer as the gas condenses on the top cryogenic plate 41. However, if the axial height H is less than the opening width W of the opening 46, i.e., the cryogenic pump suction port 12 is too close to the top cryogenic plate 41, the inlet cryogenic plate 32 may hinder the growth of the condensate layer on the top cryogenic plate 41. Therefore, by making the axial height H greater than the opening width W of the opening 46, it is possible to allow condensate layer growth sufficient to block the opening 46.

[0057] The cryogenic plates (41, 42, 43) constituting the cryogenic plate unit 20 are typically made of a highly thermally conductive metal material such as copper (e.g., pure copper), and if necessary, their surfaces may be coated with a metal layer such as nickel. Furthermore, an adsorbent material (e.g., activated carbon) for capturing non-condensable gases (e.g., hydrogen) by adsorption can be disposed on at least a portion of the surface of the cryogenic plate unit 20. For example, the adsorbent material can be disposed on the back surface of the top cryogenic plate 41, the middle cryogenic plate 42, and / or the bottom cryogenic plate 43.

[0058] Furthermore, the specific structure of the cryogenic plate unit 20 is not limited to the above. For example, an additional cryogenic plate can be provided between the top cryogenic plate 41 and the inlet cryogenic plate 32, and the diameter of this additional cryogenic plate can be smaller than the diameter of the top cryogenic plate 41. The top cryogenic plate 41 may have a radially outward inclined surface facing downward (or upward) on its outer periphery. The diameter of at least one of the intermediate cryogenic plate 42 and the lower cryogenic plate 43 (e.g., the lowermost cryogenic plate) may be larger than the diameter of the top cryogenic plate 41. The intermediate cryogenic plate 42 and / or the lower cryogenic plate 43 may also be a circular plate without an inclined surface, similar to the top cryogenic plate 41. When viewed from the axial direction, the shape of the cryogenic plate is not limited to a circle, and may also have other shapes such as rectangles or polygons.

[0059] Thus, the cryogenic pump 10 has three paths that guide the exhaust gas from the vacuum chamber 100 to the cryogenic plate unit 20 within the cryogenic pump 10. The first path 52 extends from the inlet cryogenic plate 32 and the open area 37 to the upper receiving space 38. The second path 54 extends from the outer gap 31 of the shielding member through the gap 34 of the shielding member to the lower receiving space 39. The third path, for example, a straight path 50, extends from the upper receiving space 38 through the opening 46 to the lower receiving space 39.

[0060] Furthermore, in this embodiment, as described above, the diameter of the top cryogenic plate 41 is relatively large, approximately the same as the diameter of the cryogenic pump intake port 12. Therefore, the gap 49 between the top cryogenic plate 41 and the upper shielding portion 30a of the radiation shield 30 is quite small. Consequently, the gas flow through the gap 49 from the upper receiving space 38 to the lower receiving space 39 is practically negligible. Therefore, the gap 49, unlike the third path described above, is not considered a gas flow path from the upper receiving space 38 to the lower receiving space 39.

[0061] The operation of the cryogenic pump 10 described above is explained below. Before starting the cryogenic pump 10, a suitable roughing pump (not shown) is used to roughly evacuate the vacuum chamber 100 to, for example, a cryogenic pump start-up pressure of approximately 1 Pa. Then, the cryogenic pump 10 is started. Driven by the refrigerator 14, the first cooling stage 22 and the second cooling stage 24 are cooled to the first cooling temperature and the second cooling temperature, respectively. Therefore, the first cryogenic plate 18 and the cryogenic plate unit 20, which are thermally connected to these cooling stages, are also cooled to the first cooling temperature and the second cooling temperature, respectively.

[0062] The inlet cryogenic plate 32 cools the gas flowing from the vacuum chamber 100 toward the cryogenic pump 10. On the surface of the inlet cryogenic plate 32, condenses form a vapor pressure sufficiently low (e.g., 10) at the first cooling temperature. -8 Gases below Pa. This gas can also be referred to as the first type of gas. The first type of gas is, for example, water vapor. Thus, the inlet cryogenic plate 32 can discharge the first type of gas.

[0063] like Figure 2 As shown, the exhaust gas flows towards the cryogenic plate unit 20 via the three paths described above. According to the first path 52, the gas enters the upper receiving space 38 from the vacuum chamber 100 through the inlet cryogenic plate 32 or the open area 37, and flows towards the top cryogenic plate 41. According to the second path 54, the gas enters the lower receiving space 39 from the vacuum chamber 100 through the outer gap 31 and the gap 34 of the shielding member, and flows towards the middle cryogenic plate 42 or the lower cryogenic plate 43. Furthermore, according to the third path, such as the straight path 50, the gas enters the lower receiving space 39 from the upper receiving space 38 through the opening 46, and flows towards the middle cryogenic plate 42 or the lower cryogenic plate 43.

[0064] Gas entering via the first path is cooled by the top cryogenic plate 41, and gas entering via the second path is cooled by the intermediate cryogenic plate 42 or the lower cryogenic plate 43. On the surfaces of these cryogenic plates, vapor pressure is condensed at a sufficiently low level (e.g., 10) at the second cooling temperature. -8 Gases below Pa. This gas can also be called a second gas. The second gas is, for example, argon (Ar). Thus, the cryogenic plate unit 20 can exhaust the second gas.

[0065] Gases with insufficient vapor pressure at the second cooling temperature are adsorbed onto the adsorbent material on the cryogenic plate unit 20. This gas can also be referred to as a third gas. The third gas is, for example, hydrogen (H2). Thus, the cryogenic plate unit 20 can discharge the third gas. Therefore, the cryogenic pump 10 can discharge various gases by condensation or adsorption to achieve the desired vacuum level in the vacuum chamber 100.

[0066] However, during the vacuum exhaust operation of the cryogenic pump 10, a condensation layer of the second gas grows on the cryogenic plate unit 20. This condensation layer comes into contact with a portion of the first cryogenic plate 18. As a result, the gas is re-vaporized at this contact point, causing the pressure inside the cryogenic pump 10 to rise. Subsequently, the cryogenic pump 10 cannot fully perform its intended function of exhausting the vacuum chamber 100. Therefore, the adsorption capacity of the condensation layer when it contacts the first cryogenic plate 18 determines the adsorption limit of the cryogenic pump 10.

[0067] When the condensate layer is concentrated in a specific location of the cryogenic plate unit 20, the condensate layer in that location comes into contact with the first cryogenic plate 18 first, and the cryogenic pump 10 may reach its adsorption limit. At this point, even if not much gas is condensed in other locations of the cryogenic plate unit 20, there is still ample space in the condensate layer, which cannot be utilized. That is, the potentially usable adsorption capacity is not utilized.

[0068] Basically, gas is more easily introduced into the upper containment space 38 compared to the lower containment space 39, and gas condensation tends to concentrate on the top cryogenic plate 41. The growth of the condensate layer on the top cryogenic plate 41 is faster compared to the other cryogenic plates in the cryogenic plate unit 20, such as the lower cryogenic plate 43. As a result, the condensate layer on the top cryogenic plate 41 may be the first to come into contact with the inlet cryogenic plate 32 or the upper part 30a of the shield. In this case, even if not much gas has condensed in the lower cryogenic plate 43 at this time, and the lower containment space 39 still has room for condensation, the cryogenic pump 10 will reach its adsorption limit. The lower containment space 39 is not fully utilized.

[0069] Therefore, by correcting this deviation in the condensation layer and achieving a balance between the upper containment space 38 and the lower containment space 39, the adsorption capacity of the cryogenic pump 10 can be improved.

[0070] From this perspective, the cryogenic pump 10 has the second path 54 described above. The gap 31 on the outer side of the shield and the gap 34 of the shield help to facilitate the introduction of gas from the vacuum chamber 100 into the lower receiving space 39, thereby partially correcting the situation where the condensate layer is biased towards the upper receiving space 38.

[0071] However, depending on the gas conductivity of the inlet cryogenic plate 32 and the ease of gas flow at the cryogenic pump suction port 12, the deviation correction effect of the second path 54 may not be sufficient to significantly improve the balance of condensation layer growth between the upper and lower containment spaces 38 and 39, and may not be very effective in improving adsorption capacity. This concern is easily apparent when the inlet cryogenic plate 32 has a louvered, herringbone, or other grid structure. This is because such grid structures often have a high gas conductivity, allowing gas to easily flow from the vacuum chamber 100 into the upper containment space 38 through the cryogenic pump suction port 12.

[0072] To balance the condensation layer growth in the upper containment space 38 and the lower containment space 39, one possible solution is to suppress gas inflow into the upper containment space 38 by modifying the design of the first cryogenic plate 18. For example, this could involve further reducing the opening diameter of the upper part 30a of the shield or further reducing the gas conductivity of the inlet cryogenic plate 32. However, this modification to the first cryogenic plate 18 would reduce the opening area of ​​the cryogenic pump intake port 12, potentially decreasing the exhaust velocity of the cryogenic pump 10. This is because the opening area of ​​the cryogenic pump intake port 12 is one of the main factors determining the exhaust velocity of the cryogenic pump 10.

[0073] This reduction in exhaust velocity can also affect the vacuum process in vacuum chamber 100. As a result, it can sometimes become less than ideal, requiring a redesign of the vacuum process. To avoid this, it is desirable that changes to the cryogenic pump design have minimal impact on the vacuum process.

[0074] According to the embodiment, an opening 46 is provided on the top cryogenic plate 41. This facilitates gas introduction into the lower containment space 39, improving the balance of condensate layer growth between the upper containment space 38 and the lower containment space 39. No design changes to the first cryogenic plate 18 are required. Therefore, according to the embodiment, the influence on exhaust velocity can be suppressed, while simultaneously increasing the adsorption capacity of the cryogenic pump 10.

[0075] Figure 3 Figures (a) to (c) are schematic diagrams illustrating the growth of the condensation layer 56 on the top low-temperature plate 41 according to the embodiment. In each figure, it is shown how the condensation layer 56 grows around the opening 46 of the top low-temperature plate 41.

[0076] like Figure 3 As shown in (a), during the initial vacuum exhaust operation of the cryogenic pump 10, the gas has not yet condensed on the top cryogenic plate 41. The gas flow, schematically indicated by arrow 58, enters the lower cryogenic space 39 from the upper containment space 38 through the opening 46. Thus, the gas is actively guided to the intermediate cryogenic plate 42 or the lower cryogenic plate 43 (see reference). Figure 1 ).

[0077] As the cryogenic pump 10 operates in vacuum exhaust mode... Figure 3 The initial stage shown in (a) continues, and a condensation layer 56 begins to form on the top low-temperature plate 41. Figure 3 As shown in (b), the condensation layer 56 grows on the top low-temperature plate 41, protruding from the outer periphery of the opening 46 towards the center as its height increases. However, the opening 46 is not completely sealed by the condensation layer 56, but remains open. Figure 3 In the middle stage of the growth of the condensation layer 56 shown in (b), although the gas flow rate is reduced compared to the initial stage, the gas flow (arrow 58) can still continue from the upper containment space 38 into the lower containment space 39 through the opening 46.

[0078] As the cryogenic pump 10 operates in vacuum exhaust mode... Figure 3 The intermediate stage shown in (b) continues further, with the condensation layer 56 growing further on the top low-temperature plate 41. Finally, as... Figure 3 As shown in (c), the opening 46 is blocked by the condensation layer 56, and no more gas flow occurs through the opening 46.

[0079] Thus, in the initial stage of vacuum exhaust operation, condensation of gas on the intermediate low-temperature plate 42 or the lower low-temperature plate 43 is promoted. On the other hand, as gas flows out from the upper containment space 38 through the opening 46 to the lower containment space 39, condensation of gas on the top low-temperature plate 41 is suppressed. Subsequently, if the opening 46 is blocked by the condensation layer 56, condensation of gas on the top low-temperature plate 41 will then be promoted. In this way, a balance can be achieved in the growth of the condensation layer in the upper containment space 38 and the lower containment space 39, and both the upper containment space 38 and the lower containment space 39 can be fully utilized.

[0080] According to the embodiment, the cryogenic plate unit 20 is so-called variable, meaning that it actively utilizes the lower containment space 39 in the initial stage of vacuum exhaust operation, and switches to actively utilize the upper containment space 38 as adsorption proceeds. The switching is based on the growth of the condensate layer 56 towards the opening 46, therefore no mechanical components are required for the switching. Therefore, there is no risk of contamination from particles or oil generated by mechanical components, or from the resulting contamination of the vacuum environment.

[0081] The present invention has been described above with reference to embodiments. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and various design changes and modifications are possible, and these modifications are also within the scope of the present invention. Various features described in conjunction with one embodiment can also be applied to other embodiments. New embodiments resulting from combinations possess the effects of each of the combined embodiments.

[0082] In the above embodiment, the top cryogenic plate 41 is a plate with through holes, but it can also have other configurations. For example, the top cryogenic plate 41 can have a structure similar to the inlet cryogenic plate 32. The top cryogenic plate 41 can, for example, have a grid structure with multiple louvers arranged in a concentric circle or grid pattern, such as louvered or herringbone patterns. This further promotes gas flow through the opening 46. (See reference...) Figure 4 Let's illustrate this with an example.

[0083] Figure 4 (a) and (b) are side sectional views schematically illustrating another example of the top cryogenic plate 41 of the embodiment. Figure 4 In (a) and (b), with Figure 1 Similarly, a cross-section of the top cryogenic plate 41, which includes the plane containing the central axis C, is shown.

[0084] like Figure 4 As shown in (a), the top low-temperature plate 41 has a plurality of low-temperature plates 60. Each low-temperature plate 60 can be a louvered louver, and these low-temperature plates 60 can be arranged in a concentric circle.

[0085] An opening 46 is formed between two adjacent cryogenic plates 60. In this example, the cryogenic plates 60 are configured to be parallel to each other, and each of the two adjacent cryogenic plates 60 has a cryogenic plate surface 60a parallel to the axial direction. The opening 46 is formed between the cryogenic plate surface 60a of one of the two adjacent cryogenic plates 60 and the cryogenic plate surface 60a of the other cryogenic plate 60.

[0086] like Figure 4 As shown in (b), as the cryogenic pump 10 continues to operate in vacuum, a condensation layer 56 forms on the top cryogenic plate 41. During the middle stage of the growth of the condensation layer 56, the opening 46 is in an open state, but it will eventually be blocked by the condensation layer 56 as shown in the figure.

[0087] In another embodiment, the low-temperature plate surface 60a of the low-temperature plate 60 may be tilted relative to the axial direction.

[0088] In the above embodiment, the lower part 30b of the shielding member is axially separated from the upper part 30a of the shielding member, but the radiation shielding member 30 can also have other configurations. For example, the lower part 30b of the shielding member can be axially continuous with the upper part 30a of the shielding member. In other words, the radiation shielding member 30 can be a single component consisting of the upper part 30a and the lower part 30b of the shielding member. The radiation shielding member 30 may not have a gas inlet opening provided on the side of the radiation shielding member 30, as described in the shielding member gap 34, and the second path 54 may not exist. In this case, since the third path through the opening 46 is present, it can also promote the introduction of gas into the lower receiving space 39, improving the balance of condensation layer growth between the upper receiving space 38 and the lower receiving space 39.

[0089] The present invention has been described above with reference to the embodiments. The present invention is not limited to the above-described embodiments. Those skilled in the art should understand that the present invention can be modified in various ways and various variations can exist, and these variations are also within the scope of the present invention.

Claims

1. A cryogenic pump, characterized in that, have: Cryogenic pump container, which defines the cryogenic pump suction port; A refrigeration unit is disposed inside the cryogenic pump container and includes a first cooling platform and a second cooling platform that can be cooled to a temperature lower than that of the first cooling platform; A radiation shielding element, thermally connected to the first cooling platform, and extending axially from the cryogenic pump intake port into the cryogenic pump container; and Multiple low-temperature plates, thermally connected to the second cooling platform, are arranged along the axial direction inside the radiation shield. The plurality of low-temperature plates include: The top cryogenic plate that is closest to the cryogenic pump suction port in the axial direction; and At least one low-temperature plate is disposed with a space between it and the top low-temperature plate along the axial direction. The top cryogenic plate has an opening that allows gas to pass through the space between the top cryogenic plate and the at least one cryogenic plate.

2. The cryogenic pump according to claim 1, characterized in that, The opening is configured so that it does not overlap with the refrigerator when viewed from the air inlet of the cryogenic pump.

3. The cryogenic pump according to claim 1 or 2, characterized in that, The at least one cryogenic plate is configured to allow a straight path to be formed from the cryogenic pump intake through the opening and the space to the at least one cryogenic plate.

4. The cryogenic pump according to claim 1 or 2, characterized in that, The top cryogenic plate has a front surface facing the cryogenic pump intake and a back surface opposite to the front surface. The opening extends from the front surface through the top cryogenic plate to the back surface.

5. The cryogenic pump according to claim 1 or 2, characterized in that, The top low-temperature plate has multiple low-temperature plates. The opening is formed between two adjacent low-temperature plates among the plurality of low-temperature plates.

6. The cryogenic pump according to claim 5, characterized in that, The two adjacent low-temperature plates each have a low-temperature plate surface parallel to the axial direction. The opening is formed between the surface of one of the two adjacent low-temperature plates and the surface of the other low-temperature plate.

7. The cryogenic pump according to claim 1 or 2, characterized in that, The axial height from the top cryogenic plate to the cryogenic pump suction port is greater than the opening width of the opening.

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