JP2016075218A - Cryopump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain an increase of recovery time in a vacuum processing device and extend a regeneration interval of a cryopump.SOLUTION: A cryopump 10 comprises: a cryopump container 38 that defines a suction port 12; a refrigerator 16 that comprises a first stage 22 and a second stage 24 housed in the cryopump container 38 and in which the second stage 24 is cooled to a temperature lower than that of the first stage 22; a first cryopanel 18 thermally connected to the first stage 22 and surrounded by the cryopump container 38; and a second cryopanel 20 thermally connected to the second stage 24 and surrounded by the first cryopanel 18. The first cryopanel 18 comprises a plate member 32 including an inlet opening part in the suction port 12. The inlet opening part is formed in the plate member 32 so that the ratio of the conductance of the plate member 32 to the opening conductance of the suction port 12 is 6% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cryopump.

  One application of a cryopump is a vacuum processing apparatus such as a sputtering apparatus. In the vacuum processing apparatus, a certain vacuum process can be repeatedly executed. The main role of the cryopump in such an apparatus is to continuously maintain a degree of vacuum appropriate for the vacuum process. The cryopump can be used to restore the vacuum to the proper level at which the process is allowed to start during a temporary standby of the device between the previous process and the next process. The time required for recovering the degree of vacuum is also called recovery time. The shorter the recovery time, the faster the next process can be started, and the higher the productivity of the apparatus. Therefore, it is desirable that the recovery time is as short as possible. To shorten the recovery time, the pumping speed of the cryopump can be increased. As one means for that purpose, it is generally recognized that the opening ratio of the cryopump inlet is increased.

JP 2010-84702 A JP 2013-160105 A

  Since the cryopump is a reservoir type vacuum pump, gas is accumulated in the cryopump by the vacuum pumping operation of the cryopump. As the gas accumulates, the pumping speed of the cryopump gradually decreases, and the recovery time also gradually increases. Therefore, regeneration of the cryopump is periodically performed in order to discharge the accumulated gas from the cryopump and restore the exhaust speed and the recovery time to the initial levels. The period of evacuation operation from the end of the previous regeneration to the next regeneration is also called a regeneration interval.

  As described above, it has been conventionally recognized that increasing the opening ratio of the cryopump intake port is effective in reducing the recovery time. However, the present inventor has found that such recognition is not necessarily valid later in the playback interval. In fact, in the latter part of the regeneration interval, an increase in the recovery time can be promoted instead of the high aperture ratio.

  One exemplary object of an aspect of the present invention is to produce a vacuum processing apparatus by suppressing an increase in recovery time in the vacuum processing apparatus and extending a regeneration interval of the cryopump based on new knowledge different from conventional recognition. This is to contribute to improving the performance.

  According to an aspect of the present invention, the cryopump includes a cryopump container that defines a cryopump intake port, a first stage and a second stage that are accommodated in the cryopump container, and the second stage is the first stage. A refrigerator that is cooled to a lower temperature, a first cryopanel that is thermally connected to the first stage and surrounded by the cryopump container, and is thermally connected to the second stage, and A second cryopanel surrounded by the cryopanel. The first cryopanel includes an inlet cryopanel having an inlet opening at the cryopump inlet. The inlet opening is formed in the inlet cryopanel such that the ratio of the conductance of the inlet cryopanel to the opening conductance of the cryopump inlet is 6% or less.

  In addition, what replaced the component and expression of this invention between methods, apparatuses, systems, etc. is also effective as an aspect of this invention.

  According to the present invention, an increase in recovery time in the vacuum processing apparatus can be suppressed, and the regeneration interval of the cryopump can be extended.

It is a sectional side view showing typically the principal part of the cryopump concerning an embodiment with the present invention. It is a top view which shows typically the top panel of the 2nd cryopanel which concerns on embodiment with this invention. It is a top view which shows typically the plate member of the 1st cryopanel which concerns on embodiment with this invention. 1 is a diagram schematically illustrating a cryopump during an exhaust operation according to an embodiment of the present invention. It is a schematic diagram which illustrates change of the recovery time in a certain reproduction | regeneration interval concerning embodiment with this invention. It is a top view which shows typically the plate member which concerns on a comparative example. It is a top view which shows typically the plate member of the 1st cryopanel which concerns on other embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. Moreover, the structure described below is an illustration and does not limit the scope of the present invention at all.

  FIG. 1 is a side sectional view schematically showing a main part of a cryopump 10 according to an embodiment of the present invention. The cryopump 10 is attached to, for example, a vacuum chamber of a vacuum processing apparatus and used to increase the degree of vacuum inside the vacuum chamber to a level required for a desired process. The vacuum processing apparatus to which the cryopump 10 is attached is, for example, a sputtering apparatus. The process gas pressure in the sputtering apparatus is, for example, in the range of 1 mTorr to 10 mTorr.

  The cryopump 10 has an intake port 12 for receiving gas. The gas to be exhausted enters the internal space 14 of the cryopump 10 through the air inlet 12 from the vacuum chamber to which the cryopump 10 is attached. FIG. 1 shows a cross section including the central axis A of the internal space 14 of the cryopump 10.

  The diameter of the air inlet 12 is, for example, in the range of 180 mm to 340 mm. Thus, the nominal diameter of the cryopump 10 can be 8 inches, 10 inches, 12 inches, or 320 mm.

  In the following description, the terms “axial direction” and “radial direction” are sometimes used to express the positional relationship of the components of the cryopump 10 in an easily understandable manner. The axial direction represents the direction passing through the intake port 12 (the direction along the dashed line A in FIG. 1), and the radial direction represents the direction along the intake port 12 (the direction perpendicular to the dashed line A). For convenience, the fact that it is relatively close to the inlet 12 in the axial direction may be referred to as “up”, and that it is relatively distant may be called “down”. In other words, the distance from the bottom of the cryopump 10 may be referred to as “up” and the distance from the bottom of the cryopump 10 as “lower”. Regarding the radial direction, the proximity to the center of the intake port 12 (center axis A in FIG. 1) may be referred to as “inside”, and the proximity to the peripheral edge of the intake port 12 may be referred to as “outside”. Such an expression is not related to the arrangement when the cryopump 10 is attached to the vacuum chamber. For example, the cryopump 10 may be attached to the vacuum chamber with the inlet 12 facing downward in the vertical direction.

  Further, the direction surrounding the axial direction may be referred to as “circumferential direction”. The circumferential direction is a second direction along the air inlet 12 and is a tangential direction orthogonal to the radial direction.

  The cryopump 10 includes a refrigerator 16. The refrigerator 16 is a cryogenic refrigerator such as a Gifford-McMahon refrigerator (so-called GM refrigerator). The refrigerator 16 is a two-stage refrigerator that includes a first stage 22 and a second stage 24. The refrigerator 16 is configured to cool the first stage 22 to the first temperature level and cool the second stage 24 to the second temperature level. The second temperature level is lower than the first temperature level. For example, the first stage 22 is cooled to about 65K to 120K, preferably 80K to 100K, and the second stage 24 is cooled to about 10K to 20K.

  The refrigerator 16 includes a first cylinder 23 and a second cylinder 25. The first cylinder 23 connects the room temperature part of the refrigerator 16 to the first stage 22. The second cylinder 25 is a connecting portion that connects the first stage 22 to the second stage 24.

  The illustrated cryopump 10 is a so-called horizontal cryopump. The horizontal cryopump is generally a cryopump in which the refrigerator 16 is disposed so as to intersect (usually orthogonal) the central axis A of the internal space 14 of the cryopump 10.

  The cryopump 10 includes a first cryopanel 18 and a second cryopanel 20 that is cooled to a lower temperature than the first cryopanel 18. Although details will be described later, the first cryopanel 18 includes a radiation shield 30 and a plate member 32 and surrounds the second cryopanel 20. A main accommodating space 21 for the condensed layer 72 is formed between the plate member 32 and the second cryopanel 20 (see FIG. 4).

  First, the second cryopanel 20 will be described. The second cryopanel 20 is provided at the center of the internal space 14 of the cryopump 10. The second cryopanel 20 is attached to the second stage 24 so as to surround the second stage 24. Therefore, the second cryopanel 20 is thermally connected to the second stage 24, and the second cryopanel 20 is cooled to the second temperature level.

  FIG. 2 is a top view schematically showing the top panel 60 of the second cryopanel 20 according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the top panel 60 is directly attached to the upper surface of the second stage 24 of the refrigerator 16, and the second stage 24 is located at the center of the internal space 14 of the cryopump 10. To do. Thus, the main storage space 21 of the condensed layer 72 occupies the upper half of the internal space 14.

  The top panel 60 is provided to condense the gas on the surface. The top panel 60 is a portion of the second cryopanel 20 that is closest to the plate member 32, and includes a top panel front surface 61 that faces the back surface of the plate member 32. The top panel front surface 61 includes a center region 62 and an outer region 63 surrounding the center region 62.

  The top panel 60 is a substantially flat cryopanel arranged perpendicular to the axial direction. The top panel 60 is fixed to the second stage 24 in the center region 62. The central region 62 has a recess, and the top panel 60 is fixed to the second stage 24 using an appropriate fixing member 64 (see FIG. 2). The fixing member 64 is, for example, a bolt. A stepped portion 65 is formed around the recess. The height of the step portion 65 is determined so that the fixing member 64 is accommodated in the recess. An outer region 63 extends radially outward from the step portion 65. A radial end of the outer region 63 is bent downward, and an outer peripheral end 66 of the top panel 60 is formed. As shown in FIG. 2, the top panel 60 is a generally disk-shaped panel.

  Note that the top panel 60 may not have the concave portion of the central region 62 that accommodates the fixing member 64. In this case, the top panel front surface 61 may be a flat surface that does not have the step portion 65. In the present embodiment, the top panel 60 does not include an adsorbent, but for example, an adsorbent may be provided on the back surface thereof.

  The shape of the second cryopanel 20 is adjusted so that the width W1 of the first side gap 43 and the width W2 of the second side gap 44 are matched. That is, the width W1 of the first side gap 43 and the width W2 of the second side gap 44 are substantially equal. For this purpose, the top panel 60 has a notch 74 that widens the first side gap 43. The notch 74 forms a flat portion on the refrigerator 16 side on the outer periphery of the top panel 60. Note that the cryopanel below the top panel 60 may similarly have a notch.

  The second cryopanel 20 includes one or more normal panels 67. The panel 67 is usually provided for condensing or adsorbing gas on the surface. The normal panel 67 is arranged below the top panel 60. The normal panel 67 is different in shape from the top panel 60. Each of the normal panels 67 has, for example, a shape of a side surface of a truncated cone, that is, an umbrella shape. Each normal panel 67 is provided with an adsorbent 68 such as activated carbon. For example, the adsorbent is usually bonded to the back surface of the panel 67. Usually, the front surface of the panel 67 functions as a condensation surface and the back surface functions as an adsorption surface.

  The first cryopanel 18 is a cryopanel provided to protect the second cryopanel 20 from radiant heat from the outside of the cryopump 10 or from the cryopump container 38. The first cryopanel 18 is thermally connected to the first stage 22. Therefore, the first cryopanel 18 is cooled to the first temperature level. The first cryopanel 18 has a gap with the second cryopanel 20, and the first cryopanel 18 is not in contact with the second cryopanel 20.

  The radiation shield 30 is provided to protect the second cryopanel 20 from the radiant heat of the cryopump container 38. The radiation shield 30 is between the cryopump container 38 and the second cryopanel 20 and surrounds the second cryopanel 20. The radiation shield 30 has a slightly smaller diameter than the cryopump vessel 38. The radiation shield 30 has a gap between it and the cryopump container 38, and the radiation shield 30 is not in contact with the cryopump container 38.

  The radiation shield 30 includes a shield front end 28 that defines a shield opening 26, a shield bottom 34 that faces the shield opening 26, and a shield side 36 that extends from the shield front end 28 to the shield bottom 34. The shield opening 26 is a main opening of the cryopump 10 located at the intake port 12. The radiation shield 30 has a cylindrical shape (for example, a cylinder) in which the shield bottom 34 is closed, and is formed in a cup shape.

  The radiation shield 30 includes a mounting seat 37 for the refrigerator 16. The mounting seat 37 is recessed when viewed from the outside of the radiation shield 30, and forms a flat portion on the shield side portion 36 for attaching the refrigerator 16 to the radiation shield 30. The mounting seat 37 is located on the side of the second cryopanel 20. As described above, the top panel 60 is directly attached to the upper surface of the second stage 24 of the refrigerator 16, so that the top panel 60 is at the same height as the second stage 24. Located in the direction.

  The shield side portion 36 forms a closed annular portion as a whole. The first side gap 43 is formed between the mounting seat 37 of the shield side portion 36 and the top panel 60, and the second side gap 44 is between the remaining portion of the shield side portion 36 and the top panel 60. Is formed. The first side gap 43 and the second side gap 44 are also formed between the shield side portion 36 and the normal panel 67. The second lateral gap 44 is continuous with the first lateral gap 43 in the circumferential direction, and an annular gap closed by the first lateral gap 43 and the second lateral gap 44 is formed. The second side gap 44 has a certain width in the circumferential direction.

  As shown in FIG. 1, the mounting seat 37 has a mounting hole 42 of the refrigerator 16, and the second stage 24 and the second cylinder 25 of the refrigerator 16 are inserted into the radiation shield 30 from the mounting hole 42. ing. The first stage 22 of the refrigerator 16 is disposed outside the radiation shield 30. The radiation shield 30 is connected to the first stage 22 via the heat transfer member 45. The heat transfer member 45 is fixed to the outer periphery of the mounting hole 42 by a flange at one end, and is fixed to the first stage 22 by a flange at the other end. The heat transfer member 45 is, for example, a hollow short cylinder, and extends between the radiation shield 30 and the first stage 22 along the central axis of the refrigerator 16. Thus, the radiation shield 30 is thermally connected to the first stage 22. The radiation shield 30 may be directly attached to the first stage 22.

  Between the second cylinder 25 and the mounting hole 42, an upper gap 46 is formed on the side close to the shield opening 26, and a lower gap 48 is formed on the side far from the shield opening 26. Since the refrigerator 16 is inserted into the center of the mounting hole 42, the width of the upper gap 46 is equal to the width of the lower gap 48.

  In the present embodiment, the radiation shield 30 is formed in an integral cylindrical shape as shown. Instead of this, the radiation shield 30 may be configured to have a tubular shape as a whole by a plurality of parts. The plurality of parts may be arranged with a gap therebetween. For example, the radiation shield 30 may be divided into two parts in the axial direction. In this case, the upper portion of the radiation shield 30 is a cylinder having both ends opened, and includes the shield front end 28 and the first portion of the shield side portion 36. The lower portion of the radiation shield 30 has an upper end opened and a lower end closed, and includes a second portion of the shield side portion 36 and a shield bottom portion 34. A gap extending in the circumferential direction is formed between the first portion and the second portion of the shield side portion 36. The upper half of the mounting hole 42 of the refrigerator 16 is formed in the first part of the shield side part 36, and the lower half is formed in the second part of the shield side part 36.

  The cryopump 10 is provided with a refrigerator cover 70 that surrounds the second cylinder 25 of the refrigerator 16. The refrigerator cover 70 is formed in a cylindrical shape having a slightly larger diameter than the second cylinder 25, and one end is attached to the second stage 24, passing through the attachment hole 42 of the radiation shield 30 toward the first stage 22. It extends. A gap is provided between the refrigerator cover 70 and the radiation shield 30, and the refrigerator cover 70 and the radiation shield 30 are not in contact with each other. The refrigerator cover 70 is thermally connected to the second stage 24 and is cooled to the same temperature as the second stage 24. Therefore, the refrigerator cover 70 is also regarded as a part of the second cryopanel 20.

  The first cryopanel 18 includes an inlet cryopanel having an inlet opening at the air inlet 12. The inlet cryopanel includes a perforated member disposed at the air inlet 12. The inlet opening is at least one opening formed in the perforated member. The perforated member may be a single perforated plate (eg, plate member 32) that covers the shield opening 26. The at least one opening is, for example, a number of holes (eg, small holes 54). The side surface of the inlet cryopanel that defines the inlet opening may be black. The back surface of the entrance cryopanel (that is, the surface facing the second cryopanel 20) may be black.

  The inlet opening is formed in the inlet cryopanel so that the ratio of the conductance of the inlet cryopanel to the opening conductance of the inlet 12 is 1% or more and 6% or less. Preferably, the inlet opening is formed in the inlet cryopanel so that the ratio of the conductance of the inlet cryopanel to the opening conductance of the inlet 12 is 4% or more and 6% or less.

  The plate member 32 is provided in the shield opening 26 in order to protect the second cryopanel 20 from radiant heat from a heat source outside the cryopump 10. The heat source outside the cryopump 10 is, for example, a heat source in a vacuum chamber to which the cryopump 10 is attached. In addition to radiant heat, the ingress of gas molecules is limited. The plate member 32 occupies a part of the opening area of the air inlet 12 so as to limit the gas inflow into the internal space 14 through the air inlet 12 to a desired amount. The plate member 32 covers most of the air inlet 12. A gas (for example, moisture) that condenses at the cooling temperature of the plate member 32 is captured on the surface thereof.

  There is a slight gap in the axial direction between the shield front end 28 and the plate member 32. The plate member 32 includes a skirt portion 33 to cover the gap and regulate the gas flow. The skirt portion 33 is a short cylinder surrounding the plate member 32. The skirt 33 and the plate member 32 form a circular tray-like integrated structure with the plate member 32 as a bottom surface. This circular tray structure is arranged so as to cover the radiation shield 30. Therefore, the skirt portion 33 protrudes downward in the axial direction from the plate member 32 and extends adjacent to the shield front end 28 in the radial direction. The radial distance between the skirt portion 33 and the shield front end 28 is, for example, about the dimensional tolerance of the radiation shield 30.

  The gap between the shield front end 28 and the plate member 32 may vary due to manufacturing errors. Such errors can be reduced by precision component processing and assembly, but this may not always be practical considering the increased manufacturing costs. The error leads to individual differences of the cryopump 10. If the skirt portion 33 is not provided, the amount of gas flowing into the radiation shield 30 changes depending on the size of the gap. The amount of gas inflow is directly related to the exhaust speed of the cryopump 10. If the gap is too large or too small, the actual exhaust speed will deviate from the design performance. When the skirt portion 33 covers the gap between the shield front end 28 and the plate member 32, the gas flow through the gap is restricted, and individual differences are reduced. As a result, the individual difference of the cryopump exhaust speed with respect to the design performance can be reduced.

  The shield front end 28 and the plate member 32 are disposed above the intake flange 40 of the cryopump container 38 in the axial direction. The shield front end 28 and the plate member 32 are located outside the cryopump container 38. Thus, the radiation shield 30 extends toward the vacuum chamber to which the cryopump 10 is attached. By extending the radiation shield 30 upward, the main housing space 21 of the condensed layer 72 can be widened in the axial direction. However, the axial length of the extending portion is determined so as not to interfere with the vacuum chamber (or the gate valve between the vacuum chamber and the cryopump 10).

  The cryopump container 38 is a housing of the cryopump 10 that houses the first cryopanel 18 and the second cryopanel 20, and is a vacuum container configured to maintain the vacuum airtightness of the internal space 14. Further, the first stage 22 and the second stage 24 of the refrigerator 16 are accommodated in a cryopump container 38.

  The inlet 12 is defined by the front end 39 of the cryopump container 38. The cryopump container 38 includes an inlet flange 40 that extends radially outward from the front end 39. The intake flange 40 is provided over the entire circumference of the cryopump container 38. The cryopump 10 is attached to the vacuum chamber using the inlet flange 40. There is a radial gap between the front end 39 of the cryopump container 38 and the plate member 32, and the plate member 32 is not in contact with the cryopump container 38.

  FIG. 3 is a top view schematically showing a plate member 32 according to an embodiment of the present invention. In FIG. 3, typical constituent elements below the plate member 32 are indicated by broken lines. The plate member 32 is a single flat plate (for example, a circular plate) that crosses the shield opening 26. The front surface of the plate member 32 faces the external space of the cryopump 10, and the back surface of the plate member 32 faces the top panel 60. The height of the main housing space 21 is determined by the axial distance between the plate member 32 and the top panel 60.

  The dimension (for example, diameter) of the plate member 32 is substantially equal to the dimension of the shield opening 26. The plate member 32 has a plate center portion 50 and a plate outer peripheral portion 52. The plate central portion 50 is a radially inner portion of the plate member 32, and the plate outer peripheral portion 52 is a radially outer portion of the plate member 32 surrounding the plate central portion 50.

  The plate outer peripheral part 52 is attached to the plate attaching part 29 of the shield front end 28. The plate attachment portions 29 are convex portions protruding radially inward from the shield front end 28, and are formed at regular intervals (for example, every 90 °) in the circumferential direction. The plate member 32 is fixed to the plate mounting portion 29 by an appropriate method. For example, each of the plate attachment portion 29 and the plate outer peripheral portion 52 has a bolt hole (not shown), and the plate outer peripheral portion 52 is bolted to the plate attachment portion 29.

  A large number of small holes 54 that allow gas flow are formed in the plate member 32. The small hole 54 is a through hole formed in the plate center portion 50. Therefore, the gas to be condensed in the second cryopanel 20 can be received in the main housing space 21 between the plate member 32 and the second cryopanel 20 through the small holes 54. The small holes 54 are not formed in the plate outer peripheral portion 52.

  The small holes 54 are regularly arranged. In the present embodiment, the small holes 54 are provided at equal intervals in each of two orthogonal linear directions to form a lattice of the small holes 54. As an alternative, the small holes 54 may be provided at equal intervals in each of the radial direction and the circumferential direction.

  The shape of the small hole 54 is, for example, a circular shape, but is not limited thereto. The small hole 54 is formed in an opening having a rectangular shape or other shape, a slit extending linearly or in a curved shape, or the outer periphery of the plate member 32. It may be a notch. The size of the small hole 54 is clearly smaller than the shield opening 26.

  The small hole 54 has a ratio of the total area of the small holes 54 to the opening area of the intake port 12 (also referred to as an opening ratio of the intake port 12) of 1% or more and 6% or less (preferably 4% or more and 6% or less). Thus, the plate member 32 is formed. In this way, the small holes 54 are formed in the plate member 32 so that the ratio of the conductance of the plate member 32 to the opening conductance of the air inlet 12 is 1% or more and 6% or less (preferably 4% or more and 6% or less). Is formed.

  The back surface of the plate member 32 and the inner surface of the radiation shield 30 may be subjected to a surface treatment that increases the emissivity, such as a black body treatment. Thereby, the emissivity of the back surface of the plate member 32 and the inner surface of the radiation shield 30 is substantially equal to 1. A similar surface treatment may be performed on the side surface of the plate member that defines the small hole 54 in the plate member 32. The black surface of the plate member 32 may be formed by, for example, black chrome plating on the surface of a copper base material, or may be formed by black coating. Such a black surface serves to absorb heat that has entered the cryopump 10.

  On the other hand, the front surface of the plate member 32 may be subjected to a surface treatment for reducing the emissivity in order to reflect radiant heat from the outside. Such a low emissivity surface may be formed, for example, by nickel plating the surface of a copper substrate.

  The operation of the cryopump 10 having the above configuration will be described below. When the cryopump 10 is operated, the vacuum chamber is first roughed to about 1 Pa, for example, with another appropriate roughing pump before the operation. Thereafter, the cryopump 10 is operated. The first stage 22 and the second stage 24 are cooled by driving the refrigerator 16, and the first cryopanel 18 and the second cryopanel 20 that are thermally connected thereto are also cooled. The first cryopanel 18 and the second cryopanel 20 are cooled to the first temperature and the second temperature lower than the first temperature, respectively.

  The plate member 32 cools gas molecules flying from the vacuum chamber toward the inside of the cryopump 10, and condenses and exhausts gas (for example, moisture) whose vapor pressure is sufficiently low at the cooling temperature to the surface. The gas whose vapor pressure does not become sufficiently low at the cooling temperature of the plate member 32 passes through the many small holes 54 and enters the main accommodating space 21. A part of the gas incident on the cryopump 10 is reflected by the plate member 32 and does not enter the main housing space 21.

  Of the gas molecules that have entered, a gas whose vapor pressure is sufficiently low at the cooling temperature of the second cryopanel 20 (for example, argon) is condensed on the surface of the second cryopanel 20 (mainly, the front surface 61 of the top panel). Exhausted. A gas (for example, hydrogen) whose vapor pressure does not sufficiently decrease even at the cooling temperature is adsorbed by the adsorbent 68 that is bonded to the surface of the second cryopanel 20 and cooled, and then exhausted. In this manner, the cryopump 10 can reach the desired vacuum level in the vacuum chamber.

  FIG. 4 is a diagram schematically showing the cryopump 10 during the exhaust operation. As shown in FIG. 4, ice or frost made of condensed gas is deposited on the top panel 60 of the cryopump 10. As shown in FIG. 4, a dome-type or mushroom-type condensed layer 72 grows on the top panel 60. The main component of the condensed layer 72 is, for example, argon. This ice layer grows and increases in thickness with the exhaust operation time. In FIG. 4, for the sake of simplification, the illustration of the condensed layer deposited on the normal panel 67 and the refrigerator cover 70 is omitted.

  As the condensed layer 72 grows, a temperature gradient is generated in the condensed layer 72 in the depth direction. As a result, the surface temperature of the condensed layer 72 becomes higher than the surface temperature of the top panel 60. This means that the gas is directly condensed on the front surface 61 of the low temperature top panel at the beginning of the regeneration interval, whereas the gas is condensed on the surface of the condensate layer 72 at a higher temperature later in the regeneration interval. It will be like that. Therefore, when the vacuum pumping operation of the cryopump 10 is continued, the pumping speed of the cryopump 10 gradually decreases. The recovery time increases as the exhaust speed decreases.

  Therefore, the recovery time can be used as one index for determining whether or not the cryopump 10 needs to be regenerated. In this case, the continuation of operation of the cryopump 10 is allowed while the recovery time is shorter than the specified value. However, when the recovery time becomes longer than the specified value, the vacuum pumping operation of the cryopump 10 is stopped and the cryopump 10 is regenerated. This specified value may be defined as a vacuum process specification in the vacuum processing apparatus.

  The regeneration of the cryopump 10 is downtime for the vacuum processing apparatus. Therefore, in order to improve the productivity of the vacuum processing apparatus, it is desired to lengthen the regeneration interval of the cryopump 10 while suppressing an increase in recovery time.

  It is generally recognized that the pumping speed of the cryopump 10 can be increased to shorten the recovery time. One means for this is to increase the ratio of the conductance of the plate member 32 to the open conductance of the inlet 12 of the cryopump 10. In short, by increasing the opening ratio of the intake port 12, the exhaust speed of the cryopump 10 can be increased and the recovery time can be shortened.

  This is correct at the beginning of the playback interval. However, it is not necessarily correct in the latter part of the regeneration interval, considering that the condensed layer 72 is growing. This is because if the aperture ratio is large, the thermal load entering the cryopump 10 increases, and thereby the temperature gradient of the condensed layer 72 increases. Moreover, if the aperture ratio is large, the amount of gas entering the cryopump 10 also increases. This also has the effect of expanding the temperature gradient of the condensed layer 72. As described above, the expansion of the temperature gradient in the condensed layer 72 causes an increase in the surface temperature of the condensed layer 72 and an increase in recovery time. In the latter part of the regeneration interval, the condensed layer 72 grows greatly as shown in FIG. 4, so that the recovery time can increase significantly.

  Therefore, in the present embodiment, it is aimed to suppress an increase in the recovery time by suppressing the expansion of the temperature gradient of the condensed layer 72. By reducing the temperature difference between the condensed layer 72 and the top panel 60, the decrease in the exhaust speed of the cryopump 10 accompanying the growth of the condensed layer 72 is mitigated. For this reason, in the present embodiment, the conductance ratio is practically set to a small value. For example, as described above, the ratio of the conductance of the plate member 32 to the opening conductance of the intake port 12 is set to 1% or more and 6% or less (for example, 4% or more and 6% or less).

  When the dome-shaped condensed layer 72 further grows in the radial direction, the outer peripheral portion of the condensed layer 72 can come into contact with the shield side portion 36. If the gap between the mounting seat 37 and the top panel 60 is narrow, the condensed layer 72 first contacts the mounting seat 37. The gas is vaporized again at the contact site and is released to the outside of the main housing space 21 and the cryopump 10. Therefore, thereafter, the cryopump 10 cannot provide the designed exhaust performance. Accordingly, the gas storage amount at this time gives the maximum storage amount of the cryopump 10. A local portion of the condensed layer 72 (in this case, the condensed layer 72 near the mounting seat 37) determines the gas storage limit of the cryopump 10.

  The cryopump is generally designed to be axisymmetric. However, the horizontal cryopump 10 inevitably has an asymmetric portion (for example, the mounting seat 37) because the refrigerator 16 is disposed sideways. In the present embodiment, the shape of the top panel 60 is matched to such an asymmetric part, and the width of the gap between the top panel 60 and the radiation shield 30 is aligned in the circumferential direction. Only a specific portion of the condensed layer 72 that grows in the radial direction on the top panel 60 (in this case, the condensed layer 72 near the mounting seat 37) can be prevented from contacting the radiation shield 30 in advance. As a result, according to this embodiment, the gas occlusion amount of the cryopump 10 can be improved.

  FIG. 5 is a schematic diagram illustrating a change in recovery time in a certain playback interval according to an embodiment of the present invention. The vertical axis in FIG. 5 represents the recovery time, and the horizontal axis represents the operation time of the cryopump 10. It can be said that the horizontal axis of FIG. 5 represents the cumulative number of times recovery is performed during the vacuum pumping operation of the cryopump 10. In FIG. 5, the change in the recovery time according to the present embodiment is indicated by a solid line, and the change in the recovery time according to the comparative example is indicated by a broken line. The comparative example is a case where the opening ratio of the cryopump inlet is relatively high (for example, greater than 7%). A reproduction interval according to this embodiment is illustrated by an arrow B, and a reproduction interval according to a comparative example is illustrated by an arrow C.

  FIG. 6 is a top view schematically showing the plate member 132 according to the comparative example. As shown in FIG. 6, the plate member 132 has a large number of small holes 154 formed not only in the plate center portion 150 but also in the plate outer peripheral portion 152. Thus, when the small holes 154 are distributed over the entire area of the plate member 132, the opening ratio of the intake ports exceeds 7%.

  As shown in FIG. 5, in the cryopump 10 according to the present embodiment, the recovery time at the beginning of the regeneration interval is somewhat longer than in the comparative example. When the vacuum pumping operation of the cryopump 10 is continued, the pumping speed of the cryopump 10 gradually decreases toward the latter part of the regeneration interval, and the recovery time gradually increases. Thus, when the recovery time reaches the specified value T, the playback interval ends (that is, playback starts).

  According to this embodiment, the opening ratio of the inlet cryopanel with respect to the opening of the intake port 12 is small. The opening ratio of the inlet cryopanel is the ratio of the area of the opening portion of the inlet cryopanel to the area of the inlet cryopanel when viewed in the axial direction. Since the opening ratio of the inlet cryopanel is small, the gas flow rate from the outside of the cryopump 10 to the main accommodating space 21 is also low. Therefore, the growth rate of the condensed layer 72 is small. Moreover, the heat load by gas is also small. Furthermore, the heat load by the incoming radiant heat is also small. Therefore, the temperature gradient in the condensed layer 72 is reduced, and the surface temperature of the condensed layer 72 is maintained at a low temperature. Therefore, an increase in recovery time in the latter part of the playback interval can be suppressed. Thereby, the reproduction interval B in this embodiment is extended compared with the reproduction interval C in a comparative example.

  According to the inventor's consideration and trial calculation, when the diameter of the intake port is in the range of 180 mm to 340 mm, the effect of extending the regeneration interval by reducing the aperture ratio can be obtained. Further, according to the inventor's consideration and trial calculation, the present embodiment is effective for evacuation in a range of 1 mTorr to 10 mTorr, for example.

  As described above, according to the embodiment of the present invention, it is possible to suppress an increase in the recovery time in the vacuum processing apparatus and lengthen the regeneration interval of the cryopump 10 based on new knowledge different from the conventional recognition. . Therefore, the cryopump 10 contributing to the productivity improvement of the vacuum processing apparatus can be provided.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

  FIG. 7 is a top view schematically showing a plate member 232 of the first cryopanel according to another embodiment of the present invention. The plate member 232 includes a first plate 234 having at least one opening through which gas passes, and a second plate 236 adjacent to the first plate 234 and covering the shield opening in cooperation with the first plate 234. Unlike the first plate 234, the second plate 236 does not have an opening through which gas passes.

  The first plate 234 is a perforated disk having a diameter smaller than the diameters of the cryopump inlet and the shield opening. The first plate 234 has a large number of small holes 254. The second plate 236 is an annular plate that covers the intake port together with the first plate 234. The second plate 236 has an outer diameter that is approximately equal to the diameter of the inlet and shield openings. The second plate 236 occupies at least 15% of the cryopump inlet.

  The first plate 234 may be a plate member 32 adapted to a cryopump having a first nominal diameter and / or a radiation shield. By combining the first plate 234 with the second plate 236, a plate member 232 that is compatible with a cryopump and / or radiation shield having a second nominal diameter that is larger than the first nominal diameter can be obtained. The first nominal diameter may be, for example, 8 inches, and the second nominal diameter may be, for example, 10 inches.

  10 cryopumps, 12 air inlets, 16 refrigerators, 18 first cryopanels, 20 second cryopanels, 22 first stages, 24 second stages, 32 plate members, 38 cryopump containers, 54 small holes.

Claims (10)

A cryopump container defining a cryopump inlet; and
A refrigerator comprising a first stage and a second stage housed in the cryopump container, wherein the second stage is cooled to a lower temperature than the first stage;
A first cryopanel thermally connected to the first stage and surrounded by the cryopump vessel;
A second cryopanel thermally connected to the second stage and surrounded by the first cryopanel;
The first cryopanel includes an inlet cryopanel having an inlet opening at the cryopump inlet.
The cryopump is characterized in that the inlet opening is formed in the inlet cryopanel so that a ratio of conductance of the inlet cryopanel to opening conductance of the cryopump inlet is 6% or less.   The inlet opening portion is formed in the inlet cryopanel so that a ratio of a conductance of the inlet cryopanel to an opening conductance of the cryopump inlet is 1% or more or 4% or more. Item 2. The cryopump according to Item 1. The inlet cryopanel includes a perforated member disposed at the cryopump inlet, and the inlet opening is at least one opening formed in the perforated member,
The cryopump according to claim 1 or 2, wherein an area ratio of the at least one opening to the cryopump intake port is 6% or less.   The cryopump according to claim 3, wherein the area ratio is 1% or more or 4% or more.   The cryopump according to claim 3 or 4, wherein the perforated member is a single perforated plate that covers the cryopump intake port. The cryopump inlet is a circular opening having a first diameter;
The perforated member includes a circular plate having a second diameter smaller than the first diameter, and an annular plate that covers the cryopump inlet together with the circular plate, and the at least one opening is the circular plate. The cryopump according to claim 3 or 4, wherein the cryopump is formed on a plate.   The cryopump according to claim 3, wherein the at least one opening is a plurality of holes.   The cryopump according to any one of claims 1 to 7, wherein a diameter of the cryopump inlet is in a range of 180 mm to 340 mm.   The cryopump according to claim 1, wherein a side surface of the inlet cryopanel that defines the inlet opening is black.   The cryopump according to any one of claims 1 to 9, wherein the inlet cryopanel is disposed above a front end of a cryopump container that defines the cryopump intake port.

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