Cryogenic pump

Abstract

A cryopump having a pump inlet, a two-stage refrigerator, a first-stage array arranged to be thermally coupled to a first stage of the two-stage refrigerator, and a cryopanel structure coupled to a second stage of the two-stage refrigerator. A surface of the cryopanel structure has a coated portion coated with a sorbent material and other portions not coated with the sorbent material.

Description

Technical Field

[0001] The field of the present invention relates to cryogenic pumps, and more particularly to two-stage cryogenic pumps having a first stage for capturing Class I gases such as water vapor at a temperature, and a second stage for capturing Class II gases such as nitrogen at a lower temperature, and in some embodiments for cryogenic adsorption of Class III gases such as hydrogen. Background Technology

[0002] The two-stage cryogenic pump is formed by a second-stage cryogenic panel array. It can operate in the range of 4-25 K and can be coated with a trapping material such as biochar. This cryogenic panel array acts as the main pumping surface and is surrounded by a first-stage radiation barrier that operates in a higher temperature range, such as 40-130 K, and provides radiation shielding to the lower-temperature array by trapping gas molecules, such as water vapor, where they come into contact with the array, thus protecting the array from the effects of these gases.

[0003] During operation, as gas enters the pump container through the inlet, at least some Class I gases (such as water vapor) condense on the front array, which forms part of the first-stage radiation barrier. Lower-boiling-point gases pass through the front array and enter the volume within the radiation barrier. Class II gases (such as nitrogen) condense on the second-stage array, while Class III gases (such as hydrogen, helium, and neon), which have considerable vapor pressure at 4 K, are adsorbed by adsorbents (such as activated carbon, zeolite, or molecular sieves) coated on the second-stage cryogenic panel.

[0004] In this way, the gas entering the pump from the chamber is captured, and a vacuum is created within the pump container. One problem with cryogenic pumps is that their ability to capture gas molecules decreases during operation as the capture surface becomes saturated. Therefore, the cryogenic pump is periodically regenerated to release the captured gas molecules.

[0005] The goal is to provide a two-stage cryogenic pump with increased operating time between regeneration stages. Summary of the Invention

[0006] A first aspect provides a cryogenic pump comprising: a pump inlet; a two-stage refrigerator; a first-stage array thermally coupled to a first stage of the two-stage refrigerator; and a cryogenic panel structure coupled to a second stage of the two-stage refrigerator and comprising a plurality of cryogenic panels; wherein each of the plurality of cryogenic panels comprises two surfaces, the two surfaces comprising a coated surface coated with an adsorbent material and another surface uncoated with the adsorbent material; the first-stage array comprises a plurality of elements corresponding to the plurality of cryogenic panels; the plurality of elements are configured to be mounted between the pump inlet and the plurality of cryogenic panels; wherein each of the plurality of elements extends from a position between the corresponding cryogenic panel and the pump inlet toward an adjacent cryogenic panel and is inclined toward the inlet, such that each of the plurality of elements at least partially shields the coated surface of the adjacent cryogenic panel from direct impact of gas molecules passing through the pump inlet.

[0007] The inventors of this invention recognized that the problem with the adsorbent-coated surfaces in cryogenic pumps is that they can become less effective over time due to gas molecules adsorbing onto them. Adsorbent materials are provided to capture Class III gases, and it is important that these gases contact these surfaces and are captured. However, to increase the time between regeneration cycles, it would be desirable to inhibit any other gases from being captured by the adsorbent that might condense on other surfaces. Photoresist, for example, is a gas that may be present when the cryogenic pump is used to evacuate a semiconductor processing chamber, and it is adsorbed onto the adsorbent surface upon impact, thereby reducing the lifetime of the adsorbent surface between regeneration cycles.

[0008] The inventors of this invention recognized that if some surfaces of the second-stage cryogenic panel are not coated, and if a gas, such as a photoresist, first impacts these surfaces, the gas will condense on the uncoated surfaces before reaching the adsorbent-coated surfaces, and therefore, the lifetime of the adsorbent-coated surfaces will increase. Typically, pump designers strive to coat all surfaces of the cryogenic panel because this increases the area covered by the adsorbent and increases the pumping speed and the time between regenerations. However, pump design needs to consider the surface area coated with the adsorbent, as this reflects the amount of hydrogen that can be adsorbed and has safety implications.

[0009] Therefore, by providing some uncoated surfaces to the pump, non-Class III gases may condense upon impacting these uncoated adsorbent surfaces, while Class III gases will bounce off the uncoated surfaces and be adsorbed upon impacting the coated adsorbent surfaces. In this way, the adsorbent surface will primarily adsorb Class III gases, which will increase its efficiency and lifespan between regenerations. In effect, by allowing at least some gases to impact the uncoated surfaces, some gases (such as photoresist) will never reach the coated surfaces, and the coated surfaces will be protected from these gases and can be almost exclusively used for pumping Class III gases that will bounce off the uncoated surfaces, thus increasing the time between regenerations and providing a pump whose pumping speed does not excessively degrade over time.

[0010] Furthermore, by coating one side of the panel with an adsorbent and leaving the other side uncoated, an easy-to-manufacture device is provided. Additionally, the device is well-suited to providing one surface that might be struck by molecules entering the inlet and another surface shielded by the front array. In this regard, the elements of the first-stage array are arranged such that they at least partially shield the coated surface from the influence of molecules entering the inlet between the cryogenic panel and the inlet. The portion of the first-stage element closest to the corresponding cryogenic panel (side or edge) can be in approximately the same longitudinal plane as the cryogenic panel and can be angled such that it extends radially toward a radial position adjacent to the cryogenic panel. In this way, the element extends on one side (the coated side) of the cryogenic panel between the cryogenic panel and the inlet, thereby protecting the side from the influence of gas molecules entering through the inlet.

[0011] Because this pump has a reduced coated surface area compared to pumps with all low-temperature panel surfaces coated, the theoretical maximum amount of hydrogen that can be adsorbed by the surface is correspondingly reduced. Pumps have safety features associated with the maximum amount of hydrogen they can adsorb, so reducing this maximum makes these designed safety features less cumbersome. Although the theoretical maximum amount of hydrogen that can be adsorbed is reduced, because at least some non-Class III gases (such as photoresists) will condense on the bare surface rather than the adsorbent surface, the actual amount of hydrogen adsorbed by the pump during operation can be similar to that adsorbed by a pump with a fully coated surface.

[0012] Therefore, if only a subset of the surface is coated, an improved pump can be provided that does not excessively reduce the pumping speed over time.

[0013] Although the first-stage array can be at the same temperature as the second-stage array, in some embodiments the first-stage array is at a warmer (higher) temperature than the second-stage array and is configured to pump gases such as water vapor, while the second-stage array pumps gases such as nitrogen that condense at lower temperatures.

[0014] In some embodiments, the cryogenic panel structure is configured and mounted such that the surface of the cryogenic panel structure on which molecules entering the cryogenic pump are most likely to first impact is the other portion of the surface of the cryogenic panel structure.

[0015] In a low-temperature panel structure arranged such that the uncoated surface is most likely to be struck first by molecules entering the pump, molecules condensed on this structure (such as photoresist molecules) will never reach the absorbent surface. Class III gases will bounce off the bare surface and, if they later impact the coated surface, will be captured by the absorbent surface. In this way, the absorbent surface can be almost exclusively used to capture molecules that do not condense at these temperatures, and the effective lifetime of the absorbent surface will be increased.

[0016] In some embodiments, the first stage array and the cryogenic panel structure are configured such that there is no line-of-sight path between the pump inlet and the coated portion of the surface of the cryogenic panel.

[0017] Advantageously, the cryogenic panel structure can be arranged such that there is no line-of-sight path between the pump inlet and the coated portion of the surface, making it highly unlikely that the first surface that molecules entering the pump will impact is the coated structure of the cryogenic panel. Therefore, the coated structure will typically only receive molecules that have already impacted the uncoated surface, and in this way, it will be protected from gases such as photoresist that condense on the uncoated surface.

[0018] In some embodiments, the plurality of cryo panels include a plurality of planar cryopanels, one side of which includes the coated surface and the other side includes the other surface.

[0019] In other embodiments, the plurality of cryogenic panels includes a plurality of coaxial cylindrical cryogenic panels with different diameters.

[0020] In some embodiments, the outer surface of the cylindrical low-temperature panel includes the coated surface, and the inner surface includes the other surface.

[0021] The cryogenic panel structure can be planar. In some embodiments, the planar structure may have a coated surface and an uncoated surface. In other embodiments, the structure may be formed in a coaxial cylindrical arrangement. In some embodiments, the inner surface of the cylinder is an uncoated surface and the outer surface is a coated surface, and the cryogenic panel is arranged such that gaseous molecules entering the pump inlet impact the inner surface and bounce off where they are not condensed, striking the outward-facing surface of the coaxial cylinder.

[0022] In some embodiments, when viewed through the inlet, the plurality of elements are configured to overlap such that gas molecules will strike one of the elements before impacting the cryogenic panel structure. The arrangement of the elements allows gas molecules bouncing off the elements to be directed toward the uncoated surface, thereby providing further protection to the coated surface.

[0023] In some embodiments, the plurality of elements of the first-level array comprises a plurality of coaxial truncated conical elements with different diameters.

[0024] In the case of cryogenic panel structures including cylindrical elements, one arrangement of the first-stage array provides particularly effective protection for one surface of the cylinder. Furthermore, this arrangement is well-suited for circular pump inlets.

[0025] In some embodiments, the adsorbent material is configured to adsorb Class III gases, such as hydrogen, helium, and neon.

[0026] In some embodiments, the adsorbent material comprises a molecular sieve coated on the coated surface.

[0027] In some embodiments, the adsorbent material includes one of the following: biochar, activated carbon, zeolite, or porous metal surface.

[0028] The absorbent material can be a metal; in some embodiments, a porous metal that can be sprayed onto a surface, such as aluminum sponge, can be used. Aluminum sponge has a porosity of over 90%.

[0029] Other particular and preferred aspects are set forth in the appended independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims, as appropriate and in combinations other than those expressly set forth in the claims.

[0030] When a device feature is described as operable to provide a function, it will be understood that this includes device features that provide said function or are adapted or configured to provide said function. Attached Figure Description

[0031] Embodiments of the invention will now be described further with reference to the accompanying drawings, in which:

[0032] Figure 1 The cryogenic panel structure passing through the second-stage array of a cryogenic pump in one embodiment and a cross-section of the front array are shown;

[0033] Figure 2 Show Figure 1 The low-temperature panel and front array structure are cross-sections from different angles;

[0034] Figure 3 A planar low-temperature panel structure according to another embodiment is shown; and

[0035] Figure 4 The front array and Figure 3 Low-temperature panel structure. Detailed Implementation

[0036] Before discussing any embodiments in more detail, an overview will be provided first.

[0037] A second-stage low-temperature panel structure is provided, wherein an adsorbent such as biochar is coated on the surface of one side of the panel to collect hydrogen, while the other side has no adsorbent and will collect other molecules, such as photoresist that condenses at the low temperature of the low-temperature panel.

[0038] In some embodiments, a front array comprising several elements at a relatively high temperature (approximately 80 K) is present, the elements being configured to overlap when viewed through the pump inlet. The amount of overlap will determine the maximum hydrogen pumping rate. In this respect, large overlap will impede gas flow and reduce the pumping rate of gases not pumped by the front array; however, this will protect the secondary array and increase its lifespan between regenerations.

[0039] This cryogenic pump will also be particularly effective for pumping gases from semiconductor processing applications such as implantation and PVD (physical vapor deposition).

[0040] The embodiments provide a planar and circular solution. Conventionally, the front array structure is circular because the pump inlet and the interface to the vacuum chamber are circular. The planar front array, including parallel tilted panels, allows the second-stage structure to be aligned with the front array, and this can provide very high hydrogen pumping rates. The disadvantage is that the full area of ​​the inlet may not be effectively utilized.

[0041] A circular frontal array better accommodates the pump's circular inlet and vacuum chamber interface. To provide effective shielding of the cryogenic panel structure's surfaces via the circular frontal array, cylindrical cryogenic panels can be used. The circular frontal array can advantageously be formed from overlapping truncated conical elements. The inner surfaces of the cylindrical cryogenic panels may be exposed, and molecules deflected by these surfaces will impact the coated outer surfaces of the adjacent coaxial cylindrical structure. This will result in a pump that does not degrade its pumping speed over time, or at least exhibits a reduced degradation over time.

[0042] Figure 1 A coaxial second-stage cylindrical cryogenic panel structure 20 according to one embodiment is shown, which is shielded by a first-stage or front array 10. The front array 10 includes a plurality of coaxial frustoconical elements 12, which overlap when viewed through the pump inlet 5.

[0043] Multiple elements 12 forming a frontal array are thermally connected to the first-stage refrigerator of the cryogenic pump and maintained at a first-stage temperature in the range of 40-130K. The upper surfaces of the frontal array elements 12 facing the pump inlet 5 are inclined, and molecules striking these surfaces will be captured if they condense at the temperature of the first-stage refrigerator, or will be deflected toward the lower surfaces of adjacent external elements. The paths between the elements 12 of the first-stage array leading to the pump toward the second-stage cryogenic panel structure are angled toward the inner surface of the cylindrical cryogenic panel. Therefore, molecules traveling along these paths will preferably impact the inner surface 22 of the cylindrical elements of the cryogenic panel structure when they reach it. If the molecules are gases such as nitrogen or photoresist that condense at the temperature of the second-stage array (i.e., between 4-25K), the molecules will follow the trajectory indicated by arrow 9 and be captured by the inner surface 22. If the molecule is a Class III gas molecule that does not condense at the second temperature, the molecule will follow the trajectory shown by arrow 7 and be deflected by the inner surface 22 of the cylindrical low-temperature panel element toward the outer surface 24 of the adjacent inner cylindrical element, and will be captured by the adsorbent surface coated on the inner surface 24.

[0044] In this way, the inner surface 24 of the coaxial cylindrical second-stage cryogenic panel element is shielded from the influence of gas molecules other than Class III gas molecules, and thus the long-term effectiveness of the cryogenic panel structure is improved, and the pumping speed is not excessively degraded due to the adsorption of molecules such as photoresist.

[0045] Figure 2 The same cryogenic panel structure is shown from different angles. Here, it can be seen more clearly that the truncated conical element 12 of the first-stage array 10 extends above the coaxial cylindrical element 25 that forms the second-stage cryogenic panel structure.

[0046] Figure 3 and Figure 4 An alternative embodiment is shown, in which both arrays are planar and each is formed from a plurality of planar elements. The cryogenic panel structure has parallel panels, one side of which is coated with an adsorbent while the other side is uncoated. The front array includes inclined elements extending from the elements of the second-stage array and tilted toward the pump inlet. In this way, it protects the coated surface from the initial impact of molecules entering through the pump inlet.

[0047] Figure 3 A parallel planar element 25 of a second-stage cryogenic panel structure within a pump with inlet 5 is shown. The first-stage front array is not shown.

[0048] Figure 4 The front array element 12 is schematically shown relative to the second-stage array element 25 and the pump inlet 5. As can be seen, element 12 is mounted between the pump inlet 5 and the cryogenic panel structure of the second-stage array. When viewed from the pump inlet 5, element 12 is tilted such that they overlap, and as for Figure 1 and Figure 2 In this embodiment, the path between the front array elements 12 leads to the exposed surface 22 of the cryogenic panel structure, such that molecules entering through the pump inlet are directed to this uncoated surface. Therefore, any molecules that initially impact the exposed surface 22 and condense at the temperature of the second-stage refrigerator are captured. Other Class III molecules bounce off surface 22 toward the coated surface 24, where they are captured by the adsorbent coating upon impact. In this way, the coated surface of the second-stage element is shielded from the initial impact of molecules entering the pump by the tilted first-stage array elements. Molecules that do not condense on either the first or second-stage array will impact the coated surface and be captured by the adsorbent.

[0049] While illustrative embodiments of the invention have been disclosed in detail herein with reference to the accompanying drawings, it should be understood that the invention is not limited to the precise embodiments described, and that various changes and modifications may be made herein without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0050] Figure Labels

[0051] 5. Pump inlet

[0052] 7. Hydrogen molecule trajectory

[0053] 9. Molecular trajectory of photoresist

[0054] 10 First-level array

[0055] 12 First-stage array elements

[0056] 20 Low-temperature panel structure

[0057] 22 Uncoated surfaces

[0058] 24. Surface coated with adsorbent

[0059] 25 Low-Temperature Panel Components

Claims

1. A cryogenic pump, comprising: Pump inlet; Two-stage refrigeration unit; The first-stage array is thermally coupled to the first stage of the two-stage refrigerator; as well as A low-temperature panel structure, which is coupled to the second stage of the two-stage refrigerator and includes multiple low-temperature panels; in Each of the plurality of low-temperature panels includes two sides, the two sides including a coated side coated with an adsorbent material and a side not coated with the adsorbent material; The first-level array includes multiple elements corresponding to the plurality of low-temperature panels; The plurality of components are configured to be installed between the pump inlet and the plurality of cryogenic panels; in Each of the plurality of elements extends from a position between the corresponding cryogenic panel and the pump inlet toward an adjacent cryogenic panel and is inclined toward the pump inlet, such that each of the plurality of elements at least partially shields the coated side of the adjacent cryogenic panel from direct impact of gas molecules passing through the pump inlet.

2. The cryogenic pump of claim 1, wherein the cryogenic panel structure is configured and mounted such that the surface of the cryogenic panel structure on which molecules entering the cryogenic pump are most likely to first impact is the other side of the cryogenic panel structure.

3. The cryogenic pump according to claim 1 or claim 2, wherein the first stage array and the cryogenic panel structure are configured such that there is no line-of-sight path between the pump inlet and the coated side of the side of the cryogenic panel.

4. The cryogenic pump according to claim 1 or claim 2, wherein the plurality of cryogenic panels comprises a plurality of planar cryogenic panels, one side of the cryogenic panel includes the coated side, and the other side includes the other side.

5. The cryogenic pump according to claim 1 or claim 2, wherein the plurality of cryogenic panels comprises a plurality of coaxial cylindrical cryogenic panels with different diameters.

6. The cryogenic pump of claim 5, wherein the outer surface of the cylindrical cryogenic panel includes the coated side, and the inner surface includes the other side.

7. The cryogenic pump of claim 5, wherein the plurality of elements of the first stage array comprises a plurality of coaxial truncated conical elements having different diameters.

8. The cryogenic pump according to claim 1 or claim 2, wherein the adsorbent material is configured to adsorb Class III gases.

9. The cryogenic pump according to claim 1 or claim 2, wherein the adsorbent material comprises a molecular sieve coated on the coated side.

10. The cryogenic pump according to claim 1 or claim 2, wherein the adsorbent material comprises one of the following: biochar, activated carbon, zeolite, or porous metal surface.

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