WO2024033020A1

WO2024033020A1 - Debris handling apparatus and method for an extreme ultraviolet light source

Info

Publication number: WO2024033020A1
Application number: PCT/EP2023/069737
Authority: WO
Inventors: Esteban Joseph Sandoval JOHNSON; Kyle John SCAFFIDI; Gary Dwayne MANDRUSIAK; Liza EASO; Adam CROCKER; Bryce Collin CAPUTO
Original assignee: Asml Netherlands B.V.
Priority date: 2022-08-12
Filing date: 2023-07-15
Publication date: 2024-02-15
Also published as: CN119404141A; TW202422235A

Abstract

A debris handling apparatus controls debris within a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source in which produced EUV light is transmitted along an optical axis within the chamber interior. The debris handling apparatus includes: a linear array of fins and a port liner. The fins are arranged relative to each other such that grooves are formed between adjacent fins of the array, each groove including an input groove passage and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage. The port liner defines a fluid port that includes an upstream side positioned exterior to the chamber and in fluid communication with the chamber interior, and a downstream side adjacent to and in fluid communication with the input groove passages.

Description

DEBRIS HANDLING APPARATUS AND METHOD FOR AN EXTREME ULTRAVIOLET LIGHT SOURCE

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63/397,794 which was filed on August 12, 2022 and US application 63/426,921 which was filed on November 21, 2022 and which are incorporated herein in their entirety by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to apparatuses and methods for handling debris that is produced in an extreme ultraviolet (“EUV”) light source during the generation of EUV radiation from a plasma.

BACKGROUND

[0003] Extreme ultraviolet radiation, e.g., electromagnetic radiation having wavelengths of around 50 nm or less (also sometimes referred to as soft x-rays), including radiation at a wavelength of about 13.5 nm, can be used in photolithography processes to produce extremely small features in or on substrates such as silicon wafers. Methods for generating EUV radiation include converting a target material to a plasma state. The target material includes at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV portion of the electromagnetic spectrum. The target material can be solid, liquid, or gas. In one such method, often termed laser produced plasma (“LPP”), the required plasma can be produced by using a “source” laser, typically a CO2 laser emitting infrared light at a wavelength at or about 10,600 nanometers (nm), to irradiate with one or more light pulses a target containing one or more EUV line-emitting elements. The plasma is typically produced in a sealed “source vessel” which is typically a vacuum chamber.

SUMMARY

[0004] In some general aspects, a debris handling apparatus is for controlling debris within a controlled-environment chamber of an extreme ultraviolet (EUV) radiation source. The debris handling apparatus includes an array of v-shaped fins, with the fins arranged relative to each other such that v-shaped grooves are formed between pairs of adjacent fins of the array. Each v-shaped fin includes two segments arranged at an obtuse angle from each other, and each v-shaped groove includes an input groove passage facing an interior of the chamber and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage. An angle between each segment and the flow direction is less than 20°.

[0005] Implementations can include one or more of the following features. For example, each v- shaped fin can have a thickness in the range of 1-3 mm. A distance between each adjacent fin can be in a range of 9 to 20 millimeters (mm) and a length of each v-shaped fin along the flow direction can be at least 50 mm, at least 75 mm, at least 100 mm, or at least 120 mm.

[0006] Each v-shaped fin can be made up of a first sub-fin and a second sub-fin. An interface between the first sub-fin and the second sub-fin can include a portion linearly oriented at an angle relative to the flow direction. The debris handling apparatus can further include a liner in which the array of v-shaped fins is mounted. The first sub-fin can be mounted to a first wall of the liner and the second sub-fin can be mounted to a second wall of the liner. The liner can include a different material than the material of the v-shaped fins. The liner can be made of stainless steel and the v-shaped fins can be made of molybdenum. Adjacent pairs of v-shaped fins can be mounted together to the liner at the same connection interface. The v-shaped fins can each be mounted to the liner at a plurality of connection interfaces, with each connection interface including a bolt through the liner and the v- shaped fins, a nut, and a spring washer.

[0007] Each v-shaped fin can include a concave beveled edge at the input groove passage of the adjacent v-shaped groove. The debris handling apparatus can include a drainage apparatus in fluid communication with the v-shaped grooves, the drainage apparatus configured to remove debris collected by the array of v-shaped fins. Each v-shaped fin can include or be made of a refractory metal or a metal alloy. An angle between each segment and the flow direction can be greater than 0° and less than 20°; greater than 5° and less than 15°; or greater than 10° and less than 13°.

[0008] In other general aspects, a debris handling apparatus is for controlling debris within a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source in which produced EUV light is transmitted along an optical axis within the chamber interior. The debris handling apparatus includes: a linear array of fins and a port liner. The fins are arranged relative to each other such that grooves are formed between adjacent fins of the array. Each groove includes an input groove passage and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage. The port liner defines a fluid port that includes an upstream side positioned exterior to the chamber and in fluid communication with the chamber interior, and a downstream side adjacent to and in fluid communication with the input groove passages.

[0009] Implementations can include one or more of the following features. For example, the flow direction can be the same for all of the grooves.

[0010] The upstream side of the port liner can be in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber. The chamber passage can have an annular shape and extend around an outer circumference of the chamber exterior. The upstream side of the port liner can be positioned at an angle about the outer circumference of the chamber exterior at least 90° away from the exhaust opening.

[0011] The debris handling apparatus can further include a drainage apparatus configured to drain debris collected in the linear array of fins away from the linear array of fins. The upstream side of the port liner can be in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber, and the exhaust opening can be positioned gravitationally below the fluid port of the port liner, and the drainage apparatus can include the fluid port of the port liner and at least a portion of the chamber passage. The exhaust opening can be positioned gravitationally above the fluid port of the port liner, and the drainage apparatus can include a drainage port in fluid communication with the output groove passages.

[0012] The EUV light can be transmitted from a primary focus to a secondary focus along the optical axis within the chamber interior and neither the primary focus nor the secondary focus can be in the sight line of the upstream side of the fluid port.

[0013] Each fin can be a v-shaped fin including two segments arranged at an obtuse angle from each other, and each groove can be a v-shaped groove. Each v-shaped fin can be made up of a first sub-fin and a second sub-fin.

[0014] The debris handling apparatus can also include an array liner in which the array of fins is mounted, the array liner and the port liner being hermetically connected.

[0015] Each fin can include a first sub-fin and a second sub-fin that are disconnected from each other. The debris handling apparatus can further include an array liner in which the array of fins is mounted. The first sub-fin can be mounted to a first wall of the array liner by way of a demountable connection and the second sub-fin can be mounted to a second wall of the array liner by way of a demountable connection. A gap between the first sub-fin and the second sub-fin extends along a direction that can be unparallel with an edge of the first sub-fin that is mounted to the first wall. The extent of the gap along a direction perpendicular to the flow direction can be generally constant throughout the gap.

[0016] Each fin can include a concave beveled edge at the input groove passage of the adjacent groove. The concave beveled edge can be formed with two beveled edges that define a notch facing the fluid port. Each fin can include a convex beveled edge at the output groove passage of the adjacent groove.

[0017] The debris handling apparatus can also include a heater configured to maintain a temperature of the fins above a melting point of the debris produced during production of the EUV light. The debris handling apparatus can also include an array liner in which the array of fins is mounted, wherein the heater can be in thermal contact with the array liner and the port liner.

[0018] Each fin can include or be made of a refractory metal or a metal alloy.

[0019] In other general aspects, an extreme ultraviolet (EUV) radiation source vessel includes: a chamber, a control system, a debris handling apparatus, and an exhaust opening. The chamber includes one or more walls that define a chamber interior. A primary focus at which plasma is created from a light pulse interacting with a target and a secondary focus at which EUV radiation produced by the plasma is focused are in the chamber interior, and, in use, EUV light is transmitted from the primary focus to the secondary focus along an optical axis. The control system is configured to maintain a temperature of the chamber and the chamber interior below a melting point of material of the target and to flow a purge gas away from the primary focus. The debris handling apparatus includes a fluid port positioned exterior to the chamber and includes an upstream side in fluid communication with the chamber interior, and a downstream side in fluid communication with a debris capture array. The exhaust opening fluidly communicates with the chamber interior at a first end and the upstream side of the fluid port at a second end.

[0020] Implementations can include one or more of the following features. For example, the control system can be configured to maintain a temperature of at least a portion of the debris handling apparatus above the melting point of the material of the target and a material of debris produced within the chamber interior.

[0021] In other general aspects, a method is performed for handling debris produced in a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source. The method includes: passing a flow of gas through an exhaust opening in a wall of the chamber, including directing the flow of gas from the chamber interior through the exhaust opening to an exterior to the chamber; directing the flow of gas from the exhaust opening to a debris handling apparatus exterior to the chamber; collecting debris within the flow of gas at the debris handling apparatus; and draining debris collected by the debris handling apparatus through a drainage apparatus.

[0022] Implementations can include one or more of the following features. For example, the flow of gas can be directed from the chamber interior through the exhaust opening by directing the flow of gas from a collector in the chamber interior to the exhaust opening. The flow of gas can be directed from the exhaust opening to the debris handling apparatus exterior to the chamber by passing the flow of gas around at least a portion of an outer circumference of the chamber through a chamber passage exterior to an upstream side of a fluid port of the debris handling apparatus. The debris within the flow of gas can be collected at the debris handling apparatus by passing debris through an input groove passage of a plurality of grooves formed between pairs of adjacent fins in a linear array of fins, and collecting debris within each of the grooves. The debris collected by the debris handling apparatus can be drained by navigating the flow of debris away through each respective groove, and entraining the debris within the respective groove. The debris collected by the debris handling apparatus can be drained by passing the collected debris along a drain path that overlaps a gas path along which the flow of gas is directed. The debris collected by the debris handling apparatus can be drained by passing the collected debris along a drain path that is separate from a gas path along which the flow of gas is directed.

[0023] The method can also include compensating for thermal expansion mismatch between a liner in which the fins are mounted and the fins. The flow of gas can be directed from the exhaust opening to the debris handling apparatus exterior to the chamber by directing the flow of gas along a single path to the debris handling apparatus. [0024] In other general aspects, a debris handling apparatus is for controlling debris within a controlled-environment chamber of an extreme ultraviolet (EUV) radiation source. The debris handling apparatus includes an array of v-shaped fins arranged relative to each other such that v- shaped grooves are formed between adjacent fins of the array. Each v-shaped fin includes two segments arranged at an obtuse angle from each other, and each v-shaped groove includes an input groove passage facing an interior of a chamber and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage. Each v-shaped fin includes a concave beveled edge at the input groove passage of the adjacent v-shaped groove.

[0025] Implementations can include one or more of the following features. For example, the concave beveled edge can be formed with two beveled edges that define a notch facing the chamber interior. Each v-shaped fin can include a convex beveled edge at the output groove passage of the adjacent v-shaped groove. The debris handling apparatus can include a heater configured to maintain a temperature of the v-shaped fins above a melting point of the material in the debris. The debris handling apparatus can include a liner in which the array of v-shaped fins is mounted, and the heater can be in thermal contact with the liner.

DRAWING DESCRIPTION

[0026] Fig. 1A is a schematic side cross-sectional diagram of a debris handling apparatus configured relative to a chamber of an extreme ultraviolet radiation source;

[0027] Fig. IB is a schematic cross-sectional diagram of the debris handling apparatus of Fig. 1A taken along line IB- IB;

[0028] Fig. 2 is a schematic cross-sectional diagram of an implementation of the debris handling apparatus of Fig. 1;

[0029] Fig. 3 A is a perspective view of a port liner and an array liner of an implementation of the debris handling apparatus of Figs. 1 and 2;

[0030] Fig. 3B is a perspective view of the port liner and the array liner of Fig. 3A as viewed along a flow direction;

[0031] Fig. 3C is a top cross-sectional view of the port liner, the array liner, and an array of fins within the array liner of Figs. 3A and 3B;

[0032] Fig. 3D is a close-up view of a fin of the array of Fig. 3C;

[0033] Fig. 3E is a side cross-sectional view of the array liner and the array of fins of Figs. 3A-

3C, the flow direction being into the page;

[0034] Fig. 4A is a perspective view of an implementation of a single fin in an array;

[0035] Fig. 4B is a side view of the single fin of Fig. 4A;

[0036] Fig. 4C is a cross-sectional view taken along line 4C-4C of Fig. 4B;

[0037] Fig. 5A is a perspective view of an implementation of a pair of fins in an array; [0038] Fig. 5B is a side view of the pair of fins of Fig. 4A;

[0039] Fig. 5C is a cross-sectional view taken along line 5C-5C of Fig. 5B;

[0040] Fig. 5D is a cross-sectional view of a portion 5D of the pair of fins of Fig. 5B showing details of a sub-connection interface that connects the pair of fins to the array;

[0041] Fig. 5E is an exploded perspective view of the implementation of the pair of fins of Fig. 5A;

[0042] Fig. 6 is a schematic cross-sectional view of an implementation of the debris handling apparatus of Figs. 1A, IB and 2;

[0043] Fig. 7 is a schematic cross-sectional view of an implementation of the debris handling apparatus of Figs. 1A, IB and 2; and

[0044] Fig. 8 is a perspective view of a port liner and an array liner of an implementation of the debris handling apparatus of Figs. 1A and IB and 2 and including a heater.

DETAILED DESCRIPTION

[0045] Referring to Figs. 1A and IB, a debris handling apparatus 100 is configured for controlling debris within a controlled-environment interior 161 of a chamber (or vessel) 162 of an extreme ultraviolet (EUV) radiation source 160. The debris handling apparatus 100 enables the removal of debris from the interior 161 of the chamber 162 and thus acts to clean the interior 161 of the chamber 162. Moreover, because of the design and placement of the debris handling apparatus 100, it is more durable and effective over a longer term than prior debris handling apparatuses. In the EUV radiation source 160, produced EUV light 163 is transmitted from a primary focus PF to a secondary focus SF along an optical axis OA within the chamber interior 161. The debris handling apparatus 100 controls debris within the interior 161 by removing debris from the interior 161 and transporting the debris to one or more locations outside the interior 161. The EUV radiation source 160 is shown in schematic cross section in the X-Z plane, with the X axis extending up and down in the plane of the page and the Z axis extending left and right in the plane of the page, the Z axis aligned with the optical axis OA. The chamber 162 can be generally symmetrical about the Z axis such that it includes a conical shape that tapers from the primary focus PF to the secondary focus SF. Depending on the design of the EUV radiation source 160, the optical axis OA (and the Z axis) can be positioned in different directions relative to the gravitational direction.

[0046] Debris can be formed during the production of the EUV light 163, as follows. Targets 164 that are delivered to an irradiation site 165 (at the primary focus PF) individually interact with one or more pulses of light in a light beam 166. A plasma 167 is produced from this interaction, and the plasma 167 produces the EUV light 163. The EUV light 163 is collected by a collector 168, which can be a near-normal incidence collector mirror defined by the optical axis OA and having a reflective surface 168r that can be in the form of a prolate spheroid (that is, an ellipse rotated about its major axis). In this way, the collector 168 defines the primary focus PF at the irradiation site 165 and the secondary focus SF at the exit of the chamber 162.

[0047] The targets 164 include an EUV emitting target material such as, but not limited to, tin, lithium, xenon, or combinations thereof. The targets 164 at the irradiation site 165 can be in the form of liquid droplets, or alternatively can be solid particles or solid particles contained within liquid droplets. For example, the element tin can be present as a target in the form of pure tin; a tin compound such as SnBr4, SnBrj, SnFU; a tin alloy such as tin-gallium alloys, tin-indium alloys, or tin- indium-gallium alloys; or a combination thereof. High energy ions and/or particles and vapor of or containing target material can be formed during the production of the EUV light 163. For example, particles of target material and high energy ions and vapor are byproducts from light-based vaporization or ablation processes that can occur when the targets 164 interact with the pulses of the light beam 166, and these byproducts are debris within the interior 161 of the chamber 162. Generally, debris can contaminate the reflective surface 168r of the collector 168. For example, particles of target material and energetic ions and vapor (all debris) can cause physical damage and localized heating of the reflective surface 168r of the collector 168. The debris handling apparatus 100 is designed, in combination with other components that direct the debris within the interior 161 of the chamber 162 toward the debris handling apparatus 100, to remove the debris from the interior 161 of the chamber 162 and to prevent the debris from re-entering the interior 161 after it has been removed.

[0048] The debris handling apparatus 100 includes a linear array 105 of fins 106. The fins 106 are arranged relative to each other such that grooves 107 (or gaps) (Fig. IB) are formed between pairs of adjacent fins 106 of the array. Each groove 107 is defined by the pair of adjacent fins 106. A planar input groove passage 107i and a planar output groove passage 107o that faces an exhaust pump 108, define the input and output of each of the grooves 107. A localized flow direction F is defined from and extends from the input groove passage 107i to the output groove passage 107o. This flow direction F generally governs the flow of the debris as it enters the array 105 and is generally the same for all of the grooves 107 defined in the array 105. The fins 106 as well as the grooves 107 extend along a plane that goes into and/or out of the page of Fig. IB as well as along the localized flow direction F. In Fig. 1 A, the fins 106 and the grooves 107 extend along the plane of the page. The array 105 of fins 106 is mounted inside of and to an array liner 109 by way of one or more connection interfaces 103. The array 105 is housed within a cavity 109c of the liner 109.

[0049] The debris handling apparatus 100 includes a port liner 115 that defines a fluid opening or port 116. The fluid port 116 includes an upstream side 117u positioned at an exterior 169 to the chamber 162. The fluid port 116, by way of the upstream side 117u, is in fluid communication with the chamber interior 161. The fluid port 116 includes a downstream side 117d that is in fluid communication with the input groove passages 107i of the grooves 107. The port liner 115 and the array liner 109 are hermetically connected to each other such that materials (for example, debris) inside the fluid port 116 is forced to flow through the array 105 of fins 106 and not escape between the port liner 115 and the array liner 109.

[0050] The upstream side 117u of the fluid port 116 of the port liner 115 is in fluid communication with an exhaust opening 120 in a wall 170 of the chamber 162. In some implementations, such as also shown in Fig. 7 below, the fluid connection between the upstream side 117u of the fluid port 116 and the exhaust opening 120 is by way of a circumferential chamber passage 121 that is at the exterior 169 to the chamber 162. The chamber passage 121 is defined within or by a circumferential passage structure 122. Both the chamber passage 121 and the structure 122 can have an annular shape such that both extend around at least part of the outer circumference of the wall 170 of the chamber 162. For example, and with specific reference to Fig. IB, the upstream side 117u of the port liner 115 can be positioned at an angle (in the XY plane) about the outer circumference of the wall 170 (or the chamber exterior 169) from the exhaust opening 120. The angle can be any value. For example, the angle can be at least 45°, at least 60°, at least 70°, at least 90°, or at least 120°. As another example, the angle can be any value in a range between 45° and 180°. In other implementations, such as shown in Fig. 6 below, the fluid connection between the upstream side 117u of the fluid port 116 and the exhaust opening 120 is direct. In both implementations, the placement of the port liner 115 is far enough away from optical axis OA such that neither the primary focus PF nor the secondary focus SF is in a sight line of the upstream side 117u of the fluid port 116.

[0051] In both implementations, the debris handling apparatus 100 is placed exterior to (or outside of) the chamber 162, and is therefore removed from the interior 161. Nevertheless, the debris handling apparatus 100 is in fluid communication with the interior 161 of the chamber 162 and able to receive the debris created within the interior 161 of the chamber 162. Accordingly, it is not necessary to create an environment in the interior 161 of the chamber 162 to specifically accommodate the design of the debris handling apparatus 100. For example, the interior 161 can accommodate gas flows that can be used as a buffer gas for debris and/or vapor emanating from the irradiation site 165. In some implementations, hydrogen (Hz) is used as a hydrogen gas flow within the interior 161 since hydrogen is relatively transparent to EUV radiation having a wavelength of about 13.5 nanometers (nm). Hydrogen gas can be introduced into the interior 161 to slow down and/or guide energetic debris (such as ions, atoms, and clusters) of target material created by irradiation of the targets 164 at the irradiation site 165 and by the resulting plasma 167. The debris (which is highly energetic) is slowed down (or de-energized) by collisions with the gas molecules (the Hj molecules) in the flow. This gas flow can be directed to prevent debris produced at the irradiation site 165 from reaching the reflective surface 168r of the collector 168. Thus, this gas flow can reduce damage to the collector 168 otherwise caused by vapor deposition, implantation, and deposition of sputtered target material. [0052] When targets 164 that are tin or tin-containing are used, the use of hydrogen gas for gas flow with tin targets 164 can result in another potential source of contamination in the interior 161 of the chamber 162. In particular, molten tin can be ejected or spit from surfaces in the interior 161 that are coated or subject to coating with the molten tin when hydrogen bubbles form and grow in or under the molten tin and then burst. One way to prevent tin spitting is to prevent molten target material from accumulating on a surface within the interior 161 of the chamber 162 by keeping the temperature of the surface below or well below the melting point of the target material. The melting point of tin is about 232 °C. For example, some surfaces of objects or portions of the interior 161 can be maintained at a temperature below 232 °C, or in a temperature in the range of about 50 °C to about 110 °C. Any tin that deposits on a surface maintained at that temperature is kept in solid form and prevents or resists spitting. By moving the debris handling apparatus 100 (and specifically the linear array 105 of fins 106) out of the interior 161, it is possible to maintain surfaces and the interior 161 at such low temperatures.

[0053] The deposition of debris onto cold surfaces within the interior 161 can shorten the length of service intervals of the EUV radiation source 160. Growth of such deposits on cold surfaces and accumulation of liquid tin on surfaces can be reduced by the use of gas flows inside the interior 161. Different gas flows can be used. For example, one or more gas flows can be directed along the reflective surface 168r of the collector 168. As another example, one or more gas flows can be directed through apertures generally perpendicular to a surface to be protected within the interior 161. Gas flows can be directed through one or more walls 170 of the chamber 162. As a further example, protective gas flows can be parallel to, or have a component of flow directed parallel to, the surface to be protected (such as in regions near the secondary focus SF). As a further example, a gas flow (referred to as a dynamic gas lock) can be used to prevent material from leaving the EUV radiation source 160 in the region of the secondary focus SF. A dynamic gas lock can produce a gas flow from the region of the secondary focus SF toward the irradiation site 165. In general, a stable guided flow 171 that flows away from the collector 168 can be formed from a combination of one or more of these flows. This guided flow 171 helps contain and carry away from the collector 168 the debris, which includes vapor, ions, and micro and nano-particles, and is generated from the targets 164 during production of plasma 167. Other flows can be formed. Moreover, although the guided flow 171 is depicted with merely two pathways in Fig. 1 A, it should be understood that it can extend along multiple pathways. The flow may extend along various other pathways or regions away from the collector 168 and toward the exhaust opening 120.

[0054] Low pressures are used within the interior 161, and pressure differentials at the exhaust opening 120 are not large. Nevertheless, a small pressure differential at the exhaust opening 120 is produced by vacuum pumping the exhaust opening 120 (by way of the exhaust pump 108, which is in fluid communication with the exhaust opening 120). The stable guided flow 171 of the debris entrained and contained in the flow 171 is thereby directed into the exhaust opening 120 and out of the interior 161, thus substantially reducing the amount of debris contacting surfaces within the interior 161. The debris is directed into the exhaust opening 120, optionally, through the chamber passage 121 depending on the placement of the chamber 162, through the fluid port 116 of the port liner 115, and then into the linear array 105 of fins 106. The debris is captured within the fins 106. [0055] Because the array 105 of fins 106 is external to the chamber 162, the array 105 can be made into a linear form (as opposed to a radial form, which can be used when mounted in the interior 161 of the chamber 162). In this way, the design of the array 105 is simplified, which leads to simplification and efficiencies in manufacturing and installation. Moreover, because it is external to the chamber 162, the debris handling apparatus 100 can be replaced without having to open the chamber 162. Additionally, because the debris handling apparatus 100 is external to the chamber 162, the upstream side 117u of the fluid port 116 and the array 105 of fins 106 are not in the sight line of the primary focus PF or the secondary focus SF, as discussed above. Because of this, EUV light 163 is less likely to interact with the debris handling apparatus 100, and specifically, less likely to interact with the fins 106. Accordingly, there is advantageously a substantial reduction in stray light produced from reflections of the EUV light 163 or even the light beam 166 from surfaces of the fins 106 when compared with fins that are placed inside the interior 161 (and in the direct sight line of the primary focus PF and the secondary focus SF). Thus, the EUV light 163 is more efficiently produced, and is more efficiently transported to the secondary focus SF for use by a photolithography exposure apparatus that receives the EUV light 163 when using the debris handling apparatus 100.

[0056] The debris handling apparatus 100 can also include a heater 141 configured to maintain a temperature of the fins 106 above a melting point of the material of the debris in order to prevent the debris from sticking to the fins 106 after it is captured within the fins 106. Additionally, the debris handling apparatus 100 includes a drainage apparatus 130 configured to drain any debris that is collected in the fins 106 of the array 105 away from the array 105. The drainage apparatus 130 relies on gravity to remove the debris from the array 105. Moreover, the drainage apparatus 130 is configured to function independently of the relative gravitational position between the exhaust opening 120 and the fluid port 116. Thus, for example, the drainage apparatus 130 is configured to function if the exhaust opening 120 is positioned gravitationally below the fluid port 116 of the port liner 115 (for example, as shown in Fig. 1 A, if gravity is along the -X direction, and also shown in Fig. 7) and the drainage apparatus is also configured to function if the exhaust opening is positioned gravitationally above the fluid port 116 of the port liner 115 (as shown in Fig. 6). Moreover, the drainage apparatus 130 can be made up of specific features of the array liner 109 and/or the fluid port 116 (such as shown in Fig. 7), depending on the relative gravitational position between the exhaust opening 120 and the fluid port 116. The drainage apparatus 130 is able to perform the function independently of the relative gravitational position between the exhaust opening 120 and the fluid port 116 because the array 105 of fins 106 has been moved to the exterior of the chamber 162 and the fluid port 116 still fluidly communicates with the interior 161 by way of the exhaust opening 120.

[0057] Details about the debris handling apparatus 100 are discussed next with reference to various implementations. [0058] Referring to Fig. 2, an implementation 200 of the debris handling apparatus 100 is shown mounted to the wall 170 of the chamber 162 (of an EUV radiation source 260 designed like the source 160) by way of a passage structure 222. In the debris handling apparatus 200, the linear array 105 of fins 106 is designed as an array 205 of fins 206 that have a v-shaped cross-section taken along a plane that includes the flow direction F and a direction perpendicular to the flow direction F (and are hereinafter referred to as “v-shaped fins”) 206. The design of the v-shaped fins 206 is shown more clearly in Figs. 3C and 3D, as discussed below. The array 205 of v-shaped fins 206 is arranged in a cavity 209c of an array liner 209 and is mounted to the array liner 209. The debris handling apparatus 200 also includes a port liner 215 defining a fluid opening or port 216, and, as discussed above, the port liner 215 and the array liner 209 are hermetically sealed to each other. The exhaust materials and debris from the interior 161 of the chamber 162 are sucked through an exhaust opening 220 of the wall 170 of the chamber 162, through a chamber passage 221 within the passage structure 222, and through an upstream side 217u of the fluid port 216. The exhaust materials and debris pass through the fluid port 216, through a downstream side 217d of the fluid port 216, and then through the array 205 of v-shaped fins 206.

[0059] Details of the array liner 209, the array 205, the port liner 215, and the fluid port 216 are discussed with reference to Figs. 3A-3E. An example of one fin 406 is shown in Figs. 4A-4C and an example of a pair of fins 506-8, 506-9 (within an array of a plurality of fins) is shown in Figs. 5A-5C. [0060] As shown in Figs. 2 and 3A-3E, the array liner 209 encloses the array 205 of v-shaped fins 206. Specifically, each of the fins 206 is mounted to the liner 209, as discussed below. Additionally, the array liner 209 is connected to the port liner 215 at interface 210 so as to form the hermetic seal. For example, the array liner 209 and the port liner 215 can include flanges that connect at the interface 210, and a gasket or O-ring can be fixed between the flanges to thereby provide the hermetic seal. [0061] The array liner 209 can be made of a material that is distinct from the material of the v- shaped fins 206. The array liner 209, the v-shaped fins 206, and the port liner 215 are made of materials that are not reactive to the material and debris that are to be captured by the debris handling apparatus 200. Thus, in the example above, if the targets 164 include tin, then the debris can include tin and the array liner 209, the v-shaped fins 206, and the port liner 215 are made of materials that are not reactive to tin. In some implementations, the array liner 209 and the port liner 215 are made of stainless steel. The v-shaped fins 206 can be made of a refractory metal or a metal alloy. For example, the v-shaped fins 206 can be made of molybdenum.

[0062] The v-shaped fins 206 are arranged relative to each other such that v-shaped grooves 324 are formed between pairs of adjacent fins of the array 205, as shown more clearly in Figs. 3C and 3D. The v-shape of the fins 206 and also the grooves 324 is also shown in Figs. 3C and 3D. A coordinate system of the array 205 is given by Xf, Yf, Zf, where Xf is along the flow direction F. As evident in Figs. 3C and 3D, the v-shape of the fins refers to the shape of the fins taken in cross section in the XfYf plane. In the example of Figs. 3A-3E the fins 206 include 18 v-shaped fins 306-1, 306-2, ... 306-18. However, the array 205 can include fewer than 18 fins or more than 18 fins. The groove 324 shown in Fig. 3D is the groove 324-8/9 between fins 306-8 and 306-9. Each v-shaped groove 324 includes an input groove passage and an output groove passage. In the example of Fig. 3D, the groove 324-8/9 includes an input groove passage 307i-8/9 and an output groove passage 307o-8/9. Each input groove passage 307i-8/9 fluidly faces the interior 161 of the chamber 162 which means that the input groove passage 307i-8/9 is on the side of the array 205 that is in fluid communication with the interior 161 of the chamber 162 (by way of the fluid port 116, the chamber passage 221, and the exhaust opening 220). Each output groove passage 307o-8/9 faces an exhaust pump, such as the exhaust pump 108 of the debris handling apparatus 100 of Fig. 1. This means that the output groove passage 307o- 8/9 is at the side of the array 205 that is in fluid communication with the exhaust pump 108. A flow direction F for the debris is defined from the input groove passage 307i-8/9 to the output groove passage 307o-8/9. The input groove passage 307i-8/9 and the output groove passage 307o-8/9 are planar surfaces, where the planes are positioned perpendicularly to the flow direction F.

[0063] As shown in Figs. 4A-4C, each v-shaped fin 406 includes a first segment 426s 1 and a second segment 426s2 that are arranged relative to each other at an obtuse angle <I> to thereby form the v-shape of the fin 406. For reference, a coordinate system Xf, Yf, Zf that is local to the fins 406 is shown. The axis Xf aligns with the flow direction F. The fins 406 are arranged relative to each other along the Yf axis. In particular, with reference to this local coordinate system, the first segment 426s 1 and the second segment 426s2 are angled relative to each other about an inflection line IE that is parallel with the Zf axis. This arrangement makes the fin 406 have a v-shape, as shown more clearly in Fig. 4C. A bend radius BR between the first segment 426s 1 and the second segment 426s2 can be greater than 1 millimeter (mm), such as, for example, 3 mm. In particular, due to this v-shape, an angle 01 is formed between the first segment 426s 1 and the flow direction F, and an angle 02 is formed between the second segment 426s2 and the flow direction F. Each angle 01, 02 is less than 20°. In some implementations, the angle 01 is identical to the angle 02 while in other implementations, the angle 01 is different from the angle 02. For example, each angle 01, 02 can be a value that is greater than 0° and less than 20°. As another example, each angle 01, 02 can be a value that is greater than 5° and less than 15°. In some implementations, each angle 01, 02 is a value in a range of 10° to 13°. In some implementations, each v-shaped fin 406 has a thickness T (Fig. 4C) that is between 1 to 3 millimeters (mm). In some implementations, a length L (Figs. 4B and 4C) of each v- shaped fin 406 (taken along the flow direction F) is at least 50 mm, at least 75 mm, at least 100 mm, or at least 120 mm.

[0064] As shown in Figs. 5A and 5C, a distance D between each adjacent fin may advantageously lie within a range of 9 to 20 mm. In the example of Figs. 5A and 5C, the distance D is shown between fins 506-8 and 506-9. Thus, because the fin 506-8 includes segments 526s 1-8 and 526s2-8 and the fin 506-9 includes segments 526s 1-9 and 526s2-9 (also shown in Fig. 5E), the distance D is given by the distance D between the segments 526sl-8 and 526sl-9 and the distance D between the segments 526s2-8 and 526s2-9 (Fig. 5C).

[0065] Referring back to Figs. 4A-4C, each v-shaped fin 406 is made up of a first sub-fin 427fl and a second sub-fin 427f2 that are stacked relative to each other along the Zf direction. The first subfin 427fl includes two upper portions of both segments 426s 1 and 426s2, and the second sub-fin 427f2 includes two lower portions of both segments 426s 1 and 426s2. An interface 428 between the first sub-fin 427fl and the second sub-fin 427f2 is linearly oriented at an angle relative to the flow direction F. The interface 428 is a gap or space between the first sub-fin 427fl and the second sub-fin 427f2. By splitting each fin 406 into the sub-fins 427fl, 427f2, installation of the array 405 can be simplified and distortion and high stresses due to thermal expansion can be reduced. Additionally, this interface 428 facilitates the navigation of the debris along the flow direction F toward the exhaust pump 108. As can be more clearly seen in Fig. 4B, this gap at the interface 428 extends along a direction (or directions) that is unparallel with the Xf direction; that is, the direction along which the gap at the interface 428 extends is not parallel with the Xf direction. Rather, the direction along which the gap at the interface 428 extends is skewed at an angle relative to the Xf direction. Because the interface 428 extends at a skewed angle relative to the Xf direction, any debris within a particular groove remains entrained within that groove as it passes through the groove and is less likely to pass through the interface 428 and into another adjacent groove.

[0066] Additionally, in order to facilitate mounting of the v-shaped fin 406 to the array liner 209, each v-shaped fin 406 includes a first extension 429el defined at the end of the first sub-fin 427fl farthest away from the interface 428 and a second extension 429e2 defined at the end of the second sub-fin 427f2 farthest away from the interface 428. The first extension 429el can be formed by a bent edge of the first sub-fin 427fl and the second extension 429e2 can be formed by a bent edge of the second sub-fin 427f2. These first and second extensions 429el, 429e2 can be flush with respective inner walls of the array liner 209 when properly mounted. The first and second extensions 429el, 429e2 can extend from the respective first and second sub-fins 427fl, 426f2 along the XfYf plane. [0067] The first sub-fin 427fl of each v-shaped fin 406 is mounted to a first upper wall 309wl of the array liner 209 by way of the first extension 429el at a first connection interface 43011. And, the second sub-fin 427f2 of each v-shaped fin 406 is mounted to a second lower wall 309w2 of the array liner 209 by way of the second extension 429e2 at a second connection interface 43012. This is shown generally in Fig. 3E and in more detail in Fig. 4B. Each connection interface 43011, 43012 can include a respective plurality of sub-connection interfaces 43211 j, 43212 j, where j is a set of integers. In the example of Fig. 4B, the connection interface 43011 includes sub-connection interfaces 432I1_1, 432I1_2, 432I1_3, 432I1_4 and the connection interface 43012 includes sub-connection interfaces 432I2_1, 432I2_2, 432I2_3, 432I2_4. In other implementations, each connection interface 43011, 43012 can include fewer than four or more than four sub-connection interfaces. [0068] As shown in Figs. 4A-4C, each v-shaped fin 406 includes a concave beveled edge 435 at the input groove passage of the adjacent v-shaped groove. The input groove passage of the adjacent v- shaped groove is positioned along the -Xf direction relative to the output groove passage of the adjacent v-shaped groove because the flow direction F aligns with the +Xf direction. This concave beveled edge 435 is formed with two beveled edges in the second segment 426s2 such that a notch on each fin faces the fluid port 216 (Figs. 2, 3A, and 3B). In particular, the concave beveled edge 435 is the result of the absence of material of a portion of the first sub-fin 427fl in the second segment 426s2 and a portion of the second sub-fin 427f2 in the second segment 426s2 near the location of the interface 428. This concave beveled edge 435 is formed for the following reasons. Specifically, the temperature of the debris flow that approaches the array of fins 406 is much colder than the melting temperature of the material of the debris and the target material, and, as noted above, the fins 406 are maintained at the temperature above the melting point of the material of the debris. This low temperature flow would cool a leading edge (the edge that faces the fluid port 216) of the fins, and make it difficult to achieve a melt temperature of the debris and/or target material with a reasonable heater power at the array of fins 406. By introducing the concave beveled edge 435, and thus removing a portion of the leading edge that is most exposed to the cold flow, the temperature of the fin 406 remains above the melting temperature of the debris and/or target material, even with these lower temperature flows that approach the fins 406. On the other side of the fin 406, in some implementations as shown in Figs. 4A-4C, a convex beveled edge 437 can be formed at the output groove passage of the adjacent groove.

[0069] In other implementations, as shown in Figs. 5A-5E, adjacent pairs of v-shaped fins within the array 205 are mounted together in and at the array liner 209 at the same connection interfaces. In the example of Figs. 5A-5E, the pair of v-shaped fins 506-8 and 506-9 are shown mounted together. As evident, the v-shaped fins 506-8 and 506-9 are offset from each other along the Yf axis. Each v- shaped fin 506-8 and 506-9 is made up of a respective first sub-fin 527fl-8, 527fl-9 and a respective second sub-fin 527f2-8, 527f2-9 that are stacked relative to each other along the Zf direction (see Fig. 5E). The first sub-fin 527fl-8, 527fl-9 includes two upper portions of both segments 526sl-8 and 526s2-8, 526s 1-9 and 526s2-9, respectively. And, the second sub-fin 527f2-8, 527f2-9 includes two lower portions of both segments 526sl-8 and 526s2-8, 526sl-9 and 526s2-9, respectively. An interface 528-8 (which can be a gap or a space) is formed between the first sub-fin 527fl-8 and the second sub-fin 527f2-8 and an interface 528-9 (which can be a gap or a space) is formed between the first sub-fin 527fl-9 and the second sub-fin 527f2-9. These interfaces 528-8 and 528-9 are similar to the interface 428 and thus are each linearly oriented at an angle relative to the flow direction F in order to facilitate the navigation of the debris along the flow direction F toward the exhaust pump 108. Additionally, each v-shaped fin 506-8 and 506-9 includes a concave beveled edge 535-8 and 535-9 at the input groove passage of the adjacent v-shaped groove, and this concave beveled edge 535-8 and 535-9 acts similarly to the concave beveled edge 435 discussed above. [0070] The v-shaped fins 506-8 and 506-9 are paired up and mounted to the array liner 209 together at connection interfaces 53011 and 53012 (Figs. 5B and 5D). Other fins within the array 205 can be mounted similarly to the fins 506-8 and 506-9. For example, the connection interface 53011 can include a plurality of sub-connection interfaces 53211 j, where j is a set of integers 1, 2, 3, 4, and the connection interface 53012 can include a plurality of sub-connection interfaces 532I2_j, where j is a set of integers 1, 2, 3, 4. In order to facilitate the pairing of the adjacent v-shaped fins 506-8, 506-9 for mounting, the v-shaped fin 506-8 includes a first extension 529el-8 at the first connection interface 53011, and the v-shaped fin 506-9 includes a first extension 529el-9 at the first connection interface 53011. The v-shaped fin 506-8 also includes a second extension 529e2-8 at the second connection interface 53012, and the v-shaped fin 506-9 includes a second extension 529e2-9 at the second connection interface 53012. To assemble the v-shaped fins 506-8 and 506-9 into the array liner 209, the first extensions 529el-8 and 529el-9 are stacked or nested together and the second extensions 529e2-8 and 529e2-9 are stacked or nested together. This is shown more clearly in Figs. 5A and 5B. Once these extensions are stacked, they can then be fixed together and also to the array liner 209 using a connection mechanism. The connection mechanism is demountable, which means that after the extensions are fixed together and to the array liner 209, they can be disconnected later without damaging the components. In this particular example, the first connection interface 53011 includes the sub-connection interfaces 532I1_1, 532I1_2, 532I1_3, 532I1_4, and the second connection interface 53012 includes the sub-connection interfaces 532I2_1, 532I2_2, 532I2_3, 532I2_4. Each sub-connection interface includes a connection mechanism that connects or fixes the extensions to the array liner 209.

[0071] An implementation of the connection mechanism at the sub-connection interface 532I1_3 is shown in Fig. 5D, noting that, in this implementation, the other connection mechanisms are designed in this same manner. As shown in Fig. 5D, the connection mechanism at the sub-connection interface 532I1_3 includes a bolt 531 through an opening within the first upper wall 309wl of the array liner 209 and openings within the first extensions 529el-8, 529el-9 of the respective v-shaped fins 506-8, 506-9. The openings within the first extensions 529el-8, 529el-9 at the sub-connection interface 532I1_3 are labeled as 536-8 and 536-9, respectively, in Fig. 5E. The connection mechanism at the sub-connection interface 532I1_3 also includes a nut 533 and a spring washer 534. The spring washer 534 can be configured to compensate for any mismatches in thermal expansion between the wall 309wl, the first extension 529el-9, and the first extension 529el-8, yet still provide the needed clamping force between the fins 506-8, 506-9 and the wall 309wl.

[0072] Referring to Fig. 6, in some implementations, a debris handling apparatus 600 (designed like the debris handling apparatus 100) is arranged relative to an EUV radiation source 660 in which the exhaust opening 620 is positioned gravitationally above the fluid port 616 of the port liner 615. The direction of gravity is represented by the arrow G. In these implementations, the drainage apparatus includes a drainage port 642 in fluid communication with the output groove passages 607o of the grooves 607 of the linear array 605 of fins 606. The paths of drainage is represented by the arrows 640. For comparison, the path with which debris is removed from the interior 661 of the chamber (or vessel) 662 is depicted by the arrows 671.

[0073] Referring to Fig. 7, in some implementations, a debris handling apparatus 700 (designed like the debris handling apparatus 100 or 200) is arranged relative to an EUV radiation source 760 in which the exhaust opening 720 is positioned gravitationally below the fluid port 716 of the port liner 715. The direction of gravity is represented by the arrow G. In these implementations, the drainage apparatus includes the fluid port 716 of the port liner 715 and at least a portion of the exterior chamber passage 721. Drainage continues through an opening 744 within the passage structure 722 out of the exterior chamber passage 721. The path of drainage is represented by the arrow 740. On the other hand, the path with which debris is removed from the interior 761 of the chamber (or vessel) 762 is depicted by the arrows 771.

[0074] Referring again to Fig. 1, the debris handling apparatus 100 can also include the heater 141 configured to maintain a temperature of the fins 106 above a melting point of the material of the debris and/or the target material. Referring to Fig. 8, an implementation 841 of the heater is shown. The heater 841 is in thermal contact with the array liner 209 and the port liner 215. In other implementations, the heater 841 is in thermal contact with only the array liner 209. The heater 841 can be formed of any suitable heating element such as a resistive wire that is shaped to fit into grooves at an exterior surface of the array liner 209 (and/or the port liner 215). The array liner 209 and the port liner 215 can be formed from sheet metal that is bent and then welded together, brazed, and optionally coated with titanium nitride (for example, by way of chemical vapor deposition).

[0075] The implementation can be further described using the following clauses.

1. A debris handling apparatus for controlling debris within a controlled-environment chamber of an extreme ultraviolet (EUV) radiation source, the debris handling apparatus comprising: an array of v-shaped fins, with the fins arranged relative to each other such that v-shaped grooves are formed between pairs of adjacent fins of the array, each v-shaped fin including two segments arranged at an obtuse angle from each other, and each v-shaped groove including an input groove passage facing an interior of the chamber and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage; wherein an angle between each segment and the flow direction is less than 20°.

2. The debris handling apparatus of clause 1, wherein each v-shaped fin has a thickness in the range of 1-3 mm.

3. The debris handling apparatus of clause 1, wherein a distance between each adjacent fin is in a range of 9 to 20 millimeters (mm) and a length of each v-shaped fin along the flow direction is at least 50 mm, at least 75 mm, at least 100 mm, or at least 120 mm.

4. The debris handling apparatus of clause 1, wherein each v-shaped fin is made up of a first sub-fin and a second sub-fin. 5. The debris handling apparatus of clause 4, wherein an interface between the first sub-fin and the second sub-fin includes a portion linearly oriented at an angle relative to the flow direction.

6. The debris handling apparatus of clause 4, further comprising a liner in which the array of v- shaped fins is mounted.

7. The debris handling apparatus of clause 6, wherein the first sub-fin is mounted to a first wall of the liner and the second sub-fin is mounted to a second wall of the liner.

8. The debris handling apparatus of clause 6, wherein the liner comprises a different material than the material of the v-shaped fins.

9. The debris handling apparatus of clause 6, wherein the liner is made of stainless steel and the v- shaped fins are made of molybdenum.

10. The debris handling apparatus of clause 6, wherein adjacent pairs of v-shaped fins are mounted together to the liner at the same connection interface.

11. The debris handling apparatus of clause 6, wherein the v-shaped fins are each mounted to the liner at a plurality of connection interfaces, with each connection interface including a bolt through the liner and the v-shaped fins, a nut, and a spring washer.

12. The debris handling apparatus of clause 1, wherein each v-shaped fin includes a concave beveled edge at the input groove passage of the adjacent v-shaped groove.

13. The debris handling apparatus of clause 1, further comprising a drainage apparatus in fluid communication with the v-shaped grooves, the drainage apparatus configured to remove debris collected by the array of v-shaped fins.

14. The debris handling apparatus of clause 1, wherein each v-shaped fin comprises a refractory metal or a metal alloy.

15. The debris handling apparatus of clause 1, wherein an angle between each segment and the flow direction is greater than 0° and less than 20°; greater than 5° and less than 15°; or greater than 10° and less than 13°.

16. A debris handling apparatus for controlling debris within a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source in which produced EUV light is transmitted along an optical axis within the chamber interior, the debris handling apparatus comprising: a linear array of fins, the fins arranged relative to each other such that grooves are formed between adjacent fins of the array, each groove including an input groove passage and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage; and a port liner defining a fluid port that includes an upstream side positioned exterior to the chamber and in fluid communication with the chamber interior, and a downstream side adjacent to and in fluid communication with the input groove passages.

17. The debris handling apparatus of clause 16, wherein the flow direction is the same for all of the grooves. 18. The debris handling apparatus of clause 16, wherein the upstream side of the port liner is in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber.

19. The debris handling apparatus of clause 18, wherein the chamber passage has an annular shape and extends around an outer circumference of the chamber exterior.

20. The debris handling apparatus of clause 18, wherein the upstream side of the port liner is positioned at an angle about the outer circumference of the chamber exterior at least 90° away from the exhaust opening.

21. The debris handling apparatus of clause 16, further comprising a drainage apparatus configured to drain debris collected in the linear array of fins away from the linear array of fins.

22. The debris handling apparatus of clause 21, wherein: the upstream side of the port liner is in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber, and the exhaust opening is positioned gravitationally below the fluid port of the port liner, and the drainage apparatus includes the fluid port of the port liner and at least a portion of the chamber passage; or the exhaust opening is positioned gravitationally above the fluid port of the port liner, and the drainage apparatus includes a drainage port in fluid communication with the output groove passages.

23. The debris handling apparatus of clause 16, wherein the EUV light is transmitted from a primary focus to a secondary focus along the optical axis within the chamber interior and neither the primary focus nor the secondary focus is in the sight line of the upstream side of the fluid port.

24. The debris handling apparatus of clause 16, wherein each fin is a v-shaped fin including two segments arranged at an obtuse angle from each other, and each groove is a v-shaped groove.

25. The debris handling apparatus of clause 24, wherein each v-shaped fin is made up of a first subfin and a second sub-fin.

26. The debris handling apparatus of clause 16, further comprising an array liner in which the array of fins is mounted, the array liner and the port liner being hermetically connected.

27. The debris handling apparatus of clause 16, wherein each fin comprises a first sub-fin and a second sub-fin that are disconnected from each other.

28. The debris handling apparatus of clause 27, further comprising an array liner in which the array of fins is mounted, wherein the first sub-fin is mounted to a first wall of the array liner by way of a demountable connection and the second sub-fin is mounted to a second wall of the array liner by way of a demountable connection.

29. The debris handling apparatus of clause 27, wherein a gap between the first sub-fin and the second sub-fin extends along a direction that is unparallel with an edge of the first sub-fin that is mounted to the first wall.

30. The debris handling apparatus of clause 29, wherein the extent of the gap along a direction perpendicular to the flow direction is generally constant throughout the gap. 31. The debris handling apparatus of clause 16, wherein each fin includes a concave beveled edge at the input groove passage of the adjacent groove.

32. The debris handling apparatus of clause 31, wherein the concave beveled edge is formed with two beveled edges that define a notch facing the fluid port.

33. The debris handling apparatus of clause 31, wherein each fin includes a convex beveled edge at the output groove passage of the adjacent groove.

34. The debris handling apparatus of clause 16, further comprising a heater configured to maintain a temperature of the fins above a melting point of the debris produced during production of the EUV light-

35. The debris handling apparatus of clause 34, further comprising an array liner in which the array of fins is mounted, wherein the heater is in thermal contact with the array liner and the port liner.

36. The debris handling apparatus of clause 16, wherein each fin comprises a refractory metal or a metal alloy.

37. An extreme ultraviolet (EUV) radiation source vessel comprising: a chamber including one or more walls that define a chamber interior, wherein a primary focus at which plasma is created from a light pulse interacting with a target and a secondary focus at which EUV radiation produced by the plasma is focused are in the chamber interior and, in use, EUV light is transmitted from the primary focus to the secondary focus along an optical axis; a control system configured to maintain a temperature of the chamber and the chamber interior below a melting point of material of the target and to flow a purge gas away from the primary focus; a debris handling apparatus including a fluid port positioned exterior to the chamber and including an upstream side in fluid communication with the chamber interior, and a downstream side in fluid communication with a debris capture array; and an exhaust opening fluidly communicating with the chamber interior at a first end and the upstream side of the fluid port at a second end.

38. The EUV radiation source vessel of clause 37, wherein the control system is configured to maintain a temperature of at least a portion of the debris handling apparatus above the melting point of the material of the target and a material of debris produced within the chamber interior.

39. A method of handling debris produced in a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source, the method comprising: passing a flow of gas through an exhaust opening in a wall of the chamber, including directing the flow of gas from the chamber interior through the exhaust opening to an exterior to the chamber; directing the flow of gas from the exhaust opening to a debris handling apparatus exterior to the chamber; collecting debris within the flow of gas at the debris handling apparatus; and draining debris collected by the debris handling apparatus through a drainage apparatus. 40. The method of clause 39, wherein directing the flow of gas from the chamber interior through the exhaust opening comprises directing the flow of gas from a collector in the chamber interior to the exhaust opening.

41. The method of clause 39, wherein directing the flow of gas from the exhaust opening to the debris handling apparatus exterior to the chamber comprises passing the flow of gas around at least a portion of an outer circumference of the chamber through a chamber passage exterior to an upstream side of a fluid port of the debris handling apparatus.

42. The method of clause 39, wherein collecting debris within the flow of gas at the debris handling apparatus comprises passing debris through an input groove passage of a plurality of grooves formed between pairs of adjacent fins in a linear array of fins, and collecting debris within at least some of the grooves.

43. The method of clause 42, wherein draining the debris collected by the debris handling apparatus comprises navigating the flow of debris away through each respective groove, and entraining the debris within the respective groove.

44. The method of clause 42, wherein draining the debris collected by the debris handling apparatus comprises passing the collected debris along a drain path that overlaps a gas path along which the flow of gas is directed or draining the debris collected by the debris handling apparatus comprises passing the collected debris along a drain path that is separate from a gas path along which the flow of gas is directed.

45. The method of clause 39, further comprising compensating for thermal expansion mismatch between a liner in which the fins are mounted and the fins.

46. The method of clause 39, wherein directing the flow of gas from the exhaust opening to the debris handling apparatus exterior to the chamber comprises directing the flow of gas along a single path to the debris handling apparatus.

47. A debris handling apparatus for controlling debris within a controlled-environment chamber of an extreme ultraviolet (EUV) radiation source, the debris handling apparatus comprising: an array of v-shaped fins arranged relative to each other such that v-shaped grooves are formed between adjacent fins of the array, wherein: each v-shaped fin includes two segments arranged at an obtuse angle from each other, and each v- shaped groove including an input groove passage facing an interior of a chamber and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage; and each v-shaped fin includes a concave beveled edge at the input groove passage of the adjacent v- shaped groove.

48. The debris handling apparatus of clause 47, wherein the concave beveled edge is formed with two beveled edges that define a notch facing the chamber interior. 49. The debris handling apparatus of clause 47, wherein each v-shaped fin includes a convex beveled edge at the output groove passage of the adjacent v-shaped groove.

50. The debris handling apparatus of clause 47, further comprising a heater configured to maintain a temperature of the v-shaped fins above a melting point of the material in the debris. 51. The debris handling apparatus of clause 50, further comprising a liner in which the array of v- shaped fins is mounted, wherein the heater is in thermal contact with the liner.

[0076] The above-described implementations and other implementations are within the scope of the following claims.

Claims

2. The debris handling apparatus of claim 1, wherein each v-shaped fin has a thickness in the range of 1-3 mm.

3. The debris handling apparatus of claim 1, wherein a distance between each adjacent fin is in a range of 9 to 20 millimeters (mm) and a length of each v-shaped fin along the flow direction is at least 50 mm, at least 75 mm, at least 100 mm, or at least 120 mm.

4. The debris handling apparatus of claim 1, wherein each v-shaped fin is made up of a first subfin and a second sub-fin.

5. The debris handling apparatus of claim 4, wherein an interface between the first sub-fin and the second sub-fin includes a portion linearly oriented at an angle relative to the flow direction.

6. The debris handling apparatus of claim 4, further comprising a liner in which the array of v- shaped fins is mounted.

7. The debris handling apparatus of claim 6, wherein the first sub-fin is mounted to a first wall of the liner and the second sub-fin is mounted to a second wall of the liner.

8. The debris handling apparatus of claim 6, wherein the liner comprises a different material than the material of the v-shaped fins.

9. The debris handling apparatus of claim 6, wherein the liner is made of stainless steel and the v-shaped fins are made of molybdenum.

10. The debris handling apparatus of claim 6, wherein adjacent pairs of v-shaped fins are mounted together to the liner at the same connection interface.

11. The debris handling apparatus of claim 6, wherein the v-shaped fins are each mounted to the liner at a plurality of connection interfaces, with each connection interface including a bolt through the liner and the v-shaped fins, a nut, and a spring washer.

12. The debris handling apparatus of claim 1, wherein each v-shaped fin includes a concave beveled edge at the input groove passage of the adjacent v-shaped groove.

13. The debris handling apparatus of claim 1, further comprising a drainage apparatus in fluid communication with the v-shaped grooves, the drainage apparatus configured to remove debris collected by the array of v-shaped fins.

14. The debris handling apparatus of claim 1, wherein each v-shaped fin comprises a refractory metal or a metal alloy.

15. The debris handling apparatus of claim 1, wherein an angle between each segment and the flow direction is greater than 0° and less than 20°; greater than 5° and less than 15°; or greater than 10° and less than 13°.

17. The debris handling apparatus of claim 16, wherein the flow direction is the same for all of the grooves.

18. The debris handling apparatus of claim 16, wherein the upstream side of the port liner is in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber.

19. The debris handling apparatus of claim 18, wherein the chamber passage has an annular shape and extends around an outer circumference of the chamber exterior.

20. The debris handling apparatus of claim 18, wherein the upstream side of the port liner is positioned at an angle about the outer circumference of the chamber exterior at least 90° away from the exhaust opening.

21. The debris handling apparatus of claim 16, further comprising a drainage apparatus configured to drain debris collected in the linear array of fins away from the linear array of fins.

22. The debris handling apparatus of claim 21, wherein: the upstream side of the port liner is in fluid communication with an exhaust opening in a wall of the chamber by way of a chamber passage exterior to the chamber, and the exhaust opening is positioned gravitationally below the fluid port of the port liner, and the drainage apparatus includes the fluid port of the port liner and at least a portion of the chamber passage; or the exhaust opening is positioned gravitationally above the fluid port of the port liner, and the drainage apparatus includes a drainage port in fluid communication with the output groove passages.

23. The debris handling apparatus of claim 16, wherein the EUV light is transmitted from a primary focus to a secondary focus along the optical axis within the chamber interior and neither the primary focus nor the secondary focus is in the sight line of the upstream side of the fluid port.

24. The debris handling apparatus of claim 16, wherein each fin is a v-shaped fin including two segments arranged at an obtuse angle from each other, and each groove is a v-shaped groove.

25. The debris handling apparatus of claim 24, wherein each v-shaped fin is made up of a first sub-fin and a second sub-fin.

26. The debris handling apparatus of claim 16, further comprising an array liner in which the array of fins is mounted, the array liner and the port liner being hermetically connected.

27. The debris handling apparatus of claim 16, wherein each fin comprises a first sub-fin and a second sub-fin that are disconnected from each other.

28. The debris handling apparatus of claim 27, further comprising an array liner in which the array of fins is mounted, wherein the first sub-fin is mounted to a first wall of the array liner by way of a demountable connection and the second sub-fin is mounted to a second wall of the array liner by way of a demountable connection.

29. The debris handling apparatus of claim 27, wherein a gap between the first sub-fin and the second sub-fin extends along a direction that is unparallel with an edge of the first sub-fin that is mounted to the first wall.

30. The debris handling apparatus of claim 29, wherein the extent of the gap along a direction perpendicular to the flow direction is generally constant throughout the gap.

31. The debris handling apparatus of claim 16, wherein each fin includes a concave beveled edge at the input groove passage of the adjacent groove.

32. The debris handling apparatus of claim 31, wherein the concave beveled edge is formed with two beveled edges that define a notch facing the fluid port.

33. The debris handling apparatus of claim 31, wherein each fin includes a convex beveled edge at the output groove passage of the adjacent groove.

34. The debris handling apparatus of claim 16, further comprising a heater configured to maintain a temperature of the fins above a melting point of the debris produced during production of the EUV light-

35. The debris handling apparatus of claim 34, further comprising an array liner in which the array of fins is mounted, wherein the heater is in thermal contact with the array liner and the port liner.

36. The debris handling apparatus of claim 16, wherein each fin comprises a refractory metal or a metal alloy.

38. The EUV radiation source vessel of claim 37, wherein the control system is configured to maintain a temperature of at least a portion of the debris handling apparatus above the melting point of the material of the target and a material of debris produced within the chamber interior.

39. A method of handling debris produced in a controlled-environment interior of a chamber of an extreme ultraviolet (EUV) radiation source, the method comprising: passing a flow of gas through an exhaust opening in a wall of the chamber, including directing the flow of gas from the chamber interior through the exhaust opening to an exterior to the chamber; directing the flow of gas from the exhaust opening to a debris handling apparatus exterior to the chamber; collecting debris within the flow of gas at the debris handling apparatus; and draining debris collected by the debris handling apparatus through a drainage apparatus.

40. The method of claim 39, wherein directing the flow of gas from the chamber interior through the exhaust opening comprises directing the flow of gas from a collector in the chamber interior to the exhaust opening.

41. The method of claim 39, wherein directing the flow of gas from the exhaust opening to the debris handling apparatus exterior to the chamber comprises passing the flow of gas around at least a portion of an outer circumference of the chamber through a chamber passage exterior to an upstream side of a fluid port of the debris handling apparatus.

42. The method of claim 39, wherein collecting debris within the flow of gas at the debris handling apparatus comprises passing debris through an input groove passage of a plurality of grooves formed between pairs of adj cent fins in a linear array of fins, and collecting debris within at least some of the grooves.

43. The method of claim 42, wherein draining the debris collected by the debris handling apparatus comprises navigating the flow of debris away through each respective groove, and entraining the debris within the respective groove.

44. The method of claim 42, wherein draining the debris collected by the debris handling apparatus comprises passing the collected debris along a drain path that overlaps a gas path along which the flow of gas is directed or draining the debris collected by the debris handling apparatus comprises passing the collected debris along a drain path that is separate from a gas path along which the flow of gas is directed.

45. The method of claim 39, further comprising compensating for thermal expansion mismatch between a liner in which the fins are mounted and the fins.

46. The method of claim 39, wherein directing the flow of gas from the exhaust opening to the debris handling apparatus exterior to the chamber comprises directing the flow of gas along a single path to the debris handling apparatus.

47. A debris handling apparatus for controlling debris within a controlled-environment chamber of an extreme ultraviolet (EUV) radiation source, the debris handling apparatus comprising: an array of v-shaped fins arranged relative to each other such that v-shaped grooves are formed between adjacent fins of the array, wherein: each v-shaped fin includes two segments arranged at an obtuse angle from each other, and each v-shaped groove including an input groove passage facing an interior of a chamber and an output groove passage facing an exhaust pump such that a flow direction is defined from the input groove passage to the output groove passage; and each v-shaped fin includes a concave beveled edge at the input groove passage of the adjacent v-shaped groove.

48. The debris handling apparatus of claim 47, wherein the concave beveled edge is formed with two beveled edges that define a notch facing the chamber interior.

49. The debris handling apparatus of claim 47, wherein each v-shaped fin includes a convex beveled edge at the output groove passage of the adjacent v-shaped groove.

50. The debris handling apparatus of claim 47, further comprising a heater configured to maintain a temperature of the v-shaped fins above a melting point of the material in the debris.

51. The debris handling apparatus of claim 50, further comprising a liner in which the array of v- shaped fins is mounted, wherein the heater is in thermal contact with the liner.