Cryogenic pump

Abstract

The low temperature pump (10) of the present application is provided with: a low temperature pump container (16) having a container main body (16a) defining a low temperature pump intake port (17) and a refrigerator housing cylinder (16b) connected to a side portion of the container main body (16a); a refrigerator (14) fixed to the refrigerator housing cylinder (16b) and having a first cooling stage (30) and a second cooling stage (34) cooled to a lower temperature than the first cooling stage (30); a plurality of low temperature plates (38) thermally connected to the second cooling stage (34) and each capable of adsorbing a non-condensable gas, the plurality of low temperature plates being arranged in a direction from the low temperature pump intake port (17) toward a bottom portion of the container main body (16a) or radially arranged when viewed from the low temperature pump intake port (17); and a purge gas introduction portion (20) provided on the container main body (16a) at a position lower than the refrigerator housing cylinder (16b) to blow a purge gas toward a distal end portion of the low temperature plate (38) distanced from the second cooling stage (34).

Description

Technical Field

[0001] This invention relates to a cryogenic pump. Background Technology

[0002] A cryogenic pump is a vacuum pump that uses condensation or adsorption to trap gas molecules onto a cryogenic plate cooled to ultra-low temperatures, thereby releasing the trapped gas. Cryogenic pumps are typically used to achieve the clean vacuum environments required in processes such as semiconductor circuit manufacturing. Because cryogenic pumps are so-called gas trapping vacuum pumps, they require periodic regeneration to release the trapped gas.

[0003] Previous technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2011-137423 Summary of the Invention

[0006] The technical problem to be solved by the invention

[0007] One of the exemplary objectives of one embodiment of the present invention is to shorten the regeneration time of cryogenic pumps.

[0008] means for solving technical problems

[0009] According to one embodiment of the present invention, a cryogenic pump comprises: a cryogenic pump container having a container body that defines a cryogenic pump inlet and extends axially in a cylindrical shape from the cryogenic pump inlet, and a refrigerator housing connected to a side of the container body; a refrigerator fixed to the refrigerator housing and extending within the cryogenic pump container in a direction perpendicular to the axial direction, and the refrigerator having a first cooling platform and a second cooling platform cooled to a temperature lower than the first cooling platform; a plurality of cryogenic plates thermally connected to the second cooling platform, and each cryogenic plate being capable of adsorbing non-condensable gases, the plurality of cryogenic plates being arranged axially between the cryogenic pump inlet and the bottom of the container body or arranged radially when viewed from the cryogenic pump inlet; and a purge gas inlet provided on the container body up to a lower position than the refrigerator housing, thereby spraying purge gas toward the distal end of the cryogenic plate away from the second cooling platform.

[0010] Furthermore, any combination of the above-mentioned constituent elements, or the substitution of the constituent elements or expressions of the present invention among methods, apparatuses, and systems, are also valid embodiments of the present invention.

[0011] Invention Effects

[0012] According to the present invention, the regeneration time of cryogenic pumps can be shortened. Attached Figure Description

[0013] Figure 1This is a schematic diagram illustrating the cryogenic pump involved in the embodiment.

[0014] Figure 2 This is a schematic diagram illustrating the cryogenic pump involved in the comparative example.

[0015] Figure 3 This is a schematic diagram illustrating the cryogenic pump involved in Modification 1.

[0016] Figure 4 Figures (a) and (b) are schematic representations of the cryogenic pump involved in Modification 2.

[0017] Figure 5 Figures (a) to (c) are schematic representations of examples of purge gas diffusion components applicable to the cryogenic pumps involved in the embodiments. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same or equivalent constituent elements, components, and processes are labeled with the same symbols, and repeated descriptions are omitted where appropriate. In the drawings, scales and shapes of various parts are appropriately shown for ease of explanation, and are not intended to be limiting unless otherwise stated. The embodiments are illustrative and do not limit the scope of the invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0019] Figure 1 This diagram schematically illustrates the cryogenic pump 10 according to an embodiment. The cryogenic pump 10 is, for example, installed in the vacuum chamber of an ion implantation apparatus, sputtering apparatus, evaporation apparatus, or other vacuum processing apparatus, and is used to increase the vacuum level inside the vacuum chamber to the level required in the desired vacuum processing. For example, to achieve a vacuum level of 10... -5 Pa to 10 -8 A high vacuum of approximately Pa.

[0020] The cryogenic pump 10 includes a compressor 12, a refrigerator 14, and a cryogenic pump container 16 with a cryogenic pump inlet 17. Furthermore, the cryogenic pump 10 includes a roughing valve 18, a purge valve 20a, and a vent valve 22, all of which are mounted on the cryogenic pump container 16. The cryogenic pump 10 also includes a radiation shield 36 housed within the cryogenic pump container 16 and multiple cryogenic plates 38. The purge valve 20a, together with an opening 20b provided on the radiation shield 36, constitutes a purge gas inlet 20.

[0021] Compressor 12 is configured to recover refrigerant gas from refrigerator 14, pressurize the recovered refrigerant gas, and then supply it back to refrigerator 14. Refrigerator 14, also referred to as an expander or cold head, together with compressor 12 constitutes a cryogenic refrigerator. The circulation of refrigerant gas between compressor 12 and refrigerator 14, accompanied by appropriate pressure and volume changes of the refrigerant gas within refrigerator 14, constitutes a thermodynamic cycle that generates cold, enabling refrigerator 14 to provide cryogenic cooling. The refrigerant gas is typically helium, but other suitable gases may also be used. For ease of understanding, Figure 1 Arrows are used to indicate the direction of refrigerant gas flow. As an example, the cryogenic refrigerator is a two-stage Gifford-McMahon (GM) refrigerator, but it can also be a pulse tube refrigerator, a Stirling refrigerator, or other types of cryogenic refrigerators.

[0022] The refrigerator 14 includes a room temperature section 26, a first cylinder 28, a first cooling platform 30, a second cylinder 32, and a second cooling platform 34. The refrigerator 14 is configured to cool the first cooling platform 30 to a first cooling temperature and the second cooling platform 34 to a second cooling temperature. The second cooling temperature is lower than the first cooling temperature. For example, the first cooling platform 30 is cooled to approximately 65K to 120K, preferably to 80K to 100K, and the second cooling platform 34 is cooled to approximately 10K to 20K. The first cooling platform 30 and the second cooling platform 34 may also be referred to as a high-temperature cooling platform and a low-temperature cooling platform, respectively.

[0023] The first cylinder block 28 connects the first cooling platform 30 to the room temperature section 26, thereby structurally supporting the first cooling platform 30 on the room temperature section 26. The second cylinder block 32 connects the second cooling platform 34 to the first cooling platform 30, thereby structurally supporting the second cooling platform 34 on the first cooling platform 30. The first cylinder block 28 and the second cylinder block 32 extend coaxially, and the room temperature section 26, the first cylinder block 28, the first cooling platform 30, the second cylinder block 32, and the second cooling platform 34 are arranged in a straight line in sequence.

[0024] In the case where the refrigerator 14 is a two-stage GM refrigerator, a first displacement device and a second displacement device (not shown) are respectively arranged inside the first cylinder 28 and the second cylinder 32 in a reciprocating manner. A first accumulator and a second accumulator (not shown) are respectively assembled in the first displacement device and the second displacement device. Furthermore, the room temperature section 26 has a drive mechanism (not shown) such as a motor for reciprocating the first displacement device and the second displacement device. The drive mechanism includes a flow path switching mechanism that switches the flow path of the working gas so as to periodically and repeatedly supply working gas (e.g., helium) into and discharge working gas from the interior of the refrigerator 14.

[0025] The cryogenic pump container 16 has a container body 16a and a cryogenic compressor housing 16b. The cryogenic pump container 16 is a vacuum container designed to maintain a vacuum during vacuum exhaust operation of the cryogenic pump 10 and to withstand ambient pressure (e.g., atmospheric pressure). The container body 16a defines the cryogenic pump inlet 17 and extends axially from the cryogenic pump inlet 17 (along...) Figure 1 The cryogenic pump extends in a cylindrical shape (in the direction of the central axis C shown). The container body 16a has a cylindrical shape with a cryogenic pump inlet 17 at one end in the axial direction and the other end in the axial direction is closed. A radiation shield 36 is housed within the container body 16a, and a second cooling platform 34 and a cryogenic plate 38 are also housed within the radiation shield 36. One end of the refrigerator housing 16b is connected to the container body 16a, and the other end is fixed to the room temperature section 26 of the refrigerator 14. The refrigerator 14 is inserted into the refrigerator housing 16b, and a first cylinder 28 is housed within it.

[0026] In this embodiment, the cryogenic pump 10 is a so-called horizontal cryogenic pump in which the refrigerator 14 is disposed on the side of the container body 16a. The refrigerator 14 is fixed to the refrigerator housing 16b and extends in a direction perpendicular to the axial direction within the cryogenic pump container 16. A refrigerator insertion port is provided on the side of the container body 16a, and the refrigerator housing 16b is connected to the side of the container body 16a at this refrigerator insertion port. Similarly, on the side of the radiation shield 36, adjacent to the refrigerator insertion port of the container body 16a, a hole is also provided for the refrigerator 14 to pass through. The second cylinder 32 and the second cooling platform 34 of the refrigerator 14 are inserted into the radiation shield 36 through these holes, and the radiation shield 36 is thermally connected to the first cooling platform 30 around the holes on its side.

[0027] The cryogenic pump can be configured in various positions at the point of use. As an example, the cryogenic pump 10 can be configured in the horizontal position shown in the figure (i.e., the cryogenic pump inlet 17 is facing upwards). In this case, the bottom of the container body 16a is below the cryogenic pump inlet 17, and the refrigerator 14 extends horizontally.

[0028] A roughing valve 18 is provided on the cryogenic pump container 16 (e.g., the refrigerator housing 16b). The roughing valve 18 is connected to a roughing pump (not shown) located outside the cryogenic pump 10. The roughing pump is a vacuum pump used to evacuate the cryogenic pump 10 to its operating start pressure. When the roughing valve 18 is open, the cryogenic pump container 16 is in communication with the roughing pump; when the roughing valve 18 is closed, the cryogenic pump container 16 is disconnected from the roughing pump. Opening the roughing valve 18 and activating the roughing pump allows for pressure reduction of the cryogenic pump 10.

[0029] A purge valve 20a is disposed on the cryogenic pump container 16. In this embodiment, it is disposed on the container body 16a at a position lower than the refrigeration unit housing 16b. The purge valve 20a is connected to a purge gas source 21 disposed outside the cryogenic pump 10. An opening 20b is provided on the radiation shield 36 to guide the purge gas ejected from the purge valve 20a into the cryogenic pump container 16 into the radiation shield 36. The opening 20b is disposed on the front of the purge valve 20a. When the purge valve 20a is open, purge gas is supplied from the purge valve 20a into the radiation shield 36 through the opening 20b. When the purge valve 20a is closed, the purge gas supply to the cryogenic pump container 16 is cut off.

[0030] The purge gas can be, for example, nitrogen or other dry gas, and its temperature can be adjusted to room temperature or heated to a temperature higher than room temperature. By opening the purge valve 20a to introduce the purge gas into the cryogenic pump container 16, the pressure inside the cryogenic pump 10 can be increased from vacuum to atmospheric pressure or a higher pressure. Furthermore, the cryogenic pump 10 can be heated from ultra-low temperature to room temperature or a higher temperature.

[0031] In this embodiment, when viewed from the cryogenic pump inlet 17, the purge gas inlet 20 is located on the side of the container body 16a on the same side as the refrigeration unit housing 16b. By placing the purge gas inlet 20 on the same side as other valves such as the coarse extraction valve 18, along with the refrigeration unit housing 16b, the associated piping or wiring can be centrally located, thus facilitating the operation of these piping and wiring.

[0032] A vent valve 22 is provided on the cryogenic pump container 16 (e.g., the refrigerator housing 16b). The purpose of the vent valve 22 is to discharge fluid from the inside of the cryogenic pump 10 to the outside. The vent valve 22 may be connected to a storage tank (not shown) outside the cryogenic pump 10 to receive the discharged fluid. Alternatively, if the discharged fluid is harmless, the vent valve 22 may be configured to directly discharge the discharged fluid into the surrounding environment. The fluid discharged from the vent valve 22 is primarily a gas, but may also be a liquid or a gas-liquid mixture.

[0033] The vent valve 22 can be, for example, a normally closed control valve, which can be opened during regeneration or when fluid is discharged from the cryogenic pump container 16, and closed when discharge is not required. The vent valve 22 can also be configured to function as a so-called safety valve that opens mechanically based on a predetermined pressure differential. When the internal pressure of the cryogenic pump becomes high for some reason, the vent valve 22 is mechanically opened, thereby releasing the internal high pressure.

[0034] The radiation shield 36 is thermally connected to the first cooling platform 30 and is therefore cooled to a first cooling temperature, thereby providing protection of the cryogenic surface of the cryogenic plate 38 from radiant heat from the outside of the cryogenic pump 10 or the cryogenic pump container 16. The radiation shield 36 is disposed within the container body 16a around a plurality of cryogenic plates 38. The radiation shield 36 has a shape, for example, cylindrical, surrounding the cryogenic plates 38 and the second cooling platform 34. The end of the radiation shield 36 on the cryogenic pump inlet 17 side is open, allowing gas to enter the radiation shield 36 from the outside of the cryogenic pump 10 through the cryogenic pump inlet 17. The end of the radiation shield 36 opposite to the cryogenic pump inlet 17 is closed. Alternatively, the end of the radiation shield 36 opposite to the cryogenic pump inlet 17 may also be open or closed. A gap exists between the radiation shield 36 and the cryogenic plate 38, and the radiation shield 36 does not contact the cryogenic plate 38. The radiation shield 36 also does not contact the cryogenic pump container 16.

[0035] An inlet cryogenic plate 37, fixed to the open end of the radiation shield 36, may be provided at the cryogenic pump inlet 17. The inlet cryogenic plate 37 is cooled to the same temperature as the radiation shield 36, thereby enabling so-called Type I gases (gases such as water vapor that condense at relatively high temperatures) to condense on its surface. The inlet cryogenic plate 37 may be, for example, a louver or a baffle, but may also be a plate or component of a circular or other shape configured to occupy part of the cryogenic pump inlet 17.

[0036] The cryogenic plate 38 is thermally connected to the second cooling stage 34 and is therefore cooled to a second cooling temperature, providing an ultra-low temperature surface for condensing second-type gases (e.g., gases that condense at relatively low temperatures, such as argon and nitrogen). Furthermore, to adsorb third-type gases (e.g., non-condensable gases such as hydrogen), activated carbon or other adsorbent materials are disposed on at least a portion of the surface of the cryogenic plate 38. Such adsorption regions can be formed in areas not visible from the cryogenic pump inlet 17 (e.g., the surface of the cryogenic plate 38 opposite to the cryogenic pump inlet 17, or a region that forms a shadow over an adjacent cryogenic plate 38 above). The adsorption regions of each cryogenic plate 38 can be formed on the entire surface or most of the surface of that cryogenic plate 38 not visible from the cryogenic pump inlet 17. Since multiple cryogenic plates 38 are capable of adsorbing non-condensable gases, they can also be referred to as adsorption cryogenic plates. Gas entering the radiation shield 36 from outside the cryogenic pump 10 through the cryogenic pump inlet 17 is captured onto the cryogenic plates 38 by condensation or adsorption.

[0037] The radiation shield 36, cooled to the first cooling temperature, and the inlet cryogenic plate 37 can be collectively referred to as the high-temperature cryogenic plate. The cryogenic plate 38, cooled to a second cooling temperature lower than the first cooling temperature, can also be referred to as the low-temperature cryogenic plate.

[0038] The radiation shielding component 36, the inlet cryogenic plate 37, and the cryogenic plate 38, etc., which are cooled to ultra-low temperatures, are formed of metals such as copper and aluminum, or other materials with high thermal conductivity. Each component may also have a main body formed of such a material with high thermal conductivity and a cladding layer (e.g., a nickel layer) covering the main body.

[0039] Multiple cryogenic plates 38 are arranged axially between the cryogenic pump inlet 17 and the bottom of the container body 16a. Hereinafter, for ease of explanation, the cryogenic plate 38 positioned above the second cooling platform 34 will be referred to as the upper cryogenic plate 38a, and the cryogenic plate 38 positioned below the upper cryogenic plate 38a will be referred to as the lower cryogenic plate 38b.

[0040] The upper cryogenic plates 38a have an inverted frustum-shaped shape, and their centers are located on the central axis C of the cryogenic pump. The circular central portion of the upper cryogenic plate 38a is arranged perpendicular to the axial direction, and the outer periphery is inclined relative to a plane perpendicular to the axial direction. The outer periphery of the upper cryogenic plate 38a extends obliquely upward and radially outward from the central portion. A gap exists between the outer peripheries of two axially adjacent upper cryogenic plates 38a, into which gas entering from the cryogenic pump inlet 17 can be received. Figure 1 As shown, a portion of the upper cryogenic plate 38a (e.g., at least one upper cryogenic plate 38a near the cryogenic pump inlet 17) may not be an inverted frustum-shaped plate but a flat plate (e.g., circular).

[0041] The diameter of the multiple upper cryogenic plates 38a increases as they move away from the cryogenic pump inlet 17. The upper cryogenic plate 38a closest to the cryogenic pump inlet 17 (hereinafter, for convenience, it is also referred to as the top cryogenic plate 38a1) has the smallest diameter. The top cryogenic plate 38a1 is located directly below the inlet cryogenic plate 37 and is the upper cryogenic plate 38a furthest from the second cooling platform 34 in the axial direction. The diameter of the upper cryogenic plates 38a increases as they move closer to the second cooling platform 34 from the top cryogenic plate 38a1.

[0042] Furthermore, the multiple upper cryogenic plates 38a can also be configured such that their depth (axial distance from the center to the outer periphery) increases with distance from the cryogenic pump inlet 17. Like the upper cryogenic plates 38a near the second cooling platform 34, the upper cryogenic plates 38a can also be configured in a nested manner. That is, the lower part of the upper cryogenic plate 38a can be embedded in the lower, adjacent upper cryogenic plate 38a. As shown, the inclination angle of the outer periphery of the upper cryogenic plate 38a can be set to be greater for the lower upper cryogenic plate 38a. This inclination angle can also be the same for several (or all) adjacent upper cryogenic plates 38a.

[0043] To mount multiple upper cryogenic plates 38a onto the second cooling platform 34, multiple heat conductors 40 are provided. Each heat conductor 40 has a short cylindrical or plate-like shape, with a diameter equal to the diameter of the central portion of the upper cryogenic plate 38a. The upper cryogenic plates 38a and heat conductors 40 are alternately arranged on the central shaft C of the cryogenic pump, thereby forming a cylindrical portion extending along the central shaft C of the cryogenic pump from the central portion of the upper cryogenic plate 38a and the heat conductor 40. Bolt holes are provided axially through this cylindrical portion toward the second cooling platform 34, and long bolts are inserted into these bolt holes to secure the cylindrical portion to the second cooling platform 34. Thus, the upper cryogenic plates 38a and heat conductors 40 are fixed to the second cooling platform 34 and thermally connected to it. Alternatively, the upper cryogenic plates 38a and heat conductors 40 can also be joined together by other methods such as bonding or welding.

[0044] Multiple lower cryogenic plates 38b are arranged axially between the second cooling platform 34 and the bottom of the container body 16a. Similar to the upper cryogenic plate 38a, the lower cryogenic plates 38b also have an inverted frustum-shaped shape, and their respective centers are located on the central axis C of the cryogenic pump. The lower cryogenic plates 38b have an outer periphery inclined relative to a plane perpendicular to the axial direction. The outer periphery of the lower cryogenic plates 38b extends obliquely upward and radially outward from its center. A gap exists between the outer peripheries of two axially adjacent lower cryogenic plates 38b, allowing gas entering from the cryogenic pump inlet 17 to be received into this gap.

[0045] The lower cryogenic plate 38b has a larger diameter and depth than the upper cryogenic plate 38a, and its diameter and depth increase with distance from the cryogenic pump inlet 17. Therefore, the lower cryogenic plate 38b furthest from the second cooling platform 34 (hereinafter, for convenience, it is also referred to as the bottom cryogenic plate 38b1) has the largest diameter and depth among the cryogenic plates 38. Similar to the upper cryogenic plate 38a, the lower cryogenic plate 38b can also be configured in a nested arrangement. As shown, the inclination angle of the outer periphery of the lower cryogenic plate 38b can be set to be larger for the lower cryogenic plate 38b located below. This inclination angle can also be the same for several (or all) adjacent lower cryogenic plates 38b.

[0046] A low-temperature plate mounting member 42 is provided to mount the lower low-temperature plate 38b onto the second cooling platform 34. The low-temperature plate mounting member 42 is fixed to the second cooling platform 34 and extends axially downward from the second cooling platform 34. A plurality of lower low-temperature plates 38b are spaced apart from each other axially, and their respective center portions are mounted to the low-temperature plate mounting member 42. To accommodate the second cooling platform 34 and the low-temperature plate mounting member 42 at their center portions, a notch extending from the outer periphery to the center portion is formed in each lower low-temperature plate 38b. Thus, the lower low-temperature plates 38b are thermally connected to the second cooling platform 34 via the low-temperature plate mounting member 42.

[0047] To increase the exhaust velocity and adsorption capacity of the gas (e.g., non-condensable gas), the cryogenic plates 38 are configured compactly. At least three, four, or five upper cryogenic plates 38a may be arranged axially between the inlet cryogenic plate 37 and the upper surface of the second cooling platform 34. The top cryogenic plate 38a1 may be configured close to the inlet cryogenic plate 37, and the axial distance from the top cryogenic plate 38a1 to the inlet cryogenic plate 37 may be less than or less than half the axial distance from the top cryogenic plate 38a1 to the upper surface of the second cooling platform 34. Alternatively, the axial distance from the top cryogenic plate 38a1 to the inlet cryogenic plate 37 may also be less than the axial distance from the top cryogenic plate 38a1 to the adjacent upper cryogenic plate 38a directly below it.

[0048] Furthermore, at least three, at least five, or at least ten lower cryogenic plates 38b may be arranged axially between the bottom of the radiation shield 36 and the upper surface of the second cooling platform 34. The lower cryogenic plates 38b1 may be configured close to the bottom of the radiation shield 36, and the axial distance from the lower cryogenic plate 38b1 to the bottom of the radiation shield 36 may be less than, or less than half or less than one-third of, the axial distance from the lower cryogenic plate 38b1 to the upper surface of the second cooling platform 34. Alternatively, the axial distance from the lower cryogenic plate 38b1 to the bottom of the radiation shield 36 may also be less than the axial distance from the lower cryogenic plate 38b1 to the adjacent lower cryogenic plate 38b directly above it.

[0049] The bottom cryogenic plate 38b1 is relatively large among the cryogenic plates 38, and can be the largest. The bottom cryogenic plate 38b1 can be larger than the top cryogenic plate 38a1, and the area of ​​the bottom cryogenic plate 38b1 can be approximately 1.5 to approximately 5 times the area of ​​the top cryogenic plate 38a1. The diameter of the bottom cryogenic plate 38b1 can be at least 70%, at least 80%, or at least 90% of the diameter of the cryogenic pump inlet 17.

[0050] The lower cryogenic plate 38b has a larger space than the upper cryogenic plate 38a. When the axial distance La from the top cryogenic plate 38a1 to the upper surface of the second cooling platform 34 is set to 1, the axial distance Lb from the bottom cryogenic plate 38b1 to the upper surface of the second cooling platform 34 can be in the range of 1 to 3 or 1 to 2. That is, it can be La ≤ Lb ≤ 3La (or 2La). A greater number of lower cryogenic plates 38b than upper cryogenic plates 38a can be configured on the cryogenic pump 10.

[0051] Multiple low-temperature plates 38 are not limited to reference. Figure 1The specific configuration and shape described above can take various forms. For example, the shape of the low-temperature plate 38 is not limited to an inverted frustum shape; it can also be other shapes that bulge downwards or are flat, etc. For other exemplary forms of the low-temperature plate 38, see [reference]. Figure 3 and Figure 4 This will be discussed later.

[0052] The cryogenic pump 10 is suitable for applications involving the high-speed discharge of non-condensable gases such as hydrogen (e.g., ion implantation devices). Figure 1 The cryogenic pump 10 shown is designed to have a hydrogen capture probability of at least 20%, at least 25%, or at least 30%. Furthermore, Figure 3 and Figure 4 The cryogenic pump 10 shown is also designed to have a hydrogen capture probability of at least 20%, at least 25%, or at least 30%.

[0053] The hydrogen capture probability is expressed as the ratio of the actual hydrogen exhaust velocity to the maximum theoretical hydrogen exhaust velocity in a cryogenic pump with the same orifice diameter as cryogenic pump 10 (i.e., the same orifice area). The actual hydrogen exhaust velocity of the cryogenic pump can be determined using the well-known Montto Carlo simulation method. The theoretical hydrogen exhaust velocity can be considered equal to the gas conductivity of the molecular flow at its opening. The gas conductivity C(hydrogen) can be derived from the gas conductivity C(air) at 20°C using the following formula.

[0054]

[0055] Where T is the temperature of hydrogen (K), and M is the molecular weight of hydrogen (i.e., M = 2). The gas conductivity C (air at 20℃) and the opening area A (m²) of air at 20℃ are related. 2 The equation is proportional to C(20°C air) = 116A. For example, in the case of a cryogenic pump with a diameter of 250 mm, the theoretical hydrogen exhaust velocity is approximately 20840 L / s according to the above equation. At this time, a hydrogen capture probability of 30% is equivalent to a hydrogen exhaust velocity of approximately 6252 L / s for the cryogenic pump.

[0056] Alternatively, a low-temperature plate without adsorption material on its surface can be provided; this can be referred to as a condensing low-temperature plate. That is, the condensing low-temperature plate cannot adsorb non-condensable gases, but it can capture Class 2 gases through condensation. For example, the low-temperature plate near the cryogenic pump inlet 17 in the upper low-temperature plate 38a (e.g., the top low-temperature plate 38a1) can be a condensing low-temperature plate.

[0057] In this embodiment, the purge gas inlet 20 is positioned below the refrigerator housing 16b in the container body 16a, spraying purge gas toward the distal end of the cryogenic plate 38, which is away from the second cooling platform 34. In this embodiment, the purge valve 20a and opening 20b are positioned on the side of the container body 16a at an axial height corresponding to the bottom cryogenic plate 38b1. The axial height of the purge valve 20a and opening 20b is determined to spray a purge gas flow toward the outer periphery of the bottom cryogenic plate 38b1. For example, the purge valve 20a and opening 20b are located at the same axial height as the outer periphery of the bottom cryogenic plate 38b1. For ease of understanding, in Figure 1 The arrows in the diagram represent the purge gas flow that is sprayed from the purge gas inlet 20 to the bottom cryogenic plate 38b1.

[0058] The operation of the cryogenic pump 10 with the above-described structure will now be explained. When the cryogenic pump 10 is in operation, firstly, the vacuum chamber is roughly evacuated to approximately 1 Pa using another suitable roughing pump before operation. Then, the cryogenic pump 10 is started. Driven by the refrigerator 14, the first cooling stage 30 and the second cooling stage 34 are cooled to the first cooling temperature and the second cooling temperature, respectively. Therefore, the radiation shield 36 and the inlet cryogenic plate 37, which are thermally connected to the first cooling stage 30, are also cooled to the first cooling temperature. The cryogenic plate 38, which is thermally connected to the second cooling stage 34, is cooled to the second cooling temperature.

[0059] The inlet cryogenic plate 37 cools the gas flying from the vacuum chamber toward the cryogenic pump 10. Type 1 gases, such as water vapor, condense on the surfaces of the radiation shield 36 and the inlet cryogenic plate 37. At the first cooling temperature, the vapor pressure of Type 2 gases, such as argon, or Type 3 gases, such as hydrogen, does not decrease sufficiently, thus they enter the internal space of the cryogenic pump 10 from the cryogenic pump inlet 17. Type 2 gases incident on the cryogenic plate 38 are cooled and condensed by the cryogenic plate 38. Type 3 gases are adsorbed into the adsorption region of the cryogenic plate 38. In this way, the cryogenic pump 10 can exhaust various gases through condensation or adsorption, thereby achieving the desired vacuum level in the vacuum chamber.

[0060] As the cryogenic pump 10 continuously operates under vacuum, gas gradually accumulates within it. To expel the accumulated gas to the outside, the cryogenic pump 10 needs to be regenerated. The regeneration of the cryogenic pump 10 typically includes a heating process, a venting process, and a cooling process.

[0061] The heating process includes raising the temperature of the cryogenic plate 38 to the regeneration temperature (e.g., room temperature or a higher temperature). The heat source for heating is, for example, a refrigerator 14. The refrigerator 14 is capable of heating operation (so-called reverse heating). That is, the refrigerator 14 is configured such that when the drive mechanism located in the room temperature section 26 operates in the opposite direction to the cooling operation, the working gas undergoes adiabatic compression. The heat of compression thus obtained heats the refrigerator 14 with respect to the first cooling stage 30 and the second cooling stage 34. The radiation shield 36 and the cryogenic plate 38 are heated by the first cooling stage 30 and the second cooling stage 34 as heat sources, respectively. Furthermore, the purge gas supplied from the purge valve 20a to the cryogenic pump container 16 also participates in the heating of the cryogenic pump 10. Alternatively, a heating device such as an electric heater may be provided on the cryogenic pump 10. For example, an electric heater capable of being independently controlled from the operation of the refrigerator 14 may be installed on the first cooling stage 30 and / or the second cooling stage 34 of the refrigerator 14.

[0062] In the discharge process, the gas captured by the cryogenic pump 10 is re-vaporized or liquefied and discharged as a gas, liquid, or gas-liquid mixture along with the purge gas through the vent valve 22 or the roughing valve 18. In the cooling process, the cryogenic pump 10 is cooled again to the ultra-low temperature required for vacuum exhaust operation. If regeneration is complete, the cryogenic pump 10 can restart its exhaust operation.

[0063] Figure 2 This is a schematic diagram illustrating the cryogenic pump involved in the comparative example. (As shown...) Figure 2 As shown, in conventional cryogenic pumps, a relatively large space 150 is often ensured between the cryogenic pump inlet 117 (inlet cryogenic plate 137) and the top cryogenic plate 138. The top cryogenic plate 138 is directly mounted on the second cooling stage 134 of the refrigerator, or configured very close to the second cooling stage 134. Utilizing this relatively large space 150, second-type gases such as argon are captured onto the top cryogenic plate 138 by condensation, thereby enabling a large amount of second-type gases to be drawn into the cryogenic pump. Typically, a purge valve 120 is located near the cryogenic pump inlet 117, so purge gas is introduced from the purge valve 120 during regeneration, thereby enabling the large amount of second-type gases condensed on the top cryogenic plate 138 to be effectively vaporized and discharged. Such a design is commonly seen, for example, in cryogenic pumps used in physical vapor deposition (PVD) systems.

[0064] In contrast, the cryogenic pump 10 described in this embodiment does not form a large volume space near the cryogenic pump inlet 17; instead, multiple cryogenic plates 38 are compactly arranged. Each cryogenic plate 38 can adsorb non-condensable gases, thus enabling the cryogenic pump 10 to discharge non-condensable gases at high speed. The cryogenic pump 10 is suitable, for example, for vacuum exhaust in ion implantation devices.

[0065] Because multiple cryogenic plates 38 are configured, the total weight and even the heat capacity of the cryogenic plates 38 become relatively large. During regeneration, when the refrigerator 14 is used for reverse heating, the second cooling stage 34 becomes the heat source for the cryogenic plates 38. The heat transfer path from the distal end of the cryogenic plate 38 away from the second cooling stage 34 (e.g., the outer periphery of the cryogenic plate 38) becomes longer, making heating more difficult. The lower cryogenic plate 38b (especially the bottom cryogenic plate 38b1) is relatively large, so its weight and heat capacity become greater than other cryogenic plates 38, and because it is far from the second cooling stage 34, its heat transfer path is also long. If the purge gas is introduced from near the cryogenic pump inlet 17, which is far from the bottom cryogenic plate 38b1, as in conventional cryogenic pumps, the heating promotion effect of the bottom cryogenic plate 38b1 based on the purge gas may not be sufficient. The time required to heat the entire cryogenic plate 38 to the specified regeneration temperature depends on the heating time of the distal end of the lower cryogenic plate 38b away from the second cooling stage 34 (e.g., the outer periphery of the bottom cryogenic plate 38b1). If this heating time is delayed, it may result in an increase in regeneration time, which is undesirable.

[0066] According to the embodiment, the purge gas inlet 20 is positioned on the container body 16a at a lower position than the refrigerator housing 16b, thereby spraying purge gas towards the distal end of the cryogenic plate 38, which is away from the second cooling platform 34. The axial height of the purge valve 20a and the opening 20b is determined to spray a purge gas flow onto the outer periphery of the bottom cryogenic plate 38b1. The purge gas blown from the purge valve 20a passes through the opening 20b and is then sprayed onto the outer periphery of the bottom cryogenic plate 38b1. Through this optimization of the purge gas introduction, the heating of the cryogenic plate 38 (especially the bottom cryogenic plate 38b1) is promoted. The heating time of the cryogenic plate 38 can be shortened, thereby shortening the regeneration time.

[0067] Figure 3 This is a schematic diagram illustrating the cryogenic pump involved in Modification 1. Figure 3 The cryogenic pump 10 shown is Figure 1 The difference in cryogenic pump 10 lies in the shape of the lower cryogenic plate 38b. For example... Figure 3 As shown, each of the lower cryogenic plates 38b, including the bottom cryogenic plate 38b1, is configured to be parallel to a plane perpendicular to the axial direction (the direction of the cryogenic pump's central axis C). The lower cryogenic plates 38b are flat plates with a circular shape.

[0068] The purge gas inlet 20 is positioned below the refrigerator housing 16b on the container body 16a, thereby spraying purge gas toward the distal end of the cryogenic plate 38, which is away from the second cooling platform 34. In this embodiment, the purge valve 20a and opening 20b are positioned on the side of the container body 16a at an axial height corresponding to the bottom cryogenic plate 38b1. The axial height of the purge valve 20a and opening 20b is determined to spray a purge gas flow parallel to a plane perpendicular to the axial direction toward the bottom cryogenic plate 38b1. For example, the purge valve 20a and opening 20b are located at the same axial height as the outer periphery of the bottom cryogenic plate 38b1. The axial height of the purge valve 20a and opening 20b is determined to spray a purge gas flow between the bottom cryogenic plate 38b1 and the lower cryogenic plate 38b directly above and adjacent to the bottom cryogenic plate 38b1. For ease of understanding, in Figure 3 The arrows in the diagram indicate the purge gas flow that is sprayed from the purge gas inlet 20 to the bottom cryogenic plate 38b1.

[0069] This also promotes the heating of the low-temperature plate 38 (especially the bottom low-temperature plate 38b1). It can shorten the heating time of the low-temperature plate 38, thereby shortening the regeneration time.

[0070] Figure 4 Figures (a) and (b) are schematic representations of the cryogenic pump involved in Modification 2. Figure 4 The cryogenic pump 10 shown is Figure 1 The difference in cryogenic pump 10 lies in the configuration of the cryogenic plate 38. Similar to the embodiment described above, this cryogenic pump 10 is also a horizontal cryogenic pump.

[0071] like Figure 4 As shown in (a), multiple low-temperature plates 38 extend axially from top to bottom relative to the second cooling stage 34 of the refrigerator 14. Figure 4 As shown in (b), these cryogenic plates 38 are arranged radially when viewed from the cryogenic pump inlet 17. To increase the exhaust velocity and adsorption capacity of the gas (e.g., non-condensable gas), the cryogenic plates 38 are arranged relatively compactly. There may be at least four, at least eight, or at least sixteen cryogenic plates 38 arranged radially. Each cryogenic plate 38 is mounted on a cryogenic plate mounting member 42, a flat plate (e.g., circular plate) arranged perpendicular to the axial direction, and is thermally connected to the second cooling stage 34 via the cryogenic plate mounting member 42.

[0072] Compared to the upper portion of the cryogenic plate 38 located between the second cooling platform 34 and the cryogenic pump inlet 17, the lower portion of the cryogenic plate 38 located between the second cooling platform 34 and the bottom of the container body 16a has a larger space. When the axial distance La from the upper end of the cryogenic plate 38 to the upper surface of the second cooling platform 34 is set to 1, the axial distance Lb from the lower end of the cryogenic plate 38 to the upper surface of the second cooling platform 34 can be in the range of 1 to 3 or 1 to 2. That is, it can be La ≤ Lb ≤ 3La (or 2La).

[0073] The purge gas inlet 20 is positioned below the refrigerator housing 16b on the container body 16a, thereby spraying purge gas toward the distal end of the cryogenic plate 38, which is away from the second cooling platform 34. In this embodiment, the purge valve 20a and opening 20b are positioned on the side of the container body 16a at an axial height corresponding to the lower part (e.g., the lower end) of the cryogenic plate 38. For ease of understanding, in Figure 4 In diagram (a), the arrows schematically indicate the purge gas flow from the purge gas inlet 20 to the lower part of the cryogenic plate 38. This also promotes the heating of the cryogenic plate 38, shortening the heating time of the cryogenic plate 38 and consequently reducing the regeneration time.

[0074] Figure 5 Figures (a) to (c) are schematic illustrations of examples of purge gas diffusion components applicable to the cryogenic pumps involved in the embodiments. Figure 5 As shown in (a), the purge gas inlet 20 may also include a purge gas diffusion component 44 provided at the outlet or opening 20b of the purge valve 20a. Figure 5 As shown in (b), the purge gas diffusion component 44 may also include vortex vanes. The vortex vanes themselves are fixed vanes fixedly mounted on the purge valve 20a, which generate vortices in the passing purge gas. By providing the purge gas diffusion component 44, the high-speed purge gas flow blown out from the purge valve 20a can be diffused, allowing it to contact a wider area of ​​the cryogenic plate 38, thereby promoting the heating of the cryogenic plate 38.

[0075] like Figure 5 As shown in (c), the purge gas diffusion component 44 may also have a cone (e.g., a conical shape) disposed at the outlet of the purge valve 20a toward the apex. This allows the high-speed purge gas flow blown out from the purge valve 20a to diffuse as well.

[0076] The present invention has been described above with reference to the embodiments. The present invention is not limited to the above-described embodiments. Those skilled in the art should understand that the present invention can be modified in various ways and various variations are possible, and such variations are also within the scope of the present invention.

[0077] The purge gas inlet 20 may also include a conduit for guiding purge gas from the purge valve 20a to the cryogenic plate 38. The conduit may pass through the radiation shield 36. The front end of the conduit may be positioned near the distal end of the cryogenic plate 38, thereby spraying the purge gas introduced from the purge valve 20a through the conduit to the distal end of the cryogenic plate 38.

[0078] Industrial availability

[0079] This invention can be applied to the field of cryogenic pumps.

[0080] Symbol Explanation

[0081] 10-Cryogenic pump, 14-Refrigerator, 16-Cryogenic pump container, 16a-Container body, 16b-Refrigerator housing, 17-Cryogenic pump inlet, 20-Purge gas inlet, 20a-Purge valve, 20b-Opening, 21-Purge gas source, 30-First cooling platform, 34-Second cooling platform, 36-Radiation shield, 38-Cryogenic plate, 38a-Upper cryogenic plate, 38a1-Top cryogenic plate, 38b-Lower cryogenic plate, 38b1-Bottom cryogenic plate, 44-Purge gas diffusion component.

Claims

1. A cryogenic pump, characterized in that, have: A cryogenic pump container has a container body that defines a cryogenic pump inlet and extends axially in a cylindrical shape from the cryogenic pump inlet, and a refrigeration unit housing connected to a side of the container body. A refrigeration unit is fixed to the refrigeration unit housing and extends within the cryogenic pump container in a direction perpendicular to the axial direction, and the refrigeration unit has a first cooling platform and a second cooling platform that cools to a temperature lower than that of the first cooling platform; Multiple low-temperature plates are thermally connected to the second cooling platform, and each low-temperature plate is capable of adsorbing non-condensable gases. The multiple low-temperature plates are arranged along the axial direction between the low-temperature pump inlet and the bottom of the container body, or are arranged radially when viewed from the low-temperature pump inlet. A radiation shield is disposed within the container body around the plurality of cryogenic plates and is thermally connected to the first cooling platform; and A purge gas inlet is positioned on the container body at a lower location than the refrigerator housing, thereby spraying purge gas toward the distal end of the low-temperature plate, which is away from the second cooling platform. The purge gas inlet includes a purge valve located on the side of the container body, positioned lower than the refrigeration unit housing, which connects the cryogenic pump container to the purge gas source. The radiation shield is provided with an opening that guides the purge gas ejected from the purge valve into the cryogenic pump container into the radiation shield. The opening is located on the front of the purge valve. The purge gas inlet is configured to spray a purge gas flow parallel to a plane perpendicular to the axial direction toward the distal end of the cryogenic plate.

2. The cryogenic pump according to claim 1, characterized in that, The plurality of cryogenic plates includes a plurality of lower cryogenic plates arranged along the axial direction between the second cooling platform and the bottom of the container body. The purge gas inlet is located on the side of the container body at an axial height corresponding to the lowest temperature plate furthest from the second cooling platform among the plurality of lower temperature plates.

3. The cryogenic pump according to claim 2, characterized in that, The lower low-temperature plate furthest from the second cooling platform is configured to be parallel to a plane perpendicular to the axial direction. The purge gas inlet is located on the side of the container body at an axial height that allows it to spray a purge gas flow parallel to a plane perpendicular to the axial direction onto the lower cryogenic plate furthest from the second cooling platform.

4. The cryogenic pump according to claim 2, characterized in that, The lower cryogenic plate furthest from the second cooling platform has an outer periphery that is inclined relative to a plane perpendicular to the axial direction. The purge gas inlet is located on the side of the container body at an axial height determined to spray a purge gas flow onto the outer periphery of the lower cryogenic plate furthest from the second cooling platform.

5. The cryogenic pump according to any one of claims 2 to 4, characterized in that, The plurality of cryogenic plates includes a plurality of upper cryogenic plates arranged along the axial direction between the second cooling platform and the cryogenic pump inlet. When the axial distance from the upper cryogenic plate closest to the cryogenic pump inlet to the upper surface of the second cooling platform is denoted as La, and the axial distance from the lower cryogenic plate furthest from the second cooling platform to the upper surface of the second cooling platform is denoted as Lb, La≤Lb≤3La.

6. The cryogenic pump according to claim 5, characterized in that, The plurality of upper cryogenic plates are at least three upper cryogenic plates arranged along the axial direction between the upper surface of the second cooling platform and the cryogenic pump inlet.

7. The cryogenic pump according to claim 5, characterized in that, The plurality of lower cryogenic plates are at least five lower cryogenic plates arranged along the axial direction between the upper surface of the second cooling platform and the bottom of the container body.

8. The cryogenic pump according to claim 1, characterized in that, The plurality of cryogenic plates are arranged radially when viewed from the cryogenic pump inlet, and the plurality of cryogenic plates extend from above to below along the axial direction relative to the second cooling platform. The purge gas inlet is located on the side of the container body at an axial height corresponding to the lower part of the cryogenic plate disposed between the bottom of the second cooling platform and the container body.

9. The cryogenic pump according to claim 8, characterized in that, When the axial distance from the upper end of the plurality of low-temperature plates to the upper surface of the second cooling platform is denoted as La and the axial distance from the lower end of the plurality of low-temperature plates to the upper surface of the second cooling platform is denoted as Lb, La≤Lb≤3La.

10. The cryogenic pump according to claim 1, characterized in that, The purge gas inlet includes a purge gas diffusion component located at the outlet or opening of the purge valve.

11. The cryogenic pump according to claim 10, characterized in that, The purging gas diffusion component has vortex blades.

12. The cryogenic pump according to claim 1, characterized in that, When viewed from the inlet of the cryogenic pump, the purge gas inlet is located on the side of the container body on the same side as the refrigeration unit housing.

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