Cryopump and baffle for cryopump

Abstract

We provide a baffle for a cryopump that enables shortening the recovery interval and extending the regeneration interval, as well as a cryopump itself. [Solution] The system comprises a cryopanel thermally connected to a refrigerator, a main body housing the cryopanel, and a baffle positioned at the intake port of the main body. The baffle is equipped with a plurality of fins 42 arranged concentrically, and when viewed from a viewpoint opposite the intake port, the gap S between two adjacent fins 42 in the radial direction D2 is between 1 / 3 and 3 times the width W of the fins 42 in the radial direction D2.

Description

Technical Field

[0001] The present disclosure relates to a cryopump and a baffle for a cryopump.

Background Art

[0002] A cryopump includes a pump case, a heat shield housed in the pump case, a plurality of cryopanels housed in the heat shield, and a baffle for a cryopump attached to an opening of the heat shield. The cryopanels cooled to extremely low temperatures capture gas by condensation or adsorption of the gas and evacuate a vacuum device (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The cryopump recovers the degree of vacuum and the exhaust speed. The recovery of the degree of vacuum is performed from the stop of the previous vacuum process to the start of the current vacuum process. The recovery of the degree of vacuum continues to operate the cryopump until an appropriate value allowed for the current vacuum process is reached. The time required for the recovery of the degree of vacuum is the recovery interval.

[0005] The recovery of the exhaust speed is performed for each of a plurality of vacuum processes. The gas deposits that continue to accumulate due to the repetition of the vacuum process gradually reduce the exhaust speed and lengthen the recovery interval by the amount of the reduction in the exhaust speed. The recovery of the exhaust speed discharges the accumulated gas deposits by raising the temperature of the cryopump and regenerates the inside of the cryopump so that the exhaust speed is recovered. The operation period of the cryopump from the end of the previous recovery to the start of the current recovery is the regeneration interval.

[0006] Cryopumps are desired to shorten the recovery interval and lengthen the regeneration interval, as mentioned above, in order to reduce the time required for the vacuum process. [Means for solving the problem]

[0007] A cryopump for solving the above problems comprises a cryopanel thermally connected to a refrigerator, a main body housing the cryopanel, and a baffle positioned at the intake port of the main body. The baffle has a plurality of fins arranged concentrically, and when viewed from a viewpoint facing the intake port, the gap between two adjacent fins in the radial direction is between 1 / 3 and 3 times the radial width of the fin.

[0008] A baffle for a cryopump to solve the above problem is a baffle applied to a cryopump, comprising a plurality of annular fins having mutually different inner diameters, and a support portion extending radially from the fins. The support portion is configured to fix the plurality of fins so that they are arranged concentrically in a single plane, and the gap between two adjacent fins in the radial direction, as viewed from a viewpoint opposite to the plane in which the plurality of fins are arranged, is between 1 / 3 and 3 times the width of the fin in the radial direction.

[0009] With each of the above configurations, the baffle opening ratio is larger compared to when there is no gap between the fins. As a result, the recovery interval is shortened due to the increased exhaust velocity. Furthermore, because the gap between the fins is between 1 / 3 and 3 times the width of the fin, the distribution of latent heat associated with deposit formation becomes uniform on the surface of the deposit. Consequently, the regeneration interval is extended.

[0010] In the above cryopump, the baffle may be positioned outside the air intake. With this configuration, the distance between the cryopanel and the fins is greater compared to when the fins are positioned inside the main body. As a result, the regeneration interval is extended by the amount of space available for deposit accumulation.

[0011] The above cryopump includes a heat shield connected to the refrigerator and housed in the main body, the baffle being connected to the upper end of the heat shield, and the upper end of the heat shield being located outside the main body. With this configuration, the temperature of the cryopanel is protected by the heat shield even when the baffle is located outside the main body.

[0012] The diameter at the upper end of the heat shield may be between 130 mm and 1300 mm. In the above cryopump, the cryopanel has a radial arrangement extending in the radial direction and is arranged in multiple stages along a direction away from the baffle. The radial length of the first stage cryopanel closest to the baffle is shorter than the radial length of the other stages of cryopanel that are different from the first stage. The multiple fins are arranged on a single plane including the radial direction and have inclined surfaces such that the parts closer to the radial ends are closer to the cryopanel, and may be arranged outside the first stage cryopanel when viewed from a viewpoint facing the intake port.

[0013] In the above configuration, the outermost fin is positioned outside the first-stage cryopanel when viewed from a viewpoint opposite the air intake. Therefore, the distance between the outermost fin and the first-stage cryopanel is longer than the distance between the inner fin and the first-stage cryopanel. As a result, gas that passes through the outermost fin but is not captured by the first-stage cryopanel is more likely to be captured by the second and subsequent cryopanels. In other words, all of the multiple cryopanels are more likely to act effectively in capturing the gas. [Effects of the Invention]

[0014] The cryopump of the present disclosure and the baffle for the cryopump enable shortening of the recovery interval and extension of the regeneration interval.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a configuration diagram of a cryopump. [Figure 2] FIG. 2 is a plan view of a baffle for a cryopump. [Figure 3] FIG. 3 is a cross-sectional view showing a part of a baffle for a cryopump. [Figure 4] FIG. 4 is a graph showing the regeneration interval of an example. [Figure 5] FIG. 5 is a cross-sectional view showing a part of a baffle for a cryopump of a modified example. [Figure 6] FIG. 6 is a configuration diagram of a cryopump of a modified example.

Mode for Carrying Out the Invention

[0016] [Cryopump 10] As shown in FIG. 1, the cryopump 10 includes a pump case 11 which is an example of a main body, a thermal shield 12, a plurality of cryopanels 13, a refrigerator 21, and a baffle for a cryopump (hereinafter also referred to as baffle 41).

[0017] The pump case 11 has a bottomed cylindrical shape. The pump case 11 includes a first cylindrical portion 11A, a second cylindrical portion 11C, and a flange 11F. The first cylindrical portion 11A houses the thermal shield 12. The second cylindrical portion 11C houses the refrigerator 21. The flange 11F surrounds the entire intake port which is an opening of the first cylindrical portion 11A. The flange 11F is connected to an exhaust target such as a chamber.

[0018] The heat shield 12 has a bottomed cylindrical shape. The heat shield 12 houses the cryopanel 13. The heat shield 12 is disposed between the pump case 11 and the cryopanel 13. The heat shield 12 protects the cryopanel 13 from the radiant heat of the pump case 11. The opening edge of the heat shield 12 is the mounting portion 12A. The mounting portion 12A is disposed at the intake port of the first cylindrical portion 11A. The diameter of the mounting portion 12A may be 130 mm or more and 1300 mm or less, or may be 190 mm or more and 310 mm or less.

[0019] The cryopanel 13 is attached to the attachment member 21C of the refrigerator 21. The cryopanel 13 has a plate shape extending along the radial direction D2 of the first cylindrical portion 11A. The cryopanel 13 has a trapezoidal shape that tapers from the attachment member 21C toward the tip. The cryopanel 13 is equally arranged along the circumferential direction of the first cylindrical portion 11A. That is, the cryopanel 13 has a radial shape extending in the radial direction D2. The cryopanel 13 is arranged in a plurality of stages along the axial direction D1. The axial direction D1 is parallel to the direction away from the baffle 41.

[0020] Among the plurality of stages of cryopanels 13, the cryopanel 13 closest to the baffle 41 is the first-stage cryopanel 13. The length in the radial direction D2 of the first-stage cryopanel 13 is shorter than the length in the radial direction D2 of the cryopanels 13 in other stages different from the first stage. The cryopanels 13 from the second stage onward may have the same length in the radial direction D2, or the length in the radial direction D2 may increase as they move away from the baffle 41.

[0021] The refrigerator 21 may be a Gifford-McMahon type refrigerator. The refrigerator 21 includes a first cylinder 21A1, a first stage 21A2, a second cylinder 21B1, and a second stage 21B2. The first cylinder 21A1 is connected in series to the second cylinder 21B1.

[0022] The first cylinder 21A1 includes a first displacer. The first cylinder 21A1 is located within the second cylindrical portion 11C. The first stage 21A2 is the end of the first cylinder 21A1. The first stage 21A2 is thermally connected to the heat shield 12. The first stage 21A2 is connected to the second cylinder 21B1.

[0023] The second cylinder 21B1 includes a second displacer. The second cylinder 21B1 is positioned within the heat shield 12. One end of the second cylinder 21B1 is connected to the first cylinder 21A1. The other end of the second cylinder 21B1 is thermally connected to the second stage 21B2. The second stage 21B2 is connected to the cryo panel 13 via a mounting member 21C.

[0024] The refrigerator 21 cools the first stage 21A2 to a predetermined first temperature within the range of 60K to 100K. The refrigerator 21 cools the second stage 21B2 to a predetermined second temperature within the range of 10K to 20K. The heat shield 12 is cooled to a temperature equivalent to that of the first stage 21A2. The cryopanel 13 is cooled to a temperature equivalent to that of the second stage 21B2 while being protected from radiant heat by the heat shield 12.

[0025] The cryopanel 13 captures gas by condensation or adsorption. The gas captured by the cryopanel 13 generates latent heat associated with the formation of sediment. The sediment in the cryopanel 13 expands the temperature gradient in the thickness direction of the sediment between the cryopanel 13 and the surface of the sediment. Variations in the thickness of the sediment in the cryopanel 13 cause temperature variations within the surface of the sediment. Variations in surface temperature within the sediment lead to further sediment uneven distribution, accelerating the limitation of gas capture.

[0026] [Baffle 41] As shown in Figure 2, the baffle 41 comprises a plurality of fins 42 and a plurality of fin support portions 43. The plurality of fin support portions 43 have a plate shape extending in the radial direction D2. The plurality of fin support portions 43 are arranged radially when viewed from a viewpoint facing the intake port of the first cylindrical portion 11A. The plurality of fins 42 have annular shapes with mutually different inner diameters. The plurality of fin support portions 43 fix the plurality of fins 42 to the opening edge of the heat shield 12 so that the plurality of fins 42 are arranged concentrically. The center 42C of the concentrically arranged fins 42 may be the same as the center of the mounting portion 12A, or it may be slightly different from the center of the mounting portion 12A.

[0027] The multiple fins 42 are arranged on a single plane perpendicular to the axial direction D1. When viewed from a viewpoint opposite the intake port of the first cylindrical portion 11A, the multiple fins 42 overlap the entire first stage cryo panel 13. The fins 42 located on the outermost periphery are positioned outside the first stage cryo panel 13 when viewed from a viewpoint opposite the intake port of the first cylindrical portion 11A. The fins 42 located on the outermost periphery are positioned inside the second and subsequent stages of cryo panels 13 when viewed from a viewpoint opposite the intake port of the first cylindrical portion 11A.

[0028] The fins 42 positioned on the outermost periphery may be positioned inside the first stage cryo panel 13 when viewed from a viewpoint facing the intake port of the first cylindrical portion 11A. Alternatively, the fins 42 positioned on the outermost periphery may be positioned outside the second and subsequent stages cryo panels 13 when viewed from a viewpoint facing the intake port of the first cylindrical portion 11A.

[0029] As shown in Figure 3, the fins 42 have inclined surfaces facing the axial direction D1. The inclined surfaces are closer to the cryopanel 13 at the ends of the radial direction D2. The radial D2 component of the gas flow toward the fins 42 is strengthened toward the ends of the radial direction D2 by the inclined surfaces of each fin 42. Note that fins 42 including the center 42C and fins 42 adjacent to such fins 42 may not have inclined surfaces and may have a planar shape perpendicular to the axial direction D1. Only the fins 42 located on the outermost periphery and fins 42 adjacent to such fins 42 may have inclined surfaces.

[0030] Two fins 42 adjacent to each other in the radial direction D2 are composed of an inner fin 42 and an outer fin 42. The gap S is the distance between the end of the inner fin 42 in the radial direction D2 and the end of the outer fin 42 in the direction opposite to the radial direction D2.

[0031] The width W of the fin 42 is the length of the radial D2 of the fin 42. The width W is the average value of the length of the radial D2 of the inner fin 42 and the length of the radial D2 of the outer fin 42. The length of the radial D2 of the fin 42 is the distance between the end of the radial D2 of the fin 42 and the end of the fin 42 in the opposite direction to the radial D2, and is the average value over the entire circumference of the fin 42.

[0032] The gap S is between 1 / 3 and 3 times the width W. That is, the gap S / width W is between 1 / 3 and 3. The value of gap S / width W may be determined to an optimal value while balancing both the heat resistance capacity and the exhaust speed of the cryopump 10.

[0033] The gap S / width W may vary within the baffle 41. For example, the gap S / width W may be larger for groups of fins 42 positioned on the outside in the radial direction D2. Also, if multiple fins 42 are divided into an inner group of fins 42 and an outer group of fins 42 in the radial direction D2, the gap S / width W of the outer group of fins 42 may be larger than the gap S / width W of the inner group of fins 42. Furthermore, when viewed from a viewpoint opposite the intake port of the first cylindrical portion 11A, the gap S / width W of groups of fins 42 that do not overlap with the first stage cryo panel 13 may be larger than the gap S / width W of groups of fins 42 that overlap with the first stage cryo panel 13.

[0034] [Examples] In the embodiment, a baffle 41 was prepared in which the gap S of the fins 42 was 6 mm, the width W of the fins 42 was 6 mm, and the outer diameter was 136 mm. That is, a baffle 41 was prepared in which the gap S / width W was 1. Then, as the cryopump 10 of the embodiment, the baffle 41 of the embodiment was attached to a heat shield 12 in which the diameter of the mounting portion 12A was 136 mm.

[0035] For Comparative Example 1, a baffle 41 was prepared in which the gap S between the fins 42 was 0 mm, the width W of the fins 42 was 6 mm, and the outer diameter was 136 mm. Then, as the cryopump 10 of Comparative Example 1, the baffle 41 of Comparative Example 1 was separately attached to a heat shield 12, which, like the cryopump 10 of the embodiment, had a mounting portion 12A with a diameter of 136 mm.

[0036] For Comparative Example 2, a baffle 41 was prepared in which the gap S between the fins 42 was 0 mm, the width W of the fins 42 was 6 mm, and the outer diameter was 118 mm. Then, as the cryopump 10 of Comparative Example 2, the baffle 41 of Comparative Example 2 was separately attached to a heat shield 12, which, like the cryopump 10 of the embodiment, had a mounting portion 12A with a diameter of 136 mm.

[0037] For Comparative Example 3, a baffle 41 was prepared in which the gap S between the fins 42 was 0 mm, the width W of the fins 42 was 6 mm, and the outer diameter was 110 mm. Then, as the cryopump 10 of Comparative Example 3, the baffle 41 of Comparative Example 3 was separately attached to a heat shield 12, which, like the cryopump 10 of the embodiment, had a mounting portion 12A diameter of 136 mm.

[0038] The argon pumping speed of the cryopump 10 in the example was 1250 L / sec. In contrast, the argon pumping speed of the cryopump 10 in Comparative Example 1, which was equipped with a baffle 41 having the same outer diameter as the baffle 41 in the example, was 1100 L / sec. The argon pumping speed of the cryopump 10 in Comparative Example 2 was 1180 L / sec. The argon pumping speed of the cryopump 10 in Comparative Example 3 was 1300 L / sec.

[0039] As a result, it was found that, according to the exhaust velocities of Comparative Examples 1, 2, and 3, a larger difference between the diameter of the mounting portion 12A and the outer diameter of the baffle 41 resulted in a higher exhaust velocity. Furthermore, from a comparison between the embodiment and Comparative Example 1, it was found that a larger gap S resulted in a higher exhaust velocity.

[0040] Next, using the cryopump 10 of the example and the cryopumps 10 of Comparative Examples 1, 2, and 3, and setting the supply of argon to the vacuum process, the vacuum process and vacuum recovery were repeated alternately. The recovery pressure immediately after the recovery interval was measured for each vacuum process. Figure 4 shows the changes in recovery pressure using the cryopump 10 of the example and the changes in recovery pressure using the cryopump 10 of Comparative Example 3.

[0041] As shown in Figure 4, in the cryopump 10 of the embodiment, the recovery pressure is 1 × 10¹⁶ until the amount of argon accumulated by repeating the vacuum process reaches 1500 L. -6 It was confirmed that the pressure was maintained at (Pa). It was also confirmed that the recovery pressure gradually increased as the amount of argon stored increased from 1500L. Furthermore, it was confirmed that the argon exhaust capacity of the cryopump 10 in the example was 1880L.

[0042] On the other hand, in the cryopump 10 of Comparative Example 3, the recovery pressure was 1 × 10¹⁶ until the amount of argon accumulated by repeating the vacuum process reached 1200 L. -6It was confirmed that the pressure was maintained at (Pa). Furthermore, it was observed that the recovery pressure gradually increased as the amount of argon stored increased from 1200L. In addition, it was confirmed that the argon exhaust capacity of the cryopump 10 in Comparative Example 3 was 1550L.

[0043] The same trend was observed in the cryopumps 10 of Comparative Examples 1 and 2 as in the cryopump 10 of Comparative Example 3. Furthermore, it was found that the argon exhaust capacity of the cryopump 10 of Comparative Example 1 was 1730 L, and the argon exhaust capacity of the cryopump 10 of Comparative Example 2 was 1680 L.

[0044] Thus, a comparison of Comparative Examples 1, 2, and 3 revealed an improvement in exhaust velocity due to the high opening ratio of baffle 41, i.e., a reduction in the recovery interval. Furthermore, a decrease in exhaust capacity due to the high opening ratio of baffle 41, i.e., a reduction in the regeneration interval, was observed. Finally, a comparison of the Example with Comparative Example 1 revealed an improvement in exhaust velocity and an increase in exhaust capacity due to a gap S / width W of 1, i.e., a reduction in the recovery interval and an extension of the regeneration interval.

[0045] As described above, the expansion of the temperature gradient in the thickness direction in the sediment of the cryopanel 13 increases the surface temperature of the sediment. The uneven distribution of sediment in the cryopanel 13 and the variation in the thickness of the sediment in the cryopanel 13 cause temperature variations within the surface of the sediment. This variation in surface temperature in the sediment leads to further sediment uneven distribution, accelerating the limitation of gas capture. A gap S / width W of 1 suppresses the uneven distribution of sediment in the cryopanel 13 and reduces the variation in surface temperature in the sediment. Furthermore, a gap S / width W of 1 enables a shortening of the recovery interval and an extension of the regeneration interval.

[0046] According to the above embodiment, the following effects can be obtained. (1) The recovery interval is shortened by the amount of the gap S in the baffle 41. Since the gap S is between 1 / 3 and 3 times the width W, the playback interval is extended.

[0047] (2) When the fins 42 have an inclined surface, the gas passing through the fins 42 tends to flow toward the end of the radial direction D2. For this reason, gas that is not captured by the first cryopanel 13 is more likely to be captured by the second and subsequent cryopanels 13.

[0048] (3) The outermost fin 42 is positioned outside the first stage cryopanel 13. The distance between the outermost fin 42 and the first stage cryopanel 13 is longer than the distance between the inner fin 42 and the first stage cryopanel 13. Therefore, gas that passes through the outermost fin 42 but is not captured by the first stage cryopanel 13 is more likely to be captured by the second and subsequent stages cryopanels 13. As a result, all of the multiple stages cryopanels 13 are more likely to act effectively in capturing the gas.

[0049] The above-described embodiment can be implemented with the following modifications. [Baffle 41] As shown in Figure 5, the baffle 41 is not limited to the louver type, but may also be of the chevron type. Even with the chevron type baffle 41, if the gap S is between 1 / 3 and 3 times the width W, the effects similar to those described in (1) to (3) above can be obtained.

[0050] Two fins 42 adjacent to each other in the radial direction D2 may have their axial positions D1 different from each other. For example, in the baffle 41, the fins 42 positioned at a first position in the axial direction D1 and the fins 42 positioned at a second position in the axial direction D1 may be alternately arranged in the radial direction D2. In this case as well, if the gap S is between 1 / 3 and 3 times the width W when viewed from a viewpoint opposite to the intake port of the first cylindrical portion 11A, the effects similar to those described in (1) to (3) above can be obtained.

[0051] For example, the baffle 41 may be configured to be positioned lower in the axial direction D1 than the fin 42 which is positioned outside the radial direction D2 in Figure 1. In this case as well, if the gap S is between 1 / 3 and 3 times the width W when viewed from a viewpoint opposite to the intake port of the first cylindrical portion 11A, the effects similar to those described in (1) to (3) above can be obtained.

[0052] As shown in Figure 6, the baffle 41 may be positioned outside the intake port of the first cylindrical portion 11A in the axial direction D1. In this modified example, the distance between the cryopanel 13 and the fin 42 is greater compared to the case where the fin 42 is positioned inside the first cylindrical portion 11A. As a result, the regeneration interval is extended by the amount of space available for deposit accumulation.

[0053] Furthermore, the baffle 41 may be connected to the upper end of the heat shield 12, and the upper end of the heat shield 12 may be positioned outside the intake port of the first cylindrical portion 11A in the axial direction D1. According to this modification, the temperature of the cryo panel 13 is protected by the heat shield 12 even when the baffle 41 is positioned outside the first cylindrical portion 11A. [Explanation of Symbols]

[0054] D1…Axis direction D2...Radial direction S... Gap W…width 10... Cryopump 11… Pump case 11A...First cylindrical part 12… Heat shield 13... Cryopanel 21... Refrigeration unit 41... Baffle 42... Finn

Claims

1. It is a cryopump, A cryopanel that is thermally connected to the refrigerator, A main body housing the aforementioned cryopanel, A baffle positioned at the air intake of the main body, Equipped with, The aforementioned baffle is It has multiple fins arranged in concentric circles, Viewed from a viewpoint opposite the aforementioned air intake, The gap between two adjacent fins in the radial direction of the aforementioned fin is, The width of the fin in the radial direction is 1 / 3 to 3 times the width of the fin. A cryopump characterized by the following features.

2. The baffle is positioned outside the intake port. The cryopump according to claim 1.

3. The refrigerator is further equipped with a heat shield connected to the main body and housed within the main body, The baffle is connected to the upper end of the heat shield, The upper end of the heat shield is positioned on the outside of the main body. The cryopump according to claim 1 or 2.

4. The diameter at the upper end of the heat shield is 130 mm or more and 1300 mm or less. The cryopump according to claim 3.

5. The cryopanel has a radial arrangement extending in the radial direction and is arranged in multiple stages along a direction away from the baffle, The radial length of the first stage cryopanel closest to the baffle is shorter than the radial length of the other stages of cryopanels that are different from the first stage. The plurality of fins are arranged on a single plane including the radial direction, and have inclined surfaces such that the portions closer to the radial ends are closer to the cryo panel, and are positioned outside the first stage of the cryo panel when viewed from a viewpoint opposite to the air intake. The cryopump according to claim 1 or 2.

6. A baffle for a cryopump, applicable to a cryopump, Multiple fins having annular shapes with mutually different inner diameters, The fin comprises a support portion extending in the radial direction, The support portion is configured to fix the plurality of fins such that the plurality of fins are arranged concentrically in a single plane. Viewed from a viewpoint opposite to the plane on which the plurality of fins are arranged, The gap between the two fins that are adjacent to each other in the radial direction is The width of the fin in the radial direction is 1 / 3 to 3 times the width of the fin. A baffle for a cryopump characterized by the following features.

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