Systems and methods for target material waste management in EUV light sources

Abstract

Systems and methods for managing target material waste in EUV light sources are disclosed. An apparatus associated with a radiation source may include a reservoir connected with a target material catch of the radiation source through a conduit, a valve associated with the reservoir and configured to be movable within a volume of the reservoir, and a first container placed on a horizontal surface of the valve at a first location, wherein in an extended position, the valve is configured to separate the volume of the reservoir in a first space and a second space, and wherein in the extended position, the first container is configured to be aligned with the conduit to collect target material.

Description

SYSTEMS AND METHODS FOR TARGET MATERIAL WASTE MANAGEMENT IN EUV LIGHT SOURCESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to US Application No. 63 / 738,209, filed December 23, 2024, titled SYSTEMS AND METHODS FOR TARGET MATERIAL WASTE MANAGEMENT IN EUV LIGHT SOURCES, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The embodiments provided herein generally relate to extreme ultraviolet (“EUV”) light sources and their methods of operation in semiconductor device fabrication processes, and more particularly, to systems and methods for managing target material waste in EUV light sources.BACKGROUND

[0003] Light generated by means of a radiation source can be used by exposure apparatuses for semiconductor manufacturing processes. Examples of such exposure apparatuses are a lithographic apparatus, a metrology, or an inspection apparatus, more specifically a wafer inspection apparatus, a dimension measurement apparatus, a mask inspection apparatus and even more specifically an actinic mask inspection apparatus.

[0004] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (e.g., a photoresist or resist) provided on a substrate. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. A lithographic apparatus, which uses EUV radiation, having a wavelength within the range 4-20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm.

[0005] A mask inspection apparatus (e.g., actinic mask inspection apparatus) is an apparatus that is configured for measuring dimensions or detecting defects in masks or mask blanks. EUV lithography uses reflective surfaces instead of a lenses as optics. Mask blanks used in EUV lithography generally have a multilayer structure which functions as a Bragg reflector, the multilayers may be altematingly molybdenum and silicon. If a defect exists in this structure, the projected pattern will be deformed in the lithographic process. Therefore, mask inspection to check whether a defect is present is considered a requirement for a mass-production process. EUV mask inspection may be used for several purposes and in several different stages. Firstly, it can be used for the detection of phase defects that may occur in mask blanks. Such phase defects may occur during the manufacturing of the multilayer stack of themask blank. If undetected, these phase defects are printed on all chips printed with the part of a mask containing the phase defects. Such phase defects may be correctly detected by using the same or similar actinic EUV wavelength (13.5 run) as the lithography tool. Secondly, mask inspection can be used for patterned mask inspection and can be carried out for the quality control of EUV patterned masks. For example, the mask inspection can be used to measure critical dimensions on the mask blank. In addition to phase defects, absorber pattern defects on the surface can be detected. Thirdly, mask inspection can be used for simulating exposure and determining the deterioration of optical contrast of a defect detected in the actinic inspection. Fourthly, the mask inspection can be used for optical proximity correction (OPC) evaluation or during mask repair process so as to improve pattern transfer fidelity. Further, it can be used for inspecting optical contrast after fixing the defect. In addition to the above, mask inspection can also be used to measure small particle / amplitude effects.

[0006] A metrology apparatus is an apparatus that measures critical dimension and inspect various aspects of the wafer during the semiconductor manufacturing process. A metrology apparatus can also measure and characterize physical properties of materials and components. The metrology apparatus is a precision instrument that ensures product quality and process control. In at least one embodiment, the metrology apparatus employs EUV radiation to inspect and measure dimensions of targets on the substrate.

[0007] An EUV radiation source configured for use in lithography (e.g., photolithography) apparatus or in a mask inspection apparatus may have a variety of desirable characteristics, such as high output power, high conversion efficiency, high spectral purity, among other features. The conversion efficiency, generally referred to as a fraction of the input energy to the EUV source that is converted to EUV radiation energy, may be used to determine the utility requirements, to select a target material, or to understand the limits of power scaling. In lithography and mask inspection apparatuses used for semiconductor device fabrication, maximizing EUV source output power and the source stability are of particular interest.SUMMARY

[0008] Some embodiments of the present disclosure provide systems and methods for tin waste management in EUV light sources. An apparatus associated with a radiation source may include a reservoir connected with a target material catch of the radiation source through a conduit, a valve associated with the reservoir and configured to be movable within a volume of the reservoir, and a first container placed on a horizontal surface of the valve at a first location, wherein in an extended position, the valve is configured to separate the volume of the reservoir in a first space and a second space, and wherein in the extended position, the first container is configured to be aligned with the conduit to collect target material.

[0009] Some embodiments of the present disclosure are directed to a method for managing target material associated with operation of a radiation source. The method comprises directing a plurality ofdroplets of target material into a reservoir through a conduit; and adjusting a position of a valve within a volume of the reservoir based on an operation mode of the radiation source, the operating mode comprising a production mode and a service mode, wherein operating in the production mode comprises positioning the valve in a retracted position to enable the plurality of droplets of target material into a receptacle placed within the volume of the reservoir, and wherein operating in the service mode comprises: positioning the valve in an extended position to separate the volume of the reservoir into a first space and a second space, and collecting the plurality of droplets of target material into a container disposed at a first location on a horizontal surface of the valve.

[0010] Some embodiments of the present disclosure are directed to an apparatus associated with a radiation source. The apparatus may include a reservoir connected with a target material catch of the radiation source through a conduit; a valve associated with the reservoir and configured to be movable within a volume of the reservoir in an open position and in a closed position, wherein in the closed position, the valve is configured to separate the volume of the reservoir in a first space and a second space; and a container disposed in the first space between the valve and the conduit and configured to be movable to align with the conduit to capture target material dripping from the target material catch into the volume of the reservoir.BRIEF DESCRIPTION OF FIGURES

[0011] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.

[0012] Fig. 1 illustrates a schematic block diagram of a lithography system comprising an EUV radiation source and a lithographic apparatus, consistent with embodiments of the present disclosure .

[0013] Fig. 2 illustrates an exemplary mask inspection apparatus used in combination with an EUV radiation source, consistent with embodiments of the present disclosure.

[0014] Fig. 3 illustrates a schematic diagram of an exemplary alternative EUV radiation source, consistent with embodiments of the present disclosure.

[0015] Fig. 4 illustrates a simplified schematic of an exemplary laser produced plasma (LPP) EUV radiation source, consistent with embodiments of the present disclosure.

[0016] Fig. 5A illustrates a simplified schematic of an exemplary target-material waste management apparatus in normal operation mode, consistent with embodiments of the present disclosure.

[0017] Fig. 5B illustrates a simplified schematic of the exemplary target-material waste management apparatus of Fig. 5A in service mode, consistent with embodiments of the present disclosure.

[0018] Fig. 5C illustrates a simplified schematic of the exemplary target-material waste management apparatus of Fig. 5A in service mode, consistent with embodiments of the present disclosure.

[0019] Fig. 5D illustrates a simplified schematic of the exemplary target-material waste management apparatus of Fig. 5A in normal operation mode following the service, consistent with embodiments of the present disclosure.

[0020] Fig. 6A illustrates a simplified schematic of an exemplary target-material waste management apparatus, consistent with embodiments of the present disclosure.

[0021] Fig. 6B illustrates a simplified schematic of an exemplary target-material waste management apparatus comprising a heated service container, consistent with embodiments of the present disclosure.

[0022] Fig. 7 illustrates a simplified schematic of an exemplary target-material waste management apparatus, consistent with embodiments of the present disclosure.

[0023] Fig. 8 illustrates a process flowchart of an exemplary method for managing waste associated with operation of a fuel-based radiation source, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0024] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings, the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments are described. As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component may include A or B, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or A and B. As a second example, if it is stated that a component may include A, B, or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0025] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings in which the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments as recited in the appended claims.

[0026] Manufacturing semiconductor devices typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, photolithography, etch, chemical -mechanical polishing, and ion implantation. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. Photolithography is a process of transferring a pattern to a radiation-sensitive material arranged on a substrate by exposing the substrate to radiation through a mask or a reticle defining the pattern. The substrate may be a silicon (Si) wafer coated with a radiation-sensitive material (e.g., a photoresist). The radiation used in a lithographic apparatus, for advanced technology nodes, may beEUV radiation having a wavelength in the range of 4-20 nm, for example, 13.5 nm. Generally, the shorter the wavelength of the radiation used to expose the photosensitive material, the better the resolution, and therefore, much smaller features can be produced on the substrate using EUV radiation.

[0027] Methods to produce the desirable 13.5 nm EUV radiation include, but are not necessarily limited to, converting a material into a plasma state that has an element, e.g., xenon (Xe), lithium (Li), or tin (Sn), with one or more emission line in the EUV range. In one such method, often termed laser-produced plasma (“LPP”), the required plasma can be produced by irradiating a target material, such as a droplet, stream or cluster of material having the required line -emitting element, with an optical beam, such as a laser beam.

[0028] Although specific reference may be made in this disclosure to the manufacture of ICs, it should be explicitly understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. In the context of this disclosure, any use of the terms “reticle” and “wafer” should be considered as interchangeable with the more general terms “mask” and “substrate,” respectively.

[0029] As used herein, the term “optic” and its derivatives include, but are not necessarily limited to, components which reflect, or transmit, or operate on incident light and includes, but is not limited to, lenses, windows, filters, wedges, prisms, grisms, gratings, etalons, diffusers, transmission fibers, detectors and other instrument components, apertures, stops and mirrors including multi-layer mirrors, near-normal incidence mirrors, grazing incidence mirrors, specular reflectors and diffuse reflectors. Moreover, as used herein, the term “optic” and its derivatives are not meant to be limited to components which operate solely or to advantage within one or more specific wavelength range(s) such as at the EUV output light wavelength, the irradiation laser wavelength, a wavelength suitable for metrology or some other wavelength.

[0030] Although specific reference may be made in this disclosure to a lithographic apparatus, it should be explicitly understood that the description herein may be used in other apparatuses including, but not limited to, a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrates) or mask (or other patterning devices). These apparatuses may be generally referred to as lithographic tools. Such a lithographic tool may use vacuum conditions or ambient (non -vacuum) conditions.

[0031] Although specific reference may be made in this disclosure in the context of optical lithography, it will be appreciated that the disclosure, where the context allows, is not limited to optical lithography and may be used in other applications, for example imprint lithography.

[0032] Where the context allows, embodiments of the disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executedby one or more processors. A machine -readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine -readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical, and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc., and in doing that may cause actuators or other devices to interact with the physical world.

[0033] Fig. 1 is a schematic block diagram of a lithography system comprising a radiation source and a lithographic apparatus, consistent with embodiments of the present disclosure. A lithography apparatus or a lithography system is an apparatus that applies a desired pattern onto a target portion of a substrate such as a silicon wafer. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS and a substrate table WT configured to support a substrate W. Although not illustrated, lithography apparatus may further include a processor, a preprocessor, a microprocessor, or the like, to process obtained data, for example.

[0034] The illumination system IL is configured to condition the EUV radiation beam B before the EUV radiation beam B is incident upon the patterning device MA. Thereto, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The illumination system IL may include other mirrors or devices in addition to, or instead of, the faceted field mirror device 10 and faceted pupil mirror device 11.

[0035] After being thus conditioned, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For that purpose, the projection system PS may comprise a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thus forming an image with features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only two mirrors 13, 14 in Fig. 1, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0036] The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus LA aligns the image, formed by the patterned EUV radiation beam B', with a pattern previously formed on the substrate W. A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL, or in the projection system PS.

[0037] The lithographic apparatus LA and radiation source SO described herein can be used in a method for performing a circuit layout patterning process. A circuit layout patterning method may comprise receiving a substrate with a disposed photoresist layer. The method may further comprise directing EUV radiation from radiation source SO to the photoresist layer to form a patterned photoresist layer. The method may further comprise developing and etching the patterned photoresist layer to form the desired circuit layout.

[0038] Reference is now made to Fig. 2, which illustrates an exemplary mask inspection apparatus, consistent with embodiments of the present disclosure. Mask inspection apparatus, also referred to herein as mask inspection system 200 may be to identify or inspect defects in a mask to be used in a lithographic process by means of lithographic apparatus LA, described in Fig. 1. The mask inspection system may comprise a radiation source 210 (e.g., an EUV radiation source SO of Fig. 1), an illumination system 220, and a detection system 230. A mask 240 may be placed on a mask stage 250 and illuminated by the illumination system 220 reflecting radiation incident from radiation source 210. The radiation coming from the illuminated mask 240 may be reflected by detection system 230 to form an image on a detector 260.

[0039] Referring back to Fig. 1, radiation source SO may be a LPP EUV radiation source. A laser system 1, which may, for example, include one or more drive lasers, are arranged to deposit energy via a laser beam 2 into a target material, also referred to herein as a fuel material. An exemplary target material includes tin (Sn), which is provided from a target droplet generator or a fuel generator 3. Although Sn is referred to in the following description, any suitable fuel material may be used. The target material may, for example, be in liquid form, and may, for example, be a metal or an alloy. The fuel generator 3 may comprise a nozzle configured to direct the fuel, e.g., in the form of droplets, along a trajectory towards a plasma formation region 4. The laser beam 2 is incident upon the fuel droplet(s) at the plasma formation region 4. The deposition of laser energy into target material (e.g., tin droplets) creates a plasma 7 at the plasma formation region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during de-excitation and recombination of electrons with ions of the plasma 7.

[0040] In some embodiments, laser system 1 may be spatially separated from the radiation source SO. Where this is the case, laser beam 2 may be passed from laser system 1 to radiation source SO with the aid of a beam delivery system (not shown) comprising, for example, suitable directing mirrors, or a beam expander, or other suitable optics. In some embodiments, laser system 1, radiation source SO, and the beam delivery system may together be considered to form a radiation system.

[0041] The EUV radiation from plasma 7 is collected and focused by a collector mirror 5. Collector mirror 5 may comprise, for example, a near-normal incidence radiation collector mirror 5, also referred to as a normal -incidence radiation collector. Collector mirror 5 may have a multilayer mirror structure which is arranged to reflect EUV radiation (e.g., EUV radiation having a wavelength of 13.5 nm). The collector mirror 5 may have an ellipsoidal configuration, having two focal points. A first one of the focal points may be at the plasma formation region 4, and a second one of the focal points may be at an intermediate focus 6, as discussed below.

[0042] Radiation that is reflected by collector mirror 5 forms EUV radiation beam B. The EUV radiation beam B may be focused at an intermediate focus 6 to form an image at the intermediate focus 6 of the plasma present at plasma formation region 4. The image at the intermediate focus 6 acts as a virtual radiation source for the illumination system IL. In some embodiments, radiation source SO may be arranged such that the intermediate focus 6 is located at or near to an opening 8 in an enclosing structure 9 of the radiation source SO.

[0043] It should be appreciated that although radiation source SO is discussed herein as a LPP EUV source, any suitable source such as a free electron laser (FEL) or a discharge produced plasma (DPP) source may be used to generate EUV radiation.

[0044] Reference is now made to Fig. 3, which illustrates a schematic diagram of an exemplary alternative EUV radiation source, consistent with embodiments of the present disclosure. For generating plasma, target material 360 (e.g., Sn, Xe, or an alloy) may be provided to a rotating element 320 such as, but not limited to, rotating wheels, cylinder, or a drum, or variations thereof. In some embodiments, target material 360 may be provided via target material source 330 in liquified form to the rotating element 320, such as by means of a target material bath. Alternatively, target material may also be provided in solid or frozen form (e.g., Xe, Li, or Sn metal). In some embodiments, target material may be in a gaseous state and may be sprayed onto the rotating element 320 to replenish target material transformed to plasma. In some embodiments, rotating element 320 may be cooled to solidify target material 360.

[0045] Radiation source 300 may further comprise an excitation device 310 configured to assist in plasma formation. In some embodiments, excitation device 310 may comprise a laser source, such as a solid-state laser or a gas laser, directing a laser beam to be incident on target material 360 and form plasma at a plasma formation region 370 (analogous to plasma formation region 4 of Fig. 1). A solid-state laser, as used herein, refers to a laser source which uses a lasing medium that is a solid, for example, a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser or an yttrium-doped yttrium aluminum garnet (Yb:YAG) laser. A gas laser, as used herein, refers to a laser source in which an electric current is discharged through a gas to produce coherent light, for example, a carbon dioxide (CO2) laser, carbon monoxide (CO) laser, helium-neon (HeNe) laser, or a nitrogen (N2) laser.

[0046] Radiation source 300 may include reflective optics configured to reflect the generated EUV radiation to intermediate focus point 342. In some embodiments, the reflective optics may comprise acollector mirror 340, analogous to collector mirror 5 of Fig. 1. EUV radiation of 13.5 nm is absorbed significantly by materials, and even gases, used in a Sn-based LPP EUV radiation source. Therefore, it may be desirable to minimize EUV radiation absorption losses along the optical path in an EUV radiation source to maximize the output of EUV radiation or the conversion efficiency of EUV sources. One of several ways to mitigate absorption losses in an EUV radiation source is to maximize the reflectivity of collector mirror 340. In some embodiments, collector mirror 340 may comprise a multilayered coating of reflective and barrier materials, acting as Bragg reflectors. The multilayered coating may include a silicon-molybdenum (Si / Mo) multilayered stack, for example. Other suitable coatings may be applied as well.

[0047] In some embodiments, buffer gas flow 345 may be provided to mitigate contamination of radiation source 300 and related components from previously existing debris or debris generated in radiation source 300. Collector mirror 340 may be located in close proximity to plasma formation region 370. In addition to EUV radiation, the plasma formed at plasma formation region 370 may emit high-energy ions as well as undesirable tin particles, which may get deposited on the reflective surface of collector mirror 340. Such debris, over a period of time, impairs the reflective coating of collector mirror 340, negatively impacting the optical characteristics, such as reflectivity, and lifetime of collector mirror 340. A buffer gas flow 345 may comprise the flow of a buffer gas, e.g., hydrogen gas, at a suitable pressure range. In some embodiments, the buffer gas flow pressure may be in a range of 50 - 150 Pascals (Pa). The flow of buffer gas may be configured to enable deceleration of atomic tin (unionized) and tin ions approaching the reflective surface of collector mirror 340, and further, to minimize deposition of Sn ions by enabling a chemical reaction between tin particles and hydrogen gas to form gaseous tin hydride (SnH4). The gaseous SnH may be removed from the EUV source vessel (not shown) using a vacuum pump 350. In some embodiments, vacuum pump 350 may be provided to create and maintain a gas pressure below atmospheric pressure inside radiation source 300.

[0048] Commonly used EUV radiation having a wavelength of 13.5 nm is obtained from plasma emissions of highly charged tin ions. It is to be appreciated that while Li, Xe, and tin, all of which have ions with strong resonance transitions within the desirable bandwidth, may be used to generate EUV radiation, the conversion efficiency fortin is higher than that of Xe and Li. Near 13.5 nm wavelength, the EUV spectrum of highly charged tin ions is dominated by intense unresolved transition arrays (UTAs) arising mainly from the resonance transitions. One of several requirements to obtain ~ 20-40 eV plasma temperatures to produce the highly charged tin ions includes high power densities, among other things. This temperature requirement may be understood through the Stefan-Boltzmann law, which describes the energy emitted per second per unit surface by a black body as a function of temperature. Using this relationship, approximately 108Watts (W) may be needed for a sustained emission from a representative emitting area of ~ 1 mm2. The requirement for high powerdensity necessitates plasma sources of a pulsed nature. Some examples of pulsed laser sources may include discharge-produced plasma (DPP), or laser produced plasma (LPP).

[0049] In an exemplary LPP EUV radiation source, a fuel droplet stream (e.g., tin droplets) may be illuminated with a pulsed laser radiation provided by one or more laser sources. To generate EUV radiation, a series of laser pulses are injected so as to intercept each tin droplet of the droplet stream. The tin droplets may change shape upon interaction with the laser pulse although they may still be referred to as droplets or, alternatively, the droplet may be more generally referred to as a tin target or a fuel target. The series of laser pulses may comprise three laser pulses. The LPP EUV radiation source may use (i) a low-energy first laser pulse, also referred to as a pre-pulse (PP), which upon being incident on the fuel droplet (e.g., tin droplet), causes the shape of the fuel droplet to change from a substantially spherical droplet to a flatter, disk-shaped target; (ii) a low-energy second laser pulse, also referred to as a pedestal pulse or a rarefaction pulse (RP), which upon interaction, causes the disk-shaped target to expand to a disperse, rarefied target; and (iii) a high-energy third pulse, also referred to as a main pulse (MP), which upon being incident on the disperse target, causes conversion of at least a portion of the disperse target into plasma at a plasma formation region. The portion of the disperse target converted to plasma can emit radiation, including EUV radiation, during de-excitation and recombination of electrons with ions of the plasma. The fraction of the main pulse energy that is converted to EUV radiation energy may be referred to as the conversion efficiency of the radiation source. The laser pulses may include infrared (IR) radiation, for example, with a wavelength of approximately 10 pm or approximately 1 pm.

[0050] As previously discussed, the laser source providing pulsed laser radiation may comprise a 10 pm laser architecture (e.g., CO2 laser architecture) or a 1 pm laser architecture (e.g., Nd:YAG laser architecture). In a 10 pm laser architecture, the low-energy pre-pulse and the low-energy rarefaction pulse (which may otherwise be called a rarefication pulse) may be generated by a laser source configured to provide a laser beam having a wavelength in a range of 9 pm - 11 pm. On the other hand, in a 1 pm laser architecture, the low-energy pre-pulse and the low-energy rarefaction pulse may be generated by a laser source configured to provide a laser beam having a shorter wavelength of approximately 1 pm. In either laser architectures, the high-energy main pulse may be generated by a laser source configured to provide a laser beam having a wavelength in the range of around 10 pm. It is to be appreciated that the laser wavelength ranges mentioned herein are approximate and may vary within a suitable range.

[0051] With respect to excitation lasers for EUV radiation sources, currently existing systems use one or more high-power CO2 gas laser at 10.6 pm wavelength, or one or more solid-state Nd:YAG laser at 1 pm wavelength. The conversion efficiency, and to some extent, the maximum EUV output power obtainable may depend, among other things, on the electron density of the generated plasma. To improve the conversion efficiency, it may be desirable that the electron density of the plasma formed by the fuel target irradiated by the main pulse of laser radiation is as close to, but not less than,the critical plasma density. Critical plasma density, as used herein, refers to the density of electrons in a plasma formed by irradiation of the fuel material by a laser radiation at which the plasma frequency equals the frequency of an electromagnetic electron wave in the plasma. The critical plasma density of a plasma is governed by the following equation:where s0is the permittivity of free space, meis the mass of an electron, a»Lis the angular frequency of the incident laser radiation, and e is the charge of an electron.

[0052] As an example, the critical density of electrons at the desirable 20 - 40 eV temperature range for incident radiation with a wavelength of ~1 pm (e.g., generated by a Nd:YAG laser source) would be approximately 1021cm'3and the critical density of electrons in plasma generated by an incident radiation with a wavelength of -10.6 pm (e.g., generated by a CO2 laser source) would be approximately 1019cm'3. The electron density of solid or liquid atomic tin is in the range of 1022-1023cm'3. As the fuel target is irradiated by the main pulse of the laser radiation, and as the fuel target emits EUV radiation as a result of the irradiation, the electron density of the plasma formed from the fuel target by the radiation decreases. Such a decrease in the electron density of the plasma may cause the electron density of the plasma relevant for the absorption of laser radiation to drop below the critical plasma density, thus negatively impacting the conversion efficiency of the laser source and increasing the reflectance of the plasma.

[0053] Reference is now made to Fig. 4, which illustrates a simplified schematic of an exemplary LPP EUV radiation source, consistent with embodiments of the present disclosure. LPP EUV radiation source 400 comprises a laser source 410 including a pulsed laser for delivering laser pulses into a chamber 405. A conical or columnar-shaped vessel 406 is defined inside chamber 405. The laser pulses may travel along one or more paths from laser source 410 into vessel 406 to illuminate one or more target material at an irradiation region 462.

[0054] LPP EUV radiation source 400 further includes an EUV controller 420 configured to control triggering one or more lamps or laser devices in laser source 410 to thereby generate light pulses for delivery into vessel 406. LPP EUV radiation source 400 further includes a droplet position detection system 470, which may include one or more droplet imagers configured to provide an output indicative of the position of one or more droplets of the target material, e.g., relative to irradiation region 462. The imager(s) may provide this output to a droplet position detection feedback system 430, which can, e.g., compute a droplet position and trajectory, from which a droplet position error can be computed, e.g., on a droplet-by-droplet basis. The droplet position error may then be provided as an input to controller 420, which can, for example, provide a position, direction or timing correction signal to laser source 410 to control a source timing circuit or to control a beamposition and shaping system, e.g., to change the location or focal power of the light pulses being delivered to irradiation region 462 in vessel 406.

[0055] EUV controller 420 is electronically connected to LPP EUV radiation source 400 and is electronically connected to other components as well. EUV controller 420 may be a computer configured to execute various controls of droplet detection system 470, laser source 410, a droplet delivery control system 440, or a droplet delivery mechanism 450. EUV controller 420 also includes processing circuitry configured to execute various signal and image processing functions. In some embodiments, EUV controller 420 includes one or more processors (not shown). A processor may be a generic or specific electronic device capable of manipulating or processing information. For example, the processor may include any combination of any number of a central processing unit (or “CPU”), a graphics processing unit (or “GPU”), an optical processor, a programmable logic controllers, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a Programmable Logic Array (PLA), a Programmable Array Logic (PAL), a Generic Array Logic (GAL), a Complex Programmable Logic Device (CPLD), a Field-Programmable Gate Array (FPGA), a System On Chip (SoC), an Application-Specific Integrated Circuit (ASIC), and any type circuit capable of data processing. The processor may also be a virtual processor that includes one or more processors distributed across multiple machines or devices coupled via a network. EUV controller 420 may further include one or more memories (not shown). A memory may be a generic or specific electronic device capable of storing codes and data accessible by the processor (e.g., via a bus). For example, the memory may include any combination of any number of a random-access memory (RAM), a read-only memory (ROM), an optical disc, a magnetic disk, a hard drive, a solid-state drive, a flash drive, a security digital (SD) card, a memory stick, a compact flash (CF) card, or any type of storage device. The codes may include an operating system (OS) and one or more application programs (or “apps”) for specific tasks. The memory may also be a virtual memory that includes one or more memories distributed across multiple machines or devices coupled via a network.

[0056] Droplet delivery control system 440 is operable in response to a signal (which in some implementations may include the droplet error described above, or some quantity derived therefrom) from EUV controller 420, to e.g., modify the release point of the target material from droplet delivery mechanism 450 to correct for errors in the droplets arriving at the desired irradiation region 462. For LPP EUV radiation source 400, droplet delivery mechanism 450 may include, for example, a droplet generator creating either 1) one or more streams of droplets or 2) one or more continuous streams that exit the generator and subsequently break into droplets due to surface tension. In either case, droplets may be generated and delivered to irradiation region 462 such that one or more droplets may simultaneously reside in irradiation region 462, allowing one or more droplets to be simultaneously irradiated by an initial pulse, e.g., pre-pulse to form an expanded target suitable for exposure to one or more subsequent laser pulse(s), e.g., main pulse(s), to generate an EUV emission. In someembodiments, a multi-orifice dispenser may be used to create a “showerhead-type” effect. In general, LPP EUV radiation source 400, the droplet generator may be modulating or non-modulating and may include one or several orifice(s) through which target material is passed to create one or more droplet streams.

[0057] The target material may include, but is not limited to, a material that includes tin (Sn), lithium (Li), xenon (Xe), or combinations thereof. The EUV emitting element, e.g., tin, lithium, or xenon, may be in the form of liquid droplets, or solid particles contained within liquid droplets, or any other form which delivers the EUV emitting element to the target volume in discrete amounts. For example, tin may be used as pure tin, as a tin compound, e.g., tin bromide (SnBr ). tin dibromide (SnB ). tin hydride (SnFL), or as a tin alloy, e.g., tin-gallium (Sn-Ga) alloys, tin-indium (Sn-In) alloys, tin-indium-gallium (Sn-In-Ga) alloys, or a combination thereof. Depending on the material used, the target material may be presented to irradiation region 462 at various temperatures, including room temperature or near room temperature (e.g., tin alloys, SnBr4). or at an elevated temperature (e.g., pure tin), or at temperatures below room-temperature, (e.g., SnFL).

[0058] LPP EUV radiation source 400 further includes a droplet catcher 455, also referred to herein as a tin catcher, or a tin catch, configured to catch or collect excessive target material. In some embodiments, the droplets of target material may intentionally or be accidentally missed by the laser beam, and collected by droplet catcher 455. In some embodiments, droplet catcher 455 is aligned with droplet delivery mechanism 450 along direction D2 such that droplet catcher 455 and droplet delivery mechanism 450 are placed on diametrically opposite ends of a reflective optics 460. In some embodiments, a first drainage assembly 456 is coupled to droplet catcher 455 for directing the collected target material toward a first container.

[0059] Continuing with Fig. 4, LPP EUV radiation source 400 also includes reflective optics 460, e.g., a collector mirror in the form of a truncated ellipsoid having, e.g., a graded multi-layer coating with alternating layers of molybdenum and silicon. In some embodiments, reflective optics 460 is formed with an aperture 461 to allow the light pulses generated by laser source 410 to pass through and reach irradiation region 462. Aperture 461 is also configured to introduce one or multiple buffer gas flows. As shown, the reflective optics 460 may be, e.g., an ellipsoidal mirror that has a first focus within or near irradiation region 462 and a second focus at an intermediate focus 464, also referred to herein as an intermediate focus, where the EUV light may be output from LPP EUV radiation source 400 and input to a device utilizing EUV light, e.g., an exposure tool 490 (e.g., a lithography tool or a metrology tool). In some embodiments, reflective optics 460 may be positioned such that the closest operable point on the reflective optics 460 is located at a distance, d' from irradiation region 462. It is to be appreciated that other optics may be used in place of the ellipsoidal mirror for collecting and directing light to an intermediate location for subsequent delivery to a device utilizing EUV light, for example reflective optics 460 may be parabolic or may be configured to deliver a beam having a ring-shaped cross-section to an intermediate location.

[0060] In some embodiments, irradiation of the target material at irradiation region 462 produces a plasma and generates an EUV emission. In addition, as a by-product of this process, debris may be generated that exit the plasma, typically, in all directions. Generally, the debris’ initial energy exiting the plasma will vary over a range, with the range being affected by a number of factors including, but not limited to, the wavelength, energy, intensity and pulse-shape of the irradiating light, and the composition, size, shape and form of the target material. Also indicated above, these debris, if unabated, may degrade nearby optics, such as mirrors, laser input windows, metrology windows, fdters, etc. To mitigate some issues associated with degradation due to unutilized debris, LPP EUV radiation source 400 may include a gas management system including a regulated gas source 475 for introducing one or more gases into vessel 406 and an exhaust mechanism 480 forremoving byproducts of EUV generation process and gas from vessel 406 through a second drainage assembly 481 toward a second container. The first drainage assembly and the second drainage assembly may be the same or different. The first container and the second container may be the same or different. For example, both first drainage assembly 456 and second drainage assembly 481 are coupled to a single container for collecting both target material debris and missed target material. In some embodiments, regulated gas source 475 may be configured to introduce a gas flow in vessel 406 between irradiation region 462 and reflective optic 460, the gas establishing a gas number density n, (i.e. number of molecules / volume) sufficient to operate over the distance d to reduce ion energy to a target maximum energy level before the ions reach the optic. For example, a gas number density sufficient to reduce ion energy to a target maximum energy level between about 10-200 eV, and in some cases below 30 eV may be provided.

[0061] Suitable gases may include hydrogen (FE). e.g., greater than 50% hydrogen (protium and / or deuterium isotopes), helium, or combinations thereof. For example, for a plasma generating ions having a maximum initial ion energy and distance d ~15 cm from the plasma, a suitable gas for reducing ion energy below about 30 eV may be hydrogen gas at a pressure of about 500 mTorr at room temperature may be suitable. It is to be appreciated that gas introduced into the vessel may react with vessel conditions, debris, or the plasma to dissociate or create ions, e.g. atomichydrogen, hydrogen ions which may be effective for cleaning, etching, or ion slowing.

[0062] In some embodiments, regulated gas source 475 may introduce several gases, for example, H2, He, Ar, N2, O2, H2O2, or HBr, either separately and independently, or the gas may be introduced as a mixture. Moreover, although Fig. 4 illustrates the gas being introduced at one location, it is to be appreciated that the gas may be introduced at multiple locations, may be removed at multiple locations, or may be evacuated at multiple locations. The gas may be supplied via a tank or may be generated locally. As illustrated in Fig. 4, gas management system may further include a second gas source 478 providing a stream of gas that flows along a direction from intermediate focus 464 toward irradiation region 462.

[0063] In existing LPP EUV radiation sources, target-material droplets (e.g., tin droplets) dropping at a high frequency interact with a laser beam to generate plasma that emits EUV light. While the present disclosure may refer to tin, it is appreciated that other target materials may be used as well. During operation of the LPP EUV radiation source, although the pulsed laser beam is configured to maximize the interaction volume of the droplets, some pulses of the laser beam may either interact with a partial volume of the droplets (also referred to as a “hit”), or may accidentally or intentionally miss hitting a droplet (also referred to as a “miss”). In addition, the plasma emits the EUV light, accompanied by the generation of byproducts, such as target material vapor and particles. The targetmaterial mass from such interactions is collected in corresponding containers or buckets having a fixed volume. After the containers are full and can no longer hold more target-material mass, the EUV production is interrupted and the equipment is decommissioned for maintenance or service, negatively impacting the throughput. With an increase in device complexity and density, the desired EUV power is higher. Although the higher EUV power demand may be satisfied by increasing the tin supply to the system, for example, by increasing the droplet frequency, the missed tin mass or tin vapor / particles may also increase significantly, necessitating more frequent equipment service and therefore, longer equipment downtime. Therefore, it may be desirable to provide improved systems and methods for managing tin mass generated during operation of an EUV source to allow uninterrupted EUV production while performing equipment service.

[0064] Embodiments of the present disclosure provide systems and methods for managing target material waste generated during operation of an EUV light source, without interrupting EUV production or affecting throughput due to equipment-maintenance related issues. Fig. 5A illustrates a simplified schematic of an exemplary target-material waste management apparatus (e.g., tin waste management apparatus), consistent with embodiments of the present disclosure. Target-material waste management apparatus 500, also referred to as apparatus 500, includes a reservoir 505, a vacuum isolation gate valve 510, a service container 520 and a storage container 545, a valve cover 530, a service door 540, an anti-splash grid 550, a vacuum pump 570, and a vent valve 580. It is to be appreciated that apparatus 500 may include other components or elements, as appropriate.

[0065] Apparatus 500 may be coupled with a target material collector 555of an EUV radiation source (e.g., LPP EUV radiation source 400 of Fig. 4). It is to be appreciated that in some embodiments, target material collector 555 is a part of apparatus 500. As previously discussed with respect to Fig. 4, target material collector 555, such as an exhaust mechanism, is configured to catch excessive target material or tin debris generated upon interaction of the laser beam with the tin droplet. In some embodiments, target material collector 555, such as a tin catcher, is configured to collect the droplets of target material intentionally or accidentally missed by the laser.

[0066] Target material collector 555 may be coupled with apparatus 500 via a drain pipe 560 (e.g., a drainage assembly) configured to connect target material collector 555 to a reservoir 505 of apparatus 500. Drain pipe 560 may comprise a conduit, a pathway, or a passage configured to transport targetmaterial collected in target material collector 555 to reservoir 505. The collected target material in target material collector 555 may flow through drain pipe 560 under gravitational forces, i.e., without external forces such as pressure, influencing the flow of target material. In some embodiments, drain pipe 560 includes a heating element configured to adjust the temperature of drain pipe 560, which influences the flow, or the characteristics, or both, of target material passing through. The heating element may comprise a resistive heating element, a radiative heating element, or a conductive heating element, or a combination thereof.

[0067] In some embodiments, reservoir 505 of apparatus 500 comprises a pressure chamber coupled with a pumping mechanism. The pressure in reservoir 505 may be maintained at a negative pressure with respect to atmospheric pressure, using a vacuum pump 570. The pumping mechanism may include a venting mechanism comprising a vent valve 580 configured to inject a venting gas to increase the pressure in reservoir 505 to atmospheric pressure or above atmospheric pressure, as desired. The pressure in reservoir 505 may be adjusted via operation of vacuum pump 570 or vent valve 580, or both, based on an operation state of apparatus 500. For example, in a normal operation mode, vent valve 580 may be closed and vacuum pump 570 may operate to maintain a negative pressure in reservoir 505 with respect to atmospheric pressure (i.e., vacuum condition). In a service mode, however, vent valve 580 may be opened to allow vent gas to flow and a valve associated with vacuum pump 570 may be closed to allow the pressure in a portion of reservoir 505 to rise to atmospheric pressure.

[0068] Apparatus 500 further comprises a vacuum isolation gate valve 510, configured to separate the interior of reservoir 505 into two spaces 506 and 507, in a closed position (discussed later and illustrated in Fig. 5B). In some embodiments, vacuum isolation gate valve 510 comprises a plate-like structure movable in a horizontal direction along x-axis, perpendicular or substantially perpendicular to the path of the target material in reservoir 505. Vacuum isolation gate valve 510 may comprise a plate having a rectangular, a circular, a triangular, or a polygonal shape, and may be configured to move along the x-axis in a range of positions including fully closed, fully open, and any position between a fully closed and a fully open position. A mechanism to move vacuum isolation gate valve 510 along the x-axis may include, but is not limited to, hydraulic, pneumatic, electric, mechanical, manual, among other mechanisms. In this context, a “fully closed” position of vacuum isolation gate valve 510 refers to a position in which the valve is fully extended in one direction to create a seal between the two separated volumes, and a “fully open” position of vacuum isolation gate valve 510 refers to a position in which the valve is fully retracted in the opposite direction to the fully closed position, thereby providing unhindered flow of material (e.g., fluid) within a chamber (e.g., reservoir 505).

[0069] Vacuum isolation gate valve 510 may further comprise a sealing gasket 512 disposed on a vertical edge surface perpendicular to the direction of motion along the x-axis such that, in the closed position of vacuum isolation gate valve 510, sealing gasket 512 abuts an inner wall of reservoir 505 toform a seal between spaces 506 and 507 (shown in and discussed with reference to Fig. 5B). Sealing gasket 512 may be made from a compressible material such as rubber, Teflon, or metal, among other things.

[0070] In some embodiments, a valve cover 530 is disposed on a top horizontal surface of vacuum isolation gate valve 510. Valve cover 530 may be configured to protect sealing gasket 512, such as a rubber O-ring or a vacuum sealing film, for example, from exposure to target material 565 (e.g., tin debris or liquid tin). In this context, the “top horizontal surface” of vacuum isolation gate valve 510 refers to the surface parallel to x-axis and facing the drain pipe (e.g., drain pipe 560). In some embodiments, valve cover 530 may comprise a flexible cover, including an elastic component 515, to protect sealing gasket 512 from exposure to contaminants. The elastic component 515 includes a spring, diaphragms, and bellow seals. Providing a cover for sealing gasket 512 prevents contaminants from being deposited on the sealing surface 513 of sealing gasket 512, which may enable a tight seal between spaces 506 and 507. Optionally, a second valve cover (not shown) is disposed on a bottom horizontal surface of vacuum isolation gate valve 510 to protect sealing gasket 512 from backsplash contaminants.

[0071] Valve cover 530 is fixedly or removably attached to vacuum isolation gate valve 510. As illustrated in Fig. 5A, valve cover 530 is disposed to fully cover sealing gasket 512, to prevent contaminants from being deposited on sealing surface 513 of sealing gasket 512. In some embodiments, valve cover 530 protrudes, along x-axis, beyond a vertical edge of sealing gasket 512. A protrusion distance d may be adjusted based on a characteristic of elastic component 515, such as spring constant, material of manufacture, thickness of sealing gasket 512, among other things. In this context, protrusion distance d refers to the horizontal distance between sealing surface 513 of sealing gasket 512 associated with vacuum isolation gate valve 510 and a vertical wall 532 of valve cover 530. Vertical wall 532 of valve cover 530 is configured to abut inner wall 508 of reservoir 505, in a fully closed position of vacuum isolation gate valve 510. In some embodiments, valve cover 530 extends along z-axis to cover an entirety of sealing gasket 512. In some embodiments, valve cover 530 aligns with drain pipe 560 along with z-axis to cover only a portion of sealing gasket 512.

[0072] In some embodiments, a service container 520 is coupled with vacuum isolation gate valve 510. Service container 520 may comprise a receptacle, a vessel, a bucket, a container, or any suitable structure configured to hold target material such as liquid tin generated in an EUV radiation source and exiting drain pipe 560, in service mode. In some embodiments, service container 520 is fixedly or removably attached on atop horizontal surface of vacuum isolation gate valve 510 using an attachment mechanism 525. In some embodiments, service container 520 is periodically detached from vacuum isolation gate valve 510 for cleanout and maintenance purposes.

[0073] Reservoir 505 further comprises a storage container 545 configured to collect target material 565 dripping from drain pipe 560. Storage container 545 may be a receptacle, a vessel, a bucket, a container, or any suitable structure configured to hold target material such as liquid tin or molten tingenerated in the EUV radiation source, in normal operation mode. In some embodiments, storage container 545 comprises a heating element configured to adjust the temperature of storage container 545, thereby adjusting the state of target material 565 collected therein. For example, the temperature of storage container may be maintained closer to the melting point of tin to maintain the molten state of target material.

[0074] Apparatus 500 further includes an anti-splash grid 550 placed upstream from storage container 545 configured to mitigate or prevent backsplash of molten tin or other target material towards vacuum isolation gate valve 510 or sealing gasket 512. Anti-splash grid 550 may comprise a mesh, a sieve, a baffle, or any suitable anti-splash structure. In some embodiments, anti-splash grid 550 is fixedly or removably coupled with storage container 545. Alternatively, anti-splash grid 550 is coupled with reservoir 505, or is coupled with service door 540. In some embodiments, anti-splash grid 550 is anon-coupled, individual component, which may be discretely disposed in place or removed using an appropriate mechanism. In this context, “upstream” refers to an overall direction opposite to the direction of flow of target material (e.g., molten tin) from target material collector 555 to storage container 545, and “downstream” refers to an overall direction along the direction of flow of target material from target material collector 555 to storage container 545. As an example, in Fig.5 A, target material flows from drain pipe 560 towards storage container 545, and therefore, vacuum isolation gate valve 510 is placed downstream from drain pipe 560 but upstream from storage container 545.

[0075] Apparatus 500 includes a service door 540 coupled with reservoir 505 and configured to allow introducing and removing storage container 545 from reservoir 505. In some embodiments, service door 540 comprises a glass door, or a door including a glass viewport, or a metal door, or made from any material suitable for vacuum chambers.

[0076] One of several advantages of the proposed systems and methods for managing tin waste includes uninterrupted EUV production, thereby increasing the throughput and reducing equipment downtime for maintenance. This can be realized, in part because, apparatus 500 may be operated in two modes - a normal operation mode and a service mode.

[0077] In normal operation mode, as illustrated in Fig. 5A, target material 565 is directed from target material collector 555 of EUV radiation source (shown in Fig. 4) towards storage container 545 via drain pipe 560. Vacuum isolation gate valve 510 may be in a fully open position (as shown in Fig. 5 A) or in a position to allow an unblocked passage for target material 565 directly into storage container 545. In normal operation mode, reservoir 505 may be maintained at a negative pressure with respect to atmospheric pressure (i.e., in vacuum), the negative pressure obtained using vacuum pump 570 while vent valve 580 is held in a closed position. In some embodiments, a vacuum valve 572 associated with vacuum pump 570 is closed off as well after the desired negative pressure is attained in reservoir 505. Storage container 545 may be placed to receive target material 565 dripping from drain pipe 560 and passing through anti-splash grid 550, which is configured to prevent splashing orback-splashing of target material 565 (e.g., molten tin) on a sealing surface (e.g., sealing surface 513 of sealing gasket 512), or on a surface of vacuum isolation gate valve 510, or on inner walls of reservoir 505. In some embodiments, storage container 545 may be heated to a temperature close to the melting temperature of tin metal (~ 450 °F) to maintain target material 565 in a molten state. Valve cover 530 is configured to prevent contaminants from depositing on sealing gasket 512 or on vacuum isolation gate valve 510. A vertical wall 532 of valve cover 530 protrudes horizontally (along x-axis) beyond a sealing surface 513 of sealing gasket 512 by distance d, offering protection from target material passing through to storage container 545. The service door 540 remains closed during normal operation mode to ensure a tight seal to retain vacuum, or to secure storage container 545 in place, or both.

[0078] As previously discussed, with the increase in desired EUV power, there is a significant increase in the tin load on an EUV power source (e.g., a LPP EUV power source). One of several ways to supply the desired amount of tin while maintaining the throughput is to increase the frequency with which a droplet generator (e.g., droplet delivery mechanism 450 of Fig. 4) generates and delivers tin droplets into the chamber. While doing so may address the increased demand for tin load, it may result in generating more tin waste, thereby requiring more frequent servicing and longer equipment downtime for maintenance. To mitigate some of the challenges discussed above with respect to tin waste management, apparatus 500 may be operated in service mode.

[0079] Reference is now made to Fig. 5B, which illustrates the target-material waste management apparatus 500 operating in service mode, consistent with embodiments of the present disclosure. Apparatus 500 may be operated in service mode if storage container 545 needs to be replaced, or for equipment maintenance, or equipment calibration, among other things. Although Fig. 5B illustrates replacement of storage container 545 in service mode, it is to be appreciated that apparatus 500 may be operated in service mode to perform equipment maintenance, repair, calibration, or general performance routine checks as well.

[0080] In service mode, vacuum isolation gate valve 510 is moved to a fully closed position, isolating spaces 506 and 507 in reservoir 505. In some embodiments, an actuation mechanism including an actuator 518 may be used to move vacuum isolation gate valve 510 from a fully open position (e.g., normal operation mode) to a fully closed position. The actuator mechanism may include, but is not limited to, a hydraulic, a pneumatic, a manual, a thermal, a mechanical, or an electrical mechanism. In the fully closed position, sealing surface 513 of sealing gasket 512 coupled with vacuum isolation gate valve 510 abuts a first portion of inner wall 508 of reservoir 505, maintaining vacuum in space 506. Additionally, vertical wall 532 (shown in Fig. 5A) of valve cover 530 may abut a second portion different from the first portion of inner wall 508 (shown in Fig. 5A) of reservoir 505. As previously discussed, valve cover 530 is configured to protect sealing surfaces (e.g., sealing surface 513) from exposure to contaminants including target material 565, dripping from drainpipe 560 during the movement of vacuum isolation gate valve 510 from a fully open position to the fully closed position.

[0081] Valve cover 530 comprises an elastic component 515 that is in a relaxed state in normal operation mode (i.e., open position or fully open of vacuum isolation gate valve 510 shown in Fig. 5 A), and is under tensile stress in service mode (i.e., closed position of vacuum isolation gate valve 510 shown in Fig. 5B). In some embodiments, in service mode, the tensile stress of elastic component 515 enables forming a tight seal between vertical wall 532 of valve cover 530 and the portion of inner wall 508 of reservoir 505, thus preventing deposition of any contaminant on sealing gasket 512. In some embodiments, valve cover 530 functions as a cover for elastic component 515, preventing deposition of any contaminants including target material 565 or other debris.

[0082] In some embodiments, service container 520 is positioned on the top horizontal surface of vacuum isolation gate valve 510 such that in the service mode, it substantially aligns with drain pipe 560 and collects target material 565 dripping from drain pipe 560, allowing uninterrupted EUV production by continuing to collect target-material waste (e.g., tin waste) during maintenance, repair, or replacements. It should be appreciated that although service container 520 is configured to collect a significant portion of target material 565 dripping from drain pipe 560, valve cover 530 provides protection for sealing gasket 512 from accidental deposition of target material 565.

[0083] In service mode, space 507, separated from space 506 by a fully closed vacuum isolation gate valve 510, may house a component that needs repair, replacement, or calibration. Space 507 may also be referred to herein as a service volume, or service environment, or service space and space 506 may also be referred to herein as a vacuum volume, or vacuum environment, or vacuum space. After vacuum isolation gate valve 510 is fully closed, vent valve 580 may be opened to introduce a purge gas (e.g., hydrogen, or nitrogen, extreme clean dry air, or an inert gas) to increase the pressure in space 507 from negative pressure (i.e., vacuum) to atmospheric pressure. A vacuum valve 572 associated with vacuum pump 570 configured to evacuate reservoir 505 may be closed in combination with an open vent valve 580 to facilitate venting space 507 to atmospheric pressure. In service mode, space 506 is maintained under negative pressure with respect to atmospheric pressure and space 507 is brought to and maintained at atmospheric pressure, the separation being enabled by holding vacuum isolation gate valve 510 in a fully closed position.

[0084] After venting space 507 to atmospheric pressure, service door 540 may be opened (as illustrated in Fig. 5B) to allow storage container 545 to be removed from reservoir 505. In some embodiments, storage container 545, configured to receive target material 565 dripping from drain pipe 560, may retain target material 565 in molten form 565M (shown in Fig. 5A) or in solidified form 565S (shown in Fig. 5B). During service of apparatus 500, a filled storage container 545, containing molten form 565M or solidified form 565S of target material 565, may be removed and replaced with an empty storage container 545, either by emptying and cleaning old storage container 545 or introducing an unused storage container 545. After replacing storage container 545, servicedoor 540 is closed and a gas purge cycle is performed by opening vacuum valve 572 associated with vacuum pump 570, as illustrated in Fig. 5C. Vent valve 580 may be closed to stop introduction of purge gas so that vacuum pump 570 may efficiently evacuate space 507 to create negative pressure. In some embodiments, purge gas may continue to be introduced to purge space 507 of any undesired contaminants or debris.

[0085] Fig. 5D illustrates apparatus 500 operating in normal operation mode after a servicing has been performed, consistent with embodiments of the present disclosure. In some embodiments, apparatus 500 comprises a pressure gauge (not shown) in each of spaces 506 and 507 to measure or monitor the pressure (or vacuum) within the volumes. Vacuum isolation gate valve 510 may be moved to a fully open position, as shown in Fig. 5D, after the pressure measured by corresponding pressure gauges is equal or substantially equal in each of spaces 506 and 507. In this context, “substantially equal” pressure refers to a negligible difference in pressure between two spaces (e.g., spaces 506 and 507), such that the pressure in one space is within ± 10% of the pressure in another space. For example, the pressures in spaces 506 and 507 would be substantially equal if pressure in space 506 is 10 mTorr and pressure in space 507 is either 9 mTorr or 11 mTorr.

[0086] Reference is now made to Fig. 6A, which illustrates an exemplary target-material waste management apparatus 600A, consistent with embodiments of the present disclosure. In comparison with apparatus 500, service container 620 of apparatus 600 is not associated or coupled with vacuum isolation gate valve 610. In some embodiments, position of service container 620 is adjusted independently from position of vacuum isolation gate valve 610. Apparatus 600 comprises an actuation mechanism 690 associated with and configured to move service container 620 independently from movement of vacuum isolation gate valve 610.

[0087] In normal operation mode, mechanism 690 may be deactivated and parked in a first position away from drain pipe 660 so that target material 665 may drip without hinderance towards storage container 645. In service mode, however, actuation mechanism 690 may be activated to move service container 620 from its first position to a second position to collect dripping target material 665. After service container 620 is securely positioned in the second position, vacuum isolation gate valve 510 may be adjusted from a fully open position to a fully closed position (as shown in Fig. 6A). The actuation mechanism 690 may include, but is not limited to, electrostatic actuation, magnetic actuation, thermal actuation, hydraulic actuation, or pneumatic actuation. Although not illustrated, apparatus 600 may include a valve cover (e.g., valve cover 530 of Fig. 5A) to provide protection to sealing gasket 612 from accidental exposure to target material 665. It is to be appreciated that although not illustrated, apparatus 600 may include other components.

[0088] In some cases, it may be desirable to maintain target material waste (e.g., molten tin waste) in its molten state in a service container (e.g., service container 520 of Fig. 5A). Fig. 6B illustrates an exemplary apparatus 600B comprising a heated service container, consistent with embodiments of the present disclosure. In addition to actuation mechanism 690, apparatus 600B may include a heatingmechanism 695 and heater element 696, configured to adjust the temperature of service container 620. Heating mechanism 695 may heat service container 620 by resistive heating, for example.

[0089] Reference is now made to Fig. 7, which illustrates an exemplary target-material waste management apparatus 700, consistent with embodiments of the present disclosure. In comparison with apparatus 500, apparatus 700 comprises a heated service container 720 associated with vacuum isolation gate valve 710. In some embodiments, heated service container 720 is securely fastened on a top surface of vacuum isolation gate valve 710 using a fastening mechanism such as welding, for example. Apparatus 700 may further include a heating mechanism 790 coupled with a heating wire 792 configured to adjust the temperature of heated service container 720. In such designs, vacuum isolation gate valve 710 may include a cavity 714 through which heating wire 792 may be inserted. Heating wire 792, passing through cavity 714, may be electrically connected to a heater element associated with heated service container 720.

[0090] Reference is now made to Fig. 8, which illustrates a process flowchart of an exemplary method 800 for managing waste associated with an operation of a fuel-based radiation source, consistent with embodiments of the present disclosure. Method 800 may include steps performed to manage target-material waste (e.g., tin debris) in radiation sources.

[0091] In step 810, a plurality of droplets of target material (e.g., target material 565 of Fig. 5 A) are directed into a reservoir (e.g., reservoir 505 of Fig. 5A) through a conduit (e.g., drain pipe 560 of Fig.5A). The target material may include tin mass associated with operation of a LPP EUV source. In some embodiments, target material is directed from a storage location (e.g., droplet catcher 455 of Fig. 4) associated with the LPP EUV radiation source into the reservoir. The target material may include tin droplets generated by interaction of a laser beam with a tin droplet or tin droplets that are accidentally or intentionally missed, or both. The conduit includes a drain pipe connecting a droplet catcher or a tin scrubber (not shown).

[0092] In step 820, a position of a valve (e.g., vacuum isolation gate valve 510) associated with the reservoir and disposed within a volume of the reservoir is adjusted based on an operation mode of the radiation source. The operation modes include a normal operation mode (e.g., EUV production mode) and a service mode (e.g., maintenance or repair mode). The valve may comprise a plate movable within the volume of the reservoir from a retracted position to an extended position. As used herein, the retracted position of the valve refers to an “open” or a “fully open” position and the extended position of the valve refers to a “closed” or “fully closed” position. The position of the valve may be adjusted using an actuation mechanism comprising a hydraulic, a pneumatic, a mechanical, or an electrical actuator, among other mechanisms. The actuation mechanism may include an actuator (e.g., actuator 518 of Fig. 5A) configured to actuate the valve to adjust the position of the valve within the reservoir.

[0093] In the EUV production mode, also referred to as the production mode, the valve is positioned in the retracted position to enable the plurality of droplets of target material into a receptacle (e.g.,second container 545 of Fig. 5A) placed within the volume of the reservoir. The receptacle is placed downstream from the valve in the second space. The receptacle comprises an anti -splash grid (e.g., anti-splash grid 550 of Fig. 5A) configured to minimize or prevent backsplash of molten tin mass (e.g., molten target material 565M) onto inner walls (e.g., inner wall 508 of Fig. 5A) of the reservoir. In some embodiments, the anti-splash grid may comprise a mesh or a grid placed above the receptacle.

[0094] The radiation source may be operated in service mode to perform routine maintenance, repair, or to replace a filled receptacle, among other reasons. In the service mode, the position of the valve is adjusted from the retracted position (shown in Fig. 5A) to the extended position (shown in Fig. 5B). As previously discussed, an actuation mechanism including an actuator may be configured to move the valve horizontally along the x-axis from the retracted position to the extended position.

[0095] In the extended position, a sealing surface (e.g., sealing surface 513 of Fig. 5A) of a sealing gasket (e.g., sealing gasket 512 of Fig. 5A) associated with the valve abuts a first portion of the inner wall of the reservoir to form a seal between the first space (e.g., first space 506 of Fig. 5B) and the second space (e.g., second space 507 of Fig. 5B) of the reservoir.

[0096] A container (e.g., first container 520 of Fig. 5A) is disposed on a horizontal surface of the valve. In the service mode when the valve is in extended position, the container is aligned with the conduit and is configured to collect target-material mass (e.g., tin material 565) dripping from droplet catcher or tin scrubber associated with the radiation source. Isolating the first space, by forming a seal, and providing an outlet for the tin mass generated by the EUV production, enables uninterrupted operation of the EUV radiation source.

[0097] The valve further comprises a valve cover (e.g., valve cover 530 of Fig. 5A) disposed on the horizontal surface at a different location from the container. The valve cover is configured to protect the sealing surface from contaminants including target material dropping from the conduit in the EUV production mode (i.e., open position of the valve), in the service mode (i.e., closed position of the valve), and during the movement of the valve from the retracted position to the extended position and back. In the extended position, a vertical wall (e.g., vertical wall 532 of Fig. 5A) of the valve cover may abut a second portion of the inner wall of the reservoir different from the first portion. The valve cover comprises a deformable elastic component (e.g., elastic component 515 of Fig. 5 A) configured to be substantially free of stress (unelongated) in the retracted position of the valve during the production mode and to be under tensile stress (elongated) in the extended position of the valve during the service mode. The valve cover is configured to protect the deformable elastic component from contaminants including tin mass in the reservoir.

[0098] In the service mode, the second space may be purged using an inert gas through a vent valve (e.g., vent valve 580 of Fig. 5B) to raise the pressure from a negative pressure to atmospheric pressure, thereby venting the second space to atmospheric pressure. A vacuum valve (e.g., vacuum valve 572 of Fig. 5B) associated with vacuum pump (e.g., vacuum pump 570 of Fig. 5B) may beclosed. The reservoir may comprise a service door (e.g., service door 540 of Fig. 5B) located in the second space and configured to allow introduction and removal of the receptacle, as needed. In the service mode, a filled receptacle (e.g., filled with solidified form 565 S of target material or molten form 565M of target material) may be pulled out of the reservoir through the service door and replaced with an empty receptacle. In some embodiments, the receptacle comprises a heating element configured to adjust a temperature of the receptable.

[0099] After replacing the filled receptacle with an empty receptacle, the service door may be closed, and the vacuum valve may be opened to cycle the purge gas in the second space. After the purge cycles, the vent valve may be closed to enable pumping the second space to a negative pressure substantially similar to the negative pressure in the first space. After reaching a substantially equal pressure in the first and the second space, the valve may be retracted in the open position, thereby switching to the normal EUV production mode.

[0100] A non-transitory computer readable medium may be provided that stores instructions for one or more processors of a controller (not shown) to directing components to carry out, among other things, activating laser sources, generating and delivering droplets into a chamber, power amplification, frequency modulation, activating one or more actuators for moving isolation gate valve, heating a service container or a storage container, activate valves for pump and purge cycles, and at least some steps of method 800. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-ROM), any other optical data storage medium, any physical medium with patterns of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), and Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM or any other flash memory, Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions of the same.

[0101] Block diagrams in the figures may illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer hardware or software products according to various exemplary embodiments of the present disclosure. In this regard, each block in a schematic diagram may represent certain arithmetical or logical operation processing that may be implemented using hardware such as an electronic circuit. Blocks may also represent a module, segment, or portion of code that comprises one or more executable instructions for implementing the specified logical functions. It should be understood that in some alternative implementations, functions indicated in a block may occur out of the order noted in the figures. For example, two blocks shown in succession may be executed or implemented substantially concurrently, or two blocks may sometimes be executed in reverse order, depending upon the functionality involved. Some blocks may also be omitted. It should also be understood that each block of the block diagrams, and combination of the blocks, may be implemented by special purpose hardware-based systems thatperform the specified functions or acts, or by combinations of special purpose hardware and computer instructions.

[0102] The embodiments of the present disclosure may further be described using the following clauses:1. An apparatus associated with a radiation source, the apparatus comprising:a reservoir connected with a target material catch of the radiation source through a conduit; a valve associated with the reservoir and configured to be movable within a volume of the reservoir; anda first container placed on a horizontal surface of the valve at a first location,wherein in an extended position, the valve is configured to separate the volume of the reservoir in a first space and a second space, andwherein in the extended position, the first container is configured to be aligned with the conduit to collect target material.2. The apparatus of clause 1, further comprising a valve cover disposed on the horizontal surface of the valve at a second location different from the first location.3. The apparatus of clause 2, wherein the valve cover is configured to protect a sealing surface of the valve from contaminants, the sealing surface comprising a surface of a gasket disposed on a vertical edge of the valve.4. The apparatus of clause 3, wherein the sealing surface abuts a first portion of an inner wall of the reservoir to form a seal isolating the first space from the second space in the extended position of the valve.5. The apparatus of clause 4, wherein a vertical edge of the cover abuts a second portion of the inner wall of the reservoir different from the first portion in the extended position of the valve.6. The apparatus of clause 5, wherein the valve cover comprises a deformable elastic component configured to elongate along a horizontal direction when the vertical edge of the valve cover abuts the second portion of the inner wall of the reservoir.7. The apparatus of clause 6, wherein the valve cover is configured to protect the deformable elastic component from contaminants.8. The apparatus of any one of clauses 6 and 7, wherein the deformable elastic component is substantially free of tensile stress in a retracted position of the valve and is under tensile stress in the extended position of the valve.9. The apparatus of clause 8, wherein a portion of the valve cover protrudes beyond the vertical edge of the valve along the horizontal direction in the retracted position of the valve.10. The apparatus of any one of clauses 1-9, wherein the first container is removably attached to the valve.11. The apparatus of any one of clauses 1-10, further comprising a first heating element associated with and configured to adjust a temperature of the first container.12. The apparatus of any one of clauses 8-11, further comprising a second container configured to collect target material from the target material catch in the retracted position of the valve.13. The apparatus of clause 12, further comprising an anti-splash grid configured to prevent backsplash of target material.14. The apparatus of clause 13, wherein the anti-splash grid is attached to the second container.15. The apparatus of clause 13, wherein the anti-splash grid is positioned in the second space between the valve and the second container.16. The apparatus of any one of clauses 12-15, further comprising a second heating element associated with the second container and configured to adjust a temperature of the second container.17. The apparatus of any one of clauses 1-16, further comprising a pumping mechanism configured to evacuate the volume of the reservoir to a negative pressure with respect to atmospheric pressure.18. The apparatus of clause 17, wherein the pumping mechanism is further configured to independently adjust a pressure in the first space and the second space.19. The apparatus of any one of clauses 1-18, wherein the valve comprises an isolation gate valve configured to be movable by an actuation mechanism, the actuation mechanism comprising a hydraulic, a pneumatic, a mechanical, or an electrical actuator.20. A method for managing target material associated with operation of a radiation source, the method comprising:directing a plurality of droplets of target material into a reservoir through a conduit; and adjusting a position of a valve within a volume of the reservoir based on an operation mode of the radiation source, the operating mode comprising a production mode and a service mode, wherein operating in the production mode comprises positioning the valve in a retracted position to enable the plurality of droplets of target material into a receptacle placed within the volume of the reservoir, andwherein operating in the service mode comprises:positioning the valve in an extended position to separate the volume of the reservoir into a first space and a second space, andcollecting the plurality of droplets of target material into a container disposed at a first location on a horizontal surface of the valve.21. The method of clause 20, wherein the retracted position and the extended position of the valve comprise an open position and a closed position, respectively.22. The method of clause 21, further comprising protecting a sealing surface of the valve from contaminants using a valve cover, the sealing surface comprising a surface of a gasket disposed on a vertical edge of the valve.23. The method of clause 22, wherein separating the volume of the reservoir in the first space and the second space comprises:abuting the sealing surface with a first portion of an inner wall of the reservoir to form a seal; andabuting a vertical edge of the valve cover with a second portion of the inner wall of the reservoir different from the first portion.24. The method of clause 23, wherein the valve cover comprises a deformable elastic component, and wherein abuting the vertical edge of the valve cover causes elongation of the deformable elastic component along a horizontal direction.25. The method of clause 24, wherein the valve cover is configured to protect the deformable elastic component from contaminants.26. The method of any one of clauses 20-25, further comprising adjusting a temperature of the container using a first heating element.27. The method of any one of clauses 20-26, further comprising adjusting a temperature of the receptacle using a second heating element.28. The method of any one of clauses 20-27, wherein operating the radiation source in the service mode comprises moving the valve from the retracted position to the extended position using an actuation mechanism, the actuation mechanism comprising a hydraulic, a pneumatic, a mechanical, or an electrical actuator.29. An apparatus associated with a radiation source, the apparatus comprising:a reservoir connected with a target material catch of the radiation source through a conduit; a valve associated with the reservoir and configured to be movable within a volume of the reservoir in an open position and in a closed position, wherein in the closed position, the valve is configured to separate the volume of the reservoir in a first space and a second space; anda container disposed in the first space between the valve and the conduit and configured to be movable to align with the conduit to capture target material dripping from the target material catch into the volume of the reservoir.

[0103] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in connection with various embodiments; other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

CLAIMS1. An apparatus associated with a radiation source, the apparatus comprising:a reservoir connected with a target material catch of the radiation source through a conduit;a valve associated with the reservoir and configured to be movable within a volume of the reservoir; anda first container placed on a horizontal surface of the valve at a first location, wherein in an extended position, the valve is configured to separate the volume of the reservoir in a first space and a second space, andwherein in the extended position, the first container is configured to be aligned with the conduit to collect target material.

2. The apparatus of claim 1, further comprising a valve cover disposed on the horizontal surface of the valve at a second location different from the first location.

3. The apparatus of claim 2, wherein the valve cover is configured to protect a sealing surface of the valve from contaminants, the sealing surface comprising a surface of a gasket disposed on a vertical edge of the valve.

4. The apparatus of claim 3, wherein the sealing surface abuts a first portion of an inner wall of the reservoir to form a seal isolating the first space from the second space in the extended position of the valve.

5. The apparatus of claim 4, wherein a vertical edge of the cover abuts a second portion of the inner wall of the reservoir different from the first portion in the extended position of the valve.

6. The apparatus of claim 5, wherein the valve cover comprises a deformable elastic component configured to elongate along a horizontal direction when the vertical edge of the valve cover abuts the second portion of the inner wall of the reservoir.

7. The apparatus of claim 6, wherein the deformable elastic component is substantially free of tensile stress in a retracted position of the valve and is under tensile stress in the extended position of the valve.

8. The apparatus of claim 7, wherein a portion of the valve cover protrudes beyond the vertical edge of the valve along the horizontal direction in the retracted position of the valve.

9. The apparatus of claim 1, further comprising a first heating element associated with and configured to adjust a temperature of the first container.

10. The apparatus of claim 1, further comprising a second container configured to collect target material from the target material catch in a retracted position of the valve.

11. The apparatus of claim 10, further comprising an anti-splash grid configured to prevent backsplash of target material, wherein the anti-splash grid is positioned in the second space between the valve and the second container.

12. The apparatus of claim 10, further comprising a second heating element associated with the second container and configured to adjust a temperature of the second container.

13. The apparatus of claim 1, further comprising a pumping mechanism configured to evacuate the volume of the reservoir to a negative pressure with respect to atmospheric pressure.

14. A method for managing target material associated with operation of a radiation source, the method comprising:directing a plurality of droplets of target material into a reservoir through a conduit; andadjusting a position of a valve within a volume of the reservoir based on an operation mode of the radiation source, the operating mode comprising a production mode and a service mode,wherein operating in the production mode comprises positioning the valve in a retracted position to enable the plurality of droplets of target material into a receptacle placed within the volume of the reservoir, andwherein operating in the service mode comprises:positioning the valve in an extended position to separate the volume of the reservoir into a first space and a second space, andcollecting the plurality of droplets of target material into a container disposed at a first location on a horizontal surface of the valve.

15. The method of claim 14, further comprising protecting a sealing surface of the valve from contaminants using a valve cover, the sealing surface comprising a surface of a gasket disposed on a vertical edge of the valve.

16. The method of claim 15, wherein separating the volume of the reservoir in the first space and the second space comprises:abutting the sealing surface with a first portion of an inner wall of the reservoir to form a seal; andabutting a vertical edge of the valve cover with a second portion of the inner wall of the reservoir different from the first portion.

17. The method of claim 16, wherein the valve cover comprises a deformable elastic component, and wherein abutting the vertical edge of the valve cover causes elongation of the deformable elastic component along a horizontal direction.

18. The method of claim 14, further comprising adjusting a temperature of the container using a first heating element, andadjusting a temperature of the receptacle using a second heating element.

19. The method of claim 14, wherein operating in the service mode comprises moving the valve from the retracted position to the extended position using an actuation mechanism, the actuation mechanism comprising a hydraulic, a pneumatic, a mechanical, or an electrical actuator.

20. An apparatus associated with a radiation source, the apparatus comprising:a reservoir connected with a target material catch of the radiation source through a conduit; a valve associated with the reservoir and configured to be movable within a volume of the reservoir in an open position and in a closed position, wherein in the closed position, the valve is configured to separate the volume of the reservoir in a first space and a second space; anda container disposed in the first space between the valve and the conduit and configured to be movable to align with the conduit to capture target material dripping from the target material catch into the volume of the reservoir.

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