Coolant Micro-Leak Sensor for Vacuum Systems

Abstract

The system includes a vacuum chamber and a component disposed within the vacuum chamber that is heated during operation. The system also includes a cooling line mechanically coupled to the component and used to circulate a coolant to cool the component during operation. The system further includes a vacuum gauge used to measure the total pressure within the vacuum chamber and an analyzer used to measure the partial pressure within the vacuum chamber of a substance susceptible to leaking from the cooling line.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to cooling lines in vacuum systems, and more particularly to detecting coolant leaks from cooling lines. [Background technology]

[0002] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 071,373 (August 28, 2020), which is incorporated by reference in its entirety for all purposes.

[0003] Cooling lines within a vacuum chamber can develop microleaks, for example, as a result of stress from mechanical movement. If left undetected, the microleak can grow until it becomes a catastrophic leak. Damage from a catastrophic leak requires extensive repairs and causes long downtime. Monitoring the total vacuum pressure within the vacuum chamber using a vacuum gauge can be insufficient to identify a microleak in a cooling line because the vacuum gauge cannot distinguish the microleak from any other leaks or from sources of outgassing within the vacuum chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2010 / 0269911 [Patent Document 2] U.S. Patent Application Publication No. 2005 / 0211949 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, what is needed is a method and system for detecting coolant micro-leaks in vacuum systems so that the cooling lines can be repaired before a catastrophic leak occurs. [Means for solving the problem]

[0006] In some embodiments, a system includes a vacuum chamber and a component disposed within the vacuum chamber that heats during operation. The system also includes a cooling line mechanically coupled to the component for circulating a coolant to cool the component during operation. The system further includes a vacuum gauge for measuring the total pressure within the vacuum chamber and an analyzer for measuring the partial pressure within the vacuum chamber of a substance that may leak from the cooling line.

[0007] In some embodiments, a method includes operating a component disposed within a vacuum chamber. Operating the component causes heating. The method also includes circulating a coolant through a cooling line mechanically coupled to the component to cool the component. The method further includes measuring a total pressure within the vacuum chamber, measuring a partial pressure within the vacuum chamber of a substance that may leak from the cooling line, and determining whether the cooling line has a leak based on the partial pressure. [Brief explanation of the drawings]

[0008] For a better understanding of the various described implementations, please refer to the following detailed description in conjunction with the following drawings, in which like reference numerals refer to corresponding parts throughout the drawings and specification, and in which: [Figure 1A] FIG. 1 is a block diagram illustrating a vacuum system with cooling lines containing coolant and marker species, according to some embodiments. [Figure 1B] FIG. 1B is a block diagram illustrating an example of the vacuum system of FIG. 1A in which microcracks or fissures have formed in the cooling lines, according to some embodiments. [Figure 2A] FIG. 1 is a block diagram illustrating a vacuum system with cooling lines containing coolant without marker species, according to some embodiments. [Figure 2B]FIG. 2B is a block diagram illustrating an example of the vacuum system of FIG. 2A in which microcracks or fissures have formed in the cooling lines, according to some embodiments. [Figure 3] 1 is a flowchart illustrating a method for detecting a cooling line leak in a vacuum system, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0009] Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various embodiments being described. However, it will be apparent to those skilled in the art that the various embodiments described 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.

[0010] 1A is a block diagram illustrating a vacuum system 100 according to some embodiments. The vacuum system 100 includes a vacuum chamber 102. In some embodiments, the vacuum chamber 102 provides an ultra-high vacuum (UHV). -9 (V) is a standard, well-known technical term that refers to a vacuum having a pressure on the order of Torr or less. Vacuum system 100 may be a semiconductor inspection or metrology system. For example, vacuum system 100 may be a scanning electron microscope (SEM). The vacuum system may include EUV optics for semiconductor inspection or metrology (i.e., optics for 13.5 nm light). Alternatively, vacuum system 100 may have a different application.

[0011] Component 104 is disposed within vacuum chamber 102. Component 104 heats up during operation. For example, component 104 is an active component that consumes power and consequently heats up (as opposed to a passive component that does not consume power). In another example, component 104 is mechanically and thermally coupled, directly or indirectly, to an active component such that heating of the active component also heats component 104.

[0012] In some embodiments, component 104 is or includes a motor. Cooling lines 106 may be mechanically connected to the motor (e.g., to a motor coil within the motor) to cool the motor. The motor may be, for example, a stage motor that translates a stage disposed within vacuum chamber 102. The stage may have a chuck mounted thereon to support a substrate (e.g., a semiconductor wafer). The stage translates the chuck. Thus, operating the motor translates the stage, and thus the chuck and substrate, to a desired position.

[0013] In some embodiments, component 104 is or includes a digital camera. For example, the camera is used to image a substrate (e.g., a semiconductor wafer). Cooling line 106 can be mechanically connected to the digital camera to cool it.

[0014] In some embodiments, component 104 is or includes an electron optics system (e.g., a lens for electron optics, such as a magnetic lens). Cooling line 106 may be mechanically connected to the electron optics system (e.g., to the lens) to cool the electron optics system.

[0015] The cooling line 106 is mechanically (and thermally) coupled to the component 104. While the cooling line 106 is shown as a single loop in FIG. 1A , it may include a branching coolant manifold within the vacuum chamber 102. The coolant 108 circulates within the cooling line 106 during operation of the system 100, cooling the component 104. By cooling the component 104, the circulating coolant 108 also indirectly cools other components within the vacuum chamber 102 that would otherwise be heated by heat from the component 104. For example, if the vacuum chamber 102 includes an optical component (e.g., EUV optics) (e.g., electron optics such as a magnetic lens or other electron optical lens) thermally coupled to the component 104, the circulating coolant 108 indirectly cools the optical component.

[0016] In some embodiments, the vacuum system 100 includes a chiller 116 located outside the vacuum chamber 102. The cooling lines 102 extend from the vacuum chamber 102, through the chiller 116, and back into the vacuum chamber 102. The chiller 116 cools the coolant 108 that is turned off by the component 104 and thus carries heat away from the component 104.

[0017] The cooling lines 106 may be flexible to accommodate movement of the component 104 (e.g., movement of a motor). In some embodiments, the cooling lines 106 are made entirely or partially of a polymer. For example, the cooling lines 106 may be made entirely or partially of a flexible plastic. Alternatively, the cooling lines 106 are made entirely or partially of other materials, such as metal or elastomer.

[0018] In some embodiments, the coolant 108 is or includes ordinary water (HO). Ordinary water is different from heavy water. Both hydrogen atoms in an ordinary water molecule are normal hydrogen atoms with a single proton and no neutrons. Heavy water, on the other hand, includes deuterium oxide (DO), in which both hydrogen atoms in the molecule are deuterium atoms, and hydrogen-deuterium oxide (HDO), in which one hydrogen atom in the molecule is normal hydrogen and the other hydrogen atom is deuterium.

[0019] The vacuum system 100 includes a vacuum gauge 112 that measures the total pressure within the vacuum chamber 112. However, the vacuum gauge 112 may not be sensitive enough to detect microcracks or breaks 118 in the cooling lines 106. The microcracks or breaks 118 result in microleakage. The coolant 108 leaks from the cooling lines 106 through the microcracks or crevices 118, as shown in FIG. 1B. The microleak may not be large enough to increase the total pressure in the vacuum chamber 102 by an amount that indicates the presence of a microleak. By the time the vacuum gauge 112 is able to detect the leaking coolant 108, the microleak may have turned into a catastrophic leak that causes serious damage to the vacuum chamber 102 and / or the product (e.g., a substrate, such as a semiconductor wafer) within the vacuum chamber 102.

[0020] For example, if the coolant 108 is ordinary water, the water 108 leaking from the cooling line 106 may be only one of multiple sources of water vapor within the vacuum chamber 102. Water may also escape from elastomeric seals (e.g., O-rings) used to seal the vacuum chamber 102. Also, other substances besides water may be present within the vacuum chamber 102 at their respective partial pressures. The vacuum gauge 112 measures the total pressure within the vacuum chamber 102 and therefore cannot detect the extent to which water contributes to the total pressure (i.e., it cannot detect the partial pressure of water within the vacuum chamber 102). The vacuum gauge 112 also cannot detect the extent to which water comes from microcracks or fractures 118, as opposed to another source.

[0021] In some embodiments, to solve these problems, the cooling line 106 contains a marker species 110 in addition to the coolant 108. The marker species 110 circulates within the cooling line 106 along with the coolant 108. The marker species 110 are substances (e.g., molecules) that may leak from the cooling line 106 in the event of a microcrack or fracture 118, as shown in FIG. 1B. The marker species 110 can be selected to be characteristic of the composition of the residual gas within the vacuum chamber 102 (i.e., not present in the vacuum chamber 102 except in the event of a leak from the cooling line 106). The vacuum system 100 includes an analyzer 114 configured to measure the partial pressure of the marker species 110 within the vacuum chamber 102. The analyzer 114 can detect a microleak from a microcrack or fracture 118 before the microcrack or fracture 118 propagates or grows to the point where the vacuum gauge 112 can detect it (e.g., before a catastrophic failure occurs) because it measures the partial pressure of the marker species 110 as opposed to the total pressure of the vacuum chamber 102. As a comparison of the readings of the vacuum gauge 112 and the analyzer 114 in FIGS. 1A and 1B shows, the microcrack or fracture 118 causes a significantly greater increase in the partial pressure of the marker species 110 than the total pressure of the vacuum chamber 102. Detection of a microleak from a microcrack or fracture 118 can occur when the partial pressure of the marker species 110 meets a threshold value (e.g., exceeds, equals, or exceeds a particular value, or increases by at least or more than a particular amount). The analyzer 114 can be communicatively coupled to a computer system that generates a warning signal in response to detection of a microleak from a microcrack or fracture 118. The vacuum chamber 102 can then be taken offline in a controlled manner and the cooling line 106 repaired. In some embodiments, the analyzer 114 is a residual gas analyzer (RGA) (e.g., a mass spectrometer). In some embodiments, the analyzer 114 includes an infrared spectrometer that performs infrared spectroscopy (e.g., Fourier transform infrared spectroscopy (FTIR)).

[0022] In some embodiments, the marker species 110 is heavy water. For example, the coolant 108 is HO and D2O is added to the coolant 108 in the cooling line 106. The D2O reacts with the HO to produce HDO, which is the marker species 110. The analyzer 114 is configured to detect HDO.

[0023] In some embodiments, 1-propanol is added to the coolant 108 (e.g., which is HO) to provide the marker species 110. Thus, the marker species 110 corresponds to 1-propanol. The analyzer 114 is configured to detect a peak resulting from the addition of 1-propanol to the coolant 108 in the presence of microcracks or fractures 118.

[0024] The marker species 110 can be selected to be non-reactive with the coolant 108. Therefore, the marker species 110 are added to the coolant 108. Alternatively, a chemical that reacts with the coolant 108 to produce the marker species 110 is added to the coolant 108. The marker species 110 can be selected to have a specific heat capacity within ±50% of the specific heat capacity of the coolant to provide the desired cooling of the component 104. The marker species 110 may be chemically inert to avoid causing corrosion in the cooling lines 106 and chiller 116. The marker species 110 can have a vapor pressure within ±50% of the vapor pressure of the coolant 108, so that the marker species 110 and the coolant 108 have similar flow rates into the vacuum chamber 102 when microcracks or spalls 118 form.

[0025] In some embodiments, a coolant is used that is not otherwise present in the vacuum chamber 102 (i.e., is specific to the composition of the residual gas in the vacuum chamber 102) and therefore will not be present in the vacuum chamber 102 except in the case of a leak from the cooling line 106 (e.g., if microcracks or fractures 118 form on the cooling line 106). Such a coolant may be used without the marker species 110. FIGS. 2A and 2B show a vacuum system 200 using this type of coolant, according to some embodiments. In the vacuum system 200, the marker species 110 are not used and the coolant 108 is replaced with a coolant 202 that would not be present in the vacuum chamber 102 except in the case of a leak from the cooling line 106. In FIG. 2A, the cooling line 206 is intact, while FIG. 2B shows microcracks or fractures 118 formed on the cooling line 106. The analyzer 114 is configured to detect the coolant 202. Thus, the analyzer 114 can detect microcracks or fractures 118 (ie, detect microleaks resulting from the microcracks or fractures 118).

[0026] The coolant 202 may be a fluorocarbon-based fluid. For example, the coolant 202 may be a perfluorinated compound (PFC), such as those sold under the FLUORINERT® brand name. Alternatively, the coolant 202 may be a hydrofluoroether (HFE) compound or a fluroketone (FK) compound, such as those sold under the NOVEC® brand name.

[0027] 3 is a flowchart illustrating a method 300 for detecting a cooling line leak (e.g., a microleak from a microcrack or fracture 118) in a vacuum system (e.g., vacuum system 100, FIGS. 1A-1B; vacuum system 200 of FIGS. 2A-2B), according to some embodiments. Although the steps in method 300 are shown and described in a particular order, the steps may be performed in parallel. For example, all of the steps in method 300 may be performed simultaneously in an ongoing process.

[0028] In method 300, a component (e.g., component 104) disposed within a vacuum chamber (e.g., vacuum chamber 102) is actuated (302). Actuating the component causes heating (e.g., heating the component). In some embodiments, operating the component includes operating a motor (304) disposed within the vacuum chamber. For example, the motor is actuated to translate a stage to which a chuck is attached. The chuck supports a substrate (e.g., a semiconductor wafer). In some other embodiments, operating the component includes operating a digital camera disposed within the vacuum chamber and / or operating an electron-optical system (e.g., a magnetic lens or other electron-optical lens) disposed within the vacuum chamber.

[0029] To cool the components, a coolant (e.g., coolant 108, FIGS. 1A-1B; coolant 202, FIGS. 2A-2B) is circulated (306) through cooling lines (e.g., cooling line 106) that are mechanically coupled to the components. In some embodiments, the coolant (e.g., coolant 108, FIGS. 1A-1B) typically comprises water (308). Alternatively, the coolant (e.g., coolant 202, FIGS. 2A-2B) may be a fluorocarbon-based fluid (e.g., fluids such as those sold under the FLUORINERT® or NOVEC® brands) that is not present in the vacuum chamber except in case of a leak from the cooling line (310).

[0030] In some embodiments, the cooling lines are mechanically connected to the motor core of the motor 312. In some embodiments, the cooling lines are mechanically connected to the digital camera and / or the electro-optical system.

[0031] In some embodiments, a marker species (e.g., marker species 110, FIGS. 1A-1B) is circulated with the coolant in the cooling line (314). For example, the marker species (316) is heavy water (e.g., HDO). In another example, the marker species corresponds to 1-propanol (e.g., resulting from the addition of 1-propanol to the coolant 108) (318).

[0032] The total pressure within the vacuum chamber is measured 320. For example, the total pressure is measured using vacuum gauge 112.

[0033] The partial pressure within the vacuum chamber of a substance that may leak from the cooling line is measured (322). For example, the partial pressure of a marker species within the vacuum chamber is measured (324). In another example, the partial pressure of a fluorocarbon-based fluid within the vacuum chamber is measured (326). The partial pressure is measured using the analyzer 114. In some embodiments, the partial pressure is measured using mass spectrometry. Alternatively, the partial pressure can be measured using infrared spectroscopy (e.g., Fourier transform infrared spectroscopy (FTIR)).

[0034] Method 300 allows for early detection of microcracks or fractures in the cooling lines (e.g., coolant manifolds) of a vacuum system, which can then be repaired in an orderly manner by shutting down the vacuum system before catastrophic damage occurs.

[0035] The foregoing description has been set forth with reference to specific embodiments for purposes of explanation. However, the exemplary description above 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, thereby enabling others skilled in the art to best utilize the embodiments with various modifications suited to the particular use contemplated.

Claims

1. 1. A system comprising: a vacuum chamber; a component disposed within the vacuum chamber that heats during operation; a cooling line mechanically coupled to the component for circulating a coolant therethrough during operation to cool the component, the cooling line containing the coolant and a marker species circulating with the coolant; a vacuum gauge for measuring the total pressure within the vacuum chamber; an analyzer for measuring the partial pressure of the marker species from the cooling line within the vacuum chamber as a reference to the total pressure; A system comprising:

2. The system of claim 1 , wherein the cooling line comprises a coolant manifold within the vacuum chamber.

3. 10. The system of claim 1, further comprising a chiller for cooling the coolant in the cooling line, the chiller being located outside the vacuum chamber, the cooling line extending from the vacuum chamber, through the chiller, and back to the vacuum chamber.

4. The system of claim 1 , wherein the coolant comprises plain water.

5. The system of claim 4 , wherein the marker species is heavy water.

6. The system of claim 4, wherein the marker species corresponds to 1-propanol.

7. the coolant comprises a fluorocarbon-based fluid that is not present in the vacuum chamber except in the event of a leak from the cooling line; The system of claim 1 , wherein the substance that may leak from the cooling line is a fluorocarbon-based fluid.

8. the component comprises a motor disposed within the vacuum chamber; The system of claim 1 , wherein the motor includes a motor coil to which the cooling line is mechanically connected to cool the motor coil.

9. a chuck for supporting the substrate; a translatable stage to which the chuck is mounted for translating the chuck; 9. The system of claim 8, further comprising: a stage motor for translating the stage.

10. The system of claim 9 , wherein the vacuum chamber is a scanning electron microscope (SEM) vacuum chamber.

11. The system of claim 9 , further comprising extreme ultraviolet (EUV) optics disposed within the vacuum chamber.

12. The system of claim 9 , further comprising an electron-optical system disposed within the vacuum chamber, the electron-optical system including a magnetic lens.

13. the component includes a magnetic lens; The system of claim 1 , wherein the cooling line is mechanically connected to the magnetic lens to cool the magnetic lens.

14. the components include a digital camera disposed within the vacuum chamber; 10. The system of claim 1, wherein the cooling line is mechanically connected to the digital camera to cool the digital camera.

15. The system of claim 1 , wherein the analyzer comprises a mass spectrometer.

16. The system of claim 1 , wherein the analyzer comprises an infrared spectrometer.

17. The system of claim 1 , wherein the cooling lines comprise a flexible plastic.

18. 1. A method comprising: operating a component disposed within the vacuum chamber, the operating the component causing heating; circulating a coolant through a cooling line mechanically coupled to the component to cool the component; circulating a marker species along with the coolant through the cooling line; measuring the total pressure within the vacuum chamber; measuring the partial pressure of the marker species in the vacuum chamber as a reference to the total pressure; determining whether the cooling line has a leak based on the partial pressure; A method for providing

19. 20. The method of claim 18, wherein the coolant comprises plain water.

20. 20. The method of claim 19, wherein the marker species is heavy water.

21. 20. The method of claim 19, wherein the marker species corresponds to 1-propanol.

22. circulating the coolant includes circulating a fluorocarbon-based fluid in the cooling lines that is not present in the vacuum chamber except in the event of a leak from the cooling lines; 20. The method of claim 18, wherein measuring the partial pressure comprises measuring the partial pressure of a fluorocarbon-based fluid in the vacuum chamber.

23. operating the component includes operating a motor disposed within the vacuum chamber; 20. The method of claim 18, wherein the cooling line is mechanically connected to a motor coil of the motor.

24. 24. The method of claim 23, wherein operating the motor comprises moving a stage to which a chuck that supports the substrate is attached.

25. 20. The method of claim 18, wherein measuring the partial pressure comprises performing mass spectrometry.

26. 20. The method of claim 18, wherein measuring the partial pressure comprises performing infrared spectroscopy.

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