WO2022063509A2

WO2022063509A2 - Pressure relief apparatus and method in a target material supply system

Info

Publication number: WO2022063509A2
Application number: PCT/EP2021/073421
Authority: WO
Inventors: Rahul Sunil KAPADIA; Chirag Rajyaguru; Martinus Hendrikus Antonius Leenders; Stephen William KOWALK; Georgiy Olegovich VASCHENKO
Original assignee: Asml Netherlands B.V.
Priority date: 2020-09-23
Filing date: 2021-08-24
Publication date: 2022-03-31
Also published as: CN116235637A; WO2022063509A3; TW202231126A; KR20230071137A

Abstract

A pressure relief apparatus includes a pressure relief component formed of a compressible material and disposed at an interior surface of a structure within a target material supply system. The target material supply system is configured to deliver target material. The interior surface of the structure defines a cavity within the target material supply system. The structure is formed of a rigid material, and is configured to contain the target material within the cavity. The pressure relief component is configured to passively prevent a pressure in the cavity from exceeding a maximum allowed value.

Description

PRESSURE RELIEF APPARATUS AND METHOD IN A TARGET MATERIAL SUPPLY SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Application No. 63/082,234, filed September 23, 2020, titled PRESSURE RELIEF APPARATUS AND METHOD IN A TARGET MATERIAL SUPPLY SYSTEM, which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

[0002] This disclosure relates to a pressure relief apparatus and method in a target material supply system.

BACKGROUND

[0003] In semiconductor lithography (or photolithography), a lithography exposure apparatus (which is also referred to as a scanner) is a machine that applies a desired pattern onto a target region of the substrate. A patterning device, which is alternatively referred to as a mask or a reticle, can be used to generate the desired pattern to be formed. Transfer of the pattern is typically accomplished by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004] The substrate is irradiated by a light beam, which has a wavelength in the ultraviolet range, somewhere between visible light and x-rays, and thus has a wavelength between about 10 nanometers (nm) to about 400 nm. Thus, the light beam can have a wavelength in the deep ultraviolet (DUV) range, for example, with a wavelength that can fall from about 100 nm to about 400 nm or a wavelength in the extreme ultraviolet (EUV) range, with a wavelength between about 10 nm and about 100 nm. These wavelength ranges are not exact, and there can be overlap between whether light is considered as being DUV or EUV. For example, DUV excimer lasers are commonly used to produce the light beam. Examples of DUV excimer lasers include the krypton fluoride (KrF) laser at a 248 nm wavelength and the argon fluoride (ArF) laser at a 193 nm wavelength.

SUMMARY

[0005] In some general aspects, a pressure relief apparatus includes a pressure relief component formed of a compressible material and disposed at an interior surface of a structure within a target material supply system. The target material supply system is configured to deliver target material. The interior surface defines a cavity within the target material supply system. The structure is formed of a rigid material and is configured to contain the target material within the cavity. The pressure relief component is configured to passively prevent a pressure in the cavity from exceeding a maximum allowed value. [0006] Implementations can include one or more of the following features. For example, the pressure relief component can be a liner that covers at least a portion of the interior surface of the structure. The structure can be a hollow cylindrical tube, the cavity can be cylindrical, and the liner can cover at least a portion of the interior surface of the hollow cylindrical tube. The pressure relief component can have a cylindrical shape with one or more grooves at a side of the cylindrical shape that extend axially along the cylindrical shape, and the pressure relief component can be fitted into the cylindrical cavity of the hollow cylindrical tube. The pressure relief component can have a rectangular bar shape, a hexagonal bar shape, or a polygonal bar shape, and the pressure relief component can fill at least a portion of the structure.

[0007] The structure can be a demountable connection that connects two separate and distinct fluid devices and the pressure relief apparatus can be a liner or a sleeve that at least partially extends over the demountable connection.

[0008] The compressible material can remain in an elastic regime at temperatures greater than the melting range of the target material such that the compressible material is compatible above the melting range of the target material and at pressures greater than 20 Megapascals (MPa), up to a maximum allowed pressure.

[0009] The compressible material can have an elastic modulus that remains below 6 GPa at operating temperature. A ratio of a volume of the compressible material disposed at the interior surface of the structure to a volume of the target material contained within the cavity of the structure can be related to an elastic modulus of the compressible material. The elastic modulus of the compressible material can be less than an elastic modulus of the structure. The compressible material can remain in a linear elastic regime after being repeatedly compressed and decompressed. The compressible material can be configured to deform when the compressible material is compressed and decompressed, and the deformation of the compressible material can be nonpermanent.

[0010] The compressible material can be a polymer material. The polymer material can be polyimide, polytetrafluoroethylene, polybenzimidazole, or poly ether ether ketone.

[0011] The pressure relief component can be a liner that covers at least a portion of the interior surface of the structure, and a ratio of a volume of the liner that covers the interior surface of the structure to a volume of the target material contained within the cavity of the structure can be at least 1. The compressible material can be polyimide such that the liner is formed of polyimide, the structure is formed of molybdenum, and the volume of the liner occupies at least 80% of the cavity of the structure and the volume of the target material occupies the rest of the cavity of the structure. The polyimide liner can experience elastic deformation and not experience permanent or plastic deformation.

[0012] The compressible material can be a rigid foam material with closed cells. The compressible material can be compatible (for example, chemically and/or thermally compatible) with the target material. [0013] In other general aspects, a target material supply system is configured to deliver particles of a target material to a target space inside a chamber. The target material supply system includes: one or more structures, each structure configured to retain the target material within a cavity defined by an interior surface of the structure; and a pressure relief apparatus associated with at least one of the structures. The pressure relief apparatus includes a passive pressure relief device including a compressible mechanism in fluid communication with the cavity and configured to passively change the pressure in the cavity. The compressible mechanism can expand an effective volume of the cavity to compensate for an increase in volume of target material in the cavity.

[0014] Implementations can include one or more of the following features. For example, the increase in the volume of the target material in the cavity can be caused by a change in temperature of the target material. The material can be a fluid target material that radiates ultraviolet light (such as extreme ultraviolet light) when in a plasma state.

[0015] The compressible mechanism can be a liner that covers at least a portion of the interior surface of the structure with which the pressure relief apparatus is associated. The structure with which the pressure relief apparatus is associated can be a hollow cylindrical tube having a cylindrical cavity, and the liner can cover at least a portion of the interior surface of the hollow cylindrical tube. The liner can occupy about 90% of the cavity of the structure with which the pressure relief apparatus is associated.

[0016] The compressible mechanism can be a polymer material.

[0017] The compressible mechanism can be or include an inert gas that does not react with the target material and can be formed to be in a physical contact with the target material. The inert gas can be argon (Ar), xenon (Xe), helium (He), nitrogen (Nj), hydrogen (Hz), or carbon monoxide (CO). The inert gas can occupy about 2% to about 10% of the cavity of the structure with which the pressure relief apparatus is associated.

[0018] The passive pressure relief device can be a pressure relief valve and the compressible mechanism can be a mechanical spring configured to passively change the effective volume in the cavity. The pressure relief valve can remain closed as the effective volume of the cavity changes. The pressure relief valve and the mechanical spring can each made of a material that is compatible (such as chemically and/or thermally) with the target material at associated temperatures and pressures above the melting range of the target material. The material can be a refractory metal or a ceramic material.

[0019] The target material can be tin, lithium, xenon, or a tin alloy.

[0020] A pressure relief apparatus can be associated with a plurality of cylindrical structures, each cylindrical structure being a hollow cylindrical tube having a cylindrical cavity that transfers the target material. Each of the cylindrical structures can be connected to another one or more of the structures by a demountable connection. The demountable connection can be associated with another pressure relief apparatus that includes another passive pressure relief device including another compressible mechanism.

[0021] The target material supply system can further include a target material source configured to create a fluid target material from a solid target material, and a nozzle apparatus configured to direct the particles of the target material to interact with a light beam, the interaction of the particles with the light beam creating a plasma of the target material and producing ultraviolet light (such as extreme ultraviolet light).

[0022] In other general aspects, a target material supply system is configured to deliver particles of a target material, the target material supply system including an apparatus. The apparatus includes: a pressure relief device including a compressible mechanism in fluid communication with an interior of a cavity within a structure of the target material supply system, the cavity configured to contain the target material within the interior of the cavity. The compressible mechanism of the pressure relief device is configured to passively change an effective volume in the cavity by absorbing or releasing energy associated with the pressure in the cavity.

[0023] In other general aspects, a method is performed for regulating a pressure of a target material in a target material supply system. The target material supply system includes one or more unconfined zones, each unconfined zone defined by an open cavity that allows the pressure of the target material to be regulated when a temperature of the unconfined zone is greater than a melting range of the target material, and one or more confined zones, each confined zone defined by a closed cavity. The method includes: identifying one or more of the unconfined zones; melting the target material in at least one of the identified unconfined zones such that the at least one unconfined zone has a temperature greater than the melting range of the target material; and melting the target material in each confined zone that has a temperature less than the melting range of the target material only if the confined zone is adjacent to at least one of the unconfined zones that has a temperature greater than the melting range of the target material to thereby regulate the pressure of the target material in the confined zone.

[0024] Implementations can include one or more of the following features. For example, the target material in the unconfined zone can be melted by heating the target material such that the target material expands into the open cavity of the unconfined zone to regulate the pressure of the target material.

[0025] The target material in the confined zone can be melted by heating the target material such that the target material expands into the at least one adjacent unconfined zone to thereby regulate the pressure of the target material.

[0026] Each of the one or more confined zones and the one or more unconfined zones can be defined as a separate and distinct structure. Each structure that is a confined zone can be at least one of: a pipe configured to transfer the target material between other structures; a freeze valve configured to separate two or more of the other structures; a droplet generator assembly configured to create particles in the form of droplets of the target material; and a nozzle configured to direct the particles of the target material to interact with a light beam that irradiates the particles into a plasma state, thereby producing ultraviolet light. At least one of the structures that is an unconfined zone can be a target material reservoir configured to hold the target material.

[0027] The method can further include melting the target material in one or more other confined zones that have a temperature less than the melting range of the target material only if the other confined zone is adjacent to at least one of the confined zones that has a temperature greater than the melting range of the target material. The target material in the confined zones can be melted by heating the target material in each of the one or more confined zones that have a temperature less than the melting range of the target material in a sequence such that each confined zone is adjacent to at least one of the unconfined zones and/or confined zones that has a temperature greater than the melting range of the target material at each step of the sequence.

DESCRIPTION OF DRAWINGS

[0028] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of the aspects of this disclosure and to enable a person skilled in the relevant art(s) to make and use the aspects of this disclosure.

[0029] Fig. 1 is a block diagram of a target material supply system including one or more structures configured to retain the target material and a pressure relief apparatus associated with at least one of the structures.

[0030] Fig. 2 is a block diagram of the pressure relief apparatus of Fig. 1 that is associated with one of the structures of Fig. 1, the pressure relief apparatus including a passive pressure relief device that includes a compressible mechanism configured to passively accommodate a change volume of a target material in a cavity of the associated structure.

[0031] Fig. 3A is a block diagram of the pressure relief apparatus of Fig. 2, in which the pressure relief apparatus provides additional volume to compensate for an increase in volume of target material within the cavity of the associated structure.

[0032] Fig. 3B is a block diagram of the pressure relief apparatus of Fig. 2, in which the pressure relief apparatus fills a volume to compensate for a decrease in volume of target material within the cavity of the associated structure.

[0033] Fig. 4 is a block diagram of an implementation of the pressure relief apparatus of Fig. 2 that is associated with a structure configured to retain the target material, the pressure relief apparatus including a liner formed of a compressible material as the compressible mechanism.

[0034] Fig. 5A is a block diagram of the pressure relief apparatus of Fig. 4, in which the pressure relief apparatus provides additional volume to compensate for an increase in volume of target material within the cavity of the associated structure. [0035] Fig. 5B is a block diagram of the pressure relief apparatus of Fig. 4, in which the pressure relief apparatus fills a volume to compensate for a decrease in volume of target material within the cavity of the associated structure.

[0036] Fig. 6A is a block diagram of another implementation of the pressure relief apparatus of Fig. 4 that includes a liner formed of a compressible material as the compressible mechanism, the pressure relief apparatus associated with a cylindrical structure configured to retain the target material.

[0037] Fig. 6B is a cross-sectional view of the pressure relief apparatus of Fig. 6A taken along the line 6B-6B.

[0038] Fig. 6C is a cross-sectional view of another implementation of the pressure relief apparatus of Fig. 6 A taken along the line 6B-6B.

[0039] Fig. 6D is a cross-sectional view of the pressure relief apparatus of Fig. 6C, in which the liner has compressed.

[0040] Fig. 7 is a block diagram of a plurality of pressure relief apparatuses that are each associated with one respective cylindrical structure, the cylindrical structures including: the cylindrical structure of Fig. 6A; another cylindrical structure that is a pipe; and a cylindrical structure that is a demountable connection.

[0041] Fig. 8 is a block diagram of another implementation of the pressure relief apparatus of Fig. 2 that is associated with the structure of Fig. 4, the pressure relief apparatus including an inert gas in the form of a bubble as the compressible mechanism.

[0042] Fig. 9A is a block diagram of the pressure relief apparatus of Fig. 8, in which the pressure relief apparatus provides additional volume to compensate for an increase in volume of target material within the cavity of the associated structure.

[0043] Fig. 9B is a block diagram of the pressure relief apparatus of Fig. 8, in which the pressure relief apparatus fills a volume to compensate for a decrease in volume of target material within the cavity of the associated structure.

[0044] Fig. 9C is a block diagram of an implementation of the pressure relief apparatus of Fig. 8, in which the pressure relief apparatus provides additional volume to compensate for an increase in volume of target material within the cavity of the associated structure.

[0045] Fig. 9D is a block diagram of the implementation of Fig. 9C of the pressure relief apparatus of Fig. 8, in which the pressure relief apparatus fills a volume to compensate for a decrease in volume of target material within the cavity of the associated structure.

[0046] Fig. 10 is a block diagram of another implementation of the pressure relief apparatus of Fig. 2 that is associated with the structure of Fig. 4, the pressure relief apparatus including a pressure relief valve as the passive pressure relief device and a mechanical spring as the compressible mechanism. [0047] Fig. 11 A is a block diagram of the pressure relief apparatus of Fig. 10, in which the pressure relief apparatus provides additional volume to compensate for an increase in volume of target material within the cavity of the associated structure. [0048] Fig. 1 IB is a block diagram of the pressure relief apparatus of Fig. 10, in which the pressure relief apparatus fills a volume to compensate for a decrease in volume of target material within the cavity of the associated structure.

[0049] Fig. 12A is a flowchart of a procedure for regulating a pressure of a target material in a target material supply system that includes one or more unconfined zones and one or more confined zones. [0050] Fig. 12B is a flowchart of another procedure that can be used with the procedure of Fig. 12A for regulating the pressure of the target material in the target material supply system.

[0051] Fig. 13 is a block diagram of an extreme ultraviolet (EUV) light source including an implementation of the target material supply system, structure, and pressure relief apparatus of Fig. 1.

DESCRIPTION

[0052] Referring to Fig. 1, a target material supply system 100 is configured to deliver particles 103p of a target material 103 to a target space 124 inside an interior 122i of a chamber 122. The target material supply system 100 includes at least one structure 120 configured to retain the target material 103 within a cavity 120v defined by an interior surface 120s of a structure wall 120w of the structure 120. The structure 120 is a module that can include a single component, or it can be made of several interworking components. The structure 120 can be made of at least one rigid component. Moreover, any component of the structure 120 that is physically touching the fluid target material 103 is made of a material that is compatible with the target material 103. That is, such component of the structure 120 should be non-chemically reactive with the target material 103 and also able to withstand pressures and temperatures at which the target material 103 is maintained.

[0053] The target material supply system 100 can also include a target material source 105 configured to create fluid target material 103 from a solid target material, and a nozzle apparatus 107 configured to form and direct the particles 103p of the target material 103 toward the target space 124. The structure 120 is within a fluid flow path that is defined between the target material source 105 and the nozzle apparatus 107. In this way, the nozzle apparatus 107 and the target material source 105 are in fluid communication with the cavity 120v of the structure 120. In one example, the nozzle apparatus 107 and the target material source 105 can be directly connected to the structure 120 at respective connection regions. The target material 103 within the target material supply system 100 can be in a solid matter state or a fluid (such as liquid or gas) matter state at various locations or structures within the target material supply system 100. Thus, the target material 103 within the target material supply system 100 can, in one instant, be in a fluid state at some locations while in a solid state at other locations within the system 100. Moreover, the state of matter of the target material 103 can change at various locations and structures within the target material supply system 100. Thus, for example, the target material 103 at a particular structure within the system 100 might change its matter state from a fluid to a solid and then back to a fluid, depending on the time. [0054] The target material supply system 100 can include one or more other structures, such as structures 121_1, 121_2, that are in fluid communication with one or more of the target material source 105, the structure 120, and the nozzle apparatus 107 and that retain fluid target material 103. While only two other structures 121_1, 121_2 are shown in Fig. 1, there may be fewer or more than two such structures. The structures 121_1, 121_2 can be reservoir systems, fluid flow pipes, and/or demountable connections within the fluid path between the nozzle apparatus 107 and the target material source 105. Each of these structures (including the structure 120, 121_1 , 121_2) can have different thermal mass, and independent heating supply power. Moreover, during operation of the target material supply system 100, and at certain times, one or more of the structures 120, 121_1 , 121_2, the target material source 105, and the nozzle apparatus 107 can be heated or cooled. Because of the different surrounding environments and thermal masses, thermal gradients can be generated within the structure 120, or across different structures (such as the structures 121_1, 121_2) within the target material supply system 100. Additionally, the target material 103 that is within the nozzle apparatus 107 and the target material source 105 can be at lower temperatures than the cavity 120v of the structure 120 that retains the target material 103. Because the structures 121_1, 121_2, the nozzle apparatus 107, and the target material source 105 are in fluid communication with the cavity 120v of the structure 120, at these times, temperature gradients are formed between the cavity 120v, the structures 121_1, 121_2, the target material source 105, and the nozzle apparatus 107. These temperature gradients may result in the target material being solid in some areas of the system, whereas it could be liquid in other areas with a higher temperature. The areas where the target material is still solid can act as seals on the cavity 120v of the structure 120 (and on the structures 121_1, 121_2) that cause the pressure of the cavity 120v (and of respective cavities of the structures 121_1 , 121_2) to increase as the target material is heated up. The forces caused by this increased pressure can cause leaks at the fluid connection regions between the structure 120, the structures 121_1 , 121_2, the nozzle apparatus 107, and the target material source 105. When the target material 103 leaks at these fluid connection regions, it is necessary to manually replace components of the target material supply system 100, thereby causing down-time in which the target material supply system 100 cannot be operated.

[0055] Moreover, this increase in the pressure in the cavity 120v can be associated at least in part with a change in pressure of the target material 103 that is contained within the cavity 120v. Specifically, the target material 103 can expand within the cavity 120v (such as when changing state from a solid to a fluid such as a liquid), imparting forces on the structure wall 120w and on the fluid connection regions at which the structure 120 is fluidly connected to the structures 121_1 , 121_2, the nozzle apparatus 107, and/or the target material source 105. For example, if the target material 103 expands in volume by about 3%, this can cause the pressure in the cavity 120v to increase to greater than about 200 megapascals (MPa) and cause plastic deformation and even a structural failure of the system. [0056] In implementations in which the target material 103 is made of tin or a tin alloy, thermal gradients within the cavity 120v can lead to a temperature difference as large as 30 °C when the system is cooling down. Thus, volume reduction of tin during solidification (phase transition) in a colder area may be accommodated by the addition of tin from the area where it is at a higher temperature and still can flow. As a result of this, certain local regions of the system may be filled up with solid tin and also lack voids. During the heating cycle, if that local region heats faster than its neighboring regions or structures, due to thermal mass differences or uncontrolled heating, the volume of tin in the local region could increase a substantial amount (such as by 3%) upon melting, which produces extremely high pressure in excess of, for example, 200 MPa. Structures and regions that are fittings, such as joints that interconnect other assemblies or structures, are weak links in the fluid flow path from the target material source 105 to the nozzle apparatus 107, and the tin leaks in those fittings as soon as the pressure increases beyond the rating for that fitting. For example, in some fittings, the rating is as low as 80 MPa.

[0057] In view of the above issues with excess pressure that can be produced within the cavity 120v of the structure 120, a pressure relief apparatus 110 is associated with at least one structure 120. The pressure relief apparatus 110 is configured to relieve the pressure that is formed within the cavity 120v of the structure 120. Specifically, the pressure relief apparatus 110 enables the volume within the cavity 120v of the structure 120 to be changed or modified to account for pressure changes within the cavity 120v. For example, the pressure relief apparatus 110 is configured to increase the volume within the cavity 120v that is available for the target material 103 to thereby relieve an excessive increase in pressure within the cavity 120v. When the target material supply system 100 includes other structures, such as the structure 121_1 , 121_2, the pressure relief apparatus 110 can also be associated with these structures 121_1 , 121_2 to relieve an excessive increase in pressure within the respective cavities of the structures 121_1, 121_2.

[0058] Referring also to Fig. 2, the pressure relief apparatus 110 includes a passive pressure relief device 212 that includes a compressible mechanism 214. The compressible mechanism 214 is in fluid communication with the cavity 120v of the structure 120 and is configured to passively change the pressure in the cavity 120v of the structure 120. The action of the compressible mechanism 214 is passive in that it operates without an external source of energy. That is, the compressible mechanism 214 operates solely due to the changes of pressure within the cavity 120v to which it is fluidly coupled.

[0059] Specifically, and with reference to Fig. 3 A, the compressible mechanism 214 is configured to provide an additional volume that is configured to compensate the increase of the volume of the target material 103 upon heating up and melting in the cavity 120v of the structure 120, to passively change the pressure in the cavity 120v. In other words, when the pressure is increased in the cavity 120v (such as when the temperature in the cavity 120v is increased and the density of the target material 103 is reduced), the compressible mechanism 214 passively decreases the pressure in the cavity 120v by providing the additional volume in the cavity 120v where the target material 103 in the form or state of a fluid can expand.

[0060] In addition, at times during operation of the target material supply system 100, the pressure in the cavity 120v of the structure 120 is decreased such as when the temperature of the target material 103 is reduced or when fluid target material 103 (that is, target material in a fluid state) is flowed out of the cavity 120v, as shown in Fig. 3B. Specifically, the density of the target material 103 can increase as its temperature is reduced, and this drop in density causes a drop or a reduction in the volume of target material 103 within the cavity 120v. As such, the compressible mechanism 214 is also configured to recover its original shape and volume when this happens.

[0061] The pressure relief apparatus 110 is self-contained such that other components or structures of the target material supply system 100 are not affected by the increase or decrease in pressure in the cavity 120v. In this way, the pressure relief apparatus 110 passively mitigates the leaks that can be formed at the fluid connection regions between the structure 120 and other structures (such as the structures 121_1, 121_2) within the target material supply system 100, the nozzle apparatus 107, and/or the target material source 105, thereby increasing the time during which the target material supply system 100 can be operated.

[0062] Referring again to Fig. 1, in operational use, the nozzle apparatus 107 delivers a stream of the particles or targets 103p to the target space 124 along a path 126. The interaction of the particles 103p of the target material 103 with radiation pulses of the light beam 106 at the target space 124 creates a plasma 108 of the fluid target material 103 and produces extreme ultraviolet (EUV) light 109. For example, the light beam 106 can be generated by an optical source, and the EUV light 109 that is generated by the interaction between the light beam 106 and the particles 103p can be supplied to a lithography tool.

[0063] The particles 103p can be, for example, droplets of liquid or molten fluid target material 103, a portion of a liquid stream of the target material 103, solid particles or clusters formed from the target material 103, solid particles contained within liquid droplets of the target material 103, a foam produced from the target material 103, or solid particles contained within a portion of a liquid stream of the target material 103. The target material 103 is any material that radiates ultraviolet light (such as extreme ultraviolet light) when converted to a plasma state. The target material 103 can include, for example, water, tin, lithium, xenon, or a tin alloy. For example, the element tin can be used as pure tin (Sn); as a tin compound, for example, SnBr4, SnBrj, SnFU; as a tin alloy, for example, tin-gallium alloys, tin-indium alloys, tin-indium-gallium alloys; or any combination of these alloys. The particles 103p can be provided to the target space 124 by passing molten target material through the nozzle apparatus 107, and allowing the particles 103p to drift along the path 126 into the target space 124. In some implementations, the particles 103p can be directed to the target space 124 by force.

Additionally, the particle 103p that interacts with the radiation pulse of the light beam 106 can also have already interacted with one or more prior radiation pulses. Or, the particle 103p that interacts with the radiation pulse of the light beam 106 can reach the target space 124 without having interacted with any other radiation pulses.

[0064] Referring to Fig. 4, an implementation 410 of the pressure relief apparatus 110 (Figs. 1, 2, 3 A, and 3B) is associated with a structure 420. The structure 420 can be any of the structures 120, 121_1, 121_2, as shown in Fig. 1, and can be within the target material supply system 100. The structure 420 is configured to retain or contain the target material 103 within a cavity 420v (which can be within the target material supply system 100) defined by an interior surface 420s of a wall 420w of the structure 420. The structure 420 has a rectangular cross-sectional shape in the X-Y plane, and can be a rectangular tube that extends along the Z direction. The structure 420 can have other cross- sectional shapes like a circle such that the structure 420 is a cylindrical tube (as shown in Figs. 6A and 6B) or a polygon or an oval.

[0065] The pressure relief apparatus 410 is a passive pressure relief device that includes a compressible mechanism 414 that is in fluid and direct communication with the cavity 420v of the structure 420. The compressible mechanism 414 is a pressure relief component formed of a compressible material and the structure 420 is formed of a rigid material. One way to discuss the properties of the compressible material is to discuss its elastic modulus, which measures the compressible material’ s resistance to elastic deformation. The elastic modulus of the compressible material should be less than an elastic modulus of the structure 420. As an example, the compressible material of the compressible mechanism 414 has an elastic modulus that is below 6 GPa.

[0066] Additionally, because the compressible material is subjected to high temperatures within and/or above the melting range of the target material 103 during operation, the compressible material that forms the compressible mechanism 414 (that is the pressure relief component) is configured to remain in an elastic regime at temperatures greater than the melting range of the target material 103 or after being repeatedly compressed and decompressed. Deformation of the compressible material is not permanent; such that it can be decompressed after being compressed and vice versa. In this way, the compressible material remains in an elastic regime when maintained at a temperature that is above the melting range of the target material 103. For example, the compressible material can have an elastic modulus that remains below 6 GPa at operating temperatures, which can be temperatures within and/or above the melting range of the target material 103.

[0067] Moreover, the compressible material that forms the compressible mechanism 414 (which is the liner in this implementation) is compatible with the target material 103, such that the compressible material does not react with the target material 103 within the cavity 420v. For example, the compressible material can be a polymer material such as polyimide, polytetrafluoroethylene, polybenzimidazole, or polyether ether ketone. The compressible material can also be a rigid foam material with closed cells.

[0068] In this implementation, the compressible mechanism 414 (that is the pressure relief component) is a liner that covers at least a portion of the interior surface 420s of the structure 420 with which the pressure relief apparatus 410 is associated. In other words, the liner 414 (that is the pressure relief component) is disposed at the interior surface 420s of the structure 420. The liner 414 is configured to passively change the pressure within the cavity 420v by decreasing or increasing in volume as the pressure within the cavity 420v increases or decreases, respectively. For example, when the pressure in the cavity 420v is at a minimum value, the liner can occupy at least 50% of the volume of the cavity 420v of the structure 420 with which the pressure relief apparatus 410 is associated. In other words, a ratio of the volume of the liner 414 that covers the interior surface 420s of the structure 420 to the volume of the target material 103 contained within the cavity 420v of the structure can be at least 1. Thus, when the pressure in the cavity increases, the liner decreases in volume and occupies less than 50% of the volume of the cavity 420v, allowing the target material 103 (in the state of a fluid) to expand and occupy more than 50% of the volume of the cavity 420v. In another example, when the pressure in the cavity 420v is at a minimum value, the liner 414 can occupy at least 80%, or about 90%, of the cavity 420v of the structure 420.

[0069] Additionally, the ratio of the volume of the compressible material that forms the compressible mechanism 414 (that is the pressure relief component) to the volume of the fluid target material 103 contained within the cavity 420v of the structure 420 can be related (either directly or indirectly) to an elastic modulus of the compressible material that forms the compressible mechanism 414. As such, if the value of this ratio is lower, the elastic modulus of the compressible material should also be lower. [0070] In one example, the compressible material is polyimide such that the liner 414 is formed of polyimide and the structure 420 is formed of molybdenum. In this example, the volume of the liner 414 occupies at least 80%, or about 90%, of the cavity 420v of the structure 420 and the volume of the target material 103 occupies the rest of the cavity 420v of the structure 420. The polyimide liner 414 experiences elastic deformation as the polyimide compresses and decompresses as it changes in volume due to the change in pressure in the cavity 420v during operation. In other words, the polyimide liner 414 decompresses or returns to its original state after the polyimide is compressed to a deformed state (due to the change in pressure within the cavity 420v), and does not experience permanent deformation. In addition, the polyimide liner 414 does not experience plastic deformation as the polyimide is subjected to cyclic loading (as the polyimide cyclically compresses and decompresses) due to the changes in pressure within the cavity 420v.

[0071] It should be pointed out that the same mechanism of reduction of pressure in the cavity 420v can be accomplished with a smaller relative volume of the liner material, where the stress associated with the increase in the volume of the target material 103 can be accommodated by the deformation of the liner 414 that has both the elastic and plastic components. The downside of allowing a plastic deformation of the liner material is that over time, with increased number of heating up/cooling down cycles the maximum pressure that is produced in the cavity 420v is increased, as the ratio of the volume of the liner 414 to that of the target material 103 is reduced with each cycle. [0072] During operation, the liner 414 (that is the pressure relief component) passively prevents the pressure in the cavity 420v from exceeding a maximum allowed value. The maximum allowed value can correlate to a value of pressure at which leaks can occur at connection regions of the structure 420. For example, if the structure 420 is within the target material supply system 100 and is connected to one or more other structures (such as the structures 121_1, 121_2 in Fig. 1) at these connection regions, the maximum allowed value can be less than the value of the pressure at which leaks begin to occur at the connection regions between the structures (including the structure 420).

[0073] The maximum allowed pressure value in the area of the system that is physically located away from the connections (for example, in a pipe delivering tin from one element to another element of the system) can correlate to a burst pressure of this structure that is determined at the system operating temperature.

[0074] Referring also to Fig. 5A, when the pressure in the cavity 420v is increased (such as when the temperature in the cavity 420v is increased and the density of the target material 103 is reduced), the liner 414 passively decreases the pressure in the cavity 420v by increasing the effective volume of the cavity 420v. Specifically, the liner 414 (that is formed of the compressible material) passively compresses toward the interior surface 420s of the cavity 420 (shown by arrows in Fig. 5A), which reduces the volume of the liner 414 to thereby increase the volume of the cavity 420v. In other words, the compressible material that forms the liner 414 non-permanently deforms when the compressible material is subjected to an increasing pressure. In this way, the fluid target material 103 (the target material 103 in the form of a fluid) is allowed to expand into a larger volume, which decreases the potential energy in the fluid target material 103 that is within the cavity 420v. As such, the pressure in the cavity 420v is passively decreased and does not exceed the maximum allowed value at which leakage can occur.

[0075] Referring also to Fig. 5B, when the pressure in the cavity 420v is decreased (such as when the temperature in the cavity 420v is decreased and the density of the target material 103 is increased), the cavity 420v is not required to have the larger volume because the pressure in the cavity 420v is significantly less than the maximum allowed value (at which leakage can occur). As such, the liner 414 passively decreases the volume of the cavity 420v. Specifically, the liner 414 (that is formed of the compressible material) passively expands away from the interior surface 420s of the cavity 420 (shown as arrows in Fig. 5B), which increases the volume of the liner 414. In other words, the compressible material that forms the liner 414 expands (and non-permanently deforms) when the compressible material is decompressed.

[0076] Because the compressible material compresses and decompresses as it changes in volume due to the change in pressure in the cavity 420v during operation, the compressible material that forms the compressible mechanism 414 (that is the pressure relief component) is configured to remain in a linear elastic regime after being repeatedly compressed and decompressed. In other words, the compressible material experiences elastic deformation. The compressible material decompresses or returns to its original state after the compressible material is compressed to a deformed state (due to the change in pressure within the cavity 420v), and does not experience permanent deformation. Further, the compressible material is subjected to high pressures when the pressure in the cavity 420v is increased during operation. For example, the high pressure in the cavity 420v can be greater than 20 Megapascals (MPa). As such, the compressible material is configured to remain in the elastic regime at pressures greater than this high pressure.

[0077] Referring to Figs. 6A and 6B, an implementation 620 of the structure 420 is associated with a pressure relief apparatus 610 that includes an implementation 614 of the compressible mechanism 214 or 414. The structure 620 is a hollow cylindrical tube that has a cylindrical cavity 620v defined by an interior surface 620s of a wall 620w of the cylindrical structure 620. The cylindrical structure 620 has a circular cross-section in the X-Y plane and longitudinally extends along the Z direction. The cavity 620v retains the target material 103. In this implementation, the compressible mechanism 614 is a liner (similar to the liner 414 of Figs. 4, 5A, and 5B). The liner 614 covers at least a portion of the interior surface 620s of the cylindrical structure 620. As such, the liner 614 has a cylindrical shape that matches the cylindrical shape of the interior surface 620s. The liner 614 is in fluid communication with the cavity 620v and passively changes the pressure in the cavity 620v.

[0078] The cylindrical structure 620 can be in the target material supply system 100 (Fig. 1). For example, any one of the structures 120, 121_1 , 121_2 can be the cylindrical structure 620. Moreover, the cylindrical structure 620 can be configured to transfer the target material 103 (while it is in the form or state of a fluid) between any two of the structures 120, 121_1, 121_2, the target material source 105, and the nozzle apparatus 107. In other words, the cylindrical structure 620 can act as a pathway or pipe that transfers the fluid target material 103 between regions of the target material supply system 100 during operation. As such, the cylindrical structure 620 includes an inlet 623i configured to receive the fluid target material 103 from a first region in the target material supply system 100 and an outlet 623o configured to send the fluid target material 103 to a second region in the target material supply system 100. The cylindrical structure 620 can be fluidly connected to or mounted to any one of the structures or components in the target material supply system 100 (including the structures 120, 121_1 , 121_2, the target material source 105, and the nozzle apparatus 107) at each of the inlet 623i and the outlet 623o of the cylindrical structure 620.

[0079] During operation, the fluid target material 103 moves in a direction 623d into the inlet 623i, through the cavity 620v in the direction 623d, and out of the outlet 623o in the direction 623d, the direction 623d being parallel with the longitudinal direction Z. The liner 614 passively stores energy associated with an increase in the pressure in the cavity 620v to passively change the pressure in the cavity 620v. When the pressure in the cavity 620v is increased, the liner 614 compresses to thereby increase the volume within the cavity 620s. For example, the liner 614 can compress radially toward the interior surface 620s, as shown by line 611 with arrows along the Y direction in Fig. 6A. As another example, if gaps are formed between the liner 614 and the interior end surfaces 620e, then the liner 614 can also compress along the longitudinal direction (the Z direction in Fig. 6A). Thus, the fluid target material 103 can expand and the pressure in the cavity 620s is reduced. When the pressure in the cavity 620v is decreased, the liner 614 expands and moves (for example, radially away from the interior surface 620s and/or longitudinally away from the interior end surfaces 620e) to thereby decrease the volume within the cavity.

[0080] Moreover, in other implementations, any of the compressible elements that are associated with a pressure relief apparatus can be other shapes. For example, any of the compressible elements can have a solid cylindrical shape with one or more grooves at an outer side of the cylindrical shape, such grooves extending longitudinally/axially along the cylindrical shape, providing the path for the target material 103. Such a design is shown in Fig. 6C, in which the liner 614 includes grooves 614g that extend along the Z direction and face the interior surface 620s. In these implementations, the target material 103 is able to take up the volume defined between the liner 614 and the interior surface 620s. When the pressure in this volume is increased, the liner 614 compresses to provide extra volume for the target material 103 to expand. For example, the liner 614 can compress radially away from the interior surface 620s (as shown in Fig. 6D) and/or it can compress longitudinally along the Z direction, as discussed above. The compressible elements can have the shape of a liner such as the liner 614 in Fig. 6B, with one or more grooves extending outwardly from an inner side of the cylindrical shape of the liner 614, such grooves extending longitudinally/axially along the cylindrical shape, providing the path for the target material 103.

[0081] Referring also to Fig. 7, in some implementations, the cylindrical structure 620 is fluidly connected to a structure 720_l that is a demountable connection at the outlet 623i of the cylindrical structure 620. Furthermore, the demountable connection 720_l is fluidly connected to another structure 720_2 that is another hollow cylindrical tube or pipe. In these implementations, the demountable connection 720_l can be a pipe fitting or pipe connector configured to connect two pipes, such as, for example, a coupling fitting, an adaptor fitting, a bushing fitting, or a union fitting. The cylindrical structures 620 and 720_2 are separate and distinct structures connected to one another by the demountable connection 720_l. In some implementations, the structures 620, 720_2 are within the target material supply system 100 (Fig. 1). In such implementations, any two adjacent structures in the target material supply system 100 (including the structures 120, 121_1 , 121_2) can be the cylindrical structures 620, 720_2. Each of the cylindrical structures 620, 720_2 can be a fluid device and/or be configured to transfer the fluid target material 103 between any other two structures or components (including the target material source 105 and the nozzle apparatus 107) in the target material supply system 100.

[0082] The structure 720_2 has a cylindrical cavity 720v_2 defined by an interior surface 720s_2 of the cylindrical structure 720_2. The cylindrical structure 720_2 has a circular cross-section in the X-Y plane and it longitudinally extends along the Z direction (similar to the cross-section of the cylindrical structure 620 shown in Fig. 6B). The cavity 720v_2 also retains the target material 103. In this implementation, a pressure relief apparatus 710_2 is associated with the structure 720_2. As such, the cylindrical structure 720_2 is also at least partially covered by a liner 714_2 (that is part of the pressure relief apparatus 710_2 and acts as a compressible mechanism 714_2) at the interior surface 720s_2 of the cylindrical structure 720_s. The liner 714_2 is in fluid communication with the cavity 720v_2 and passively changes the pressure in the cavity 720v_2. The cylindrical structure 720_2 also includes an inlet 723i_2 configured to receive the fluid target material 103 from the structure 620 through the demountable connection 720_l and an outlet 723o_2 configured to send the fluid target material 103 to another region in the target material supply system 100.

[0083] The demountable connection 720_l has a cavity 720v_l defined by an interior surface 720s_l of the demountable connection 720_l. The cross-section of the demountable connection 720_l can also be circular, or another shape such as, for example, rectangular or hexagonal. The cavity 720v_l also retains the target material 103. The demountable connection 720_l is associated with a pressure relief apparatus 710_l that includes a compressible mechanism 714_1. In this example, the compressible mechanism 714_1 is a liner. The liner 714_1 is in fluid communication with the cavity 720v_l and passively changes the pressure in the cavity 720v_l when the fluid target material 103 passes through the demountable connection 720_l from the cylindrical structure 620 to the cylindrical structure 720_2.

[0084] During operation, the fluid target material 103 moves in a direction 723d that is parallel with the longitudinal Z direction into the inlet 623i of the cylindrical structure 620, through the cavity 620v, and into the cavity 720v_l of the demountable connection 720_l through the outlet 623o. The fluid target material 103 then moves through the cavity 720v_l of the demountable connection 720_l and into the cavity 720v_2 of the cylindrical structure 720_2 through the inlet 723i_2 of the cylindrical structure 720_2. The fluid target material 103 then moves in the direction 723d out of the cavity 720v_2 through the outlet 723i_2 of the cylindrical structure 720_2, thereby transferring the target material 103 from a first region (at the inlet 623i) to a second region (at the outlet 723i_2) within the target material supply system 100.

[0085] Each of the liners 614, 714_1, 712_2 are present to avoid high pressure generation when the target material 103 is melted (from a solid state to a fluid or liquid state). As an example, when the cylindrical structures 620, 720_2 are at a temperature below the melting range of the target material 103 and the target material 103 is melted (from the solid target material) within the demountable connection 720_l, the fluid target material 103 within the demountable connection 720_l is prevented from expanding into these neighboring structures 620, 720_2. As such, the liner 714_1 is configured to passively compress relative to the interior surface 720s_l, which changes the volume of the liner 714_1 to thereby passively change the volume of the cavity 720v_l and allow the fluid target material 103 to expand. For example, the liner 714_1 can compress along a radial direction, as shown by a line with arrows 711_1 along the Y direction associated with the structure 720_l in Fig. 7. In addition, the liner 714_1 can compress longitudinally, such as, if the fluid target material 103 has penetrating gaps between the liner 714_1 and interior end surfaces 720e_2 of the structure 720_2.

[0086] Similarly, at certain times when either of the structures 620, 720_2 are surrounded by structures that have a temperature below the melting range of the target material 103 and the target material 103 is melted in either of the structures 620, 720_l, each of the liners 614, 714_2 are configured to passively compress relative to each respective interior surface 620s, 720s_2 (shown by lines with arrows 611, 711_2 along the Y direction associated with respective structures 620, 720_2 in Fig. 7) or relative to interior end surfaces 720e_2, which changes the volume of each liner 614, 714_2 to thereby passively change the volume of each respective cavity 620v, 720v_2 and allow the fluid target material 103 to expand. In this way, high pressure generation within the target material supply system 100 is avoided and damage to the target material supply system 100 is prevented or mitigated as the target material 103 is melted in various structures (including the structures 620, 720_l, 720_2) of the target material supply system 100.

[0087] In other implementations, a pressure relief apparatus (such as the pressure relief apparatuses 610, 710_l, 710_2) can be associated with other cylindrical structures that are hollow cylindrical tubes having a cylindrical cavity that transfers the fluid target material 103. For example, the target material supply system 100 can include several cylindrical structures that each act as a pipe that are involved in the transfer of the target material 103 from the target material source 105 to the nozzle apparatus 107, and a pressure relief apparatus can be associated with each of the hollow cylindrical tubes. Moreover, each of the cylindrical structures within the target material supply system 100 can be fluidly connected to each of the one or more adjacent cylindrical structures by a demountable connection (such as the demountable connection 720_l). Each demountable connection can be associated with another pressure relief apparatus that includes another passive relief device including another compressible mechanism (such as the liner 710_l). In these implementations, the demountable connection can be a pipe fitting or pipe connector configured to connect more than two pipes at a connection region, such as, for example, a tee fitting, a wye fitting, a cross fitting, or an elbow fitting.

[0088] In another example, any of the compressible elements can have a rectangular bar shape (such that the cross-section of the compressible element has a rectangular shape). In this example, the compressible element fills at least a portion of the interior surface of the cylindrical structure and can extend longitudinally/ axially along the interior surface of the structure. In other examples, any of the compressible elements can have a hexagonal bar shape, or any other polygonal bar shape. In these examples, the compressible element may or may not have a cross-sectional shape that matches the cross-sectional shape of the interior surface of the structure. Any of these other shapes can also have one or more grooves at a side of the shape that extends along the shape.

[0089] Referring to Fig. 8, an implementation 810 of the pressure relief apparatus 110 (Figs. 1, 2, 3 A, and 3B) is associated with the structure 420. The structure 420 can be any of the structures 120, 121_1, 121_2 (Fig. 1) or the cylindrical structures 620, 720_l, 720_2 (Figs. 6A, 6B, and 7). Furthermore, the structure 420 can be within the target material supply system 100. As described above, the structure 420 retains or contains the fluid target material 103 within the cavity 420v that is defined by the interior surface 420s of the structure 420.

[0090] The pressure relief apparatus 810 is a passive pressure relief device that includes a compressible mechanism 814 that is in fluid and direct communication with the cavity 420v of the structure 420. In this implementation, the compressible mechanism 814 is an inert gas formed as a bubble within the target material 103. The inert gas 814 is configured to passively change the pressure within the cavity 420v. The inert gas 814 is a gas that does not react with the target material 103. For example, the inert gas 814 can be argon (Ar), xenon (Xe), helium (He), nitrogen (Nj), hydrogen (Hz), or carbon monoxide (CO). The inert gas 814 occupies a portion of the cavity 420v that allows the inert gas 814 to sufficiently reduce the pressure in the cavity 420v when the pressure in the cavity 420v increases during operation, which can be caused by a decrease in density of the target material 103 as the temperature of the target material 103 increases (such as when the target material 103 changes from a solid to a liquid and/or as the temperature of the liquid increases). Moreover, the volume of the inert gas 814 does not lead to an appreciable increase in the total volume within the target material supply system 100 that can lead to detrimental effects within the target material supply system 100. For example, the inert gas 814 can occupy about 2% to about 10% of the cavity 420v of the structure 420 with which the pressure relief apparatus 810 is associated.

[0091] During operation, the inert gas 814 passively changes the pressure within the cavity 420v by reducing its volume in response to a pressure that is increasing as a result of the target material 103 expansion in the cavity 420v of the structure 420. Referring also to Fig. 9A, when the pressure in the cavity 420v is increased (such as when the temperature in the cavity 420v is increased and the density of the target material 103 is reduced), the inert gas 814 passively decreases the pressure in the cavity 420v by compressing and increasing the available volume of the cavity 420v, where the available volume in the cavity 420v is the volume outside the bubble of the inert gas 814. Specifically, the inert gas 814 that is the fluid gas bubble passively compresses by decreasing in volume (shown with arrows in Fig. 9A) and increasing in density, which thereby increases the available volume of the cavity 420v. In this way, the fluid target material 103 (that is, the target material 103 in the form of a fluid) is allowed to expand into a larger volume, which decreases the energy in the fluid target material 103 that is within the cavity 420v. As such, the pressure in the cavity 420v is passively decreased or maintained.

[0092] Referring also to Fig. 9B, when the pressure in the cavity 420v is decreased (such as when the temperature in the cavity 420v is decreased and the density of the target material 103 is increased), the cavity 420v is not required to have the larger volume. As such, the inert gas 814 that is the fluid gas bubble passively decreases the available volume of the cavity 420v by expanding or increasing in volume (shown with arrows in Fig. 9B) and decreasing in density. In this way, the inert gas 814 releases the energy back into the target material 103 that is within the cavity 420v.

[0093] Referring to Figs. 9C and 9D, the inert gas 814 can also be implemented when an external force F, such as a gravity force and/or another force, is acting on the structure 420. In this example, the external force F is along the negative Y direction. The inert gas 814 is formed as a gas bubble inside an extended portion 420e of the structure 420. The extended portion 420e of the structure acts as a pocket (or additional volume) for the inert gas 814 to occupy. Because the inert gas 814 has a lower density than the target material 103 within the cavity 420v, the inert gas 814 floats or rises in the positive Y direction (that is opposite to the direction of the external force F) to the top of the available volume within the cavity 420v (which is the portion of the cavity 420v associated with the extended portion 420e of the structure 420).

[0094] With reference to Fig. 9C, as similarly described in Fig. 9A, when the pressure in the cavity 420v is increased (such as when the temperature in the cavity 420v is increased and the density of the target material 103 is reduced), the inert gas 814 passively decreases the pressure in the cavity 420v by compressing (shown with an arrow in Fig. 9C) which increases the available volume of the cavity 420v, where the available volume in the cavity 420v is the volume below or outside of the bubble of the inert gas 814. As such, the pressure in the cavity 420v is passively decreased or maintained when the external force F is also acting on the structure 420. With reference to Fig. 9D, as similarly described in Fig. 9B, when the pressure in the cavity 420v is decreased (such as when the temperature in the cavity 420v is decreased and the density of the target material 103 is increased), the inert gas 814 that is the fluid gas bubble passively decreases the available volume of the cavity 420v by expanding or increasing in volume (shown with an arrow in Fig. 9D) and decreasing in density.

[0095] In implementations that include more than one structure (such as the structures 120, 121_1, 121_2, 620, 720_l, 720_2) in the target material supply system 100, the pressure relief apparatus 810 can be associated with any one or more of the structures 120, 121_1, 121_2, 620, 720_l, 720_2. Specifically, the inert gas 814 can be formed as more than one gas bubble, each gas bubble being formed inside each cavity of each respective structure with which the pressure relief apparatus 810 is associated. In this way, the inert gas 814 formed as gas bubbles in the cavities can passively change the pressure within each of the cavities of the structures during operation.

[0096] Referring to Fig. 10, another implementation 1010 of the pressure relief apparatus 110 (Figs. 1, 2, 3 A, and 3B) is associated with the structure 420. The structure 420 can be any of the structures 120, 121_1, 121_2 (Fig. 1) or the cylindrical structures 620, 720_l, 720_2 (Figs. 6A, 6B, and 7). Moreover, the structure 420 can be within the target material supply system 100. As described above, the structure 420 retains or contains the target material 103 within the cavity 420v that is defined by the interior surface 420s of the structure 420.

[0097] The pressure relief apparatus 1010 includes a passive pressure relief device 1012 that includes a compressible mechanism 1014 that is in fluid and direct communication with the cavity 420v of the structure 420. In this implementation, the passive pressure relief device 1012 is a pressure relief valve 1012 and the compressible mechanism 1014 is a mechanical spring configured to passively change the pressure in the cavity 420v. The pressure relief valve 1012 remains closed as the pressure changes in the cavity 420v. In other words, the pressure relief valve 1012 remains separated and isolated from an external environment outside of the cavity 420v.

[0098] Specifically, the pressure relief valve 1012 includes a valve body 1012b that surrounds or supports the mechanical spring 1014, a cap 1012c attached to the valve body 1012b and configured to maintain closure of the pressure relief valve 1012 by acting as a stop for one end of the mechanical spring 1014, and a valve seat 1012s configured to move along the Y direction as the pressure changes in the cavity 420v. The mechanical spring 1014 is loaded between the cap 1012c and the valve seat 1012s such that the mechanical spring 1014 compresses when the valve seat 1012s moves in the positive Y direction and decompresses when the valve seat 1012s moves in the negative Y direction. The pressure relief valve 1012 and the mechanical spring 1014 are each made of a material that is compatible with the target material 103 at associated temperatures and pressures above the melting range of the target material 103. In addition, the material of the pressure relief valve 1012 (including the valve seat 1012s and the mechanical spring 1014) does not react with the target material 103. For example, the material of the pressure relief valve 1012 can be a refractory metal or a ceramic material. [0099] During operation, the mechanical spring 1014 passively changes the pressure within the cavity 420v by deforming elastically and providing an added volume in the cavity 420v of the structure 420. Referring also to Fig. 11 A, when the pressure in the cavity 420v is increased (such as when the temperature in the cavity 420v is increased and the density of the target material 103 is reduced), the mechanical spring 1014 passively decreases the pressure in the cavity 420v by increasing the available volume of the cavity 420v. Specifically, the valve seal 1012s is forced along the positive Y direction by the increasing pressure in the cavity 420v thereby compressing the mechanical spring 1014 (shown with an arrow in Fig. 11 A) and increasing the available volume of the cavity 420v. In this way, the fluid target material 103 is allowed to expand into a larger volume, which decreases the energy in the fluid target material 103 that is within the cavity 420v. As such, the pressure in the cavity 420v is passively decreased. Moreover, the mechanical spring 1014 can store this energy (and the cap 1012c remains closed) such that the energy is not lost to an external environment outside of the cavity 420v.

[0100] Referring also to Fig. 1 IB, when the pressure in the cavity 420v is decreased (such as when the temperature in the cavity 420v is decreased and the density of the target material 103 is increased), the cavity 420v is not required to have the larger volume. Because the valve seal 1012s is not being forced along the positive Y direction, the mechanical spring 1014 decompresses and the valve seal 1012s moves along the negative Y direction (shown with an arrow in Fig. 1 IB) to thereby passively decrease the volume of the cavity 420v. In this way, the mechanical spring 1014 releases the energy back into the target material 103 that is within the cavity 420v. [0101] In implementations that include more than one structure (such as the structures 120, 121_1, 121_2, 620, 720_l, 720_2) in the target material supply system 100, the pressure relief apparatus 1010 can be associated with any one or more of the structures 120, 121_1, 121_2, 620, 720_l, 720_2. For example, the pressure relief valve 1012 can be a tee connector with a ball check valve that fluidly connects two adjacent structures in the target material supply system 100.

[0102] Referring to Fig. 12A, a procedure 1240 is performed for regulating a pressure of the target material 103 in a target material supply system. The procedure can be performed with respect to the target material supply system 100 (Fig. 1) that can include one or more of the structures 120, 121_1, 121_2, the structure 420 (Figs. 4, 8, and 10), and the cylindrical structures 620, 720_l, 720_2 (Figs. 6 A, 6B, and 7). Each of the structures in the target material supply system 100 can be associated with a pressure relief apparatus (including, for example, the pressure relief apparatuses 110, 410, 610, 710_l, 710_2, 810, 1010), but are not required to be associated with a pressure relief apparatus in order for the procedure 1240 to be performed. In the following, the procedure 1240 is discussed with respect to the target material supply system 100 including the target material source 105, the nozzle apparatus 107, and the structures 120, 121_1, 121_2 (Fig. 1). The procedure 1240 can be performed whenever one or more portions of or the entire target material supply system 100 needs to be heated to thereby melt the target material 103 in the form of solid matter within the portions or in the target material supply system 100 to form the fluid target material 103 (that is, target material 103 in the form of a fluid or liquid). In general, the target material supply system 100 includes a set of zones, each zone being defined by its own heaters and independent temperature control. At any particular moment in time, the target material supply system 100 can include one or more unconfined zones and one or more confined zones.

[0103] An unconfined zone is a zone defined by an open cavity that allows the pressure of the target material 103 to be released when a temperature of that unconfined zone is greater than a melting range of the target material 103. An open cavity is a cavity that is fluidly coupled to another volume outside the unconfined zone, and, moreover, pressure within the unconfined zone can be released to the other volume. A confined zone is defined by a closed cavity, that is, a volume that is (for example, temporarily) not fluidly coupled to another volume outside the cavity. The cavity can be closed by solid target material 103 that is contained on each side of the zone, acting as a high pressure seal. Each of the one or more confined zones and the one or more unconfined zones can be defined as a separate and distinct structure (such as the structures 120, 121_1 , 121_2, structures within the target material source 105, and structures within the nozzle apparatus 107).

[0104] Because the unconfined zones are defined by open cavities, the fluid target material 103 is able to expand into the open volumes of each open cavity as the temperature in each unconfined zone is increased to a temperature greater than the melting range of the target material 103 because the pressure that builds from the expanding volume of the fluid target material 103 can escape to another volume outside the unconfined zone. In this way, the pressure of the target material 103 is automatically regulated when the temperature of each unconfined zone is greater than the melting range of the target material 103.

[0105] Because the confined zones are defined by closed cavities, the fluid target material 103 is not allowed to expand into open volumes. As such, when the target material 103 is increased to the temperature greater than the melting range of the target material 103 within the closed cavities of the confined zones, the pressure of the target material 103 cannot be regulated without expanding into at least one adjacent zone (which each must be at the temperature greater than the melting range of the target material 103 in order for the fluid target material 103 to expand to thereby regulate the pressure in the closed cavities).

[0106] The procedure 1240 includes identifying one or more unconfined zones (1241). For example, the target material source 105 can include at least one structure that is an unconfined zone, such as a target material reservoir configured to hold the target material 103. Specifically, the target material reservoir includes an open volume within a cavity of the target material reservoir that allows the fluid target material 103 to expand when the temperature of the target material reservoir is greater than the melting range of the target material 103. The target material reservoir can also be configured to create the fluid target material 103 from a solid target material. As such, the target material reservoir in the target material source 105 can be identified as the unconfined zone.

[0107] Next, the target material 103 is melted in at least one of the identified unconfined zones such that the at least one unconfined zone has a temperature greater than the melting range of the target material 103 (1242). For example, the unconfined zone can be identified as the target material reservoir in the target material source 105 configured to create the fluid target material 103 from a solid target material and hold the fluid target material 103. Specifically, the solid target material in the target material reservoir (that is the unconfined zone) can be melted by heating the solid target material (to thereby create the fluid target material 103) such that the target material 103 expands into the open cavity of the target material reservoir (that is the unconfined zone) to regulate the pressure of the target material in the target material reservoir.

[0108] In this way, the temperature of the target material reservoir (that is the unconfined zone) has a temperature greater than the melting range of the target material, and the pressure of the fluid target material 103 within the cavity of the target material reservoir is regulated by allowing the target material to expand into the open volume of the cavity of the target material reservoir. Furthermore, leaks within the target material supply system 100 that can occur due to unregulated pressures of the fluid target material 103 (that can exceed a maximum allowed value) are mitigated.

[0109] Next, a cold confined zone is identified (1243). A cold confined zone is a confined zone having a temperature less than the melting range of the target material 103. Once the cold confined zone is identified (1243), then a determination is made as to whether the identified cold confined zone is adjacent to at least one of the unconfined zones that has a temperature greater than the melting range of the target material 103 (1244). If the cold confined zone is adjacent to an unconfined zone having a temperature greater than the melting range of the target material 103 (1244), then the target material 103 within that cold confined zone is melted (1245). If there are other cold confined zones (1246), then the steps 1243, 1244, 1245 are repeated for each of those other cold confined zones until all of these cold confined zones are heated and the target material 103 is melted.

[0110] For example, the confined zones can be the structures 120, 121_1, 121_2 and the nozzle apparatus 107. Each of the structures (such as the structures 120, 121_1, 121_2) that is a confined zone defined by a closed cavity can be one of a pipe configured to transfer the target material 103 between other structures, a freeze valve configured to separate two or more of the other structures, and a droplet generator assembly configured to create particles (such as the particles 103p) in the form of droplets of the target material 103. Moreover, the nozzle apparatus 107 can include a structure defined as a confined zone. The nozzle apparatus 107 includes a nozzle that can be considered as an unconfined zone, the nozzle being configured to direct the particles 103p of the target material 103 to interact with a light beam (such as the light beam 106 inside the interior 122i of the chamber 122) that irradiates the particles 103p into a plasma state (such as the plasma 108), thereby producing EUV light (such as the EUV light 109).

[0111] In one example, the structure 121_1 can be a freeze valve in the target material supply system 100 that separates the target material reservoir in the target material source 105 from the structure 120. The structure 120 can be a pipe (similar to the hollow cylindrical structure 620 of Figs. 6A and 6B) that transfers the target material 103 from the target material reservoir in the target material source 105 to the structure 121_2. The structure 121_2 can be a droplet generator assembly that receives the target material 103 through the pipe 120 and creates the particles 103p of the target material 103. The nozzle in the nozzle apparatus 107 can receive the target material 103 from the droplet generator assembly 121_2 and direct the particles 103p along the path 126 to the target space 124 to interact with the light beam 106.

[0112] Thus, in this example, when the target material reservoir (that is an unconfined zone) in the target material source 105 has a temperature greater than the melting range of the target material 103 (for example, by melting the target material 103 to create a fluid in Step 1243), the target material 103 can be melted in the freeze valve 121_1 because the freeze valve 121_1 is now becoming an unconfined zone. The target material 103 in the freeze valve 121_1 can be heated (to melt the target material) such that the target material 103 is allowed to expand into the adjacent unconfined zone (which is the target material reservoir) to thereby regulate the pressure of the target material 103 in the freeze valve 121_1.

[0113] In other words, the procedure 1240 allows each cold confined zone of the target material supply system 100 to be heated such that each cold confined zone is only heated when the cold confined zone is not entirely blocked by other zones that include solid target material 103, which prevents expansion of the target material 103. In this way, leaks within the target material supply system 100 that can occur due to unregulated pressures of the fluid target material 103 (that can exceed a maximum allowed value) are mitigated or reduced, and the target material supply system 100 can be operated for longer durations of time.

[0114] Referring also to Fig. 12B, in some implementations, the procedure 1240 can further include additional steps that are performed after step 1244 if it is determined at step 1244 that the cold confined zone is not adjacent to an unconfined zone having a temperature greater than the melting range of the target material 103. Specifically, the procedure 1240 can include a determination as to whether the cold confined zone is adjacent to at least one of the confined zones that has a temperature greater than the melting range of the target material 103 (1247), and if so, then the target material 103 within that cold confined zone is melted (1248) prior to returning to step 1246.

[0115] In the example described above, when the target material reservoir in the target material source 105 and the freeze valve 121_1 have temperatures greater than the melting range of the target material 103, the target material 103 can be melted in one or more of the other confined zones that have temperatures less than the melting range of the target material 103 if the one or more other confined zones are adjacent to either one of the target material reservoir or the freeze valve. Specifically, with respect to the target material supply system 100 of Fig. 1, the target material 103 can be melted in the pipe 120 (that is a confined zone) because the pipe 120 is adjacent to the freeze valve 121_1 (that is a confined zone) that has a temperature greater than the melting range of the target material 103. If more than one confined zone (that is a separate structure, not shown) adjacent to the freeze valve 121_1 is also included in the target material supply system 100, the target material 103 in these other adjacent confined zones can additionally be melted when the temperature of the freeze valve 121_1 is greater than the melting range of the target material 103.

[0116] Furthermore, in this example, when the target material reservoir (in the target material source 105), the freeze valve 121_1 , and the pipe 120 have temperatures greater than the melting range of the target material 103, the target material 103 can then be melted in the droplet generator assembly 121_2 (that is a confined zone adjacent to the pipe 120) such that the droplet generator assembly also has a temperature greater than the melting range of the target material 103. Next, after the target material reservoir, the freeze valve 121_1 , the pipe 120, and the droplet generator assembly 121_2 have temperatures greater than the melting range of the target material 103, then the nozzle in the nozzle apparatus 107 can also be heated to a temperature above the melting range of the target material 103. Because the target material 103 is melted in all zones before being melted in the nozzle apparatus 107, the target material 103 can be properly controlled by the nozzle. In this way, the target material 103 can be melted in the confined zones by heating the target material 103 in each of the confined zones (that have a temperature less than the melting range of the target material 103) in a sequence such that each confined zone is adjacent to at least one of the unconfined zones and/or confined zones that has a temperature greater than the melting range of the target material 103 at each step of the sequence. Thus, leaks within the target material supply system 100 that can occur due to unregulated pressures of the fluid target material 103 (that can exceed a maximum allowed value) are mitigated or reduced by regulating the pressure in each of the confined zones at each step of the sequence.

[0117] In further implementations, the procedure 1240 can be performed when at least one of the structures 120, 121_1, 121_2, the target material source 105, and the nozzle apparatus 107 is also associated with a pressure relief apparatus. In the example of Fig. 1, the structure 120 is associated with the pressure relief apparatus 110. As such, when the structure 120 is heated using the procedure 1240, the compressible mechanism 214 (Fig. 2) of the pressure relief apparatus 110 can additionally passively change (and regulate) the pressure in the cavity of the structure 120 by expanding the volume of the cavity. This allows the fluid target material 103 to simultaneously expand into a larger volume within the cavity of the structure 120 and expand into at least one of the adjacent structures 121_1 , 121_2 that has a temperature greater than the melting range of the target material 103. In this way, leaks within the target material supply system 100 that can occur due to unregulated pressures of the fluid target material 103 are further mitigated or reduced.

[0118] Referring to Fig. 13, an implementation 1360 of an EUV light source is shown, in which the EUV light source 1360 includes an implementation 1300 of the target material supply system 100. The EUV light source 1360 includes an implementation 1322 of the chamber 122. The target material supply system 1300 includes at least one structure (such as the structure 120 in the target material supply system 100, or any of the other structures disclosed here) 1320, the structure 1320 configured to retain target material 1303. A pressure relief apparatus 1310 is associated with the structure 1320, as discussed above with reference to the pressure relief apparatus 110. The target material supply system 1300 includes a target material source 1305 configured to create the fluid target material 1303 from a solid material 1361, and a nozzle apparatus 1307 configured to form and direct particles 1303p of the target material 1303 through a capillary device 1363. The pressure relief apparatus 1310 can be associated with a structure 1320 within the target material source 1305, within the nozzle apparatus 1307, or within other components (such as a reservoir system) of the target material supply system 1300 that aren’t shown in Fig. 13.

[0119] The nozzle apparatus 1307 delivers the target material 1303 in the form of the stream 1362 of particles 1303p to the target space 1324 within a chamber 1322 of the EUV light source 1360. The interaction of a particle 1303p of the target material 1303 with radiation pulses of a light beam 1364 at the target space 1324 creates a plasma 1365 that produces EUV light 1366. The light beam 1364 can be generated by an optical source 1367. The EUV light 1366 that is generated by the interaction between the radiation pulses of the light beam 1364 and the particles 1303p is collected by a collector 1368, which supplies the EUV light 1366 to a lithography exposure apparatus 1369. The collector 1368 can be, for example, in the shape of a ellipsoid that has a first focus within the target space 1324 and a second focus at an intermediate point 1370 (also called the intermediate focus) at which the EUV light 1366 is output from the EUV light source 1360 and input to the lithography exposure apparatus 1369. The lithography exposure apparatus 1369 can be an integrated circuit lithography tool that uses the EUV light 1366, for example, to process a silicon wafer work piece 1371 in a known manner. The silicon wafer work piece 1371 is then additionally processed in a known manner to obtain an integrated circuit device.

[0120] Other implementations are within the scope of the following clauses.

1. A pressure relief apparatus for a target material supply system configured to deliver target material, the pressure relief apparatus comprising: a pressure relief component formed of a compressible material and disposed at an interior surface of a structure, the interior surface defining a cavity within the target material supply system, the structure formed of a rigid material and configured to contain the target material within the cavity, wherein the pressure relief component is configured to passively prevent a pressure in the cavity from exceeding a maximum allowed value.

2. The pressure relief apparatus of clause 1, wherein the pressure relief component is a liner that covers at least a portion of the interior surface of the structure.

3. The pressure relief apparatus of clause 2, wherein the structure is a hollow cylindrical tube, the cavity is cylindrical, and the liner covers at least a portion of the interior surface of the hollow cylindrical tube.

4. The pressure relief apparatus of clause 3, wherein the pressure relief component has a cylindrical shape with one or more grooves at a side of the cylindrical shape, the grooves extending axially along the cylindrical shape, and the pressure relief component is fitted into the cylindrical cavity of the hollow cylindrical tube.

5. The pressure relief apparatus of clause 2, wherein the pressure relief component has a rectangular bar shape, a hexagonal bar shape, or a polygonal bar shape, and the pressure relief component fills at least a portion of the structure.

6. The pressure relief apparatus of clause 1, wherein the structure is a demountable connection that connects two separate and distinct fluid devices and the pressure relief apparatus is a liner or a sleeve that at least partially extends over the demountable connection.

7. The pressure relief apparatus of clause 1, wherein the compressible material remains in an elastic regime at temperatures greater than the melting range of the target material such that the compressible material is compatible with the target material above the melting range of the target material and at pressures greater than 20 Megapascals (MPa), up to a maximum allowed pressure.

8. The pressure relief apparatus of clause 1, wherein the compressible material has an elastic modulus that remains below 6 GPa at operating temperature.

9. The pressure relief apparatus of clause 1, wherein a ratio of a volume of the compressible material to a volume of the target material contained within the cavity of the structure is related to an elastic modulus of the compressible material.

10. The pressure relief apparatus of clause 1, wherein the elastic modulus of the compressible material is less than an elastic modulus of the structure. 11. The pressure relief apparatus of clause 1, wherein the compressible material remains in a linear elastic regime after being repeatedly compressed and decompressed.

12. The pressure relief apparatus of clause 1, wherein the compressible material is configured to deform when the compressible material is compressed and decompressed and the deformation of the compressible material is nonpermanent.

13. The pressure relief apparatus of clause 1, wherein the compressible material is a polymer material.

14. The pressure relief apparatus of clause 13, wherein the polymer material is polyimide, polytetrafluoroethylene, polybenzimidazole, or polyether ether ketone.

15. The pressure relief apparatus of clause 1, wherein the pressure relief component is a liner that covers at least a portion of the interior surface of the structure, and a ratio of a volume of the liner that covers the interior surface of the structure to a volume of the target material contained within the cavity of the structure is at least 1.

16. The pressure relief apparatus of clause 15, wherein the compressible material is polyimide such that the liner is formed of polyimide, the structure is formed of molybdenum, and the volume of the liner occupies at least 80% of the cavity of the structure and the volume of the target material occupies the rest of the cavity of the structure, and wherein the polyimide liner experiences elastic deformation and does not experience permanent or plastic deformation.

17. The pressure relief apparatus of clause 1, wherein the compressible material is a rigid foam material with closed cells.

18. The pressure relief apparatus of clause 1, wherein the compressible material is formed of polyimide.

19. A target material supply system configured to deliver particles of a target material to a target space inside a chamber, the target material supply system comprising: one or more structures, each structure configured to retain the target material within a cavity defined by an interior surface of the structure; and a pressure relief apparatus associated with at least one of the structures, the pressure relief apparatus comprising a passive pressure relief device comprising a compressible mechanism in fluid communication with the cavity and configured to passively change the pressure in the cavity; wherein the compressible mechanism expands an effective volume of the cavity to compensate for an increase in volume of target material in the cavity.

20. The target material supply system of clause 19, wherein the increase in the volume of the target material in the cavity is caused by a change in temperature of the target material.

21. The target material supply system of clause 20, wherein the target material is configured to radiate extreme ultraviolet light when in a plasma state. 22. The target material supply system of clause 19, wherein the compressible mechanism is a liner that covers at least a portion of the interior surface of the structure with which the pressure relief apparatus is associated.

23. The target material supply system of clause 22, wherein the structure with which the pressure relief apparatus is associated is a hollow cylindrical tube having a cylindrical cavity, and the liner covers at least a portion of the interior surface of the hollow cylindrical tube.

24. The target material supply system of clause 22, wherein the liner occupies about 90% of the cavity of the structure with which the pressure relief apparatus is associated.

25. The target material supply system of clause 19, wherein the compressible mechanism is a polymer material.

26. The target material supply system of clause 19, wherein the compressible mechanism is an inert gas that does not react with the target material and is formed to be in physical contact with the target material.

27. The target material supply system of clause 26, wherein the inert gas is argon (Ar), xenon (Xe), helium (He), nitrogen (Nj), hydrogen (Hz), or carbon monoxide (CO).

28. The target material supply system of clause 26, wherein the inert gas occupies about 2% to about 10% of the cavity of the structure with which the pressure relief apparatus is associated.

29. The target material supply system of clause 19, wherein the passive pressure relief device is a pressure relief valve and the compressible mechanism is a mechanical spring configured to passively change the effective volume in the cavity, the pressure relief valve remaining closed as the effective volume of the cavity changes.

30. The target material supply system of clause 29, wherein the pressure relief valve and the mechanical spring are each made of a material that is compatible with the target material at associated temperatures and pressures above the melting range of the target material.

31. The target material supply system of clause 30, wherein the material is a refractory metal or a ceramic material.

32. The target material supply system of clause 19, wherein the target material is tin, lithium, xenon, or a tin alloy.

33. The target material supply system of clause 19, wherein a pressure relief apparatus is associated with a plurality of cylindrical structures, each cylindrical structure being a hollow cylindrical tube having a cylindrical cavity that transfers the target material in the form of a fluid.

34. The target material supply system of clause 33, wherein each of the cylindrical structures is connected to another one or more of the structures by a demountable connection.

35. The target material supply system of clause 34, wherein the demountable connection is associated with another pressure relief apparatus that comprises another passive pressure relief device comprising another compressible mechanism. 36. The target material supply system of clause 19, further comprising a target material source configured to create the target material from a solid target material, and a nozzle apparatus configured to direct the particles of the target material to interact with a light beam, the interaction of the particles with the light beam creating a plasma of the target material and producing extreme ultraviolet light.

37. An apparatus for a target material supply system configured to deliver particles of a target material, the apparatus comprising: a pressure relief device comprising a compressible mechanism in fluid communication with an interior of a cavity within a structure of the target material supply system, the cavity configured to contain the target material within the interior of the cavity; wherein the compressible mechanism of the pressure relief device is configured to passively change an effective volume in the cavity by absorbing or releasing energy associated with the pressure in the cavity.

38. A method for regulating a pressure of a target material in a target material supply system that comprises one or more unconfined zones, each unconfined zone defined by an open cavity that is not fluidically sealed, and one or more confined zones, each confined zone defined by a closed cavity, the method comprising: identifying one or more of the unconfined zones; melting the target material in at least one of the identified unconfined zones such that the at least one unconfined zone has a temperature greater than the melting range of the target material; and melting the target material in each confined zone that has a temperature less than the melting range of the target material only if the confined zone is adjacent to at least one of the unconfined zones that has a temperature greater than the melting range of the target material to thereby regulate the pressure of the target material in the confined zone.

39. The method of clause 38, wherein melting the target material in the unconfined zone comprises heating the target material such that the target material expands into the open cavity of the unconfined zone.

40. The method of clause 38, wherein melting the target material in the confined zone comprises heating the target material such that the target material expands into the at least one adjacent unconfined zone to thereby regulate the pressure of the target material.

41. The method of clause 38, wherein each of the one or more confined zones and the one or more unconfined zones are defined as a separate and distinct structure.

42. The method of clause 41, wherein each structure that is a confined zone is at least one of: a pipe configured to transfer the target material between other structures; a freeze valve configured to separate two or more of the other structures; a droplet generator assembly configured to create particles in the form of droplets of the target material; and a nozzle configured to direct the particles of the target material to interact with a light beam that irradiates the particles into a plasma state, thereby producing ultraviolet light.

43. The method of clause 41, wherein at least one of the structures that is an unconfined zone is a target material reservoir configured to hold the target material. 44. The method of clause 38, further comprising melting the target material in one or more other confined zones that have a temperature less than the melting range of the target material only if the other confined zone is adjacent to at least one of the confined zones that has a temperature greater than the melting range of the target material.

45. The method of clause 44, wherein melting target material in the confined zones comprises heating the target material in each of the one or more confined zones that have a temperature less than the melting range of the target material in a sequence such that each confined zone is adjacent to at least one of the unconfined zones and/or confined zones that has a temperature greater than the melting range of the target material at each step of the sequence.

Claims

CLAIMS:

2. The pressure relief apparatus of claim 1, wherein the pressure relief component is a liner that covers at least a portion of the interior surface of the structure.

3. The pressure relief apparatus of claim 2, wherein the structure is a hollow cylindrical tube, the cavity is cylindrical, and the liner covers at least a portion of the interior surface of the hollow cylindrical tube.

4. The pressure relief apparatus of claim 3, wherein the pressure relief component has a cylindrical shape with one or more grooves at a side of the cylindrical shape, the grooves extending axially along the cylindrical shape, and the pressure relief component is fitted into the cylindrical cavity of the hollow cylindrical tube.

5. The pressure relief apparatus of claim 2, wherein the pressure relief component has a rectangular bar shape, a hexagonal bar shape, or a polygonal bar shape, and the pressure relief component fills at least a portion of the structure.

6. The pressure relief apparatus of claim 1, wherein the structure is a demountable connection that connects two separate and distinct fluid devices and the pressure relief apparatus is a liner or a sleeve that at least partially extends over the demountable connection.

7. The pressure relief apparatus of claim 1, wherein the compressible material remains in an elastic regime at temperatures greater than the melting range of the target material such that the compressible material is compatible with the target material above the melting range of the target material and at pressures greater than 20 Megapascals (MPa), up to a maximum allowed pressure.

8. The pressure relief apparatus of claim 1, wherein the compressible material has an elastic modulus that remains below 6 GPa at operating temperature.

9. The pressure relief apparatus of claim 1, wherein a ratio of a volume of the compressible material to a volume of the target material contained within the cavity of the structure is related to an elastic modulus of the compressible material.

10. The pressure relief apparatus of claim 1, wherein the elastic modulus of the compressible material is less than an elastic modulus of the structure.

11. The pressure relief apparatus of claim 1, wherein the compressible material remains in a linear elastic regime after being repeatedly compressed and decompressed.

12. The pressure relief apparatus of claim 1, wherein the compressible material is configured to deform when the compressible material is compressed and decompressed and the deformation of the compressible material is nonpermanent.

13. The pressure relief apparatus of claim 1, wherein the compressible material is a polymer material.

14. The pressure relief apparatus of claim 13, wherein the polymer material is polyimide, polytetrafluoroethylene, polybenzimidazole, or polyether ether ketone.

15. The pressure relief apparatus of claim 1, wherein the pressure relief component is a liner that covers at least a portion of the interior surface of the structure, and a ratio of a volume of the liner that covers the interior surface of the structure to a volume of the target material contained within the cavity of the structure is at least 1.

16. The pressure relief apparatus of claim 15, wherein the compressible material is polyimide such that the liner is formed of polyimide, the structure is formed of molybdenum, and the volume of the liner occupies at least 80% of the cavity of the structure and the volume of the target material occupies the rest of the cavity of the structure, and wherein the polyimide liner experiences elastic deformation and does not experience permanent or plastic deformation.

17. The pressure relief apparatus of claim 1, wherein the compressible material is a rigid foam material with closed cells.

18. The pressure relief apparatus of claim 1, wherein the compressible material is formed of polyimide.

20. The target material supply system of claim 19, wherein the increase in the volume of the target material in the cavity is caused by a change in temperature of the target material.

21. The target material supply system of claim 20, wherein the target material is configured to radiate extreme ultraviolet light when in a plasma state.

22. The target material supply system of claim 19, wherein the compressible mechanism is a liner that covers at least a portion of the interior surface of the structure with which the pressure relief apparatus is associated.

23. The target material supply system of claim 22, wherein the structure with which the pressure relief apparatus is associated is a hollow cylindrical tube having a cylindrical cavity, and the liner covers at least a portion of the interior surface of the hollow cylindrical tube.

24. The target material supply system of claim 22, wherein the liner occupies about 90% of the cavity of the structure with which the pressure relief apparatus is associated.

25. The target material supply system of claim 19, wherein the compressible mechanism is a polymer material.

26. The target material supply system of claim 19, wherein the compressible mechanism is an inert gas that does not react with the target material and is formed to be in physical contact with the target material.

27. The target material supply system of claim 26, wherein the inert gas is argon (Ar), xenon (Xe), helium (He), nitrogen (Nj), hydrogen (Hz), or carbon monoxide (CO).

28. The target material supply system of claim 26, wherein the inert gas occupies about 2% to about 10% of the cavity of the structure with which the pressure relief apparatus is associated.

29. The target material supply system of claim 19, wherein the passive pressure relief device is a pressure relief valve and the compressible mechanism is a mechanical spring configured to passively change the effective volume in the cavity, the pressure relief valve remaining closed as the effective volume of the cavity changes.

30. The target material supply system of claim 29, wherein the pressure relief valve and the mechanical spring are each made of a material that is compatible with the target material at associated temperatures and pressures above the melting range of the target material.

31. The target material supply system of claim 30, wherein the material is a refractory metal or a ceramic material.

32. The target material supply system of claim 19, wherein the target material is tin, lithium, xenon, or a tin alloy.

33. The target material supply system of claim 19, wherein a pressure relief apparatus is associated with a plurality of cylindrical structures, each cylindrical structure being a hollow cylindrical tube having a cylindrical cavity that transfers the target material in the form of a fluid.

34. The target material supply system of claim 33, wherein each of the cylindrical structures is connected to another one or more of the structures by a demountable connection.

35. The target material supply system of claim 34, wherein the demountable connection is associated with another pressure relief apparatus that comprises another passive pressure relief device comprising another compressible mechanism.

36. The target material supply system of claim 19, further comprising a target material source configured to create the target material from a solid target material, and a nozzle apparatus configured to direct the particles of the target material to interact with a light beam, the interaction of the particles with the light beam creating a plasma of the target material and producing extreme ultraviolet light.

39. The method of claim 38, wherein melting the target material in the unconfined zone comprises heating the target material such that the target material expands into the open cavity of the unconfined zone.

40. The method of claim 38, wherein melting the target material in the confined zone comprises heating the target material such that the target material expands into the at least one adjacent unconfined zone to thereby regulate the pressure of the target material.

41. The method of claim 38, wherein each of the one or more confined zones and the one or more unconfined zones are defined as a separate and distinct structure.

42. The method of claim 41, wherein each structure that is a confined zone is at least one of: a pipe configured to transfer the target material between other structures; a freeze valve configured to separate two or more of the other structures; a droplet generator assembly configured to create particles in the form of droplets of the target material; and a nozzle configured to direct the particles of the target material to interact with a light beam that irradiates the particles into a plasma state, thereby producing ultraviolet light.

43. The method of claim 41, wherein at least one of the structures that is an unconfined zone is a target material reservoir configured to hold the target material.

44. The method of claim 38, further comprising melting the target material in one or more other confined zones that have a temperature less than the melting range of the target material only if the other confined zone is adjacent to at least one of the confined zones that has a temperature greater than the melting range of the target material.

45. The method of claim 44, wherein melting target material in the confined zones comprises heating the target material in each of the one or more confined zones that have a temperature less than the melting range of the target material in a sequence such that each confined zone is adjacent to at least one of the unconfined zones and/or confined zones that has a temperature greater than the melting range of the target material at each step of the sequence.