Dual Vacuum Seal

Abstract

A vacuum system includes a vacuum chamber wall, a vacuum chamber flange, an outer seal disposed between the wall and the flange, and an inner seal disposed between the wall and the flange. The outer seal includes a first material and the inner seal includes a second material different from the first material. The inner seal is closer to the interior of the vacuum chamber than the outer seal and is separated from the outer seal by a gap. The outer seal can provide a tighter wall-to-flange vacuum seal than the inner seal. The inner seal can be more resistant to gases used to clean the interior of the vacuum chamber than the outer seal. The vacuum system also includes a passageway connecting the gap to a first vacuum pump for evacuating the gap.

Description

[Technical field]

[0001] TECHNICAL FIELD This disclosure relates to vacuum systems, and more particularly to vacuum seals. [Background technology]

[0002] [Related Applications] This application claims priority to U.S. Provisional Patent Application No. 63 / 148,625, filed February 12, 2021, which is incorporated by reference in its entirety for all purposes.

[0003] In some vacuum systems, to establish a vacuum seal between a flange (e.g. door) and the wall of the vacuum chamber, O-rings made of the same material are placed in inner and outer grooves for the flange. Each of these O-rings can be called a seal. Evacuation of the gap separating the O-rings can reduce the pressure on the inner O-ring. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-099924 A [Patent Document 2] Japanese Patent Application Publication No. 9-263944 Summary of the Invention [Problem to be solved by the invention]

[0005] To be able to maintain a high vacuum in the vacuum chamber, the O-ring should exhibit only minor leakage and permeation. However, the O-ring should also be stable, for example, to exhibit resistance to the gases used to clean the inside of the vacuum chamber. Lack of resistance to the gases could cause degradation of the inner O-ring due to exposure to the gases, leading to particle emission and leakage from the inner O-ring into the vacuum chamber. These requirements can sometimes conflict. [Means for solving the problem]

[0006] In certain embodiments, a vacuum system includes a vacuum chamber wall, a vacuum chamber flange, an outer seal disposed between the wall and the flange, and an inner seal disposed between the wall and the flange. The outer seal includes a first material and the inner seal includes a second material different from the first material. The inner seal is closer to an interior of the vacuum chamber than the outer seal. The outer seal is separated from the inner seal by a gap. The outer seal provides a tighter wall-to-flange vacuum seal than the inner seal. The vacuum system also includes a passageway connecting the gap to a first vacuum pump for evacuating the gap.

[0007] In certain embodiments of the method, an outer seal and an inner seal are disposed between a wall of a vacuum chamber and a flange of the vacuum chamber. The outer seal comprises a first material and the inner seal comprises a second material different from the first material. The inner seal is closer to an interior of the vacuum chamber than the outer seal. The outer seal is separated from the inner seal by a gap. The outer seal provides a tighter wall-to-flange vacuum seal than the inner seal. The method also includes evacuating the gap using a first vacuum pump, and evacuating the interior of the vacuum chamber using a second vacuum pump while evacuating the gap using the first vacuum pump.

[0008] In certain embodiments, the vacuum system includes a vacuum chamber wall, a vacuum chamber flange, an outer seal disposed between the wall and the flange, and an inner seal disposed between the wall and the flange. The outer seal includes a first material and the inner seal includes a second material different from the first material. The inner seal is closer to the interior of the vacuum chamber than the outer seal. The outer seal is separated from the inner seal by a gap. The inner seal is more resistant to gases used to clean the interior of the vacuum chamber than the outer seal. The vacuum system also includes a passageway connecting the gap to a first vacuum pump for evacuating the gap.

[0009] For a better understanding of the various described embodiments, reference should be made to the following drawings in conjunction with the detailed description that follows. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a portion of a vacuum chamber according to certain embodiments. [Diagram 2] 2 is a cross-sectional view of a portion of a vacuum system including a vacuum chamber, a first vacuum pump, and a second vacuum pump of FIG. 1 in accordance with certain embodiments. [Diagram 3] 3 is a cross-sectional view of a portion of an example vacuum system of FIG. 2 according to certain embodiments. [Figure 4] 1 is a flow chart illustrating a method of operating a vacuum system according to certain embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Like reference numerals refer to corresponding parts throughout the drawings and specification.

[0012] Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the detailed description that follows, numerous specific details are set forth in order to provide a consistent understanding of the various described embodiments. However, it will be appreciated by those skilled in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

[0013] FIG. 1 illustrates a cross-sectional view of a portion of a vacuum chamber 100 according to certain embodiments. The vacuum chamber 100 includes a wall 102 and a flange 104 (for simplicity, only a portion of the wall 102 and flange 104 are shown in FIG. 1). The term flange, as used herein, refers to a cover for an opening in the vacuum chamber 100. For example, the flange 104 may be a door that can be opened and closed to allow materials to be placed in and removed from the vacuum chamber 100. For example, the flange 104 may be fixedly attached to the wall 102 but removable to allow maintenance to be performed on the vacuum chamber 100. The walls 102, flange 104, and / or other components (e.g., including other walls and / or flanges) of the vacuum chamber 100 enclose an interior 106 of the vacuum chamber 100. A vacuum (e.g., ultra-high vacuum (UHV)) is maintained within the vacuum chamber 100 (UHV is about 100 MPa). -9 (Vacuum is a standard and well-known technical term referring to a vacuum exhibiting a pressure on the order of less than 1000 torr.) Outside the vacuum chamber 100 may be atmosphere 108 (i.e., at atmospheric pressure).

[0014] As shown in the example of Figure 1, a portion of the flange 104 is adjacent to the wall 102. An outer seal 110 and an inner seal 112 (e.g., an outer gasket and an inner gasket) are disposed between the wall 102 and the flange 104 (i.e., between the wall 102 and the portion of the flange 104 adjacent to the wall 102) to provide a vacuum seal. In certain embodiments, the outer seal 110 and / or the inner seal 112 are disposed in separate grooves in the surface of the wall 102 adjacent to the flange 104, as shown in Figure 1. In other embodiments, the outer seal 110 and / or the inner seal 112 are disposed in separate grooves in the surface of the flange 104 adjacent to the wall 102. In further embodiments, the outer seal 110 and / or the inner seal 112 are disposed in respective pairs of grooves in the wall 102 and the flange 104 such that both the wall 102 and the flange 104 have grooves in which the outer seal 110 and / or the inner seal 112 are seated. Thus, at least one of the wall 102 and the flange 104 can be provided with a first groove in which the outer seal 110 is seated and a second groove in which the inner seal 112 is seated. The inner seal 112 is closer to the interior 106 of the vacuum chamber 100 than the outer seal 110. For example, the outer seal 110 and the inner seal 112 are disposed concentrically between the wall 102 and the flange 104 (e.g., disposed in their respective grooves), with the outer seal 110 having a larger equivalent diameter (i.e., overall length) than the inner seal 112. An outer seal 110 and an inner seal 112 are disposed between the wall 102 and the flange 104 and are compressed.

[0015] The outer seal 110 and the inner seal 112 are separated from each other by a gap 114. The gap 114 is located between the flange 104 and the wall 102 and between the inner seal 112 and the outer seal 110. A passage 116 leads out from the gap 114 so that the gap 114 can be coupled to a first vacuum pump that evacuates the gap 114 (and the passage 116). The passage 116 can be through the wall 102 (e.g., as shown in FIG. 1 ) or through the flange 104. In certain embodiments, the vacuum achieved in the gap 114 has a higher pressure (i.e., a lower vacuum) than the vacuum achieved in the interior 106 of the vacuum chamber 100. For example, if the vacuum achieved in the gap 114 is a lower vacuum (i.e., a lower pressure), the gap 114 may be evacuated from the wall 102 by a vacuum pump. -3 torr or more), while the pressure related to the vacuum in the inside 106 is 10 -3 torr (eg, UHV). By evacuating the gap 114, the pressure difference between the gap 114 and the interior 106 of the vacuum chamber 100 is reduced, thereby reducing the pressure on the inner seal 112.

[0016] The outer seal 110 provides a tighter vacuum seal between the wall 102 and the flange 104 (i.e., a better seal with less leakage through the seal) than the inner seal 112. The outer seal 110 includes (e.g., is made of) a first material. The inner seal 112 includes (e.g., is made of) a second material that is different from the first material. In certain embodiments, the second material is harder than the first material, causing the inner seal 112 to be harder than the outer seal 110. The outer seal 110 being less stiff than the inner seal 112 allows the outer seal 110 to form a tighter fit against the wall 102 and flange 104 than the inner seal 112, and therefore provides a tighter vacuum seal between the wall 102 and the flange 104 than the inner seal 112.

[0017] In certain embodiments, both the outer seal 110 and the inner seal 112 are elastomeric seals (e.g., O-rings) and the first material and the second material are separate elastomers. That is, the inner seal 112 can be an inner elastomeric seal (e.g., an inner O-ring) and the outer seal 110 can be an outer elastomeric seal (e.g., an outer O-ring). The second material (i.e., the elastomer comprising the inner seal 112) can be harder than the first material (i.e., the elastomer comprising the outer seal 110). For example, the first material can be a fluoroelastomer (i.e., FKM / FPM) (e.g., sold under the trademark VITON®) and the second material can be a perfluoroelastomer (i.e., FFKM) (e.g., sold under the trademark PERFREZ®). Perfluoroelastomers are harder than fluoroelastomers, and the fluoroelastomer seals provide a tighter vacuum seal than perfluoroelastomer seals.

[0018] From time to time (e.g., periodically), the interior 106 of the vacuum chamber 100 can be cleaned by introducing a gas into the interior 106. In certain embodiments, the gas is a reducing gas (or contains such a gas). For example, the gas is ozone or atomic oxygen (or contains such a gas). During this cleaning process, the interior 106 of the vacuum chamber 100 is not at a vacuum, which is maintained in the interior 106 during operation of the vacuum chamber 100, due to the high partial pressure of the gas. After the cleaning process is completed, the interior 106 is pumped back to the operational vacuum level (e.g., UHV) and operation of the vacuum chamber 100 is resumed.

[0019] The inner seal 112 is more resistant (i.e., more resistant to chemical and / or physical changes caused by) the gases (e.g., ozone or atomic oxygen) used to clean the interior 106 of the vacuum chamber 100 than the outer seal 110. This resistance is achieved, for example, because the inner seal 112 is harder than the outer seal 110. In certain embodiments, the inner seal 112 is an elastomeric seal (e.g., an O-ring) that is more resistant to the gases than the outer seal 110, which is also an elastomeric seal (e.g., an O-ring). For example, the inner seal 112 is a perfluoroelastomer and the outer seal 110 is a fluoroelastomer; the perfluoroelastomer is more resistant to the vacuum chamber cleaning gases than the fluoroelastomer. The increased gas resistance of the inner seal 112 reduces degradation of the inner seal 112 due to exposure to the gas, thereby reducing particle shedding from the inner seal 112 into the interior 106 of the vacuum chamber 100 and leakage through the inner seal 112 caused by degradation of the inner seal 112. Such particles may contaminate the interior 106 (e.g., components disposed in the interior 106, such as optical systems). Thus, increasing the gas resistance of the inner seal 112 reduces contamination of the interior 106 of the vacuum chamber (e.g., contamination of components disposed in the interior 106).

[0020] In certain embodiments, the outer seal 110 and the inner seal 112 are operated under static conditions where the position of the flange 104 relative to the wall 102 is stationary during operation of the vacuum chamber 100. Alternatively, the outer seal 110 and the inner seal 112 may be operated under dynamic conditions to allow the flange 104 to move relative to the wall 102 during operation of the vacuum chamber 100. For example, the flange 104 may move relative to the wall 102 for self-alignment and maintain its alignment relative to the vacuum chamber 100. The outer seal 110 and the inner seal 112 may accommodate movement of the flange 104 relative to the wall 102 while collectively maintaining a vacuum seal between the wall 102 and the flange 104: the cooperation of the outer seal 110 and the inner seal 112 maintains the vacuum seal despite movement of the flange 104.

[0021] 2 is a cross-sectional view of a portion of a vacuum system 200 including the vacuum chamber 100 (FIG. 1), a first vacuum pump 118, and a second vacuum pump 122, according to certain embodiments. The first vacuum pump 118 is coupled to the gap 114 via a passage 116 and may be used to evacuate the gap 114 and thus provide a vacuum within the gap 114. For example, the first vacuum pump 118 is coupled to the gap 114 via a passage 116 by a tube 120 that couples the first vacuum pump 118 to the passage 116 (also, the tube 120 may be considered part of the passage 116). In certain embodiments, the first vacuum pump 118 is a roughing pump that provides a rough vacuum within the gap 114.

[0022] The second vacuum pump 122 is used to provide a vacuum in the interior 106 of the vacuum chamber 100. The second vacuum pump 122 may provide that vacuum alone or in cooperation with one or more other vacuum pumps. A separate roughing pump may be used initially (e.g., through a connection of the first vacuum pump 118 to the interior 106, not shown in FIG. 2) to pump the interior 106 to a rough vacuum and then, either alone or in cooperation with one or more other vacuum pumps, to pump the interior to a higher vacuum (e.g., UHV). Examples of the second vacuum pump 122 include, but are not limited to, a turbopump or a cryopump. In certain embodiments, the second vacuum pump 122 is used to provide a higher (i.e., lower pressure) vacuum in the interior 106 than is provided or can be provided in the gap 114 by the first vacuum pump 118. For example, the second vacuum pump 122 may be a UHV pump, while the first vacuum pump 118 may not be capable of providing an ultra-high vacuum within the gap 114 (e.g., the first vacuum pump 118 may be a roughing pump that provides a rough vacuum within the gap 114).

[0023] 3 is a cross-sectional view of a portion of vacuum system 300, which is an example of vacuum system 200 (FIG. 2) according to certain embodiments. In vacuum system 300, first vacuum pump 118 is coupled to second vacuum pump 122, which can evacuate second vacuum pump 122. For example, tube 124 couples the exhaust of second vacuum pump 122 to first vacuum pump 118. Tube 124 can also be connected to tube 120.

[0024] A vacuum system having a vacuum chamber 100 (e.g., vacuum system 200 of FIG. 2, e.g., vacuum system 300 of FIG. 3) can be used in a wide variety of applications. In certain embodiments, the vacuum chamber 100 is used in a metrology or inspection tool (e.g., a semiconductor metrology or inspection tool). For example, the vacuum chamber 100 can be used in a tool that inspects reticles (i.e., photomasks) or semiconductor wafers for defects. The vacuum chamber 100 can have optics in its interior 106 that are cleaned when a gas is used to clean the interior 106. The optics can be extreme ultraviolet (EUV) optics (e.g., 13.5 nm optics). Many other examples are possible.

[0025] FIG. 4 is a flow chart illustrating a method 400 of operating a vacuum system (e.g., vacuum system 200 of FIG. 2, e.g., vacuum system 300 of FIG. 3) according to certain embodiments. In the method 400, an outer seal (e.g., outer seal 110 of FIGS. 1-3) and an inner seal (e.g., inner seal 112 of FIGS. 1-3) are disposed (402) between a wall (e.g., wall 102 of FIGS. 1-3) of a vacuum chamber (e.g., vacuum chamber 100 of FIG. 103) and a flange (e.g., flange 104 of FIGS. 1-3) of the vacuum chamber. The outer seal is of a first material. The inner seal is of a second material, different from the first material. The inner seal and the outer seal are disposed such that the inner seal is closer to an interior of the vacuum chamber (e.g., interior 106 of FIGS. 1-3) than the outer seal. The outer seal is separated from the inner seal by a gap (e.g., gap 114 of FIGS. 1-3). In some embodiments, the outer seal provides a tighter wall-to-flange vacuum seal than the inner seal 404. In some embodiments, the inner seal is harder than the outer seal and the second material is harder than the first material 406. For example, the outer seal may provide a tighter wall-to-flange vacuum seal than the inner seal because the outer seal is not as hard and therefore may form a better fit with the wall and flange.

[0026] In some embodiments, the inner and outer seals are elastomeric seals (e.g., O-rings) and the first and second materials are distinct elastomers (408). The second material (i.e., the material of the inner elastomeric seal) can be harder than the first material (i.e., the material of the outer elastomeric seal), making the inner elastomeric seal harder than the outer elastomeric seal. For example, the first material can be a fluoroelastomer and the second material can be a perfluoroelastomer.

[0027] The gap is evacuated (410) using a first vacuum pump (e.g., first vacuum pump 118 of FIGS. 2-3) (e.g., a turbopump or a cryopump). That is, a vacuum is created in the gap by the first vacuum pump. While the gap is being evacuated (i.e., while the first vacuum pump is being used to create a vacuum in the gap), the interior of the vacuum chamber is evacuated (414) using a second vacuum pump (e.g., second vacuum pump 122 of FIGS. 2-3). For example, an ultra-high vacuum is created in the vacuum chamber (416) while a pressure higher than an ultra-high vacuum is created in the gap (412). The second vacuum pump creates a vacuum in the vacuum chamber by itself or in cooperation with one or more other pumps (e.g., one or more other turbopumps or cryopumps).

[0028] External and internal seals can be used to accommodate movement of the flange relative to the wall while maintaining a wall-to-flange vacuum seal. Such movement can occur, for example, to allow the flange to self-align. Such movement and accommodation by the external and internal seals can occur while the gap is being evacuated using a first vacuum pump and the interior of the vacuum chamber is being evacuated using a second vacuum pump. Alternatively, the flange is held stationary relative to the wall while the gap is being evacuated using a first vacuum pump and the interior of the vacuum chamber is being evacuated using a second vacuum pump.

[0029] The vacuum chamber may require cleaning (e.g., periodic cleaning). Thus, the method 400 may further include ceasing (418) evacuation of the interior of the vacuum chamber. After evacuation of the interior of the vacuum chamber has ceased, the interior of the vacuum chamber is cleaned (420) with a gas (e.g., a reducing gas). In certain embodiments, the gas is ozone or atomic oxygen (or contains the same). The inner seal may be more resistant to the gas than the outer seal (422). After the interior of the vacuum chamber has been cleaned, evacuation of the interior of the vacuum chamber is resumed (424) with the second vacuum pump, and the method 400 returns to steps 410 and 414. Alternatively, the method 400 may return to step 402 after step 424. In this manner, the vacuum chamber may be cleaned repeatedly, with each cleaning occurring after a separate cycle of use.

[0030] The above description is for illustrative purposes and has been described with reference to specific embodiments. However, the above illustrative discussion is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. The embodiments have been selected to best explain the principles underlying the claims and their practical application, so that others skilled in the art can best utilize the embodiments with various modifications commensurate with the specific use envisioned.

Claims

1. 1. A vacuum system comprising: A wall of the vacuum chamber; a flange of the vacuum chamber; an outer seal disposed between the wall and the flange, the outer seal including a first material; an inner seal disposed between the wall and the flange, the inner seal including a second material different from the first material; Equipped with the inner seal is closer to an interior of the vacuum chamber than the outer seal; the outer seal is separated from the inner seal by a gap; and a vacuum system in which the outer seal provides a tighter vacuum seal between the wall and the flange than the inner seal; and a passageway connecting the gap to a first vacuum pump for evacuating the gap; Furthermore, the first vacuum pump coupled to the gap via the passage; a second vacuum pump for providing an ultra-high vacuum within the vacuum chamber; wherein the first vacuum pump is coupled to a second vacuum pump to evacuate the second vacuum pump.

2. 10. The vacuum system of claim 1, wherein the inner seal is more resistant to gases used to clean the interior of the vacuum chamber than the outer seal.

3. 3. The vacuum system of claim 2, wherein the gas comprises ozone.

4. 3. The vacuum system of claim 2, wherein the gas comprises atomic oxygen.

5. 2. The vacuum system of claim 1, wherein the inner seal is harder than the outer seal and the second material is harder than the first material.

6. 2. The vacuum system of claim 1, wherein said inner seal and said outer seal are elastomeric seals, and said first material and said second material are distinct elastomers.

7. 7. The vacuum system of claim 6, wherein the inner seal and the outer seal are O-rings.

8. 7. A vacuum system according to claim 6, comprising: the first material is a fluoroelastomer; and The vacuum system wherein the second material is a perfluoroelastomer.

9. 7. The vacuum system of claim 6, wherein the inner seal is harder than the outer seal and the second material is harder than the first material.

10. 2. The vacuum system of claim 1, the flange is configured to be movable relative to the wall during operation of the vacuum chamber; and A vacuum system in which the outer seal and the inner seal collectively maintain a vacuum seal between the wall and the flange while accommodating movement of the flange relative to the wall.

11. 2. The vacuum system of claim 1, wherein the flange is a door.

12. 2. The vacuum system of claim 1, wherein at least one of the flange and the wall has a first groove in which the outer seal seats and a second groove in which the inner seal seats.

13. 1. A method comprising: An outer seal and an inner seal are disposed between the wall of the vacuum chamber and a flange of the vacuum chamber, the outer seal comprises a first material; the inner seal comprises a second material different from the first material; the inner seal is closer to an interior of the vacuum chamber than the outer seal; the outer seal is separated from the inner seal by a gap; and the outer seal provides a tighter vacuum seal between the wall and the flange than the inner seal; evacuating the gap using a first vacuum pump; and While evacuating the gap with the first vacuum pump, an interior of the vacuum chamber is evacuated with a second vacuum pump, the first vacuum pump being coupled to a second vacuum pump for evacuating the second vacuum pump.

14. 14. The method of claim 13 further comprising: Stopping evacuation of the inside of the vacuum chamber; purging the interior of the vacuum chamber with a gas after evacuation of the interior of the vacuum chamber has ceased, the inner seal being more resistant to the gas than the outer seal; and After cleaning the interior of the vacuum chamber, re-evacuating the interior of the vacuum chamber with the second vacuum pump.

15. 15. The method of claim 14, wherein the gas comprises ozone or atomic oxygen.

16. 14. The method of claim 13, wherein the inner seal is harder than the outer seal and the second material is harder than the first material.

17. 14. The method of claim 13, wherein the inner seal and the outer seal are elastomeric seals, and the first material and the second material are distinct elastomers.

18. 20. The method of claim 17, wherein the inner seal and the outer seal are O-rings.

19. 20. The method of claim 17, the first material is a fluoroelastomer; and The method wherein said second material is a perfluoroelastomer.

20. 18. The method of claim 17, wherein the inner seal is harder than the outer seal and the second material is harder than the first material.

21. 14. The method of claim 13, providing an ultra-high vacuum within the vacuum chamber when evacuating the interior of the vacuum chamber using the second vacuum pump; and The method of providing a vacuum having a pressure greater than ultra-high vacuum in the gap when evacuating the gap with the first vacuum pump.

22. 14. The method of claim 13, further comprising, while evacuating the gap with the first vacuum pump and evacuating the interior of the vacuum chamber with the second vacuum pump: A method using the outer seal and the inner seal to accommodate movement of the flange relative to the wall while maintaining a vacuum seal between the wall and the flange.

23. 1. A vacuum system comprising: A wall of the vacuum chamber; a flange of the vacuum chamber; an outer seal disposed between the wall and the flange, the outer seal including a first material; an inner seal disposed between the wall and the flange, the inner seal including a second material different from the first material; Equipped with the inner seal is closer to an interior of the vacuum chamber than the outer seal; the outer seal is separated from the inner seal by a gap; and a vacuum system in which the inner seal is more resistant to gases used to clean the interior of the vacuum chamber than the outer seal; and a passageway connecting the gap to a first vacuum pump for evacuating the gap; a second vacuum pump for providing an ultra-high vacuum within the vacuum chamber; wherein the first vacuum pump is coupled to a second vacuum pump to evacuate the second vacuum pump.

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