TWI631280B - Cryopump - Google Patents

Abstract

It is an object of the present invention to suppress an increase in recovery time in a vacuum processing apparatus and to extend a regeneration interval of the cryopump. The cryopump (10) of the present invention includes a cryopump container (38) that defines an intake port (12), and a refrigerator (16) that includes a first cooling stage (22) housed in the cryopump housing (38) and The second cooling stage (24), the second cooling stage (24) is cooled to a temperature lower than the first cooling stage (22); the first low temperature plate (18) is thermally connected to the first cooling stage (22), and is The cryopump container (38) is surrounded; and the second cryopanel (20) is thermally connected to the second cooling stage (24) and surrounded by the first cryopanel (18). The first cryopanel (18) is provided with a plate member (32) having an inlet opening at the intake port (12). The inlet opening portion is formed in the plate member (32) such that the ratio of the air guide of the plate member (32) to the opening air guide of the intake port (12) is 6% or less.

Description

Cryopump

The present application claims priority based on Japanese Patent Application No. 2014-206158, filed on Jan. 7, 2014. The entire contents of this Japanese application are incorporated herein by reference.

The present invention relates to a cryopump.

As a use of a cryopump, there is a vacuum processing device such as a sputtering device. In a vacuum processing apparatus, a vacuum process can be performed repeatedly. The primary function of the cryopump in such a device is to continuously ensure a vacuum suitable for the vacuum process. During the temporary standby of the device between the last process and the next process, the cryopump can be used in order to restore the vacuum to an appropriate degree of vacuum that would allow the process to begin. The time required to restore the vacuum is called the recovery time. The shorter the recovery time, the more the next process can be started in advance, so the productivity of the device is improved. Thus, it is desirable to have a recovery time as short as possible. In order to shorten the recovery time, it is only necessary to increase the exhaust speed of the cryopump. Therefore, one of the commonly recognized means is to increase the aperture ratio of the suction port of the cryopump.

(previous technical literature) (Patent Literature)

Patent Document 1: Japanese Laid-Open Patent Publication No. 2010-84702

Patent Document 2: Japanese Laid-Open Patent Publication No. 2013-160105

Since the cryopump is a trap type vacuum pump, the gas is accumulated in the cryopump by the vacuum exhaust operation of the cryopump. As the gas accumulates, the exhaust velocity of the cryopump gradually decreases, and at the same time, the recovery time becomes longer. Therefore, in order to discharge the accumulated gas from the cryopump, and to restore the exhaust velocity and the recovery time to the initial stage, the cryopump is periodically regenerated. The vacuum evacuation operation period from the end of the previous regeneration to the next regeneration is also referred to as the regeneration interval.

As described above, it has been conventionally considered that increasing the aperture ratio of the intake port of the cryopump will contribute to shortening the recovery time. However, the inventors have found that such an opinion is not reasonable at the later stage of the regeneration interval. In fact, in the later stage of the regeneration interval, if the aperture ratio is high, the recovery time is promoted instead.

One of the exemplary purposes of one aspect of the present invention is to suppress an increase in recovery time in a vacuum processing apparatus and to extend the regeneration interval of the cryopump by a new insight different from the conventional insights, thereby contributing to an improvement The productivity of the vacuum processing unit.

According to one aspect of the invention, the cryopump is configured to: determine the cryogenic pump suction a cryopump container; the refrigerator includes a first cooling stage and a second cooling stage housed in the cryopump housing, and the second cooling stage is cooled to a temperature lower than the first cooling stage; the first cryopanel; The second cryopanel is thermally connected to the first cooling stage and surrounded by the cryopump housing, and the second cryopanel is thermally connected to the second cooling stage and surrounded by the first cryopanel. The first cryopanel is provided with an inlet cryopanel having an inlet opening in the intake port of the cryopump. The inlet opening portion is formed in the inlet cryopanel so that the ratio of the air guide of the inlet cryopanel to the opening air guide of the cryopump intake port is 6% or less.

Further, the constituent elements or expressions of the present invention are mutually substituted between methods, apparatuses, systems, etc., and are equally effective as aspects of the present invention.

According to the present invention, it is possible to suppress an increase in the recovery time in the vacuum processing apparatus, and it is possible to extend the regeneration interval of the cryopump.

10‧‧‧Cryogenic pump

12‧‧‧ suction port

16‧‧‧Freezer

18‧‧‧1st cryogenic plate

20‧‧‧2nd cryogenic plate

22‧‧‧1st cooling station

24‧‧‧2nd cooling station

32‧‧‧ Board components

38‧‧‧Cryogenic pump container

54‧‧‧Small hole

Fig. 1 is a side cross-sectional view schematically showing a main part of a cryopump according to an embodiment of the present invention.

Fig. 2 is a plan view schematically showing a top plate of a second cryopanel according to an embodiment of the present invention.

Fig. 3 is a plan view schematically showing a plate member of a first cryopanel according to an embodiment of the present invention.

Figure 4 is a view showing an embodiment of the present invention and schematically shows Diagram of the cryopump in exhaust operation.

Fig. 5 is a view showing an embodiment of the present invention, and exemplifies a change in recovery time in a regeneration interval.

Fig. 6 is a plan view schematically showing a plate member of a comparative example.

Fig. 7 is a plan view schematically showing a plate member of a first cryopanel according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements are denoted by the same reference numerals, and the repeated description is omitted as appropriate. Also, the structures described below are examples and are not intended to limit the scope of the invention.

Fig. 1 is a side cross-sectional view schematically showing a main part of a cryopump 10 according to an embodiment of the present invention. The cryopump 10 is, for example, mounted in a vacuum chamber of a vacuum processing apparatus, which is used to increase the degree of vacuum inside the vacuum chamber to the extent required for the desired process. The vacuum processing apparatus to which the cryopump 10 is mounted is, for example, a sputtering apparatus. The processing 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 a gas. The gas to be discharged enters the internal space 14 of the cryopump 10 after passing through the suction port 12 from the vacuum chamber in which the cryopump 10 is installed. The first figure shows a cross section including the central axis A of the internal space 14 of the cryopump 10.

The diameter of the suction port 12 is, for example, in the range of 180 mm to 340 mm. Thereby, the nominal diameter of the cryopump 10 can be 8 inches, 10 inches. Inch, 12 inches, or 320mm.

In addition, hereinafter, in order to facilitate understanding, the positional relationship of the components of the cryopump 10 is used, and terms such as "axial direction" and "radial direction" may be used. The axial direction indicates the direction through the intake port 12 (the direction along the dotted line A in Fig. 1), and the radial direction indicates the direction along the intake port 12 (the direction perpendicular to the one-dotted line A). For the sake of convenience, with respect to the axial direction, the side relatively close to the suction port 12 is sometimes referred to as "upper", and the side farther away is referred to as "lower". That is, the side relatively far from the bottom of the cryopump 10 is sometimes referred to as "upper", and the relatively close side is referred to as "lower". Regarding the radial direction, a side close to the center of the intake port 12 (the central axis A in FIG. 1) may be referred to as "inner", and a side close to the periphery of the intake port 12 may be referred to as "outer". In addition, this performance is independent of the configuration when the cryopump 10 is installed in the vacuum chamber. For example, the cryopump 10 may be attached to the vacuum chamber with the intake port 12 facing downward in the vertical direction.

Further, the direction around the axial direction is sometimes referred to as "circumferential direction". The circumferential direction is along the second direction of the intake port 12 and a tangential direction orthogonal to the radial direction.

The cryopump 10 is provided with a refrigerator 16 . The refrigerator 16 is, for example, an ultra-low temperature refrigerator such as a Gifford-McMahon type refrigerator (so-called GM refrigerator). The refrigerator 16 is a two-stage refrigerator including a first cooling stage 22 and a second cooling stage 24 . The refrigerator 16 is configured to cool the first cooling stage 22 to the first temperature stage and to cool the second cooling stage 24 to the second temperature stage. The temperature in the second temperature stage is lower than the temperature in the first temperature stage. 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.

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

The illustrated cryopump 10 is a so-called horizontal cryopump. The horizontal cryopump is generally configured as a cryopump in which the refrigerator 16 is disposed 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 temperature lower than the first cryopanel 18 . As will be described in detail later, the first cryopanel 18 includes the radiation shield 30 and the plate member 32, and surrounds the second cryopanel 20. A main accommodating space 21 of the condensing 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 a central portion of the internal space 14 of the cryopump 10 . The second cryopanel 20 is attached to the second cooling stage 24 so as to surround the second cooling stage 24 . Thereby, the second cryopanel 20 is thermally connected to the second cooling stage 24, and the second cryopanel 20 is cooled to the second temperature stage.

Fig. 2 is a plan view schematically showing a top plate 60 of a second cryopanel 20 according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the top plate 60 is directly attached to the upper surface of the second cooling stage 24 of the refrigerator 16, and the second cooling stage 24 is located at the center of the internal space 14 of the cryopump 10. Thereby, the main accommodating space 21 of the condensing layer 72 occupies the upper half of the internal space 14.

The top plate 60 is provided to condense gas on its surface. roof 60 is a portion of the second cryopanel 20 closest to the plate member 32, and has a top plate front surface 61 opposed to the back surface of the plate member 32. The top front surface 61 is provided with a central area 62 and an outer area 63 surrounding the central area 62.

The top plate 60 is a substantially flat low temperature plate that is disposed perpendicular to the axial direction. The top plate 60 is fixed to the second cooling stage 24 in the center area 62. The center region 62 has a recess in which the top plate 60 is fixed to the second cooling stage 24 by an appropriate fixing member 64 (see Fig. 2). The fixing member 64 is, for example, a bolt. A stepped portion 65 facing upward is formed in the periphery of the recess. The height of the step portion 65 is defined to accommodate the fixing member 64 in the recess. The outer side region 63 extends from the step portion 65 toward the radially outer side. The radial end of the outer side region 63 is bent downward, and the outer peripheral end portion 66 of the top plate 60 is formed. As shown in Fig. 2, the top plate 60 is a substantially circular plate.

Additionally, the top plate 60 may not have a recess that receives the central region 62 of the stationary member 64. In this case, the top front surface 61 may also be a flat surface having no step portion 65. Further, in the present embodiment, the top plate 60 does not have an adsorbent, but an adsorbent may be provided on the back surface, for example.

The shape of the second cryopanel 20 is adjusted such that the width W1 of the first lateral gap 43 coincides with the width W2 of the second lateral gap 44. That is, the width W1 of the first side gap 43 and the width W2 of the second side gap 44 are substantially equal. Therefore, the top plate 60 has a notch portion 74 that expands the width of the first side gap 43. The notch portion 74 forms a flat portion on the outer periphery of the top plate 60 toward the refrigerator 16 side. Further, the low temperature plate that is lower than the top plate 60 may have a notch portion as well.

Also, the second cryopanel 20 includes one or a plurality of conventional plates 67. The conventional plate 67 is provided to condense or adsorb gas to its surface. The conventional plate 67 is arranged below the top plate 60. The shape of the conventional board 67 is different from that of the top board 60. The conventional plates 67 each have, for example, a shape of a side surface of a truncated cone, a so-called umbrella shape. An adsorbent 68 such as activated carbon is provided on each of the conventional plates 67. The adsorbent is adhered to, for example, the back side of the conventional plate 67. The front surface of the conventional plate 67 functions as a condensation surface and a back surface 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 the cryopump housing 38. The first cryopanel 18 is thermally connected to the first cooling stage 22 . Thereby, the first cryopanel 18 is cooled to the first temperature stage. There is a gap between the first cryopanel 18 and 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 housing 38. The radiation shield 30 is located between the cryopump housing 38 and the second cryopanel 20 and surrounds the second cryopanel 20. Radiation shield 30 has a slightly smaller diameter than cryopump housing 38. There is a gap between the radiation shield 30 and the cryopump housing 38, and the radiation shield 30 is not in contact with the cryopump container 38.

The radiation shield 30 is provided with a shield front end 28 defining a shield opening 26, a shield bottom 34 opposite the shield opening 26, and a shield side 36 extending from the shield front end 28 toward the shield bottom 34. The shield opening 26 is located at the main opening of the cryopump 10 of the suction port 12. The radiation shield 30 has a cylindrical (e.g., cylindrical) shape in which the shield bottom 34 is closed. And formed into a cup shape.

The radiation shield 30 is provided with a mount 37 of the refrigerator 16 . When viewed from the outside of the radiation shield 30, the mount 37 is recessed, and a flat portion for mounting the refrigerator 16 to the radiation shield 30 is formed on the shield side portion 36. The mount 37 is located on the side of the second cryopanel 20. As described above, since the top plate 60 is directly attached to the upper surface of the second cooling stage 24 of the refrigerator 16, the top plate 60 is located at the same height as the second cooling stage 24, and the mount 37 is located on the side of the top plate 60.

The shield side portion 36 forms an integrally closed annular portion. The first side gap 43 is formed between the mount 37 of the shield side portion 36 and the top plate 60, and the second side gap 44 is formed between the remaining portion of the shield side portion 36 and the top plate 60. The first side gap 43 and the second side gap 44 are also formed between the shield side portion 36 and the conventional plate 67. The second side gap 44 is connected to the first side gap 43 in the circumferential direction, and a closed annular gap is formed by the first side gap 43 and the second side gap 44. The second side gap 44 has a constant width in the circumferential direction.

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

Between the second cylinder 25 and the mounting hole 42, an upper gap 46 is formed on a side close to the shield opening 26, and a lower gap 48 is formed on a side away 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 integrated cylindrical shape as illustrated. Alternatively, the radiation shield 30 may be configured to have a cylindrical shape as a whole by a plurality of components. These plurality of parts can also be arranged with a gap therebetween. For example, the radiation shield 30 can also be divided into two portions in the axial direction. In this case, the upper portion of the radiation shield 30 is a cylinder that is open at both ends, and includes a shield front end 28 and a first portion of the shield side portion 36. The lower portion of the radiation shield 30 is open at the upper end and closed at the lower end, and has 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 portion of the shield side portion 36, and the lower half is formed in the second portion of the shield side portion 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 diameter slightly larger than that of the second cylinder 25, and one end is attached to the second cooling stage 24, and extends to the first cooling stage 22 after passing through the attachment hole 42 of the radiation shield 30. In the cold A gap is provided between the refrigerator cover 70 and the radiation shield 30, and the refrigerator cover 70 is not in contact with the radiation shield 30. The refrigerator cover 70 is thermally connected to the second cooling stage 24 and is cooled to the same temperature as the second cooling stage 24. Thereby, the refrigerator cover 70 can be regarded as a part of the second cryopanel 20.

The first cryopanel 18 includes an inlet cryopanel having an inlet opening at the intake port 12. The inlet cryopanel has a perforated member disposed in the intake port 12. The inlet opening is at least one opening formed in the apertured member. The apertured member may also be a single apertured plate (e.g., plate member 32) that covers the shield opening 26. The at least one opening is, for example, a plurality of holes (eg, small holes 54). In addition, the side surface of the inlet cryopanel that determines the inlet opening portion may be black. Alternatively, the back surface of the inlet cryopanel (that is, the surface facing the second cryopanel 20) may be black.

The inlet opening portion is formed in the inlet cryopanel so that the ratio of the air conduction of the inlet cryopanel to the opening air conduction of the intake port 12 is 1% or more and 6% or less. It is preferable that the inlet opening portion is formed in the inlet cryopanel so that the ratio of the air guide of the inlet cryopanel to the opening air guide of the intake port 12 is 4% or more and 6% or less.

The plate member 32 is provided to the shield opening 26 in order to protect the second cryopanel 20 from radiant heat from a heat source external to the cryopump 10 . The heat source outside the cryopump 10 is, for example, a heat source installed in the vacuum chamber of the cryopump 10. It not only limits radiant heat, but also limits the entry of gas molecules. The plate member 32 occupies a part of the opening area of the intake port 12 to restrict the inflow of gas passing through the intake port 12 toward the internal space 14 to a desired amount. The plate member 32 covers most of the suction port 12. In the plate member 32 The condensed gas (for example, moisture) at the cooling temperature is captured to its surface.

There is a slight gap in the axial direction between the shield front end 28 and the plate member 32. In order to cover the gap and restrict the flow of gas, the plate member 32 is provided with a skirt portion 33. The skirt portion 33 is a short tube that curls the plate member 32. The skirt portion 33 together with the plate member 32 constitutes a circular tray-like integrated structure in which the plate member 32 has a bottom surface. The circular tray structure is configured to cover the radiation shield 30. Thereby, the skirt portion 33 projects downward from the plate member 32 in the axial direction and extends in the radial direction adjacent to the shield front end 28. The radial distance of the skirt 33 from the front end 28 of the shield is, for example, the degree of 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 an error can be reduced by the processing and assembly of precision components, but it is not necessarily realistic if one considers the resulting increase in manufacturing costs. The error relates to the individual difference of the cryopump 10. Assuming that there is no skirt 33, the amount of inflow of gas to the inside of the radiation shield 30 changes by the size of the gap. The inflow amount of the gas is directly related to the exhaust speed of the cryopump 10. Whether the gap is too large or too small will cause the actual exhaust speed to deviate from the design performance. The skirt 33 covers the gap between the shield front end 28 and the plate member 32, thereby restricting the flow of gas through the gap and reducing individual differences. As a result, it is also possible to reduce the individual difference in the cryopump exhaust speed with respect to the design performance.

The shield front end 28 and the plate member 32 are disposed above the suction port flange 40 of the cryopump housing 38 in the axial direction. The shield front end 28 and the plate member 32 are located outside of the cryopump housing 38. As such, the radiation shield 30 faces It extends to the vacuum chamber in which the cryopump 10 is mounted. By extending the radiation shield 30 upward, the main accommodating space 21 of the condensing layer 72 can be enlarged in the axial direction. However, the axial length of the extended portion is set to not interfere with the vacuum chamber (or the gate valve between the vacuum chamber and the cryopump 10).

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

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

Fig. 3 is a plan view schematically showing a plate member 32 according to an embodiment of the present invention. Representative constituent elements located below the plate member 32 are indicated by dashed lines in FIG. The plate member 32 is a flat plate (e.g., a circular plate) that traverses the shield opening 26. The front surface of the plate member 32 faces the outer space of the cryopump 10, and the back surface of the plate member 32 faces the top plate 60. The height of the main accommodation space 21 is determined by the axial distance of the plate member 32 from the top plate 60.

The size (e.g., diameter) of the plate member 32 is nearly equal to the size of the shield opening 26. The plate member 32 has a plate center portion 50 and a plate outer peripheral portion 52. The plate center portion 50 is a radially inner portion of the plate member 32, and the outer peripheral portion of the plate 52 is a radially outer portion of the plate member 32 that surrounds the plate center portion 50.

The outer peripheral portion 52 of the plate is attached to the plate mounting portion 29 of the front end 28 of the shield. The plate attachment portion 29 is a convex portion that protrudes radially inward from the shield distal end 28, and is formed at equal intervals in the circumferential direction (for example, every 90 degrees). The plate member 32 is fixed to the board mounting portion 29 by an appropriate method. For example, the plate attachment portion 29 and the plate outer peripheral portion 52 each have a bolt hole (not shown), and the plate outer peripheral portion 52 is fastened to the plate attachment portion 29 by bolts.

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

The small holes 54 are regularly arranged. In the present embodiment, the small holes 54 are provided at equal intervals in two orthogonal straight directions, and a lattice of the small holes 54 is formed. Alternatively, the small holes 54 may be provided at equal intervals in the radial direction and the circumferential direction, respectively.

The shape of the small hole 54 is, for example, a circular shape, but is not limited thereto. The small hole 54 may be an opening having another shape such as a rectangular shape, a slit extending in a straight line or a curved shape, or being formed on the outer periphery of the plate member 32. gap. The aperture 54 is significantly smaller in size than the shield opening 26.

The total area ratio of the small holes 54 to the opening area of the small holes 54 with respect to the intake port 12 (which may also be referred to as the opening ratio of the intake port 12) is 1% or more and 6% or less (4% or more and 6% or less). The preferred method is formed on the plate member 32. Thereby, the small hole 54 is guided by the air guide of the plate member 32 with respect to the suction port 12 The plate member 32 is formed in such a manner that the ratio of the open air conductance is 1% or more and 6% or less (4% or more and 6% or less is preferable).

It is also possible to carry out a surface treatment for improving the emissivity such as a black body treatment on the back surface of the plate member 32 and the inner surface of the radiation shield 30. Thereby, the radiance of the back surface of the plate member 32 and the inner surface of the radiation shield 30 is almost equal to one. It is also possible to apply the same surface treatment to the side of the plate member defining the small hole 54 in the plate member 32. The black surface of the plate member 32 may be formed, for example, by plating black chrome on the surface of the copper substrate, or may be formed by black coating. This black surface helps to absorb heat entering the cryopump 10.

On the one hand, it is also possible to carry out a surface treatment for reducing the emissivity on the front surface of the plate member 32 to reflect the radiant heat from the outside. Such a low emissivity surface can also be formed by, for example, nickel plating on the surface of a copper substrate.

The operation performed by the cryopump 10 having the above configuration will be described below. When the cryopump 10 is in operation, first, the inside of the vacuum chamber is roughly pumped to, for example, about 1 Pa by other appropriate rough pump before its operation. Thereafter, the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled by the driving of the refrigerator 16, and the first cryopanel 18 and the second cryopanel 20 thermally connected thereto are also cooled. Each of the first cryopanel 18 and the second cryopanel 20 is cooled to a first temperature and a second temperature lower than the first temperature.

The plate member 32 cools the gas molecules that have flown from the vacuum chamber toward the inside of the cryopump 10, and condenses and discharges a gas (for example, moisture or the like) whose vapor pressure is sufficiently lowered at the cooling temperature. The gas whose vapor pressure is not sufficiently lowered at the cooling temperature of the plate member 32 passes through the plurality of small holes 54 Enters the main accommodation 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 accommodating space 21.

Among the gas molecules that have entered, a gas (for example, argon or the like) whose vapor pressure is sufficiently lowered at the cooling temperature of the second cryopanel 20 is condensed and discharged on the surface of the second cryopanel 20 (mainly the top surface 61 of the top plate). Even a gas (for example, hydrogen or the like) whose vapor pressure is not sufficiently lowered at the cooling temperature is adsorbed and discharged by the adsorbent 68 adhered to the surface of the second cryopanel 20 which has been cooled. In this way, the cryopump 10 is capable of bringing the vacuum of the vacuum chamber to a desired degree of vacuum.

Fig. 4 is a view schematically showing the cryopump 10 during the exhaust operation. As shown in Fig. 4, ice or frost composed of condensed gas is deposited on the top plate 60 of the cryopump 10. As shown in Fig. 4, a dome-shaped or mushroom-type condensation layer 72 is grown on the top plate 60. The main component of the condensation layer 72 is, for example, argon. The ice layer grows with the exhaust gas running time, so that the thickness gradually increases. In addition, in the fourth drawing, the condensed layer deposited on the conventional plate 67 and the refrigerating machine cover 70 is omitted for the sake of simplicity.

As the condensation layer 72 grows, a temperature gradient is generated along the depth direction on the condensation layer 72. As a result, the surface temperature of the condensation layer 72 becomes higher than the surface temperature of the top plate 60. This means that at the beginning of the regeneration interval, the gas is directly condensed to the low-temperature top surface 61 of the top plate, whereas at the later stage of the regeneration interval, the gas condenses on the surface of the condensation layer 72 higher than the aforementioned temperature. Therefore, the exhaust speed of the cryopump 10 gradually decreases while the vacuum exhaust operation of the cryopump 10 is continued. The recovery time is also lengthened by the decrease in the exhaust speed.

Thus, the recovery time can also be used as an indicator for determining whether regeneration of the cryopump 10 is required. In this case, the cryopump 10 is allowed to continue to operate while the recovery time is shorter than the predetermined value. However, when the recovery time is longer than the predetermined value, the vacuum exhaust operation of the cryopump 10 is stopped, and regeneration of the cryopump 10 is performed. The specified value can also be determined as the specification of the vacuum process in the vacuum processing apparatus.

The regeneration of the cryopump 10 also becomes a downtime for the vacuum processing apparatus. Therefore, in order to increase the productivity of the vacuum processing apparatus, it is desirable to suppress an increase in the recovery time, thereby prolonging the regeneration interval of the cryopump 10.

When the recovery time is shortened, it is generally considered that the exhaust speed of the cryopump 10 can be increased. Therefore, as a method thereof, the ratio of the air conduction of the plate member 32 to the opening air conduction of the suction port 12 of the cryopump 10 is increased. In short, by increasing the aperture ratio of the intake port 12, the exhaust velocity of the cryopump 10 can be increased, and the recovery time can be shortened.

This is correct at the beginning of the regeneration interval. However, in the latter stage of the regeneration interval, it is not necessarily correct if the condensation layer 72 is grown. This is because if the aperture ratio is large, the heat load entering the cryopump 10 becomes high, and thus the temperature gradient of the condensation layer 72 is enlarged. Further, when the aperture ratio is large, the amount of gas that has entered the cryopump 10 also increases. This also has the effect of increasing the temperature gradient of the condensation layer 72. As described above, the expansion of the temperature gradient in the condensing layer 72 will bring about an increase in the surface temperature of the condensing layer 72 and an increase in the recovery time. In the latter stage of the regeneration interval, as shown in Fig. 4, since the condensation layer 72 is largely grown, there is a possibility that the recovery time is remarkably increased.

Therefore, in the present embodiment, the object is to suppress the condensation layer The expansion of the temperature gradient of 72 inhibits the increase in recovery time. The exhaust gas velocity of the cryopump 10 is reduced by the growth of the condensation layer 72 by reducing the temperature difference between the condensation layer 72 and the top plate 60. Therefore, in the present embodiment, the air conduction ratio is finally set to a small value from the viewpoint of practicality. For example, as described above, the ratio of the air conduction of the plate member 32 to the opening air conduction of the intake port 12 is set to be 1% or more and 6% or less (for example, 4% or more and 6% or less).

Further, if the dome-shaped condensing layer 72 is further grown in the radial direction, there is a possibility that the outer peripheral portion of the condensing layer 72 comes into contact with the shield side portion 36. Assuming that the gap between the mount 37 and the top plate 60 is narrow, the condensation layer 72 first comes into contact with the mount 37. The gas is vaporized again at the contact portion, and is released to the outside of the main accommodating space 21 and the cryopump 10. Thereby, the cryopump 10 thereafter cannot provide design exhaust performance. Therefore, the amount of gas occlusion at this time is given to the maximum occlusion amount of the cryopump 10. Part of the condensing layer 72 (at this time, the condensing layer 72 near the mount 37) determines the gas occlusion limit of the cryopump 10.

Cryopumps are generally designed to be axisymmetric. However, since the refrigerator 16 is laterally disposed in the horizontal cryopump 10, it is inevitably provided with an asymmetrical portion (for example, the mount 37). In the present embodiment, the shape of the top plate 60 is made to coincide with such an asymmetrical portion, and the width of the gap between the top plate 60 and the radiation shield 30 is aligned in the circumferential direction. It is possible to avoid that only a specific portion of the top plate 60 that has the radially growing condensation layer 72 (in this case, the condensation layer 72 near the mount 37) comes into contact with the radiation shield 30 first. As a result, according to the embodiment, the gas occlusion of the cryopump 10 can be improved. the amount.

Fig. 5 is a view showing an embodiment of the present invention, and exemplifies a change in recovery time in a regeneration interval. The vertical axis of Fig. 5 indicates the recovery time, and the horizontal axis indicates the operation time of the cryopump 10. The horizontal axis of Fig. 5 can also be referred to as the cumulative number of times the recovery is performed during the vacuum exhaust operation of the cryopump 10. In Fig. 5, the change in the recovery time of this embodiment is indicated by a solid line, and the change of the recovery time of the comparative example is indicated by a broken line. The comparative example is a case where the opening ratio of the suction port of the cryopump is relatively high (for example, more than 7%). The reproduction interval of this embodiment is indicated by an arrow B, and the reproduction interval of the comparative example is indicated by an arrow C.

Fig. 6 is a plan view schematically showing a plate member 132 of a comparative example. As shown in Fig. 6, the plate member 132 has a plurality of small holes 154 formed not only on the plate center portion 150 but also on 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 suction port exceeds 7%.

As shown in Fig. 5, in the cryopump 10 of the present embodiment, the recovery time at the initial stage of the regeneration interval is slightly longer than that of the comparative example. When the vacuum exhaust operation of the cryopump 10 continues, the exhaust velocity of the cryopump 10 gradually decreases as the regeneration interval approaches, and at the same time, the recovery time becomes longer. Thereby, when the recovery time reaches the predetermined value T, the regeneration interval is ended (that is, the regeneration is started).

According to this embodiment, the opening ratio of the inlet cryopanel is small with respect to the opening of the intake port 12. The opening ratio of the inlet cryopanel is the area of the opening portion of the inlet cryopanel relative to the inlet cryopanel area when viewed from the axial direction. ratio. Since the opening ratio of the inlet cryopanel is small, the flow rate of gas from the outside of the cryopump 10 to the main accommodating space 21 is also small. Thereby, the growth rate of the condensation layer 72 is small. Also, the heat load generated by the gas is also small. In addition, the heat load generated by the incoming radiant heat is also small. Thereby, the temperature gradient in the condensation layer 72 becomes small, and the surface temperature of the condensation layer 72 is maintained at a low temperature. Thereby, it is possible to suppress an increase in the recovery time in the later stage of the regeneration interval. Thereby, the regeneration interval B in the present embodiment is extended as compared with the regeneration interval C in the comparative example.

According to the investigation and estimation by the present inventors, when the diameter of the intake port is in the range of 180 mm to 340 mm, the effect of prolonging the regeneration interval caused by the decrease in the aperture ratio can be obtained. Further, according to the investigation and estimation by the inventors of the present invention, the present embodiment is effective, for example, for vacuum evacuation in the range of 1 mTorr to 10 mTorr.

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 to extend the regeneration interval of the cryopump 10 in accordance with a new knowledge different from the conventional knowledge. Thereby, the cryopump 10 which contributes to the productivity improvement of a vacuum processing apparatus can be provided.

Hereinabove, the present invention has been described by way of examples. The present invention is not limited to the above-described embodiments, and various modifications can be made. It will be understood by those skilled in the art that various modifications can be made, and such modifications are also within the scope of the present invention.

Fig. 7 is a plan view schematically showing a plate member 232 of a first cryopanel according to another embodiment of the present invention. The plate member 232 is provided with: a first plate 234, having an opening through which at least gas passes; and a second plate 236 adjacent to the first plate 234 and cooperating with the first plate 234 to cover the opening of the shield. 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 diameter of the cryopump suction port and the opening of the shield. The first plate 234 has a plurality 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 substantially equal to the diameter of the intake port and the opening of the shield. The second plate 236 represents at least 15% of the cryopump suction port.

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

Claims (8)

A cryopump characterized by comprising: a cryopump container, wherein a cryopump intake port is defined by a tip end; and the refrigerator includes a first cooling stage and a second cooling stage housed in the cryopump housing, and the second cooling The stage is cooled to a temperature lower than the first cooling stage; the first cryopanel is thermally connected to the first cooling stage and surrounded by the cryopump container; and the second cryopanel is thermally connected to the second cooling stage. The first cryopanel is provided with an inlet cryopanel having an inlet opening at the inlet of the cryopump, and the inlet opening is formed by the air conduction of the inlet cryopanel relative to the low temperature The inlet air-cooling plate is formed in the inlet cryopanel in such a manner that the ratio of the open air conduction of the pump suction port is 4% or more and 6% or less. The cryopump according to claim 1, wherein the inlet cryopanel includes a perforated member disposed at the cryopump intake port, and the inlet opening portion is formed in at least one opening of the perforated member The area ratio of the at least one opening to the suction port of the cryopump is 4% or more and 6% or less. The cryopump according to claim 2, wherein the perforated member is a single perforated plate covering the suction port of the cryopump. The cryopump according to claim 2, wherein the cryopump intake port is a circular opening having a first diameter, and the perforated member includes a circle having a second diameter smaller than the first diameter. And a shaped plate, and an annular plate covering the suction port of the cryopump together with the circular plate, wherein the at least one opening is formed in the circular plate. The cryopump according to claim 2, wherein the at least one opening is a plurality of holes. The cryopump according to claim 1 or 2, wherein the aforementioned cryopump suction port has a diameter in the range of 180 mm to 340 mm. The cryopump according to claim 1 or 2, wherein the side surface of the inlet cryopanel that defines the inlet opening portion is black. The cryopump according to claim 1 or 2, wherein the inlet cryopanel is disposed above the front end of the cryopump container that determines the intake port of the cryopump.