Target material storage and delivery system for an EUV radiation source

Abstract

Disclosed is an apparatus adapted to deliver a molten target material such as tin to be irradiated and converted in a source of extreme ultraviolet radiation and components of such systems in which the components are exposed to the molten target material under pressure such as a housing of a filter through which the molten target material passes is comprised of an alloy of two refractory metals, for example, molybdenum and rhenium.

Description

TARGET MATERIAL STORAGE AND DELIVERY SYSTEM FOR AN EUV RADIATION SOURCECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 446,712, filed February 17,2023, titled TARGET MATERIAL STORAGE AND DELIVERY SYSTEM FOR AN EUV RADIATION SOURCE, which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The present disclosure relates to extreme ultraviolet radiation (“EUV”) sources that generate EUV radiation by converting a target material, in particular to devices and systems for storing and delivering the target material.BACKGROUND

[0003] EUV radiation, for example, electromagnetic radiation having a wavelength of around50 nm or less (also sometimes referred to as soft x-rays) and including light at a wavelength of about 13 nm, is used in photolithography processes to produce extremely small features in and on substrates, for example, silicon wafers.

[0004] Methods for generating EUV radiation include, but are not limited to, those in which radiation is produced by first converting the physical state of a target material to a plasma state. The plasma is typically produced in a sealed vessel, for example, a vacuum chamber, and monitored using various types of metrology equipment. The target material includes an element, for example, xenon, lithium, or tin, with an emission line in the EUV range. The target material may be solid, liquid, or gaseous just prior to introduction into the vacuum chamber.

[0005] In one known method involving a liquid target material the necessary plasma is produced by irradiating a droplet or cluster of target material with a drive laser. One technique for generating droplets involves melting solid target material and then supplying the liquid target material to a target material delivery system also referred to as a droplet generator. The target material delivery system forces the liquid target material under high pressure through a relatively small diameter orifice, such as an orifice having a diameter of about 0.5 pm to about 30 pm, to produce a stream of droplets. The droplet generator directs the droplets towards the primary focus of collector optics where at least some of the droplets are irradiated individually for EUV production.

[0006] In some systems the target material delivery system includes one or more reservoirs.The reservoir holds the target material in reserve for ready supply to the droplet generator. The interior of the reservoir is maintained under pressure to force a flow of liquid target material from the reservoir to the droplet generator.

[0007] As mentioned, tin is one suitable choice for a target material. Hot molten tin, however, is extremely corrosive. Thus, components of the tin storage and delivery system are conventionally made of a material that can withstand prolonged exposure to molten tin under pressure. Molybdenum (Mo) is a relatively strong material that resists corrosion from exposure to molten tin which recommends it as a choice for a material this application.

[0008] High EUV power at high repetition rates drives requirements for higher speed droplets with a large space between droplets. Acceleration of the droplets generated by a droplet generator has been achieved in the past by increasing the driving gas pressure. Currently, pressures on the order of 4000 psi (270 bar) are used to achieve droplet velocities of about 80 m / sec. Future EUV designs will call for much higher droplet velocities requiring drive pressures of up to 20305 psi (1400 bar) to achieve . The need to employ these higher pressures in turn drives a need to use materials that exhibit more tensile strength than a material such as pure molybdenum.

[0009] It is in this context that the need for and advantages of the presently disclosed subject matter arise.SUMMARY

[0010] The following is a concise summary providing a basic understanding of the embodiments. This summary is not intended to be a comprehensive overview of all contemplated embodiments nor is it intended to identify as key or critical any elements of any embodiments. Its sole purpose is to present some concepts relating to one or more embodiments as a prelude to the more detailed description that is presented further below.

[0011] According to an aspect of an embodiment there may be disclosed a target material storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the target material storage and delivery system comprising a fdter arranged so that target material passes through the fdter while passing through the target material storage and delivery system, the fdter comprising a fdter housing, the fdter housing comprising an alloy of a first refractory metal and a second refractory metal.

[0012] The first refractory metal may be rhenium. A weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight. The second refractory metal may be molybdenum.

[0013] A weight percentage of the rhenium in the alloy may be in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities. A weight percentage of the rhenium in the alloy may be about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

[0014] The second refractory metal may be tantalum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities. The weight percentage of the rhenium in the alloy maybe about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

[0015] According to another aspect of an embodiment there is disclosed a molten tin storage and delivery system comprising at least one component which comes into contact with pressurized molten tin, the at least one component comprising an alloy consisting of a first refractory metal and a second refractory metal.

[0016] The first refractory metal may be rhenium. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight. The second refractory metal may be molybdenum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

[0017] The second refractory metal may be tantalum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

[0018] According to another aspect of an embodiment there is disclosed a source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising a vacuum chamber, collector optics arranged within the vacuum chamber and to have a focus within the chamber, and a target material storage and delivery system arranged to dispense droplets of a target material to an irradiation site within the chamber at the focus, the target material storage and delivery system comprising a filter arranged so that target material passes through the filter while passing through the target material storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

[0019] The first refractory metal may be rhenium. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight. The second refractory metal may be molybdenum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

[0020] The second refractory metal may be tantalum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

[0021] According to another aspect of an embodiment there is disclosed a filter for a targetmaterial storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the filter housing comprising an alloy of a first refractory metal and a second refractory metal. The first refractory metal may be rhenium. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight. The second refractory metal may be molybdenum. The weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

[0022] The second refractory metal may be tantalum. The filter weight percentage of the rhenium in the alloy may be in the range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities. The weight percentage of the rhenium in the alloy may be about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

[0023] According to another aspect of an embodiment there is disclosed a source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising a vacuum chamber and a tin storage and delivery system arranged to dispense droplets of a molten tin to an irradiation site within the chamber, the tin storage and delivery system comprising a filter arranged so that the filter removes particulate contaminants from molten tin passing through the tin storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

[0024] Further embodiments, features, and advantages of the subject matter of the present disclosure, as well as the structure and operation of various embodiments, are described in detail below with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the presently disclosed subject matter and, together with the description, further serve to explain the principles of the presently disclosed subject matter and to enable a person skilled in the relevant art(s) to make and use the presently disclosed subject matter.

[0026] FIG. 1 is a partially schematic functional block diagram of an overall broad conception for a laser-produced plasma EUV radiation source such as might incorporate an aspect of an embodiment.

[0027] FIG. 2 is a schematic cross-sectional diagram of an exemplary target material supply apparatus as might be used in the EUV radiation source of FIG. 1.

[0028] FIG. 3 is a cross section of a target material filter in accordance with an aspect of an embodiment.

[0029] FIG. 4 is a schematic cross-sectional diagram of structure around a capillary nozzlehaving a filter in a system in accordance with an aspect of an embodiment.

[0030] Further features and advantages of the disclosed apparatus, as well as the structure and operation of various embodiments of the disclosed apparatus, are described in detail below with reference to the accompanying drawings. The disclosed apparatus is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art based on the teachings contained herein.DETAILED DESCRIPTION

[0031] Various embodiments are described below with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to promote a thorough understanding of multiple embodiments. It may be evident in some or all instances, however, that any embodiment described below can be practiced without adopting the specific design details described below.

[0032] In the description that follows and in the claims the terms “up,” “down,” “upper,”“lower,” “top,” “bottom,” “vertical,” “horizontal,” and like terms may be employed. These terms are intended to show relative orientation only and not any absolute orientation such as orientation with respect to gravity unless otherwise indicated or clear from context.

[0033] FIG. 1 is a schematic diagram of an example of an EUV radiation source, e.g., a laser produced plasma EUV radiation source 10. As shown, the EUV radiation source 10 may include a pulsed or continuous laser source 15, which may, for example, be a pulsed gas discharge CO2 laser source producing a beam 17 of pulses of radiation at a wavelength generally below 20 pm, for example, in the range of about 11 pm to about 9 pm or less. The pulsed gas discharge CO2 laser source may have DC or RF excitation operating at high power and at a high pulse repetition rate.

[0034] The EUV radiation source 10 also includes a target material delivery system 20 for delivering target material in the form of liquid droplets or a continuous liquid stream. In this example, the target material is a liquid, but it could also be a solid. The target material may be made up of tin or a tin compound, although other materials could be used. In the system depicted the target material delivery system 20 introduces droplets 25 of the target material into the interior of a vacuum chamber 30 to an irradiation region 32 where the droplets 25 may be irradiated to produce plasma. It should be noted that as used herein an irradiation region is a region where target material irradiation is to occur and is an irradiation region even at times when no irradiation is actually occurring. The EUV light source 10 also includes a beam focusing and steering system 35.

[0035] In the example shown, the components are arranged so that the droplets 25 travel substantially horizontally with respect to gravity. The direction from the laser source 15 towards the irradiation region 32, that is, the nominal direction of propagation of the beam 17, may be taken as theZ axis. The path the droplets 25 take from the target material delivery system 20 to the irradiation region 32 may be taken as the X axis. The view of FIG. 1 is thus normal to the XZ plane. While a system in which the droplets 25 travel substantially horizontally is depicted, it will be understood by one having ordinary skill in the art that other arrangements can be used in which the droplets 25 travel at an angle with respect to gravity between and including 90 degrees (horizontal) and 0 degrees (vertical).

[0036] The EUV radiation source 10 may also include an EUV light source controller system40 and a laser firing control system 45 along with the beam steering system 35. The EUV radiation source 10 may also include a detector such as a target position detection system which may include one or more droplet imagers 50 that generate an output indicative of the absolute or relative position of a target droplet, e.g., relative to the irradiation region 32, and provide this output to a target position detection feedback system 55. The target position detection feedback system 55 may use the output of the droplet imager 50 to compute a target position and trajectory, from which a target error can be computed.

[0037] The EUV radiation source 10 as depicted in FIG. 1 also includes a conditioning laser60 for generating a conditioning beam 62. This conditioning beam 62 is made up of pulses that prepare the target for subsequent heating by the main drive pulse. The conditioning pulse can change the shape or distribution of the target. It includes pulses variously referred to as pre-pulses, pedestal pulses, and rarefication pulses. The laser beam steering system 35 is capable of steering the conditioning beam 62 generated by the conditioning laser 60.

[0038] As shown in FIG. 1 , the target material delivery system 20 may include a target delivery control system 70. The target delivery control system 70 is operable in response to a signal, for example, a target error or some quantity derived from the target error provided by the system controller 40, to adjust paths of the targets 25 through the irradiation region 32. This may be accomplished, for example, by repositioning the point at which a target delivery mechanism 72 releases the droplets 25 from a capillary 75. The droplet release point of the capillary 75 may be repositioned, for example, by tilting or shifting the target delivery mechanism 72.

[0039] The target delivery mechanism 72 extends into the chamber 30 and is supplied with target material 26 from a target material reservoir 77. The target material reservoir 77 is in fluid communication with the target delivery mechanism 72 through a reservoir target material outlet valve 78. The reservoir target material outlet valve 78 may be configured as a freeze valve in which the flow of molten tin is controlled by permitting / causing molten tin to solidify in the valve to close the valve and permitting / causing solid tin to melt in the valve to open the valve. The target material reservoir 77 is also in fluid communication with a source of liquid target material through a reservoir target material inlet valve 79. The reservoir target material inlet valve 79 may also be configured as a freeze valve. In some embodiments there may be only a single target material conduit permitting adding target material to and withdrawing target material from the target material reservoir 77 and so serving as both an inlet and an outlet.

[0040] The liquid target material 26 within the target material reservoir 77 is maintained under pressure by a gas supplied from a gas supply (not shown) in fluid communication with the target material reservoir 77 through a reservoir gas inlet valve 71.

[0041] It will be understood that the EUV radiation source 10 may include more than one target material reservoir 77. The liquid target material 26 within the target material reservoir 77 may be produced by any one of several methods generally involving melting pure solid tin.

[0042] More details regarding various droplet dispenser configurations may be found for example in U.S. Pat. No. 7,872,245, issued on January 18, 2011, titled “Systems and Methods for Target Material Delivery in a Laser Produced Plasma EUV Light Source”, U.S. Pat. No. 7,405,416, issued on July 29, 2008, titled “Method and Apparatus for EUV Plasma Source Target Delivery”, and U.S. Pat. No. 7,372,056, issued on May 13, 2008, titled “LPP EUV Plasma Source Material Target Delivery System.”

[0043] All patent applications, patents, and printed publications cited herein are incorporated herein by reference in their entireties, except for any definitions, subject matter disclaimers, or disavowals, and except to the extent that the incorporated material is inconsistent with the express disclosure herein, in which case the language in this disclosure controls.

[0044] The arrangement of FIG. 1 also includes one or more filters 80, 85 which block particulates which may be entrained in the molten target material and which would otherwise clog the capillary 75. As shown, one filter 80 may be positioned within the target delivery mechanism 72 just upstream of the capillary 75. Another filter 85 may be positioned, for example, between the target delivery mechanism 72 and the target material reservoir 77. These filters may have a porous filter element made, for example, out of sintered tungsten. Details regarding the filters may be found for example in U.S. Pat. No. 9,029,813, issued on May 12, 2015, and titled “Filter for Material Supply Apparatus of an Extreme Ultraviolet Light Source.”

[0045] The target material delivery system 20 (including target delivery control system 70, the target delivery mechanism 72, the capillary 75, and the filter 80), the target material reservoir 77, the filter 85, and the valves 71, 78, and 79 may be regarded as a target material storage and delivery system 95. The target material storage and delivery system 95 may also include a second reservoir if one is used. The components of the target material storage and delivery system 95 will in general be exposed to molten target material maintained at a high pressure.

[0046] The EUV radiation source 10 also includes a target material catch 87 that catches and retains target material which has not been converted through irradiation to limit contamination from such unconverted target material.

[0047] Continuing with FIG. 1, the EUV radiation source 10 may also include one or more optical elements. A collector 36 is shown as an example of such an optical element, but the description applies to other types of optical elements as well. The collector 36 may be a normal incidence reflector, for example, implemented as a multilayer mirror with additional thin barrier layers, for example EEC,ZrC, SisN or C, deposited at each layer interface to effectively block thermally induced interlayer diffusion. The collector 36 may be in the form of a prolate ellipsoid, with a central aperture to allow the beam 17 and conditioning beam 62 to pass through and reach the irradiation region 32. The collector 36 may have a first focus at the irradiation region 32 and a second focus at an intermediate point 38 (also called the intermediate focus 38) where the EUV radiation may be output from the EUV radiation source 10 and input to, e.g., an integrated circuit lithography scanner or stepper 90. The integrated circuit lithography scanner or stepper 90 uses the radiation, for example, to process a silicon wafer workpiece 92 in a known manner using a reticle or mask 94. The silicon wafer workpiece 92 may then be processed additionally in a known manner to obtain an integrated circuit device.

[0048] FIG. 2 is a schematic diagram of a target material storage and delivery system 95 such as that shown in FIG. 1. As can be seen, molten target material 26 is stored in an internal volume 76 of the target material reservoir 77 which is under pressure from a gas introduced into the target material reservoir 77 through the valve 71. The molten target material 26 flows through the valve 78 along a conduit 210 through a filter 85 to reach an internal volume 73 of the target delivery mechanism 72. The molten target material 26 in the internal volume 73 of the target delivery mechanism 72 passes through a filter 80 and then through a capillary 25 to create droplets 25 in chamber 30. It will be appreciated by one of ordinary skill in the art that the filter 85 is not necessarily included in an arrangement such as that shown in FIG. 2. In a system in which the droplets travel horizontally so that the capillary 75 is not pointed gravitationally downward it will be understood that the molten target material 26 in the internal volume 76 of the target material reservoir 77 and in the internal volume 73 of the target delivery mechanism 72 will not necessarily partially fill those volumes as shown.

[0049] FIG. 3 shows a possible arrangement for a filter 80 according to an aspect of an embodiment. As shown, the filter 80 includes a generally cylindrical filter housing 100 defining a filter housing cavity 110. The filter housing 100 also defines a filter inlet 120 and a filter outlet 130. The filter inlet 120 and the filter outlet 140 are separated by a filter porous element 140 arranged in the filter housing cavity 110. An interior volume of the filter porous element 140 defines a filter porous element cavity 150.

[0050] In use, molten target material enters the filter 80 through the filter inlet 120 and passes into the filter porous element cavity 150. The molten target material then must pass through the filter porous element 140 in order to flow through the filter 80 to the filter outlet 130.

[0051] The filter porous element 140 may be made of a material such as sintered tungsten. The filter porous element 140 may be attached to the filter housing 100 by any suitable mechanical means such as by welding or being joined by mechanical fastenings to make the assembly.

[0052] Some components of the target material storage and delivery system 95 are exposed to pressurized molten target material These include the filter housing 100 which is conventionally made using molybdenum such as molybdenum ASTM B387 Type 361 (molybdenum 361). According to an aspect of an embodiment, one or more components of the target material storage and delivery system95 which are exposed to pressurized molten target material are made of an alloy of refractory metals such as a molybdenum-rhenium alloy to provide greater material strength. These components include various housings such as the fdter housing as well as pressure vessels, reservoirs, tubes, conduits, valves, and fittings. Refractory metals are a group of metallic elements that are highly resistant to heat and wear. They include metals with melting points greater than 2000 °C. Tungsten, (W) molybdenum, niobium (Nb), tantalum (Ta), chromium (Cr), and rhenium (Re) are typical refractory metals. Hafnium (Hf), zirconium (Zr), and iridium (Ir) are also considered to be refractory. As used herein, the term “refractory metal” is used to describe all of these elements.

[0053] One example of such an alloy for making a component such as the filter housing 100 is a molybdenum rhenium (MoRe) alloy. MoRe is compatible with the molten target material when the target material is tin. Mo-Re is substantially stronger (has substantially greater tensile strength) than an unalloyed molybdenum material such as molybdenum 361. Molybdenum 361, for example, for example, has a tensile strength of around 360 MPa at 300 °C versus a MoRe alloy having 52.5% by weight Mo and 47.5% by weight Re (Mo-47.5 Re) which has tensile strength of around 630 MPa at 300 °C.

[0054] The use of MoRe will thus facilitate scaling up to operating with liquid tin at pressures of 1400 bar. At the same time the use of MoRe permits the construction of components having more compact sizes that fit within the allotted dimensions of existing target material storage and delivery systems. In other words, a cylindrical filter designed to handle 1400 bar pressure fabricated from molybdenum 361 would need to have an external diameter greater than 60 mm while a filter designed to handle 1400 bar pressure fabricated from MoRe could have an external diameter of only about 30 mm. In addition, including rhenium in the molybdenum alloy improves weldability and robustness of the end product. Alloying a material such as rhenium with molybdenum can allow for the fabrication of a more robust product as compared to fabrication using unalloyed molybdenum. These benefits may be pronounced for products in which fabrication of the product includes welding.

[0055] The relative proportions of Mo and Re in the alloy may be varied. The composition having 52.5% by weight Mo and 47.5% by weight Re (Mo-47.5 Re) mentioned above is readily available because it is manufactured as a standard alloy. A composition of 55% by weight Mo and 45% by weight for Re (Mo-45 Re) is also readily available. Another possibility is a composition having 55.5% by weight Mo and 44.5% by weight Re (Mo-44.5 Re). In general, the rhenium content of MoRe alloys is preferably in a range of about 5% by weight to about 50% by weight Re with the remainder being Mo besides normally present or inevitable impurities. As used in this description and in the appended claims, the term “about” means equal to the stated quantity plus or minus standard tolerances, e.g., + / - 5% of the stated quantity.

[0056] Refractory metals other than molybdenum such as tantalum may be alloyed with rhenium to make TaRe. As with molybdenum, various relative proportions of these components may be used to make the alloys including 97% by weight Ta and 3% by weight Re (Ta-3 Re). Tungsten mayalso be used as the primary component to make, e.g., an alloy having 75% by weight W and 25% by weight Re (W -25 Re). As with molybdenum, the rhenium content of these alloys is preferably in a range of about 5% by weight to about 50% by weight Re with the remainder being tantalum or tungsten, respectively, besides inevitable impurities.

[0057] It is also possible to use alloys of two refractory metals neither of which is rhenium such as tantalum-tungsten. It is also possible to use molybdenum alloys which contain a second refractory metal such as hafnium and carbon, such as molybdenum hafnium carbide alloy which is a particle-reinforced molybdenum alloy which contains hafnium and carbon, for example, in the proportions 0.8-1 .4% hafnium and 0.05-0.15% carbon, remainder hafnium.

[0058] In some embodiments the alloy is pure. Here and elsewhere in this specification the term “pure” is intended to connote so-called “three nines” purity, i.e., 99.9% purity by weight. It will be understood that other materials may be present at or below 0.010 weight percent as well as inevitable impurities. As used herein, the term “alloy” connotes a material made up of at least two metallic constituents that have been purposefully combined to obtain an end material having one or more altered material properties.

[0059] In accordance with an aspect of an embodiment, at least some components of the target material storage and delivery system exposed to high pressure molten target material and made of one of the alloys described above are fabricated so that the material properties of the alloy are substantially isotropic, e.g., made using a powder metallurgy process, specifically, a hot isostatically pressed (HIP) process that results in the alloy being isotropic. Here and elsewhere in this specification the terms “isotropic” and “substantially isotropic” mean that the alloy’s physical properties are the same, regardless of the direction in which they are determined (axially, transversely, etc.), within + / - 5%.

[0060] HIP is a materials fabrication process in which a starting powder or a premolded shape is simultaneously subjected to both high temperatures and high isostatic pressures. The gas pressure is referred to as being isostatic because it is uniformly applied in all directions. HIP can combine high temperature (e.g., up to and exceeding 2200 °C) and a high isostatic gas pressure ( e.g., in a range of 200-500 MPa). The HIP process does not cause any forming-process induced deformation and so can be used to produce an isotropic alloy.

[0061] As an example of a component of a target material storage and delivery system which can advantageously be made of the alloys described above, FIG. 4 shows a nozzle assembly portion 200 of target delivery mechanism 72 in accordance with certain aspects of an embodiment. A nozzle nut 210 attaches a ferrule 215 to a nozzle body 220. The nozzle cavity 235, which corresponds to or is in fluid communication with the internal volume 73 of target delivery mechanism 72, retains liquid target material under pressure. Liquid target material flows down the capillary 75 and out of a nozzle 225. A piezoelectric element 230 mechanically coupled to the capillary 75 introduces perturbations in the flow of liquid target material exiting the nozzle 225 in a known manner. Also shown is a fdter 80 arranged just upstream of the capillary 75 to prevent the passage of particulate contaminants in thenozzle cavity 235 from reaching the capillary 75 and potentially clogging the nozzle 225.

[0062] The present disclosure is made with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein to promote clear description. Alternate boundaries can be defined so long as the specified functions are appropriately performed. For example, control module functions can be divided among several systems or performed at least in part by an overall control system.

[0063] The above description includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the aforementioned embodiments, but one of ordinary skill in the art after being supplied with this disclosure will recognize that many further combinations and permutations of various embodiments are possible. Accordingly, the described embodiments are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is construed when employed as a transitional word in a claim. Furthermore, although elements of the described aspects and / or embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated or clear from context. Additionally, all or a portion of any aspect and / or embodiment may be utilized with all or a portion of any other aspect and / or embodiment, unless stated otherwise.

[0064] The embodiments can be further described using the following clauses:1. A target material storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the target material storage and delivery system comprising a filter arranged so that target material passes through the filter while passing through the target material storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.2. The target material storage and delivery system of clause 1 wherein the first refractory metal is rhenium.3. The target material storage and delivery system of clause 2 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.4. The target material storage and delivery system of clause 2 wherein the second refractory metal is molybdenum.5. The target material storage and delivery system of clause 4 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.6. The target material storage and delivery system of clause 5 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.7. The target material storage and delivery system of clause 2 wherein the second refractory metal is tantalum.8. The target material storage and delivery system of clause 7 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.9. The target material storage and delivery system of clause 8 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.10. A molten tin storage and delivery system comprising at least one component which comes into contact with pressurized molten tin, the at least one component comprising an alloy consisting of a first refractory metal and a second refractory metal.11. The molten tin storage and delivery system of clause 10 wherein the first refractory metal is rhenium.12. The molten tin storage and delivery system of clause 11 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.13. The molten tin storage and delivery system of clause 11 wherein the second refractory metal is molybdenum.14. The molten tin storage and delivery system of clause 13 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.15. The molten tin storage and delivery system of clause 14 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.16. The molten tin storage and delivery system of clause 11 wherein the second refractory metal is tantalum.17. The molten tin storage and delivery system of clause 16 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.18. The molten tin storage and delivery system of clause 17 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.19. A source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising: a vacuum chamber;collector optics arranged within the vacuum chamber and to have a focus within the chamber; and a target material storage and delivery system arranged to dispense droplets of a target material to an irradiation site within the chamber at the focus, the target material storage and delivery system comprising a fdter arranged so that target material passes through the filter while passing through the target material storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.20. The source of clause 19 wherein the first refractory metal is rhenium.21. The source of clause 20 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.22. The source of clause 21 wherein the second refractory metal is molybdenum.23. The source of clause 22 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.24. The source of clause 23 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.25. The source of clause 20 wherein the second refractory metal is tantalum.26. The source of clause 25 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.27. The source of clause 26 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.28. A filter for a target material storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.29. The filter of clause 28 wherein the first refractory metal is rhenium.30. The filter of clause 29 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.31. The filter of clause 29 wherein the second refractory metal is molybdenum.32. The filter of clause 31 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.33. The filter of clause 32 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.34. The filter of clause 29 wherein the second refractory metal is tantalum.35. The filter of clause 34 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.36. The filter of clause 35 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.37. A source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising: a vacuum chamber; and a tin storage and delivery system arranged to dispense droplets of a molten tin to an irradiation site within the chamber, the tin storage and delivery system comprising a filter arranged so that the filter removes particulate contaminants from molten tin passing through the tin storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

[0065] The above described implementations and other implementations are within the scope of the following claims.

Claims

CLAIMS1. A target material storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the target material storage and delivery system comprising a filter arranged so that target material passes through the filter while passing through the target material storage and delivery system, the fdter comprising a fdter housing, the fdter housing comprising an alloy of a first refractory metal and a second refractory metal.

2. The target material storage and delivery system of claim 1 wherein the first refractory metal is rhenium.

3. The target material storage and delivery system of claim 2 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.

4. The target material storage and delivery system of claim 2 wherein the second refractory metal is molybdenum.

5. The target material storage and delivery system of claim 4 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.

6. The target material storage and delivery system of claim 5 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

7. The target material storage and delivery system of claim 2 wherein the second refractory metal is tantalum.

8. The target material storage and delivery system of claim 7 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.

9. The target material storage and delivery system of claim 8 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

10. A molten tin storage and delivery system comprising at least one component which comes into contact with pressurized molten tin, the at least one component comprising an alloy consisting of a first refractory metal and a second refractory metal.

11. The molten tin storage and delivery system of claim 10 wherein the first refractory metal is rhenium.

12. The molten tin storage and delivery system of claim 11 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.

13. The molten tin storage and delivery system of claim 11 wherein the second refractory metal is molybdenum.

14. The molten tin storage and delivery system of claim 13 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.

15. The molten tin storage and delivery system of claim 14 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

16. The molten tin storage and delivery system of claim 11 wherein the second refractory metal is tantalum.

17. The molten tin storage and delivery system of claim 16 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.

18. The molten tin storage and delivery system of claim 17 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

19. A source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising: a vacuum chamber; collector optics arranged within the vacuum chamber and to have a focus within the chamber; anda target material storage and delivery system arranged to dispense droplets of a target material to an irradiation site within the chamber at the focus, the target material storage and delivery system comprising a filter arranged so that target material passes through the filter while passing through the target material storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

20. The source of claim 19 wherein the first refractory metal is rhenium.

21. The source of claim 20 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.

22. The source of claim 21 wherein the second refractory metal is molybdenum.

23. The source of claim 22 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.

24. The source of claim 23 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

25. The source of claim 20 wherein the second refractory metal is tantalum.

26. The source of claim 25 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.

27. The source of claim 26 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

28. A filter for a target material storage and delivery system adapted to deliver a target material to an irradiation site in an extreme ultraviolet radiation source, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

29. The filter of claim 28 wherein the first refractory metal is rhenium.

30. The filter of claim 29 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight.

31. The filter of claim 29 wherein the second refractory metal is molybdenum.

32. The filter of claim 31 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being molybdenum besides normally present impurities.

33. The filter of claim 32 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight with the remainder being molybdenum besides normally present impurities.

34. The filter of claim 29 wherein the second refractory metal is tantalum.

35. The filter of claim 34 wherein a weight percentage of the rhenium in the alloy is in a range of 5% by weight to about 50% by weight with a remainder being tantalum besides normally present impurities.

36. The filter of claim 35 wherein a weight percentage of the rhenium in the alloy is about 47.5% by weight by weight with the remainder being tantalum besides normally present impurities.

37. A source of extreme ultraviolet radiation for semiconductor photolithography, the source comprising: a vacuum chamber; and a tin storage and delivery system arranged to dispense droplets of a molten tin to an irradiation site within the chamber, the tin storage and delivery system comprising a filter arranged so that the filter removes particulate contaminants from molten tin passing through the tin storage and delivery system, the filter comprising a filter housing, the filter housing comprising an alloy of a first refractory metal and a second refractory metal.

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