Self-aligned vacuum feedthrough for liquid nitrogen

Abstract

A light source includes a rotatable drum, an exhaust tube coupled to the rotatable drum to exhaust nitrogen gas from an interior of the rotatable drum, a feed tube located within the exhaust tube to provide liquid nitrogen to the interior of the rotatable drum, and an enclosure to enclose at least a portion of the exhaust tube. The light source also includes a rotational air bearing located between the exhaust tube and the enclosure to allow the exhaust tube to rotate with the rotatable drum.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 006,690, filed April 7, 2020, and U.S. Provisional Patent Application No. 63 / 041,124, filed June 19, 2020, the entire contents of which are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure relates to vacuum feedthrough of liquid nitrogen in a light source, such as an extreme ultraviolet (EUV) light source. Background Technology

[0004] EUV light sources can comprise a rotating drum with an outer surface coated with solid xenon. A plasma emitting EUV light is formed by irradiating the xenon on the outer surface with a laser. Liquid nitrogen is fed into the interior of the drum to maintain the outer surface at a low temperature. Nitrogen gas is then exhausted from the interior of the drum. Traditionally, the nitrogen feed pipe and exhaust pipe extend through the middle of the rotating drum's axis. This arrangement limits feasible drum architectures. Summary of the Invention

[0005] Therefore, a roller architecture is required in which the nitrogen feed pipe and exhaust pipe are decoupled from the roller actuation.

[0006] In some embodiments, a light source includes: a rotatable drum; an exhaust pipe coupled to the rotatable drum to discharge nitrogen gas from the interior of the rotatable drum; a feed pipe located within the exhaust pipe to supply liquid nitrogen to the interior of the rotatable drum; and a housing for surrounding at least a portion of the exhaust pipe. The light source further includes a rotary air bearing located between the exhaust pipe and the housing to allow the exhaust pipe to rotate together with the rotatable drum.

[0007] In some embodiments, a method of operating a light source includes: rotating a drum; supplying liquid nitrogen into the interior of the drum through a feed pipe; and discharging nitrogen from the interior of the drum through an exhaust pipe coupled to the drum. The feed pipe is located within the exhaust pipe. The method further includes using a rotating air bearing between the exhaust pipe and a housing surrounding at least a portion of the exhaust pipe to allow the exhaust pipe to rotate together with the drum. Attached Figure Description

[0008] To better understand the various described embodiments, please refer to the following detailed embodiments in conjunction with the following figures.

[0009] Figure 1 This is a cross-sectional side view of an EUV light source according to some embodiments.

[0010] Figure 2According to some embodiments Figure 1 A cross-sectional side view of the feedthrough assembly of the EUV light source.

[0011] Figure 3 According to some embodiments Figure 1 A perspective view of the feedthrough assembly and roller assembly of the EUV light source.

[0012] Figure 4A This is a perspective view of a feedthrough assembly with a constant level frame according to some embodiments.

[0013] Figure 4B and 4C According to some embodiments Figure 4A A cross-sectional side view of the feedthrough assembly.

[0014] Figure 5 This is a flowchart of a method for operating a light source according to some embodiments.

[0015] The same component symbols in all the accompanying drawings and specifications refer to the corresponding parts. Detailed Implementation

[0016] Various embodiments illustrated in the accompanying drawings will now be described in detail with reference to examples thereof. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the various described embodiments. However, those skilled in the art will understand that the various described embodiments can be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail to avoid unnecessarily obscuring aspects of the embodiments.

[0017] Figure 1 This is a cross-sectional side view of an extreme ultraviolet (EUV) light source 100 according to some embodiments. The EUV light source 100 includes a vacuum chamber 102 (e.g., a billet aluminum chamber). A vacuum pump 110 (e.g., a turbopump) provides a vacuum in the vacuum chamber 102. A laser beam 103 is introduced into the vacuum chamber 102 through a laser objective 104 and an accompanying protective film. The laser objective 104 focuses the laser beam 103 onto the outer surface of a roller 118 coated with solid xenon. When the laser beam 103 irradiates the xenon on the outer surface of the roller 118, it triggers a plasma that emits EUV light 105. A reflector 106 collects a portion of the EUV light 105 and guides the collected EUV light 105 through a window 108 in the vacuum chamber 102. The roller 118 is rotated and also translated vertically to allow different areas on its outer surface to be exposed to the laser beam 103. Xenon can be ejected onto the outer surface of the roller 118 as the roller 118 rotates and translates to maintain the xenon coating.

[0018] The feedthrough assembly 112 supplies liquid nitrogen into the interior of the roller 118 to keep the surface of the roller 118 at a low temperature and thus maintain the xenon coating. The liquid nitrogen evaporates during operation of the EUV light source 100. The feedthrough assembly 112 also vents the resulting nitrogen gas from the roller 118. According to some embodiments, the feedthrough assembly 112 in... Figure 2 A more detailed demonstration is provided below.

[0019] Roller 118 is housed in roller assembly 114, which is coupled to feedthrough assembly 112. Roller assembly 114 also includes a rotary motor 116 for rotating roller 118. Rotary motor 116 is coupled to roller 118 independently of feedthrough assembly 112. Roller assembly 114 has a water-cooled roller cover that receives water from water-cooling input 126. Below roller assembly 114 and therefore below roller 118 is translation motor 120 that linearly translates roller 118 in the vertical direction (i.e., moves the roller up and down). Translation motor 120 is also coupled to roller 118 independently of feedthrough assembly 112. Corresponding linear stage actuator 124 actuates translation motor 120. Weight-compensating bellows 122 is also located below roller assembly 114.

[0020] Figure 2 According to some embodiments, the EUV light source 100 ( Figure 1 A cross-sectional side view of the feed assembly 112. The feed pipe 202 extends to the roller 118. Figure 1 Liquid nitrogen is supplied to the interior of roller 118. Exhaust pipe 204 vents nitrogen from the interior of roller 118. Feed pipe is located within exhaust pipe 204 (e.g., in the middle of exhaust pipe 204) (e.g., such that feed pipe 202 and exhaust pipe 204 are coaxial). Exhaust pipe 204 is mechanically coupled to roller 118. For example, nut 206 couples exhaust pipe 204 to roller 118 (e.g., as shown in the image). Figure 3 (As shown in the diagram). Nut 206 rotates together with exhaust pipe 204 and roller 118. Alternatively, another suitable coupling mechanism can be used to couple exhaust pipe 204 to roller 118.

[0021] A housing 214 (e.g., a stainless steel housing) surrounds at least a portion of the exhaust pipe 204. A rotating air bearing 212 is located between the housing 214 and the exhaust pipe 204 to allow the exhaust pipe 204 to rotate together with the roller 118: the exhaust pipe 204 rotates with the roller 118 while the housing 214 does not rotate. The rotating air bearing 212 contains a thin film of pressurized gas (e.g., substantially particulate-free air) in a narrow gap between the exhaust pipe 204 and the housing 214. This pressurized gas film acts as a substantially frictionless interface between the exhaust pipe 204 and the housing 214. The rotating motor 116 of the rotating roller 118 (… Figure 1The feed pipe 202 is coupled to the roller 118 independently of the exhaust pipe 204. Therefore, the rotary motor 116 causes the roller 118 to rotate, and the rotation of the roller 118 causes the exhaust pipe 204 to rotate. In some embodiments, the feed pipe 202 is fixed and does not rotate with the exhaust pipe 204 and the roller 118.

[0022] like Figure 2 As shown, the feed pipe 202 and exhaust pipe 204 extend vertically above the drum 118. A rotating air bearing 212 allows the exhaust pipe 204 to translate vertically together with the drum 118: the exhaust pipe 204 translates vertically with the drum 118, while the housing 214 does not translate vertically. A translation motor 120 (for vertically translating the drum 118)... Figure 1 The feed pipe 202 is coupled to the roller 118 independently of the exhaust pipe 204. Therefore, the translation motor 120 causes the roller 118 to translate vertically, and the vertical translation of the roller 118 causes the exhaust pipe 204 to translate vertically. In some embodiments, the feed pipe 202 is fixed and does not translate vertically together with the exhaust pipe 204 and the roller 118.

[0023] The exhaust pipe 204 has a heat insulation material 210 beneath the outer layer 208. For example, the heat insulation material 210 is welded titanium. The heat insulation material 210 isolates the outer layer 208 and the rotating air bearing 212 from the cold air inside the exhaust pipe 204, as cold air can cause the rotating air bearing 212 to malfunction. Although cold nitrogen is present in the exhaust pipe 204, the heat insulation material 210 allows the outer casing 214 to be at or near room temperature. In another example, a vacuum gap (e.g., vacuum gap 406) exists between the inner and outer layers of the exhaust pipe 204. Figures 4B to 4C Provides insulation.

[0024] An exhaust pipe 204 extends from the drum 118 to a chamber 226 having an outlet 228. The exhaust pipe 204 terminates in the chamber 226. The chamber 226 receives nitrogen from the exhaust pipe 204 and discharges nitrogen through the outlet 228. A heating block 224 is located between the chamber 226 and the outer casing 214 to thermally insulate the outer casing 214 from the chamber 226, which is cooler due to the nitrogen. For example, the heating block 224 allows the outer casing 214 to be at or near room temperature.

[0025] Pump ring 222 evacuates air from air bearing 212 to prevent air from entering vacuum chamber 102. Figure 1 Argon gas is injected through the argon purification ring 220, and the argon gas is primarily evacuated by the pump ring 222. The argon gas from the argon purification ring 220 helps ensure that air from the air bearing 212 does not enter the vacuum chamber 102. A small amount of argon gas may enter the vacuum chamber, but its impact on the function of the EUV light source 100 is minimal.

[0026] In some embodiments, flange 218 is used to level housing 214 and thus to level feedthrough assembly 112. Linear air bearing 216 is located between housing 214 and flange 218 to adjust the horizontal translation of housing 214 and exhaust pipe 204 relative to flange 218. (Heating block 224 and chamber 226 also translate horizontally with housing 214.) Linear air bearing 216 contains a thin film of pressurized gas (e.g., substantially particulate-free air) in the narrow gap between housing 214 and flange 218. This pressurized gas film acts as a substantially frictionless interface between housing 214 and flange 218. Linear air bearing 216 compensates for misalignment between feedthrough assembly 112 and roller assembly 114 and compensates for runout of roller 118. Bellows 223 extends from flange 218 to housing 214 (e.g., to the bottom of housing 214) to provide a vacuum seal. Bellows 223 has a first end connected to flange 218 and a second end connected to housing 214.

[0027] Figure 3 According to some embodiments, the EUV light source 100 ( Figure 1 A perspective view of the feedthrough assembly 112 and the roller assembly 114. Nut 206 couples the feedthrough assembly 112 to the roller assembly 114. An opening on the side of the roller assembly 114 exposes the outer surface of the roller 118 to the laser beam 103, which passes through the laser objective lens 104. Figure 1 Enter vacuum chamber 102.

[0028] Figures 4A to 4C Demonstrating one of the linear air bearings 216 according to some embodiments ( Figure 2 The alternative feeder assembly 400 is replaced by the constant level frame 402. Figure 4A This is a perspective view of feedthrough assembly 400. Figure 4B and 4C This is a cross-sectional side view of the feedthrough assembly 400; Figure 4C The view relative to Figure 4B The view is rotated 90°. The feedthrough assembly 400 is part of the EUV light source, which also includes, for example, a vacuum chamber 102 having a laser objective 104, a mirror 106, a window 108, a vacuum pump 110, and a roller assembly 114. Figure 1 The feedthrough assembly 400 includes a rotating air bearing 212 between the housing 214 and the exhaust pipe 204. Figures 4B to 4C Rotating air bearing 212, as for feedthrough assembly 112 ( Figure 2 It operates as described.

[0029] Like feedthrough assembly 112 ( Figures 1 to 3The feed pipe 202 extends into the interior of the roller 118, and the exhaust pipe 204 is coupled to the roller 118. A coupling element 410 (e.g., a machined coupling element) couples the feed assembly 400 to the roller assembly 114 and thus couples the exhaust pipe 204 to the roller 118. Pipe 412 ( Figure 4A and 4B A pipe 414 is connected to a feed pipe 202 and supplies liquid nitrogen to the feed pipe 202, which in turn supplies liquid nitrogen into the interior of the drum 118. A pipe 414 is connected to an outlet 228 of chamber 226 to discharge nitrogen from chamber 226. Therefore, nitrogen is discharged from the interior of the drum 118 through the exhaust pipe 204, chamber 226, outlet 228, and pipe 414. According to some embodiments, the feedthrough assembly 400 does not include a heating block 224. Figures 2 to 3 ).

[0030] 402 constant level frame (which uses attachment 412) Figure 4A and 4C ) Attached to a vacuum chamber (e.g., vacuum chamber 102, Figure 1 Adjust the tilt and rotation of the outer casing 214 and the exhaust pipe 204. The bushing 404 in the constant level frame 402 ( Figure 4B Adjust the horizontal translation of housing 214 and exhaust pipe 204 (e.g., caused by the runout of roller 118 and the misalignment of feed assembly 400 with roller assembly 114).

[0031] The exhaust pipe 204 has an outer layer 408 separated from the inner surface of the exhaust pipe 204 by a vacuum gap 406. The vacuum gap 406 provides insulation for the housing 214 relative to the interior of the exhaust pipe 204. For example, the vacuum gap 406 allows the housing 214 to be at or near room temperature, even though cold nitrogen is present in the exhaust pipe 204.

[0032] The feedthrough assembly 400 can be lowered into the vacuum chamber during EUV light source assembly and raised from the vacuum chamber during maintenance (e.g., to allow replacement of the roller assembly 114). The leveling frame 402 allows maintenance to be performed without having to readjust the feedthrough assembly 400.

[0033] Figure 5 It is an operating light source (e.g., EUV light source 100) according to some embodiments. Figure 1 The flowchart of method 500 is shown. In method 500, roller 118 is rotated (502). In some embodiments, roller 118 is vertically translated (504) while rotating.

[0034] Liquid nitrogen is supplied (506) to the interior of the drum 118 through the feed pipe 202. Nitrogen gas is discharged (508) from the interior of the drum 118 through the exhaust pipe 204 coupled to the drum 118. The feed pipe 202 is located inside the exhaust pipe 204.

[0035] A rotating air bearing 212 is used between the exhaust pipe 204 and the housing 214 surrounding at least a portion of the exhaust pipe 204 to allow (510) the exhaust pipe 204 to rotate together with the roller 118. In some embodiments, the rotating air bearing 212 allows (512) the exhaust pipe 204 to translate vertically together with the roller 118.

[0036] In some embodiments, a linear air bearing 216 is used between the housing 214 and the flange 218. Figure 2 (514) Adjust the horizontal translation of the housing 214 and the exhaust pipe 204 relative to the flange 218. The flange 218 levels the housing 214.

[0037] In some other embodiments, a constant level 402 coupled to housing 214 is used. Figures 4A to 4C The tilt of the housing 214 and exhaust pipe 204 can be adjusted using the (516) bushing 402. The rotation of the housing 214 and exhaust pipe 204 can also be adjusted using the leveling bracket 402. Figure 4B (518) adjust the horizontal translation of the outer casing 214 and the exhaust pipe 204.

[0038] although Figure 5 The operations of method 500 are displayed in a specific order, but the execution of the operations can overlap. For example, all operations are executed simultaneously. Method 500 may contain more or fewer operations. Two or more operations can be combined into a single operation.

[0039] The above description has been given with reference to specific embodiments for illustrative purposes. However, the illustrative discussion above is not intended to be exhaustive or to limit the scope of the claims to the precise form disclosed. Many modifications and variations can be made in light of the above teachings. The embodiments have been chosen to best explain the basic principles of the claims and their practical application, thereby enabling those skilled in the art to best use the embodiments and various modifications suitable for a particular intended purpose.

Claims

1. A light source, comprising: Rotatable roller; An exhaust pipe coupled to the rotatable drum to discharge nitrogen gas from the interior of the rotatable drum; A feed pipe, located inside the exhaust pipe, supplies liquid nitrogen into the interior of the rotatable drum; A housing for enclosing at least a portion of the exhaust pipe; A rotating air bearing is located between the exhaust pipe and the housing to allow the exhaust pipe to rotate together with the rotatable roller; and An electric motor, which is coupled to the rotatable drum independently of the exhaust pipe to rotate the rotatable drum.

2. The light source according to claim 1, wherein: The exhaust pipe and the feed pipe extend vertically; The rotatable roller can be vertically translated; and The rotating air bearing allows the exhaust pipe to move vertically together with the rotatable roller.

3. The light source according to claim 2, wherein: The motor is a first motor; and The light source also includes a second motor, which is coupled to the rotatable roller independently of the exhaust pipe to vertically translate the rotatable roller.

4. The light source according to claim 3, wherein: The second motor is located below the rotatable roller; and The exhaust pipe and the feed pipe extend above the rotatable drum.

5. The light source according to claim 2, further comprising: Flange, which is used to level the housing; and A linear air bearing is located between the housing and the flange.

6. The light source according to claim 5, further comprising a bellows having a first end connected to the flange and a second end connected to the housing.

7. The light source of claim 2, further comprising a constant leveling bracket coupled to the housing to adjust the tilt of the housing and the exhaust pipe.

8. The light source according to claim 7, wherein the constant level frame includes a bushing for adjusting the horizontal translation of the housing and the exhaust pipe.

9. The light source according to claim 1, wherein the exhaust pipe comprises a heat-insulating material.

10. The light source according to claim 9, wherein the heat insulation material comprises titanium.

11. The light source according to claim 9, wherein the heat insulation material comprises a vacuum gap between the first layer of the exhaust pipe and the second layer of the exhaust pipe.

12. The light source according to claim 9, further comprising: A chamber for receiving nitrogen from the exhaust pipe, wherein the exhaust pipe terminates in the chamber and the chamber has an output for discharging the nitrogen; and A heating block is located between the chamber and the outer casing to thermally insulate the outer casing from the chamber.

13. The light source of claim 1, further comprising a nut for coupling the exhaust pipe to the rotatable roller.

14. A method for operating a light source, comprising: Use a motor to rotate the drum; Liquid nitrogen is supplied into the interior of the drum through a feed pipe; Nitrogen gas is discharged from the interior of the drum through an exhaust pipe coupled to the drum, wherein the feed pipe is located inside the exhaust pipe; and A rotating air bearing is used between the exhaust pipe and a housing that surrounds at least a portion of the exhaust pipe to allow the exhaust pipe to rotate together with the roller, wherein the motor is coupled to the roller independently of the exhaust pipe.

15. The method of claim 14, wherein the exhaust pipe and the feed pipe extend vertically, the method further comprising: While rotating the roller, the roller is translated vertically; and The rotating air bearing is used to allow the exhaust pipe to move vertically along with the roller.

16. The method of claim 15, further comprising using a linear air bearing between the housing and the flange to adjust the horizontal translation of the housing and the exhaust pipe relative to the flange, wherein: The flange levels the outer casing; and The horizontal translation includes displacement from the bouncing of the roller.

17. The method of claim 15, further comprising using a leveling bracket coupled to the housing to adjust the tilt of the housing and the exhaust pipe.

18. The method of claim 17, wherein the constant leveling frame includes a bushing, the method further comprising using the bushing to adjust the horizontal translation of the housing and the exhaust pipe, the horizontal translation including displacement from the bounce of the roller.

19. A light source comprising: A roller that can move vertically and rotate; An exhaust pipe coupled to the drum to discharge nitrogen from the interior of the drum, wherein the exhaust pipe extends vertically. A feed pipe, located within the exhaust pipe, supplies liquid nitrogen into the interior of the drum, wherein the feed pipe extends vertically; A housing for enclosing at least a portion of the exhaust pipe; A rotating air bearing is located between the exhaust pipe and the housing to allow the exhaust pipe to rotate and translate vertically together with the roller; Flange, which is used to level the housing; and A linear air bearing is located between the housing and the flange.

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