Guiding device and associated system

Abstract

To provide a radiation source including a gas flow guiding device.SOLUTION: There is provided a radiation source comprising: a chamber comprising a plasma formation region; a radiation collector arranged in the chamber, the radiation collector configured to collect radiation emitted at the plasma formation region and to direct the collected radiation to an intermediate focus region; a debris mitigation system configured to direct a first gas flow from the intermediate focus region towards the plasma formation region; and a guiding device arranged in the chamber such that the first gas flow is directed around the guiding device. There are provided a system and apparatus for reducing contamination of the inner wall of an EUV vessel. The system and apparatus comprise inner vessel wall supplies of gas that introduces gas in a direction away from the vessel wall through multiple nozzles. The system and apparatus also optionally include an asymmetric exhaust that exhausts gas from the EUV vessel while providing a flow geometry that promotes a direction of the gas away from the inner vessel wall and the EUV collector within the EUV vessel.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims priority to U.S. Application No. 15 / 400,929, filed on January 6, 2017, European Application No. 17158280.2, filed on February 28, 2017, and U.S. Application No. 62 / 596,629, filed on December 8, 2017, the entire contents of each of which are incorporated herein by reference.

[0002]

[0002] The present disclosure relates to a gas flow guiding device and a radiation source including such a guiding device. The present disclosure relates to, for example, a guiding device and a radiation source used in a lithography system. The present disclosure also relates to a radiation source including an EUV container having an inner wall of the container protected from debris by a gas supply portion on the inner wall of the container, and more specifically, to a method and an apparatus for supplying a gas flow into the EUV container to protect an inner surface of the container, such as a portion above the EUV collector of the EUV container on the inner wall of the container, in the direction of gravity.

Background Art

[0003]

[0003] A lithography apparatus is a machine constructed to impart a desired pattern onto a substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithography apparatus can project a pattern from a patterning device (e.g., a mask) onto a layer of radiation - sensitive material (resist) provided on a substrate.

[0004]

[0004] The wavelength of the radiation used by a lithography apparatus to project a pattern onto a substrate determines the minimum size of the features that can be formed on that substrate. A lithography apparatus using EUV radiation, which is electromagnetic radiation having a wavelength in the range of 4 - 20 nm, can be used to form smaller features on a substrate than conventional lithography apparatuses (e.g., apparatuses that can use electromagnetic radiation having a wavelength of 193 nm).

[0005]

[0005] The lithography system may include one or more radiation sources, a beam delivery system, and one or more lithography apparatuses. The beam delivery system may be configured to convey radiation from one or more of the radiation sources to each of the lithography apparatuses.

[0006]

[0006] Extreme ultraviolet (EUV) radiation is used for applications such as extreme ultraviolet lithography (EUVL). An EUV source can generate EUV radiation by illuminating a target material such as tin (Sn) with radiation from a high-power laser radiation source. Illuminating the target material with laser radiation generates a laser-produced plasma (LPP), which can consequently emit EUV radiation.

Summary of the Invention

[0007]

[0007] When a target material such as tin is illuminated with laser radiation to generate a plasma, a portion of the target material becomes debris. For example, the target material debris may include Sn vapor, SnH4 vapor, Sn atoms, Sn ions, Sn clusters, Sn microparticles, Sn nanoparticles, and Sn deposits. If Sn debris accumulates on one or more of the inner walls of the EUV collector or EUV vessel, the efficiency, lifetime, and usefulness of the EUV collector may be reduced.

[0008]

[0008] EUV radiation can be generated using a plasma. The plasma can be generated, for example, by directing a laser beam at the fuel of the radiation source. The resulting plasma can emit EUV radiation. A portion of the fuel becomes debris, which may accumulate on one or more components of the radiation source.

[0009]

[0009] As a result, one or more components of the radiation source may be contaminated, and it may be difficult to remove this contamination. Contamination of one or more components of the radiation source by debris may cause a degradation in the performance of the radiation source, such as a reduction in the quality of the EUV radiation produced, and ultimately a degradation in the performance of the associated lithographic apparatus. This may ultimately result in a longer downtime of the lithographic apparatus while the components of the radiation source are being cleaned or replaced. Embodiments of the present invention arise in such circumstances.

[0010]

[0010] Embodiments of the present disclosure relate to systems and apparatuses associated with EUV containers having a container inner wall gas supply, and more particularly to systems and apparatuses for providing a flow pattern of a gas stream capable of reducing debris contamination on one or more container inner walls within an EUV container. One embodiment includes introducing gas into the container via a showerhead or curtain flow and discharging the gas from the container via a discharge configuration. In one configuration, the container is designed to have an asymmetric discharge configuration. In another configuration, the container is designed to have a symmetric discharge configuration. It should be understood that the present disclosure can be implemented by various means such as instructions on a computer-readable medium configured to execute a process, apparatus, system, device, or method. Some embodiments of the inventions of the present disclosure will be described below.

[0011]

[0011] In one embodiment, an EUV source comprises a container having a container inner wall and an intermediate focus (IF) region. This embodiment includes an EUV collector disposed inside the container and connected to the container inner wall. The EUV collector comprises a reflective surface configured to directionally face the IF region of the container. This embodiment also includes a showerhead disposed along at least a portion of the container inner wall. The showerhead comprises a plurality of nozzles for introducing gas into the container. This embodiment also includes one or more discharge portions for removing the gas introduced into the container, the one or more discharge portions being oriented near the IF region so as to flow the gas introduced into the container away from the EUV collector.

[0012]

[0012] In another embodiment, the EUV source comprises a container having an inner container wall and an intermediate focus (IF) region. This embodiment comprises an EUV collector disposed inside the container and connected to the inner container wall, the EUV collector having a reflective surface configured to directionally face the IF region of the container. This embodiment comprises a first gas source disposed near the reflective surface of the EUV collector and having a plurality of inlets for introducing gas into the container. This embodiment also comprises a showerhead disposed along at least a portion of the inner container wall and having a plurality of nozzles for introducing gas into the container. An exhaust portion disposed at an azimuthally asymmetric position along the inner container wall is also provided for exhausting gas from the container. In certain embodiments, the asymmetric exhaust portion may be oriented, for example, at a downward inclination angle in the direction of gravity. In these and other embodiments, the asymmetric exhaust portion may be oriented to generally face a region near the ceiling area above the EUV collector in the inner container wall in the direction of gravity.

[0013]

[0013] In another embodiment, the EUV source comprises a container having an inner container wall and an intermediate focus (IF) region. This embodiment comprises an EUV collector disposed inside the container and connected to the inner container wall, the EUV collector having a reflective surface configured to directionally face the IF region of the container. This embodiment comprises a container wall gas source disposed laterally along at least a portion of a part of the inner container wall. According to this embodiment, the container wall gas source comprises a plurality of nozzle assemblies. Each of the nozzle assemblies may comprise a first outlet and a second outlet for introducing gas into the container, the first outlet being configured to introduce gas in a first direction away from a second direction in which the second outlet is configured to introduce gas. In these embodiments, both outlets are configured to introduce gas along the perimeter of the inner container wall.

[0014]

[0014] According to one aspect, there is provided a radiation source including a chamber (i.e., a container) including a plasma formation region, a radiation collector disposed in the chamber, configured to collect radiation emitted from the plasma formation region and direct the collected radiation to an intermediate focus region, a debris mitigation system configured to direct a first gas flow from the intermediate focus region to the plasma formation region, and an induction device disposed in the chamber such that the first gas flow is directed circumferentially.

[0015]

[0015] The induction device may be arranged such that the first gas flow is directed symmetrically around and / or diffused by the induction device.

[0016]

[0016] The debris mitigation system may be configured to direct a second gas flow from the radiation collector to the plasma formation region.

[0017]

[0017] The induction device may be configured to reduce the interaction between the first gas flow and the second gas flow.

[0018]

[0018] The induction device may be configured to prevent the interaction between the first gas flow and the second gas flow.

[0019]

[0019] The induction device may be configured to prevent the formation of a jet of the first gas flow toward the radiation collector.

[0020]

[0020] The induction device may be disposed in the chamber so as to extend at least partially along the optical axis of the radiation collector.

[0021]

[0021] The induction device may be disposed in or near the intermediate focus region.

[0022]

[0022] The guiding device may be arranged in a tapered shape from a first end of the guiding device towards a second end of the guiding device. The first end of the guiding device may include an enlarged portion. The second end of the guiding device may include a pointed portion or a rounded portion.

[0023]

[0023] The guiding device may be arranged in the chamber such that a first end of the guiding device is distally arranged from an intermediate focus region. The guiding device may be arranged in the chamber such that a second end of the guiding device is arranged in or proximally to the intermediate focus region.

[0024]

[0024] The guiding device may comprise at least one opening or a plurality of openings. Each of the at least one opening, the plurality of openings or the plurality of openings may be configured to direct a third gas flow towards the radiation collector.

[0025]

[0025] Each of the at least one opening, each of the plurality of openings or the plurality of openings may be arranged in the guiding device such that a third gas flow from the at least one opening, each of the plurality of openings or the plurality of openings interacts with the first gas flow to direct or push, for example, the first gas flow near at least a portion of the chamber.

[0026]

[0026] The guiding device may comprise a heating element. The heating element may be configured to increase the temperature of the guiding device.

[0027]

[0027] The heating element may be configured to increase the temperature of the guiding device to a first temperature at which an increased amount of the first gas flow is directed around the guiding device. The heating element may be configured to maintain the temperature of the guiding device below a second temperature at which the diffusion of debris present on the guiding device is enhanced.

[0028]

[0028] The guiding device may be configured to be cooled by a coolant. The coolant may be supplied or may be capable of being supplied by a coolant source.

[0029]

[0029] The radiation source may include a debris receiving surface. The debris receiving surface may be disposed within the chamber so as to suppress or prevent debris from reaching the intermediate focus region.

[0030]

[0030] The debris receiving surface may be disposed so as to intersect or extend across the optical axis of the radiation collector.

[0031]

[0031] The induction device may be disposed between the debris receiving surface and the intermediate focus region.

[0032]

[0032] The debris receiving surface may be disposed so as to extend over or overlap at least a portion or the entirety of the induction device such that debris generated in the plasma formation region impinges on the debris receiving surface.

[0033]

[0033] The debris receiving surface may be included in, be a part of, or be provided by the induction device.

[0034]

[0034] According to one aspect, there is provided a method for reducing debris deposition in a radiation source, the method including directing a first gas flow from an intermediate focus region of the radiation source towards a plasma generation region of the radiation source and directing the first gas flow around an induction device disposed within the chamber of the radiation source.

[0035]

[0035] According to one aspect, there is provided an extreme ultraviolet (EUV) source including a container having an inner wall and an intermediate focus (IF) region, an EUV collector disposed within the container and connected to the inner wall of the container, the EUV collector having a reflective surface configured to face directionally towards the IF region of the container, a showerhead disposed along at least a portion of the inner wall of the container, the showerhead including a plurality of nozzles for introducing gas into the container and having at least one inlet for supplying gas therein, and one or more discharge portions disposed along at least a portion of the inner wall of the container so as to flow gas away from the EUV collector for removing gas introduced into the container.

[0036]

[0036] The EUV source may further include a material target region disposed within a container for generating plasma radiation that is collected by a reflective surface of the EUV collector and directed towards an IF region for incidence on at least a portion of the lithographic apparatus. By introducing gas into the container via a plurality of nozzles, it may be possible to protect the inner wall of the container from material deposition.

[0037]

[0037] The plurality of nozzles may be oriented in a direction away from the inner surface of the inner wall of the container along at least a portion of the inner surface of the inner wall of the container.

[0038]

[0038] The inner wall of the container may have a conical shape, a cylindrical shape, or a polyhedral shape.

[0039]

[0039] The showerhead may extend in a circumferential direction and a transverse direction along at least a portion of the inner wall of the container.

[0040]

[0040] The EUV source may further include an outer wall of the container having one or more exhaust ports surrounding the container.

[0041]

[0041] The showerhead may include one or more zones each including at least a portion of the plurality of nozzles and realizing individually controllable zones for introducing gas into the container by individually supplying gas to each.

[0042]

[0042] The inner wall of the container may be defined by a smooth surface, a blade surface, or a combination of a smooth surface and a blade surface.

[0043]

[0043] According to one aspect, there is provided an extreme ultraviolet (EUV) source comprising: a container having an inner wall of the container and an intermediate focus (IF) region; an EUV collector disposed inside the container and connected to the inner wall of the container, the EUV collector comprising a reflective surface configured to directionally face the IF region of the container; a first gas source provided with a first plurality of inlets disposed near the reflective surface of the EUV collector for introducing gas into the container; a showerhead disposed along at least a part of the inner wall of the container, the showerhead comprising a plurality of nozzles for introducing gas into the container and having at least one inlet for supplying gas inside; and a discharge portion disposed at an azimuthally asymmetric position along the inner wall of the container for discharging gas from the container.

[0044]

[0044] The discharge portion may be further oriented near a first region of the inner wall of the container. The first region of the inner wall of the container may generally face a second region located above the EUV collector of the inner wall of the container in the direction of gravity. The discharge portion may enable the gas introduced by the first gas source and the plurality of nozzles to flow in a direction away from the second region during operation of the EUV source.

[0045]

[0045] The plurality of nozzles may be distributed at least partially along a region of the inner wall of the container located above the EUV collector of the inner wall of the container in the direction of gravity.

[0046]

[0046] The plurality of nozzles may be oriented in a direction away from the inner surface of the inner wall of the container along the inner surface of the inner wall of the container. The orientation of the plurality of nozzles may enable a gas flow that is at least partially directed in a direction away from at least a part of the inner surface of the inner wall of the container.

[0047]

[0047] The plurality of nozzles may be disposed at least partially along a ceiling region of the inner wall of the container located above the EUV collector of the inner wall of the container in the direction of gravity. The plurality of nozzles may be oriented in a direction facing away from the ceiling region. By introducing gas through the plurality of nozzles, a diffusion barrier adjacent to the ceiling region for removing debris may be provided.

[0048]

[0048] The showerhead may include one or more zones. Each of the one or more zones may include at least a portion of a plurality of nozzles. Each of the one or more zones may be individually supplied with gas to implement an individually controllable zone for introducing gas into the container.

[0049]

[0049] The inner wall of the container may have a conical shape, a cylindrical shape, or a polyhedral shape.

[0050]

[0050] A container having an inner wall of the container and an intermediate focus (IF) region, an EUV collector disposed inside the container and connected to the inner wall of the container, the EUV collector having a reflective surface configured to directionally face the IF region of the container, and a plurality of nozzle assemblies disposed laterally at least partially along the inner wall of the container, each having at least a first outlet and a second outlet for introducing gas into the container, the first outlet being configured to introduce gas in a first direction away from a second direction in which the second outlet is configured to introduce gas, a container wall gas source, a discharge portion near the IF region for discharging the gas introduced into the container and allowing the gas introduced by the container wall gas source to flow away from the EUV collector, an extreme ultraviolet (EUV) source is provided.

[0051]

[0051] The first direction and the second direction in which gas can be introduced by the first outlet and the second outlet of each of the plurality of nozzle assemblies may be oriented at least partially along the periphery of the inner wall of the container to enable a curtain flow of gas along the periphery of the inner wall of the container.

[0052]

[0052] At least a portion of the plurality of nozzle assemblies may further include a third outlet for introducing gas into the container. The third outlet may be configured to introduce gas in a direction away from the inner wall of the container.

[0053]

[0053] The plurality of nozzle assemblies may be distributed at least partially along a first region located above the EUV collector on the inner wall of the container in the direction of gravity during the operation of the EUV source. The discharge part may be further oriented near a second region that can face the first region of the inner wall of the container so that the gas introduced into the container can flow away from the first region of the inner wall of the container.

[0054]

[0054] The inner wall of the container may have a conical shape, a cylindrical shape, or a polyhedral shape.

[0055]

[0055] According to one aspect, there is provided a radiation source including a chamber including an inner wall and a material target region, a radiation collector disposed in the chamber and configured to collect radiation emitted from the material target region and direct the collected radiation to an intermediate focus region, a debris mitigation system configured to direct a first gas flow from the intermediate focus region to the material target region and a second gas flow into the chamber from a portion of the inner wall of the chamber, an induction device disposed in the chamber so that the first gas flow is directed peripherally, and a discharge part for removing the gas supplied by the debris mitigation system from the chamber.

[0056]

[0056] The discharge part may be disposed at an azimuthally asymmetric position so as to extend from a portion of the inner wall of the chamber.

[0057]

[0057] The debris mitigation system may include a shower head. The shower head may be disposed along at least a portion of the inner wall of the chamber. The shower head may include a plurality of nozzles for introducing the second gas flow into the chamber.

[0058]

[0058] The induction device may be configured to reduce the interaction between the first gas flow and the second gas flow.

[0059]

[0059] The debris mitigation system may be configured to direct a third gas flow from a position at or near the position of the induction device in the chamber towards the material target area.

[0060]

[0060] The induction device may be configured to reduce the interaction between the first gas flow and the third gas flow.

[0061]

[0061] The debris mitigation system may be configured to direct a fourth gas flow from the radiation collector towards the material target area.

[0062]

[0062] The induction device may be configured to reduce the interaction between the first gas flow and the fourth gas flow.

[0063]

[0063] The induction device may be arranged in a tapered shape from a first end of the induction device towards a second end of the induction device. The first end of the induction device may include an enlarged portion. The second end of the induction device may include a pointed portion or a rounded portion.

[0064]

[0064] The induction device may be arranged in the chamber such that the first end of the induction device is distally located from the intermediate focus region and the second end of the induction device is located at or proximally to the intermediate focus region.

[0065]

[0065] The induction device may be arranged in the chamber so as to extend at least partially along the optical axis of the radiation collector.

[0066]

[0066] The induction device may include at least one opening or a plurality of openings. Each of the at least one opening, the plurality of openings, or the plurality of openings may be configured to direct a fifth gas flow towards the radiation collector.

[0067]

[0067] At least one opening, each opening of a plurality of openings, or the plurality of openings may be arranged in an induction device such that a fifth gas flow from at least one opening, each opening of the plurality of openings, or the plurality of openings interacts with the first gas flow to direct or push the first gas flow near at least a portion of the inner wall of the chamber.

[0068]

[0068] The induction device may comprise a heating element. The heating element may be configured to raise the temperature of the induction device.

[0069]

[0069] The heating element may be configured to raise the temperature of the induction device to a first temperature at which an increased amount of the first gas flow is directed around the induction device. The heating element may be configured to maintain the temperature of the induction device below a second temperature at which the diffusion of debris present on the induction device is enhanced.

[0070]

[0070] The induction device may be configured to be cooled by a coolant. The coolant may be supplied or may be capable of being supplied by a coolant source.

[0071]

[0071] The radiation source may comprise a debris receiving surface. The debris receiving surface may be disposed within the chamber so as to inhibit or prevent debris from reaching the intermediate focus region.

[0072]

[0072] The debris receiving surface may be included in, be part of, or be provided by the induction device.

[0073]

[0073] According to one aspect, a method for reducing debris deposition in a radiation source, the method comprising directing a first gas flow from an intermediate focus region of the radiation source to a material target region of the radiation source, directing a second gas flow from a portion of an inner wall of a chamber of the radiation source into the chamber, directing the first gas flow around an induction device disposed within the chamber of the radiation source, and removing gas from the chamber.

[0074]

[0074] According to one aspect, there is provided a radiation system comprising a laser and (i) a radiation source described herein, or (ii) an extreme ultraviolet (EUV) source described herein.

[0075]

[0075] According to one aspect, there is provided a lithography system comprising a lithography apparatus configured to project a pattern from a patterning device onto a substrate, and a radiation system described herein configured to provide at least a portion of the radiation to the lithography apparatus.

[0076]

[0076] According to one aspect, there is provided a radiation source comprising a chamber including an inner wall and a material target region, a radiation collector disposed within the chamber and configured to collect radiation emitted from the material target region and direct the collected radiation to an intermediate focus region, a debris mitigation system comprising a first gas supply system and a second gas supply system, and an exhaust configured to remove gas supplied by the debris mitigation system from the chamber, wherein the first gas supply system is configured to direct a first gas flow from the intermediate focus region to the material target region or a plasma formation region and comprises one or more apertures arranged to direct the first gas flow into the chamber in a direction substantially opposite to the propagation direction of the radiation beam, and the second gas supply system is configured to direct a second gas flow in a direction substantially perpendicular to or inclined at an angle to the propagation direction of the first gas flow and comprises one or more apertures arranged to direct the second gas flow in said direction.

[0077]

[0077] Other aspects of a method and apparatus for protecting a container wall with one or more gas flow inlets and an asymmetric exhaust to improve the collector lifetime of an LPP EUV source will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the method and apparatus.

[0078]

[0078] It will be readily apparent to those skilled in the art that the various aspects and features of the invention described above and below may be combined with various other aspects and features of the invention.

Brief Description of the Drawings

[0079]

[0079] Embodiments of the present invention will be described below by way of example with reference to the accompanying schematic diagrams.

[0080]

Figure 1

[0080] A lithography apparatus and a lithography system including a radiation source according to an embodiment are shown.

Figure 2

[0081] A radiation source including a debris reduction system of the lithography system of FIG. 1 is shown.

Figure 3

[0082] A simulation of a first gas flow and a second gas flow of the radiation source of FIG. 2 is shown.

Figure 4A

[0083] A part of the radiation source of FIG. 2 including an induction device is shown.

Figure 4B

[0084] Another embodiment of the induction device of FIG. 4A is shown.

Figure 4C

[0085] Another embodiment of the induction device of FIG. 4A is shown.

Figure 4D

[0086] Another embodiment of the induction device of FIG. 4A is shown.

Figure 5

[0087] A part of the radiation source of FIG. 2 including another embodiment of the induction device is shown.

Figure 6

[0088] A part of the radiation source of FIG. 4A including a debris receiving surface is shown.

Figure 7A

[0089] A simulation of a first gas flow in a part of the radiation source of FIG. 2 including the debris receiving surface of FIG. 6 is shown.

Figure 7B

[0090] A simulation of debris deposition in a part of the radiation source of FIG. 7A is shown.

Figure 8A

[0091] A simulation of a first gas flow in a part of the radiation source of FIG. 2 including the induction device of FIG. 4A is shown.

Figure 8B

[0092] Shows a simulation of debris deposition in a portion of the radiation source of FIG. 8A.

Figure 9A

[0093] It is a simplified schematic diagram of an embodiment of an EUV container having a shower head disposed along at least a part of the inner wall of the container of the EUV container.

Figure 9B

[0094] It is a simplified schematic diagram of an embodiment of an EUV container having a shower head for introducing gas into the container through a first plurality of nozzles and a second plurality of nozzles.

Figure 9C

[0095] It is a simplified schematic diagram of an embodiment of an EUV container having a shower head provided with a plurality of nozzles controlled by a common gas supply system.

Figure 9D

[0096] It is a simplified schematic diagram of an embodiment of an EUV container having a shower head including a plurality of zones each of which can be separately controlled by an individual gas supply system.

Figure 10

[0097] It is a simplified schematic diagram of an embodiment of an EUV container having a shower head and an asymmetric discharge part.

Figure 11

[0098] It is a simplified schematic diagram of an embodiment of an EUV container oriented at an upward inclination angle during operation.

Figure 12A

[0099] It is a cross-sectional view of an embodiment of an EUV container showing a plurality of flow paths through which gas is introduced into the container from different supply parts and discharged by a symmetric discharge structure.

Figure 12B

Figure 13

Figure 14

Figure 15A

Figure 15B

Figure 16A

Figure 16B

Figure 17

Figure 18A

Figure 18B

Figure 19A

Figure 19B

Figure 19C

Figure 20

Figure 21

Figure 22A

Figure 22B

Figure 22C

Embodiments for Carrying Out the Invention

[0081] [000118] FIG. 1 shows a lithography system including a radiation source according to an embodiment. This lithography system includes a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithography apparatus LA includes an illumination system IL, a support structure MT configured to support a patterning device MA (for example, a mask), a projection system PS, and a substrate table WT configured to support a substrate W. The illumination system IL is configured to condition the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam B (which is patterned by the mask MA here) onto the substrate W. The substrate W can include a previously formed pattern. In this case, the lithography apparatus aligns the patterned radiation beam B with the previously formed pattern on the substrate W.

[0082] [000119] The radiation source SO, the illumination system IL, and the projection system PS can all be constructed and arranged so as to be isolated from the external environment. A gas at a pressure lower than atmospheric pressure (for example, hydrogen) may be provided inside the radiation source SO. A vacuum may be provided inside the illumination system IL and / or the projection system PS. A small amount of gas at a pressure considerably lower than atmospheric pressure (for example, hydrogen) may be provided inside the illumination system IL and / or the projection system PS.

[0083] [000120] The radiation source SO shown in FIG. 1 is of a type sometimes called a laser-produced plasma (LPP) source. The laser 1 may be, for example, a CO2 laser and is configured to impart energy to a fuel such as tin (Sn) provided from a fuel dispenser 3 via a laser beam 2. Although tin will be referred to in the following description, any suitable fuel can be used. The fuel may be, for example, liquid and may be, for example, a metal or an alloy. The fuel dispenser 3 may comprise a nozzle configured to direct tin, for example in the form of droplets, along an orbit towards a plasma formation region 4. The laser beam 2 is incident on the tin in the plasma formation region 4. By imparting laser energy to the tin, a plasma 7 is generated in the plasma formation region 4. Radiation including EUV radiation is emitted from the plasma 7 during the de-excitation and recombination of the ions of the plasma.

[0084] [000121] The EUV radiation is collected and focused by a near-normal incidence radiation collector 5 (sometimes more generally called a normal incidence radiation collector). The collector 5 may have a multilayer structure configured to reflect EUV radiation (for example, EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 may have an elliptical configuration with two elliptical foci. The first focus may be in the plasma formation region 4. The second focus 6a may be located in or near the intermediate focus region 6.

[0085] [000122] The laser 1 may be remote from the radiation source SO. In this case, the laser beam 2 may be sent from the laser 1 to the radiation source SO using a beam delivery system (not shown) including, for example, suitable guiding mirrors and / or a beam expander, and / or other optical systems. The laser 1 and the radiation source SO can be regarded together as a radiation system.

[0086] [000123] The radiation reflected by the collector 5 forms a radiation beam B. The radiation beam B is focused at point 6a and forms an image of the plasma formation region 4. This image serves as the virtual radiation source of the illumination system IL. The point 6a at which the radiation beam B is focused may be referred to as an intermediate focus 6a. The radiation source SO is arranged such that the intermediate focus 6a is located at or near the opening 8 of the closed structure 9 of the radiation source.

[0087] [000124] The radiation beam B enters the illumination system IL from the radiation source SO. The illumination system IL is configured to adjust the radiation beam. The illumination system IL may comprise a facet field mirror device 10 and a facet pupil mirror device 11. The facet field mirror device 10 and the facet pupil mirror device 11 cooperate to impart a desired cross-sectional shape and a desired angular intensity distribution to the radiation beam B. The radiation beam B is incident from the illumination system IL on a patterning device MA held by a support structure MT. The patterning device MA reflects the radiation beam B and imparts a pattern thereto. The illumination system IL may comprise other mirrors or devices in addition to or instead of the facet field mirror device 10 and the facet pupil mirror device 11.

[0088] [000125] After being reflected from the patterning device MA, the patterned radiation beam B is incident on a projection system PS. The projection system comprises a plurality of mirrors 13, 14 configured to project the radiation beam B onto a substrate W held on a substrate table WT. The projection system PS can apply a reduction factor to the radiation beam and form an image having features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 can be applied. In FIG. 1, the projection system PS has two mirrors 13, 14, but the projection system may comprise any number of mirrors (for example, six mirrors).

[0089] [000126] The radiation source SO shown in FIG. 1 may include components not shown. For example, a spectral filter may be provided for the radiation source. The spectral filter may be substantially transparent to EUV radiation but substantially block other radiation wavelengths such as infrared radiation.

[0090] [000127] FIG. 2 schematically shows an exemplary radiation source SO including a debris mitigation system 15. For clarity, in FIG. 2, the laser beam 2 and the radiation beam B are shown by dashed lines. The debris mitigation system 15 is configured to direct a first gas flow 16 from the intermediate focus region 6 to the plasma formation region 4. For example, the debris mitigation system 15 may include a first gas supply system 17. The first gas supply system 17 may be configured to supply the first gas flow 16 toward the plasma formation region 4. The first gas supply system 17 may include one or more openings 18, such as one or more nozzles or slits, and the one or more openings 18 are provided in or near the intermediate focus region 6, such as the intermediate focus 6. The one or more openings 18 may be arranged to generate the first gas flow 16 toward the collector 5. For example, the one or more openings 18 may be arranged to direct the first gas flow 16 in a direction opposite (e.g., substantially opposite) to the propagation direction of the radiation beam B. The first gas flow 16 may have a flow rate sufficient to suppress or prevent debris from moving toward the intermediate focus 6a. The first gas supply system 17 may be regarded as or included in a dynamic gas lock (DGL) system. When the fuel is illuminated with the laser beam 2 to generate the plasma 7, a part of the fuel may become debris. The debris may include, for example, particulate debris such as Sn clusters, Sn microparticles, Sn nanoparticles, and / or Sn deposits, and molecular and / or atomic debris such as, for example, Sn vapor, SnH x vapor, Sn atoms, Sn ions, etc.

[0091] [000128] The debris mitigation system 15 may be configured to direct a second gas flow 19 from the collector 5 towards the plasma formation region 4. For example, the debris mitigation system 15 may include a second gas supply system 20. The second gas supply system 20 may be configured to supply the second gas flow 19 from the collector 5 towards the plasma formation region 4. The second gas flow 19 is directed towards the plasma formation region 4 and can suppress or prevent debris generated by the plasma 7 from reaching the collector 5. For example, the second gas supply system 20 may be arranged to supply the second gas flow 19 from the central opening 5a of the collector 5. In other embodiments, it will be understood that a second gas supply system or a part thereof may be provided in the collector. For example, the second gas supply system may include one or more outlets, and the one or more outlets may be arranged within the collector. Additionally or alternatively, the second gas supply system may be configured to supply the second gas flow from the peripheral portion of the collector.

[0092] [000129] The second gas flow 19 may have a flow rate sufficient to prevent debris from depositing on the collector 5. For example, the second gas flow 19 may have a flow rate in the range of about 30 to 200 slm (standard liters per minute), desirably about 50 to 150 slm. The flow rate of the second gas flow 19 may be selected according to the arrangement or shape of the second gas supply system 20.

[0093] [000130] The first gas flow 16 may be selected so as to prevent debris from entering the illumination system IL. The flow rate of the first gas flow 16 may be selected according to the gas used for the first gas flow 16, the velocity of the gas used for the first gas flow 16, the density or pressure of the gas used for the first gas flow 16, the size of the debris, for example particulate debris, the velocity of the debris, and / or the direction of debris diffusion in the radiation source SO. Additionally or alternatively, the flow rate of the first gas flow 16 may be selected according to the arrangement or shape of the first gas supply system 17. For example, the flow rate of the first gas flow 16 may be selected according to the number of openings 18, the width (e.g., diameter) of each opening 18 of the first gas supply system 17 and / or the width (e.g., diameter), outer circumference or dimensions of the intermediate focus region 6. For example, the maximum velocity of the gas used for the first gas flow 16 may be in the range of about 1000 to 3000 m / s.

[0094] [000131] The first gas flow 16 may have a flow rate in the range of about 5 to 30 slm. A flow rate of about 7 slm may be sufficient to prevent the molecules and / or atomic debris generated at the radiation source SO from entering the illumination system IL. A flow rate of the first gas flow greater than 7 slm may be required to suppress the particulate debris from reaching the illumination system IL. For example, a flow rate of the first gas flow 16 greater than 15 slm may be required to suppress the particulate debris from reaching the illumination system. At a flow rate greater than 15 slm, an asymmetric flow of the first gas flow 16 may be observed. In other words, the first gas flow 16 may be pushed towards the inner wall of the radiation source SO as described below.

[0095] [000132] FIG. 3 shows the simulated first and second gas flows 16, 19 within the radiation source SO when the flow rate of the first gas flow 16 is, for example, 15 slm or more. From FIG. 3, it can be seen that the first gas flow 16 is pressed against the inner wall 21 of the radiation source SO (e.g., of the chamber 23). This is considered to be due to the interaction between the first gas flow 16 and the second gas flow 19. The interaction between the first gas flow 16 and the second gas flow 19 may result in the formation of a jet of the first gas flow 16 towards a part of the collector 5. As a result of the formation of the jet of the first gas flow 16, debris, such as particulate debris, may deposit on the collector 5. This may increase the contamination of the collector 5 and / or the radiation source SO.

[0096] [000133] Figure 4A schematically shows a radiation source SO according to an embodiment. The radiation source SO shown in Figure 4A is the same as that shown in Figure 2 except that it further includes an induction device. The induction device may be provided in the form of a flow splitter 22. For clarity, the first and second gas supply systems 17, 20, one or more openings 18, the laser 1, the laser beam 2, and the radiation beam B are omitted in Figure 4A. However, it will be understood that the exemplary radiation source SO shown in Figure 4A may have the characteristics of the radiation source SO described above in connection with Figures 1 to 3. The radiation source may include a chamber 23. The flow splitter 22 is disposed within the chamber 23 such that the first gas flow 16 is directed around the flow splitter 22. For example, the flow splitter 22 may be arranged such that the first gas flow is symmetrically directed around the flow splitter 22. The flow splitter 22 may be configured to diffuse or disperse the first gas flow 16, for example, symmetrically. By disposing the flow splitter 22 within the chamber 23, it is possible to suppress at least a portion of the first gas flow 16 from recirculating within the chamber 23. This may reduce the debris deposited on the inner wall 21 of the radiation source SO. Additionally or alternatively, by disposing the flow splitter 22 within the chamber 23 such that the first gas flow 16 is directed around the flow splitter 22, it is possible to suppress or prevent, for example, contamination of the flow splitter 22 by debris.

[0097] [000134] The flow splitter 22 is disposed within the chamber 23 of the radiation source SO and can maintain the maximum velocity of the gas used for the first gas flow 16 at the first position of the radiation source SO. At the first position, the velocity of the gas used for the first gas flow 16 may (or may substantially) coincide with the maximum velocity of the gas used for the first gas flow 16 when no flow splitter is disposed within the chamber 23 of the radiation source SO, for example. The flow splitter 22 is disposed within the radiation source SO and can diffuse or disperse the first gas flow 16 to prevent or suppress, for example, the recirculation of a portion of the first gas flow 16 in the direction toward the intermediate focus 6a. The flow splitter 22 is disposed within the chamber 23 of the radiation source SO and can diffuse or disperse the first gas flow 16 at the second position, and the second position may be spaced apart from or away from the intermediate focus 6a. The flow splitter 22 may be disposed within the chamber 23 of the radiation source such that the maximum velocity of the gas used for the first gas flow 16 decreases at the second position and / or the minimum velocity of the gas of the first gas flow 16 that can be directed in a direction away from the intermediate focus 6a increases.

[0098] [000135] The flow splitter 22 may be configured to suppress or prevent the interaction between the first gas flow 16 and the second gas flow 19. The flow splitter 22 may be configured to prevent, for example, the formation of a jet of the first gas flow 16 toward a part of the collector 5. Thereby, it may be possible to use a flow rate of the first gas flow 16 greater than 7 slm.

[0099] [000136] Referring to FIG. 4A, the flow splitter 22 is disposed within the chamber 23 and extends into a portion of the chamber 23. For example, the flow splitter 22 may be disposed so as to extend at least partially along the optical axis OA of the collector 5. In other words, the flow splitter 22 may be disposed within the chamber 23 such that the central axis, i.e., the longitudinal axis A, of the flow splitter 22 coincides with at least a part of the optical axis OA of the collector 5. The radiation source SO may include a conical portion 23a, which may be a part of the chamber 23. The conical portion 23a may be disposed so as to extend from the intermediate focus 6a towards or near the collector 5. The flow splitter 22 may be disposed in the conical portion 23a and may, for example, extend at least partially along the central axis, i.e., the longitudinal axis, of the conical portion 23a. The central axis, i.e., the longitudinal axis, coincides with at least a part of the optical axis OA of the collector 5 in this example. This may result in a symmetric arrangement of the flow splitter 22 in the chamber 23, for example, the conical portion 23a. It will be understood that the exemplary chambers described herein are not limited to those including a conical portion. For example, the chamber or a portion thereof may have any suitable shape that reduces the volume of the chamber or a portion thereof, for example, without blocking the radiation beam.

[0100] [000137] Referring to FIG. 4A, the flow splitter 22 is disposed in or near the intermediate focus region 6. For example, the flow splitter 22 is disposed in or near the intermediate focus region 6 such that the flow splitter 22 can act on the first gas flow 16. The flow splitter 22 may be disposed at a distance from the intermediate focus 6a. The distance of the flow splitter 22 from the intermediate focus 6a may be in the range of 5 to 15 cm. However, it should be understood that the arrangement of the flow splitter 22 within the radiation source SO is not limited to such a distance and other distance values may be selected. For example, the distance may be selected according to the space available in or near the intermediate focus region and / or the heat load that can act on the flow splitter 22 due to radiation in the intermediate focus region. In other words, the distance may be selected such that the thermal effect on the flow splitter 22, such as melting of the flow splitter 22, is minimized or prevented. As discussed above, the flow splitter 22 may be arranged to extend at least partially along the central axis, i.e., the longitudinal axis, of the conical portion 23a, and the central axis, i.e., the longitudinal axis, coincides with at least a part of the optical axis OA of the collector 5 in this example. With this arrangement, the flow splitter 22 may be able to direct the first gas flow 16 symmetrically around the flow splitter 22 and / or prevent the formation of a jet of the first gas flow 16, for example, to suppress or prevent the interaction between the first and second gas flows 16, 19.

[0101] [000138] The exemplary flow splitter 22 shown in FIG. 4B is arranged to be tapered from a first end 22a towards a second end 22b. The first end 22a of the flow splitter 22 can include or define an enlarged portion. The flow splitter 22 may be arranged within the chamber 23, for example its conical portion 23a, such that the first end 22a of the flow splitter, for example the enlarged portion, is located distally from the intermediate focus region 6. The second end 22b of the flow splitter 22 can define or include a pointed tip. The flow splitter 22 may be arranged within the chamber 23, for example its conical portion 23a, such that the second end 22b of the flow splitter 22, for example the pointed tip, is located in or proximal to the intermediate focus region 6. The exemplary flow splitter 22 shown in FIG. 4B has a conical shape.

[0102] [000139] FIG. 4C shows another exemplary configuration of the flow splitter 22. The flow splitter 22 shown in FIG. 4C is similar to that shown in FIG. 4B. The first end 22a of the flow splitter 22 defines or includes an enlarged portion. The second end 22b of the flow splitter 22 includes or defines a rounded portion. The exemplary flow splitter shown in FIG. 4C may be considered to have a substantially frustoconical shape. It should be understood that the flow splitters disclosed herein are not limited to conical or frustoconical shapes. In other examples, the flow splitter may have a conical or frustoconical shape with one or more flat portions. Alternatively, the flow splitter may have a spiral or helical shape.

[0103] [000140] Referring to FIGS. 4B and 4C, for example, the length or dimension of the flow splitter 22 along the vertical axis or central axis A of the flow splitter 22 may be selected according to the dimensions, volume and / or shape of the chamber 23 of the radiation source SO. The length or dimension of the flow splitter 22 may be selected such that, for example, when the flow splitter 22 is disposed within the chamber 23 of the radiation source SO, the flow splitter 22 interacts with the first gas flow 16 and / or the flow splitter directs the first gas flow around the flow splitter 22. An exemplary length or dimension of the flow splitter 22 along the vertical axis or central axis A of the flow splitter 22 may include from about 3 to 30 cm, such as 10 to 20 cm. However, it should be understood that the exemplary flow splitters disclosed herein are not limited to such lengths or dimensions.

[0104] [000141] The radiation source SO may comprise a heating element 24, and the heating element 24 may be part of or included in the flow splitter 22. The heating element 24 may be configured to increase the temperature of the flow splitter 22, for example, to increase the amount of the first gas flow 16 directed around the flow splitter 22.

[0105] [000142] The heating element 24 may be configured to raise the temperature of the flow splitter 22 to a first temperature or higher at which an increased amount of the first gas flow is directed around the flow splitter 22. For example, as a result of the temperature of the flow splitter 22 rising to the first temperature or higher, when at least a portion of the first gas flow 16 contacts the flow splitter 22, for example, the velocity of at least some of the atoms of the first gas flow 16 may increase. When the temperature of the flow splitter 22 rises to the first temperature or higher, heat may be conducted to a portion of the first gas flow 16 that contacts the flow splitter 22. By heat being conducted to a portion of the first gas flow 16, the gas of a portion of the first gas flow may expand and / or the viscosity of the gas of a portion of the first gas flow may increase. In other words, the gas of a portion of the first gas flow that contacts the flow splitter 22 may have an increased viscosity. The gas of a portion of the first gas flow 16 having an increased viscosity may act on another portion of the first gas flow incident on the flow splitter 22 and / or direct another portion of the first gas flow 16 around the flow splitter 22. In other words, by the viscosity of a portion of the gas of the first gas flow 16 increasing, the effective dimension of the flow splitter 22 can be considered to be larger than the actual dimension of the flow splitter 22.

[0106] [000143] The first temperature may be equal to or higher than the melting temperature of the fuel used to generate the plasma 7. In other words, the first temperature may be selected according to the fuel used to generate the plasma 7. For example, if tin is used as the fuel, the heating element 24 may be configured to raise the temperature of the flow splitter to a temperature of about 230 °C or higher (substantially corresponding to the melting temperature of tin). At a temperature below 200 °C, the fuel deposited on the flow splitter 22, for example tin, may be solid. The solid fuel may diffract or block at least a portion of the radiation beam B directed towards the intermediate focus 6a.

[0107] [000144] The heating element 24 may be configured to maintain the temperature of the flow splitter 22 below a second temperature. At a temperature equal to or higher than the second temperature, the diffusion of debris that may be present on the flow splitter occurs or increases. At a temperature equal to or higher than the second temperature, the diffusion of debris that may be present on the flow splitter 22 may increase. For example, the diffusion coefficient of tin vapor in a hydrogen atmosphere may increase with an increase in temperature. By maintaining the temperature of the flow splitter 22 below the second temperature, the diffusion of debris in the chamber 23 can be suppressed. The amount of debris that may be present on the flow splitter 22 is considered to be small, as described above, for example, because the flow splitter 22 is disposed in the chamber 23 and directs the first gas flow 16 around the flow splitter 22, and / or because a flow rate of the first gas flow 16 greater than 7 slm is used.

[0108] [000145] The heating element 24 may be embedded within the flow splitter 22. In other embodiments, it will be understood that the heating element may be provided separately. In such embodiments, the heating element may be arranged to raise the temperature of the flow splitter. The heating element 24 may be provided in the form of a resistive heating element. In other embodiments, it will be understood that the flow splitter 22 may be inductively heated and / or the heating element may be provided in the form of an electromagnetic element, such as a coil. An electronic oscillator, such as a high-frequency generator, may be provided to generate a current in the electromagnetic element, and as a result, heat may be generated in the electromagnetic element.

[0109] [000146] Referring to FIGS. 4A and 4D, in some embodiments, the flow splitter 22 may be configured to be cooled by a coolant. For example, the flow splitter 22 may be cooled to reduce a heat load that may act on the flow splitter 22, for example, due to radiation in the intermediate focus region 6. The flow splitter 22 may be cooled to maintain the temperature of the flow splitter 22 below the melting temperature of the fuel used to generate the plasma 7. Thereby, dispersion / diffusion onto the inner wall 21 of the radiation source SO of the liquid fuel that may be present on the flow splitter 22 or any other component can be prevented. As described above, the amount of debris that may be present on the flow splitter 22 is, as described above, for example, because the flow splitter 22 is disposed in the chamber 23 and directs the first gas flow 16 around the flow splitter 22, and / or because a flow rate of the first gas flow 16 greater than 7 slm is used, considered to be small.

[0110] [000147] The coolant may be supplied by a coolant source 25. For example, the flow splitter 22 may include channels 26 for receiving the coolant from the coolant source 25 and / or for flowing the coolant through the flow splitter 22. The flow splitter 22 may be configured to connect to the coolant source 25. The coolant source 25 may be configured to supply the coolant to the flow splitter 22. For example, the coolant source 25 may be configured to supply the coolant to the flow splitter 22 to reduce the temperature of the flow splitter 22 below, for example, the melting temperature of the fuel used to generate the plasma 7 and / or a second temperature, as described above. The coolant may be provided in the form of a coolant fluid, such as a coolant liquid or a coolant / cooling gas. It will be understood that the flow splitter may be configured to be cooled by a coolant instead of or in addition to comprising the heating element 24.

[0111] [000148] FIG. 5 schematically shows another embodiment of the radiation source SO. The radiation source SO shown in FIG. 5 is the same as that shown in FIG. 4A. For clarity, the first and second gas supply systems 17, 20, one or more openings 18, the laser 1, the laser beam 2, and the radiation beam B are omitted in FIG. 5. However, it will be understood that the exemplary radiation source SO shown in FIG. 5 may have the features of the radiation source SO described above in connection with FIGS. 1 to 4.

[0112] [000149] The exemplary flow splitter 22 of the radiation source SO shown in FIG. 5 comprises a plurality of other openings 27 which may be provided in the form of nozzles or slits. The plurality of other openings 27 (or each separate opening of the plurality of other openings 27) may be configured to direct a third gas flow 28 towards the collector 5. The third gas flow may have a flow rate in the range of about 1 to 50 slm. The plurality of other openings 27 may be arranged in the flow splitter 22 such that the third gas flow 28 from the plurality of other openings 27 interacts with the first gas flow 16. The interaction between the first gas flow 16 and the third gas flow 28 can direct or push the first gas flow 16 near the inner wall 21 of the chamber 23, for example the conical part 23a. By providing the plurality of other openings 27 to direct the third gas flow 28 towards the collector 5, the dispersion of the first gas flow 16 can be increased. As a result of the increased dispersion of the first gas flow 16, the interaction between the first and second gas flows 16, 19 may be reduced or suppressed.

[0113] [000150] The plurality of other openings 27 may be arranged circumferentially, circumferentially and / or axially in the flow splitter 22. In other words, the plurality of other openings 27 may be arranged to extend around the flow splitter 22 and / or in the direction of the central axis, i.e. the longitudinal axis A, of the flow splitter 22. The plurality of other openings 27 may be arranged symmetrically in the flow splitter 22, for example such that the first gas flow 16 and / or the third gas flow 28 flow symmetrically around the flow splitter 22.

[0114] [000151] The exemplary first gas supply system 17 shown in FIG. 2 may be configured to supply a third gas stream 28 to the flow splitter 22. For example, the flow splitter 22 may be connected or connectable to the first gas supply system 17 to enable supply of the third gas stream 28 to the flow splitter 22. In another example, it will be understood that the debris mitigation system may include another gas supply system configured to supply a third gas stream to the flow splitter. The flow splitter may be connected or connectable to another gas supply system to enable supply of the third gas stream to the flow splitter. The flow splitter 22 shown in FIG. 5 includes a plurality of other openings 27, but in other embodiments, it will be understood that the flow splitter may include one other opening configured to direct the third gas stream to a collector.

[0115] [000152] FIG. 6 schematically shows another embodiment of the radiation source SO. The radiation source SO shown in FIG. 6 is the same as that shown in FIG. 4A. For clarity, the first and second gas supply systems 17, 20, one or more openings 18, the laser 1, the laser beam 2, and the radiation beam B are omitted in FIG. 4A. However, it will be understood that the exemplary radiation source SO shown in FIG. 6 may have the features of the radiation source described above in connection with FIGS. 1 to 5.

[0116] [000153] The exemplary radiation source SO shown in FIG. 6 comprises a debris receiving surface 29a that may be part of or provided by a bar, i.e., an obscuration bar 29. The bar 29 is disposed within the chamber 23, such as the conical portion 23a, and can prevent debris from reaching the intermediate focus region 6. The bar 29 may be disposed so as to intersect or extend across the optical axis OA of the collector 5. In this arrangement, the bar 29 can be considered to block the direct line of sight of debris that may contain ballistic particulate debris and / or a portion of the laser beam 2, such as the portion passing through the plasma formation region 4 of the laser beam 2. In other words, the bar 29 may be configured to reflect a portion of the laser beam 2 away from the intermediate focus region 6 of the radiation source SO.

[0117] [000154] In the exemplary radiation source shown in FIG. 6, the flow splitter 22 is disposed between the bar 29 and the intermediate focus region 6. In this arrangement, the bar 29 is disposed so as to extend over or overlap at least a portion or all of the flow splitter 22. For example, the bar 29 may be disposed so as to extend over or overlap an enlarged portion of the first end 22a of the flow splitter 22 such that debris generated by the plasma 7 impinges on the debris receiving surface 29a of the bar 29. In other words, the flow splitter 22 may be disposed in the shadow of the bar 29.

[0118] [000155] In the exemplary radiation source SO shown in FIG. 6, the debris receiving surface 29a was described as being part of the bar 29. However, in other embodiments of the radiation source described in connection with FIGS. 4A, 4B, 4C, and 5, it will be understood that the debris receiving surface 29a may be provided by or be part of the flow splitter 22. In such embodiments, the flow splitter 22 may include any of the features of the bar 29 described herein. Further, the flow splitter 22 may be configured to withstand the heat or heat load generated by the plasma 7 or the heat or heat load of the radiation in the intermediate focus region 6. The flow splitter 22 may be configured to reflect a portion of the laser beam 2 passing through the plasma formation region 4 in a direction away from the intermediate focus region 6. For example, if the debris receiving surface 29a is provided by the flow splitter 22, the length or dimension of the flow splitter 22 in a direction perpendicular and / or parallel to the central axis, i.e., the longitudinal axis A, of the flow splitter 22 may be larger than the length or dimension of the flow splitter 22 in a direction perpendicular and / or parallel to the central axis, i.e., the longitudinal axis A, of the flow splitter 22 used in combination with the bar 29, for example.

[0119] [000156] FIG. 7A shows a simulation of the first gas flow 16 in the radiation source SO in the absence of a flow splitter. The radiation source SO shown in FIG. 7A includes the chamber 23, for example, an obscuration bar 29 disposed in the conical portion 23a, as described above with respect to FIG. 6. The first gas flow 16 may be considered to be substantially laminar in the radiation source SO. However, it can be seen from FIG. 7A that a portion of the first gas flow 16 recirculates. The recirculation of a portion of the first gas flow 16 may be due to the interaction with the adjacent gas, for example, a jet that can pull the adjacent gas at the same speed or velocity is formed from a portion of the gas of the first gas flow 16. The fresh gas of the first gas flow 16 flows along the inner wall 21 at a low speed or velocity, which can prevent gas depletion and the formation of negative pressure. As a result of a portion of the first gas flow 16 recirculating, debris may accumulate on the inner wall 21 of the radiation source SO, for example, the chamber 23.

[0120] [000157] FIG. 7B shows a simulation of surface deposition of debris, such as atomic tin debris, in a radiation source in the absence of a flow splitter. It can be seen that the debris is distributed in the chamber 23, for example, the conical portion 23a, and extends in a direction towards the intermediate focus region 6.

[0121] [000158] FIG. 8A shows a simulation of the first gas flow 16 in the radiation source SO provided with the flow splitter 22 described above. From FIG. 8B, it can be seen that by disposing the flow splitter 22 within the chamber 23, for example, the conical portion 23a, the recirculation of the first gas flow 16 is suppressed. As a result, as shown in FIG. 8B showing a simulation of surface deposition of debris, such as atomic tin debris, in a radiation source provided with the flow splitter 22, the debris deposition within the chamber 23, for example, the conical portion 23a, is suppressed. In other words, by disposing the flow splitter 22 within the chamber 23, for example, the conical portion 23a, the spread of debris in the direction of the intermediate focus region 6 is suppressed.

[0122] [000159] The first, second, and / or third gas flow may include hydrogen gas. In other embodiments, it will be understood that another gas or a mixture of gases may be used. For example, in other embodiments, the first, second, and / or third gas flow may include argon gas or helium gas.

[0123] [000160] The material of the flow splitter 22 may be selected to exhibit resistance to corrosion, for example, resistance to corrosion by fuel in an environment within the radiation source SO, such as a hydrogen environment within the radiation source SO. The material of the flow splitter 22 may be selected to exhibit resistance to the thermal load acting on the flow splitter due to, for example, radiation in the radiation source SO, the plasma 7, and / or the increase in the temperature of the flow splitter 22 to a temperature equal to or higher than the first temperature, as described above. Exemplary flow splitters 22 may include or be made of a metal or a metal alloy. For example, the material of the flow splitter may be or may include molybdenum, tungsten, aluminum, stainless steel, copper, or alloys thereof. The flow splitter 22 may have a metal surface or a metal alloy surface. The metal surface or the metal alloy surface of the flow splitter may result in an improvement in the recombination of hydrogen radicals that may be present within the radiation source SO. For example, hydrogen (H2) molecules may be split into hydrogen radicals by heat absorption and / or radiation absorption, or ion collisions. Hydrogen radicals may be useful for removing debris, such as tin, from the inner wall 21 of the radiation source. The presence of hydrogen radicals may cause contamination within the chamber 23, such as spitting of the fuel when the hydrogen radicals diffuse into the liquid fuel layer within the chamber 23. By providing a flow splitter having a metal surface or a metal alloy surface, the recombination of hydrogen radicals can be improved and / or contamination within the chamber 23, such as spitting of the fuel, can be suppressed. In other embodiments, it will be understood that the flow splitter may include another material, such as a ceramic material. The ceramic material may include a silicon dioxide material, a zirconium nitride material, or a zirconium oxide material.

[0124] [000161] As described above, the debris mitigation system is configured to direct a first gas flow from the intermediate focus region towards the plasma formation region. For example, the debris mitigation system may comprise a first gas supply system. The first gas supply system may be configured to supply the first gas flow towards the plasma formation region. The first gas supply system may comprise one or more openings, such as one or more nozzles or slits, provided in the intermediate focus region, for example at or near the intermediate focus. The one or more openings may be arranged such that the first gas flows towards the collector. For example, the one or more openings may be arranged to direct the first gas flow in a direction opposite (e.g., substantially opposite) to the propagation direction of the EUV radiation beam. The first gas flow may have a flow rate sufficient to suppress or prevent debris from moving towards the intermediate focus 127a. The first gas supply system can be considered to be or included in a dynamic gas lock (DGL) system.

[0125] [000162] As shown in Figure 22A, to protect at least a part of the EUV lithography apparatus from fuel contamination by the EUV source, a first gas flow is introduced in the intermediate focus (IF) region 127 to push back the debris particles generated in plasma formation to the source container (the first gas flow shown in Figure 22A is the same as the first gas flow 16 in Figure 7A). The first gas flow is referred to herein as a dynamic gas flow or a dynamic gas lock (DGL) flow and can be generated by one or more converging gas inlets. For example, high-speed gas jets may be provided from two arrays of several gas inlets that converge towards the optical axis of the EUV collector (as shown in Figures 9 and 10 for example), and a high-speed first gas flow is formed within the EUV container 100. The high-speed first gas flow creates a drag force that pulls the debris particles away from the IF region 127, and at the same time, provides a Peclet-type protection to at least a part of the lithography apparatus from fuel vapor and / or derivatives of the fuel (such as tin hydride). However, experimental results show that when using a dynamic gas flow (such as the first gas flow) with a gas flow rate of less than 10 slm, the amount of debris particles passing through the IF point 127a may be one order of magnitude greater than the cleanliness specification required for the EUV source.

[0126] [000163] To solve this problem, it is conceivable to use a faster first gas flow to protect at least a part of the lithography apparatus from fuel contamination. However, when the first gas flow becomes faster, the collector contamination and the stability of the fuel droplets (when released by the fuel generator) may deteriorate. The high-speed and narrow dynamic gas flow is still expected to reach the collector by interacting with the cone flow of the collector provided from the opposite direction, resulting in instability of the fuel droplets and / or further collector contamination. The high-speed first gas flow causes recirculation and further brings the debris particles closer to the IF region 127, as a result, the debris particles may enter the lithography apparatus through the intermediate focus 127a, thereby at least partially canceling the debris reduction function of the dynamic (first) gas flow. Gas recirculation may occur especially at the upper part of the container, thereby serving as a "conveyor belt" for debris towards the IF region 127.

[0127] [000164] In one embodiment, it is proposed to use a second gas supply system arranged to provide a second gas flow that confines the recirculation of the first gas flow to an intermediate focal region 127 in the upper part of the EUV vessel 100. The second gas supply system preferably comprises one or more openings arranged to direct the second gas flow in a direction substantially perpendicular to the propagation direction of the first gas flow (i.e., substantially perpendicular to the optical axis of the EUV collector). In the embodiment shown in FIG. 22B, a pair of inlets 624a, 624b for providing two opposing gas flow jets (i.e., the second gas flow) are arranged near the intermediate focal region 127 downstream of the first gas flow. The second gas flow is preferably supplied at a gas flow rate of at least 2 slm per inlet (i.e., at least 4 slm per pair), more preferably at least 5 slm per jet. The second gas flow may have a speed substantially the same as or even higher than the first gas flow.

[0128] [000165] The aperture jet cooperates best with a straight DGL flow (i.e., in line with the optical axis of the EUV vessel). The gas jet inlets 624a, 624b may be aligned to provide a central flow (as shown in FIG. 22B). The gas jet inlets may also be slightly offset. The offset between the aperture jets can improve robustness against tilts (which form a larger interaction region when the gas flow is blocked) as long as the DGL flow remains substantially straight. Alternatively, the gas jet inlets 624a, 624b are arranged to provide an inclined second gas flow (not shown) at an angle to the direction of the first gas flow.

[0129] [000166] If there are no mechanical design constraints, a pair of opposing gas jet inlets 624a, 624b may be arranged in the IF region 127 close to the first gas inlet at the IF point 127a (as shown in FIG. 22C) to improve performance. The function of the pair of opposing gas jets 624a, 624b is to throttle and diffuse the dynamic gas flow by momentum exchange. A similar principle is used in a liquid atomizer where two high-speed side gas jets break up the liquid flow into fine droplets. The side gas jets 624a, 624b decelerate and diffuse the thin, high-speed dynamic gas flow jets. This removes or suppresses large-scale recirculation near the container wall, and instead, a substantially unidirectional gas flow field is established towards the discharge section, which helps protect the EUV container 100 from fuel contamination.

[0130] [000167] The throttle jet inlets 624a, 624b are arranged such that the gas jet flow is substantially orthogonal to the main direction of the dynamic gas flow, while the dynamic gas flow nozzle is arranged substantially in alignment with the resulting dynamic gas flow jet. The speed of the throttle jets may be adjusted to be substantially the same as the speed of the dynamic gas flow jets near the break point 166. Without being bound by theory, it is expected that the momentum of the throttle jets preferably has a value substantially equivalent to the momentum of the dynamic gas flow jets at the break point 166. The debris reduction of the EUV container 100 can be enhanced by varying the sizes, shapes (circular, racetrack, square, etc.) of the inlets and nozzles, and the spacing from the throttle jet inlets 624a, 624b to the IF point 127a.

[0131] [000168] One or more advantages of introducing side jets are enabling a high DGL flow rate for protecting at least a part of the lithographic apparatus, suppressing and even removing recirculation from the discharge section to the lower cone, enabling active peclet protection in the IF cone, and being able to significantly reduce the dynamic gas flow speed without sacrificing the function of the dynamic gas flow, thereby removing the adverse effects on the stability of the collector and fuel droplets.

[0132] [000169] Figures 22B and 22C show a pair of throttle jets, but it is also possible to use a single throttle jet or multiple throttle jets (i.e., two or more throttle jets). Simulations have shown that two throttle jets or multiple pairs of gas flow throttle jets produce advantageous results, but depending on the specific conditions of the total gas flow within the EUV vessel, an asymmetric second gas flow configuration may also be useful. In an asymmetric flow design, the momentum of the throttle jet is substantially equal to the momentum of the dynamic gas flow at the break point.

[0133] [000170] According to an aspect of the present invention, it is also possible to combine the above embodiments with other gas flow supply parts. For example, the EUV vessel may also include (i.e., in addition to the first and second gas flows) a third gas flow in the form of a shower head disposed along at least a portion of the inner wall of the vessel. The shower head includes one or more nozzles configured to introduce gas into the vessel. The shower head has at least one inlet configured to supply gas into the shower head. One or more discharge parts may be configured to remove the gas introduced into the vessel, and the one or more discharge parts are oriented along at least a portion of the inner wall of the vessel so as to flow the gas in a direction away from the EUV collector. At least one discharge part may be disposed at an azimuthally asymmetric position along the inner wall of the vessel and configured to discharge gas from the vessel. The throttle jet or the induction device can also operate well with a curtain flow (e.g., the curtain flow 122 as shown in FIG. 18A). It is also possible to combine a second gas flow (throttle jet), a curtain flow, and a shower head flow at the bottom of the EUV vessel with the DGL flow. Another embodiment is a curtain flow substantially perpendicular to the first gas flow provided by an induction device (e.g., as shown in FIG. 20). This can be used in combination with a throttle jet or alone (without a jet).

[0134] [000171] Further, a guiding device may be added into the EUV chamber such that the first gas flow is directed peripherally. The guiding device may be introduced into the flow path of the first gas flow before or after the break point by the second gas flow.

[0135] [000172] The radiation source used in the lithography system may be provided in the form of a laser-produced plasma (LPP) source (or simply "source"). The radiation source generates extreme ultraviolet (EUV) radiation by generating a plasma from a fuel such as tin (Sn) in a plasma container. The radiation source may include an EUV container. In some examples, a tin plasma is generated by illuminating droplets of a liquid fuel with high-energy laser radiation. The following description refers to tin, but any suitable fuel may be used. EUV photons emitted from the plasma are collected by a near-normal incidence radiation collector (which may also be more generally referred to as a normal incidence radiation collector) provided in the form of an EUV collector within the container and sent to an intermediate focus that enters at least a part of the lithography apparatus. In many examples, tin debris is generated as a result of illuminating the tin material with laser radiation and remains within the container.

[0136] [000173] The tin debris may include tin material or tin products remaining within the container after illumination by the laser radiation has been performed or was intended. The tin debris can include, for example, ionic tin, tin vapor, tin particles, tin products (SnH4 gas), or tin deposits. In many examples, the tin debris deposits not only on the EUV collector but also on the inner wall of the container of the EUV container. Once deposited, the tin debris can spit, drip, and fall onto other surfaces within the container. As a result, the tin debris can accumulate to such an extent as to reduce the reflectivity of the EUV collector or block the EUV optical path. Ultimately, this shortens the life of the collector and reduces the availability of the radiation source.

[0137] [000174] In some examples, some surfaces (such as the container wall, the blade, and the scrubber) are kept cold during the operation of the radiation source. This can eliminate some of the tin dripping and ejection by keeping the tin debris in a solid state. However, in certain situations, tin may still accumulate to such an extent that it falls due to gravity and the gas pressure applied to the EUV collector during the operation of the EUV container. Furthermore, the accumulation of Sn on these cold surfaces can cause not only disturbances in the gas flow for the radiation source operation but also blockage of the EUV path.

[0138] [000175] In other examples, some surfaces are kept at a temperature higher than the melting point of Sn. As a result, the tin debris is maintained in a liquid state, which can suppress the accumulation of Sn and the blockage of the EUV path. However, as described above, the liquid tin is prone to ejection and dripping.

[0139] [000176] Some radiation sources address the Sn debris and deposits on the container surface by providing gas supply parts at multiple locations within the container to expel the tin debris from the container. One of these is a central supply part near the center of the EUV collector that introduces gas into the container. Also, some radiation sources may have a peripheral supply part located in a place near the periphery of the EUV collector that introduces gas into the container. The central supply part and the peripheral supply part provide gas flow paths that help protect the EUV collector from Sn debris to some extent by giving a barrier to the diffusion of Sn debris as well as having an energetically favorable flow direction away from the EUV collector.

[0140] [000177] Embodiments having a central supply section and a peripheral supply section enable a certain level of protection of the EUV collector, but Sn debris may still accumulate on the inner wall of the container to an extent that blocks the EUV optical path. Also, when Sn debris accumulates in a region above the EUV collector on the inner wall of the container in the direction of gravity, the Sn debris may fall onto the EUV collector. As a result, in addition to the central supply section and the peripheral supply section, it is considered advantageous to provide a gas source for introducing gas into the container to enable protection of one or more inner walls of the container.

[0141] [000178] In certain embodiments, the EUV container may comprise a container wall supply section for introducing gas into the container. According to some embodiments, the container wall supply section may comprise a showerhead disposed along at least a portion of the inner wall of the container and having a plurality of nozzles for introducing gas into the container. According to these embodiments, the showerhead may have a shape similar to that of the inner wall of the container. Thus, for example, if the inner wall of the container has a conical shape, the showerhead may also have a conical shape. Similarly, if the inner wall of the container happens to have a cylindrical shape, a rectangular shape, or other polyhedral shapes, the showerhead included in the EUV container may similarly have a cylindrical shape, a rectangular shape, or other polyhedral shapes, respectively. According to another embodiment, the showerhead may have a shape different from that of the inner wall of the container. In some embodiments, the gas supplied into the container via the container wall supply section, the peripheral supply section, or the central supply section may include hydrogen gas.

[0142] [000179] FIG. 9A is a simplified schematic view of an embodiment of an EUV container 100 having a showerhead 101 disposed along at least a portion of the inner wall 104 of the EUV container 100. According to this embodiment, it is shown that a laser radiation pulse 105 illuminates a target material 111 within a material target region (not shown). It is shown that a plasma 107 may be generated and, for example, EUV radiation 115 may be produced. It is shown that the EUV radiation 115 is reflected by an EUV collector 102 towards an intermediate focus (IF) region 157.

[0143] [000180] According to the embodiment of FIG. 9A, the showerhead 101 is shown to include a plurality of nozzles 120 disposed along at least a portion of the inner wall 104 of the container. Each of the plurality of nozzles 120 is shown to allow the inflow of the gas stream 140 into the container in a direction away from the disposed inner wall 104 of the container. Although not shown, it should be understood that the nozzle 120 may also be included in the rightmost portion of the inner wall 104 of the container. That is, the showerhead 101 may extend along the right side of the inner wall 104 of the container, including a portion close to the IF region 157 of the inner wall 104.

[0144] [000181] FIG. 9A shows that the inner wall 104 of the container can be defined by a rectangular cross-section 151. The inner wall 104 of the container may be, for example, circular, elliptical, other cross-sectional shapes that may be non-rectangular polygons, or may have different cross-sectional shapes at different distances along the length of the inner wall 104 of the container. It should be understood that various shapes of the inner wall 104 of the container can be realized without departing from the scope and spirit of the embodiments described herein. Therefore, various non-limiting examples of a conical inner wall 104 of the container are described below by way of example.

[0145] [000182] FIG. 9B is a simplified schematic diagram of an embodiment of an EUV container 100 (or simply "container") having a showerhead 101 for introducing gas into the container 100 via a plurality of first and second nozzles 120a and 120b. In the illustrated embodiment, the EUV container 100 is shown to comprise a container inner wall 104 having a conical shape. The showerhead 101 is shown to take on a similar shape as a result of being disposed along at least a portion of the container inner wall 104. The EUV container 100 is further shown to be able to receive a laser radiation pulse 105 entering the container through a central region 109. The laser radiation pulse 105 is shown to be incident on a target material 111 within a target material region (not shown). A plasma 107 is shown to be generated and emit plasma light 113. A portion of the plasma light including EUV radiation 115 is shown to be reflected by the EUV collector 102, travel within the container 100, and enter at least a portion of a lithographic apparatus 117.

[0146] [000183] FIG. 9B also shows a central supply section 106 and a peripheral supply section 108 both for introducing gas into the container 100 in the vicinity of the EUV collector 102. The central supply section 106 and the peripheral supply section 108 may both comprise a plurality of gas inlets for introducing gas into the container 100 respectively. The central supply section 106 and the peripheral supply section 108 introduce gas so as to reduce the contact cases of Sn debris with the EUV collector 102. For example, the central supply section 106 and the peripheral supply section 108 provide a diffusion barrier against Sn vapor or particles and, similarly, an energetically favorable flow path in a direction away from the EUV collector 102. As a result, a certain degree of protection for the EUV collector 102 against Sn debris is provided.

[0147] [000184] Figure 9B also shows a showerhead 101 for introducing gas into the container 100 in a direction away from the inner wall 104 of the container. In the illustrated embodiment, the showerhead 101 includes a first supply section 103a and a second supply section 103b. The first supply section 103a is shown to supply a first plurality of nozzles 120a for introducing gas into the container 100 as a first plurality of flows 140a. The second supply section 103b is shown to supply a second plurality of nozzles 120b for introducing gas into the container 100 as a second plurality of flows 140b. It is shown that the first supply section 103a and the second supply section 103b of the showerhead 101 can control the supply of gas to the first plurality of nozzles 120a and the second plurality of nozzles 120b separately. Also, the second plurality of nozzles 120b are shown to be closer to the EUV collector 102, while the first plurality of nozzles 120a are shown to be closer to the IF region 157 of the container near at least a part of the lithography apparatus 117.

[0148] [000185] In certain embodiments, the first plurality of nozzles 120a and the second plurality of nozzles 120b may be separately supplied by a separately controlled gas supply system (not shown). In these embodiments, having a separately controlled gas supply system for the first plurality of nozzles 120a and the second plurality of nozzles 120b may enable control of the flow pattern or flow path that occurs within the container 100 due to the introduction of gas into the container 100 via the showerhead 101. Details regarding controlling the flow pattern within the container 100 are discussed herein. In certain embodiments, the first plurality of nozzles 120a and the second plurality of nozzles 120b may be considered as separate zones for introducing gas into the container 100.

[0149] [000186] The first plurality of flows 140a and the second plurality of flows 140b are shown to be in a direction away from the inner wall 104 of the container. As a result of the directionality of the first and second pluralities of flows 140a and 140b, a flow pattern can be generated within the container 100 that prevents the deposition of Sn debris on the surface of the inner wall 104 of the container. For example, the gas introduced through the first and second pluralities of nozzles 120a and 120b can provide a diffusion barrier that can suppress the Sn vapor flux, the SnH4 flux, and other Sn debris fluxes on the inner wall 104 of the container.

[0150] [000187] In certain embodiments, a hydrogen radical flux may be present on the inner wall 104 of the container. Generally speaking, hydrogen radicals can be present within the container 100 as a result of the plasma 107, as well as from the absorption of EUV radiation 115 by hydrogen gas. Hydrogen radicals can be advantageous in certain situations, including those involving a "cold" wall (a portion of the inner wall 104 of the container that is regulated to be below the melting point of Sn) that can remove solid Sn deposits from the inner wall 104 of the container, for example, by forming SnH4 gas. According to certain embodiments under such circumstances, additional hydrogen radicals can be supplied, for example, by supplying hydrogen radicals from the showerhead 101, the central supply unit 106, the peripheral supply unit 108, or the dynamic gas lock (DGL) supply unit 110, to facilitate the removal of solid Sn deposits from the inner wall 104 of the container. In other embodiments that include a warm region that can contain liquid Sn on the inner wall 104 of the container, the hydrogen radical flux over the warm region can be reduced.

[0151] [000188] In various embodiments, the inner wall 104 of the container may be defined by an independent wall interface that enables the first and second pluralities of nozzles 120a and 120b to direct a gas flow into the EUV container 100. In these configurations, the showerhead 101 is mainly behind the inner wall 104 of the container. In other embodiments, the showerhead 101 itself has an inner surface that defines the inner wall 104. In certain other embodiments, each of the first and second pluralities of nozzles 120a and 120b may include an individual gas line for introducing gas into the container 100. In yet another embodiment, the showerhead 101 may be incorporated into the inner wall 104, and the lines supplying each of the nozzles of the first and second pluralities of nozzles 120a and 120b are a first piece that is later fitted to a second piece, with either the first or the second piece being hogged out from a first piece that defines the inner wall 104 of the container.

[0152] [000189] Although the first and second pluralities of flows 140a and 140b are shown introducing gas in a direction orthogonal to the inner wall 104 of the container, it should be understood that there are many ways to introduce gas into the container 100 that are within the spirit and scope of the embodiments even if not orthogonal to the inner wall 104. Further, although each of the first and second pluralities of nozzles 120a and 120b is shown having the same directionality, there can be various variations to the individual directionality of the individual nozzles that can be realized without departing from the essence and scope of the described embodiments. For example, some embodiments may implement a plurality of nozzles having the same direction or angle with respect to the inner wall 104, while other embodiments may implement nozzles having different angles with respect to the inner wall 104 that meet the needs of different embodiments of the EUV source or the EUV container.

[0153] [000190] It should also be understood that the showerhead 101 of FIG. 9B may be configured such that the plurality of first and second nozzles 120a and 120b introduce gas into the container 100 along the entire circumference of the inner wall 104 of the container, and thus extends along the periphery (e.g., circumference) of the inner wall 104 of the container. In other embodiments, the showerhead 101 may not necessarily extend along the entire circumference of the inner wall 104 of the container, i.e., it may only extend in a lateral length along the inner wall 104 of the container. In other words, the embodiment may have any one of a plurality of patterns for distributing the plurality of first and second nozzles 120a and 120b along the inner wall 104 of the container 100 to meet the needs of different embodiments. For example, in a particular embodiment, the plurality of first or second nozzles 120a or 120b may be arranged in a region above the EUV collector 102 in the gravitational direction, so that Sn debris accumulates on the container wall in this region and then does not fall onto the EUV collector 102 during the operation of the EUV source.

[0154] [000191] Although the inner wall 104 of the container is shown to have a smooth surface, it should be understood that the inner wall 104 of the container may have a finned surface (e.g., a surface with fins or a surface defined by fins). For example, in a particular embodiment having one or more inner walls 104 with fins, gas may be introduced through the rear of the fins and discharged into the container 100 through the openings in the plasma-facing surface of the fins. Thus, an appropriate channel (not shown) inside the fins may be used to supply gas to the nozzles incorporated in the fins in a desired pattern. As a result, the showerhead 101 may be incorporated into the finned surface of the container 100 to obtain a gas flow pattern that reduces the contamination of one or more inner walls 104 of the container. In other embodiments having one or more inner walls 104 with fins, gas may be introduced from the valleys between adjacent fins.

[0155] [000192] Figure 9B also shows a symmetric discharge portion 112 for discharging gas from the container 100. The symmetric discharge portion 112 may be arranged symmetrically or asymmetrically around the perimeter of the inner wall of the container. In one embodiment, the symmetric discharge portion 112 may include one discharge portion extending around the entire perimeter of the inner wall 104 of the container. In another embodiment, the symmetric discharge portion 112 may include a plurality of individual discharge lines arranged symmetrically around the inner wall 104 of the container. Figure 9B further shows a dynamic gas lock (DGL) supply portion 110 for introducing gas into the container from a location near the IF region 157.

[0156] [000193] Figure 9C is a simplified schematic diagram of an embodiment of an EUV container 100 having a showerhead 101 with a plurality of nozzles 120 supplied by a gas supply portion 103. The gas supply portion 103 may be controlled by a common gas supply system (not shown). In the embodiment shown, it is shown that the plurality of nozzles 120 can introduce gas into the container 100 in a direction in which a plurality of gas flows 140 move away from the inner wall 104 of the container. Figure 9C shows not only the central supply portion 106, the peripheral supply portion 108, and the DGL supply portion 110, but also a laser radiation pulse 105 incident on the material target region 123.

[0157] [000194] In another embodiment shown in Figure 9D, the showerhead 101 is shown to include a plurality of separately supplied nozzles 120a - 120n. It is shown that the first plurality of nozzles 120a are supplied by a first supply portion 103a and introduce gas into the container 100 as a first plurality of gas flows 140a. It is understood that the first plurality of nozzles 120 extend along the perimeter of the inner wall 104 of the container according to some embodiments.

[0158] [000195] The second plurality of nozzles 120b and the third plurality of nozzles 120c are shown to be configured to be present along the same lateral distance on the inner wall 104 of the container with respect to the IF region 157. However, the second and third pluralities of nozzles 120b and 120c are shown to have different circumferential and / or azimuthal positions along the inner wall 104 of the container. Further, the second plurality of nozzles 120b are shown to be supplied by the second supply unit 103b, while the third plurality of nozzles 120c are shown to be supplied by the third supply unit 103c. As a result, the second and third pluralities of nozzles 120b and 120c may enable control of the flow pattern of the gas within the container 100.

[0159] [000196] According to some embodiments, each of the plurality of nozzles 120a - 120n may be supplied by a separately controlled gas supply system (not shown). As a result, precise control of the flow pattern within the container 100 can be achieved through individual control of the plurality of nozzles 120a - 120n. The second, third, and nth pluralities of nozzles 120b, 120c, and 120n are shown to enable the second, third, and nth flows 140b, 140c, and 140n, respectively. Each of the flows 140a - 140n is shown to be generally in a direction away from the inner wall 140 into which the flows 140a - 140n are introduced.

[0160] [000197] By way of example and not limitation, a gas flow in the range of 50 - 500 slm may be used for supply to the supply unit 103 to enable protection of the inner wall 104 of the container. In embodiments having two or more supply units, such as the embodiment shown in FIG. 9D, the flow in the above range may be distributed among the supply units 103a - 103n. In one embodiment, the supply unit 103 may be supplied with about 200 slm of gas. Of course, other ranges of mass flow rates may be used to introduce gas into the container 100 to suit the needs of various embodiments, and the given examples are not intended to be limiting.

[0161] [000198] As already discussed, protecting the inner wall 104 of the container or other exposed surfaces of the shower head 101 includes providing a gas flow pattern within the container to suppress the Sn vapor flux, SnH4 vapor flux, and other Sn debris fluxes on one or more of the inner walls 104 of the container. As an example, according to some embodiments, as a result of the flow patterns generated by the central supply section 106, the peripheral supply section 108, and the shower head 101 respectively, the Sn vapor and SnH4 debris on the inner wall 104 of the container can be reduced by hundreds of times. In other embodiments, further reduction of the Sn debris flux can be achieved, for example, by using an asymmetric vane / liner structure that does not pump in the area above the EUV collector 102.

[0162] [000199] According to some embodiments, a range of 10 to 1000 nozzles having a diameter of about 1 to 10 mm may be used. According to certain embodiments, depending on the number and size of the nozzles, each of the nozzles may be spaced about 1 to 10 cm apart. A gas supply section (not shown) and a shower head body or manifold or a plurality of gas lines (not shown) that provide a uniform and stable mass flux through the plurality of nozzles may be used in the above embodiments. Of course, embodiments with more or fewer nozzles having different cross-sectional widths (e.g., diameters) and spacings may be used without departing from the scope and spirit of the present disclosure.

[0163] [000200] Also, according to some embodiments, the plurality of nozzles 120 may be joined to the inner wall 104 of the container such that the openings of the nozzles 120 are in the same plane as the plasma-facing surface of the inner wall 104 of the container. In other embodiments, the nozzles 120 project into the container 100 from the inner wall 104 of the container, for example, by several millimeters (not shown). The nozzles 120 projecting into the inner wall 104 of the container or the liner can provide some protection from clogging as a result of Sn debris during the operation of the radiation source or during periodic liquid outflow.

[0164] [000201] To ensure that the outflow area of the nozzle is not contaminated, certain embodiments may include a nozzle tip made of a ceramic (e.g., ZrN) material. In these and other embodiments, hydrogen radicals may be supplied near the nozzle opening and / or the nozzle tip for cleaning. Additionally, these embodiments may use EUV-induced self-cleaning. In these and other embodiments, the nozzle 120 may also include a hollow plug made of a different material disposed in a larger opening of the inner wall 104 of the container.

[0165] [000202] To prevent or inhibit Sn debris from entering the plurality of nozzles 120, certain embodiments may include nozzles 120 made of a porous medium. As a result, the outflow of gas may be less sensitive to particles deposited at the nozzle opening (not shown). In other embodiments, a mesh grid disposed near the nozzle opening may be provided for each nozzle to prevent Sn debris from entering the nozzle 120. In certain embodiments, the mesh grid may be heated for local generation of hydrogen radicals. In yet another embodiment, the nozzle 120 may include a showerhead hole with a cap for introducing gas laterally along the periphery of the inner wall 104 of the container. In these embodiments, a leakage flow may be introduced at the top of the cap to prevent Sn debris from depositing on the cap itself.

[0166] [000203] FIG. 10 is a simplified schematic view of an embodiment of an EUV vessel 100 having a first showerhead 101a, a second showerhead 101b, and an asymmetric discharge portion 132. The vessel inner wall 104 is shown to have a ceiling region 104a defined as a portion of the vessel inner wall 104 that is above the EUV collector 102 in the direction of gravity (i.e., the portion of the first showerhead 101a that defines each portion of the vessel inner wall 104). The ceiling region 104a is shown to include a boundary 134 that defines a portion of the vessel inner wall 104 that is above the EUV collector 102 in the direction of gravity and a portion that is not. It should be understood that the shape of the boundary 134 will depend on the shape of the vessel inner wall 104. The boundary 134 is illustrative and is not intended to be limiting. For example, the boundary 134 may be located closer to the IF region 157 or the EUV collector 102 depending on the shape of the vessel inner wall 104 and the orientation of the EUV vessel 100 while the EUV source is operating.

[0167] [000204] The asymmetric discharge portion 132 is shown to be generally oriented along the vessel inner wall 104 at a location generally opposite the ceiling region 104a to promote a flow pattern of gas that is away from the EUV collector 102 and away from the ceiling region 104a within the vessel 104. In a particular embodiment, the asymmetric discharge portion 132 may be configured in a downwardly inclined direction. It will of course be possible to implement many different orientations of the asymmetric discharge portion without departing from the spirit and scope of the embodiments. The configuration of the asymmetric discharge portion 132 shown in FIG. 10 is illustrative and is not intended to be limiting.

[0168] [000205] For example, the direction of the asymmetric discharge portion 132 may be at an upwardly inclined angle while maintaining the ability to promote a flow pattern within the vessel 100 that is away from the ceiling region 104a and away from the EUV collector 102. Further, in certain other embodiments, the asymmetric discharge portion 132 may be configured to be closer to or farther from the EUV collector 120 than the embodiment shown. Also, a scrubber remotely disposed downstream towards the pump may be included in certain embodiments (not shown) to avoid spitting within the vessel inner wall 104.

[0169] [000206] The first shower head 101a is shown to include a first plurality of nozzles 120a through which gas can be supplied further away from the second plurality of nozzles 120b of the shower head 101b. For example, while the first plurality of nozzles 120a are shown to be supplied by the first supply unit 103a, the second plurality of nozzles 102b are shown to be supplied by the second supply unit 103b. The first plurality of nozzles 120a are also shown to extend along the lateral length of the container inner wall 104 that is longer than that of the second plurality of nozzles 120b. However, in other embodiments, the reverse may also be the case. Further, the first plurality of nozzles 120a are shown to provide a first plurality of flows 140a that are greater in number than the second plurality of flows 140b provided by the second plurality of nozzles 120b. This may also be reversed in other embodiments. In certain other embodiments, the first and second pluralities of nozzles 120a and 120b may be supplied by a common gas supply unit.

[0170] [000207] Although not shown, the first plurality of nozzles 120a and the second plurality of nozzles 120b may extend a certain distance along the circumferential or outer peripheral direction along the container inner wall 104. In certain embodiments, the first plurality of nozzles 120a may extend further along the periphery than the second plurality of nozzles 120b, while in other embodiments, the second plurality of nozzles 120b may extend further along the periphery than the first plurality of nozzles 120a. In other embodiments, the first and second pluralities of nozzles 120a and 120b may extend along the periphery at a similar distance, or may extend more or less along a given periphery than the other depending on the lateral position of the first or second pluralities of nozzles 120a and 120b.

[0171] [000208] In certain embodiments, the first and second plurality of nozzles 120a and 120b may be supplied by a common gas supply system. In yet other embodiments, each of the nozzles of the first and second plurality of nozzles 120a and 120b may be individually supplied with gas and controlled to enable precise control of the flow pattern within the container 100.

[0172] [000209] Here again, while the container inner wall 104 of FIG. 10 generally has a conical shape, it should be understood that there are various shapes that the container inner wall 104 (or the showerhead 101 that defines at least a portion of the container inner wall 104) can have without departing from the scope and spirit of the embodiments. For example, certain embodiments may have a container inner wall with an elliptical, rectangular, or polygonal cross-section. Further, these and other embodiments may include combinations of different types of surfaces (e.g., smooth surfaces, or surfaces defined by vanes) corresponding to the container inner wall shapes of the aforementioned types of cross-sections. Additionally, the container inner wall may have a smooth surface, or a surface defined by vanes, or a combination of both. As a result, various shapes of the container inner wall 104 can be realized in accordance with embodiments having the configuration of the asymmetric discharge portion 132 and one or more showerheads 101.

[0173] [000210] FIG. 11 is a simplified schematic view of an embodiment of an EUV container 100 oriented at an angle 119 for operation. It is shown that a laser radiation pulse 105 from a radiation source enters a material target region 123 where EUV radiation 115 is generated. The virtual laser radiation path 105a shown in the figure is shown to be the optical path that the laser radiation pulse 105 can take with respect to the direction of gravity. As a non-limiting example, certain embodiments may have an EUV container 100 oriented such that the virtual laser radiation path 105a has an angle 119 between about 45° and about 80°, depending on the designed structure. However, it will be understood that the angle 119 can vary between 0° and 90° depending on the details of each application.

[0174] [000211] FIG. 11 also shows the inner wall 104 of the container connected to the EUV collector 102. The inner wall 104 of the container is shown to extend from the EUV collector 102 to the IF region 157, with the upper region 153 including the portion of the inner wall 104 proximal to the EUV collector 102 and the intermediate region 155 including the portion of the inner wall of the container disposed between the IF region 157 and the upper region 153. The outer wall 121 of the container is shown to surround the inner wall 104.

[0175] [000212] FIG. 12A is a cross-sectional view of an embodiment of an EUV container 100 showing a plurality of flow paths in which gas is introduced into the container 100 from different supply portions and discharged by a symmetric discharge portion 112 extending around the inner wall 104 of the container. In the embodiment shown, the EUV container 100 is shown to include a central supply portion 106, a peripheral supply portion 108, and a DGL supply portion 110. The central supply portion 106 introduces gas that follows a central supply flow path 114 that is shown to proceed symmetrically towards the discharge portion 112 around a material target region (not shown).

[0176] [000213] FIG. 12A also shows a peripheral supply portion 108 that introduces gas following a peripheral supply flow path 116 adjacent to the periphery of the EUV collector 102. The peripheral supply flow path 116 is shown to proceed inwardly generally towards the axis or center of the container 100 before proceeding towards the symmetric discharge portion 112. Some of the peripheral supply flow paths 116a are shown to take a more circuitous path within the container 100, for example increasing the contact cases with the inner wall 104 of the container. In particular, the peripheral supply flow path 116a is shown to return towards the peripheral supply portion 108 along a path close to the ceiling region 104a of the inner wall 104 of the container. This may increase the contact of Sn debris with the inner wall 104 of the container.

[0177] [000214] The third gas supply unit shown in FIG. 12A is the DGL supply unit 110 that introduces gas into the container from the area near the IF region 157. The gas introduced by the DGL supply unit 110 follows the DGL supply flow path 118. As shown in FIG. 12A, the DGL supply flow path 118 may follow a roundabout path including a loop flow path that is slightly laterally separated along the inner wall 104 of the container. As a result, the DGL supply flow path 118 may increase the contact cases or flow of Sn debris to the inner wall 104 of the container. For example, the gas supply units shown in FIG. 12A (for example, the central supply unit 106, the peripheral supply unit 108, and the DGL supply unit 110) introduce gas that can serve as a diffusion barrier for by-products generated by laser-generated plasma and a carrier medium. As a result, each representative flow path may always contain Sn debris. As a result, although the EUV collector 102 has been shown to be somewhat protected from Sn debris because the central supply unit 106 and the peripheral supply unit 108 have flow paths 114 and 116 in directions generally away from the EUV collector 102, the same may not be true for all regions of the inner wall 104 of the container.

[0178] [000215] FIG. 12B is a cross-sectional view of an embodiment of the EUV container 100 showing a plurality of flow paths 114, 116, 118, and 136 through which gas is introduced into the container from various supply units and discharged by the asymmetric discharge unit 132. The flow paths 114, 116, 118, and 136 are based on computational fluid dynamics (CFD) simulations that take into account plasma-gas interactions (PGI). This embodiment is shown to include a showerhead 101 having a plurality of nozzles 120. In the simulation shown in FIG. 12B, there are flows emitted from the plurality of nozzles 120 of the showerhead 101, but they are omitted in the figure for clarity.

[0179] [000216] As shown in FIG. 12B, the EUV vessel 100 includes a central supply section 106, a peripheral supply section 108, a curtain supply section 122, and a DGL supply section 110. FIG. 12B also shows an asymmetric discharge section 132 oriented along the vessel 100 at a location generally opposite to the ceiling region 104a above the EUV collector 102 of the vessel inner wall 104 in the gravitational direction. Generally, the asymmetric discharge section 132 is shown to discharge the gas introduced through various supply sections in a direction away from both the EUV collector 102 and the ceiling region 104a of the vessel inner wall 104.

[0180] [000217] For example, each of the central supply flow path 114 and the peripheral supply flow path 116 is shown to originate near the EUV collector 102 and then enter the asymmetric discharge section 132. Different from the embodiment shown in FIG. 12A, the asymmetric discharge section 132 of the embodiment shown in FIG. 12B allows a flow pattern that does not substantially circulate backward or loop back along the vessel inner wall 104. As a result, the peripheral supply flow path 116 can reduce the contact cases of the Sn debris carried by the gas with the vessel inner wall 104.

[0181] [000218] FIG. 12B also shows a DGL supply flow path 118 through which gas is introduced into the vessel 100 via the DGL supply section 110. Each of the DGL supply flow paths 118 enters and exits the vessel 100 with fewer cases of looping back or backward circulation. Here too, as a result of fewer cases of looping back or backward circulation, the contact cases of the gas introduced by the DGL supply section 110 and the by-products that this gas can carry with the vessel inner wall 104 are reduced.

[0182] [000219] In the embodiment shown in FIG. 12B, it is also shown that the curtain supply unit 122 introduces gas into the container 100 at a location close to the IF region 157 of the container 100. The gas introduced through the curtain supply unit 122 is shown to follow the curtain supply flow path 136 that enters the container 100 as a curtain flow in the lateral direction away from the IF region 157. It is also shown that the gas introduced through the curtain supply unit 122 then exits the container 100 through the asymmetric discharge unit 132. Similar to most of the other flow paths of the embodiment shown in FIG. 12B, each of the curtain supply flow paths 136 enters and exits the container so as to reduce the contact cases with the container inner wall 104. In a particular embodiment, the curtain supply unit 122 may be composed of a slit nozzle or a nozzle array that introduces a gas flow substantially parallel to the container inner wall 104. Although not shown, the flow paths resulting from the gas being introduced by the plurality of nozzles 120 of the shower head 101 also enter and exit the container without substantially looping back or circulating rearward toward the container inner wall 104.

[0183] [000220] Although representative flow paths of some supply units are shown, it should be understood that some supply units may be excluded from the embodiment shown in FIG. 12B while still maintaining the overall directionality and flow shape of the gas flowing not only away from the ceiling region 104a of the container inner wall 104 but also away from the EUV collector 102. For example, if the curtain supply unit 122 is excluded from the embodiment shown in FIG. 12B, the remaining central supply flow path 114, peripheral supply flow path 116, and DGL supply flow path 118 will head toward the asymmetric discharge unit 132 and maintain a similar overall shape in the direction away from the EUV collector 102 and the container inner wall 104. However, it is noted that when the asymmetric discharge unit 132 is realized by a gas flow emitted from the container inner wall 104 such as provided by the shower head 101, a significant reduction in loop-back and rearward-circulating flow paths can be achieved.

[0184] [000221] Each of the individual flow paths 114, 116, 118, and 136 is representative and should not be construed as limiting the number of inlets used for each of the central supply section 106, the peripheral supply section 108, the DGL supply section 110, or the curtain supply section 122. For example, each of the supply sections may include any number of inlets for introducing gas at their respective locations.

[0185] [000222] FIG. 13 is a cross-sectional view of the Sn concentration gradient calculated based on a CFD simulation of an EUV container 100 having a plurality of nozzles 120 (e.g., of a showerhead) that are distributed laterally along the inner wall 104 of the container and introduce a gas flow 140 into the container 100 according to one simulated embodiment. Each of the showerhead nozzles 120 is shown to introduce the gas flow 140 in a direction away from the inner wall 104 of the container. As a result, there is a first region 142 directly adjacent to the inner wall 104 of the inner space 100a of the container having an Sn concentration that is approximately one order of magnitude less than the Sn concentration in a second region 144 that further extends into the inner space 100a of the container. Although not shown in the gradient scale, it has been found that regions further away from the inner wall 104, such as a third region 146, have an Sn concentration level that is at least one order of magnitude greater than the Sn concentration level in the first region 142. Thus, in a particular embodiment having nozzles 140 that introduce the gas flow 140 in a direction away from the inner wall 104 of the container, a certain level of protection from Sn debris can be obtained.

[0186] [000223] FIG. 14 is a cross-sectional view of an EUV container 100 having a curtain flow nozzle assembly 200 for introducing gas as a curtain flow into the container 100 according to one simulated embodiment. The EUV container 100 is shown to have a curtain flow nozzle assembly 200 disposed adjacent to the inner (plasma-facing) wall of the container inner wall 104. The curtain flow nozzle assembly 200 is shown to include a first outlet 202, a second outlet 204, and a third outlet 206, each for introducing gas into the container. The first outlet 202 is shown to introduce gas in a counterclockwise direction along the perimeter (e.g., the circumference in this example) of the container inner wall 104 in this figure, while the second outlet 204 is shown to introduce gas in a clockwise direction along the same perimeter in this figure. The third outlet 206 is shown to introduce gas generally in a direction away from the container inner wall 104.

[0187] [000224] The gas introduced by the first outlet 202 of the curtain flow nozzle assembly 200 is shown to result in a first curtain flow 212 extending from the first outlet 202. The gas introduced by the second outlet 204 is shown to result in a second curtain flow 214 extending from the second outlet 204. In certain embodiments, such as the embodiment shown in FIG. 14, the asymmetric discharge portion 132 may be oriented along a region of the container 100 opposite the region where the curtain flow nozzle assembly 200 of the container 100 may be disposed.

[0188] [000225] According to the embodiment shown in FIG. 14, a region adjacent to the inner wall 104 of the container within the inner space 100a of the container, such as the first region 208, exhibits an Sn concentration gradient that is many orders of magnitude smaller than the Sn concentration gradient in a region further away from the inner wall 104 of the container within the inner space 100a, such as the second region 210. According to a particular embodiment, the first and second curtain flows 212 and 214 provide a flow pattern within the inner space 100a of the container that protects the inner wall 104 from Sn debris contamination. In these embodiments, the first and second curtain flows 212 and 214 serve as a diffusion barrier along each wall portion along which they move. As a result of the reduction in the Sn concentration gradient near the inner wall 104 of the container, the contact cases of Sn debris with the inner wall 104 of the container are reduced.

[0189] [000226] In a particular embodiment, a third outlet 206 is also provided within the curtain flow nozzle assembly 200 to provide a flow pattern of gas within the inner space 100a of the container that is away from the curtain flow nozzle assembly 200 itself. As a result, the curtain flow nozzle assembly 200 is protected from Sn debris contamination. In certain other embodiments, the third outlet 206 may be excluded from the curtain flow nozzle assembly 200.

[0190] [000227] In some embodiments, the EUV container 100 may include a plurality of curtain flow nozzle assemblies 200 arranged horizontally along at least a portion of the inner wall 104 of the container. For example, in a particular embodiment, the plurality of curtain flow nozzle assemblies 200 may be arranged horizontally within a ceiling region located above the EUV collector (not shown) of the inner wall of the container in the direction of gravity. In these embodiments, the plurality of curtain flow nozzle assemblies may be arranged along a line segment (e.g., a generatrix in the case where the container is conical) from a region near the EUV collector to the IF region.

[0191] [000228] The curtain flow nozzle assembly 200 is shown as being located within the interior space 100a of the container (e.g., protruding beyond the inner wall 104 of the container), but other embodiments may have a curtain flow nozzle assembly 200 configured such that the openings of the first, second, and third outlets 202, 204, and 206 are in a plane more co-planar with the inner wall 104 of the container. Also, while the illustrated embodiment includes the asymmetric discharge portion 132, it should be understood that other embodiments may have a curtain flow nozzle assembly 200 that is implemented without the asymmetric discharge portion 132. Further, while the illustrated embodiment includes a smooth surface as the inner wall 104 of the container, certain other embodiments may include an inner wall 104 of the container having vanes, or a surface defined by vanes. For example, the vanes may be a separate structure that covers the inside of the inner wall 104 of the container and protrudes into the volume defined by the interior space 100a of the container. In these embodiments, the curtain flow nozzle assembly 200 may be incorporated into the vane structure or separated from the vane structure.

[0192] [000229] FIG. 15A is a cross-sectional view of an EUV container 100 having a showerhead 101 and an asymmetric discharge portion 132, showing the Sn concentration within the interior space of the container according to one simulated embodiment. The showerhead 101 is shown as being incorporated into the inner wall 104 of the container such that it shares a portion of the inner wall 104 as part of its structure. The showerhead 101 is shown as including a plurality of nozzles 120 that extend around the perimeter of the container 100. Each of the plurality of nozzles 120 is shown as introducing a gas flow 140 in a direction away from the inner wall 104 of the container.

[0193] [000230] The container 100 is also shown to include a central supply unit 106, a peripheral supply unit 108, a DGL supply unit 110, and a curtain supply unit 122. It is shown that the Sn concentration in the region adjacent to the inner wall 104 of the container interior space is lower than the Sn concentration in the region further away from the inner wall 104 and towards the central region of the container interior space 100a. For example, it is shown that the first region 218 adjacent to the inner wall 104 of the container has an Sn concentration that is several orders of magnitude lower than the Sn concentration in the second region 216 that is further away from the inner wall 104.

[0194] [000231] FIG. 15B is a cross-sectional view of an EUV container 100 having a shower head 101 and an asymmetric discharge unit 132, showing the debris deposition rate on the inner wall 104 of the container according to one embodiment and based on simulation. According to the embodiment shown, the region of the inner wall 104 protected by the shower head 101 has a deposition rate that is several orders of magnitude lower than the deposition rate of one or more walls provided in the asymmetric discharge unit 132. For example, there is a region 220 of the ceiling region 104a of the inner wall 104 that is above the EUV collector 102 in the gravitational direction and is shown to have the lowest deposition rate of Sn debris. In contrast, there is a region 222 of the wall of the asymmetric discharge unit 132 that is not located above the EUV collector 102 in the gravitational direction and is shown to have a deposition rate of about 200 - 1000 nm / hour or more (the color bar ends at 1000 nm / hour).

[0195] [000232] An embodiment is shown having a showerhead 101 with a nozzle 140 disposed to surround the perimeter of the inner wall 104 of the container, but it should be noted that there are other embodiments that can be realized without departing from the scope and spirit of the embodiment having a showerhead 101 with a nozzle 120 that does not cover the entire circumference of the inner wall of the container. For example, a particular embodiment may comprise a nozzle arrangement that does not cover the entire circumference of the inner wall 104 of the container and others that may only cover the entire circumference along a certain lateral distance along the inner wall 104 of the container. Further, while one arrangement pattern of the nozzles 120 is shown for illustrative purposes, it should be understood that various arrangements of the nozzles 120 that protect the inner wall 104 of the container may be used. For example, more or fewer nozzles 120 than shown may be used. Further, the pattern of arranging the nozzles 120 can be changed in terms of spacing, uniformity, nozzle diameter, etc. to meet the needs of various embodiments.

[0196] [000233] FIG. 16A is a cross-sectional view of an EUV container 100 having a curtain flow supply section 201 and an asymmetric discharge section 132 showing the Sn concentration in the internal space of the container according to an embodiment. The container 100 is shown to include a plurality of curtain flow nozzle assemblies 200 disposed laterally along the inner wall 104 of the container. Each curtain flow nozzle assembly 200 is shown to include a first gas outlet 202, a second gas outlet 204, and a third gas outlet 206. The first gas outlet 202 is shown to be a curtain flow that moves along the perimeter of the inner wall 104 of the container. The second gas outlet 204 is also shown to be a curtain flow that moves in a direction opposite to the first gas outlet 202 along the perimeter of the inner wall 104 of the container. The curtain flow nozzle assembly 200 is also shown to include a third gas outlet 206 that introduces gas into the container 100 in a direction away from the inner wall 104 of the container. Also, the container 100 is shown to include a central supply section 106, a peripheral supply section 108, a DGL supply section 110, and a curtain supply section 122.

[0197] [000234] Due to the presence of the curtain flow supply unit 201, it has been shown that the Sn concentration in the region adjacent to the inner wall 104 of the container inner space 100a is lower than the Sn concentration in the region further away from the inner wall 104 and towards the central region of the container inner space 100a. For example, it has been shown that the first region 224 adjacent to the inner wall 104 has an Sn concentration that is several orders of magnitude lower than the Sn concentration in the second region 226 that is further away from the inner wall 104.

[0198] [000235] FIG. 16B is a cross-sectional view of an EUV container 100 having a curtain flow supply unit and an asymmetric discharge unit 132, showing the Sn deposition rate on the inner wall 104 of the container according to one embodiment and based on simulation. According to the embodiment shown, it has been shown that the region of the inner wall 104 protected by the curtain flow supply unit 201 has a deposition rate that is several orders of magnitude lower than the deposition rate of one or more walls provided in the asymmetric discharge unit 132. For example, there is a region 228 of the ceiling region 104a of the inner wall 104 that is above the EUV collector 102 in the gravitational direction and has been shown to have the lowest deposition rate of Sn debris. In contrast, there is a region 230 of the wall of the asymmetric discharge unit 132 that is not located above the EUV collector 102 in the gravitational direction and has been shown to have an Sn deposition rate that is several orders of magnitude higher than the Sn deposition rate in region 228.

[0199] [000236] While specific embodiments of EUV vessels with conical showerheads have been described, it should be understood that there are many ways to implement a showerhead within an EUV vessel that are within the scope and spirit of these embodiments. For example, a particular embodiment may have a separate body or manifold or multiple gas lines and have a showerhead that supplies each of the plurality of nozzles. The separate body or manifold or multiple gas lines that supply the showerhead may be disposed behind the inner wall of the vessel (e.g., the non-plasma facing surface of the inner wall of the vessel). In certain other embodiments, the separate body or manifold of the showerhead may be disposed on the plasma facing surface such that the separate body or manifold itself may define at least a portion that is exposed to the plasma and Sn debris of the inner wall of the vessel. In yet other embodiments, the separate body or manifold may be one with an inner wall of the vessel such that the inner wall of the vessel constitutes a portion of the showerhead. In these and other embodiments, the inner wall of the vessel may include an embedded path or channel that includes a separate body or manifold or multiple gas lines that supply the showerhead. Further, in these embodiments, the showerhead may be incorporated into the inner wall of the vessel. In certain other embodiments, the showerhead may or may not have a distributed body or manifold. As described above, for example, the plurality of nozzles of the showerhead may be supplied by gas lines that join each of the nozzles. Thus, the showerhead may simply be defined as a plurality of nozzles configured in the same manner as a showerhead.

[0200] [000237] In one embodiment having generally a conical shape, the EUV source comprises a container having an upper conical region, a focus conical region, and an intermediate conical region disposed between the upper conical region and the focus conical region, and the upper conical region and the focus conical region are disposed at both ends of the container. This embodiment has a reflective surface and comprises an EUV collector disposed inside the container, and the reflective surface is configured to directionally face the focus conical region of the container. This embodiment also comprises a conical showerhead disposed along at least a portion of the inner wall of the container. The conical showerhead comprises a plurality of nozzles for introducing gas into the container. This embodiment also includes a plurality of discharge portions oriented near the focus conical region for removing the gas introduced into the container so that the gas introduced into the container flows away from the EUV collector.

[0201] [000238] In another embodiment having generally a conical shape, the EUV source comprises a container having an upper conical region, a focus conical region, and an intermediate conical region disposed between the upper conical region and the focus conical region, and the upper conical region and the focus conical region are disposed at both ends of the container. This embodiment has a reflective surface and comprises an EUV collector disposed inside the container, and the reflective surface is configured to directionally face the focus conical region of the container. This embodiment has a plurality of inlets for introducing gas into the container and comprises a first gas source disposed near the reflective surface of the EUV collector. This embodiment also comprises a conical showerhead disposed along at least a portion of the inner wall of the container and having a plurality of nozzles for introducing gas into the container. This embodiment also comprises a discharge portion oriented at an asymmetric position between the upper conical region and the focus conical region for discharging gas from the container. In a particular embodiment, the asymmetric discharge portion may be oriented, for example, at a downward inclination angle in the direction of gravity. In these and other embodiments, the asymmetric discharge portion may be oriented to face a region near the ceiling area above the EUV collector in the direction of gravity on the inner wall of the container.

[0202] [000239] In another embodiment having generally a conical shape, the EUV source comprises a container having an upper conical region, a focus conical region, and an intermediate conical region disposed between the upper conical region and the focus conical region, wherein the upper conical region and the focus conical region are disposed at both ends of the container. This embodiment comprises an EUV collector having a reflective surface and disposed inside the container, and the reflective surface is configured to directionally face the focus conical region of the container. This embodiment has a plurality of inlets for introducing gas into the container and comprises a first gas source disposed near the reflective surface of the EUV collector. This embodiment also includes a second gas source disposed laterally at least partially along a portion of the inner wall of the container and having a plurality of nozzle assemblies. According to this embodiment, each of the nozzle assemblies comprises a first outlet and a second outlet for introducing gas into the container, and the first outlet is configured to introduce gas in a first direction away from a second direction in which the second outlet is configured to introduce gas.

[0203] [000240] FIG. 17 shows another embodiment of a radiation source that can be provided in the form of an EUV source SO. The EUV source SO includes a chamber that can be provided in the form of an EUV container 100. The EUV container 100 includes an inner wall 104 and a material target region 111. The EUV source SO includes a radiation collector that can be provided in the form of an EUV collector 102 disposed within the EUV container 100. The EUV collector 102 is configured to collect radiation, such as EUV radiation 115 emitted from the material target region 111, and direct the collected EUV radiation 115 to an intermediate focus (IF) region 157. The focus 157a of the EUV collector (also referred to as the intermediate focus 157a) is located in or near the intermediate focus region 157 as described herein. The EUV source SO, such as the EUV container 100, includes a debris mitigation system. The debris mitigation system may include, or be provided in the form of, a central supply section 106, a peripheral supply section 108, and / or a DGL supply section 110 as described above. The debris mitigation system, such as the DGL supply section, is configured to direct a first gas flow from the intermediate focus region 157 to the material target region 111. The first gas flow may be, or include, a gas supplied by the DGL supply section 110. It will be understood that the terms "first gas flow" and "gas supplied by the DGL supply section" may be used interchangeably.

[0204] [000241] The debris mitigation system is configured to direct a second gas flow from a portion of the container inner wall 104 into the EUV container 100. For example, the debris mitigation system includes a showerhead 101 having a plurality of nozzles 120 for introducing the second gas flow or gas into the EUV container 100. The second gas flow may be, or include, a gas supplied by the showerhead 101. It will be understood that the terms "second gas flow" and "gas supplied by the showerhead" may be used interchangeably.

[0205] [000242] In the example shown in FIG. 17, the showerhead 101 is provided in the form of the first showerhead 101a and the second showerhead 101b as described above. The first showerhead 101a includes a first plurality of nozzles 120a, and the second showerhead 101b includes a second plurality of nozzles 120b. The first and second pluralities of nozzles 120a, 120b may be provided to direct the gas supplied by the showerhead 101, for example, the first and second showerheads 101a, 101b, into the EUV vessel 100. In other embodiments, it will be understood that, as described above, the second gas flow may be supplied by a curtain flow supply unit.

[0206] [000243] The EUV vessel 100 includes a guiding device that may be provided in the form of a flow splitter 150. The flow splitter 150 is disposed within the EUV vessel 100 such that the gas supplied by the DGL supply unit 110 is directed around the flow splitter 150. The EUV vessel 100 includes a discharge portion 132 for removing the gas supplied by the debris reduction system from the EUV vessel. The discharge portion 132 may be configured to remove debris carried by the gas from the EUV vessel 100. The discharge portion 132 is disposed, as described above, to extend from a portion of the inner wall 104 of the EUV vessel 100, for example, at an azimuthally asymmetric position. The EUV vessel 100 shown in FIG. 17 is the same as those shown in FIGS. 10, 12B, 15A, and 15B and may include any of the features described above in relation to FIGS. 10, 12B, 15A, and 15B.

[0207] [000244] FIG. 18A shows a simulated flow path of the gas supplied by the DGL supply unit 110, the shower head 101, the central supply unit 106, and / or the peripheral supply unit 108. As described above, the central supply unit 106 introduces the gas that follows the central supply flow path 114. The peripheral supply unit 108 introduces the gas that follows the peripheral supply flow path 116 (shown together with the central supply flow path 114 in FIG. 18A). The gas introduced by the DGL supply unit 110 follows the DGL supply flow path 118. Each of the shower head nozzles 120 (for example, each of the first and second plurality of nozzles 120a, 120b) introduces the gas that follows the flow path 140, as shown in FIG. 18A.

[0208] [000245] The debris mitigation system may be configured to direct a third gas flow or gas from a position at or near the position of the flow splitter 150 (or the intermediate focus region 157) in the EUV container towards the material target region 111. The debris mitigation system may be configured to direct a third gas flow from a position on the inner wall 104 towards the material target region 111. The debris mitigation system may include a curtain supply unit 122, as described above. The gas introduced via the curtain supply unit 122 follows the curtain supply flow path 136. It will be understood that the terms "third gas flow" and "gas supplied by the curtain supply unit" may be used interchangeably.

[0209] [000246] The gas supplied by the central supply unit 106 and / or the peripheral supply unit 108 may be or may be included in the fourth gas stream. It will be understood that the terms "fourth gas stream" and "gas supplied by the central supply unit 106 and / or the peripheral supply unit 108" may be used interchangeably. A debris mitigation system, such as the central supply unit 106, the peripheral supply unit 108, may be configured to direct the fourth gas stream from the EUV collector 102 towards the material target area 111. The flow splitter 150 may be configured to suppress or prevent the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the central supply unit 106 and / or the peripheral supply unit 108. The flow splitter 150 may be configured to prevent the formation of, for example, a jet of the gas supplied by the DGL supply unit 110 towards the EUV collector 102.

[0210] [000247] The flow rate of the gas supplied by the DGL supply unit 110 may be selected to prevent debris from entering the intermediate focus region 157. The flow rate of the gas supplied by the DGL supply unit 110 may be selected according to the gas supplied by the DGL supply unit 110, the density or pressure of the gas supplied by the DGL supply unit 110, the debris, such as the size of particulate debris, or the velocity of the debris and / or the diffusion direction of the debris in the EUV chamber of the radiation source SO. Additionally or alternatively, the flow rate of the gas supplied by the DGL supply unit 110 may be selected according to the configuration or shape of the DGL supply unit. For example, the flow rate of the gas supplied by the DGL supply unit 110 may be selected according to the number of openings of the DGL supply unit 110, the cross-sectional width (e.g., diameter) of each opening of the DGL supply unit 110, and / or the cross-sectional width (e.g., diameter), outer perimeter or dimensions of the intermediate focus region 157. For example, the maximum velocity of the gas supplied by the DGL supply unit 110 may be in the range of about 1000 to 3000 m / s.

[0211] [000248] The gas supplied by the DGL supply unit 110 may have a flow rate in the range of about 5 to 30 slm. The debris may include particulate debris such as Sn clusters, Sn fine particles, Sn nanoparticles, and / or Sn deposits as described above, and molecular and / or atomic debris such as Sn vapor, SnH x vapor, Sn atoms, Sn ions, etc. A flow rate of about 7 slm may be sufficient to prevent the molecular and / or atomic debris generated in the EUV vessel 100 from entering the intermediate focus region 157. In order to suppress the particulate debris from reaching the intermediate focus region 157, it may be necessary to increase the flow rate of the gas supplied by the DGL supply unit 110 to be greater than 7 slm. For example, in order to suppress the particulate debris from reaching the intermediate focus region 157, it may be necessary to increase the flow rate of the gas supplied by the DGL supply unit 110 to be greater than 15 slm. At a flow rate greater than 15 slm, such as 20 slm, an interaction between the gases supplied by the shower head 101 and / or the curtain supply unit 122 may be observed. Due to this interaction, the debris in the EUV vessel 100 may disperse before being removed from the EUV vessel 100 by the discharge unit 132 using some of the gas, and / or contamination of the inner wall 104 of the EUV vessel 100 may occur.

[0212] [000249] The flow splitter 150 is configured to suppress the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the shower head 101, and / or the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the curtain supply unit 122. By suppressing the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the shower head 101, and / or the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the curtain supply unit 122, it is possible to suppress the dispersion of debris before it is removed from the EUV vessel by the discharge unit 132. This can further reduce the contamination of the EUV vessel, for example, the inner wall of the EUV vessel. The debris reduction system, for example, the shower head 101 and / or the curtain supply unit 122, may be configured or arranged such that the gas supplied by the shower head 101 and / or the curtain supply unit 122 directs the debris towards the discharge unit 132.

[0213] [000250] FIG. 18B shows the simulated debris concentration inside the EUV vessel 100. It can be seen from FIG. 18B that by providing the flow splitter 150, the shower head 101 and / or the curtain supply unit 122, the debris can be directed towards the discharge unit 132 while reducing the contamination of the EUV vessel 100, for example, the inner wall 104 of the EUV vessel.

[0214] [000251] Referring to FIG. 17, the flow splitter 150 is arranged such that the gas supplied by the DGL supply unit 110 is directed symmetrically around the flow splitter 150. The flow splitter 150 may be configured to diffuse or disperse, for example, symmetrically diffuse or disperse the gas supplied by the DGL supply unit 110. By arranging the flow splitter 150 within the EUV vessel 100, for example, at least a portion of the gas supplied by the DGL supply unit 110 can be suppressed from recirculating within the EUV vessel 100 due to the interaction of the gas supplied by the DGL supply unit 110 with the gas supplied by the showerhead 101, the curtain supply unit 122, the central supply unit 106 and / or the peripheral supply unit 108. Thereby, debris deposited on the inner wall 104 of the radiation source SO can be reduced. Additionally or alternatively, by arranging the flow splitter 150 within the EUV vessel 100 such that the gas supplied by the DGL supply unit 110 is directed around the flow splitter 150, contamination of the flow splitter 150, for example by debris, can be reduced or prevented.

[0215] [000252] The flow splitter 150 may be disposed within the EUV vessel 100 of the radiation source SO in order to maintain the maximum speed of the gas supplied by the DGL supply unit 110 at a first location within the radiation source SO. At the first location, the speed of the gas supplied by the DGL supply unit 110 may match (or substantially match) the maximum speed of the gas supplied by the DGL supply unit 110, for example, when no flow splitter is disposed within the EUV vessel 100 of the radiation source SO. The flow splitter 150 may be disposed within the EUV vessel 100 of the radiation source SO to diffuse or disperse the gas supplied by the DGL supply unit 110 and to prevent or suppress recirculation of at least a portion of the gas supplied by the DGL supply unit 110, for example, in a direction toward the intermediate focus 157a. The flow splitter 150 may be disposed within the radiation source SO to diffuse or disperse the gas supplied by the DGL supply unit 110 at a second location that may be spaced apart from or away from the intermediate focus 157a. The flow splitter 150 may be disposed within the EUV vessel 100 of the radiation source SO such that the maximum speed of the gas supplied by the DGL supply unit 110 decreases at the second location and / or the minimum speed of the gas supplied by the DGL supply unit 110, which may be directed away from the intermediate focus 157a, increases.

[0216] [000253] Referring to FIG. 17, the flow splitter 150 is disposed within the EUV vessel 100 so as to extend into a portion of the EUV vessel 100. For example, the flow splitter 150 may be disposed so as to extend at least partially along the optical axis OA of the EUV collector 102. In other words, the flow splitter 150 may be disposed within the EUV vessel 100 such that the central axis or longitudinal axis A of the flow splitter 150 (shown in FIG. 19A) coincides with at least a part of the optical axis OA of the EUV collector 102. The EUV vessel 100 may have a conical shape that extends from the intermediate focus region 157 towards or near the EUV collector 102. The conical shape of the EUV vessel 100 may enable a symmetric arrangement of the flow splitter 150 within the EUV vessel 100. It will be understood that the exemplary EUV vessels described herein are not limited to those including a conical portion. For example, the EUV vessel or a portion thereof may have any suitable shape that reduces the volume of the EUV vessel, for example, without blocking the EUV radiation 115.

[0217] [000254] The flow splitter 150 is disposed in or near the intermediate focus region 157. For example, the flow splitter 150 is disposed in or near the intermediate focus region 157 so that the flow splitter 150 can act on the gas supplied by the DGL supply unit 110.

[0218] [000255] The flow splitter 150 may be disposed at a distance from the intermediate focus 157a. The distance of the flow splitter 150 from the intermediate focus 157a may be within the range of 5 to 15 cm. However, it should be understood that the arrangement of the flow splitter 150 within the radiation source SO is not limited to such a distance, and other distance values may be selected. For example, the distance may be selected according to the available space in or near the intermediate focus region and / or the heat load that can act on the flow splitter 150 due to the radiation in the intermediate focus region. In other words, the distance may be selected so as to minimize or prevent any thermal effect on the flow splitter 150, such as melting of the flow splitter 150.

[0219] [000256] The flow splitter 150 may be arranged to extend at least partially along the central axis, i.e., the vertical axis, of the EUV vessel 100 that coincides with at least a part of the optical axis OA of the EUV collector 102 in this example. With this arrangement, the flow splitter 150 can direct the gas supplied by the DGL supply unit 110 symmetrically around the flow splitter 150, for example, suppressing or preventing the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the shower head 101, and / or the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the curtain supply unit 122. Also, with this arrangement, the flow splitter 150 can direct the gas supplied by the DGL supply unit 110 symmetrically around the flow splitter 150, for example, suppressing or preventing the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the central supply unit 106 and / or the peripheral supply unit 108, and / or preventing the formation of a jet, for example, of the gas supplied by the DGL supply unit 110 toward the EUV collector 102.

[0220] [000257] The exemplary flow splitter 150 shown in FIG. 19A is configured to be tapered from a first end 150a to a second end 150b. The first end 150a of the flow splitter 150 may include or define an enlarged portion. The flow splitter 150 may be disposed within the EUV vessel 100 such that the first end 150a of the flow splitter 150, for example, the enlarged portion, is located distally from the intermediate focus region 157. The second end 150b of the flow splitter 150 may define or include a pointed tip 150a. The flow splitter 150 may be disposed within the EUV vessel 100 such that the second end 150b of the flow splitter, for example, the pointed tip, is located at or proximally to the intermediate focus region 157. The exemplary flow splitter 150 shown in FIG. 19A has a conical shape.

[0221] [000258] FIG. 19B shows another exemplary configuration of the flow splitter 150. The flow splitter 150 shown in FIG. 19B is similar to that shown in FIG. 19A. The first end 150a of the flow splitter 150 defines or includes an enlarged portion. The second end 150b of the flow splitter 150 includes or defines a rounded portion. The exemplary flow splitter shown in FIG. 19B may be considered to have a substantially frustoconical shape. It should be understood that the flow splitters disclosed herein are not limited to conical or frustoconical shapes. In other examples, the flow splitter may have a conical or frustoconical shape with one or more flat portions. Alternatively, the flow splitter may have a spiral or helical shape.

[0222] [000259] Referring to FIGS. 19A and 19B, for example, the length or dimension of the flow splitter 150 along the longitudinal axis or central axis A of the flow splitter 150 may be selected according to the dimensions, volume and / or shape of the EUV vessel 100. The length or dimension of the flow splitter 150 may be selected such that, as described above, for example when the flow splitter 150 is disposed within the EUV vessel 100, the flow splitter 150 interacts with the gas supplied by the DGL supply unit 110 and / or the flow splitter directs the gas supplied by the DGL supply unit 110 around the flow splitter 150. An exemplary length or dimension of the flow splitter 150 along the longitudinal axis or central axis A of the flow splitter 150 may include about 3 to 30 cm, for example 10 to 20 cm. However, it should be understood that the exemplary flow splitters disclosed herein are not limited to such lengths or dimensions.

[0223] [000260] The EUV source SO may include a heating element 152 that may be part of or included in the flow splitter 150. The heating element 152 may be configured to increase the temperature of the flow splitter 150, for example, to increase the amount of gas supplied by the DGL supply unit 110 directed around the flow splitter 150.

[0224] [000261] The heating element 152 may be configured to raise the temperature of the flow splitter 150 to a first temperature or higher that directs the amount of gas supplied by the increased DGL supply unit 110 around the flow splitter 150. For example, as a result of the temperature of the flow splitter 150 rising to the first temperature or higher, when at least a portion of the gas supplied by the DGL supply unit 110 contacts the flow splitter 150, the velocity of at least some of the atoms of the gas supplied by the DGL supply unit 110 may increase. By the temperature of the flow splitter 150 rising to the first temperature or higher, heat may conduct to a portion of the gas supplied by the DGL supply unit 110 that contacts the flow splitter 150. By heat conducting to a portion of the gas supplied by the DGL supply unit, a portion of the gas may expand and / or the viscosity of a portion of the gas may increase. In other words, the gas of a portion of the gas supplied by the DGL supply unit 110 that contacts the flow splitter 150 may have an increased viscosity. The gas of a portion of the gas supplied by the DGL supply unit 110 having an increased viscosity can act on another portion of the gas supplied by the DGL supply unit 110 that impinges on the flow splitter 150 and / or can direct another portion of the gas supplied by the DGL supply unit 110 around the flow splitter 150. In other words, by the viscosity of a portion of the gas supplied by the DGL supply unit 110 increasing, the effective dimension of the flow splitter 150 can be considered to be larger than the actual dimension of the flow splitter 150.

[0225] [000262] The first temperature may be equal to or higher than the melting temperature of the fuel used to generate the plasma 107. In other words, the first temperature may be selected according to the fuel used to generate the plasma 107. For example, when tin is used as the fuel, the heating element 152 may be configured to raise the temperature of the flow splitter 150 to a temperature of about 230 °C or higher (substantially matching the melting temperature of tin). At a temperature below 200 °C, the fuel deposited on the flow splitter 150, such as tin, may be solid. The solid fuel may diffract or block at least a portion of the EUV radiation 115 directed towards the intermediate focus 157a.

[0226] [000263] The heating element 152 may be configured to maintain the temperature of the flow splitter 150 below a second temperature. Above the second temperature, the diffusion of debris that may be present on the flow splitter occurs or increases. For example, above the second temperature, the diffusion of debris that may be present on the flow splitter 150 may increase. For example, the diffusion coefficient of tin vapor in a hydrogen atmosphere may increase with an increase in temperature. By maintaining the temperature of the flow splitter 150 below the second temperature, the diffusion of debris within the EUV vessel 100 can be suppressed. The amount of debris on the flow splitter 150 may be considered small, for example, for arranging the flow splitter 150 within the EUV vessel 100 and directing the gas supplied by the DGL supply unit 110 around the flow splitter 150.

[0227] [000264] The heating element 152 may be embedded within the flow splitter 150. In other embodiments, it will be understood that the heating element may be provided separately. In such embodiments, the heating element may be arranged to raise the temperature of the flow splitter. The heating element 152 may be provided in the form of a resistive heating element. In other embodiments, it will be understood that the flow splitter may be inductively heated and / or the heating element may be provided in the form of an electromagnetic element, such as a coil. An electronic oscillator, such as a high-frequency generator, may be provided to generate a current in the electromagnetic element, and as a result, heat may be generated in the electromagnetic element.

[0228] [000265] Referring to FIGS. 17 and 19C, in some embodiments, the flow splitter 150 may be configured to be cooled by a coolant. For example, the flow splitter 150 may be cooled to reduce a heat load that may act on the flow splitter 150, for example, due to EUV radiation in the intermediate focus region 157. The flow splitter 150 may be cooled to maintain the temperature of the flow splitter 150 below the melting temperature of the fuel used to generate the plasma 107. Thereby, the dispersion / diffusion of the liquid fuel on the inner wall 104 of the radiation source SO or any other component of the flow splitter 150 that may be present on the flow splitter 150 can be prevented. As described above, the amount of debris that may be present on the flow splitter 150 is considered to be small, for example, to dispose the flow splitter 150 within the EUV vessel 100 and direct the gas supplied by the DGL supply unit 110 around the flow splitter 150.

[0229] [000266] The coolant may be supplied by a coolant source 154. For example, the flow splitter 150 may include channels 156 for receiving the coolant from the coolant source 154 and / or for flowing the coolant through the flow splitter 150. The flow splitter 150 may be configured to connect to the coolant source 154. The coolant source 154 may be configured to supply the coolant to the flow splitter 150. For example, the coolant source 154 may be configured to supply the coolant to the flow splitter 150 to reduce the temperature of the flow splitter 150 below the melting temperature of the fuel used to generate the plasma 107 and / or a second temperature, as described above. The coolant may be provided in the form of a coolant fluid, for example, a coolant liquid or a coolant / cooling gas. It will be understood that the flow splitter may be configured to be cooled by a coolant instead of or in addition to including the heating element 152.

[0230] [000267] FIG. 20 schematically shows another embodiment of the EUV source SO. The EUV source SO shown in FIG. 20 is the same as that shown in FIG. 17. The exemplary flow splitter 150 of the radiation source SO shown in FIG. 20 includes a plurality of other openings 158 that can be provided in the form of nozzles or slits. The plurality of other openings 158 (or each separate opening of the plurality of other openings 158) may be configured to direct the fifth gas stream 160 towards the EUV collector 102. The fifth gas stream may have a flow rate in the range of about 1 to 50 slm. The plurality of other openings 158 may be arranged in the flow splitter 150 such that the fifth gas stream 160 from the plurality of other openings 158 interacts with the gas supplied by the DGL supply unit 110. The interaction between the gas supplied by the DGL supply unit 110 and the fifth gas stream 160 can direct or push the gas supplied by the DGL supply unit 110 near the inner wall 104 of the EUV vessel 100. By providing the plurality of other openings 158 to direct the fifth gas stream 160 towards the EUV collector 102, the dispersion of the gas supplied by the DGL supply unit 110 can be enhanced. As a result of the increased dispersion of the gas supplied by the DGL supply unit 110, the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the shower head 101, and / or the interaction between the gas supplied by the DGL supply unit 110 and the gas supplied by the curtain supply unit 122 may be reduced or suppressed.

[0231] [000268] The plurality of other openings 158 may be arranged circumferentially, circumferentially and / or axially in the flow splitter 150. In other words, the plurality of other openings 158 may be arranged to extend around the flow splitter 150 and / or in the direction of the central axis, i.e., the longitudinal axis A, of the flow splitter 150. The plurality of other openings 158 may be symmetrically arranged in the flow splitter 150 such that, for example, the gas supplied by the DGL supply unit 110 and / or the fifth gas stream 160 flow symmetrically around the flow splitter 150.

[0232] [000269] The DGL supply unit 110 may be configured to supply a fifth gas stream 160 to the flow splitter 150. For example, the flow splitter 150 can be connected to or made connectable to the DGL supply unit 110, for example, to enable the supply of the fifth gas stream 160 to the flow splitter 150. In another example, it will be understood that the debris mitigation system may include another gas supply system configured to supply a gas stream to the flow splitter. The flow splitter can be connected to or made connectable to another gas supply system, for example, to enable the supply of the gas stream to the flow splitter. The flow splitter 150 shown in FIG. 20 includes a plurality of other openings 158, but in other embodiments, it will be understood that the flow splitter may include one other opening configured to direct the fifth gas stream toward the EUV collector.

[0233] [000270] FIG. 21 schematically shows another embodiment of the EUV source SO. The EUV source SO shown in FIG. 21 is similar to that shown in FIG. 17. The exemplary EUV source SO shown in FIG. 21 includes a debris receiving surface 162a that can be part of or provided by a bar, i.e., an obscuration bar 162. The bar 162 may be disposed within the EUV vessel 100 so as to suppress or prevent debris from reaching the intermediate focus region 157. The bar 162 may be disposed so as to intersect or extend across the optical axis OA of the EUV collector 102. In this arrangement, the bar 162 can be considered to block the direct line of sight of debris that may include ballistic particulate debris and / or a portion of the laser radiation 105, for example, the portion of the laser radiation 105 that passes through the material target region 111. In other words, the bar 162 may be configured to reflect a portion of the laser radiation 105 away from the intermediate focus region 157 of the EUV source SO.

[0234] [000271] In the exemplary EUV source shown in FIG. 21, the flow splitter 150 is disposed between the bar 162 and the intermediate focus region 157. In this arrangement, the bar 162 is disposed so as to extend over or overlap at least a part or all of the flow splitter 150. For example, the bar 162 may be disposed so as to extend over or overlap with the enlarged portion of the first end 150b of the flow splitter 150 such that debris generated by the plasma 107 impinges on the debris receiving surface 162a of the bar 162. In other words, the flow splitter 150 may be disposed in the shadow of the bar 162.

[0235] [000272] In the exemplary EUV source SO shown in FIG. 21, the debris receiving surface 162a has been described as being part of the bar 162, but it will be understood that in other embodiments of the EUV source, such as those described in connection with FIGS. 17 and 20, the debris receiving surface 162a may be provided by or be part of the flow splitter 150. In such an example, the flow splitter 150 may include any of the features of the bar 162 described above. Further, the flow splitter 150 may be configured to withstand the heat or heat load generated by the plasma 107 or the heat or heat load of the EUV radiation 115 in the intermediate focus region 157. The flow splitter 150 may be configured to reflect a portion of the laser radiation 105 passing through the material target region 111 in a direction away from the intermediate focus region 157. For example, when the debris receiving surface 162a is provided by the flow splitter 150, the length or dimension of the flow splitter 150 in a direction perpendicular and / or parallel to the central axis, i.e., the longitudinal axis A, of the flow splitter 150 may be larger than the length or dimension of the flow splitter 150 in a direction perpendicular and / or parallel to the central axis, i.e., the longitudinal axis A, of the flow splitter 150 used in combination with the bar 162, for example.

[0236] [000273] The first, second, third, fourth, and / or fifth gas flow may include hydrogen gas. In other embodiments, it will be understood that another gas or mixture of gases may be used. For example, in other embodiments, the first, second, third, fourth, and / or fifth gas flow may include argon gas or helium gas.

[0237] [000274] The material of the flow splitter 150 may be selected to exhibit resistance to corrosion, for example, resistance to corrosion by fuel in an environment within the EUV source SO, such as a hydrogen environment within the EUV source SO. The material of the flow splitter 150 may be selected to exhibit resistance to the heat load acting on the flow splitter, as described above, for example, due to EUV radiation 115, plasma 107, and / or an increase in the temperature of the flow splitter 150 to a temperature above the first temperature in the radiation source SO. Exemplary flow splitters 150 may include a metal or metal alloy. For example, the material of the flow splitter may be, or may include, molybdenum, tungsten, aluminum, stainless steel, copper, or alloys thereof. The flow splitter 150 may comprise a metal surface or a metal alloy surface. The metal surface or metal alloy surface of the flow splitter may result in an improvement in the recombination of hydrogen radicals that may be present within the radiation source SO. For example, hydrogen (H2) molecules may be split into hydrogen radicals by heat absorption and / or radiation absorption, or ion collisions. Hydrogen radicals may be useful for removing debris, such as tin, from the inner wall 104 of the radiation source. The presence of hydrogen radicals may cause contamination within the EUV vessel 100, for example, fuel spitting when the hydrogen radicals diffuse into the liquid fuel layer within the EUV vessel 100. By providing a flow splitter having a metal surface or a metal alloy surface, the recombination of hydrogen radicals can be improved and / or contamination within the EUV vessel, such as fuel spitting, can be reduced.

[0238] [000275] In other embodiments, it will be appreciated that the flow splitter may comprise another material, such as a ceramic material. The ceramic material may comprise a silicon dioxide material, a zirconium nitride material, or a zirconium oxide material. Although specific reference has been made herein to embodiments in the context of lithographic apparatus, embodiments of the invention may be used in one or more other apparatus. Embodiments may form part of an apparatus for measuring or processing an object such as a mask inspection apparatus, a metrology apparatus, or a wafer (or other substrate) or mask (or other patterning device). These apparatus are sometimes generally referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0239] [000276] The term "at least a portion of a lithographic apparatus" may be considered to encompass the illumination system IL, the patterning device MA, and / or the projection system PS.

[0240] [000277] The term "radiation source" may be considered to encompass the laser 162.

[0241] [000278] The term "obstruct" may be considered to encompass substantially obstruct.

[0242] [000279] The term "intermediate focus region" may be considered to encompass regions at and / or near the intermediate focus.

[0243] [000280] The term "EUV radiation" may be considered to encompass electromagnetic radiation having a wavelength in the range of 4 to 20 nm, for example in the range of 13 to 14 nm. EUV radiation may have a wavelength in the range of 4 to 10 nm, for example 6.7 nm or 6.8 nm, which is less than 10 nm.

[0244] [000281] FIG. 1 shows the radiation source SO as a laser-produced plasma (LPP) source, but any suitable radiation source that generates EUV radiation may be used. For example, an EUV-emitting plasma may be generated by converting a fuel (e.g., tin) into a plasma state using a discharge. This type of radiation source may be referred to as a discharge-produced plasma (DPP) source. The discharge may be generated by a power source that may form part of the radiation source or may be a separate entity connected to the EUV radiation source SO via an electrical connection.

[0245] [000282] Although the flow splitter 150 has been described as being disposed within an EUV container having an asymmetric discharge section 132, it will be understood that in other embodiments the flow splitter may be used in an EUV container having a symmetric discharge section as shown, for example, in FIGS. 9B - 9C, 12A. Additionally or alternatively, the flow splitter may be used in an EUV container having a curtain flow supply section as shown, for example, in FIGS. 16A and 16B. The flow splitter may also be used in the EUV containers shown in FIGS. 9A and 11.

[0246] [000283] It will also be understood that each of the foregoing embodiments may be implemented in a temperature control system that adjusts the container inner wall 104 to achieve a specific temperature, similar to other components included in the EUV container 100. For example, certain portions of the container inner wall 104 may be maintained at a temperature below the melting point of Sn, while other portions may be maintained at a temperature above the melting point of Sn. In these and other embodiments, the temperature of each region of the container inner wall 104 may also be varied, i.e., cycled between a temperature above and below the melting point of Sn.

[0247] [000284] Although this specification particularly refers to the use of a lithographic apparatus in IC manufacture, it should be understood that the lithographic apparatus described herein may have other applications. Other possible applications include the manufacture of integrated optical systems, the induction and detection patterns of magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0248] [000285] Although particular mention has been made of the use of embodiments in the field of photolithography, it will be understood that embodiments of the invention may, depending on the context, be used in other applications, such as imprint lithography, and are not limited to photolithography. In imprint lithography, the topography within the patterning device defines a pattern created on a substrate. The topography of the patterning device is imprinted within a resist layer supplied to the substrate, and the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is removed from the resist, leaving a pattern inside the resist when it is cured.

[0249] [000286] As will be appreciated, aspects of one or more embodiments herein may be incorporated into one or more other embodiments herein, for example, as alternative or modified forms.

[0250] [000287] While particular embodiments of the invention have been described above, it will be understood that the invention may be practiced in other ways different from those described. The above description is illustrative and not intended to be limiting. Thus, it will be apparent to those skilled in the art that the invention may be modified as described, without departing from the scope of the claims set forth below and their equivalents.

Claims

1. A chamber including a plasma formation region, A radiation collector disposed in the chamber, configured to collect radiation emitted from the plasma formation region and direct the collected radiation toward an intermediate focus region, A debris mitigation system configured to direct a first gas flow from the intermediate focus region toward the plasma formation region, An induction device disposed in the chamber such that the first gas flow is directed circumferentially, A radiation source comprising the above.

2. The radiation source according to claim 1, wherein the induction device is arranged such that the first gas flow is directed symmetrically around and / or diffused by the induction device.

3. The radiation source according to claim 1 or 2, wherein the debris mitigation system is configured to direct a second gas flow from the radiation collector toward the plasma formation region.

4. The radiation source according to claim 3, wherein the induction device is configured to reduce the interaction between the first gas flow and the second gas flow.

5. The radiation source according to claim 3 or 4, wherein the induction device is configured to prevent the interaction between the first gas flow and the second gas flow.

6. The radiation source according to any one of claims 1 to 5, wherein the induction device is configured to prevent the formation of a jet of the first gas flow toward the radiation collector.

7. The radiation source according to any one of claims 1 to 6, wherein the induction device is disposed in the chamber so as to extend at least partially along the optical axis of the radiation collector.

8. The radiation source according to any one of claims 1 to 7, wherein the induction device is disposed in or near the intermediate focus region.

9. The radiation source according to any one of claims 1 to 8, wherein the induction device is arranged in a tapered shape from a first end of the induction device toward a second end of the induction device, the first end includes an enlarged portion, and the second end includes a pointed portion or a rounded portion.

10. The radiation source according to claim 9, wherein the induction device is disposed in the chamber such that the first end of the induction device is distally disposed from the intermediate focus region and the second end of the induction device is disposed in or proximal to the intermediate focus region.

11. The radiation source according to any one of claims 1 to 10, wherein the guiding device comprises a plurality of openings configured to direct a third gas flow towards the radiation collector.

12. The radiation source according to claim 11, wherein the plurality of openings are arranged in the guiding device such that the third gas flow from the plurality of openings interacts with the first gas flow to direct or push the first gas flow near at least a portion of the chamber.

13. The radiation source according to any one of claims 1 to 12, wherein the guiding device comprises a heating element configured to increase the temperature of the guiding device.

14. The radiation source according to claim 13, wherein the heating element is configured to increase the temperature of the guiding device to a first temperature at which an increased amount of the first gas flow is directed around the guiding device, and / or to maintain the temperature of the guiding device below a second temperature at which the diffusion of debris present on the guiding device is enhanced.

15. The radiation source according to any one of claims 1 to 14, wherein the guiding device is configured to be cooled by a coolant supplied by a coolant source.

16. The radiation source according to any one of claims 1 to 15, comprising a debris receiving surface disposed within the chamber to suppress or prevent debris from reaching the intermediate focus region.

17. The radiation source according to claim 16, wherein the debris receiving surface is arranged to intersect or extend across the optical axis of the radiation collector.

18. The radiation source according to claim 16 or claim 17, wherein the guiding device is disposed between the debris receiving surface and the intermediate focus region.

19. The radiation source according to any one of claims 16 to 18, wherein the debris receiving surface is arranged to extend over or overlap at least a portion or the whole of the guiding device such that debris generated in the plasma formation region is incident on the debris receiving surface.

20. The radiation source according to claim 16, wherein the debris receiving surface is included in, is part of, or is provided by the guiding device.

21. A radiation system comprising a laser and the radiation source according to any one of claims 1 to 20.

22. A lithography system comprising a lithography apparatus arranged to project a pattern from a patterning device onto a substrate, and a radiation system as claimed in claim 21 arranged to provide at least part of the radiation to the lithography apparatus.

23. A method of reducing debris deposition at a radiation source, the method comprising: directing a first gas flow from an intermediate focus region of the radiation source towards a plasma generation region of the radiation source, and directing the first gas flow around an induction device disposed within a chamber of the radiation source.

24. A container having an inner wall of the container and an intermediate focus (IF) region, an EUV collector disposed inside the container and connected to the inner wall of the container, the EUV collector comprising a reflective surface configured to be directionally oriented towards the IF region of the container, a showerhead disposed along at least a portion of the inner wall of the container and comprising a plurality of nozzles configured to introduce gas into the container, the showerhead having at least one inlet configured to supply the gas therein, one or more discharge portions configured to remove the gas introduced into the container and oriented along at least a portion of the inner wall of the container so as to flow the gas in a direction away from the EUV collector, an extreme ultraviolet (EUV) source comprising the above.

25. The EUV source according to claim 24, further comprising a material target region disposed within the container for generating plasma radiation collected by the reflective surface of the EUV collector and directed towards the IF region for incidence on at least a portion of a lithography apparatus, wherein by introducing the gas into the container via the plurality of nozzles, the inner wall of the container can be protected from deposition of material.

26. The EUV source according to claim 24 or claim 25, wherein the plurality of nozzles are oriented in a direction away from the inner surface of the inner wall of the container along at least a portion of the inner surface of the inner wall of the container.

27. The EUV source according to any one of claims 24 to 26, wherein the inner wall of the container has a conical shape, a cylindrical shape, or a polyhedral shape.

28. The EUV source according to any one of claims 24 to 27, wherein the showerhead extends in a circumferential direction and a transverse direction along at least a portion of the inner wall of the container.

29. The EUV source according to any one of claims 24 to 28, further comprising a container outer wall having one or more exhaust ports surrounding the container.

30. The EUV source according to any one of claims 24 to 29, wherein the shower head includes one or more zones each including at least a portion of the plurality of nozzles and realizing individually controllable zones for individually supplying gas to the container to introduce gas into the container.

31. The EUV source according to any one of claims 24 to 30, wherein the inner wall of the container is defined by a smooth surface, a blade surface, or a combination of a smooth surface and a blade surface.

32. A container having an inner wall of the container and an intermediate focus (IF) region, An EUV collector disposed inside the container and connected to the inner wall of the container, the EUV collector having a reflective surface configured to directionally face the IF region of the container, A first gas source configured to introduce gas into the container and having a first plurality of inlets disposed near the reflective surface of the EUV collector, A shower head having a plurality of nozzles disposed along at least a portion of the inner wall of the container and configured to introduce gas into the container, and having at least one inlet configured to supply gas therein, An exhaust portion disposed at an azimuthally asymmetric position along the inner wall of the container and configured to discharge gas from the container, An extreme ultraviolet (EUV) source comprising.

33. The EUV source according to claim 32, wherein the discharge portion is further oriented near a first region of the inner wall of the container generally facing a second region of the inner wall of the container located above the EUV collector in the gravitational direction, and the discharge portion allows the gas introduced by the first gas source and the plurality of nozzles to flow in a direction away from the second region during operation of the EUV source.

34. The EUV source according to claim 32 or claim 33, wherein the plurality of nozzles are at least partially distributed along a region of the inner wall of the container located above the EUV collector in the gravitational direction.

35. The EUV source according to any one of claims 32 to 34, wherein the plurality of nozzles are oriented in a direction away from the inner surface of the inner wall of the container along the inner surface of the inner wall of the container, and the orientation of the plurality of nozzles enables a gas flow that is at least partially directed away from at least a portion of the inner surface of the inner wall of the container.

36. The EUV source according to any one of claims 32 to 35, wherein the plurality of nozzles are disposed at least partially along a ceiling region located above the EUV collector of the inner wall of the container in the direction of gravity, the plurality of nozzles are oriented in a direction facing away from the ceiling region, and by introducing the gas through the plurality of nozzles, a diffusion barrier adjacent to the ceiling region for removing debris is provided.

37. The EUV source according to any one of claims 32 to 36, wherein the showerhead includes one or more zones each including at least a portion of the plurality of nozzles and realizing an individually controllable zone in which gas is individually supplied to each to introduce gas into the container.

38. The EUV source according to any one of claims 32 to 37, wherein the inner wall of the container has a conical shape, a cylindrical shape, or a polyhedral shape.

39. A container having an inner wall of the container and an intermediate focus (IF) region, An EUV collector disposed inside the container and connected to the inner wall of the container, the EUV collector having a reflecting surface configured to directionally face the intermediate focus region of the container, A plurality of nozzle assemblies disposed laterally at least partially along the inner wall of the container and each having at least a first outlet and a second outlet configured to introduce gas into the container, the first outlet being configured to introduce gas in a first direction away from a second direction in which the second outlet is configured to introduce gas, a container wall gas source, An exhaust portion configured to exhaust the gas introduced into the container, located near the IF region, and enabling the gas introduced by the container wall gas source to flow in a direction away from the EUV collector, An extreme ultraviolet (EUV) source comprising.

40. The EUV source according to claim 39, wherein the first direction and the second direction for introducing gas into the first outlet and the second outlet of each of the plurality of nozzle assemblies are oriented at least partially along the periphery of the inner wall of the container such that a curtain flow of gas along the periphery of the inner wall of the container is enabled.

41. The EUV source according to claim 39 or claim 40, further comprising a third outlet in at least a portion of the plurality of nozzle assemblies configured to introduce gas into the container, the third outlet being configured to introduce gas in a direction away from the inner wall of the container.

42. The plurality of nozzle assemblies are distributed at least partially along a first region located above the EUV collector of the inner wall of the container in the direction of gravity during operation of the EUV source, and the discharge portion is further oriented near a second region of the inner wall of the container facing the first region of the inner wall of the container such that the gas introduced into the container can flow in a direction away from the first region of the inner wall of the container. The EUV source according to any one of claims 39 to 41.

43. The EUV source according to any one of claims 39 to 42, wherein the inner wall of the container has a conical shape, a cylindrical shape, or a polyhedral shape.

44. A chamber including an inner wall and a material target region; A radiation collector disposed in the chamber and configured to collect radiation emitted from the material target region and direct the collected radiation to an intermediate focus region; A debris mitigation system configured to direct a first gas flow from the intermediate focus region to the material target region and a second gas flow from a portion of the inner wall of the chamber into the chamber; A guiding device disposed in the chamber such that the first gas flow is directed circumferentially; A discharge portion configured to remove the gas supplied by the debris mitigation system from the chamber; A radiation source comprising.

45. The radiation source according to claim 44, wherein the discharge portion is disposed at an azimuthally asymmetric position so as to extend from a portion of the inner wall of the chamber.

46. The debris mitigation system comprises a showerhead disposed along at least a portion of the inner wall of the chamber, the showerhead comprising a plurality of nozzles configured to introduce the second gas stream into the chamber, the radiation source according to claim 44 or claim 45.

47. The radiation source according to any one of claims 44 to 46, wherein the guiding device is configured to reduce the interaction between the first gas stream and the second gas stream.

48. The radiation source according to any one of claims 44 to 47, wherein the debris mitigation system is configured to direct a third gas stream from a position at or near the position of the guiding device in the chamber towards the material target region.

49. The radiation source according to claim 48, wherein the guiding device is configured to reduce the interaction between the first gas stream and the third gas stream.

50. The radiation source according to any one of claims 44 to 49, wherein the debris mitigation system is configured to direct a fourth gas stream from the radiation collector towards the material target region.

51. The radiation source according to claim 50, wherein the guiding device is configured to reduce the interaction between the first gas stream and the fourth gas stream.

52. The radiation source according to any one of claims 44 to 51, wherein the guiding device is disposed in a tapered shape from a first end of the guiding device towards a second end of the guiding device, the first end including an enlarged portion, and the second end including a pointed portion or a rounded portion.

53. The radiation source according to claim 52, wherein the first end of the guiding device is disposed distally from the intermediate focus region, and the second end of the guiding device is disposed in or proximally to the intermediate focus region in the chamber.

54. The radiation source according to any one of claims 44 to 53, wherein the guiding device is disposed in the chamber so as to extend at least partially along the optical axis of the radiation collector.

55. The radiation source according to any one of claims 44 to 54, wherein the guiding device comprises a plurality of openings configured to direct a fifth gas stream towards the radiation collector.

56. The radiation source according to claim 55, wherein the plurality of openings are arranged in the guiding device such that the fifth gas flow from the plurality of openings interacts with the first gas flow to direct or push the first gas flow near at least a part of the inner wall of the chamber.

57. The radiation source according to any one of claims 44 to 56, wherein the guiding device comprises a heating element configured to increase the temperature of the guiding device.

58. The radiation source according to claim 57, wherein the heating element is configured to raise the temperature of the guiding device to a first temperature at which an increased amount of the first gas flow is directed around the guiding device, and / or to maintain the temperature of the guiding device below a second temperature at which the diffusion of debris present on the guiding device is enhanced.

59. The radiation source according to any one of claims 44 to 58, wherein the guiding device is configured to be cooled by a coolant supplied by a coolant source.

60. The radiation source according to any one of claims 44 to 59, wherein the radiation source is disposed within the chamber and includes a debris receiving surface that suppresses or prevents debris from reaching the intermediate focus region.

61. The radiation source according to claim 60, wherein the debris receiving surface is included in the guiding device, is part of the guiding device, or is provided by the guiding device.

62. A radiation system comprising a laser and a radiation source according to any one of claims 24 to 61.

63. A lithography system comprising a lithography apparatus configured to project a pattern from a patterning device onto a substrate, and a radiation system according to claim 62 configured to provide at least a portion of the radiation to the lithography apparatus.

64. A method for reducing debris deposition in a radiation source, the method comprising: directing a first gas flow from an intermediate focus region of the radiation source to a material target region of the radiation source; directing a second gas flow from a portion of an inner wall of a chamber of the radiation source into the chamber; directing the first gas flow around a guiding device disposed within the chamber of the radiation source; and removing gas from the chamber The method includes.

65. A chamber including an inner wall and a material target region, A radiation collector disposed within the chamber, configured to collect radiation emitted from the material target region and direct the collected radiation to an intermediate focus region; A debris mitigation system comprising a first gas supply system and a second gas supply system; An exhaust section configured to remove the gas supplied by the debris mitigation system from the chamber, comprising: The first gas supply system is configured to direct a first gas flow from the intermediate focus region to the material target region or the plasma formation region, and is arranged with one or more openings configured to direct the first gas flow into the chamber in a direction substantially opposite to the propagation direction of the radiation beam; The second gas supply system comprises one or more openings arranged to direct the second gas flow in a direction substantially perpendicular to or inclined at an angle to the propagation direction of the first gas flow; A radiation source.

66. The radiation source according to claim 65, wherein the second gas supply system includes a pair of opposing gas flow jets.

67. The radiation source according to claim 65, wherein the first gas flow and the second gas flow interact via momentum exchange such that a substantially unidirectional gas flow field is established towards the exhaust section.

68. The radiation source according to claim 65, wherein the second gas supply system is arranged near the intermediate focus region downstream of the first gas flow.

69. The radiation source according to claim 65, wherein the first and second gas supply systems are arranged such that the velocity of the first gas flow is substantially equal to the velocity of the second gas flow in the immediate vicinity of the break point of the first and second gas flows.

70. The radiation source according to claim 65, wherein a guiding device is arranged within the chamber such that the first gas flow is directed radially outwards.

71. A showerhead comprising a plurality of nozzles arranged along at least a portion of the inner wall of the container and configured to introduce gas into the container, and having at least one inlet configured to supply the gas therein; One or more exhaust sections configured to remove the gas introduced into the container and oriented along at least a portion of the inner wall of the container to flow the gas away from the EUV collector; The radiation source according to claim 65, comprising:

72. The radiation source according to claim 65, wherein the discharge portion is disposed at an azimuthally asymmetric position along the inner wall of the container and is configured to discharge gas from the container.

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