Cryopump

Abstract

To provide a cryopump that enables both improvement in productivity of a vacuum process device through shortening of a recovery time and compatibility with an existing vacuum process in the vacuum process device.SOLUTION: A cryopump 10 comprises a radiation shield 30, an intake port plate 32, and a skirt 33, which are thermally coupled to a first cooling stage 22 of a refrigerator 14, and a cryopanel unit 20 that is thermally coupled to a second cooling stage 24 of the refrigerator 14 and is disposed inside the radiation shield 30. The skirt 33 extends from an outer periphery of the intake port plate 32 into the radiation shield 30. A gas inlet 46 is formed between the intake port plate 32 and the radiation shield 30, and a frost accommodation space 38 is formed between the cryopanel unit 20 and the intake port plate 32. A gas flow path 48 for connecting the gas inlet 46 to the frost accommodation space 38 is formed between the skirt 33 and the radiation shield 30.SELECTED DRAWING: Figure 1

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 exhausts 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] As an example of the use of a cryopump, there is a vacuum process apparatus that executes a predetermined process on an object to be processed, such as a semiconductor wafer, in a vacuum environment in a vacuum chamber of a vacuum film forming apparatus such as a sputtering apparatus. During such a vacuum process, a gas required for the process is supplied to the vacuum chamber of the apparatus. By balancing the supply of the process gas to the vacuum chamber and the vacuum exhaust by the cryopump, the vacuum chamber can be maintained at an appropriate degree of vacuum for the vacuum process. During the interval between processes, the supply of the process gas is stopped, and the degree of vacuum of the vacuum chamber is restored by the cryopump to a desired degree of vacuum higher than that during the process. The time required for such restoration of the degree of vacuum is also called the recovery time (or pull-back time). The shorter the recovery time, the earlier the next process can be started, and the productivity of the vacuum process apparatus is increased. Therefore, it is desirable that the recovery time be as short as possible.

[0005] To shorten the recovery time, it is sufficient to increase the evacuation speed of the cryopump. As a generally recognized means for this, it is to increase the opening ratio of the cryopump intake port, that is, the ratio of the opening area to the total area of the intake port. Increasing the opening ratio of the cryopump intake port will increase the evacuation speed of the cryopump not only during the interval between processes but also during the process. Therefore, increasing the opening ratio can reduce the vacuum chamber pressure during the process. In some cases, the vacuum chamber pressure may deviate from the established pressure desired for the process. Such an unintended change in the process recipe can have an unexpected impact on the quality of the process. For example, in vacuum film formation, the pressure during the process affects the film thickness to be generated. In other words, while increasing the opening ratio of the cryopump intake port leads to the advantages of shortening the recovery time and thereby improving the productivity of the vacuum process apparatus, there is a concern that it may also bring about the disadvantage of incompatibility with the existing vacuum process.

[0006] One of the exemplary objects of an aspect of the present invention is to provide a cryopump that enables both an improvement in the productivity of a vacuum process apparatus through shortening of the recovery time and compatibility with an existing vacuum process in the vacuum process apparatus.

Means for Solving the Problem

[0007] According to an aspect of the present invention, a cryopump includes a cryopump container that defines a cryopump intake port, a refrigerator installed in the cryopump container and including a first cooling stage and a second cooling stage that is cooled to a temperature lower than that of the first cooling stage, a radiation shield thermally coupled to the first cooling stage and extending axially from the cryopump intake port into the cryopump container, an intake port plate thermally coupled to the first cooling stage and extending along a plane perpendicular to the axial direction at the cryopump intake port, the intake port plate having a gas inlet formed therebetween and the radiation shield, a cryopanel unit thermally coupled to the second cooling stage and disposed inside the radiation shield, the cryopanel unit having a frost accommodation space formed therebetween and the intake port plate, and a skirt thermally coupled to the first cooling stage and extending from the outer periphery of the intake port plate into the radiation shield, the skirt having a gas flow path formed therebetween and the radiation shield for connecting the gas inlet to the frost accommodation space.

Advantages of the Invention

[0008] According to the present invention, it is possible to provide a cryopump that enables both an improvement in the productivity of a vacuum process apparatus through shortening of the recovery time and compatibility with existing vacuum processes in the vacuum process apparatus.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0010] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions are omitted as appropriate. The scales and shapes of the respective parts shown are set for convenience in order to facilitate the explanation, and are not to be construed in a limited sense unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

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

[0012] The cryopump 10 is attached to a vacuum chamber 100 of, for example, an ion implantation apparatus, a sputtering apparatus, a vapor deposition apparatus, or other vacuum process apparatuses, and is used to increase the degree of vacuum inside the vacuum chamber 100 to a level required for a desired vacuum process. The cryopump 10 has a cryopump intake port 12 for receiving the gas to be evacuated from the vacuum chamber 100. The gas enters the internal space of the cryopump 10 through the cryopump intake port 12.

[0013] In the following, in order to clearly show the positional relationship of the components of the cryopump 10, the terms "axial direction" and "radial direction" may be used. The axial direction of the cryopump 10 represents the direction passing through the cryopump intake port 12 (i.e., the direction along the central axis C in the figure), and the radial direction represents the direction along the cryopump intake port 12 (the direction perpendicular to the central axis C). For the sake of convenience, being relatively close to the cryopump intake port 12 in the axial direction may be referred to as "upper", and being relatively far as "lower". That is, being relatively far from the bottom of the cryopump 10 may be referred to as "upper", and being relatively close as "lower". Regarding the radial direction, being close to the center of the cryopump intake port 12 (the central axis C in the figure) may be referred to as "inner", and being close to the periphery of the cryopump intake port 12 as "outer". Note that such expressions have nothing to do with the arrangement when the cryopump 10 is attached to the vacuum chamber 100. For example, the cryopump 10 may be attached to the vacuum chamber 100 with the cryopump intake port 12 facing downward in the vertical direction.

[0014] Also, the direction around the central axis C may be referred to as the "circumferential direction". The circumferential direction is the second direction along the circumference of the cryopump intake port 12 and is the tangential direction perpendicular to the radial direction.

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

[0016] The refrigerator 14 is an ultra-low temperature refrigerator such as a Gifford-McMahon refrigerator (so-called GM refrigerator). The refrigerator 14 is a two-stage refrigerator and includes 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 be referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0017] In addition, the refrigerator 14 includes a refrigeration structure portion 21 that structurally supports the second cooling stage 24 on the first cooling stage 22 and structurally supports the first cooling stage 22 on the room temperature portion 26 of the refrigerator 14. Therefore, the refrigeration structure portion 21 includes a first cylinder 23 and a second cylinder 25 that extend coaxially along the radial direction of the cryopump 10. The first cylinder 23 connects the room temperature portion 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 formed of a high thermal conductivity metal material such as copper (e.g., pure copper), and the first cylinder 23 and the second cylinder 25 are formed of another metal material such as stainless steel. The room temperature portion 26, the first cylinder 23, the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are arranged linearly in this order in a row.

[0018] Inside each of the first cylinder 23 and the second cylinder 25, a first displacer and a second displacer (not shown) are reciprocally arranged. A first regenerator and a second regenerator (not shown) are incorporated in the first displacer and the second displacer, respectively. Further, the room temperature section 26 has a drive mechanism (not shown) for reciprocating the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas so as to periodically repeat the supply and discharge of the working gas (for example, helium) into the refrigerator 14.

[0019] The refrigerator 14 is connected to a compressor (not shown) of the 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. It should be noted that 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 cryopump intake port 12 is defined by the front end of the cryopump container 16. The cryopump container 16 includes an intake flange 16a that extends radially outward from its front end. The intake flange 16a is provided over the entire circumference of the cryopump container 16. The cryopump 10 is attached to the vacuum chamber 100 of the vacuum processing apparatus using the intake flange 16a. Note that the cryopump 10 may be attached to the vacuum chamber 100 via a gate valve (not shown).

[0023] Further, the cryopump container 16 has a container body portion 16b that extends axially from the intake flange 16a, a container bottom portion 16c that closes the container body portion 16b on the side opposite to the cryopump intake port 12, and a refrigerator housing cylinder 16d that extends laterally between the intake flange 16a and the container bottom portion 16c. The end of the refrigerator housing cylinder 16d on the side opposite to the container body portion 16b is attached to the room temperature portion 26 of the refrigerator 14, whereby the low temperature portion 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) is disposed in the cryopump container 16 in a non-contact manner with the cryopump container 16. The first cylinder 23 is disposed in the refrigerator housing cylinder 16d, and the first cooling stage 22, the second cylinder 25, and the second cooling stage 24 are disposed in the container body portion 16b. The first stage cryopanel 18 and the cryopanel unit 20 are also disposed in the container body portion 16b.

[0024] The first-stage cryopanel 18 includes a radiation shield 30, an air inlet plate 32, and a skirt 33, and surrounds the cryopanel unit 20. The first-stage cryopanel 18 provides a cryogenic surface for protecting the cryopanel unit 20 from the radiant heat from the outside of the cryopump 10 or the cryopump container 16. The first-stage cryopanel 18 is thermally coupled to the first cooling stage 22. Thus, the first-stage cryopanel 18 is cooled to the first cooling temperature. Therefore, a gas (such as moisture) that condenses at the first cooling temperature is trapped on its surface. The first-stage cryopanel 18 is generally formed of a high thermal conductivity metal material such as copper (e.g., pure copper), and if necessary, the surface may be coated with a metal layer such as nickel.

[0025] The first-stage cryopanel 18 has a gap with the cryopanel unit 20, and the first-stage cryopanel 18 is not in contact with the cryopanel unit 20. The first-stage cryopanel 18 is also not in contact with the cryopump container 16.

[0026] The radiation shield 30 is provided to protect the cryopanel unit 20 from the radiant heat of the cryopump container 16. The radiation shield 30 extends axially in a cylindrical shape (e.g., a circular cylinder shape) from the cryopump air inlet 12 into the cryopump container 16. The radiation shield 30 is between the cryopump container 16 and the cryopanel unit 20 and surrounds the cryopanel unit 20. The radiation shield 30 has a diameter slightly smaller than that of the cryopump container 16, and a shield outer gap 31 is formed between the radiation shield 30 and the cryopump container 16. Thus, the radiation shield 30 is not in contact with the cryopump container 16.

[0027] The first cooling stage 22 of the refrigerator 14 is directly attached to the outer surface of the side portion of the radiation shield 30. Thus, the radiation shield 30 is thermally coupled to the first cooling stage 22 and is therefore cooled to the first cooling temperature. Note that the radiation shield 30 may be attached to the first cooling stage 22 via an appropriate heat transfer member. Further, the second cooling stage 24 and the second cylinder 25 of the refrigerator 14 are inserted into the radiation shield 30 from the side portion of the radiation shield 30.

[0028] In this embodiment, the radiation shield 30 includes a shield upper portion 30a disposed close to the cryopump intake port 12 and a shield lower portion 30b disposed away from the cryopump intake port 12. The shield upper portion 30a is disposed on the cryopump intake port 12 side with respect to the second cooling stage 24 of the refrigerator 14, and the shield lower portion 30b is disposed on the container bottom portion 16c side with respect to the second cooling stage 24. The shield upper portion 30a is a cylinder with both ends open and surrounds the upper portion of the cryopanel unit 20. The shield lower portion 30b is a bottomed cylinder with its upper end open and its lower end closed, and surrounds the lower portion of the cryopanel unit 20. The lower end of the shield upper portion 30a and the upper end of the shield lower portion 30b are generally at the same height. The diameter of the shield upper portion 30a is slightly smaller than the diameter of the shield lower portion 30b, and the shield outer gap 31 is wider outside the shield upper portion 30a than outside the shield lower portion 30b.

[0029] The intake port plate 32 is provided at the cryopump intake port 12 in order to protect the cryopanel unit 20 from radiant heat from a heat source outside the cryopump 10 (for example, a heat source in the vacuum chamber 100 to which the cryopump 10 is attached). The intake port plate 32 is thermally coupled to the first cooling stage 22 via the radiation shield 30 and is cooled to the first cooling temperature, like the radiation shield 30.

[0030] The intake port plate 32 extends along a plane perpendicular to the axial direction at the cryopump intake port 12. The intake port plate 32 is, for example, a single disk arranged perpendicular to the central axis C so as to cross the cryopump intake port 12, and its center is located on or near the central axis C of the cryopump 10. The diameter of the intake port plate 32 is smaller than the diameter of the shield upper part 30a, and a gap is formed between the intake port plate 32 and the shield upper part 30a as will be described later. In this example, the entire surface of the intake port plate 32 is flat and has no inclined surface.

[0031] In the illustrated example, the intake port plate 32 is arranged in the axial direction at the same height as the front end of the cryopump container 16, that is, the intake port flange 16a (for example, between the upper surface and the lower surface of the intake port flange 16a). The intake port plate 32 may be arranged axially above the front end of the cryopump container 16, that is, on the vacuum chamber 100 side, or may be arranged axially below the front end of the cryopump container 16, that is, on the cryopanel unit 20 side.

[0032] The intake port plate 32 is coupled to the upper end of the shield upper part 30a. For example, the intake port plate 32 may be attached to a joint block (not shown) at its outer peripheral portion. The joint block is a convex portion that protrudes radially inward at the upper end of the shield upper part 30a and is formed at equal intervals in the circumferential direction (for example, every 90°). As shown in FIG. 2, the intake port plate 32 has plate attachment portions 32a at its outer periphery in an arrangement corresponding to the joint blocks. The plate attachment portions 32a are fixed to the joint blocks using fastening members 32b such as bolts or by other appropriate methods such as welding.

[0033] The cryopanel unit 20 includes a plurality of cryopanels (41, 42, 43) arranged in the axial direction. Each of these cryopanels is thermally coupled to the second cooling stage 24 and is cooled to a second cooling temperature lower than the first cooling temperature. The cryopanel unit 20 is disposed inside the radiation shield 30 within the cryopump container 16 and below the intake port plate 32 in the axial direction.

[0034] For the sake of convenience in explanation, the part of these cryopanels closest to the cryopump intake port 12 is referred to as the top cryopanel 41. Thus, the top cryopanel 41 is disposed closest to the intake port plate 32 in the axial direction in the cryopanel unit 20. The front surface of the top cryopanel 41 faces the back surface of the intake port plate 32, and no other cryopanels are provided between the top cryopanel 41 and the intake port plate 32. The top cryopanel 41 is, for example, a disk-shaped member disposed perpendicular to the axial direction, and its center is located on or near the central axis C of the cryopump 10. The top cryopanel 41 has a flat entire surface and no inclined surface.

[0035] In order to condense more gas, the top cryopanel 41 is relatively large, and the diameter of the top cryopanel 41 may be, for example, 70% or more or 80% or more of the diameter of the radiation shield 30 (for example, the shield upper part 30a). Also, the diameter of the top cryopanel 41 may be 98% or less or 90% or less of the diameter of the radiation shield 30 (for example, the shield upper part 30a). Thereby, it is possible to surely keep the top cryopanel 41 non-contact with the radiation shield 30.

[0036] The top cryopanel 41 may be disposed generally near the middle in the axial direction within the container body 16b of the cryopump container 16. The central portion of the top cryopanel 41 may be directly attached to the upper surface of the second cooling stage 24 of the refrigerator 14. The axial distance from the intake port plate 32 to the top cryopanel 41 may be in the range of, for example, 30 to 70%, or 40 to 60% of the axial distance from the intake port plate 32 to the container bottom 16c. In this way, a relatively wide empty space is formed axially between the cryopanel unit 20 (i.e., the top cryopanel 41) and the intake port plate 32. This space can be utilized as a frost storage space 38 for accommodating the condensation layer of the exhaust gas to be condensed on the top cryopanel 41.

[0037] 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 connection cryopanel 44. In this example, one intermediate cryopanel 42 and two lower cryopanels 43 are provided. The axial interval between the intermediate cryopanel 42 and the lower cryopanel 43 is wider than the axial interval between the lower cryopanels 43, whereby a relatively wide condensation layer accommodation space may be formed between the intermediate cryopanel 42 and the lower cryopanel 43. This space can be utilized as a frost storage space 39 for the condensation layer that condenses on the lower cryopanel 43.

[0038] As an example, the diameters of both the intermediate cryopanel 42 and the lower cryopanel 43 may be smaller than the diameter of the top cryopanel 41. Also, the diameter of the intermediate cryopanel 42 may be smaller than the diameter of the lower cryopanel 43.

[0039] In the illustrated example, the intermediate cryopanel 42 and the lower cryopanel 43 each have a frustum - shaped configuration, having a flat disc - shaped central portion and an outer peripheral portion that slopes downward in the radial direction. The centers of these cryopanels are located on or near the central axis C of the cryopump 10. In the axial direction, the intermediate cryopanel 42 is located below the top cryopanel 41 and above the second cooling stage 24, and the lower cryopanel 43 is located below the second cooling stage 24. For example, the intermediate cryopanel 42 may be sandwiched between the top cryopanel 41 and the second cooling stage 24. Alternatively, the intermediate cryopanel 42 may be located at the same height as the second cooling stage 24 (e.g., between the upper and lower surfaces of the second cooling stage 24).

[0040] The connecting cryopanel 44 extends from the second cooling stage 24 to the lower cryopanel 43 and thermally couples the lower cryopanel 43 to the second cooling stage 24. The connecting cryopanel 44 may be a set of elongated plate - shaped members that extend 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.

[0041] Each cryopanel (41, 42, 43) constituting the cryopanel unit 20 is generally formed of a high - thermal - conductivity metal material such as copper (e.g., pure copper), and if necessary, the surface may be coated with a metal layer such as nickel. Also, an adsorbent (e.g., activated carbon) for capturing a non - condensable gas (e.g., hydrogen) by adsorption may be provided on at least a part 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.

[0042] Note that the specific configuration of the cryopanel unit 20 is not limited to the above. For example, an additional cryopanel may be provided between the top cryopanel 41 and the intake port plate 32, and such an additional cryopanel may have a smaller diameter than the top cryopanel 41. The top cryopanel 41 may have an inclined surface that faces downward (or upward) on the outer peripheral portion in the radial direction. At least one of the intermediate cryopanel 42 and the lower cryopanel 43 (for example, the lowermost cryopanel) may have a larger diameter than the top cryopanel 41. The intermediate cryopanel 42 and / or the lower cryopanel 43 may be a disk-shaped plate without an inclined surface, 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 a rectangle or a polygon.

[0043] A first gas inlet 34 for taking gas from the outside to the inside of the cryopump 10 is formed in the first-stage cryopanel 18. The first gas inlet 34 is at least one opening formed in the intake port plate 32. The opening is a hole that penetrates the intake port plate 32, and thus, a gas flow from the vacuum chamber 100 to the frost storage space 38 through the first gas inlet 34 is allowed.

[0044] At least one opening of the intake port plate 32 as the first gas inlet 34 is formed at the central portion of the intake port plate 32. The central portion of the intake port plate 32 may be in a range of, for example, 3 / 4 or less, or 1 / 2 or less, or 1 / 4 or less of the diameter of the cryopump intake port 12. No opening as the first gas inlet 34 is formed at the outer peripheral portion of the intake port plate 32 that is outside the central portion of such an intake port plate 32.

[0045] As shown in the figure, a large number of openings may be formed in the intake port plate 32. As an example, FIG. 2 shows 6×6 = 36 openings. These openings may be regularly arranged on the intake port plate 32, for example, in a lattice pattern as shown in the figure. The openings may be provided at equal intervals in both the radial direction and the circumferential direction. The shape of the openings is, for example, circular, but is not limited thereto, and may have other shapes such as rectangular or slotted.

[0046] In addition, a second gas inlet 36 for taking gas into the cryopump 10 from the outside to the inside is also formed in the first-stage cryopanel 18. The second gas inlet 36 is a gap between the shield upper part 30a and the shield lower part 30b in the radiation shield 30 having the above-described divided structure (this is also referred to as a shield gap in this document).

[0047] The axial distance from the intake port plate 32 to the shield gap is larger than the axial distance from the intake port plate 32 to the top cryopanel 41. The second gas inlet 36 is located axially below the top cryopanel 41, that is, it is formed at the axial height between the top cryopanel 41 and the container bottom 16c. In this example, the second gas inlet 36 is formed at the axial height between the intermediate cryopanel 42 and the lower cryopanel 43. The second gas inlet 36 may be formed between the top cryopanel 41 and the intermediate cryopanel 42. Therefore, gas flow from the vacuum chamber 100 through the shield outer gap 31 and the second gas inlet 36 to the frost storage space 39 below the top cryopanel 41 is allowed.

[0048] Note that the shield gap between the shield upper part 30a and the shield lower part 30b may be set at an arbitrary position in the axial direction, or may be provided at the axial height between the top cryopanel 41 and the intake port plate 32. In this case, gas flow from the vacuum chamber 100 through the second gas inlet 36 to the frost storage space 38 above the top cryopanel 41 is allowed.

[0049] In this embodiment, a skirt 33 is provided on the intake port plate 32. The skirt 33 extends from the outer periphery of the intake port plate 32 into the radiation shield 30. The skirt 33 extends in the axial direction, that is, parallel to the radiation shield 30.

[0050] The axial length L of the skirt 33 is smaller than the axial distance from the intake port plate 32 to the top cryopanel 41. For example, the axial length L of the skirt 33 may be smaller than 3 / 4, or 1 / 2, or 1 / 4 of the axial distance from the intake port plate 32 to the top cryopanel 41. Thus, the skirt 33, together with the intake port plate 32, is disposed relatively above the frost storage space 38. The skirt 33, like the radiation shield 30 and the intake port plate 32, is not in physical contact with the cryopanel unit 20 such as the top cryopanel 41.

[0051] Since the second gas inlet 36 is provided axially below the top cryopanel 41 as described above, the axial length L of the skirt 33 is smaller than the axial distance from the intake port plate 32 to the second gas inlet 36. This helps to increase the diameter of the top cryopanel 41 and thus the gas storage amount of the cryopump 10. If, for example, the skirt 33 extended axially below the top cryopanel 41, the top cryopanel 41 would be surrounded by the skirt 33. In order to prevent physical contact between the top cryopanel 41 and the skirt 33, the diameter of the top cryopanel 41 would have to be made smaller than the diameter of the skirt 33. Miniaturization of the top cryopanel 41 leads to a decrease in the gas storage amount of the cryopump 10 and is therefore desirably avoided.

[0052] The skirt 33 is an annulus or a short cylinder that borders the intake port plate 32, and together with the intake port plate 32, it can also be said to form a circular-shaped tray. Such an intake port plate 32 with a skirt 33 is arranged at the cryopump intake port 12 so as to cover most of the open area inside the upper end of the radiation shield 30. In FIG. 2, for the sake of understanding, the skirt 33 is shown by a dashed line.

[0053] The diameters of the intake port plate 32 and the skirt 33 are smaller than the inner diameter of the radiation shield 30 (for example, the shield upper part 30a). However, so that the intake port plate 32 can occupy most of the open area inside the upper end of the radiation shield 30, the diameters of the intake port plate 32 and the skirt 33 may be, for example, 70% or more, or 80% or more, or 90% or more of the inner diameter of the radiation shield 30 (for example, the shield upper part 30a).

[0054] Therefore, in addition to the first gas inlet 34 and the second gas inlet 36, as shown in FIGS. 1 and 2, a gas inlet 46 as a further gas inlet is formed between the intake port plate 32 and the radiation shield 30 (more specifically, the upper end of the shield upper part 30a). The gas inlet 46 is a radial gap between the radiation shield 30 and the intake port plate 32. Also, a gas flow path 48 is formed between the skirt 33 and the radiation shield 30. The gas flow path 48 is a radial gap between the radiation shield 30 and the skirt 33. The gas inlet 46 is connected to the frost storage space 38 above the top cryopanel 41 through the gas flow path 48. Thus, a gas flow from the vacuum chamber 100 to the frost storage space 38 through the gas inlet 46 and the gas flow path 48 is allowed.

[0055] In this way, the cryopump 10 has three paths for guiding the gas to be exhausted from the vacuum chamber 100 to the cryopanel unit 20 in the cryopump 10. The first path is the path from the first gas inlet 34 to the frost storage space 38. The second path is from the outside shield gap 31, through the second gas inlet 36, to the frost storage space 39. The third path is from the gas inlet 46, through the gas flow path 48, to the frost storage space 38. These three paths contribute to the improvement of the exhaust speed of the cryopump 10.

[0056] In the illustrated example, the outside shield gap 31 is wider than the gas flow path 48. That is, as shown in FIG. 1, the radial distance R1 from the radiation shield 30 to the cryopump container 16 at the cryopump intake port 12 is larger than the radial distance R2 from the skirt 33 to the radiation shield 30 in the gas flow path 48. Such a dimensional setting between the outside shield gap 31 and the gas flow path 48 has been confirmed by the verification of the inventor to be effective in shortening the recovery time of the cryopump 10.

[0057] The axial length L of the skirt 33 may be within 8 times the radial distance R2 from the skirt 33 to the radiation shield 30. In this way, it has been confirmed by the verification of the inventor to be effective in shortening the recovery time of the cryopump 10.

[0058] Also, as shown, the diameter of the skirt 33 may be smaller than the diameter of the top cryopanel 41. Since the skirt 33 has the same diameter as the intake port plate 32, the diameter of the intake port plate 32 may also be smaller than the diameter of the top cryopanel 41. In this way, the gas inlet 46 and the gas flow path 48 can be made relatively wide. This helps to increase the opening ratio of the cryopump intake port 12 and improve the exhaust speed of the cryopump 10. Also, since the area of the top cryopanel 41 can be made relatively large, the gas storage capacity of the cryopump 10 can be increased.

[0059] The operation of the cryopump 10 configured as described above will be explained below. FIG. 3 is a schematic diagram showing the cryopump 10 during vacuum evacuation operation according to the embodiment. When the cryopump 10 operates, first, before the operation, the inside of the vacuum chamber 100 is roughly evacuated to a cryopump operation start pressure of, for example, about 1 Pa by another appropriate roughing pump (not shown). Then, the cryopump 10 is operated. By driving 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-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.

[0060] The intake port plate 32 cools the gas flying from the vacuum chamber 100 toward the cryopump 10. On the surface of the intake port plate 32, a gas whose vapor pressure is sufficiently low (for example, 10 -8 Pa or less) condenses at the first cooling temperature. This gas may be referred to as the first type of gas. The first type of gas is, for example, water vapor. In this way, the intake port plate 32 can exhaust the first type of gas.

[0061] As shown by the solid arrows in FIG. 3, a part of the gas enters the cryopump 10 through any of the above three paths. That is, the gas can enter the frost storage space 38 through the first gas inlet 34 from the vacuum chamber 100. Also, the gas can enter from the vacuum chamber 100 into the gas inlet 46 and further enter the frost storage space 38 through the gas flow path 48. Further, the gas can enter from the vacuum chamber 100 into the shield outer gap 31 and further enter the frost storage space 39 through the second gas inlet 36. At this time, since the radiation shield 30 and the skirt 33 are also cooled to the first cooling temperature, the first type of gas can be condensed and exhausted on their surfaces. A gas whose vapor pressure is not sufficiently low at the first cooling temperature can enter the radiation shield 30 through these paths.

[0062] The gas entering from the first gas inlet 34 and the gas inlet 46 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 bottom cryopanel 43. On the surfaces of these cryopanels, a gas whose vapor pressure is sufficiently low (for example, 10 -8 Pa or less) condenses at the second cooling temperature. This gas may be referred to as a second type of gas. The second type of gas is, for example, argon (Ar). In this way, the cryopanel unit 20 can exhaust the second type of gas.

[0063] For understanding, FIG. 3 shows a condensation layer 50 of the gas condensed on the top cryopanel 41. As shown in the drawing, the condensation layer 50 can form a hemispherical ice block in the frost storage space 38. In FIG. 3, for the sake of convenience, the illustration of other condensation layers, such as the condensation layer on the bottom cryopanel 43, is omitted.

[0064] In this embodiment, the skirt 33, together with the intake port plate 32, is disposed axially above the frost storage space 38. For example, the axial length L of the skirt 33 may be smaller than, for example, 1 / 2 of the axial distance from the intake port plate 32 to the top cryopanel 41 as described above. In this way, a relatively large axial gap can be formed between the skirt 33 and the frost storage space 38, and a larger condensation layer 50 can be condensed on the top cryopanel 41. The gas storage amount of the cryopump 10 can be increased.

[0065] Further, since the first gas inlet 34 is formed at the center of the intake port plate 32, the condensation layer 50 can be evenly grown on the top cryopanel 41 together with the gas inlet 46 formed around the intake port plate 32.

[0066] Gases whose vapor pressure is not sufficiently low at the second cooling temperature are adsorbed by the adsorbent on the cryopanel unit 20. This gas may be referred to as a third type of gas. The third type of gas is, for example, hydrogen (H2). Thus, the cryopanel unit 20 can exhaust the third type of gas. Therefore, the cryopump 10 can exhaust various gases by condensation or adsorption, and bring the degree of vacuum in the vacuum chamber 100 to a desired level.

[0067] FIG. 4 is a diagram schematically showing exemplary pressure changes during the operation of a vacuum process apparatus (e.g., a PVD apparatus) equipped with the cryopump 10 according to the embodiment. FIG. 4 schematically shows how the pressure in the vacuum chamber of the vacuum process apparatus varies during the vacuum process (e.g., the PVD process) and during the interval between processes.

[0068] During the process, a process gas is supplied to the vacuum chamber. Due to the balance between the supply of the process gas to the vacuum chamber and the vacuum exhaust by the cryopump, the pressure in the vacuum chamber is maintained at a vacuum level appropriate for the vacuum process. The degree of vacuum during the process may be, for example, in the intermediate flow region on the order of 10 -1 Pa. During the interval between processes, since the supply of the process gas is stopped, the cryopump restores the degree of vacuum in the vacuum chamber to a desired degree of vacuum higher than during the process. During the interval, for example, the degree of vacuum is restored to the molecular flow region on the order of 10 -5 Pa to 10 -6 Pa. During the interval, preparations for the process are made, such as removing a processed substrate (e.g., a semiconductor wafer) from the vacuum chamber and loading a new substrate into the vacuum chamber.

[0069] As described at the beginning of this book, the time required to restore the degree of vacuum during the interval between processes is also called the recovery time (or pull-back time). In FIG. 4, the recovery time is indicated by the symbol Tr. The shorter the recovery time Tr, the earlier the next process can be started, and the higher the productivity of the vacuum process apparatus.

[0070] Therefore, it is desirable that the recovery time Tr be as short as possible. To shorten the recovery time Tr, the evacuation speed of the cryopump may be increased. One generally recognized means for this is to increase the opening ratio of the cryopump intake port, that is, the ratio of the opening area to the total area of the intake port.

[0071] FIGS. 5(A) and 5(B) are schematic views showing the first-stage cryopanel of a cryopump according to a comparative example. In Comparative Example 1 shown in FIG. 5(A), the first-stage cryopanel 18A has a radiation shield 30A and an intake port shield 32A that closes the opening of the radiation shield 30A. However, a large number of small holes for taking in gas into the radiation shield 30A are formed in the intake port shield 32A. Comparative Example 1 is a typical example of the first-stage cryopanel in an existing cryopump.

[0072] In Comparative Example 2 shown in FIG. 5(B), the first-stage cryopanel 18B has a radiation shield 30B and an intake port shield 32B disposed at the center of the opening of the radiation shield 30B. A large number of small holes for taking in gas into the radiation shield 30B are formed in the intake port shield 32B. Since the intake port shield 32B is disposed at the center of the opening of the radiation shield 30B, a gap 46B is formed between the intake port shield 32B and the radiation shield 30B. Thus, in Comparative Example 2 shown in FIG. 5(B), the opening ratio of the cryopump intake port is higher than that in Comparative Example 1 shown in FIG. 5(A). Gas can be taken into the radiation shield 30A using not only the small holes of the intake port shield 32B but also this gap. Comparative Example 2 is based on the consideration of the present inventor and is an example of a first-stage cryopanel capable of achieving a higher evacuation speed than Comparative Example 1.

[0073] FIG. 6 is a schematic diagram showing the exhaust speed of the cryopump according to the comparative examples of FIGS. 5(A) and 5(B). In FIG. 6, for Comparative Example 1 shown in FIG. 5(A) and Comparative Example 2 shown in FIG. 5(B), the change in the exhaust speed with respect to the pressure (vacuum degree) is shown from the intermediate flow region to the molecular flow region. As shown in FIG. 6, generally, the exhaust speed of the cryopump increases as the pressure increases in the intermediate flow region. On the other hand, in the molecular flow region, the exhaust speed is generally constant and does not depend on the pressure. This is because the exhaust speed of the cryopump in the molecular flow region is determined by the opening area of the cryopump intake port. When comparing the exhaust speeds of Comparative Example 1 and Comparative Example 2, as described above, since the opening ratio of the cryopump intake port in Comparative Example 2 is higher than that in Comparative Example 1, the exhaust speed of Comparative Example 2 is higher than that of Comparative Example 1 from the intermediate flow region to the molecular flow region.

[0074] Therefore, assuming that these cryopumps according to the comparative examples are applied to a vacuum process apparatus, the cryopump of Comparative Example 2 can provide a higher exhaust speed than Comparative Example 1 both during the process and during the interval between processes. The high exhaust speed during the interval can lead to a reduction in the recovery time and thus an improvement in the throughput of the vacuum process apparatus.

[0075] However, an increase in the exhaust speed during the process can reduce the vacuum chamber pressure during the process. In some cases, the vacuum chamber pressure may deviate from the predetermined pressure desired for the process. Such an unintended change in the process recipe can have an unexpected impact on the quality of the process. For example, in vacuum film deposition, the pressure during the process affects the film thickness to be formed. In other words, while an increase in the opening ratio of the cryopump intake port leads to the advantages of shortening the recovery time and thereby improving the productivity of the vacuum process apparatus, there is a concern that it may also bring about the disadvantage of incompatibility with the existing vacuum process.

[0076] Therefore, in the embodiment, in addition to the gas inlet 46 around the intake port plate 32, a skirt 33 is provided on the intake port plate 32, and a gas flow path 48 connecting the gas inlet 46 to the frost storage space 38 is formed between the skirt 33 and the radiation shield 30. The skirt 33 enables different adjustments of the conductance of the cryopump inlet 12 in the intermediate flow region and the molecular flow region.

[0077] In the intermediate flow region, since the gas behaves closer to viscous flow than in the molecular flow region, the skirt 33 reduces the conductance of the cryopump inlet 12 compared to the case where it is not present on the intake port plate 32. The longer the axial length L of the skirt 33, the smaller the conductance.

[0078] Therefore, in the intermediate flow region, the skirt 33 can cancel out the increase in conductance obtained by the increase in the opening ratio of the cryopump inlet 12 due to the gas inlet 46. That is, the conductance of the cryopump inlet 12 having both the gas inlet 46 and the skirt 33 can be maintained equivalent to the case where they are not provided on the cryopump inlet 12 (for example, Comparative Example 1).

[0079] On the other hand, in the molecular flow region, the conductance of the cryopump inlet 12 is determined according to the opening area of the cryopump inlet 12. Since the skirt 33 extends parallel to the radiation shield 30, it does not substantially affect the flow path cross-sectional area of the gas flow path 48. The reduction in conductance due to the skirt 33 in the molecular flow region is less than the reduction in conductance due to the skirt 33 in the intermediate flow region. That is, the influence of the skirt 33 in the molecular flow region is small.

[0080] Therefore, in the molecular flow region, even if the skirt 33 is provided on the intake port plate 32, the conductance of the cryopump intake port 12 increases due to the effect of the increased opening ratio of the cryopump intake port 12 by the gas inlet 46. That is, the conductance of the cryopump intake port 12 having both the gas inlet 46 and the skirt 33 is larger than when they are not provided on the cryopump intake port 12 (for example, Comparative Example 1).

[0081] FIG. 7 is a schematic diagram showing the exhaust speed of the cryopump 10 according to the embodiment. Similar to FIG. 6, in FIG. 7, the change in the exhaust speed with respect to the pressure (vacuum degree) is shown from the intermediate flow region to the molecular flow region. In FIG. 7, the exhaust speed of Comparative Example 1 described above is shown by a broken line, and the exhaust speed of the cryopump 10 according to the embodiment is shown by a solid line.

[0082] The conductance of the cryopump intake port 12 is a main factor that determines the exhaust speed of the cryopump 10. Therefore, the cryopump 10 according to the embodiment can increase the exhaust speed compared to the existing cryopumps such as Comparative Example 1 in the molecular flow region. That is, the cryopump 10 can provide a higher exhaust speed compared to Comparative Example 1 during the interval between processes in the vacuum process apparatus. Further, the cryopump 10 according to the embodiment can match the exhaust speed with the existing cryopumps such as Comparative Example 1 in the intermediate flow region.

[0083] Therefore, according to the embodiment, it is possible to provide a cryopump 10 that enables both improvement in the productivity of the vacuum process apparatus through shortening of the recovery time and compatibility with the existing vacuum processes in the vacuum process apparatus.

[0084] The above is the description of the present invention based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above-described embodiments, various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention. The various features described in connection with one embodiment are also applicable to other embodiments. The new embodiments resulting from the combination have the effects of the respective embodiments being combined.

[0085] In the above-described embodiment, the intake port plate 32 has at least one opening as the first gas inlet 34 at the central portion of the intake port plate 32. Together with or instead of this, the first gas inlet 34 may be formed at the outer peripheral portion of the intake port plate 32. Further, in an embodiment, the intake port plate 32 may not have an opening as the first gas inlet 34.

[0086] In the above-described embodiment, the radiation shield 30 is composed of a plurality of divided parts and has a shield upper portion 30a and a shield lower portion 30b. Instead of this, the radiation shield 30 may be a single component extending from the cryopump intake port 12 to the bottom 16c of the container. The second gas inlet 36 may be at least one opening formed in such a single component.

[0087] In the above-described embodiment, the skirt 33 extends parallel to the radiation shield 30. Instead of this, in an embodiment, the skirt 33 may extend downwardly inclined radially outward (or radially inward) from the outer periphery of the intake port plate 32.

[0088] The above is the description of the present invention based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above-described embodiments, various design changes are possible, various modifications are possible, and such modifications are also within the scope of the present invention.

Description of Reference Numerals

[0089] 10 Cryopump, 12 Cryopump air inlet, 14 Refrigerator, 16 Cryopump container, 20 Cryopanel unit, 22 First cooling stage, 24 Second cooling stage, 30 Radiation shield, 30a Shield upper part, 30b Shield lower part, 32 Air inlet plate, 33 Skirt, 38, 41 Top cryopanel, 46 Gas inlet, 48 Gas flow path.

Claims

1. A cryopump container that defines a cryopump intake port, a refrigerator installed in the cryopump container and including a first cooling stage and a second cooling stage cooled to a temperature lower than that of the first cooling stage, a radiation shield thermally coupled to the first cooling stage and extending axially from the cryopump intake port into the cryopump container, an intake port plate thermally coupled to the first cooling stage and extending along a plane perpendicular to the axial direction at the cryopump intake port, and a gas inlet is formed between the intake port plate and the radiation shield, a cryopanel unit thermally coupled to the second cooling stage and disposed inside the radiation shield, and a frost storage space is formed between the cryopanel unit and the intake port plate, a skirt thermally coupled to the first cooling stage and extending from the outer periphery of the intake port plate into the radiation shield, and a gas flow path connecting the gas inlet to the frost storage space is formed between the skirt and the radiation shield. A cryopump characterized by comprising.

2. The cryopanel unit includes a top cryopanel disposed closest to the intake port plate in the axial direction in the cryopanel unit, The cryopump according to claim 1, wherein an axial length of the skirt is smaller than an axial distance from the intake port plate to the top cryopanel.

3. The cryopump according to claim 2, wherein an axial length of the skirt is smaller than 1 / 2 of an axial distance from the intake port plate to the top cryopanel.

4. The cryopump according to claim 2, wherein a diameter of the skirt is smaller than a diameter of the top cryopanel.

5. The cryopump according to claim 1, wherein the skirt extends parallel to the radiation shield.

6. The cryopump according to claim 1, wherein a radial distance from the radiation shield to the cryopump container at the cryopump intake port is larger than a radial distance from the skirt to the radiation shield in the gas flow path.

7. The radiation shield includes an upper shield portion disposed close to the cryopump intake port and a lower shield portion disposed away from the cryopump intake port, and the upper shield portion and the lower shield portion are disposed with a shield gap therebetween. The cryopump according to claim 1, characterized in that the axial length of the skirt is smaller than the axial distance from the intake port plate to the shield gap.

8. The cryopanel unit includes a top cryopanel disposed closest to the intake port plate in the cryopanel unit. The cryopump according to claim 7, characterized in that the axial distance from the intake port plate to the shield gap is larger than the axial distance from the intake port plate to the top cryopanel.

9. The cryopump according to claim 1, characterized in that the intake port plate has at least one opening.

10. The cryopump according to claim 9, characterized in that the at least one opening is formed at the central portion of the intake port plate.

Images