Cryopump

Abstract

The invention provides a cryopump capable of improving productivity of a vacuum processing device and interchangeability with existing vacuum processing in the vacuum processing device by shortening recovery time. A cryopump (10) is provided with: a radiation shield (30) and an intake plate (32) that are thermally connected to a first cooling stage (22) of a refrigerator (14); a skirt section (33); and a cryopanel unit (20) thermally connected to a second cooling stage (24) of the refrigerator (14) and disposed inside the radiation shield (30). A skirt (33) extends from the outer periphery of the air inlet plate (32) toward the inside of the radiation shield (30). A gas inlet (46) is formed between the gas inlet plate (32) and the radiation shield (30), and a frost accommodating space (38) is formed between the cryopanel unit and the gas inlet plate. A gas flow path (48) connecting the gas inlet and the frost accommodating space is formed between the skirt and the radiation shield.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2023-209662 filed on December 12, 2023. The entire content of the Japanese application is incorporated herein by reference. Technical Field

[0002] The present invention relates to a cryopump. Background Art

[0003] A cryopump is a vacuum pump that exhausts gas by condensing or adsorbing gas molecules onto a cryopanel cooled to an ultra-low temperature. Cryopumps are typically used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes and the like.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-515046

[0005] As an example of the use of a cryopump, there is, for example, a vacuum processing apparatus that performs 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, the gas required for the process is supplied into the vacuum chamber of the apparatus. By balancing the supply of the process gas to the vacuum chamber and the vacuum exhaust based on the cryopump, the vacuum chamber can be maintained at a vacuum level suitable for performing the vacuum process. During the interval between processes, the supply of the process gas is stopped, and the cryopump is used to restore the vacuum level of the vacuum chamber to a higher desired vacuum level than during the process. The time required for such a restoration of the vacuum level is also referred to as the recovery time (or return time). The shorter the recovery time, the earlier the next process can start, thereby improving the productivity of the vacuum processing apparatus. Therefore, it is preferable that the recovery time is as short as possible.

[0006] To shorten the recovery time, it is only necessary to increase the exhaust speed of the cryopump. As one method of achieving this goal, it is generally considered to increase the opening ratio of the inlet of the cryopump (i.e., the ratio of the opening area to the total area of the inlet). Increasing the opening ratio of the inlet of the cryopump can not only increase the exhaust speed of the cryopump during the interval between processes but also increase the exhaust speed of the cryopump during the process. Therefore, an increase in the opening ratio may reduce the pressure in the vacuum chamber during the process. Depending on the situation, the pressure in the vacuum chamber may deviate from the specified pressure required for the process. Such an unexpected change in the processing conditions may 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 generated. In other words, an increase in the opening ratio of the inlet of the cryopump brings the advantage of shortening the recovery time and thereby improving the productivity of the vacuum processing apparatus. However, on the other hand, there is also a possibility of causing an adverse effect that does not match the existing vacuum process. Summary of the Invention

[0007] One of the exemplary objects of an embodiment of the present invention is to provide a cryopump that can balance the productivity improvement of a vacuum processing apparatus by shortening the recovery time and the interchangeability with the existing vacuum processing in the vacuum processing apparatus.

[0008] An embodiment of the present invention provides a cryopump, comprising: a cryopump container that defines a cryopump inlet; a refrigerator disposed within the cryopump container and having a first cooling stage and a second cooling stage that is cooled to a lower temperature than the first cooling stage; a radiation shield thermally connected to the first cooling stage and extending axially from the cryopump inlet into the cryopump container; an inlet plate thermally connected to the first cooling stage and extending in a plane perpendicular to the axial direction at the cryopump inlet, and a gas inlet is formed between the inlet plate and the radiation shield; a cryopanel unit thermally connected to the second cooling stage and disposed inside the radiation shield, and a frost accommodation space is formed between the cryopanel unit and the inlet plate; and a skirt thermally connected to the first cooling stage and extending from the outer periphery of the inlet plate into the radiation shield, and a gas flow path connecting the gas inlet and the frost accommodation space is formed between the skirt and the radiation shield.

[0009] According to the present invention, there is provided a cryopump that can balance the productivity improvement of a vacuum processing apparatus by shortening the recovery time and the interchangeability with the existing vacuum processing in the vacuum processing apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a schematic side sectional view showing the cryopump according to the embodiment.

[0011] Figure 2 is a schematic top view showing the first-stage cryopanel of the cryopump according to the embodiment.

[0012] Figure 3 is a schematic view showing the cryopump during operation according to the embodiment.

[0013] Figure 4 is a graph schematically showing an exemplary pressure change during the operation of a vacuum processing apparatus equipped with the cryopump according to the embodiment.

[0014] Figure 5 In (A) and (B) are schematic views showing the first-stage cryopanel of the cryopump according to the comparative example.

[0015] Figure 6 is showing Figure 5 the exhaust speed of the cryopump according to the comparative example in (A) and (B).

[0016] Figure 7It is a schematic diagram showing the exhaust speed of the cryopump related to the embodiment.

[0017] In the figure: 10 - cryopump, 12 - cryopump inlet, 14 - refrigerator, 16 - cryopump container, 20 - cryopanel unit, 22 - first cooling stage, 24 - second cooling stage, 30 - radiation shield, 30a - upper part of the shield, 30b - lower part of the shield, 32 - inlet plate, 33 - skirt, 41 - top cryopanel, 46 - gas inlet, 48 - gas flow path. Detailed implementation mode

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same or equivalent components, parts, and processes are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In each drawing, for the sake of convenience of explanation, the scales and shapes of the respective parts are appropriately set, and unless otherwise specifically stated, they are not to be construed in a limiting sense. The embodiments are examples and do not limit the scope of the present invention in any way. All the features or combinations thereof described in the embodiments are not necessarily the essence of the invention.

[0019] Figure 1 It is a schematic side sectional view showing the cryopump 10 related to the embodiment. In Figure 1 a cross-section including the cryopump central axis (hereinafter also simply referred to as the central axis) C is shown. For the sake of easy understanding, in Figure 1 the central axis C is shown by a single-dot chain line.

[0020] The cryopump 10 is installed, for example, in a vacuum chamber 100 of an ion implantation apparatus, a sputtering apparatus, an evaporation apparatus, or other vacuum processing apparatuses, so as to increase the vacuum degree inside the vacuum chamber 100 to the level required for the desired vacuum processing. The cryopump 10 has a cryopump inlet 12 for receiving the gas to be exhausted from the vacuum chamber 100. The gas enters the internal space of the cryopump 10 through the cryopump inlet 12.

[0021] In addition, hereinafter, in order to easily understand the positional relationship of the components of the cryopump 10, terms such as "axial direction" and "radial direction" may be used. The axial direction of the cryopump 10 indicates the direction passing through the cryopump inlet 12 (i.e., the direction along the central axis C in the figure), and the radial direction indicates the direction along the cryopump inlet 12 (the direction perpendicular to the central axis C). For the sake of convenience of explanation, the position relatively closer to the cryopump inlet 12 in the axial direction may be referred to as "upper", and the position relatively farther from the cryopump inlet 12 may be referred to as "lower". That is, the position relatively farther from the bottom of the cryopump 10 may be referred to as "upper", and the position relatively closer to the bottom of the cryopump 10 may be referred to as "lower". Regarding the radial direction, the position closer to the center of the cryopump inlet 12 (the central axis C in the figure) may be referred to as "inner", and the position closer to the periphery of the cryopump inlet 12 may be referred to as "outer". In addition, such expressions have nothing to do with the configuration when the cryopump 10 is installed in the vacuum chamber 100. For example, the cryopump 10 may be installed in the vacuum chamber 100 such that the cryopump inlet 12 faces downward in the vertical direction.

[0022] And, the direction around the central axis C may be referred to as the "circumferential direction". The circumferential direction is the second direction extending around the cryopump inlet 12 and is the tangential direction orthogonal to the radial direction.

[0023] 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 is also referred to as a high-temperature cryopanel part or a 100K part, etc. The cryopanel unit 20 is a second-stage cryopanel and is also referred to as a low-temperature cryopanel part or a 10K part, etc.

[0024] The refrigerator 14 is, for example, 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 the first cooling temperature and cool the second cooling stage 24 to the 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 cooled to 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 referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0025] Moreover, the refrigerator 14 includes a refrigerator structure portion 21 which structurally supports the second cooling table 24 on the first cooling table 22 and structurally supports the first cooling table 22 on the room temperature portion 26 of the refrigerator 14. Therefore, the refrigerator structure portion 21 includes a first cylinder body 23 and a second cylinder body 25 that extend coaxially along the radial direction of the cryopump 10. The first cylinder body 23 connects the room temperature portion 26 of the refrigerator 14 and the first cooling table 22. The second cylinder body 25 connects the first cooling table 22 and the second cooling table 24. Typically, the first cooling table 22 and the second cooling table 24 are made of a highly thermally conductive metal material such as copper (e.g., pure copper), and the first cylinder body 23 and the second cylinder body 25 are made of other metal materials such as stainless steel. The room temperature portion 26, the first cylinder body 23, the first cooling table 22, the second cylinder body 25, and the second cooling table 24 are linearly arranged in a row in this order.

[0026] A first displacer and a second displacer (not shown) are respectively disposed inside the first cylinder body 23 and the second cylinder body 25 so as to be reciprocally movable. A first regenerator and a second regenerator (not shown) are respectively assembled on the first displacer and the second displacer. Moreover, the room temperature portion 26 has a drive mechanism (not shown) for reciprocally moving the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium gas) in such a manner as to periodically repeat supplying the working gas into the refrigerator 14 and discharging the working gas from the refrigerator 14.

[0027] 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, thereby cooling the first cooling table 22 and the second cooling table 24. The expanded working gas is recovered by the compressor and pressurized again. The refrigerator 14 refrigerates by repeating a heat cycle that includes the supply and discharge of the working gas and the reciprocating movement of the first displacer and the second displacer synchronized therewith.

[0028] The illustrated cryopump 10 is a so-called horizontal cryopump. A horizontal cryopump is generally a cryopump in which the refrigerator 14 is arranged to intersect (usually orthogonally) the central axis C of the cryopump 10. In addition, the present invention can also 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.

[0029] The cryopump container 16 is a vacuum container configured to maintain a vacuum seal of its internal space. The refrigerator 14, the first-stage cryopanel 18, and the cryopanel unit 20 are accommodated in the cryopump container 16.

[0030] The front end of the cryopump container 16 defines the cryopump air inlet 12. The cryopump container 16 has an air inlet flange 16a extending radially outward from its front end. The air inlet flange 16a is provided around the entire circumference of the cryopump container 16. The cryopump 10 is mounted on the vacuum chamber 100 of the vacuum processing apparatus using the air inlet flange 16a. Additionally, the cryopump 10 may also be mounted on the vacuum chamber 100 via a gate valve (not shown).

[0031] Furthermore, the cryopump container 16 has: a container body 16b extending axially from the air inlet flange 16a; a container bottom 16c closing the container body 16b on the side opposite to the cryopump air inlet 12; and a refrigerator housing cylinder 16d extending laterally between the air inlet flange 16a and the container bottom 16c. On the side opposite to the container body 16b, the end of the refrigerator housing cylinder 16d is mounted on the room temperature portion 26 of the refrigerator 14. Thus, the low temperature portion of the refrigerator 14 (i.e., the first cylinder block 23, the first cooling table 22, the second cylinder block 25, and the second cooling table 24) is arranged in the cryopump container 16 without contacting the cryopump container 16. The first cylinder block 23 is arranged in the refrigerator housing cylinder 16d, and the first cooling table 22, the second cylinder block 25, and the second cooling table 24 are arranged in the container body 16b. The first-stage cryopanel 18 and the cryopanel unit 20 are also arranged in the container body 16b.

[0032] The first-stage cryopanel 18 includes a radiation shield 30, an air inlet plate 32, and a skirt 33, which surround the cryopanel unit 20. The first-stage cryopanel 18 provides an ultra-low temperature surface for protecting the cryopanel unit 20 from radiant heat from the outside of the cryopump 10 or from the cryopump container 16. The first-stage cryopanel 18 is thermally connected to the first cooling table 22. Therefore, the first-stage cryopanel 18 is cooled to the first cooling temperature. Thus, the gas (e.g., moisture) condensed at the first cooling temperature is trapped by its surface. The first-stage cryopanel 18 is usually made of a highly thermally conductive metal material such as copper (e.g., pure copper), and if necessary, its surface may also be coated with a metal layer such as nickel.

[0033] There is a gap between the first-stage cryopanel 18 and the cryopanel unit 20, and the first-stage cryopanel 18 does not contact the cryopanel unit 20. The first-stage cryopanel 18 also does not contact the cryopump container 16.

[0034] The radiation shield 30 is provided to protect the cryopanel unit 20 from the radiant heat from the cryopump container 16. The radiation shield 30 extends axially in a cylindrical shape (e.g., a cylindrical shape) from the cryopump air inlet 12 into the cryopump container 16. The radiation shield 30 is located 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. Therefore, the radiation shield 30 does not contact the cryopump container 16.

[0035] The first cooling stage 22 of the refrigerator 14 is directly mounted on the outer surface of the side portion of the radiation shield 30. Thus, the radiation shield 30 is thermally connected to the first cooling stage 22 and is thus cooled to the first cooling temperature. In addition, the radiation shield 30 may also be mounted on the first cooling stage 22 via an appropriate heat conducting member. Further, the second cooling stage 24 and the second cylinder block 25 of the refrigerator 14 are inserted into the radiation shield 30 from the side portion of the radiation shield 30.

[0036] In the present embodiment, the radiation shield 30 includes a shield upper portion 30a disposed close to the cryopump air inlet 12 and a shield lower portion 30b disposed away from the cryopump air inlet 12. The shield upper portion 30a is disposed on the cryopump air inlet 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 16c side with respect to the second cooling stage 24. The shield upper portion 30a is a cylindrical tube open at both ends and surrounds the upper portion of the cryopanel unit 20. The shield lower portion 30b is a bottomed cylinder open at the upper end and closed at the lower end 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 located at substantially 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 on the outside of the shield upper portion 30a than on the outside of the shield lower portion 30b.

[0037] In order to protect the cryopanel unit 20 from the radiant heat of an external heat source (e.g., the heat source of the vacuum chamber 100 in which the cryopump 10 is installed) of the cryopump 10, an air inlet plate 32 is provided on the cryopump air inlet 12. The air inlet plate 32 is thermally connected to the first cooling stage 22 via the radiation shield 30 and is thus cooled to the first cooling temperature in the same manner as the radiation shield 30.

[0038] The intake port plate 32 extends in a plane perpendicular to the axis at the intake port 12 of the cryopump. The intake port plate 32 is, for example, a single circular plate arranged perpendicular to the central axis C in a manner that crosses the intake port 12 of the cryopump, 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 upper part 30a of the shield. As will be described later, a gap is formed between the intake port plate 32 and the upper part 30a of the shield. In this example, the entire surface of the intake port plate 32 is flat and does not have an inclined surface.

[0039] In the illustrated example, the intake port plate 32 is axially arranged at the front end of the cryopump container 16, that is, at the same height as 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 can also be arranged at a position axially above the front end of the cryopump container 16, that is, it can be arranged on the side of the vacuum chamber 100, or it can also be arranged at a position axially below the front end of the cryopump container 16, that is, it can be arranged on the side of the cryopanel unit 20.

[0040] The intake port plate 32 is joined to the upper end of the upper part 30a of the shield. For example, the intake port plate 32 can be mounted on a joint claw (not shown) at its outer peripheral part. The joint claw is a convex part protruding radially inward at the upper end of the upper part 30a of the shield and is formed at equal intervals in the circumferential direction (for example, every 90°). As Figure 2 shown, the intake port plate 32 has a plate mounting part 32a at a position corresponding to the joint claw on its outer periphery. The plate mounting part 32a is fixed to the joint claw using a fastening member 32b such as a bolt or by other appropriate methods such as welding.

[0041] The cryopanel unit 20 includes a plurality of cryopanels 41, 42, 43 arranged axially. These cryopanels are respectively thermally connected to the second cooling stage 24 and thus cooled to a second cooling temperature lower than the first cooling temperature. The cryopanel unit 20 is arranged inside the cryopump container 16 and inside the radiation shield 30, and is axially arranged below the intake port plate 32.

[0042] For the sake of convenience of explanation, the part of these cryopanels closest to the intake port 12 of the cryopump is referred to as the top cryopanel 41. Therefore, in the cryopanel unit 20, the top cryopanel 41 is axially arranged at the position closest to the intake port plate 32. 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 circular plate-shaped component arranged perpendicular to the axis, and its center is located on or near the central axis C of the cryopump 10. The entire surface of the top cryopanel 41 is flat and does not have an inclined surface.

[0043] In order to condense more gas, the top cryoplate 41 is relatively large. The diameter of the top cryoplate 41 can be, for example, 70% or more or 80% or more of the diameter of the radiation shield 30 (for example, the upper part 30a of the shield). Also, the diameter of the top cryoplate 41 can be 98% or less or 90% or less of the diameter of the radiation shield 30 (for example, the upper part 30a of the shield). Thus, it is possible to reliably prevent the top cryoplate 41 from contacting the radiation shield 30.

[0044] The top cryoplate 41 can be disposed near the approximate middle in the axial direction within the container body 16b of the cryopump container 16. The central portion of the top cryoplate 41 can be directly mounted on 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 cryoplate 41 can be in the range of, for example, 30 - 70% or 40 - 60% of the axial distance from the intake port plate 32 to the container bottom 16c. In this way, in the axial direction, a relatively wide empty space is formed between the cryoplate unit 20 (i.e., the top cryoplate 41) and the intake port plate 32. This space can be used as a frost accommodation space 38 for accommodating the condensate layer of the exhausted gas condensed on the top cryoplate 41.

[0045] In addition to the top cryoplate 41, the cryoplate unit 20 is provided with one or more intermediate cryoplates 42, one or more lower cryoplates 43, and a connecting cryoplate 44. In this example, one intermediate cryoplate 42 and two lower cryoplates 43 are provided. The axial interval between the intermediate cryoplate 42 and the lower cryoplates 43 is larger than the axial interval between the lower cryoplates 43 themselves. Thus, a relatively wide condensate layer accommodation space can be formed between the intermediate cryoplate 42 and the lower cryoplates 43. This space can be used as a frost accommodation space 39 for accommodating the condensate layer condensed on the lower cryoplates 43.

[0046] As an example, the diameters of the intermediate cryoplate 42 and the lower cryoplates 43 can both be smaller than the diameter of the top cryoplate 41. Also, the diameter of the intermediate cryoplate 42 can be smaller than the diameter of the lower cryoplates 43.

[0047] In the illustrated example, both the intermediate cryoplate 42 and the lower cryoplates 43 have a frustum - of - a - cone shape, which has a flat circular - plate - shaped central portion and an outer peripheral portion that slopes downward as it faces radially outward. The centers of these cryoplates are located on or near the central axis C of the cryopump 10. In the axial direction, the intermediate cryoplate 42 is located below the top cryoplate 41 and above the second cooling stage 24, and the lower cryoplates 43 are located at a position lower than the second cooling stage 24. For example, the intermediate cryoplate 42 can be sandwiched between the top cryoplate 41 and the second cooling stage 24. Or, the intermediate cryoplate 42 can also be located at the same height as the second cooling stage 24 (for example, between the upper surface and the lower surface of the second cooling stage 24).

[0048] The connecting cold plate 44 extends from the second cooling table 24 downward toward the lower cold plate 43 and thermally connects the lower cold plate 43 to the second cooling table 24. The connecting cold plate 44 can be a set of elongated plate-like members extending axially along both radial sides of the second cooling table 24. The upper end of the connecting cold plate 44 is mounted on the second cooling table 24, and the lower end is mounted on the lower cold plate 43.

[0049] Each of the cold plates 41, 42, 43 constituting the cold plate unit 20 is usually made of a highly thermally conductive metal material such as copper (e.g., pure copper), and if necessary, its surface can also be coated with a metal layer such as nickel. Also, an adsorbent material (e.g., activated carbon) that captures non-condensable gases (e.g., hydrogen) by adsorption can be provided on at least a part of the surface of the cold plate unit 20. The adsorbent material can be provided, for example, on the back surfaces of the top cold plate 41, the middle cold plate 42, and / or the lower cold plate 43.

[0050] In addition, the specific structure of the cold plate unit 20 is not limited to the above. For example, an additional cold plate can be provided between the top cold plate 41 and the inlet plate 32, and the diameter of such an additional cold plate can be smaller than the diameter of the top cold plate 41. The top cold plate 41 can also have an inclined surface that slopes downward (or upward) as it faces radially outward at its outer peripheral portion. The diameter of at least one of the middle cold plate 42 and the lower cold plate 43 (e.g., the lowermost cold plate) can be larger than the diameter of the top cold plate 41. The middle cold plate 42 and / or the lower cold plate 43 can also be a circular plate-like plate without an inclined surface like the top cold plate 41. The shape of the cold plate when viewed axially is not limited to a circle, and can also have other shapes such as a rectangle or a polygon.

[0051] A first gas inlet 34 for introducing gas from the outside to the inside of the cryopump 10 is formed on the first-stage cold plate 18. The first gas inlet 34 is at least one opening formed in the inlet plate 32. Since the opening is a hole penetrating the inlet plate 32, it allows gas to flow from the vacuum chamber 100 to the frost accommodation space 38 through the first gas inlet 34.

[0052] At least one opening of the inlet plate 32 serving as the first gas inlet 34 is formed at the central portion of the inlet plate 32. The central portion of the inlet plate 32 can be within a range of, for example, 3 / 4 or less, 1 / 2 or less, or 1 / 4 or less of the diameter of the cryopump inlet 12. No opening serving as the first gas inlet 34 is formed at the outer peripheral portion of the inlet plate 32 that is more outward than such a central portion of the inlet plate 32.

[0053] As shown in the figure, a plurality of openings can be formed in the inlet plate 32. As an example, inFigure 2 Sixty-six openings are shown. As shown in the figure, these openings can be regularly arranged on the air inlet plate 32, such as in a grid pattern or the like. The openings can be equally spaced in the radial and circumferential directions. The shape of the openings is, for example, circular, but is not limited thereto, and other shapes such as rectangular or long holes can also be used.

[0054] In addition, a second gas inlet 36 for introducing gas from the outside to the inside of the cryopump 10 is also formed on the first-stage cryoplate 18. The second gas inlet 36 is the gap between the upper shield 30a and the lower shield 30b of the radiation shield 30 having the split structure as described above (also referred to as the shield gap in this specification).

[0055] The axial distance from the air inlet plate 32 to the shield gap is greater than the axial distance from the air inlet plate 32 to the top cryoplate 41. The second gas inlet 36 is located at a position axially lower than the top cryoplate 41, that is, formed at the axial height between the top cryoplate 41 and the bottom 16c of the container. In this example, the second gas inlet 36 is formed at the axial height between the intermediate cryoplate 42 and the lower cryoplate 43. The second gas inlet 36 can also be formed between the top cryoplate 41 and the intermediate cryoplate 42. Therefore, it is allowed for the gas to flow from the vacuum chamber 100 through the outer shield gap 31 and the second gas inlet 36 to the frost-containing space 39 below the top cryoplate 41.

[0056] In addition, the shield gap between the upper shield 30a and the lower shield 30b can also be set at any position in the axial direction, and can be set at the axial height between the top cryoplate 41 and the air inlet plate 32. At this time, it is allowed for the gas to flow from the vacuum chamber 100 through the second gas inlet 36 to the frost-containing space 38 above the top cryoplate 41.

[0057] In the present embodiment, the air inlet plate 32 is provided with a skirt 33. The skirt 33 extends from the outer periphery of the air inlet plate 32 toward the inside of the radiation shield 30. The skirt 33 extends in the axial direction (i.e., in the direction parallel to the radiation shield 30).

[0058] The axial length L of the skirt 33 is less than the axial distance from the air inlet plate 32 to the top cryoplate 41. For example, the axial length L of the skirt 33 can be less than 3 / 4, 1 / 2, or 1 / 4 of the axial distance from the air inlet plate 32 to the top cryoplate 41. Thus, the skirt 33 and the air inlet plate 32 are arranged together at a position relatively above the frost-containing space 38. Similar to the radiation shield 30 and the air inlet plate 32, the skirt 33 is not in physical contact with the cryoplate unit 20 such as the top cryoplate 41.

[0059] As described above, since the second gas inlet 36 is provided at a position axially below the top cryopanel 41, the axial length L of the skirt 33 is smaller than the axial distance from the inlet plate 32 to the second gas inlet 36. This helps to increase the diameter of the top cryopanel 41, and thus increase the gas retention capacity of the cryopump 10. Suppose that if the skirt 33 extends axially below the top cryopanel 41, the top cryopanel 41 will be surrounded by the skirt 33. To prevent physical contact between the top cryopanel 41 and the skirt 33, the diameter of the top cryopanel 41 must be smaller than that of the skirt 33. Since miniaturization of the top cryopanel 41 will result in a reduction in the gas retention capacity of the cryopump 10, this is to be avoided.

[0060] The skirt 33 is a ring or a short cylinder that frames the inlet plate 32, and can also be said to form a so-called circular tray together with the inlet plate 32. The inlet plate 32 with such a skirt 33 is arranged at the cryopump inlet 12 so as to cover most of the open area inside the upper end of the radiation shield 30. Additionally, for ease of understanding, the skirt 33 is shown by a dashed line in Figure 2 .

[0061] The diameters of the inlet plate 32 and the skirt 33 are smaller than the inner diameter of the radiation shield 30 (e.g., the upper shield 30a). However, the diameters of the inlet plate 32 and the skirt 33 can be, for example, 70% or more, 80% or more, or 90% or more of the inner diameter of the radiation shield 30 (e.g., the upper shield 30a), so that the inlet plate 32 can occupy most of the open area inside the upper end of the radiation shield 30.

[0062] Therefore, as shown in Figure 1 and Figure 2 , in addition to the first gas inlet 34 and the second gas inlet 36, a gas inlet 46 as another gas inlet is also formed between the inlet plate 32 and the radiation shield 30 (more specifically, the upper end of the upper shield 30a). The gas inlet 46 is a radial gap between the radiation shield 30 and the inlet plate 32. And 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 communicates with the frost accommodation space 38 above the top cryopanel 41 through the gas flow path 48. Therefore, it is allowed for the gas to flow from the vacuum chamber 100 through the gas inlet 46 and the gas flow path 48 and then to the frost accommodation space 38.

[0063] Thus, the cryopump 10 has three paths for introducing the gas to be evacuated from the vacuum chamber 100 into the cryoplate unit 20 inside the cryopump 10. The first path is the path from the first gas inlet 34 to the frost accommodation space 38. The second path is from the outer shield gap 31 through the second gas inlet 36 to the frost accommodation space 39. The third path is from the gas inlet 46 through the gas flow path 48 to the frost accommodation space 38. These three paths contribute to increasing the evacuation speed of the cryopump 10.

[0064] In the illustrated example, the outer shield gap 31 is wider than the gas flow path 48. That is, as Figure 1 shown, the radial distance R1 from the radiation shield 30 to the cryopump container 16 at the cryopump inlet 12 is greater than the radial distance R2 from the skirt 33 to the radiation shield 30 at the gas flow path 48. According to the verification by the present inventor, it has been confirmed that such a dimensional setting between the outer shield gap 31 and the gas flow path 48 effectively shortens the recovery time of the cryopump 10.

[0065] The axial length L of the skirt 33 can be within 8 times the radial distance R2 from the skirt 33 to the radiation shield 30. According to the verification by the present inventor, in this way, the recovery time of the cryopump 10 is effectively shortened.

[0066] Also, as shown in the figure, the diameter of the skirt 33 can be smaller than the diameter of the top cryoplate 41. Since the skirt 33 and the inlet plate 32 have the same diameter, the diameter of the inlet plate 32 can also be smaller than the diameter of the top cryoplate 41. Thus, the gas inlet 46 and the gas flow path 48 can be set wider. This helps to increase the opening ratio of the cryopump inlet 12 to improve the evacuation speed of the cryopump 10. Also, since the area of the top cryoplate 41 can be relatively enlarged, the gas retention amount of the cryopump 10 can be increased.

[0067] Hereinafter, the operation of the cryopump 10 having the above structure will be described. Figure 3 is a schematic diagram showing the cryopump 10 during the vacuum evacuation operation according to the embodiment. When operating the cryopump 10, first, before its operation, the inside of the vacuum chamber 100 is rough pumped to a cryopump operation start pressure of, for example, about 1 Pa using another appropriate rough pump (not shown). After that, 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 cryoplate 18 and the cryoplate unit 20 thermally connected to these are also cooled to the first cooling temperature and the second cooling temperature, respectively.

[0068] The inlet plate 32 cools the gas flying from the vacuum chamber 100 toward the cryopump 10. At the first cooling temperature, the vapor pressure is low enough (for example, 10 -8The gas (with a vapor pressure of 10 Pa or less) condenses on the surface of the intake port plate 32. This gas may also be referred to as the first type of gas. The first type of gas is, for example, water vapor. Thus, the intake port plate 32 can discharge the first type of gas.

[0069] As Figure 3 shown by the solid arrows in the figure, a part of the gas enters the cryopump 10 from any one of the above three paths. That is, the gas can enter the frost accommodation space 38 from the vacuum chamber 100 through the first gas inlet 34. Also, the gas can enter the gas inlet 46 from the vacuum chamber 100 and enter the frost accommodation space 38 through the gas flow path 48. Moreover, the gas can enter the outer gap 31 of the shield and enter the frost accommodation 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 on their surfaces for exhaust. The gas with a vapor pressure not low enough at the first cooling temperature can enter the radiation shield 30 through these paths.

[0070] The gas entering from the first gas inlet 34 and the gas inlet 46 is cooled by the top cryoplate 41. The gas entering from the second gas inlet 36 is cooled by the middle cryoplate 42 or the lower cryoplate 43. The gas with a vapor pressure low enough (e.g., 10 Pa or less) at the second cooling temperature condenses on the surfaces of these cryoplates. This gas may also be referred to as the second type of gas. The second type of gas is, for example, argon (Ar). Thus, the cryoplate unit 20 can discharge the second type of gas. -8 Pa or less) condenses on the surfaces of these cryoplates. This gas may also be referred to as the second type of gas. The second type of gas is, for example, argon (Ar). Thus, the cryoplate unit 20 can discharge the second type of gas.

[0071] For easy understanding, Figure 3 shows the condensation layer 50 of the gas condensed on the top cryoplate 41. As shown in the figure, the condensation layer 50 can form a hemispherical ice block in the frost accommodation space 38. Additionally, in Figure 3 for ease of explanation, illustrations of other condensation layers such as the condensation layer on the lower cryoplate 43 are omitted, for example.

[0072] In the present embodiment, the skirt 33 and the intake port plate 32 are arranged above the frost accommodation space 38 in the axial direction. For example, as described above, the axial length L of the skirt 33 can be less than 1 / 2 of the axial distance from the intake port plate 32 to the top cryoplate 41. Thus, a relatively large axial gap can be formed between the skirt 33 and the top cryoplate 41, and a larger condensation layer 50 can be condensed on the top cryoplate 41. The gas retention capacity of the cryopump 10 can be increased.

[0073] Moreover, since the first gas inlet 34 is formed at the central portion of the intake port plate 32, the condensation layer 50 can grow uniformly on the top cryoplate 41 together with the gas inlet 46 formed around the intake port plate 32.

[0074] A gas with an insufficiently low vapor pressure at the second cooling temperature is adsorbed onto the adsorption material of the cryopanel unit 20. This gas may also be referred to as a third gas. The third gas is, for example, hydrogen (H 2 ). Thus, the cryopanel unit 20 can expel the third gas. Therefore, the cryopump 10 can expel various gases by condensation or adsorption to bring the degree of vacuum in the vacuum chamber 100 to a desired level.

[0075] Figure 4 FIG. is a diagram schematically showing an exemplary pressure change during the operation of a vacuum processing apparatus (e.g., a PVD apparatus) equipped with the cryopump 10 according to the embodiment. In Figure 4 , it is schematically shown how the pressure in the vacuum chamber of the vacuum processing apparatus changes during a vacuum process (e.g., a PVD process) and during the rest period between vacuum processes.

[0076] During the process, a process gas is supplied to the vacuum chamber. By the balance between the supply of the process gas to the vacuum chamber and the vacuum exhaust based on the cryopump, the pressure in the vacuum chamber is maintained at a degree of vacuum suitable for performing the vacuum process. The degree of vacuum during the process can be, for example, an intermediate flow region of the order of 10 -1 Pa. Since the supply of the process gas is stopped during the rest period between processes, the cryopump restores the degree of vacuum in the vacuum chamber to a higher desired degree of vacuum than during the process. During the rest period, the degree of vacuum, for example, returns from 10 -5 Pa to a molecular flow region of the order of 10 -6 Pa. During the rest period, preparations for the next process are carried out: the substrate such as a semiconductor wafer after processing is removed from the vacuum chamber, and a new substrate is introduced into the vacuum chamber.

[0077] As described at the beginning of this specification, the time required to restore the degree of vacuum during the rest period between processes is also referred to as the recovery time (or return time). In Figure 4 , the recovery time is denoted by the symbol Tr. The shorter the recovery time Tr, the earlier the next process can start, thereby improving the productivity of the vacuum processing apparatus.

[0078] Therefore, it is preferable that the recovery time Tr is as short as possible. To shorten the recovery time Tr, it is only necessary to increase the exhaust speed of the cryopump. As one method to achieve this goal, it is generally considered to increase the opening ratio of the inlet of the cryopump (i.e., the ratio of the opening area to the total area of the inlet).

[0079] Figure 5 In FIGS. (A) and (B), they are schematic views showing the first-stage cryopanel of the cryopump according to the comparative example. In Figure 5In Comparative Example 1 shown in (A), the first-stage cryopanel 18A has a radiation shield 30A and an inlet shield 32A that seals the opening of the radiation shield 30A. However, a plurality of small holes for introducing gas into the radiation shield 30A are formed in the inlet shield 32A. Comparative Example 1 is a typical example of the first-stage cryopanel in an existing cryopump.

[0080] In Figure 5 In Comparative Example 2 shown in (B), the first-stage cryopanel 18B has a radiation shield 30B and an inlet shield 32B disposed at the center of the opening of the radiation shield 30B. A plurality of small holes for introducing gas into the radiation shield 30B are formed in the inlet shield 32B. Since the inlet shield 32B is disposed at the center of the opening of the radiation shield 30B, a gap 46B is formed between the inlet shield 32B and the radiation shield 30B. Thus, in Figure 5 In Comparative Example 2 shown in (B), compared with Figure 5 Comparative Example 1 shown in (A), the opening ratio of the cryopump inlet is high. Gas can be introduced into the radiation shield 30A not only through the small holes in the inlet shield 32B but also through this gap. Comparative Example 2 is an example of a first-stage cryopanel that can achieve a higher exhaust speed than Comparative Example 1 based on the findings of the present inventor.

[0081] Figure 6 is a schematic diagram showing Figure 5 the exhaust speeds of the cryopumps related to the comparative examples in (A) and (B). In Figure 6 it, for Figure 5 Comparative Example 1 shown in (A) and Figure 5 Comparative Example 2 shown in (B), the change in the exhaust speed from the intermediate flow region to the molecular flow region with respect to pressure (vacuum degree) is shown. As Figure 6 shown, generally, regarding the exhaust speed of a cryopump, in the intermediate flow region, the higher the pressure, the higher the exhaust speed. In contrast, in the molecular flow region, the exhaust speed is substantially constant regardless of 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 inlet. If the exhaust speeds in Comparative Example 1 and Comparative Example 2 are compared, as described above, since the opening ratio of the cryopump inlet 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.

[0082] Therefore, if the cryopumps involved in these comparative examples are applied to a vacuum processing apparatus, the cryopump of Comparative Example 2 can provide a higher exhaust speed both during processing and during the rest period between processes. The high exhaust speed during the rest period can shorten the recovery time, and thus can improve the productivity of the vacuum processing apparatus.

[0083] However, an increase in the exhaust speed during processing may cause a decrease in the pressure of the vacuum chamber during processing. Depending on the situation, the pressure of the vacuum chamber may deviate from the specified pressure required for processing. Such an unexpected change in processing conditions may have an unexpected impact on the quality of the processing. For example, in vacuum film formation, the pressure during processing affects the film thickness generated. In other words, an increase in the opening ratio of the cryopump inlet brings the advantage of shortening the recovery time and improving the productivity of the vacuum processing apparatus based on this. However, on the other hand, there may also be an adverse effect that does not match the existing vacuum processing.

[0084] Therefore, in the embodiment, in addition to the gas inlet 46 around the inlet plate 32, a skirt portion 33 is also provided on the inlet plate 32, and a gas flow path 48 that connects the gas inlet 46 to the frost accommodation space 38 is formed between the skirt portion 33 and the radiation shield 30. The skirt portion 33 can adjust the conductivity of the cryopump inlet 12 differently in the intermediate flow region and the molecular flow region.

[0085] In the intermediate flow region, the gas is closer to viscous flow than in the molecular flow region. Therefore, compared with the case where there is no skirt portion 33 on the inlet plate 32, the skirt portion 33 reduces the conductivity of the cryopump inlet 12. The longer the axial length L of the skirt portion 33, the smaller the conductivity.

[0086] Therefore, in the intermediate flow region, the skirt portion 33 can offset the increase in conductivity obtained due to the increase in the opening ratio of the cryopump inlet 12 based on the gas inlet 46. That is, the conductivity of the cryopump inlet 12 having both the gas inlet 46 and the skirt portion 33 can be maintained at the same level as the case where they are not provided on the cryopump inlet 12 (for example, Comparative Example 1).

[0087] On the other hand, in the molecular flow region, the conductivity of the cryopump inlet 12 depends on the opening area of the cryopump inlet 12. The skirt portion 33 extends parallel to the radiation shield 30, so it substantially does not affect the flow path cross-sectional area of the gas flow path 48. The decrease in conductivity caused by the skirt portion 33 in the molecular flow region is less than the decrease in conductivity caused by the skirt portion 33 in the intermediate flow region. That is, the influence of the skirt portion 33 in the molecular flow region is small.

[0088] Therefore, in the molecular flow region, even if the skirt portion 33 is provided on the intake port plate 32, the conductivity of the cryopump intake port 12 increases due to the effect of the increased opening ratio of the cryopump intake port 12 based on the gas inlet 46. That is, the conductivity of the cryopump intake port 12 having both the gas inlet 46 and the skirt portion 33 is larger than the case where they are not provided on the cryopump intake port 12 (for example, Comparative Example 1).

[0089] Figure 7 is a schematic diagram showing the exhaust speed of the cryopump 10 according to the embodiment. Similar to Figure 6 Similarly, in Figure 7 also shows the change in the exhaust speed with respect to the pressure (vacuum degree) from the intermediate flow region to the molecular flow region. In Figure 7 the exhaust speed of the above Comparative Example 1 is represented by a dotted line, and the exhaust speed of the cryopump 10 according to the embodiment is represented by a solid line.

[0090] The conductivity of the cryopump intake port 12 is the main factor determining the exhaust speed of the cryopump 10. Therefore, the cryopump 10 according to the embodiment can increase the exhaust speed in the molecular flow region compared to the existing cryopump such as Comparative Example 1. That is, the cryopump 10 can provide a higher exhaust speed during the rest between processes in the vacuum processing apparatus than Comparative Example 1. And the cryopump 10 according to the embodiment can make the exhaust speed consistent with the existing cryopump such as Comparative Example 1 in the intermediate flow region.

[0091] Therefore, according to the embodiment, a cryopump 10 is provided that can balance the improvement of the productivity of the vacuum processing apparatus by shortening the recovery time and the interchangeability with the existing vacuum processing in the vacuum processing apparatus.

[0092] As described above, the present invention has been described based on the embodiments. Those skilled in the art should understand that the present invention is not limited to the above embodiments, various design changes can be made, various variations can exist, and such variations are also within the scope of the present invention. The various features described in one embodiment can also be applied to other embodiments. The new embodiments generated by combination have the effects of the respective embodiments being combined.

[0093] In the above embodiment, the intake port plate 32 has at least one opening portion as the first gas inlet 34 at the central portion of the intake port plate 32. At the same time or instead, the first gas inlet 34 can also be formed at the outer peripheral portion of the intake port plate 32. And in one embodiment, the intake port plate 32 may not have an opening portion as the first gas inlet 34.

[0094] In the above-described embodiment, the radiation shield 30 is composed of a plurality of divided parts, which has a shield upper part 30a and a shield lower part 30b. Instead, the radiation shield 30 may also be a single member extending from the cryopump air inlet 12 to the container bottom 16c. The second gas inlet 36 may be at least one opening formed in such a single member.

[0095] In the above-described embodiment, the skirt 33 extends parallel to the radiation shield 30. Instead, in one embodiment, the skirt 33 may extend obliquely from the outer periphery of the air inlet plate 32 so as to face downward as it faces radially outward (or radially inward).

[0096] As described above, the present invention has been described based on the embodiments. Those skilled in the art should understand that the present invention is not limited to the above-described embodiments, various design changes can be made, various modifications can exist, and such modifications are also within the scope of the present invention.

Claims

1. A cryogenic pump, characterized in that: have: Cryogenic pump container, determine the cryogenic pump air inlet; a refrigerator disposed in the cryopump housing and comprising a first cooling stage and a second cooling stage cooled to a lower temperature than the first cooling stage; a radiation shield thermally connected to the first cooling stage and extending axially from the cryopump inlet toward the cryopump housing; an air inlet plate thermally connected to the first cooling stage and extending along a plane perpendicular to the axial direction at the cryopump air inlet, and forming a gas inlet between the air inlet plate and the radiation shield; a cryopanel unit thermally connected to the second cooling stage and arranged inside the radiation shield, with a frost receiving space formed between the cryopanel unit and the air inlet plate; and The skirt is thermally connected to the first cooling stage and extends from the outer periphery of the air inlet plate toward the inside of the radiation shield, and a gas flow path connecting the gas inlet and the frost storage space is formed between the skirt and the radiation shield.

2. The cryopump according to claim 1, characterized in that The cryopanel unit includes a top cryopanel, the top cryopanel being a cryopanel disposed at a position closest to the air inlet plate in the axial direction in the cryopanel unit. The axial length of the skirt is smaller than the axial distance from the air inlet plate to the top cryopanel.

3. The cryopump according to claim 2, characterized in that The axial length of the skirt is less than 1 / 2 of the axial distance from the air inlet plate to the top cryopanel.

4. The cryopump according to claim 2, characterized in that The skirt has a diameter that 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 housing at the cryopump inlet is greater than a radial distance from the skirt to the radiation shield at the gas flow path.

7. The cryopump according to claim 1, wherein: The radiation shield includes an upper shield portion disposed near the cryopump inlet and a lower shield portion disposed away from the cryopump inlet, wherein the upper shield portion and the lower shield portion are disposed with a shield gap therebetween. The axial length of the skirt is less than the axial distance from the air inlet plate to the shield gap.

8. The cryopump according to claim 7, characterized in that The cryopanel unit includes a top cryopanel, the top cryopanel being a cryopanel disposed at a position closest to the air inlet panel in the cryopanel unit. An axial distance from the air inlet plate to the shield gap is greater than an axial distance from the air inlet plate to the top cryopanel.

9. The cryopump according to claim 1, wherein: The air inlet plate has at least one opening.

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

Images