Cryopump

Abstract

A cryopump (10) comprising: a cryopump container (16) having a container body (16a) that defines a cryopump inlet (17) and a refrigerating machine receiving barrel (16b) connected to a side portion of the container body (16a); a refrigerating machine (14) fixed to the refrigerating machine receiving barrel (16b) and having a first cooling stage (30) and a second cooling stage (34) that is cooled to a temperature lower than that of the first cooling stage (30); a plurality of cryopanels (38) which are thermally coupled to the second cooling stage (34), each of which is capable of adsorbing a non-condensable gas, and which are arrayed in a direction from the cryopump inlet (17) toward the bottom portion of the container body (16a) or radially arranged when viewed from the cryopump inlet (17); and a purge gas introduction portion (20) mounted to the container body (16a) at a position lower than the refrigerating machine receiving barrel (16b) so that a purge gas is to be blown to the distal portions of the cryopanels (38) distant from the second cooling stage (34).

Description

Technical Field

[0001] The present invention relates to a cryopump.

Background Art

[0002] A cryopump is a vacuum pump that captures gas molecules by condensation or adsorption on a cryopanel cooled to an extremely low temperature and exhausts them. Cryopumps are generally used to achieve a clean vacuum environment required in semiconductor circuit manufacturing processes and the like. Since a cryopump is a so-called gas storage type vacuum pump, it requires regeneration to periodically discharge the captured gas to the outside.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One exemplary object of an aspect of the present invention is to shorten the regeneration time of a cryopump.

Means for Solving the Problems

[0005] According to one aspect of the present invention, the cryopump comprises a cryopump container having a container body that defines a cryopump intake port and extends axially in a cylindrical shape from the cryopump intake port, and a refrigerator housing cylinder connected to the side of the container body; a refrigerator fixed to the refrigerator housing cylinder and extending in a direction perpendicular to the axial direction within the cryopump container, having a first cooling stage and a second cooling stage that is cooled to a lower temperature than the first cooling stage; a plurality of cryopanels thermally coupled to the second cooling stage, each capable of adsorbing non-condensable gases, arranged axially between the cryopump intake port and the bottom of the container body, or arranged radially when viewed from the cryopump intake port; and a purge gas introduction section installed in the container body below the refrigerator housing cylinder to blow purge gas onto the distal portions of the cryopanels away from the second cooling stage.

[0006] Furthermore, any combination of the above components, or any substitution of components or expressions of the present invention between methods, apparatus, systems, etc., is also valid as an embodiment of the present invention. [Effects of the Invention]

[0007] According to the present invention, the regeneration time of the cryopump can be shortened. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing a cryopump according to an embodiment. [Figure 2] This diagram schematically shows a cryopump related to a comparative example. [Figure 3] This diagram schematically shows a cryopump according to Modification Example 1. [Figure 4] Figures 4(a) and 4(b) schematically show a cryopump according to Modification 2. [Figure 5] Figures 5(a) to 5(c) schematically show examples of purge gas diffusion members applicable to a cryopump according to the embodiment. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0010] Figure 1 is a schematic diagram showing a cryopump 10 according to an embodiment. The cryopump 10 is used to raise the vacuum level inside the vacuum chamber to the level required for a desired vacuum process, for example, by being installed in the vacuum chamber of an ion implantation apparatus, sputtering apparatus, deposition apparatus, or other vacuum process apparatus. -5 Pa~10 -8 A high level of vacuum, around Pa, is achieved in the vacuum chamber.

[0011] The cryopump 10 comprises a compressor 12, a refrigerator 14, and a cryopump container 16 having a cryopump air intake 17. The cryopump 10 also includes a rough valve 18, a purge valve 20a, and a vent valve 22, which are installed in the cryopump container 16. The cryopump 10 comprises a radiation shield 36 and a plurality of cryopanels 38 housed in the cryopump container 16. The purge valve 20a, together with an opening 20b provided in the radiation shield 36, constitutes a purge gas introduction section 20.

[0012] The compressor 12 is configured to recover refrigerant gas from the chiller 14, pressurize the recovered refrigerant gas, and supply it back to the chiller 14. The chiller 14, also called the expander or cold head, together with the compressor 12 constitutes a cryogenic chiller. The circulation of refrigerant gas between the compressor 12 and the chiller 14 occurs with a combination of appropriate pressure and volume fluctuations of the refrigerant gas within the chiller 14, thereby creating a thermodynamic cycle that generates cold, and the chiller 14 can provide cryogenic cooling. The refrigerant gas is usually helium, but other suitable gases may be used. For understanding, the direction of refrigerant gas flow is indicated by arrows in Figure 1. The cryogenic chiller is, as an example, a two-stage Gifford-McMahon (GM) chiller, but may be a pulse tube chiller, a Stirling chiller, or other type of cryogenic chiller.

[0013] The refrigerator 14 comprises a room temperature section 26, a first cylinder 28, a first cooling stage 30, a second cylinder 32, and a second cooling stage 34. The refrigerator 14 is configured to cool the first cooling stage 30 to a first cooling temperature and the second cooling stage 34 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling stage 30 is cooled to about 65K to 120K, preferably 80K to 100K, and the second cooling stage 34 is cooled to about 10K to 20K. The first cooling stage 30 and the second cooling stage 34 may also be referred to as a high-temperature cooling stage and a low-temperature cooling stage, respectively.

[0014] The first cylinder 28 connects the first cooling stage 30 to the room temperature section 26, thereby structurally supporting the first cooling stage 30 in the room temperature section 26. The second cylinder 32 connects the second cooling stage 34 to the first cooling stage 30, thereby structurally supporting the second cooling stage 34 in the first cooling stage 30. The first cylinder 28 and the second cylinder 32 extend coaxially, and the room temperature section 26, the first cylinder 28, the first cooling stage 30, the second cylinder 32, and the second cooling stage 34 are arranged in a straight line in this order.

[0015] In the case of a two-stage GM refrigerator 14, a first displacer and a second displacer (not shown) are reciprocally mounted inside the first cylinder 28 and the second cylinder 32, respectively. The first displacer and the second displacer each incorporate a first regenerator and a second regenerator (not shown). The room temperature section 26 also has a drive mechanism (not shown), such as a motor, for reciprocating the first and second displacers. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas (e.g., helium) to periodically supply and discharge the working gas into and out of the refrigerator 14.

[0016] The cryopump vessel 16 has a vessel body 16a and a refrigerator housing cylinder 16b. The cryopump vessel 16 is a vacuum vessel designed to maintain a vacuum during the vacuum evacuation operation of the cryopump 10 and to withstand the pressure of the surrounding environment (e.g., atmospheric pressure). The vessel body 16a defines the cryopump intake port 17 and extends cylindrically from the cryopump intake port 17 in the axial direction (along the cryopump central axis C shown in Figure 1). The vessel body 16a has a cylindrical shape with the cryopump intake port 17 at one axial end and the other axial end closed. The vessel body 16a houses a radiation shield 36, and the cryopanel 38 is housed inside the radiation shield 36 together with the second cooling stage 34. The refrigerator housing cylinder 16b is connected at one end to the vessel body 16a and fixed at the other end to the room temperature section 26 of the refrigerator 14. The refrigerator 14 is inserted into the refrigerator housing cylinder 16b, and the first cylinder 28 is housed within it.

[0017] In this embodiment, the cryopump 10 is a so-called horizontal cryopump in which the refrigerator 14 is provided on the side of the container body 16a. The refrigerator 14 is fixed to the refrigerator housing cylinder 16b and extends in a direction perpendicular to the axial direction within the cryopump container 16. A refrigerator insertion port is provided on the side of the container body 16a, and the refrigerator housing cylinder 16b is coupled to the side of the container body 16a at this refrigerator insertion port. Similarly, adjacent to the refrigerator insertion port of the container body 16a, a hole for passing the refrigerator 14 is also provided in the side of the radiation shield 36. Through these holes, the second cylinder 32 and the second cooling stage 34 of the refrigerator 14 are inserted into the radiation shield 36, and the radiation shield 36 is thermally coupled to the first cooling stage 30 around the holes on its side.

[0018] The cryopump can be installed in various orientations at the site where it is used. As an example, the cryopump 10 can be installed in the illustrated horizontal orientation, that is, with the cryopump intake port 17 facing upward. At this time, the bottom of the container body 16a is located below the cryopump intake port 17, and the refrigerator 14 extends horizontally.

[0019] The roughing valve 18 is installed in the cryopump container 16, for example, in the refrigerator housing cylinder 16b. The roughing valve 18 is connected to a roughing pump (not shown) installed outside the cryopump 10. The roughing pump is a vacuum pump for evacuating the cryopump 10 to its operating starting pressure. When the roughing valve 18 is opened, the cryopump container 16 is communicated with the roughing pump, and when the roughing valve 18 is closed, the cryopump container 16 is blocked from the roughing pump. By opening the roughing valve 18 and operating the roughing pump, the cryopump 10 can be depressurized.

[0020] The purge valve 20a is installed in the cryopump container 16. In this embodiment, it is installed in the container body 16a below the refrigerator housing cylinder 16b. The purge valve 20a is connected to a purge gas source 21 installed outside the cryopump 10. The radiation shield 36 is provided with an opening 20b through which the purge gas ejected from the purge valve 20a into the cryopump container 16 passes into the radiation shield 36. The opening 20b is provided in the front of the purge valve 20a. When the purge valve 20a is opened, the purge gas is supplied from the purge valve 20a into the radiation shield 36 through the opening 20b, and when the purge valve 20a is closed, the supply of the purge gas to the cryopump container 16 is blocked.

[0021] The purge gas may be, for example, nitrogen gas or other dry gas. The temperature of the purge gas may be adjusted to room temperature, for example, or heated to a temperature higher than room temperature. By opening the purge valve 20a and introducing the purge gas into the cryopump container 16, the pressure inside the cryopump 10 can be increased from vacuum to atmospheric pressure or a pressure higher than that. Also, the cryopump 10 can be heated from an extremely low temperature to room temperature or a temperature higher than that.

[0022] In this embodiment, it is provided on the side of the container body 16a on the same side as the refrigerator housing cylinder 16b when viewed from the cryopump intake port 17. By providing the purge gas introduction part 20 on the same side as the refrigerator housing cylinder 16b like other valves such as the roughing valve 18, the accompanying piping and electrical wiring can be arranged together, facilitating the handling of these piping and wiring.

[0023] The vent valve 22 is installed in the cryopump vessel 16, for example, in the chiller housing cylinder 16b. The vent valve 22 is provided to discharge fluid from the inside of the cryopump 10 to the outside. The vent valve 22 may be connected to an external storage tank (not shown) that receives the discharged fluid. Alternatively, if the discharged fluid is harmless, the vent valve 22 may be configured to release the discharged fluid into the surrounding environment. The fluid discharged from the vent valve 22 is basically a gas, but may be a liquid or a mixture of gas and liquid.

[0024] The vent valve 22 may be, for example, a normally closed control valve, which may be opened when fluid is released from the cryopump container 16, such as during regeneration, and closed when fluid should not be released. The vent valve 22 may also be configured to function as a so-called safety valve that is mechanically opened when a predetermined differential pressure is applied. If the inside of the cryopump becomes high pressure for any reason, the vent valve 22 can be mechanically opened, thereby releasing the high pressure inside.

[0025] The radiant shield 36 is thermally coupled to the first cooling stage 30 and cooled to a first cooling temperature to provide a cryogenic surface for protecting the cryopanels 38 from radiant heat from outside the cryopump 10 or from the cryopump vessel 16. The radiant shield 36 is positioned around the multiple cryopanels 38 within the vessel body 16a. The radiant shield 36 has a cylindrical shape, for example, that surrounds the cryopanels 38 and the second cooling stage 34. The end of the radiant shield 36 on the cryopump intake 17 side is open, allowing gas entering from outside the cryopump 10 through the cryopump intake 17 to be received into the radiant shield 36. The end of the radiant shield 36 opposite the cryopump intake 17 is closed. Alternatively, the end of the radiant shield 36 opposite the cryopump intake 17 may have an opening or be open. The radiant shield 36 has a gap between it and the cryopanels 38, and the radiant shield 36 is not in contact with the cryopanels 38. The radiation shield 36 is not in contact with the cryopump container 16.

[0026] An inlet cryo-panel 37 may be provided at the cryopump intake port 17, fixed to the open end of the radiation shield 36. The inlet cryo-panel 37 is cooled to the same temperature as the radiation shield 36, and so-called type 1 gases (gases that condense at relatively high temperatures, such as water vapor) can be condensed on its surface. The inlet cryo-panel 37 may be, for example, a louver or baffle, but it may also be a plate or member of, for example, a circular or other shape, arranged to occupy a portion of the cryopump intake port 17.

[0027] The cryopanel 38 is thermally coupled to the second cooling stage 34 and cooled to a second cooling temperature in order to provide a cryogenic surface for condensing type 2 gases (e.g., gases that condense at relatively low temperatures, such as argon and nitrogen). Furthermore, at least a portion of the surface of the cryopanel 38 is covered with, for example, activated carbon or other adsorbent material for adsorbing type 3 gases (e.g., non-condensable gases, such as hydrogen). These adsorption regions may be formed in locations not visible from the cryopump inlet 17 (e.g., on the surface of the cryopanel 38 opposite the cryopump inlet 17, or in the shadow of an adjacent cryopanel 38 above). The adsorption regions of each cryopanel 38 may be formed on all or most of the surface of that cryopanel 38 that is not visible from the cryopump inlet 17. Multiple cryopanels 38 can also be referred to as adsorption cryopanels, as each is capable of adsorbing non-condensable gases. Gas entering the radiation shield 36 from outside the cryopump 10 through the cryopump intake port 17 is captured by condensation or adsorption on the cryopanel 38.

[0028] The radiant shield 36 and the inlet cryopanel 37, which are cooled to a first cooling temperature, may be collectively referred to as a high-temperature cryopanel. The cryopanel 38 is cooled to a second cooling temperature lower than the first cooling temperature, and can therefore also be called a low-temperature cryopanel.

[0029] Each component cooled to extremely low temperatures, such as the radiation shield 36, the inlet cryopanel 37, and the cryopanel 38, is formed from, for example, a metallic material such as copper or aluminum, or another material with high thermal conductivity. Each component may comprise a body made of such a high thermal conductivity material and a covering layer (e.g., a nickel layer) covering the body.

[0030] Multiple cryopanels 38 are arranged axially between the cryopump intake port 17 and the bottom of the container body 16a. For convenience of explanation, cryopanels 38 located above the second cooling stage 34 will be referred to as upper cryopanels 38a, and cryopanels 38 located below the upper cryopanels 38a will be referred to as lower cryopanels 38b.

[0031] The upper cryopanels 38a have an inverted frustoconical shape, with each center located on the cryopump central axis C. The circular center of the upper cryopanel 38a is positioned perpendicular to the axial direction, and the outer periphery is inclined with respect to a plane perpendicular to the axial direction. The outer periphery of the upper cryopanel 38a extends diagonally upward radially outward from the center. Two axially adjacent upper cryopanels 38a have a gap between their outer peripheries, allowing gas entering from the cryopump intake port 17 to be received into this gap. As shown in Figure 1, some of the upper cryopanels 38a, for example, at least one upper cryopanel 38a adjacent to the cryopump intake port 17, may be flat (e.g., circular) instead of inverted frustoconical.

[0032] The diameter of the multiple upper cryo panels 38a increases as they move away from the cryopump intake port 17. The upper cryo panel 38a closest to the cryopump intake port 17 (hereinafter referred to as the top cryo panel 38a1 for convenience) has the smallest diameter. The top cryo panel 38a1 is located directly below the inlet cryo panel 37 and is the upper cryo panel 38a furthest axially from the second cooling stage 34. The diameter of the upper cryo panels 38a increases as they move closer to the second cooling stage 34 from the top cryo panel 38a1.

[0033] Furthermore, the depth (axial distance from the center to the outer periphery) of the multiple upper cryo panels 38a may increase as they move away from the cryopump intake port 17. The upper cryo panels 38a may be arranged in a nested manner, such as some of the upper cryo panels 38a that are closer to the second cooling stage 34. That is, the lower part of an upper cryo panel 38a located higher up may extend into an adjacent upper cryo panel 38a below it. The inclination angle of the outer periphery of an upper cryo panel 38a may be greater for upper cryo panels 38a located lower down, as shown in the figure. This inclination angle may be the same for several (or all) adjacent upper cryo panels 38a.

[0034] Multiple heat transfer elements 40 are provided to attach multiple upper cryo panels 38a to the second cooling stage 34. The heat transfer elements 40 have a short cylindrical or disc shape, and their diameter is equal to the center of the upper cryo panel 38a. The upper cryo panels 38a and heat transfer elements 40 are arranged alternately on the cryopump central axis C, thereby forming a cylindrical portion extending along the cryopump central axis C with the center of the upper cryo panel 38a and the heat transfer elements 40. Axial bolt holes are provided that penetrate this cylindrical portion to the second cooling stage 34, and long bolts are inserted into the bolt holes to fasten them to the second cooling stage 34. In this way, the upper cryo panels 38a and heat transfer elements 40 are fixed to the second cooling stage 34 and thermally bonded to the second cooling stage 34. Note that the upper cryo panels 38a and heat transfer elements 40 may be joined by other methods, such as adhesive or welding.

[0035] Multiple lower cryopanels 38b are arranged axially between the second cooling stage 34 and the bottom of the container body 16a. Similar to the upper cryopanels 38a, the lower cryopanels 38b have an inverted frustoconical shape, with each center located on the cryopump central axis C. The lower cryopanels 38b have an outer periphery inclined with respect to a plane perpendicular to the axial direction. The outer periphery of the lower cryopanels 38b extends diagonally upward radially outward from the center. Two axially adjacent lower cryopanels 38b have a gap between their outer peripheries, allowing gas entering from the cryopump intake port 17 to be received into this gap.

[0036] The lower cryopanel 38b has a larger diameter and depth than the upper cryopanel 38a, and its diameter and depth increase as it moves away from the cryopump intake port 17. Therefore, the lower cryopanel 38b furthest from the second cooling stage 34 (hereinafter referred to as the bottom cryopanel 38b1 for convenience) has the largest diameter and depth among the cryopanels 38. The lower cryopanels 38b may be arranged in a nested manner, similar to the upper cryopanel 38a. The inclination angle of the outer periphery of the lower cryopanel 38b may be greater for lower cryopanels 38b located lower down, as shown in the figure. This inclination angle may be the same for several (or all) adjacent lower cryopanels 38b.

[0037] A cryo-panel mounting member 42 is provided for attaching the lower cryo-panel 38b to the second cooling stage 34. The cryo-panel mounting member 42 is fixed to the second cooling stage 34 and extends axially downward from the second cooling stage 34. Multiple lower cryo-panels 38b are spaced apart from each other in the axial direction and attached to the cryo-panel mounting member 42 at their respective centers. Each lower cryo-panel 38b has a notch formed from its outer periphery to its center to receive the second cooling stage 34 and the cryo-panel mounting member 42 in its center. In this way, the lower cryo-panel 38b is thermally coupled to the second cooling stage 34 via the cryo-panel mounting member 42.

[0038] The cryopanels 38 are arranged relatively closely together to increase the exhaust velocity and storage capacity of the gas (e.g., a non-condensable gas). At least three, or at least four, or at least five upper cryopanels 38a may be arranged axially between the inlet cryopanel 37 and the upper surface of the second cooling stage 34. The top cryopanel 38a1 may be positioned close to the inlet cryopanel 37, and the axial distance from the top cryopanel 38a1 to the inlet cryopanel 37 may be less than, or less than half of, the axial distance from the top cryopanel 38a1 to the upper surface of the second cooling stage 34. Alternatively, the axial distance from the top cryopanel 38a1 to the inlet cryopanel 37 may be less than the axial distance from the top cryopanel 38a1 to the adjacent upper cryopanel 38a directly below it.

[0039] Furthermore, at least three, or at least five, or at least ten lower cryo panels 38b may be arranged axially between the bottom of the radiation shield 36 and the top surface of the second cooling stage 34. The bottom cryo panel 38b1 may be positioned close to the bottom of the radiation shield 36, and the axial distance from the bottom cryo panel 38b1 to the bottom of the radiation shield 36 may be less than, or less than half of, or less than one-third of, the axial distance from the bottom cryo panel 38b1 to the top surface of the second cooling stage 34. Alternatively, the axial distance from the bottom cryo panel 38b1 to the bottom of the radiation shield 36 may be less than the axial distance from the bottom cryo panel 38b1 to the adjacent lower cryo panel 38b directly above it.

[0040] The bottom cryo panel 38b1 is relatively large among the cryo panels 38, and may be the largest. The bottom cryo panel 38b1 may be larger than the top cryo panel 38a1, and the area of ​​the bottom cryo panel 38b1 may be about 1.5 to about 5 times the area of ​​the top cryo panel 38a1. The diameter of the bottom cryo panel 38b1 may be at least 70%, or at least 80%, or at least 90% of the diameter of the cryopump intake port 17.

[0041] The lower cryo panel 38b is allocated more space than the upper cryo panel 38a. When the axial distance La from the top cryo panel 38a1 to the upper surface of the second cooling stage 34 is 1, the axial distance Lb from the bottom cryo panel 38b1 to the upper surface of the second cooling stage 34 may be in the range of 1 to 3, or in the range of 1 to 2. That is, La ≤ Lb ≤ 3La (or 2La). The cryopump 10 can accommodate more lower cryo panels 38b than the upper cryo panel 38a.

[0042] The multiple cryopanels 38 are not limited to the specific arrangement and shape described above with reference to Figure 1, but can take on various forms. For example, the shape of the cryopanel 38 is not limited to an inverted frustoconical shape, but may be other shapes that are convex downwards, or flat plates, or other shapes. Other exemplary forms of cryopanels 38 will be described later with reference to Figures 3 and 4.

[0043] The cryopump 10 is suitable for applications requiring high-speed exhaust of non-condensable gases such as hydrogen gas (e.g., ion implantation equipment). The cryopump 10 shown in Figure 1 is designed to have a hydrogen capture probability of at least 20%, at least 25%, or at least 30%. Similarly, the cryopumps 10 shown in Figures 3 and 4 are also designed to have a hydrogen capture probability of at least 20%, at least 25%, or at least 30%.

[0044] The hydrogen capture probability is given by the ratio of the actual hydrogen pumping velocity to the theoretical maximum hydrogen pumping velocity in a cryopump having the same bore diameter as cryopump 10 (i.e., the same cryopump opening area). The actual hydrogen pumping velocity of a cryopump can be determined by known Monte Carlo simulations. The theoretical hydrogen pumping velocity can be considered equal to the molecular flow conductance for its opening. The hydrogen conductance C(hydrogen) can be obtained from the conductance C(air at 20°C) of air at 20°C using the following equation.

[0045] TIFF0007837946000001.tif28170

[0046] Here, T is the temperature of hydrogen gas (K), and M is the molecular weight of hydrogen (i.e., M=2). The conductance C of air at 20°C (air at 20°C) is given by the opening area A (m²). 2 It is proportional to ) and given by C(20°C air) = 116A. For example, in the case of a cryopump with a diameter of 250 mm, the theoretical hydrogen pumping velocity is approximately 20840 L / s according to the above formula. In this case, a hydrogen capture probability of 30% is equivalent to a hydrogen pumping velocity of approximately 6252 L / s for that cryopump.

[0047] Furthermore, cryopanels without adsorbent material on their surface may be provided, and these may be referred to as condensing cryopanels. In other words, condensing cryopanels cannot adsorb non-condensable gases, but can capture type 2 gases by condensation. For example, the upper cryopanel 38a closest to the cryopump intake port 17 (e.g., top cryopanel 38a1) may be a condensing cryopanel.

[0048] In this embodiment, the purge gas inlet 20 is installed in the container body 16a below the refrigerator housing cylinder 16b so as to blow purge gas onto the distal part of the cryopanel 38 away from the second cooling stage 34. In this embodiment, the purge valve 20a and opening 20b are installed on the side of the container body 16a at an axial height aligned with the bottom cryopanel 38b1. The axial height of the purge valve 20a and opening 20b is determined so as to blow the purge gas flow onto the outer circumference of the bottom cryopanel 38b1. For example, the purge valve 20a and opening 20b are at the same axial height as the outer circumference of the bottom cryopanel 38b1. For understanding, Figure 1 schematically shows the purge gas flow blown from the purge gas inlet 20 onto the bottom cryopanel 38b1 with arrows.

[0049] The operation of the cryopump 10 with the above configuration is described below. Before operating the cryopump 10, the inside of the vacuum chamber is first roughly vacuumed to about 1 Pa using another suitable rough pump. Then, the cryopump 10 is operated. The refrigerator 14 drives the first cooling stage 30 and the second cooling stage 34 to the first cooling temperature and the second cooling temperature, respectively. As a result, the radiant shield 36 and the inlet cryo panel 37, which are thermally coupled to the first cooling stage 30, are also cooled to the first cooling temperature. The cryo panel 38, which is thermally coupled to the second cooling stage 34, is cooled to the second cooling temperature.

[0050] The inlet cryopreaker 37 cools the gas flying from the vacuum chamber toward the cryopreaker 10. Type 1 gases, such as water vapor, condense on the surfaces of the radiation shield 36 and the inlet cryopreaker 37. Type 2 gases, such as argon, and Type 3 gases, such as hydrogen, do not have sufficiently low vapor pressure at the first cooling temperature, so they enter the internal space of the cryopreaker 10 through the cryopreaker intake 17. Type 2 gases that enter the cryopreaker 38 are cooled and condensed by the cryopreaker 38. Type 3 gases are adsorbed in the adsorption region of the cryopreaker 38. In this way, the cryopreaker 10 can exhaust various gases by condensation or adsorption, and the vacuum level of the vacuum chamber can be brought to the desired level.

[0051] As the vacuum evacuation operation of the cryopump 10 continues, gas accumulates in the cryopump 10. To discharge the accumulated gas to the outside, the cryopump 10 is regenerated. The regeneration of the cryopump 10 generally includes a heating process, a discharge process, and a cool-down process.

[0052] The heating process includes heating the cryopanel 38 to a regeneration temperature (e.g., room temperature or higher). The heat source for heating is, for example, the refrigerator 14. The refrigerator 14 enables heating operation (so-called reverse heating). That is, the refrigerator 14 is configured such that adiabatic compression occurs in the working gas when the drive mechanism provided in the room temperature section 26 operates in the opposite direction to the cooling operation. The heat of compression thus obtained allows the refrigerator 14 to heat the first cooling stage 30 and the second cooling stage 34. The radiant shield 36 and the cryopanel 38 are heated using the first cooling stage 30 and the second cooling stage 34 as heat sources, respectively. In addition, the purge gas supplied into the cryopump vessel 16 from the purge valve 20a also contributes to heating the cryopump 10. Alternatively, the cryopump 10 may be provided with a heating device such as an electric heater. For example, an electric heater that can be controlled independently of the operation of the refrigerator 14 may be installed in the first cooling stage 30 and / or the second cooling stage 34 of the refrigerator 14.

[0053] In the discharge process, the gas captured by the cryopump 10 is re-vaporized or liquefied and discharged as gas, liquid, or a mixture of gas and liquid together with the purge gas through the vent valve 22 or rough valve 18. In the cool-down process, the cryopump 10 is re-cooled to an extremely low temperature for vacuum evacuation operation. Once regeneration is complete, the cryopump 10 can start evacuation operation again.

[0054] Figure 2 is a schematic diagram of a cryopump relating to a comparative example. As shown in Figure 2, in existing cryopumps, a large space 150 is often secured between the cryopump intake port 117 (inlet cryopanel 137) and the top cryopanel 138. The top cryopanel 138 is directly attached to the second cooling stage 134 of the refrigerator, or is located very close to the second cooling stage 134. By utilizing this large space 150 to capture type 2 gases such as argon on the top cryopanel 138 by condensation, a large amount of type 2 gas can be stored in the cryopump. Since the purge valve 120 is typically installed near the cryopump intake port 117, the large amount of type 2 gas condensed on the top cryopanel 138 can be efficiently vaporized and discharged by introducing purge gas from the purge valve 120 during regeneration. Such a design is often seen, for example, in cryopumps for physical deposition (PVD) systems.

[0055] In contrast, the cryopump 10 according to this embodiment does not occupy a large volume space close to the cryopump intake port 17, but rather has a large number of cryopanels 38 densely arranged. Since each cryopanel 38 is capable of adsorbing non-condensable gases, the cryopump 10 can exhaust non-condensable gases at high speed. The cryopump 10 is suitable, for example, for vacuum evacuation of an ion implantation apparatus.

[0056] Since a large number of cryopanels 38 are arranged, the total weight of the cryopanels 38, and therefore their heat capacity, becomes relatively large. When reverse heating of the refrigerator 14 is used during regeneration, the second cooling stage 34 becomes the heat source for the cryopanels 38. The distal part of the cryopanel 38 that is far from the second cooling stage 34 (for example, the outer periphery of the cryopanel 38) is relatively difficult to heat up because the heat transfer path from the second cooling stage 34 is longer. The lower cryopanel 38b, in particular the bottom cryopanel 38b1, is relatively large, so its weight and heat capacity are greater than the other cryopanels 38, and it is also far from the second cooling stage 34, so its heat transfer path is also longer. If the purge gas is introduced from near the cryopump intake port 17, which is far from the bottom cryopanel 38b1, as in existing cryopumps, the effect of the purge gas on promoting the heating of the bottom cryopanel 38b1 may be insufficient. The time required to raise the entire cryopanel 38 to a predetermined regeneration temperature is determined by the heating time of the distal part of the lower cryopanel 38b that is far from the second cooling stage 34 (for example, the outer periphery of the bottom cryopanel 38b1). If this heating time is extended, it may lead to an increase in regeneration time, which is undesirable.

[0057] According to this embodiment, the purge gas introduction unit 20 is installed in the container body 16a below the refrigerator housing cylinder 16b so as to blow purge gas onto the distal part of the cryopanel 38 away from the second cooling stage 34. The axial height of the purge valve 20a and the opening 20b is set so as to blow the purge gas flow onto the outer circumference of the bottom cryopanel 38b1. The purge gas blown out from the purge valve 20a is blown onto the outer circumference of the bottom cryopanel 38b1 through the opening 20b. This optimization of purge gas introduction promotes the heating of the cryopanel 38, especially the bottom cryopanel 38b1. The heating time of the cryopanel 38 can be shortened, and furthermore, the regeneration time can be shortened.

[0058] Figure 3 is a schematic diagram of a cryopump according to Modification 1. The cryopump 10 shown in Figure 3 differs from the cryopump 10 in Figure 1 in the shape of its lower cryopanel 38b. Each lower cryopanel 38b, including the bottom cryopanel 38b1, is arranged parallel to a plane perpendicular to the axial direction (the direction of the cryopump's central axis C), as shown in the figure. The lower cryopanels 38b are flat plates and have a circular shape.

[0059] The purge gas introduction section 20 is installed in the container body 16a below the refrigerator housing cylinder 16b so as to blow purge gas onto the distal part of the cryopanel 38 away from the second cooling stage 34. In this embodiment, the purge valve 20a and opening 20b are installed on the side of the container body 16a at an axial height aligned with the bottom cryopanel 38b1. The axial height of the purge valve 20a and opening 20b is determined so as to blow a purge gas flow parallel to a plane perpendicular to the axial direction onto the bottom cryopanel 38b1. For example, the purge valve 20a and opening 20b are at the same axial height as the outer circumference of the bottom cryopanel 38b1. The axial height of the purge valve 20a and opening 20b may be determined so as to blow a purge gas flow between the bottom cryopanel 38b1 and the adjacent lower cryopanel 38bb directly above it. For understanding, Figure 3 schematically shows the flow of purge gas blown from the purge gas inlet 20 to the bottom cryo panel 38b1 using arrows.

[0060] In this way, the heating of the cryopanel 38, especially the bottom cryopanel 38b1, is accelerated. The heating time of the cryopanel 38 can be shortened, and furthermore, the regeneration time can be shortened.

[0061] Figures 4(a) and 4(b) schematically show a cryopump according to Modification 2. The cryopump 10 shown in Figure 4 differs from the cryopump 10 in Figure 1 in the arrangement of the cryopanel 38. This cryopump 10 is also a horizontal cryopump, similar to the embodiment described above.

[0062] Each of the cryopanels 38 extends axially from top to bottom relative to the second cooling stage 34 of the refrigerator 14, as shown in Figure 4(a). These cryopanels 38 are arranged radially as viewed from the cryopump intake port 17, as shown in Figure 4(b). The cryopanels 38 are arranged relatively densely to increase the exhaust velocity and storage capacity of the gas (e.g., a non-condensable gas). At least four, or at least eight, or at least sixteen cryopanels 38 may be arranged radially. Each cryopanel 38 is attached to a flat (e.g., disc-shaped) cryopanel mounting member 42 that is positioned perpendicular to the axial direction and is thermally coupled to the second cooling stage 34 via the cryopanel mounting member 42.

[0063] The lower part of the cryopanel 38, which is positioned between the second cooling stage 34 and the bottom of the container body 16a, is allocated more space than the upper part of the cryopanel 38, which is positioned between the second cooling stage 34 and the cryopump air intake port 17. When the axial distance La from the upper end of the cryopanel 38 to the upper surface of the second cooling stage 34 is 1, the axial distance Lb from the lower end of the cryopanel 38 to the upper surface of the second cooling stage 34 may be in the range of 1 to 3, or in the range of 1 to 2. That is, La ≤ Lb ≤ 3La (or 2La).

[0064] The purge gas inlet 20 is installed in the container body 16a below the refrigerator housing cylinder 16b so as to blow purge gas onto the distal part of the cryopanel 38 away from the second cooling stage 34. In this embodiment, the purge valve 20a and opening 20b are installed on the side of the container body 16a at an axial height aligned with the lower part (e.g., the lower end) of the cryopanel 38. For understanding, Figure 4(a) schematically shows the flow of purge gas blown from the purge gas inlet 20 onto the lower part of the cryopanel 38 with arrows. Even in this way, the heating of the cryopanel 38 is promoted. The heating time of the cryopanel 38 can be shortened, and furthermore, the regeneration time can be shortened.

[0065] Figures 5(a) to 5(c) schematically show examples of purge gas diffusion members applicable to a cryopump according to an embodiment. As shown in Figure 5(a), the purge gas introduction section 20 may include a purge gas diffusion member 44 provided at the outlet or opening 20b of the purge valve 20a. The purge gas diffusion member 44 may include a swirling vane, as shown in Figure 5(b). The swirling vane is itself a fixed blade fixedly installed on the purge valve 20a and generates a swirling flow in the passing purge gas. By providing the purge gas diffusion member 44, the high-speed purge gas flow blown out from the purge valve 20a can be diffused and applied to a wider area of ​​the cryopanel 38, thereby promoting the heating of the cryopanel 38.

[0066] As shown in Figure 5(c), the purge gas diffusion member 44 may include a cone (for example, having a conical shape) positioned with its apex facing the outlet of the purge valve 20a. In this way as well, the high-speed purge gas flow blown out from the purge valve 20a can be diffused.

[0067] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention.

[0068] The purge gas introduction section 20 may include a conduit for guiding the purge gas from the purge valve 20a to the cryopanel 38. The conduit may be provided through the radiation shield 36. The tip of the conduit may be positioned near the distal end of the cryopanel 38, and the purge gas introduction section 20 may blow the purge gas introduced from the purge valve 20a through the conduit onto the distal end of the cryopanel 38. [Industrial applicability]

[0069] This invention can be used in the field of cryopumps. [Explanation of Symbols]

[0070] 10 Cryopump, 14 Refrigerator, 16 Cryopump container, 16a Container body, 16b Refrigerator housing cylinder, 17 Cryopump air intake, 20 Purge gas introduction section, 20a Purge valve, 20b Opening, 21 Purge gas source, 30 First cooling stage, 34 Second cooling stage, 36 Radiation shield, 38 Cryopanel, 38a Upper cryopanel, 38a1 Top cryopanel, 38b Lower cryopanel, 38b1 Bottom cryopanel, 44 Purge gas diffusion member.

Claims

1. A cryopump container having a cryopump intake port and a container body extending axially in a cylindrical shape from the cryopump intake port, and a refrigerator housing cylinder connected to the side of the container body, A refrigerator fixed to the refrigerator housing cylinder and extending in a direction perpendicular to the axial direction within the cryopump container, the refrigerator having a first cooling stage and a second cooling stage that cools to a lower temperature than the first cooling stage, A plurality of cryopanels, each thermally coupled to the second cooling stage and capable of adsorbing non-condensable gases, are arranged axially between the cryopump intake and the bottom of the container body, or arranged radially when viewed from the cryopump intake, A purge gas introduction unit is installed in the container body below the refrigerator housing cylinder so as to blow purge gas onto the distal part of the cryopanel away from the second cooling stage, The container body comprises a radiant shield arranged around the plurality of cryopanels and thermally coupled to the first cooling stage, The purge gas introduction section is installed in the container body below the refrigerator housing cylinder and includes a purge valve that connects the cryopump container to the purge gas source. The radiation shield is provided with an opening that allows the purge gas ejected from the purge valve into the cryopump container to pass through the radiation shield. The cryopump is characterized in that the opening is located below the refrigerator housing cylinder and in front of the purge valve.

2. The plurality of cryopanels include a plurality of lower cryopanels arranged in the axial direction between the second cooling stage and the bottom of the container body, The cryopump according to claim 1, characterized in that the purge gas introduction section is installed on the side of the container body at an axial height that matches the lower cryo panel furthest from the second cooling stage among the plurality of lower cryo panels.

3. The lower cryo panel, which is furthest from the second cooling stage, is arranged parallel to the plane perpendicular to the axial direction. The cryopump according to claim 2, characterized in that the purge gas introduction section is installed on the side of the container body at an axial height determined to blow a purge gas flow parallel to a plane perpendicular to the axial direction onto the lower cryo panel furthest from the second cooling stage.

4. The lower cryopanel, which is furthest from the second cooling stage, has an outer periphery inclined with respect to a plane perpendicular to the axial direction, The cryopump according to claim 2, characterized in that the purge gas introduction section is installed on the side of the container body at an axial height determined to blow the purge gas flow onto the outer periphery of the lower cryo panel, which is furthest from the second cooling stage.

5. The plurality of cryopanels include a plurality of upper cryopanels arranged axially between the second cooling stage and the cryopump intake port. The cryopump according to any one of claims 2 to 4, characterized in that when the axial distance from the upper cryo panel closest to the cryopump intake port to the upper surface of the second cooling stage is denoted as La, and the axial distance from the lower cryo panel furthest from the second cooling stage to the upper surface of the second cooling stage is denoted as Lb, La ≤ Lb ≤ 3La.

6. The cryopump according to claim 5, characterized in that the plurality of upper cryopanels are at least three upper cryopanels arranged in the axial direction between the upper surface of the second cooling stage and the cryopump intake port.

7. The cryopump according to claim 5 or 6, characterized in that the plurality of lower cryopanels are at least five lower cryopanels arranged in the axial direction between the upper surface of the second cooling stage and the bottom of the container body.

8. The plurality of cryopanels are arranged radially when viewed from the cryopump intake port, and each of the cryopanels extends in the axial direction from above to below with respect to the second cooling stage. The cryopump according to claim 1, characterized in that the purge gas introduction section is installed on the side of the container body at an axial height aligned with the lower part of the cryo panel, which is positioned between the second cooling stage and the bottom of the container body.

9. The cryopump according to claim 8, characterized in that when the axial distance from the upper ends of the plurality of cryopanels to the upper surface of the second cooling stage is denoted as La, and the axial distance from the lower ends of the plurality of cryopanels to the upper surface of the second cooling stage is denoted as Lb, La ≤ Lb ≤ 3La.

10. The cryopump according to any one of claims 1 to 9, characterized in that the purge valve and the opening are installed on the side of the container body at an axial height aligned with the distal portion of the cryopanel.

11. The cryopump according to any one of claims 1 to 10, characterized in that the purge gas introduction section comprises a purge gas diffusion member provided at the outlet or opening of the purge valve.

12. The cryopump according to claim 11, characterized in that the purge gas diffusion member is provided with swirling vanes.

13. The cryopump according to any one of claims 1 to 12, characterized in that the purge gas introduction section is provided on the side of the container body on the same side as the refrigerator housing cylinder when viewed from the cryopump intake port.

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