Cryopump

Abstract

A cryopump (10) comprises: a cryopump container (16) that has an air inlet (12); a radiation shield (30) that is cooled to a first cooling temperature and extends into the cryopump container (16) from the air inlet (12); a cryo-panel unit (20) that is cooled to a second cooling temperature which is lower than the first cooling temperature and that is disposed so as to be surrounded by the radiation shield (30) in the cryopump container (16); and an air inlet shield (32) that is cooled to the first cooling temperature and is disposed at the air inlet (12) such that the cryo-panel unit (20) cannot be seen from outside the cryopump (10). The radiation shield (30) has a first gas intake port (34) which is formed at a height between the air inlet shield (32) and the cryo-panel unit (20).

Description

Technical Field

[0001] The present invention relates to a cryopump.

Background Art

[0002] A cryopump is a vacuum pump that captures gas molecules by condensation or adsorption on a cryopanel cooled to an extremely low temperature and evacuates them. Cryopumps are generally used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A cryopump is known in which an inlet cryopanel having openings such as a large number of small holes is disposed at the intake port of the cryopump. For example, a target gas such as argon enters the cryopump from the outside through the openings of the inlet cryopanel and is captured by a cryopanel that is colder than the inlet cryopanel disposed inside the cryopump. The captured target gas forms ice blocks on this low-temperature cryopanel.

[0005] However, the entry into the cryopump is not limited to the target gas only. Low vapor pressure gases such as water vapor, which should be shielded by the inlet cryopanel, and radiant heat can also enter the cryopump to some extent through the opening in the inlet cryopanel. Therefore, ice blocks on the low-temperature cryopanel are formed not only from the target gas but also from a mixture of gases (e.g., argon and water vapor). Due to differences in the physical properties of different gas species (e.g., thermal conductivity, lattice constant), ice blocks made from a mixture of gases tend to be more brittle and prone to cracking than ice blocks made from the target gas alone. Radiant heat can enter the ice block, causing a temperature increase and accelerating cracking. If the ice block cracks and the ice fragments fall and come into contact with hotter parts such as radiation shields, there is a concern that the vaporization of the ice fragments could cause a sudden pressure increase (also known as a microburst).

[0006] One exemplary objective of a certain aspect of the present invention is to reduce the risk of microbursts occurring in a cryopump. [Means for solving the problem]

[0007] According to one aspect of the present invention, the cryopump comprises a cryopump container having a cryopump intake port, a radiant shield cooled to a first cooling temperature and extending from the cryopump intake port into the cryopump container, a cryopanel unit cooled to a second cooling temperature lower than the first cooling temperature and positioned within the cryopump container so as to be surrounded by the radiant shield, and an intake port shield cooled to the first cooling temperature and positioned at the cryopump intake port such that the cryopanel unit is not visible from outside the cryopump. The radiant shield has a first gas inlet formed at the height between the intake port shield and the cryopanel unit. [Effects of the Invention]

[0008] According to the present invention, the risk of microbursts occurring within a cryopump can be reduced. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic side cross-sectional view showing a cryopump according to an embodiment. [Figure 2] Figure 1 is a schematic side view showing the radiation shield inside the cryopump. [Figure 3] This is a schematic side cross-sectional view of a cryopump relating to a comparative example. [Figure 4] Figures 4(a) and 4(b) are schematic side views illustrating other examples of radiation shields and intake shields applicable to the cryopump shown in Figure 1, respectively, and Figure 4(c) is a schematic top view illustrating other examples of radiation shields and intake shields applicable to the cryopump shown in Figure 1. [Figure 5] This is a schematic top view showing other examples of radiation shields and intake shields that can be applied to the cryopump shown in Figure 1. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0011] Figure 1 is a schematic side cross-sectional view showing a cryopump 10 according to an embodiment. Figure 2 is a schematic side view showing the radiation shield inside the cryopump 10 shown in Figure 1. Figure 1 shows a cross-section including the cryopump central axis (hereinafter simply referred to as the central axis) C. For ease of understanding, the central axis C is shown as a dashed line in Figure 1.

[0012] The cryopump 10 is used to raise the vacuum level inside the vacuum chamber to the level required for a desired vacuum process, for example, by being installed in the vacuum chamber of an ion implantation apparatus, sputtering apparatus, deposition apparatus, or other vacuum process apparatus. The cryopump 10 has a cryopump intake port (hereinafter also simply referred to as the "intake port") 12 for receiving the gas to be exhausted from the vacuum chamber. The gas enters the internal space of the cryopump 10 through the intake port 12.

[0013] In the following, the terms "axial direction" and "radial direction" may be used to clearly represent the positional relationships of the components of the cryopump 10. The axial direction of the cryopump 10 represents the direction passing through the intake port 12 (i.e., the direction along the central axis C in the figure), and the radial direction represents the direction along the intake port 12 (the direction perpendicular to the central axis C). For convenience, relative proximity to the intake port 12 in the axial direction may be referred to as "up," and relative distance as "down." In other words, relative distance from the bottom of the cryopump 10 may be referred to as "up," and relative proximity as "down." Regarding the radial direction, proximity to the center of the intake port 12 (central axis C in the figure) may be referred to as "inside," and proximity to the periphery of the intake port 12 may be referred to as "outside." Note that these expressions are not related to the arrangement when the cryopump 10 is installed in a vacuum chamber. For example, the cryopump 10 may be installed in a vacuum chamber with the intake port 12 facing downwards in the vertical direction.

[0014] Furthermore, the direction surrounding the axial direction is sometimes called the "circumferential direction." The circumferential direction is the second direction along the intake port 12 and is the tangential direction perpendicular to the radial direction.

[0015] The cryopump 10 comprises a refrigerator 14, a cryopump vessel 16, a first-stage cryopanel 18, and a cryopanel unit 20. The first-stage cryopanel 18 may also be referred to as the high-temperature cryopanel section or the 100K section. The cryopanel unit 20 is the second-stage cryopanel and may also be referred to as the low-temperature cryopanel section or the 10K section.

[0016] The refrigerator 14 is a cryogenic refrigerator, such as a Gifford-McMahon type refrigerator (a so-called GM refrigerator). The refrigerator 14 is a two-stage refrigerator and comprises 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 about 65K to 120K, preferably 80K to 100K, and the second cooling stage 24 is cooled to about 10K to 20K. The first cooling stage 22 and the second cooling stage 24 may also be called a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0017] Furthermore, the refrigerator 14 includes a refrigerator structure 21 that structurally supports the second cooling stage 24 in relation to the first cooling stage 22, and structurally supports the first cooling stage 22 in relation 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 that extend coaxially along the radial direction. The first cylinder 23 connects the room temperature section 26 of the refrigerator 14 to the first cooling stage 22. The second cylinder 25 connects the first cooling stage 22 to the second cooling stage 24. Typically, the first cooling stage 22 and the second cooling stage 24 are made of a highly thermally conductive metal material such as copper (e.g., pure copper), while 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 stage 22, the second cylinder 25, and the second cooling stage 24 are arranged in a straight line in this order.

[0018] A first displacer and a second displacer (not shown) are reciprocally mounted inside the first cylinder 23 and the second cylinder 25, respectively. A first regenerator and a second regenerator (not shown) are incorporated into the first and second displacers, respectively. The room temperature section 26 also has a drive mechanism (not shown) for reciprocating the first and second displacers. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically repeat the supply and discharge of the working gas into the refrigerator 14.

[0019] The refrigerator 14 is connected to a compressor (not shown) of a working gas. The refrigerator 14 expands the working gas pressurized by the compressor inside to cool the first cooling stage 22 and the second cooling stage 24. The expanded working gas is recovered by the compressor and pressurized again. The refrigerator 14 generates cold by repeating a heat cycle including the supply and discharge of the working gas and the reciprocating motion of the first displacer and the second displacer synchronized therewith.

[0020] The illustrated cryopump 10 is a so-called horizontal cryopump. A horizontal cryopump is generally a cryopump in which the refrigerator 14 is arranged so as to intersect (usually orthogonally) the central axis C of the cryopump 10. The present invention can be similarly applied to a so-called vertical cryopump. A vertical cryopump is a cryopump in which the refrigerator is arranged along the axial direction of the cryopump.

[0021] The cryopump container 16 is a vacuum container configured to maintain the vacuum tightness of its internal space. The cryopump container 16 houses the refrigerator 14, the first-stage cryopanel 18, and the cryopanel unit 20.

[0022] The intake port 12 is defined by the front end of the cryopump container 16. The cryopump container 16 includes an intake port flange 16a extending radially outward from its front end. The intake port flange 16a is provided over the entire circumference of the cryopump container 16. The cryopump 10 is attached to the vacuum chamber of the vacuum processing apparatus using the intake port flange 16a.

[0023] Furthermore, the cryopump vessel 16 has a vessel body 16b extending axially from the intake flange 16a, a vessel bottom 16c that closes the vessel body 16b on the opposite side of the intake port 12, and a refrigerator housing cylinder 16d extending laterally between the intake flange 16a and the vessel bottom 16c. The end of the refrigerator housing cylinder 16d on the opposite side of the vessel body 16b is attached to the room temperature section 26 of the refrigerator 14, thereby positioning the low-temperature section of the refrigerator 14 (i.e., the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24) within the cryopump vessel 16 in non-contact with the cryopump vessel 16. The first cylinder 23 is located in the refrigerator housing cylinder 16d, and the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are located in the vessel body 16b. The first stage cryo panel 18 and the cryo panel unit 20 are also located in the vessel body 16b.

[0024] The first-stage cryopanel 18, comprising a radiation shield 30 and an air intake shield 32, surrounds the cryopanel unit 20. The first-stage cryopanel 18 provides a cryogenic surface to protect the cryopanel unit 20 from radiant heat from the outside of the cryopump 10 or from the cryopump vessel 16. The first-stage cryopanel 18 is thermally coupled to the first cooling stage 22. Thus, the first-stage cryopanel 18 is cooled to a first cooling temperature. The first-stage cryopanel 18 has a gap between it and the cryopanel unit 20, and the first-stage cryopanel 18 is not in contact with the cryopump vessel 20. The first-stage cryopanel 18 is also not in contact with the cryopump vessel 16.

[0025] The radiation shield 30 is provided to protect the cryopump container 16 from radiant heat. The radiation shield 30 extends axially in a cylindrical shape (e.g., cylindrical) into the cryopump container 16 from the air intake 12. The radiation shield 30 is located between the cryopump container 16 and the cryopump container 20 and surrounds the cryopump container 20. The radiation shield 30 has a diameter slightly smaller than the cryopump container 16, and an outer shield gap 31 is formed between the radiation shield 30 and the cryopump container 16. Therefore, the radiation shield 30 does not come into contact with the cryopump container 16.

[0026] The first cooling stage 22 of the refrigerator 14 is directly attached to the outer side surface of the radiant shield 30. In this way, the radiant shield 30 is thermally coupled to the first cooling stage 22 and is therefore cooled to the first cooling temperature. The radiant shield 30 may also be attached to the first cooling stage 22 via an appropriate heat transfer member. In addition, the second cooling stage 24 and the second cylinder 25 of the refrigerator 14 are inserted into the radiant shield 30 from its side.

[0027] The radiation shield 30 comprises an upper shield 30a positioned on the intake port 12 side relative to the second cooling stage 24 of the refrigerator 14, and a lower shield 30b positioned on the container bottom 16c side relative to the second cooling stage 24. The upper shield 30a is a cylinder with both ends open and surrounds the upper part of the cryopanel unit 20. The lower shield 30b is a bottomed cylinder with its upper end open and its lower end closed, and surrounds the lower part of the cryopanel unit 20. The lower end of the upper shield 30a and the upper end of the lower shield 30b are at approximately the same height. The diameter of the upper shield 30a is somewhat smaller than the diameter of the lower shield 30b, and the outer shield gap 31 is wider outside the upper shield 30a (compared to outside the lower shield 30b).

[0028] As will be described in more detail later, the radiation shield 30 has a first gas inlet 34 and a second gas inlet 36. The first gas inlet 34 is formed at the height between the intake shield 32 and the cryopanel unit 20. The second gas inlet 36 is formed at the height between the part of the cryopanel unit 20 closest to the intake port 12 and the bottom of the container 16c.

[0029] The intake shield 32 is provided at the intake port 12 to protect the cryopump unit 20 from radiant heat from an external heat source (e.g., a heat source inside the vacuum chamber in which the cryopump 10 is installed). The intake shield 32 is thermally coupled to the first cooling stage 22 via the radiant shield 30 and, like the radiant shield 30, is cooled to a first cooling temperature. As a result, gases (e.g., water) that condense at the first cooling temperature are trapped on its surface.

[0030] The intake shield 32 is positioned at the intake port 12 such that the cryopanel unit 20 is not visible from outside the cryopump 10. In this embodiment, the intake shield 32 completely covers the end opening of the radiation shield 30 on the intake port 12 side, i.e., the upper end opening of the upper part 30a of the shield. There are no openings in the intake shield 32, and radiant heat and gases entering the intake shield 32 from outside the cryopump 10 are completely shielded by the intake shield 32.

[0031] The intake port shield 32 is a disc positioned perpendicular to the central axis C so as to traverse the intake port 12, with a diameter equal to the diameter of the upper part of the shield 30a, and is coupled to the upper end of the upper part of the shield 30a. The intake port shield 32 may be attached to a joint block (not shown) at its outer circumference. The joint block is a protrusion that projects radially inward from the upper end of the upper part of the shield 30a, and is formed at equal intervals (e.g., every 90°) in the circumferential direction. The intake port shield 32 is fixed to the joint block using fasteners such as bolts, or by welding or other appropriate method.

[0032] The outer gap 31 of the shield is not blocked by the intake shield 32. If necessary, the intake shield 32 may have a larger diameter than the radiation shield 30, thereby covering a portion of the outer gap 31 of the shield.

[0033] The cryopanel unit 20 comprises multiple cryopanels arranged axially. For convenience of explanation, the portion of these cryopanels closest to the air intake 12 is referred to as the top cryopanel 41. Each of these cryopanels is thermally coupled to the second cooling stage 24 and cooled to a second cooling temperature lower than the first cooling temperature. The cryopanel unit 20 is positioned below the air intake shield 32 within the cryopump vessel 16, surrounded by the radiation shield 30. The cryopanel unit 20 is not in contact with the radiation shield 30 or the air intake shield 32.

[0034] The top cryo panel 41 has its front facing the back surface of the intake shield 32, and no other cryo panels are provided between the top cryo panel 41 and the intake shield 32. The top cryo panel 41 is positioned approximately midway in the axial direction within the vessel body 16b of the cryopump vessel 16. The center of the top cryo panel 41 may be directly attached to the upper surface of the second cooling stage 24 of the chiller 14. The axial distance from the intake shield 32 to the top cryo panel 41 may be, for example, 30-70% or 40-60% of the axial distance from the intake shield 32 to the bottom of the vessel 16c. In this way, a relatively large space for accommodating the condensed layer 90 of the exhaust gas condensing on the top cryo panel 41 is formed above the top cryo panel 41. The condensed layer 90 may form a hemispherical ice mass as shown in the figure.

[0035] The top cryo panel 41 is a disc-shaped member positioned perpendicular to the axial direction, with its center located on or near the central axis C of the cryopump 10. The top cryo panel 41 is flat on all surfaces and has no inclined surfaces. To condense more gas, the top cryo panel 41 is relatively large, and its diameter may be, for example, 70% or more or 80% or more of the intake shield 32. Alternatively, the diameter of the top cryo panel 41 may be 98% or less or 90% or less of the diameter of the intake shield 32. This ensures that the top cryo panel 41 is not in contact with the radiation shield 30. The axial projected area of ​​the top cryo panel 41 may be 50% to 95% of the intake shield 32 area, preferably 73% to 90%.

[0036] In addition to the top cryopanel 41, the cryopanel unit 20 is provided with one or more intermediate cryopanels 42, one or more lower cryopanels 43, and a connecting cryopanel 44. In this example, there is one intermediate cryopanel 42 and two lower cryopanels 43. The axial distance between the intermediate cryopanel 42 and the lower cryopanels 43 is wider than the axial distance between the lower cryopanels 43, thereby creating a relatively large condensate layer containment space between the intermediate cryopanel 42 and the lower cryopanels 43.

[0037] The intermediate cryopanel 42 and the lower cryopanel 43 each have a frustoconical shape, with a flat, disc-shaped center and an outer periphery that slopes radially outward and downward. The centers of these cryopanels are located on or near the central axis C of the cryopump 10. The intermediate cryopanel 42 is located below the top cryopanel 41 and above the second cooling stage 24, while the lower cryopanel 43 is located below the second cooling stage 24. The intermediate cryopanel 42 may also be located at the same height as the second cooling stage 24 (between the top and bottom surfaces of the second cooling stage 24). In this example, the diameters of both the intermediate cryopanel 42 and the lower cryopanel 43 are smaller than the diameter of the top cryopanel 41, and the diameter of the intermediate cryopanel 42 is smaller than the diameter of the lower cryopanel 43.

[0038] The connecting cryopanel 44 extends from the second cooling stage 24 to the lower cryopanel 43, thermally bonding the lower cryopanel 43 to the second cooling stage 24. The connecting cryopanel 44 may also be a pair of elongated plate-like members extending axially on both radial sides of the second cooling stage 24. The upper end of the connecting cryopanel 44 is attached to the second cooling stage 24, and the lower end is attached to the lower cryopanel 43.

[0039] Each cryopanel constituting the cryopanel unit 20 is generally made of a highly thermally conductive metal material such as copper (e.g., pure copper), and its surface may be coated with a metal layer such as nickel if required. Furthermore, an adsorbent (e.g., activated carbon) for capturing non-condensable gases (e.g., hydrogen) by adsorption may be provided on at least a portion of the surface of the cryopanel unit 20. The adsorbent may be provided, for example, on the back surface of the top cryopanel 41, the intermediate cryopanel 42, and / or the lower cryopanel 43.

[0040] The specific configuration of the cryopanel unit 20 is not limited to those described above. For example, an additional cryopanel may be provided between the top cryopanel 41 and the intake shield 32, and such an additional cryopanel may have a smaller diameter than the top cryopanel 41. The top cryopanel 41 may have a radially outward downward (or upward) inclined surface on its outer circumference. At least one of the intermediate cryopanel 42 and the lower cryopanel 43 (for example, the lowest cryopanel) may have a larger diameter than the top cryopanel 41. The intermediate cryopanel 42 and / or the lower cryopanel 43 may be disc-shaped plates without inclined surfaces, similar to the top cryopanel 41. The shape of the cryopanel when viewed from the axial direction is not limited to a circle, and may have other shapes such as rectangles or polygons.

[0041] The first gas inlet 34 is a plurality of openings formed in the upper part 30a of the shield, located at the axial height between the intake shield 32 and the top cryo panel 41. The first gas inlet 34 may be positioned relatively high and may be closer to the intake shield 32 than to the top cryo panel 41. The first gas inlet 34 may be formed at the upper end of the upper part 30a of the shield, below the upper edge of the upper part 30a of the shield.

[0042] Each opening forming the first gas inlet 34 is, as shown in Figure 2, a small, elongated hole in the circumferential direction in this example. These holes are spaced equally in the circumferential direction. The total area of ​​the openings of the first gas inlet 34 may be, for example, 10% or less, or 5% or less, of the area of ​​the intake port 12. The shape and arrangement of the openings can be appropriately determined to achieve the desired exhaust performance (e.g., exhaust speed) of the cryopump 10.

[0043] The second gas inlet 36 is formed at the axial height between the top cryo panel 41 and the bottom of the container 16c, in this example, at the axial height between the intermediate cryo panel 42 and the lower cryo panel 43. The second gas inlet 36 may also be formed between the top cryo panel 41 and the intermediate cryo panel 42.

[0044] The second gas inlet 36 has a plurality of openings 36a formed in the upper part 30a of the shield (for example, the lower end of the upper part 30a of the shield) and a shield gap 36b between the upper part 30a of the shield and the lower part 30b of the shield. The openings 36a are small, elongated holes in the circumferential direction, similar to the first gas inlet 34, and are provided at equal intervals in the circumferential direction. In this example, the openings 36a are somewhat longer in the circumferential direction than the openings forming the first gas inlet 34. The shield gap 36b is defined between the lower end of the upper part 30a of the shield and the upper end of the lower part 30b of the shield. The shape and arrangement of the second gas inlet 36 can be appropriately determined to achieve the desired exhaust performance (e.g., exhaust speed) of the cryopump 10.

[0045] The operation of the cryopump 10 with the above configuration is described below. Before operating the cryopump 10, the inside of the vacuum chamber is first roughly vacuumed to about 1 Pa using another suitable rough pump. Then, the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled to the first cooling temperature and the second cooling temperature, respectively, by the operation of the refrigerator 14. As a result, the first stage cryopanel 18 and the cryopanel unit 20, which are thermally coupled to these, are also cooled to the first cooling temperature and the second cooling temperature, respectively.

[0046] The intake shield 32 cools the gas flying from the vacuum chamber toward the cryopump 10. The surface of the intake shield 32 is coated with a vapor pressure that is sufficiently low at the first cooling temperature (e.g., 10 -8 Gases (below Pa) condense. These gases may be called first-class gases. First-class gases are, for example, water vapor. In this way, the intake shield 32 can exhaust the first-class gas. The intake shield 32 can also shield against radiant heat (shown by solid arrows in Figure 1) directed from the vacuum chamber to the cryopump 10.

[0047] Some of the gas enters the outer gap 31 of the shield from around the intake shield 32. The first type of gas condenses on the surface of the upper part 30a of the shield that defines the outer gap 31. Gases whose vapor pressure is not sufficiently low at the first cooling temperature may enter the radiant shield 30 from the first gas inlet 34 or the second gas inlet 36 (shown by dashed arrows in Figure 1).

[0048] The gas entering from the first gas inlet 34 is cooled by the top cryopanel 41. The gas entering from the second gas inlet 36 is cooled by the intermediate cryopanel 42 or the lower cryopanel 43. On the surfaces of these cryopanels, a vapor pressure that is sufficiently low at the second cooling temperature (e.g., 10°C) is cooled. -8 Gases (below Pa) condense. These gases may also be called Type 2 gases. An example of a Type 2 gas is argon (Ar). In this way, the cryopanel unit 20 can exhaust the Type 2 gas.

[0049] Gases whose vapor pressure is not sufficiently low at the second cooling temperature are adsorbed onto the adsorbent on the cryopanel unit 20. This gas may be referred to as a third type gas. A third type gas is, for example, hydrogen (H2). In this way, the cryopanel unit 20 can exhaust the third type gas. Therefore, the cryopump 10 can exhaust various gases by condensation or adsorption and bring the vacuum level of the vacuum chamber to a desired level.

[0050] Figure 3 is a schematic side cross-sectional view of a cryopump according to a comparative example. In this cryopump, an inlet cryopanel 80 having a number of openings 82 is attached to the upper end opening of a radiation shield 30. These openings 82 are formed in the center of the inlet cryopanel 80. The radiation shield 30 does not have any openings for taking in gas.

[0051] In this comparative example, radiant heat enters the radiant shield 30 through the opening 82 of the inlet cryo panel 80 (shown by a solid arrow in Figure 3). Since these openings 82 face the condensation layer 90 formed on the top cryo panel 41 of the cryo panel unit 20, radiant heat enters the surface of the condensation layer 90 from the openings 82, and can raise the temperature of the condensation layer 90. In addition, a mixed gas of type 1 and type 2 gases (for example, a mixed gas of water vapor and argon gas) that did not condense on the surface of the inlet cryo panel 80 also enters the radiant shield 30 through the opening 82 (shown by a dashed arrow in Figure 3). Therefore, the condensation layer 90 may contain both type 1 and type 2 gases.

[0052] Ice blocks made from mixed gases tend to be more brittle and prone to cracking than ice blocks made from a single gas, due to differences in the physical properties (e.g., thermal conductivity, lattice constant) of the different gases. For example, an ice block made from a mixture of water vapor and argon gas is more prone to cracking than an ice block made from argon gas alone. The rise in surface temperature due to radiant heat incident on the ice block can also accelerate cracking. If the ice block cracks and the ice fragments fall and come into contact with the radiation shield 30, the ice fragments will rapidly vaporize. This can cause a sudden pressure increase (also called a microburst) within the cryopump 10. This is undesirable because it can negatively affect the exhaust performance of the cryopump 10.

[0053] According to the cryopump 10 of this embodiment, the first type of gas is basically captured on the intake shield 32. Most of the first type of gas that enters the gap 31 on the outside of the shield without being captured is captured on the side of the radiation shield 30 before it reaches the first gas inlet 34 or the second gas inlet 36. Therefore, it can be expected that the first type of gas hardly enters the radiation shield 30 and hardly mixes with the condensate layer 90. The second and third type of gases can be received into the radiation shield 30 from the first gas inlet 34 or the second gas inlet 36. Furthermore, since the intake shield 32 is positioned so that the cryopanel unit 20 is not visible from outside the cryopump 10, the intake shield 32 can block the incidence of radiant heat from outside the cryopump 10 to the cryopanel unit 20. Therefore, the temperature rise of the condensate layer 90 is also suppressed. In particular, in this embodiment, the upper opening of the radiation shield 30 is completely sealed by the intake shield 32, so the entry of the first type gas and radiant heat can be effectively prevented compared to the comparative example. Therefore, the cryopump 10 according to this embodiment can reduce the risk of microbursts occurring inside the cryopump 10.

[0054] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. Various features described in relation to one embodiment are applicable to other embodiments. New embodiments resulting from combinations will possess the combined effects of each of the embodiments combined.

[0055] In the above-described embodiment, the radiation shield 30 has a divided structure consisting of an upper shield 30a and a lower shield 30b. However, the radiation shield 30 may also be a single component extending from the air intake 12 to the bottom of the container 16c, and the first gas inlet 34 and the second gas inlet 36 may be formed in such a single component.

[0056] In the above-described embodiment, the first gas inlet 34 is provided in the radiation shield 30. However, the first gas inlet 34 may be provided between the radiation shield 30 and the intake shield 32. For example, as shown in Figure 4(a), the first gas inlet 34 may be a notch formed in the upper edge of the radiation shield 30. Alternatively, as shown in Figure 4(b), the intake shield 32 may be positioned with a gap axially upward from the upper edge of the radiation shield 30. As shown in Figure 4(c), the intake shield 32 may be positioned with a gap radially inward from the upper edge of the radiation shield 30 (i.e., the first gas inlet 34).

[0057] In the above-described embodiment, the intake shield 32 completely blocks the upper end opening of the radiation shield 30. However, an opening as the first gas inlet 34 may be formed in the intake shield 32. In this case, in order to prevent radiant heat from directly entering the cryopanel unit 20 through the opening of the intake shield 32, the opening of the intake shield 32 may be positioned on the intake shield 32 such that the cryopanel unit 20 is not visible from outside the cryopump 10. As shown in Figure 5, the opening of the intake shield 32 (i.e., the first gas inlet 34) may be located radially outward from, for example, the largest diameter cryopanel of the cryopanel unit 20 (e.g., the top cryopanel 41). No opening as the first gas inlet 34 is provided radially inward from the largest diameter cryopanel of the cryopanel unit 20 (e.g., the top cryopanel 41).

[0058] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. [Industrial applicability]

[0059] This invention can be used in the field of cryopumps. [Explanation of Symbols]

[0060] 10 Cryopump, 12 Intake port, 16 Cryopump container, 16c Container bottom, 20 Cryopanel unit, 30 Radiation shield, 32 Intake port shield, 34 First gas inlet, 36 Second gas inlet.

Claims

1. A cryopump container having a cryopump air intake port, A radiation shield is cooled to a first cooling temperature and extends from the cryopump intake port into the cryopump container, A cryopanel unit is cooled to a second cooling temperature lower than the first cooling temperature and is arranged within the cryopump container so as to be surrounded by the radiation shield, The system comprises an intake shield that is cooled to the first cooling temperature and positioned at the cryopump intake port such that the cryopump panel unit is not visible from outside the cryopump, The radiation shield has a first gas inlet formed at the height between the air intake shield and the cryo panel unit, The cryopump container has a bottom on the side opposite to the cryopump air intake, The cryopanel unit comprises a plurality of cryopanels arranged in the axial direction of the cryopump, extending from the cryopump air intake to the bottom of the container, The plurality of cryopanels include a top cryopanel that is positioned closest to the cryopump intake port in the axial direction of the cryopump and facing the back surface of the intake port shield. The cryopump is characterized in that the intake shield is coupled to the radiation shield so as to completely close the end opening of the radiation shield on the cryopump intake side, and the intake shield does not have an opening for gas intake.

2. The cryopump according to claim 1, characterized in that the first gas inlet is located at an axial height between the intake shield and the top cryo panel.

3. The cryopump according to claim 1, characterized in that the axial distance from the intake shield to the top cryo panel is in the range of 30% to 70% of the axial distance from the intake shield to the bottom of the container.

4. The cryopump according to claim 1, characterized in that no other cryopump is provided between the top cryopump and the intake shield.

5. The cryopump according to claim 1, characterized in that the first gas inlet includes a plurality of openings formed in the upper end of the radiation shield adjacent to the cryopump intake port.

6. The cryopump according to claim 1, characterized in that the total area of ​​the first gas inlet is 10% or less of the area of ​​the cryopump air intake.

7. The cryopump according to claim 1, characterized in that the diameter of the top cryopanel is 80% or more of the diameter of the intake shield.

8. The cryopump according to any one of claims 1 to 7, characterized in that the radiation shield has a second gas inlet located at an axial height between the top cryo panel and the bottom of the container.

9. The radiation shield comprises an upper shield portion located on the side of the cryopump intake port and a lower shield portion located on the side of the container bottom, with the upper shield portion and the lower shield portion separated by a shield gap. The cryopump according to claim 8, characterized in that the second gas inlet includes a plurality of openings formed at the lower end of the upper part of the shield and the gap between the shields.

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