Conduit structure and extreme ultraviolet (EUV) radiation source

Abstract

This invention discloses a conduit structure for an EUV system, wherein a non-horizontal internal surface of the conduit has flow barriers that impede the flow of molten target material across the surface, causing the molten target material to freeze and be captured by the internal surface. In cases where the conduit is a conduit through which droplets of target material pass from an EUV chamber, the flow barriers on the sides of the conduit ensure that molten target material initially captured by an upper surface of the conduit and flowing to a sidewall adheres to the sidewall and is diverted from the actual droplet path. This ensures that an opening in the conduit is maintained, thereby allowing the intended flow. For example, the conduit structure can be placed between the interior of a chamber generating EUV radiation and a target material container.

Description

[Technical Field]

[0001] This invention relates to an apparatus for generating extreme ultraviolet ("EUV") radiation from plasma generated by changing the state of a target material. In these applications, optical elements are used, for example, to collect and guide EUV radiation for use in semiconductor photolithography. [Previous Technology]

[0002] EUV radiation (e.g., electromagnetic radiation having wavelengths of about 50 nm or less (sometimes referred to as soft X-rays) and including radiation with wavelengths of about 13.5 nm) is used in photolithography processes to produce minute features in substrates such as silicon wafers. Here and elsewhere in this document, the term "light" is used to understand that the radiation described may not be in the visible portion of the spectrum.

[0003] Methods for generating EUV radiation include converting a target material into a plasma state. The target material preferably comprises at least one element having one or more emission lines in the EUV portion of the electromagnetic spectrum, such as xenon, lithium, or tin. The target material can be solid, liquid, or gas. In one such method, commonly referred to as laser-generated plasma (“LPP”), the desired plasma can be generated by irradiating a target material having the desired spectral emission element using a laser beam.

[0004] An LPP technology relates to generating a stream of target droplets and irradiating at least some of the droplets with one or more laser radiation pulses. The droplet stream is generated by a droplet generator.

[0005] The process of changing the target material results in the deposition of residual target material on various surfaces, where an unobstructed path exists between the irradiation site and the surface. Such deposition also occurs on surfaces exposed to the gas flow carrying the residual target material. These surfaces include blades, exhaust ports, and exhaust paths. If the target material is tin, this can lead to the growth of tin fluff, which can fall onto the collector optics and block exhaust and exhaust paths. Tin is used herein as an example of a specific target material, and it is understood that other types of targets can be used and may present the same or similar management problems.

[0006] A technique for controlling tin accumulation involves capturing tin with vapor or particles on a collection surface heated to above the melting point of tin. On such heated collection surfaces, the tin melts (or remains molten) and flows to a capture container. However, liquid tin tends to eject or "sputter" in the presence of hydrogen radicals, such as those found in EUV chambers, and this ejected tin can impact the collector.

[0007] Furthermore, liquid tin often does not flow as intended. For example, the structure within the chamber, such as the blades and grooves of a scrubber provided to remove some or all of the tin vapor from the chamber, can cause liquid tin to drip onto the collector. Liquid tin can also create thermal short circuits, i.e., unintended heat conduction paths. In addition, liquid tin is highly corrosive and can cause malfunctions, for example, in electric heaters used to maintain the collection surface above the melting point of tin.

[0008] One chamber feature requiring special attention is a tin trap or container positioned to receive and store unused tin droplets for subsequent removal. Unused droplets occur, for example, in systems where light generation is enabled or disabled by interrupting or redirecting laser pulses that would otherwise convert the droplets rather than interrupting their generation. Measures must be taken to control and contain unused tin, preferably without disrupting the vacuum within the chamber. Structures through which droplets pass as they exit the chamber are prone to tin accumulation in the form of tin fluff or threads. This structure can be implemented as a conduit structure in an insert within a collector ring, as described below. Ultimately, this tin accumulation can obstruct the discharge path of unused tin droplets.

[0009] Therefore, there is a need to manage residual target material so that it does not obstruct the orifices in the source chamber, including the inlet of the tin trap. In this context, the need arises for the subject matter disclosed in this invention. [Summary of the Invention]

[0010] The following presents a brief overview of one or more embodiments to provide a basic understanding of the disclosed subject matter. This overview is not an extensive summary of all the embodiments covered. It is not intended to make any particular element singlely critical or decisive for any embodiment, nor to set a limitation on the scope of implementation of any or all embodiments. Its sole purpose is to present some concepts in a streamlined form as an introduction to the more detailed description that follows.

[0011] According to one embodiment, an internal surface of a conduit structure for an EUV system has flow barriers that impede the flow of molten target material across a non-horizontal surface of the conduit structure, causing the molten target material to freeze on and be captured by the internal surface. The conduit structure may be placed, for example, between the interior of a chamber that generates EUV radiation and a target material container, in which case the internal surface is a side surface of the conduit structure.

[0012] According to another embodiment, a conduit structure is disclosed, which is adapted to be placed in fluid communication with an interior of a chamber for an EUV radiation source, in which a target is transformed, the conduit structure including at least one sidewall facing the interior of the conduit structure, at least a portion of the sidewall having a plurality of flow barriers configured to impede the flow of the molten target across a plurality of flow barriers.

[0013] The conduit structure may include a plate configured to cover at least a portion of the sidewall, on which the plurality of flow obstructions are disposed. The plurality of flow obstructions may include a plurality of unidirectional ridges extending at least partially through the conduit structure in a first direction. One of the ridges may be discontinuous. The ridges may extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction.

[0014] According to another embodiment, an EUV radiation source is disclosed, comprising a chamber of an EUV target, the chamber having at least one conduit structure having a surface exposed to the EUV target, wherein a first portion of the surface is disposed at a location where the molten target encounters the first portion of the surface, and gravity will tend to pull the molten target downward in a first direction across the first portion of the surface, and a second portion below the first portion of the surface has a plurality of flow barriers configured to impede the flow of the molten target across the second portion in the first direction.

[0015] The surface may include a plate insert comprising the plurality of flow barriers. The plate insert may be maintained at a temperature below the melting temperature of one of the target materials. The target material may be tin, and the plate insert may be maintained at a temperature not exceeding approximately 200°C.

[0016] The plurality of flow obstacles may comprise a plurality of unidirectional ridges extending in a second direction substantially perpendicular to the first direction. One of the uppermost ridges may be discontinuous. The ridges may extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the second direction alternates with a second group of straight segments angled at a second angle relative to the second direction. The discontinuity of one of the uppermost ridges defines a plurality of gaps passing through it.

[0017] The EUV radiation source may further include a cooling flow ring at least partially arranged around a circumference of a collector mirror located in the chamber, the conduit structure being positioned in the cooling flow ring to provide a path between the interior of the chamber and a target container.

[0018] The plurality of flow obstacles may comprise a plurality of substantially circular indentations. The plurality of flow obstacles may comprise a plurality of substantially rectangular indentations. The plurality of substantially rectangular indentations may extend along the same length as one of the second portions of the surface. The plurality of substantially rectangular indentations may be arranged in an array of columns and rows.

[0019] The plurality of flow obstacles may include a plurality of angled blades located on the second portion. The plurality of flow obstacles may include a plurality of elongated slits extending perpendicular to the first direction, wherein each slit has an associated groove portion. At least a portion of the surface may be roughened.

[0020] The EUV radiation source may further include a top surface element that is adjacent to and angled relative to the surface and is adapted and configured to allow molten target material collected on the top surface element to flow out of the top surface element and onto the surface.

[0021] According to another embodiment, an EUV radiation source is disclosed, which includes a chamber and a target container in fluid communication with the interior of one of the chambers via a conduit, the conduit including a target collection plate positioned to at least partially cover the interior surface of one of the conduits, the target collection plate including the plurality of structures that impede the flow of molten target material across one of the plurality of structures, thereby causing the molten target material to solidify on the target collection plate.

[0022] According to another embodiment, an EUV radiation source is disclosed, comprising a chamber including a surface exposed at a location of a residual target during EUV radiation generation, the source including a target collection plate that at least partially covers the surface, the target collection plate being maintained at a temperature below the melting temperature of the target, the target collection plate including a plurality of flow barriers, the target collection plate being oriented such that gravity pulls the molten target across the flow barriers and the flow barriers being oriented to impede the flow of the molten target.

[0023] According to another embodiment, a conduit structure is disclosed, adapted for placement in fluid communication with the interior of a chamber for an extreme ultraviolet (EUV) radiation source, in which a target material is transformed. The conduit structure includes: at least one sidewall facing the interior of the conduit structure, the at least one sidewall having a first sidewall edge extending in a first direction and at least a portion of the sidewall having a plurality of flow barriers substantially extending in the first direction and configured to impede flow of molten target material across that portion of the sidewall in a second direction different from the first direction. The conduit structure also includes a top wall facing the interior of the conduit structure, the top wall being configured to have a top wall edge extending substantially parallel to the first sidewall edge in the first direction, the top wall edge having a plurality of edge features configured to inhibit flow of target material along the top wall edge in the first direction.

[0024] The top wall may come into thermal contact with a heat source such that the top wall reaches a temperature greater than the melting temperature of one of the target materials. The plurality of edge features may include a plurality of recesses. The plurality of recesses may be arranged in a linear array. Each recess may be substantially triangular, wherein one base of the recess is located at the edge of the top wall.

[0025] Each recess may have a tin-repellent material layer. At least a portion of one surface of the top wall other than the surfaces of the recesses has a tin-loving material layer. The entire surface of the top wall other than the surfaces of the recesses may be covered with a tin-loving material layer.

[0026] The conduit structure may further include a heating element that is in thermal contact with at least a portion of the top wall and is configured to maintain at least a portion of the top wall at a first temperature. The heating element may be configured to maintain a first portion of the top wall at the first temperature and a second portion of the top wall at a second temperature different from the first temperature.

[0027] According to another embodiment, an extreme ultraviolet (EUV) radiation source is disclosed, comprising a chamber modified from an EUV target, the chamber having at least one conduit structure, the conduit structure including a transverse side surface exposed to the EUV target, wherein a first portion of the transverse side surface is disposed at a location where a molten target encounters the first portion of the transverse side surface and is configured such that gravity will tend to pull the molten target downward across the first portion of the transverse side surface in a first direction, and a second portion of the transverse side surface below the first portion having a plurality of flow barriers is configured to impede the flow of the molten target across the second portion in the first direction, the transverse side surface having a first transverse side surface edge extending in a second direction. The conduit structure further includes a top wall facing the interior of the conduit structure, the top wall being configured to have a top wall edge extending substantially parallel to the first transverse side surface edge in the second direction, the top wall edge having a plurality of edge features configured to inhibit the flow of the target along the top wall edge in the second direction.

[0028] The plurality of edge features may include a plurality of recesses. The plurality of recesses may be arranged in a linear array. Each recess may be arranged in a linear array. Each recess may be substantially triangular, wherein one base of the recess is located at the edge of the top wall. One surface of each recess may have a tin-repellent material layer. At least a portion of a surface of the top wall other than the surfaces of the recesses may have a tin-loving material layer.

[0029] The conduit structure may further include a heating element that is in thermal contact with at least a portion of the top wall and is configured to maintain at least a portion of the top wall at a first temperature. The heating element may be configured to maintain a first portion of the top wall at the first temperature and a second portion of the top wall at a second temperature different from the first temperature.

[0030] Further embodiments, features and advantages of the subject matter disclosed in the present invention, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings.

Implementation Method

[0060] Various embodiments are now described with reference to the drawings, wherein similar reference numerals are always used to refer to similar elements. In the following description, specific details are set forth for purposes of explanation to facilitate a thorough understanding of all described embodiments. However, it will be apparent that in some or all cases any of the embodiments described below may be practiced without employing the specific design details attributed to them herein. In other cases, well-known structures and devices are shown in schematic or block diagram form to facilitate the description of one or more embodiments.

[0061] However, before describing these embodiments in more detail, it is instructive to describe example environments in which embodiments of the subject matter disclosed in this invention may be implemented. In the following description and in the claims, the terms "upward," "downward," "top," "bottom," "vertical," "horizontal," and similar terms may be used. Unless otherwise indicated or understood from the context, these terms are intended to indicate relative orientation only and not any orientation relative to gravity.

[0062] Referring initially to FIG1, a schematic diagram illustrating an exemplary EUV radiation source (e.g., a laser-generated plasma EUV radiation source 10) of one aspect of an embodiment of the subject matter disclosed in the present invention is shown. As shown, the EUV radiation source 10 may include a pulsed or continuous laser source 22, which may be, for example, a pulsed gas discharge CO2 laser source that generates a radiation beam 12 at a range of 10.6 µm or 1 µm. The pulsed gas discharge CO2 laser source may have DC or RF excitation operating at high power and high pulse repetition rate.

[0063] The EUV radiation source 10 also includes a target delivery system 24 for delivering a target material in the form of droplets or a continuous liquid stream. In this example, the target material is a liquid, but it may also be a solid or a gas. Tin is used as a non-limiting example of the target material described, and it is understood that other materials may be used. Furthermore, droplets are used as a non-limiting example of tin in form, and it should be understood that other forms may be used.

[0064] In the depicted system, the target delivery system 24 introduces a droplet 14 of target material into the interior of a vacuum chamber 26 having chamber walls 27. The vacuum chamber 26 includes an irradiation zone 28 for irradiating the target material to generate plasma. It should be noted that, as used herein, the irradiation zone is the area where target irradiation can or is intended to occur, and even when irradiation does not actually occur. The EUV light source may also include a beam steering system 32.

[0065] In the system shown, the components are configured such that the droplet 14 travels substantially horizontally. The direction from the laser source 22 toward the irradiation area 28 (i.e., the nominal propagation direction of the beam 12) can be considered the Z-axis. The path taken by the droplet 14 from the target delivery system 24 to the irradiation area 28 can be considered the X-axis. Therefore, the view in FIG1 is orthogonal to the XZ plane. The orientation of the EUV radiation source 10 is rotated relative to gravity as shown, where arrow G indicates a downward orientation relative to gravity. Although a system in which the droplet 14 travels substantially horizontally is depicted, those skilled in the art will understand that other configurations can be used in which the droplet travels vertically or at an angle relative to gravity between 90 degrees (horizontal) and 0 degrees (vertical) (inclusive).

[0066] The EUV radiation source 10 may also include an EUV light source controller system 60 and a laser emission control system 65. The EUV radiation source 10 may also include a detector (such as a target position detection system 70) that generates an output indicating the absolute or relative position of the target droplet, for example, relative to the irradiation area 28 and provides this output to the target position detection feedback system 62.

[0067] As shown in FIG. 1, the target delivery system 24 may include a target delivery control system 90. The target delivery control system 90 adjusts the path of the target droplet 14 through the irradiation zone 28. This adjustment may be achieved, for example, by repositioning the point at which the droplet generator 92 releases the target droplet 14. The droplet release point may be repositioned, for example, by tilting or translating the droplet generator 92. The droplet generator 92 extends into the chamber 26 and preferably supplies the target externally. A gas source (not shown) pressurizes the target into the droplet generator 92. The droplet 14, without conversion, continues through the irradiation zone 28 to the target container 34, also referred to herein as the tin trap 34.

[0068] Continuing with Figure 1, the radiation source 10 may also include one or more optical elements. In the following description, collector 30 is used as an example of such an optical element, but the description also applies to other optical elements. Collector 30 may be a normal-incident reflector, for example, implemented as a multi-layered mirror. Collector 30 may be in the form of an elongated ellipsoid having a central aperture to allow laser radiation 12 to pass through and reach the irradiation area 28. Collector 30 has a first focal point at the irradiation area 28 and a second focal point (also referred to as intermediate focal point 40) at a so-called midpoint 40, wherein EUV radiation can be output from EUV radiation source 10 and input to, for example, an integrated circuit lithography scanner 50. Scanner 50 uses the radiation, for example, to process silicon wafer workpiece 52 in a known manner using a magnifying glass or mask 54. Silicon wafer workpiece 52 is then further processed in a known manner to manufacture integrated circuit devices.

[0069] As mentioned, the management of residual target material is a key technical challenge. Residual tin tends to accumulate on the surface of chamber 26 during a process known as tin writing. This tin can fall off and contaminate collector 30. Tin can also block various inlets and conduits intended to allow buffer gas to flow inside chamber 26 or to serve as outlets for unused droplets. This residual tin must be managed to extend the lifespan of the source.

[0070] Figure 2 illustrates several modules for reducing tin contamination. In the illustrated orientation, the droplet generator is positioned directly behind chamber 26 such that the droplet path is out of plane to a conduit structure including tin trap inlet 110. In the illustrated embodiment, tin trap inlet 110 is positioned in a collector ring (“CFR”) 100 surrounding the circumference of collector 30. CFR 100 is provided to establish gas flow near collector 30. CFR 100 may include a cooling flow channel configured to deliver the provided fluid to remove at least a portion of the heat from CFR 100 during EUV radiation generation. Further details regarding the construction and operation of CFRs such as CFR 100 are available in International Publication No. WO 2021 / 130017 entitled “Collector Ring”, published July 1, 2021.

[0071] All patent applications, patents and printed publications cited herein are incorporated herein by reference in their entirety, except for any definitions or subjects abandoned or denied therein and any incorporated material inconsistent with the statements disclosed herein, in which case the language of this invention shall prevail.

[0072] CFR 100 introduces a flow of buffer gas that tends to carry tin away from the surface of collector 30. The gas is also introduced via a collector cone 120 disposed at the central aperture of collector 30. Laser radiation 12 also passes through this aperture. Further along the optical axis of chamber 26 between the main focal point and intermediate focal point 40 of collector 30, there is a section 130 with a series of flow vanes that guide the airflow in a pattern intended to keep tin away from the critical surface. This section 130 may also include vanes 36 for collecting tin. A high-flow scrubber 140 may also be used to control the tin. Exhaust port 125 is provided to exhaust the buffer gas from chamber 26 and must also maintain the removal of residual target material.

[0073] Figure 3A is a plan view of the configuration from the intermediate focal point 40 of the collector 30, as shown in Figure 2. As can be seen, the droplet generator 92 generates a stream of droplets 14. The CFR 100 surrounding the periphery or circumference of the collector 30 is also shown. The droplets 14 may be irradiated in the irradiation zone 28 at the main focal point of the collector 30, or they may pass through the main focal point to the tin trap inlet 110 without change and then through the conduit 112 to the tin trap 34. The tin trap 34 collects molten tin and transfers it to a tin bucket (not shown). A freeze valve (not shown) may be provided to allow discharge from the tin trap 34 without interrupting source operation.

[0074] Conventionally, the wall of the conduit 112 extending beyond the tin trap inlet 110 is a smooth, flat surface. This improperly allows stray residual tin to accumulate on the wall in the form of, for example, tin whiskers or threads. The accumulated tin can eventually partially or completely block the conduit 112, preventing the tin droplets 14 from passing through unimpeded.

[0075] To address this problem, according to an embodiment, at least one sidewall of the conduit 112 has an engineered surface with obstructions that trap residual tin by impeding the flow of tin across the engineered surface and freezing it in place. The engineered surface may be provided in the form of a thin plate-shaped insert positioned adjacent to the sidewall of the conduit 112, or may be integral with the sidewall of the conduit 112. In the following description, the plate-shaped insert will be used as an example of implementation. The plate-shaped insert may be constructed as a liner that can be easily replaced during maintenance after it has accumulated its tin capacity. Stray tin may be tin entrained in the airflow through the tin trap inlet 110 and the conduit 112, or may be tin flowing downward from the upper surface of the conduit 112 to the sidewall of the conduit 112, as described below.

[0076] Flow obstructions on the sidewalls ensure that the molten target material initially captured by the upper surface of the conduit 112 and flowing to the sidewalls freezes on the sidewalls and keeps the intended droplet path clean. This ensures that the opening in the conduit 112 is maintained, thereby allowing the intended flow.

[0077] According to one embodiment, as shown in FIG3B, stray tin entering the tin trap inlet 110 is captured and stored on a plate 200 maintained at a temperature below the melting point of tin. According to another embodiment, the plate 200 is heated to, for example, in the range of about 70°C to about 200°C, for example, about 100°C (about + / - 10% here and elsewhere). In instances where the surface material includes aluminum, temperatures greater than 70°C unexpectedly increase the surface tension of tin and aluminum, thus reducing the downward flow velocity across the plate 200.

[0078] The plate 200 is maintained at a temperature in the range of approximately 80°C to approximately 200°C so that tin is frozen on the surface of the plate 200. The plate 200 can be maintained at the desired temperature by active means (i.e., by providing a temperature control plate 215 (Figures 6A and 15)) or passive means (i.e. by heat transfer from a sufficiently close heating element).

[0079] Figure 4 provides a closer perspective view of the conduit 112 with plate 200 relative to the collector 30, CFR 100, tin trap 34, and droplet flow as indicated by arrow A. Figure 4 also shows a top cover element 210 configured to cover the conduit 112. Figure 5 shows the lateral extent of plate 200 relative to top cover element 210, and specifically in the same direction as and parallel to the droplet outlet flow path.

[0080] FIG. 6A is a plan view of plate 200 according to an embodiment. In the embodiment of FIG. 6A, plate 200 is shaped as a trapezoid. However, it should be understood that this shape is arbitrary and may be selected to at least partially cover the sidewall of conduit 112. The dotted line 300 indicates the lower edge of the tin landing area where molten solder will contact plate 200 when plate 200 is positioned in a suitable location adjacent to the sidewall of conduit 112. After molten solder impacts plate 200, the solder generally flows downward (in the diagram and by gravity) and encounters a series of tin-blocking structures or flow barriers 310 that resist the solder flow, eventually slowing the solder flow for a sufficient time to allow the solder to freeze and be captured on plate 200 as solidified solder.

[0081] In the illustrated embodiment, the barrier 310 takes the form of a vertical series of Z-shaped walls or ridges 320, 330, and 340 that create troughs or grooves between them. Although three such grooves are present in the example of FIG. 6A, it should be understood that fewer or more grooves may be used. The angles between the segments of the Z-shaped walls or ridges 320, 330, and 340 are selected to enhance the stopping of molten solder by allowing the flow of molten solder, for example, without excessively exceeding the ridges 320, 330, and 340.

[0082] According to another embodiment, the top ridge 320 (i.e., the ridge first encountered by the molten solder after impacting and flowing on the landing area 300) breaks apart with gaps 350 between at least some of its segments. These gaps 350 also serve to prevent the molten solder from exceeding the top ridge 320 and instead guide the molten solder flow through the grooves between the ridges 320, 330, and 340. This design allows the solder flow to acquire momentum because the gaps in the groove walls provide a low-resistance path to the next groove, while some of the momentum of the solder flow is dissipated due to the viscosity of the molten solder.

[0083] According to one embodiment, the geometry of the obstacle on the plate 200 is determined such that tin freezes on the plate 200 within a range of approximately 30 mm in the downward direction of gravity. Thus, the configured surface can hold a large amount of tin in a low profile, i.e., a profile that does not obstruct the path of droplets through the conduit 112. For some applications, it is preferable to configure the obstacle so that tin does not accumulate at a single point, causing the plate 200 to thermally short-circuit to near the hot surface. According to another embodiment, the surface is configured to prevent tin from flowing along a path that avoids, i.e., "wanders" or meanders around the surface features intended to capture tin.

[0084] Figure 6B is a side sectional view of plate 200 taken along line BB of Figure 6A. Plate 200 has a plate body 205, from which ridges 320, 330, and 340 protrude. Representative dimensions of the plate are a plate body thickness C of approximately 1 mm, a ridge thickness D of approximately 0.5 mm, and a ridge protrusion length E of approximately 3 mm. It should be understood that these dimensions are only representative and will be selected for use in any given implementation according to the technical requirements of that implementation. In some embodiments, the groove spacing may be 8 mm. In embodiments with one or more gaps between ridge wall sections, the width of the gap may be, for example, 3 mm.

[0085] These ridges can be configured as steps. These steps can be angled relative to the horizontal. This can be achieved by making the steps angled relative to the plate 200, or by having the steps protrude orthogonally to the angled plate, or by introducing an angle in a combination of these configurations. For example, except that the plate body 205 is angled θ relative to the vertical in FIG. 6C, FIG. 6C is a side sectional view of the same configuration as in 6B. For some embodiments, this enhances the ability of the ridges 320, 330 and 340 to impede the surface flow of the molten target across the plate body 200. The angle θ can be, for example, in the range of about 5° to about 45°, and more specifically in the range of about 10° to about 30°.

[0086] Figure 7 shows an example of a configuration in which plate 200 is angled relative to vertical and ridges 360 and 365 are angled relative to plate 200. This forms the hook-shaped configuration shown in Figure 7. Molten solder flowing on the ridges of plate 200 will solidify into a block 370 and tends to form complementary hook-shaped structures that are mechanically locked to plate 200, thus additionally securing the block 370.

[0087] The Z-shaped ridge of the embodiment just described is an example of a surface structure for capturing tin. Figure 8A shows a configuration of circular indentations 400 configured to capture tin flowing on the surface of board 200. The circular indentations 400 may have a radius larger or smaller than that shown in the example of Figure 8A. The circular indentations 400 shown in Figure 8A are configured in a periodic array, but a random configuration may also be used. This applies to all periodic configurations disclosed herein. Figure 8B shows a configuration of elongated elliptical indentations 420. Furthermore, the elongated elliptical indentations 420 may have a height and / or width larger or smaller than that shown in the example of Figure 8B.

[0088] Figure 9A shows an example of a configuration of linear indentations 430 arranged to capture tin flowing on the surface of board 200. The indentations 430 can have various widths and depths. The indentations 430 can extend fully across the length of board 200. Alternatively, the indentations 430 can be divided into segments 440 separated by gaps 445 as shown in Figure 9B. These gaps can be aligned as shown or misaligned, i.e., staggered relative to each other. Figure 10A shows a configuration of ridges 460 tilted backward at an angle θ' from vertical. These ridges can tilt backward as shown in Figure 10A or forward as shown by ridge 465 in Figure 10B. The angle θ' can be, for example, in the range of about 5° to about 45°, and more specifically in the range of about 10° to about 30°.

[0089] The damming structure may have any of several cross-sectional shapes. For example, as shown in Figure 11B, which is a cross-section taken along line CC of Figure 11A, each of the troughs 470 may have a square cross-sectional profile. As shown in Figure 11C, each of the troughs 480 may have an open (bottom-up) trapezoidal cross-section. As shown in Figure 11D, each of the troughs 490 may have a triangular cross-section separated by a smooth section or a flat portion. As shown in Figure 11E, each of the troughs 495 may have a triangular cross-section without an intervening flat portion. It will be apparent that many other configurations are possible and these configurations can be combined according to the design considerations of a given application.

[0090] Such engineered surface textures or configurations can be produced using techniques such as drilling, milling, or indentation. The overall effect of engineering such surface configurations is to intentionally introduce structures that slow down and impede the flow of molten tin across the surface.

[0091] Other configurations are possible. Figure 12 is a perspective view of a portion of a plate 200 having an array of cylindrical structures 510. The spacing or pitch of the cylindrical structures 510 may, for example, be in the range of approximately 5 mm to approximately 7 mm.

[0092] Figure 13A shows a configuration with a vertical series of slots 520, with groove sections 530 below each slot 520 rising from the surface in a "cheese grater" configuration, through which solder can flow through the slots 520 and down to the back of the plate 200. Figure 13B is a cross-sectional side view along line FF of the configuration in Figure 13A, with arrows indicating possible flow directions of solder encountering solder above the dashed line landing on the plate 200. Figure 13C shows a configuration similar to that of Figure 13A, except that the slots 540 in Figure 13C are not continuous, but instead horizontally separated, thus creating channels for solder flow between the slots 540. It should be noted that the body 200 in the configurations of Figures 13A and 13C can be oriented and tilted similarly to the plate body 205 in Figure 6C.

[0093] In addition to providing ridges and / or indentations on the surface of the plate 200 through which tin flows, the surface can also be roughened to enhance its ability to slow the flow of tin. Roughening can be performed by filling or etching and can be random or patterned. Figures 14A to 14F show various patterns that can be produced. Thus, Figure 14A shows a diagonal pattern on the surface of the plate 200. Figure 14B shows a crosshair pattern. Furthermore, any of these patterns can be periodic and uniformly spaced as shown, or, if formed, for example, by filling or scraping the surface of the plate 200, they can be more randomly distributed. Figure 14C shows a pattern extending parallel to the length of the plate 200. Figure 14D shows a pattern extending transversely to the surface of the plate 200. Figure 14E shows a dense pattern of tracks extending parallel to the length of the surface of the plate 200. Figure 14F shows a dense diamond pattern on the plate 200.

[0094] Plate 200 may be made of or coated with a material that rapidly forms an indirect metal bond with tin to facilitate the dispersion of tin on its surface. Such materials include aluminum, molybdenum, nickel, silver, and Worthfield nickel-chromium superalloys, such as Inconel® alloys.

[0095] Plate 200, as described above, is primarily configured as an insert in a conduit. Plate 200 and conduit 112 can be configured to allow easy removal of the insert and replacement with a clean insert during operation of the source. However, as mentioned, the obstruction may alternatively be integrated with the sidewall of conduit 112.

[0096] Plate 200 is also primarily described above as being used in a target container conduit. However, it will be apparent to those skilled in the art that the benefits of the insert can also be obtained by placing the plate (such as plate 200) in other ports, conduits, apertures, and the like, where uncontrolled accumulation of solder on the inner surface can lead to blockage or other undesirable forms of solder accumulation. It will also be apparent to those skilled in the art that the benefits of the insert can also be obtained by placing the insert on other surfaces, where uncontrolled accumulation of solder on the inner surface can lead to solder ejection or solder detachment from the surface and impact on the collector.

[0097] Figure 15 shows another embodiment. As can be seen, the conduit 112 can be tilted relative to gravity (arrow G). Depending on the embodiment, this angle can be in the range of approximately 20° to approximately 40°, for example, 28°. Figure 15 also shows a temperature control plate 215 configured to maintain the plate 200 at a temperature below the melting point of the target material. This allows the target material to flow in the direction of arrow T, but the target material will solidify and be trapped on the plate 200.

[0098] The conduit cap element 225 is maintained above the target melting temperature (232°C for tin) to prevent tin from solidifying on the exposed top surface and to maintain the liquid tin layer. Tin debris impacting the bottom surface of the cap element 210 will be added to the liquid tin layer. After the liquid tin layer has accumulated a critical weight of tin flow, the tin begins to flow toward the edge of the cap plate 210 in the direction of arrow R. After sufficient tin has accumulated on the edge at one location, the liquid tin drips onto the landing area on the plate 200 to capture the tin.

[0099] Therefore, as shown in FIG15, the top element 225 of the conduit is positioned below the top cover element 210. According to the embodiment, the top element 225 may have a bottom surface arranged at an angle relative to the top cover element 210, which increases the angle relative to the existing gravity when the conduit 112 has an inclined orientation. The final angle θ'' may be in the range of about 20° to about 40° relative to the horizontal, for example, 32.5°. This angle allows the molten target material collected on the exposed surface of the top element 225 to flow out of the top element 225 and onto the plate 200. The top element 225 may be actively heated by its own heater, or, as shown, the top element may be passively heated by thermal contact with another heated surface (i.e., the surface heated by the temperature control plate 215). For the purposes of the following discussion, the sidewall with plate 200 is referred to as left sidewall 217, and the opposite sidewall as right sidewall 219, "right" and "left" viewed from the inlet on the collector side of conduit 112. Thus, tin flows via conduit from the container to the tin trap in the plane of the figure. These references are provided only for the purpose of facilitating clarity in the following description. Those skilled in the art will understand that the designations are arbitrary. For example, in some embodiments, plate 200 may be disposed on the right sidewall.

[0100] As mentioned above, the top element 225 can be actively heated by a designated heater, or the top element 225 can be passively heated by thermal contact with another heated surface (e.g., a surface heated by a temperature control plate 215). Figure 16 shows an example of a solder control insert defining a conduit 112 with a heated top plate 230. The left side wall 217 is not visible in Figure 16, but is positioned below the plate 200 from the viewpoint of Figure 16. The right side wall 219 is at the top from the viewpoint of Figure 16. The top element 225 is not visible in Figure 16, but is positioned behind the heated top plate 230 from the viewpoint of Figure 16. According to the embodiment, the top plate 230 has a dripping feature 250 intended to control the movement of solder along the edge 231 of the top plate, which is positioned parallel to and adjacent to the edge 202 of the plate 200 to a selected section to control the dripping onto the side plate 200. The droplet feature 250 also guides the flow of tin, causing the tin to accumulate and fall more rapidly. The view in Figure 16 is generally upward, making the bottom surface of the heated top plate 230 visible. In the example of Figure 16, the heated top plate 230 is actively heated by a heating wire 236, shown in dashed lines, which is positioned inside the heated top plate 230 to make thermal contact with the bottom surface of the heated top plate 230. The tin accumulated on the bottom surface of the heated top plate 230 flows laterally (generally downward in the direction of the arrows in the figure) onto the side plate 200 as described above.

[0101] The edge 231 of the bottom surface of the heated top plate 230, which extends generally parallel to the longitudinal edge 202 of the side plate 200, has a droplet feature 250 that controls the flow of tin along the edge 231 and away from the edge 231 onto the plate 200. According to one embodiment, the droplet feature 250 is configured to impede the flow of tin parallel to the edge of the side plate 200 and thus may exit toward a collector. According to another embodiment, the droplet feature 250 defines a point where tin can coalesce and subsequently fall onto the side plate 200.

[0102] As shown in Figure 16, the droplet feature 250 is configured as a linear array of triangular elements. The triangular elements can be formed as recesses or notches, for example, by milling. The base of each triangular element is arranged to coincide with the edge 231 of the bottom surface 233 of the top plate 230. Although these triangular elements are used as examples in the following description, those skilled in the art will understand that other shapes can be used. The triangular elements can have any suitable dimensions, such as a base length of about 6 mm and a depth of about 3 mm.

[0103] Figure 17A is a plan view of the bottom surface 233 of the heated top plate 230. Furthermore, in the example of Figure 17A, the edge 231 of the bottom surface 233 of the heated top plate 230, which extends generally parallel to the longitudinal edge of the side plate 200, has a droplet feature 250 for controlling the flow of solder. The flow of solder is generally in the direction of arrow T. As shown in Figure 16, the droplet feature 250 is configured as a linear array of triangular elements. According to another configuration, the heated top plate 230 of Figure 17A has a first section 232 positioned closer to the opening of the insert (the collector side of the conduit) and a second section 234 positioned towards the rear of the insert (the solder trap side of the conduit). This first section 232, which has a line of sight to the collector, is typically extended by, for example, about 50 mm.

[0104] As is more apparent from Figure 17B, which is a side view of the heated top plate 230 taken from the left-hand side of the conduit 112. The first section 232 is angled, wherein the front portion of the first section 232 is higher than the rear portion of the first section 232 when in the proper position, such that molten solder impacting and accumulating on the solder flow surface 235 on the first section 232 will tend to flow away from the inlet of the conduit and thus away from fragile elements such as collector optics.

[0105] Figure 18A is an enlarged view of region 18A in Figure 17A. Depending on the configuration, droplet features 250 converge at connecting region 256. Connecting region 256 can be a vertex or an arc with a radius of curvature of approximately 0.5 mm and an angle θ of approximately 90°. Tin flow is generally in the direction of arrow T. The surface of droplet feature 250 may have a material layer 252 that tends to repel tin, i.e., is tin-repellent, such as titanium nitride (TiN). Tin-loving surfaces promote tin adhesion to the surface and tin flow across angled protruding edges. The surface of top plate 230, excluding droplet feature 250, may have a material layer 254 that tends not to repel tin, i.e., is tin-loving, such as tin itself. This promotes the effect of tin coalescing in the vertex 258 of the triangular feature of droplet feature 250, thus making vertex 258 an effective tin coalescence site where tin collects before falling onto side plate 200. The boundary of tin-loving surfaces and the transition from tin-loving surface coatings to tin-repellent surface coatings promote tin aggregation.

[0106] Figure 18B is an enlarged view of region 18B in Figure 17B. Depending on the pattern, the droplet feature 250 may have a depth of approximately 0.5 mm. The tin-repellent material layer 252 and the tin-loving material layer 254 are also visible in Figure 18B.

[0107] Figure 19 is a perspective view taken from the edge 202 (not shown) of the top plate, looking upwards at the edge 231, illustrating a portion of the configuration of the droplet feature 250. The flow of tin is generally in the direction of arrow T. Similar to what is shown in Figure 16, the droplet feature 250 is configured as a linear array of recessed triangular elements, for example, manufactured by milling. The droplet feature 250 tends to aggregate tin at its vertices 258, thus effectively making the vertices 258 tin aggregation sites where tin (e.g., tin lumps 260) collects before falling onto the side plate 200. The tin-repellent material layer 252, the tin-loving material layer 254, and the connecting region 256 are also visible in Figure 18B.

[0108] According to another embodiment, the temperature of the heated top plate 230 has a gradient, that is, the first section 232 (FIG. 17A) with the line of sight to the collector has a lower temperature than the second section 234. This is because the tin ejection rate varies with temperature, and therefore the temperature of the first section 232 is kept lower to reduce the ejection of tin that may have an unobstructed path to the collector. The first section 232 can therefore have a temperature in the range of about 235°C to about 260°C, and the second section 234 can have a temperature in the range of about 250°C to about 330°C, which is higher than the temperature of the first section, but other temperatures and relative temperatures can be used in other configurations. In addition, as mentioned, the first section 232 has a slight gravitational upward angle. This ensures that the molten tin accumulation tends to flow away from the line of sight to the collector, again minimizing the ejection on the collector. According to the embodiment, the first segment 232 does not have the dripping feature 250 to avoid the accumulation of tin in the first segment 232, rather than the better accumulation in the second segment 234 which is further inside the chamber 26.

[0109] Furthermore, according to the configuration and as shown in Figure 20, the top plate 230 and the side plate 200 are spaced apart to establish a gap G of, for example, at least 5 mm. The flow of solder is generally in the direction of arrow T. The gap G prevents molten solder from bridging between the top plate 230 and the side wall 200, and thus avoids thermal shorting.

[0110] The above description includes examples of one or more embodiments. It is certainly impossible to describe every conceivable combination of components or methods for the purpose of describing such embodiments, but those skilled in the art will recognize that many other combinations and arrangements of various embodiments are possible. Therefore, the described embodiments are intended to encompass all such changes, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, the term "comprising" as used in the implementation or claims is intended to be inclusive in a manner similar to the interpretation of the term "including" when "comprising" is used as a transitional term in a claim. Moreover, although elements of the described patterns and / or embodiments may be described or claimed in the singular, the plural is also covered unless explicitly stated otherwise. Additionally, unless otherwise stated, all or part of any pattern and / or embodiment may be used together with all or part of any other pattern and / or embodiment.

[0111] The implementation may be further described using the following clauses. 1. A conduit structure adapted for placement in fluid communication with the interior of a chamber for an extreme ultraviolet (EUV) radiation source, wherein a target material is transformed in the chamber, the conduit structure comprising at least one sidewall facing the interior of the conduit structure, at least a portion of the sidewall having a plurality of flow barriers configured to impede flow of molten target material across that portion of the sidewall. 2. The conduit structure of clause 1, further comprising a plate configured to cover the at least portion of the sidewall, the plurality of flow barriers disposed on the plate. 3. The conduit structure of clause 1, wherein the plurality of flow barriers comprises a plurality of unidirectional ridges extending at least partially through the conduit structure in a first direction. 4. The conduit structure of clause 3, wherein one of the ridges is discontinuous. 5. The conduit structure of claim 3, wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction. 6. The conduit structure of claim 5, wherein one of the ridges is discontinuous. 7. The conduit structure of claim 1, wherein the at least one sidewall has a first sidewall edge extending in a first longitudinal direction and further includes a top wall facing the interior of one of the conduit structures, the top wall being configured to have a top wall edge extending substantially parallel to the first sidewall edge in the first longitudinal direction, the top wall edge having a plurality of edge features configured to inhibit the flow of one of the target materials along the top wall edge in the first direction. 8. An extreme ultraviolet (EUV) radiation source comprising a chamber of an EUV target, the chamber having at least one conduit structure having a surface exposed to the EUV target, wherein a first portion of the surface is disposed at a location where a molten target encounters the first portion of the surface and is oriented such that gravity would tend to pull the molten target downward across the first portion of the surface in a first direction, and a second portion below the first portion of the surface has a plurality of flow barriers configured to impede the flow of the molten target across the second portion in the first direction. 9. The EUV radiation source of claim 8, wherein the surface includes a plate insert including the plurality of flow barriers. 10. The EUV radiation source of claim 9, wherein the plate insert is maintained at a temperature below the melting temperature of the target. 11. The EUV radiation source of claim 9, wherein the target is tin and the plate insert is maintained at a temperature not exceeding approximately 200°C. 12. An EUV radiation source as described in paragraph 8, wherein the plurality of flow obstacles comprises a plurality of unidirectional ridges extending in one of a second directions substantially perpendicular to the first direction. 13. An EUV radiation source as described in paragraph 12, wherein the uppermost of the ridges is discontinuous.14. An EUV radiation source of claim 8, wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the second direction alternates with a second group of straight segments angled at a second angle relative to the second direction. 15. An EUV radiation source of claim 14, wherein one of the uppermost ridges is discontinuous, thereby defining a plurality of gaps passing through the uppermost ridge. 16. An EUV radiation source of claim 8, further comprising a cooling flow ring disposed at least partially around a circumference of a collector mirror positioned in the chamber, the conduit structure positioned in the cooling flow ring to provide a path between the interior of the chamber and a target container. 17. An EUV radiation source of claim 8, wherein the plurality of flow obstructions comprise a plurality of substantially circular indentations. 18. An EUV radiation source of claim 8, wherein the plurality of flow obstructions comprise a plurality of substantially rectangular indentations. 19. An EUV radiation source as described in clause 18, wherein the plurality of substantially rectangular indentations extend along the same length as one of the second portions of the surface. 20. An EUV radiation source as described in clause 19, wherein the plurality of substantially rectangular indentations are arranged in columns and rows in an array. 21. An EUV radiation source as described in clause 8, wherein the plurality of flow obstacles comprises a plurality of angled blades located on the second portion. 22. An EUV radiation source as described in clause 8, wherein the plurality of flow obstacles comprises a plurality of elongated slits extending perpendicular to the first direction, wherein each slit has an associated groove portion. 23. An EUV radiation source as described in clause 8, wherein at least a portion of the surface is roughened. 24. The EUV radiation source of clause 8 further includes a top surface element adjacent to and angled relative to the surface, and adapted and configured to allow molten target material collected on the top surface element to flow out of the top surface element and onto the surface. 25. An extreme ultraviolet (EUV) radiation source includes a chamber and a target container in fluid communication with an interior of the chamber via a conduit, the conduit including a target collection plate positioned to at least partially cover an interior surface of the conduit, the target collection plate including the plurality of structures configured to impede the flow of molten target material across a plurality of structures and thus allow the molten target material to solidify on the target collection plate. 26. An EUV radiation source as described in clause 25, wherein the target collection plate has a first target collection plate edge extending in a first longitudinal direction and further includes a top wall facing the interior of one of the conduit structures, the top wall being configured to have a top wall edge extending substantially parallel to the first target collection plate edge in the first longitudinal direction, the top wall edge having a plurality of edge features configured to inhibit the flow of target material along one of the top wall edges in the first direction.27. An extreme ultraviolet (EUV) radiation source comprising a chamber including a surface exposed at a location of residual target material during EUV radiation generation, the source including a target material collection plate at least partially covering the surface, a temperature controller configured to maintain the target material collection plate at a temperature below the melting temperature of the target material, the target material collection plate including a plurality of flow barriers, the target material collection plate being oriented such that gravity pulls the molten target material across the flow barriers and the flow barriers being oriented to impede the flow of the molten target material. 28. A conduit structure adapted for placement in fluid communication with the interior of a chamber for an extreme ultraviolet (EUV) radiation source, wherein a target material is transformed within the chamber, the conduit structure comprising: at least one sidewall facing the interior of the conduit structure, the at least one sidewall having a first sidewall edge extending in a first longitudinal direction and at least a portion of the sidewall having a plurality of flow barriers substantially extending in the first longitudinal direction and configured to impede flow of molten target material across that portion of the sidewall in a second direction different from the first direction; and a top wall facing the interior of the conduit structure, the top wall being configured to have a top wall edge extending substantially parallel to the first sidewall edge in the first longitudinal direction, the top wall edge having a plurality of edge features configured to inhibit flow of target material along the top wall edge in the first longitudinal direction. 29. The conduit structure of claim 28, wherein the top wall is in thermal contact with a heat source such that the top wall reaches a temperature greater than the melting temperature of the target material. 30. The conduit structure of claim 28, wherein the plurality of edge features comprises a plurality of recesses. 31. The conduit structure of claim 30, wherein the plurality of recesses are arranged in a linear array. 32. The conduit structure of claim 31, wherein each recess is substantially triangular, and one base of the recess is located at the edge of the top wall. 33. The conduit structure of claim 30, wherein one surface of each recess has a tin-repellent material layer. 34. The conduit structure of claim 33, wherein at least a portion of one surface of the top wall other than the surfaces of the recesses has a tin-loving material layer. 35. The conduit structure of claim 33, wherein one surface of the top wall other than the surfaces of the recesses is covered with a tin-loving material layer. 36. The conduit structure of claim 28, further comprising a heating element that is in thermal contact with at least a portion of the top wall and configured to maintain at least a portion of the top wall at a first temperature. 37. The conduit structure of clause 36, wherein the heating element is configured to maintain a first portion of the top wall at the first temperature and a second portion of the top wall at a second temperature different from the first temperature.38. An extreme ultraviolet (EUV) radiation source comprising a chamber of an EUV target, the chamber having at least one conduit structure including a transverse side surface exposed to the EUV target, wherein a first portion of the transverse side surface is disposed at a location where molten target flowing from a top surface of the conduit drips down onto the first portion of the transverse side surface and is configured such that gravity would tend to pull the molten target downward across the first portion of the transverse side surface in a first direction, and a second portion of the transverse side surface below the first portion having a plurality of flow barriers configured to impede the flow of the molten target across the second portion in one of the first directions, the transverse side surface having a first transverse side surface edge extending in a second direction; and a top surface configured to have a top surface edge extending substantially parallel to the first transverse side surface edge in the second direction, the top wall surface having a plurality of edge features configured to inhibit the flow of target along the top surface edge in one of the second directions. 39. An EUV radiation source of claim 38, wherein the plurality of edge features comprises a plurality of recesses. 40. An EUV radiation source of claim 39, wherein the plurality of recesses are arranged in a linear array. 41. An EUV radiation source of claim 39, wherein each recess is substantially triangular, and one base of the recess is located at the edge of the top wall. 42. An EUV radiation source of claim 39, wherein one surface of each recess has a tin-repellent material layer. 43. An EUV radiation source of claim 42, wherein at least a portion of a surface of the top wall other than the surfaces of the recesses has a tin-loving material layer. 44. A conduit structure of claim 38, further comprising a heating element that is in thermal contact with at least a portion of the top wall and configured to maintain at least a portion of the top wall at a first temperature. 45. An EUV radiation source as described in paragraph 44, wherein the heating element is configured to maintain a first portion of the top wall at the first temperature and a second portion of the top wall at a second temperature different from the first temperature.

[0112] The above-described embodiments and other embodiments fall within the scope of the following patent application. [Simplified Explanation of the Diagram]

[0031] Figure 1 is a schematic, non-scale view of the general concept of a laser-generated plasma EUV radiation source system.

[0032] Figure 2 is a non-scale drawing showing a possible configuration of the chamber and airflow system in a laser-generated plasma EUV radiation source system.

[0033] Figure 3A is a schematic, non-scale plan view of one possible configuration of a laser-generated plasma EUV radiation source system.

[0034] Figure 3B is a schematic, non-scale plan view of a portion of a possible configuration of a laser-generated plasma EUV radiation source system according to an embodiment of the subject matter disclosed in the present invention.

[0035] Figure 4 is a non-scale perspective view showing a possible configuration of a target control system for an inlet of a target container, according to an embodiment of the subject matter disclosed in the present invention.

[0036] Figure 5 is a non-scale perspective view showing a possible structure of a target control system for an inlet of a target container, illustrating an embodiment of the subject matter disclosed in the present invention.

[0037] Figure 6A is a non-scale plan view showing a possible configuration of flow obstacles on an insert plate of a target control system for an inlet of a target container, according to an embodiment of the subject matter disclosed in the present invention.

[0038] FIG6B is a non-scale sectional side view taken along line BB of FIG6A, showing a possible configuration of the insert plate for the inlet of the target container of the target control system according to an embodiment of the subject matter disclosed in FIG6A.

[0039] FIG6C is a non-scale cross-sectional side view showing another possible configuration of the insert plate of the target control system for the inlet of the target container, according to an embodiment of the subject matter disclosed in the present invention.

[0040] Figure 7 is a cross-sectional side view of a target capture and holding system for an inlet of a target container, illustrating an embodiment of the subject matter disclosed in the present invention.

[0041] Figures 8A and 8B are non-scale plan views illustrating other possible configurations of flow obstacles on the insert plate of the target control system for the inlet of the target container, as shown in the embodiments of the subject matter disclosed in the present invention.

[0042] Figures 9A and 9B are non-scale plan views illustrating other possible configurations of flow obstacles on the insert plate of the target control system for the inlet of the target container, as shown in the embodiments of the subject matter disclosed in the present invention.

[0043] Figures 10A and 10B are non-scale plan views illustrating other possible configurations of flow obstacles on the insert plate of the target control system for the inlet of the target container, as shown in the embodiments of the subject matter disclosed in the present invention.

[0044] FIG11A is a non-scale drawing of an insert plate for a target control system according to an embodiment of the subject matter disclosed in the present invention.

[0045] Figures 11B to 11E are cross-sections of an embodiment of the tin blocking structure on the insert plate of Figure 11, taken along line CC of Figure 11 according to an embodiment of the subject matter disclosed in the present invention.

[0046] Figure 12 is a non-scale perspective view showing another possible configuration of flow obstructions on the insert plate of a target control system for the inlet of a target container, according to an embodiment of the subject matter disclosed in the present invention.

[0047] FIG13A is a non-scale perspective view showing a possible configuration of flow obstacles on an insert plate of a target control system for an inlet of a target container, according to an embodiment of the subject matter disclosed in the present invention.

[0048] FIG13B is a non-scale sectional side view taken along line FF of FIG13A, showing a possible configuration of an insert plate for a target control system for an inlet of a target container according to an embodiment of the subject matter disclosed in the present invention.

[0049] Figure 13C is a non-scale perspective view showing another possible configuration of flow obstructions on the insert plate of a target control system for the inlet of a target container, according to an embodiment of the subject matter disclosed in the present invention.

[0050] Figures 14A to 14F are plan views of surface roughening on an insert plate of a target control system for use in an inlet of a target container, as described in the embodiments of the subject matter disclosed in the present invention.

[0051] Figure 15 is a plan view of a target control system for the inlet of a target container, as described in an embodiment of the subject matter disclosed in this invention.

[0052] Figure 16 is a bottom perspective view of a target control system for an inlet of a target container, as described in an embodiment of the subject matter disclosed in the present invention.

[0053] Figure 17A is a plan view of the bottom of the top plate of a target control system for the inlet of a target container, as shown in an embodiment of the subject matter disclosed in the present invention.

[0054] Figure 17B is an edge view of the top plate of a target control system for the inlet of a target container, as shown in an embodiment of the subject matter disclosed in the present invention.

[0055] Figure 18A is an enlarged version of a portion of Figure 17A.

[0056] Figure 18B is an enlarged version of a portion of Figure 17B.

[0057] Figure 19 is a perspective view of a portion of the edge of the top plate of a target control system for an inlet of a target container, as described in an embodiment of the subject matter disclosed in the present invention.

[0058] Figure 20 is a front view of a target control system for the inlet of a target container, as described in an embodiment of the subject matter disclosed in this invention.

[0059] Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. Embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to those skilled in the art based on the teachings contained herein.

Claims

1. A conduit structure adapted for placement in fluid communication with the interior of a chamber for an extreme ultraviolet (EUV) radiation source, wherein a target material is transformed within the chamber, the conduit structure including at least one sidewall facing the interior of the conduit structure, at least a portion of the sidewall having a plurality of flow barriers configured to impede flow of the molten target material across that portion of the sidewall, wherein the plurality of flow barriers includes a plurality of codirectional ridges extending at least partially via the conduit structure in a first direction, and wherein the ridges extend in a zigzag pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction.

2. The conduit structure of claim 1, further comprising a plate configured to cover at least a portion of the sidewall, the plurality of flow barriers being disposed on the plate.

3. The ductal structure of claim 1, wherein one of the ridges is discontinuous.

4. The conduit structure of claim 1, wherein the at least one sidewall has a first sidewall edge extending in the first direction and further includes a top wall facing the interior of one of the conduit structures, the top wall being configured to have a top wall edge extending substantially parallel to the first sidewall edge in the first direction, the top wall edge having a plurality of edge features configured to inhibit the flow of a target material along the top wall edge in one of the first directions.

5. An extreme ultraviolet (EUV) radiation source comprising a chamber of an EUV target, the chamber having at least one conduit structure having a surface exposed to the EUV target, wherein a first portion of the surface is disposed at a location where a molten target encounters the first portion of the surface and is configured such that gravity would tend to pull the molten target downward across the first portion of the surface in a first direction, and a second portion below the first portion of the surface has a plurality of flow barriers configured to impede the flow of the molten target across the second portion in the first direction, wherein the plurality of flow barriers comprises a plurality of co-directional ridges extending in a second direction substantially perpendicular to the first direction, and wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the second direction alternates with a second group of straight segments angled at a second angle relative to the second direction.

6. The EUV radiation source of claim 5, wherein the surface includes a plate insert that includes the plurality of flow barriers.

7. The EUV radiation source of claim 6, wherein the plate insert is maintained at a temperature below the melting temperature of the target material.

8. The EUV radiation source of claim 6, wherein the target material is tin, and the plate insert is maintained at a temperature not exceeding about 200°C.

9. The EUV radiation source as claimed in claim 5, wherein the uppermost of the ridges is discontinuous.

10. The EUV radiation source of claim 5 further includes a cooling flow ring disposed at least partially around a circumference of a collector mirror located in the chamber, the conduit structure being positioned in the cooling flow ring to provide a path between the interior of the chamber and a target container.

11. The EUV radiation source as claimed in claim 5, wherein the plurality of flow obstacles comprises a plurality of substantially circular indentations.

12. The EUV radiation source as claimed in claim 5, wherein the plurality of flow obstacles comprises a plurality of substantially rectangular indentations.

13. The EUV radiation source of claim 12, wherein the plurality of substantially rectangular indentations extend together with the length of one of the second portions of the surface.

14. The EUV radiation source as claimed in claim 13, wherein the plurality of substantially rectangular indentations are arranged in columns and rows in an array.

15. The EUV radiation source of claim 5, wherein the plurality of flow obstacles comprises a plurality of angled blades located on the second portion.

16. The EUV radiation source of claim 5, wherein the plurality of flow obstacles comprises a plurality of elongated slits extending perpendicular to the first direction, wherein each slit has an associated groove portion.

17. An EUV radiation source as claimed in claim 5, wherein at least a portion of the surface is roughened.

18. The EUV radiation source of claim 5 further includes a top surface element adjacent to and angled relative to the surface and adapted and configured to allow molten target material collected on the top surface element to flow out of the top surface element and onto the surface.

19. An extreme ultraviolet (EUV) radiation source comprising a chamber and a target container in fluid communication with an interior of one of the chambers via a conduit, the conduit including a target collection plate positioned to at least partially cover an interior surface of one of the conduits, the target collection plate including a plurality of structures configured to impede the flow of molten target material across one of a plurality of structures and thus allow the molten target material to solidify on the target collection plate, wherein the plurality of structures includes a plurality of co-directional ridges extending at least partially via the conduit in a first direction, and wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction.

20. The EUV radiation source of claim 19, wherein the target collection plate has a first target collection plate edge extending in the first direction and further includes a top wall facing the interior of one of the conduit structures, the top wall being configured to have a top wall edge extending substantially parallel to the first target collection plate edge in the first direction, the top wall edge having a plurality of edge features configured to inhibit the flow of target material along the top wall edge in one of the first directions.

21. An extreme ultraviolet (EUV) radiation source comprising a chamber including a surface exposed at a location of residual target material during EUV radiation generation, the source including a target material collection plate at least partially covering the surface, a temperature controller configured to maintain the target material collection plate at a temperature below the melting temperature of the target material, the target material collection plate including a plurality of flow barriers, the target material collection plate being oriented such that gravity pulls the molten target material across the plurality of flow barriers and the plurality of flow barriers being oriented to impede the flow of the molten target material, wherein the plurality of flow barriers includes a plurality of co-directional ridges extending at least partially via a conduit structure in a first direction, and wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction.

22. A conduit structure adapted for placement in fluid communication with the interior of a chamber for an extreme ultraviolet (EUV) radiation source, wherein a target material is transformed within the chamber, the conduit structure comprising: At least one sidewall facing the interior of one of the conduit structures, the at least one sidewall having a first sidewall edge extending in a first direction and at least a portion of the sidewall having a plurality of flow barriers extending substantially in the first direction and configured to impede the flow of molten target material across that portion of the sidewall in a second direction different from the first direction, wherein the plurality of flow barriers includes a plurality of co-directional ridges extending at least partially through the conduit structure in the first direction, and wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the first direction alternates with a second group of straight segments angled at a second angle relative to the first direction; and a top wall facing the interior of one of the conduit structures, the top wall being configured to have a top wall edge extending substantially parallel to the first sidewall edge in the first direction, the top wall edge having a plurality of edge features configured to inhibit the flow of target material along the top wall edge in the first direction.

23. The conduit structure of claim 22, wherein the top wall is in thermal contact with a heat source such that the top wall reaches a temperature greater than the melting temperature of the target material.

24. The conduit structure of claim 22, wherein the plurality of edge features comprises a plurality of recesses.

25. The conduit structure of claim 24, wherein the plurality of recesses are arranged in a linear array.

26. The conduit structure of claim 25, wherein each recess is substantially triangular, wherein the base of one of the recesses is located at the edge of the top wall.

27. The conduit structure of claim 24, wherein one surface of each recess has a tin-repellent material layer.

28. The conduit structure of claim 27, wherein at least a portion of one surface of the top wall, excluding the recessed surfaces, has a tin-loving material layer.

29. The conduit structure of claim 27, wherein one surface of the top wall, excluding the recessed surfaces, is covered with a layer of tin-loving material.

30. The conduit structure of claim 22, further comprising a heating element that is in thermal contact with at least a portion of the top wall and configured to maintain at least a portion of the top wall at a first temperature.

31. The conduit structure of claim 30, wherein the heating element is configured to maintain a first portion of the top wall at the first temperature and a second portion of the top wall at a second temperature different from the first temperature.

32. An extreme ultraviolet (EUV) radiation source comprising a chamber for transforming an EUV target, the chamber having at least one conduit structure including a transverse side surface exposed to the EUV target, wherein a first portion of the transverse side surface is disposed at a location where molten target flowing from a top surface of the conduit drips down onto the first portion of the transverse side surface and is configured such that gravity will tend to pull the molten target downward across the first portion of the transverse side surface in a first direction, and a second portion of the transverse side surface below the first portion having a plurality of flow barriers is configured to impede the flow of the molten target across the second portion in the first direction. The lateral side surface has a first lateral side surface edge extending in a second direction, wherein the plurality of flow obstructions includes a plurality of unidirectional ridges extending in the second direction at least partially via the conduit structure, and wherein the ridges extend in a Z-shaped pattern, wherein a first group of straight segments angled at a first angle relative to the second direction alternates with a second group of straight segments angled at a second angle relative to the second direction; and the top surface is configured to have a top surface edge extending substantially parallel to the first lateral side surface edge in the second direction, the top surface having a plurality of edge features configured to inhibit the flow of the target material along the top surface edge in one of the second directions.

33. An EUV radiation source as claimed in claim 32, wherein the plurality of edge features comprises a plurality of depressions.

34. The EUV radiation source as claimed in claim 33, wherein the plurality of depressions are arranged in a linear array.

35. An EUV radiation source as claimed in claim 33, wherein each recess is substantially triangular, wherein the base of one of the recesses is located at the edge of the top surface.

36. The EUV radiation source of claim 33, wherein one surface of each recess has a tin-repellent material layer.

37. The EUV radiation source of claim 36, wherein at least a portion of a surface of the top surface other than the recessed surfaces has a tin-loving material layer.

38. The EUV radiation source of claim 32, further comprising a heating element that is in thermal contact with at least a portion of the top surface and configured to maintain at least a portion of the top surface at a first temperature.

39. The EUV radiation source of claim 38, wherein the heating element is configured to maintain a first portion of the top surface at the first temperature and a second portion of the top surface at a second temperature different from the first temperature.

Images