Circulation mechanism and light source device

Abstract

To provide a circulation mechanism and an operation device which are capable of preventing erosion by liquid metal.SOLUTION: A circulation mechanism comprises a housing part, a supply pipe, a recovery pipe, a circulation drive part, and a protective member. The housing part houses liquid metal. The supply pipe supplies the liquid metal housed in the housing part to a subject mechanism. The recovery pipe communicates with the housing part, and recovers the liquid metal flown out from the subject mechanism to the housing part. The circulation drive part, by moving the liquid metal housed in the housing part to the supply pipe, circulates the liquid metal between the subject mechanism and itself. The protective member is arranged so as to cover an area corresponding to a position of an inner wall of the recovery pipe at which the liquid metal flowing through the recovery pipe and the liquid metal housed in the housing part collide.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a circulation mechanism for circulating liquid metal, and an operating device that operates by utilizing liquid metal. [Background technology]

[0002] In recent years, as semiconductor integrated circuits become finer and more highly integrated, the wavelength of light for exposure is becoming shorter. As a next-generation semiconductor exposure light source, the development of an extreme ultraviolet light source device (hereinafter also referred to as an "EUV light source device") that emits extreme ultraviolet light (hereinafter also referred to as "EUV light") with a wavelength of 13.5 nm is being promoted.

[0003] There are several known methods for generating EUV light (EUV radiation) in EUV light source devices. One of these methods involves heating and exciting extreme ultraviolet emitting species (hereinafter also referred to as EUV emitting species) to generate high-temperature plasma, and extracting the EUV light from the high-temperature plasma. EUV light source devices that employ this method are divided into an LPP (Laser Produced Plasma) type and a DPP (Discharge Produced Plasma) type depending on the method of generating high temperature plasma.

[0004] DPP type EUV light source devices apply a high voltage between electrodes to which a discharge gas containing EUV radiating species (gaseous plasma raw material) is supplied, generating high-density, high-temperature plasma through discharge, and utilize the extreme ultraviolet light emitted from it. As an example of the DPP method, as described in Patent Document 1, a method has been proposed in which liquid high-temperature plasma raw material (e.g., Sn (tin) or Li (lithium)) containing EUV radiating species is supplied to the surface of an electrode (discharge electrode) that generates a discharge, the raw material is irradiated with an energy beam such as a laser beam to vaporize the raw material, and then high-temperature plasma is generated by discharge. This type of method is sometimes called an LDP (Laser Assisted Discharge Produced Plasma) method.

[0005] On the other hand, an LPP type EUV light source device irradiates a target material with laser light, and excites the target material to generate plasma.

[0006] EUV light source devices are used as light source devices for semiconductor exposure equipment (lithography equipment) in semiconductor device manufacturing. Alternatively, EUV light source devices are used as light source devices for inspection equipment for masks used in lithography. In other words, EUV light source devices are used as light source devices for other optical systems (utilization equipment) that use EUV light.

[0007] As described above, in the LDP method, high-temperature plasma raw material is supplied to the surface of a discharge electrode. Specifically, as described in Patent Document 1, liquid-phase plasma raw material (e.g., liquid-phase tin) is stored in a container, and a part of a disk-shaped discharge electrode (anode, cathode) is immersed in the liquid-phase plasma raw material. The discharge electrode is configured to be rotatable. As the discharge electrode rotates, the portion of the discharge electrode that is immersed in the liquid-phase plasma raw material is transported to the discharge region. In other words, the liquid-phase plasma raw material is transported to the discharge region. Here, the discharge region is a region where a discharge occurs after the above-mentioned energy beam is irradiated. A container in which the plasma raw material is stored and discharge electrodes (anode, cathode) function as the plasma source, and high-temperature plasma is generated in the discharge region.

[0008] Here, the liquid phase plasma raw material stored in the container is consumed and reduced by generating plasma. Therefore, in order to replenish this, the container that stores the liquid phase plasma raw material is connected to a plasma raw material supply mechanism that includes a reservoir that holds the liquid phase plasma raw material. Patent Document 2 discloses this plasma raw material supply mechanism.

[0009] The discharge electrode is heated as a discharge occurs. As described above, a portion of the discharge electrode is immersed in the liquid-phase plasma raw material stored in the container. Therefore, by rotating the discharge electrode, at least the portion of the discharge electrode heated by the discharge passes through the liquid-phase plasma raw material, and heat exchange occurs between the heated portion and the liquid-phase plasma raw material, and the portion heated by the discharge is cooled. Meanwhile, the temperature of the liquid-phase plasma raw material stored in the container rises. Therefore, by circulating liquid phase plasma raw material between the container and the plasma raw material supply mechanism including the above-mentioned reservoir and cooling at least a portion of the circulation path, it is possible to supply liquid phase plasma raw material to the container and also to maintain the temperature of the liquid phase plasma raw material stored in the container at a predetermined temperature.

[0010] From the viewpoints of ease of processing and material cost, stainless steel is usually used as a constituent material of the plasma raw material supply mechanism, but stainless steel does not have sufficient resistance to electrochemical corrosion by molten metal (e.g., lithium, tin, etc.) that is the liquid phase plasma raw material, and mechanical erosion by heated metal. In order to impart resistance to molten metal (liquid metal) to stainless steel, Patent Document 3 proposes coating the surface of a plasma raw material supply mechanism made of stainless steel that comes into contact with liquid metal with a covalent inorganic solid material. For example, TiN is used as the covalent inorganic solid material. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2017-219698 A [Patent Document 2] JP 2014-225437 A [Patent Document 3] JP 2011-527503 A Summary of the Invention [Problem to be solved by the invention]

[0012] In a mechanism for supplying liquid metal, such as the plasma raw material supply mechanism described above, it is important to prevent piping and the like from being eroded by the liquid metal.

[0013] In view of the above circumstances, an object of the present invention is to provide a circulation mechanism and an operating device capable of preventing erosion by liquid metal. [Means for solving the problem]

[0014] In order to achieve the above object, a circulation mechanism according to one aspect of the present invention includes a container, a supply pipe, a recovery pipe, a circulation drive unit, and a protective member. The container contains a liquid metal. The supply pipe supplies the liquid metal contained in the container to a target mechanism. The recovery pipe is in communication with the container, and recovers the liquid metal flowing out of the target mechanism into the container. The circulation drive unit moves the liquid metal accommodated in the accommodation unit to the supply pipe, thereby circulating the liquid metal between the target mechanism and the liquid metal. The protective member is disposed so as to cover a portion of an inner wall of the recovery pipe corresponding to a position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container section collide with each other.

[0015] In this circulation mechanism, a protective member is disposed on the inner wall of the recovery pipe so as to cover the portion corresponding to the position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container collide with each other, thereby making it possible to prevent the recovery pipe from being corroded by the liquid metal.

[0016] The recovery pipe may be in communication with the container at a position where the liquid metal contained in the container enters the inside of the recovery pipe, and in this case, the protective member may be disposed so as to cover a portion of an inner wall of the recovery pipe that contacts a liquid surface of the liquid metal entering the recovery pipe.

[0017] The recovery pipe may have a protective film formed on an inner wall of the recovery pipe. In this case, the protective member may be disposed on the protective film.

[0018] The protective member may have a hollow cylindrical shape and be inserted into the recovery pipe.

[0019] The protective member may be configured of a deformable sheet member, and may be inserted into the recovery pipe in a deformed state so as to fit along an inner wall of the recovery pipe.

[0020] The protective member may be configured as a hollow tubular member and may be inserted into the recovery pipe.

[0021] The liquid metal may be tin, lithium, gadolinium, terbium, gallium, or an alloy containing at least one of these materials.

[0022] The protective member may be comprised of molybdenum, titanium, vanadium, chromium, zirconium, niobium, hafnium, tantalum, tungsten, rhenium, ruthenium, osmium, and iridium, or an alloy containing at least one of these materials.

[0023] The protective film may be composed of titanium nitride, titanium, or an alloy containing at least one of these materials.

[0024] The container may have a connection hole to which the recovery pipe is connected. In this case, the recovery pipe may be connected to the connection hole so as to protrude from the connection hole toward the inside of the container.

[0025] The recovery pipe may have a pipe outlet through which the metal material flows out into the container. In this case, the protective member may have a protruding portion that protrudes from the pipe outlet toward the inside of the container. The protruding portion may have an outlet through which the liquid metal flowing out from the pipe outlet flows out toward the liquid metal contained in the container.

[0026] The protrusion may extend in a direction inclined with respect to the liquid level of the liquid metal contained in the container, and an end face forming the outlet may be configured to be parallel to the liquid level.

[0027] The recovery pipe may have a pipe inlet through which the liquid metal flowing out from the target mechanism flows in, and a pipe outlet located vertically below the inlet and through which the liquid metal flows out to the storage section, and may be arranged at an angle with respect to the storage section.

[0028] The circulation mechanism may further include a temperature adjustment mechanism that adjusts the temperature of at least one of the liquid metal flowing through the recovery pipe, the liquid metal contained in the container, or the liquid metal flowing through the supply pipe.

[0029] An operating device according to one aspect of the present invention includes an operating unit that operates by utilizing liquid metal, and the circulation mechanism.

[0030] The operating unit may have a container that holds the liquid metal as a plasma raw material, and a rotating electrode that is partially immersed in the plasma raw material, and may generate plasma that emits radiation by generating a discharge at the portion of the rotating electrode to which the plasma raw material adheres. In this case, the operating device may be configured as a device that emits the radiation. Effect of the Invention

[0031] As described above, according to the present invention, it is possible to prevent erosion by liquid metal. Note that the effects described here are not necessarily limited to those described, and may be any of the effects described in the present disclosure. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram showing an example of the basic configuration of a plasma raw material supply mechanism according to one embodiment of the present invention. [Diagram 2] 4 is an enlarged view of a portion of a recovery side connection hole of the reservoir. FIG. [Diagram 3] 4 is an enlarged view of a portion of a recovery side connection hole of the reservoir. FIG. [Figure 4] FIG. 1 is a schematic diagram showing the results of a simulation analysis of the distribution of the magnitude of pressure fluctuations (impacts) caused by collisions of plasma raw materials. [Diagram 5] FIG. 13 is a schematic diagram showing an example of a configuration using a protective member. [Figure 6] 13 is a schematic diagram showing another configuration example using a protective member. FIG. [Figure 7] 1 is a schematic diagram showing an example of a basic configuration of an extreme ultraviolet light source device (EUV light source device). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0034] [Plasma raw material supply mechanism] FIG. 1 is a schematic diagram showing an example of the basic configuration of a plasma raw material supply mechanism according to one embodiment of the present invention. Here, an example will be taken in which the plasma raw material supply mechanism 1 is configured within an EUV light source device 2 of the LDP type. The plasma raw material supply mechanism 1 corresponds to one embodiment of the circulation mechanism according to the present invention. The LDP type EUV light source device 2 including the plasma raw material supply mechanism 1 corresponds to one embodiment of the operating device according to the present invention.

[0035] First, the plasma source 3 of the EUV light source device 2 to which the plasma raw material supply mechanism 1 is connected will be briefly described. The plasma source 3 has a disk-shaped discharge electrode 4 (anode 4a, cathode 4b) and a container 6 that contains liquid-phase plasma raw material 5. A part of the disk-shaped discharge electrode 4 is immersed in the liquid-phase plasma raw material 5 stored in the container 6. In this embodiment, liquid-phase tin is used as the plasma raw material 5. The plasma raw material 5 corresponds to one embodiment of the liquid metal according to the present invention. The plasma source 3 can also be called a source module (heat source) or a source head.

[0036] The discharge electrode 4 (anode 4a, cathode 4b) is configured to be rotatable. When the discharge electrode 4 rotates, the portion of the discharge electrode 4 that is immersed in the liquid-phase plasma raw material 5 is transported to the discharge region 7. In other words, the portion of the discharge electrode 4 on which the liquid-phase plasma raw material 5 is applied is transported to the discharge region 7. Here, the discharge region 7 is a region where a discharge occurs after being irradiated with an energy beam E such as a laser beam. In this way, fresh plasma raw material 5 is constantly supplied to the discharge region 7. The liquid phase plasma raw material 5 also functions as a coolant for the discharge electrode 4.

[0037] A pulsed power supply unit 8 for generating a discharge between the anode 4a and the cathode 4b is connected to a metallic container 6. The pulsed power supply unit 8 supplies power to each discharge electrode 4 via the container 6 which is electrically connected to each discharge electrode 4 and the conductive liquid-phase plasma raw material 5. When the energy beam E is irradiated onto the cathode 4b, a discharge occurs between the two electrodes to which the plasma raw material 5 is applied, generating a high-temperature plasma P, from which EUV light L is emitted.

[0038] 1, the plasma raw material supply mechanism 1 is configured to be able to supply and recover liquid phase plasma raw material 5 to a container 6 on the cathode 4b side of the plasma source 3. A similar plasma raw material supply mechanism 1 is also connected to the anode 4a side of the plasma source 3. Of the two plasma raw material supply mechanisms 1, the plasma raw material supply mechanism 1 that supplies raw material to the cathode 4b side will be explained below as a representative example.

[0039] The plasma raw material supply mechanism 1 has a reservoir (container) 10, a supply pipe 11, a recovery pipe 12, a pump 13, and a cooling mechanism . The reservoir 10 has a hollow cylindrical shape as an approximate outer shape. The size of the cylindrical shape in the height direction is relatively small. The reservoir 10 is disposed so that the axial direction of the central axis of the cylinder is approximately parallel to the horizontal direction. That is, the reservoir 10 is a hollow member having a low cylindrical shape and is disposed horizontally. Fig. 1 shows a schematic cross-sectional view of the reservoir 10 cut in a direction perpendicular to the axial direction of the central axis. The configuration of the reservoir 10 is not limited, and other configurations may be adopted.

[0040] 1, the internal space of the reservoir 10 is roughly divided into two spaces. Specifically, when the reservoir 10 is viewed along the central axis of the cylindrical shape, the wall portion 15 is configured to extend obliquely downward from a certain position on the upper side. The lower space divided by wall 15 becomes raw material supply space S1 in which plasma raw material 5 is stored. The upper space divided by wall 15 becomes raw material passage space S2 which contains a path for allowing plasma raw material 5 to flow into container 6. The raw material supply space S1 and the raw material passing space S2 are sealed from each other by a wall portion 15 and spatially divided.

[0041] The raw material supply space S1 of the reservoir 10 is designed to have a larger capacity than the container 6 of the plasma source 3. This makes it possible to fill the container 6 with the plasma raw material 5 consumed in the discharge operation etc. for a relatively long period of time.

[0042] As shown in FIG. 1, the outer wall constituting the raw material supply space S1 of the reservoir 10 is formed with a recovery side connection hole 16 to which the recovery pipe 12 is connected and a supply side connection hole 17 to which the supply pipe 11 is connected. The recovery side connection hole 16 is configured to communicate with the raw material supply space S1, near the position of a liquid surface 18 of the plasma raw material 5 contained in the raw material supply space S1. Supply side connection hole 17 is configured to communicate with raw material supply space S1 near the lowest position of raw material supply space S1. Therefore, supply side connection hole 17 is configured at a deep position of the plasma raw material 5 contained in raw material supply space S1.

[0043] The supply pipe 11 is a pipe for supplying the plasma raw material 5 contained in the raw material supply space S1 to the container 6. One end of the supply pipe 11 is connected to a supply side connecting hole 17 that communicates with the raw material supply space S1. Therefore, this end serves as a pipe inlet 19 through which the plasma raw material 5 flows in (in FIG. 1, the same part as the supply side connecting hole 17 is denoted by the reference symbol 19). The other end of the supply pipe 11 is connected to a raw material return port 20 formed in the container 6. The raw material return port 20 is a hole for supplying the plasma raw material 5 into the container 6. Therefore, this end serves as a pipe outlet 21 from which the plasma raw material 5 flows out (in FIG. 1, the same part as the raw material return port 20 is denoted by the reference symbol 21). In this manner, the supply pipe 11 communicates with both the raw material supply space S 1 of the reservoir 10 and the container 6 , and supplies the plasma raw material 5 contained in the raw material supply space S to the container 6 .

[0044] The recovery pipe 12 is a pipe for recovering the plasma raw material 5 from the container 6 . One end of the recovery pipe is connected to a raw material discharge port 22 formed in the container 6. The raw material discharge port 22 is a hole for discharging the plasma raw material 5 from inside the container 6. This end therefore becomes the pipe inlet 23 through which the plasma raw material 5 flows in (in FIG. 1, the same part as the raw material discharge port 22 is given the reference symbol 23). The other end of the recovery pipe 12 is connected to a recovery side connecting hole 16 that communicates with the raw material supply space S1. In this embodiment, as shown in FIG. 1, the recovery pipe 12 is connected to the recovery side connecting hole 16 so as to protrude from the recovery side connecting hole 16 toward the inside of the reservoir 10. The plasma raw material 5 flows out into the reservoir 10 from a piping outlet 24 arranged inside the reservoir 10 . In this way, the recovery pipe 12 communicates with both the container 6 and the raw material supply space S1 of the reservoir 10, and recovers the plasma raw material 5 that flows out of the container 6 into the raw material supply space S1.

[0045] The reservoir 10, the supply pipe 11, and the recovery pipe 12 are made of stainless steel. Furthermore, on the areas that come into contact with the plasma raw material 5, such as the inner wall of the reservoir 10, the inner wall of the supply pipe 11, and the inner wall of the recovery pipe 12, a liquid metal resistant coating is formed as a protective film (not shown). The protective film is, for example, a covalent inorganic solid material. In this embodiment, a TiN film made of titanium nitride (TiN) is formed, but a protective film made of another material may be formed. For example, the protective film may be formed of titanium nitride (TiN), titanium (Ti), or an alloy containing at least one of these materials.

[0046] The pump 13 is provided in the supply pipe 11 . When the pump 13 is driven, the plasma raw material 5 contained in the raw material supply space S1 of the reservoir 10 flows out into the supply pipe 11, making it possible to circulate the plasma raw material 5 through a circulation system including the reservoir 10, the supply pipe 11, the container 6, and the recovery pipe 12. That is, by driving the pump 13, the plasma raw material 5 in the reservoir 10 can be supplied to the container 6 and also recovered to the reservoir 10. For example, an electromagnetic pump is used as pump 13. The electromagnetic pump applies a magnetic field from outside supply piping 11, and utilizes the Lorentz force that is generated in the plasma raw material 5 inside supply piping 11 when a current is passed through it, to generate a flow of plasma raw material 5 inside supply piping 11. As a result, a pumping force is generated that is capable of moving the plasma raw material 5 contained in raw material supply space S1 into supply piping 11.

[0047] There are no limitations on the position at which pump 13 is provided. Pump 13 can be provided at any position in the circulation path formed by reservoir 10, supply pipe 11, and recovery pipe 12, so long as it can generate a pumping force capable of moving plasma raw material 5 contained in raw material supply space S1 to supply pipe 11. The plasma raw material 5 supplied to the container 6 is caused to flow out from the raw material outlet 22 into the recovery pipe 12 by the rotation of the discharge electrode 4 .

[0048] The raw material reflux port 20 is formed near the region in the container 6 through which the discharge electrode 4 passes just before reaching the discharge region 7. The raw material discharge port 22 is formed near the region where the portion of the container 6 irradiated with the energy beam E of the discharge electrode 4 is immersed again in the plasma raw material 5 inside the container 6. With this configuration, it becomes possible to transport the plasma raw material 5 at a predetermined set temperature to the discharge region 7 at the discharge electrode 4 before the energy beam E is irradiated and before a discharge occurs. Furthermore, the discharge electrode 4, heated by the generation of the discharge, comes into contact with the plasma raw material 5 in the container 6, and the plasma raw material 5 is heated to a desired temperature or higher, but it is possible to quickly discharge this heated plasma raw material 5 from the container 6. This makes it possible to prevent the effects of the heating of the plasma raw material 5 from acting on the plasma raw material 5 that is transported to the discharge region 7 at the time of the next discharge.

[0049] The high-temperature plasma raw material 5 recovered from the recovery pipe 12 is discharged from the pipe outlet 24 of the recovery pipe 12 into the raw material supply space S1 of the reservoir 10, where it is mixed with the plasma raw material 5 in the reservoir 10 and cooled to a certain extent.

[0050] Here, the plasma raw material 5 discharged from the container 6 contains slag 25 such as impurities and metal oxide (tin oxide). The slag 25 contained in the plasma raw material 5 discharged from the pipe outlet 24 of the recovery pipe 12 to the reservoir 10 condenses on the liquid surface 18 of the liquid-phase plasma raw material 5 in the reservoir 10.

[0051] As shown in FIG. 1, in this embodiment, a plate-shaped slag separator 27 having holes 26 formed therein is provided in the raw material supply space S1. The slag separator 27 is provided so as to extend obliquely from a position above the supply side connection hole 17 provided on the lower side of the reservoir 10 to the vicinity of the recovery side connection hole 16 through which the plasma raw material 5 is discharged. The slag separator 27 is configured as a barrier between the liquid level 18 at which the slag 25 aggregates and the supply side connection hole 17 provided on the lower side of the reservoir 10 . This makes it possible to separate the liquid-phase plasma raw material 5 discharged from the recovery piping 12 connected to the recovery side connecting hole 16 from the slag 25 that has aggregated on the liquid surface 18 of the liquid-phase plasma raw material 5. As a result, it is possible to prevent the plasma raw material 5 mixed with the slag 25 from flowing out into the supply piping 11 connected to the supply side connecting hole 17.

[0052] The plasma raw material 5 recovered from the container 6 via the recovery pipe 12 to the reservoir 10 is mixed with the plasma raw material 5 in the reservoir 10 and cooled to a certain extent. Furthermore, before the plasma raw material 5 is returned to the container 6, the temperature of the plasma raw material 5 is adjusted to a temperature level that is appropriately (1 to 50 K) higher than the melting temperature of the plasma raw material 5.

[0053] The cooling mechanism 14 is capable of cooling (adjusting the temperature) of the plasma raw material 5. As shown in FIG. 1, the cooling mechanism 14 is provided in the raw material passing space S2. A through channel 28 that crosses the raw material passing space S2 is formed in the raw material passing space S2. The supply pipe 11 is provided in the through channel 28. Alternatively, the through channel 28 itself may be configured as a part of the supply pipe 11.

[0054] The cooling mechanism 14 is provided for the through channel 28, and cools the through channel 28, thereby cooling (adjusting the temperature) the plasma raw material 5. The cooling mechanism 14 may be, for example, a spray cooling mechanism, a heat pipe, a radiator, or the like, as disclosed in Patent Document 2. (In FIG. 1, the cooling mechanism is diagrammatically shown by a dot pattern in the raw material passing space S2.)

[0055] In the plasma source 3, the plasma raw material 5 in the container 6 is consumed by the discharge operation (high temperature plasma generation). The plasma raw material 5 stored in the raw material supply space S1 of the reservoir 10 is replenished into the container 6 to compensate for the consumed amount. As a result, the plasma raw material 5 stored in the reservoir 10 gradually decreases. In this embodiment, the raw material supply space S1 is provided with a sensor (not shown) that senses the amount of plasma raw material 5 stored in that space. As the sensor, for example, a level sensor that detects the liquid level of the plasma raw material 5, as disclosed in Patent Document 2, is used. When it is detected that the contact between the level sensor and the plasma raw material 5 has been released, the raw material supply space S1 of the reservoir 10 is refilled with the plasma raw material 5. The plasma raw material 5 is charged through a plasma raw material replenishment port (not shown) which is provided in the raw material supply space S1 of the reservoir 10 in which the plasma raw material 5 is stored.

[0056] For cooling the discharge electrode 4 of the plasma source 3 and for generating EUV radiation from the high pressure plasma P generated in the plasma source 3, it is possible to use lithium (Li), tin (Sb), gadolinium (Gd), terbium (Tb), gallium (Ga), or an alloy containing at least one of these materials. Without being limited to these materials, the present invention can be applied to any liquid metal.

[0057] The plasma source 3 and plasma raw material supply mechanism 1 are placed inside the EUV light source device 2. The plasma raw material 5 stored in the plasma raw material supply mechanism 1 and circulated between the plasma source 3 and a container 6 is a liquid metal maintained at a high temperature. Therefore, it is desirable to block undesired heat radiation from the plasma raw material 5 to other mechanisms arranged around the plasma raw material supply mechanism 1 within the EUV light source device 2 . For this reason, the reservoir 10 containing the plasma raw material 5 is placed in a negative pressure state in order to suppress heat radiation to other surrounding mechanisms.

[0058] In this embodiment, the mechanism for generating the EUV light L from the plasma source 3 corresponds to one embodiment of the target mechanism. Also, the mechanism for generating the EUV light L corresponds to one embodiment of an operating part that operates by using liquid metal. The reservoir 10 (the portion constituting the raw material supply space S1) corresponds to one embodiment of a container that contains a liquid metal. The supply pipe 11 corresponds to one embodiment of the supply pipe according to the present invention. The recovery pipe 12 corresponds to one embodiment of the recovery pipe according to the present invention. The pump 13 corresponds to one embodiment of a circulation drive unit that circulates the liquid metal between the target mechanism by moving the liquid metal contained in the container to the supply pipe. The recovery side connecting hole 16 of the reservoir 10 corresponds to one embodiment of a connecting hole to which a recovery pipe is connected. The pipe outlet 24 of the recovery pipe 12 corresponds to one embodiment of a pipe outlet through which the metal material flows out into the storage section. The cooling mechanism 14 corresponds to one embodiment of a temperature adjustment mechanism that adjusts the temperature of at least one of the liquid metal flowing through the recovery pipe, the liquid metal contained in the container, and the liquid metal flowing through the supply pipe.

[0059] [Corrosion of pipes, etc.] As disclosed in Patent Document 2, even if a protective film (TiN film) is formed in areas where the plasma raw material 5 (liquid metal: liquid phase tin) heated to a high temperature comes into contact, such as the inner wall of the recovery pipe 12, the inner wall of the supply pipe 11, and the inner wall of the reservoir 10, erosion by the plasma raw material 5 may occur. Patent Document 2 states that such erosion occurs because large stress is applied by the heat or flow of the plasma raw material 5 in areas such as areas where the piping that forms the circulation path of the plasma raw material 5 is distorted in the direction of the flow of the liquid metal, or in areas where the plasma raw material 5 from the reservoir 10 mechanically collides.

[0060] The present inventors have conducted extensive research into the erosion of pipes and the like by the plasma raw material 5. When the inventors investigated the parts of the pipes and the like that had been eroded by the plasma raw material 5 (parts where the TiN film had been destroyed and the pipes and the like had been damaged), they found that erosion was occurring only in specified locations. If the stress is due to the force of the flow of plasma raw material 5, then erosion should occur randomly in all areas where the stress is applied. However, both the actual results and experiments using the actual equipment showed that erosion occurs only in certain specific locations. In other words, it is suggested that the occurrence of erosion in the TiN film or piping is not necessarily caused by the stress (shear stress) accompanying the flow of plasma raw material 5. Furthermore, the inventors conducted experiments using test pieces in which a TiN film was formed on the same material as the piping, and found that neither damage to the TiN film nor erosion of the base material was observed, even due to the stress caused by the heat of the plasma raw material 5.

[0061] 2 and 3 are enlarged views of the recovery side connection hole 16 of the reservoir 10. FIG. According to the inventor's investigation, it was found that erosion occurs at the connection between the recovery pipe 12 and the reservoir 10 . The present inventors conducted a detailed investigation into the locations at which erosion occurs in the connection portion between the recovery pipe 12 and the reservoir 10 for a number of configurations exemplified in FIG. 2 and FIG.

[0062] 1, in this embodiment, the pipe outlet 24 of the recovery pipe 12 is installed vertically below the pipe inlet 23 into which the plasma raw material 5 flows out of the container 6. In addition, the recovery pipe 12 is disposed at an angle with respect to the reservoir 10. The term "arranged at an angle" includes, for example, various configurations in which a line connecting the pipe inlet 23 and the pipe outlet 24 of the recovery pipe 12 is inclined with respect to the reservoir 10. For example, a configuration in which the recovery pipe 12 is configured straight without bending and is arranged at an angle with respect to the reservoir 10 is included in the configuration in which the recovery pipe 12 is arranged at an angle with respect to the reservoir 10. Not limited to this, even if the recovery pipe 12 having a bent portion in the middle is arranged at an angle to the reservoir 10, if the line connecting the pipe inlet 23 and the pipe outlet 24 is inclined with respect to the reservoir 10, this is included in the configuration in which the recovery pipe 12 is arranged at an angle to the reservoir 10. All of the configurations illustrated in FIG. 2 and FIG. 3 are included in the configuration in which the recovery pipe 12 is disposed at an incline with respect to the reservoir 10.

[0063] 2A, recovery pipe 12 is bent near pipe outlet 24 of recovery pipe 12. Bent portion (hereinafter, bent portion) 29 is connected to recovery side connection hole 16 of reservoir 10. Furthermore, a portion of the lower side of pipe outlet 24 of recovery pipe 12 is submerged below liquid level 18 of the plasma raw material 5 contained in reservoir 10 (raw material supply space S1). Therefore, the plasma raw material 5 has entered from pipe outlet 24 of recovery pipe 12 to the inside of bent section 29. Thus, in the example shown in FIG. 2A, the recovery pipe 12 communicates with the reservoir 10 at a position where the plasma raw material 5 contained in the reservoir 10 enters the inside of the recovery pipe 12.

[0064] In the configuration shown in FIG. 2A, erosion occurred in region R of the inner wall of recovery pipe 12 near the position of liquid surface 30 of plasma raw material 5 entering recovery pipe 12. The plasma raw material 5 that has entered the recovery pipe 12 is included in the plasma raw material 5 stored in the reservoir 10. Typically, the position of the liquid level 30 of the plasma raw material 5 that has entered the recovery pipe 12 is equal to the liquid level 18 of the plasma raw material 5 that has not entered the recovery pipe 12. Depending on the configuration of the recovery pipe 12 and the connection between the recovery pipe 12 and the reservoir 10, it may be the case that the position of the liquid level 30 of the plasma raw material 5 that has entered the recovery pipe 12 differs from the liquid level 18 of the plasma raw material 5 that has not entered the recovery pipe 12. Even in this case, the present invention is applicable. From the investigation results shown in FIG. 2A, it is possible to consider that, as disclosed in Patent Document 2, stress caused by the heat and flow of plasma raw material 5 acted on bent portion 29.

[0065] 2B uses recovery pipe 12 that is bent near pipe outlet 24, similar to the configuration shown in Fig. 2A. Meanwhile, the position of liquid level 18 of plasma raw material 5 contained in reservoir 10 is set below pipe outlet 24 of recovery pipe 12. 2B, pipe outlet 24 of recovery pipe 12 is located above liquid level 18 of plasma raw material 5 and does not come into contact with plasma raw material 5. Therefore, plasma raw material 5 does not enter the inside of recovery pipe 12. The plasma raw material 5 flowing through the recovery pipe 12 flows out from the pipe outlet 24 into the raw material supply space S 1 and collides with a liquid surface 18 of the plasma raw material 5 contained in the reservoir 10 .

[0066] 2B, no erosion was observed in the entire area of ​​the inner wall, including bent section 29 of recovery pipe 12. However, erosion occurred on the inner wall of reservoir 10 in area R near the position where liquid level 18 of plasma raw material 5 and plasma raw material 5 flowing in from recovery pipe 12 collide. Therefore, it is possible to obtain the knowledge that the cause of the erosion may be something other than the action of stress caused by the heat and flow of the plasma raw material 5.

[0067] 3A uses a straight recovery pipe 12 without any bent portions. The recovery pipe 12 is connected to the recovery side connection hole 16 such that the pipe outlet 24 protrudes further toward the inside of the reservoir 10 than the recovery side connection hole 16 of the reservoir 10. Furthermore, the position of liquid level 18 of plasma raw material 5 is set below pipe outlet 24 of recovery pipe 12, but at a position that does not contact pipe outlet 24. Therefore, plasma raw material 5 does not enter the inside of recovery pipe 12. The plasma raw material 5 flowing through the recovery pipe 12 flows out from the pipe outlet 24 into the raw material supply space S 1 and collides with a liquid surface 18 of the plasma raw material 5 contained in the reservoir 10 .

[0068] In the configuration shown in Fig. 3A, the position where the plasma raw material 5 flowing in from the recovery piping 12 collides with the liquid surface 18 is closer to the center (inner side) of the reservoir 10 than in the configuration shown in Fig. 2A. That is, in the configuration shown in Fig. 3A, the position where the outflowing plasma raw material 5 collides with the liquid surface 18 is farther from the inner wall of the reservoir 10 (the inner wall near the recovery side connecting hole 16) than in the configuration shown in Fig. 2B. In the configuration shown in FIG. 3A, no erosion was observed on the inner wall of the recovery pipe 12 or the inner wall of the reservoir 10.

[0069] 3B uses a straight recovery pipe 12 with no bent portions, similar to the configuration shown in Fig. 3A. Meanwhile, the recovery pipe 12 communicates with the reservoir 10 at a position where the plasma raw material 5 contained in the reservoir 10 enters the inside of the recovery pipe 12. This configuration was the one considered when performing a simulation of pressure fluctuations, which will be described later.

[0070] The inventors further investigated the location of erosion in the configurations shown in Figures 2A and 2B and Figure 3A. As a result of examining literature on cavitation erosion tests on various materials, they found that cavitation erosion occurs in TiN materials. In other words, they found that TiN materials have low impact resistance.

[0071] The investigation results shown in Figures 2A and 2B reveal that the location where erosion occurs is near the area where the liquid level 18 (30) of the plasma raw material 5 stored in the reservoir 10 (raw material supply space S1) collides with the flow of plasma raw material 5 recovered from the container 6 flowing inside the recovery pipe 12. Therefore, rather than erosion occurring because the flow direction of the plasma raw material 5 flowing through the recovery pipe 12 changes due to the bending of the pipe, it is believed that the position of erosion changes in accordance with the position of the liquid surface 18 (30) of the liquid plasma raw material 5. Based on the findings from this experiment and the finding that TiN material has low impact resistance, the present inventors have arrived at the following new findings. That is, the TiN film is destroyed, pipes are broken, and part of the inner wall of the reservoir 10 is damaged because the pressure fluctuation (impact) caused by the collision between the liquid level 18 (30) of the plasma raw materials 5 stored in the reservoir 10 and the plasma raw materials 5 recovered from the container 6 flowing through the recovery pipe 12 places a mechanical load on the inner wall of the circulation path near the collision point. As a result, the TiN film applied to the inner wall of the circulation path is destroyed, and the inner wall surface in that area is corroded and deformed, and in some cases erosion such as the opening of holes occurs. For example, if a hole appears in the inner wall of the circulation path, the plasma raw material 5 will flow into that area and, if it becomes thermally connected to the external insulating structure, the temperature of the plasma raw material 5 will drop below its melting point. This will cause the plasma raw material 5 to solidify, causing problems such as the circulation of the plasma raw material stopping.

[0072] In order to confirm the newly derived findings, the inventors conducted a simulation analysis of the distribution of the magnitude of pressure fluctuations (impact) caused by collision between the liquid level 18 (30) of the plasma raw material 5 stored in the reservoir 10 and the plasma raw material 5 flowing through the recovery pipe 12 in each of the configurations shown in Figures 2A, 3A, and B.

[0073] FIG. 4 is a schematic diagram showing the simulation results. FIG. 4A shows simulation results corresponding to the configuration of FIG. 2A. FIG. 4B shows simulation results corresponding to the configuration of FIG. 3B. FIG. 4C shows simulation results corresponding to the configuration of FIG. 3A. 4A to 4C show the distribution of pressure fluctuations when the connection portion between recovery pipe 12 and reservoir 10 is viewed from below.

[0074] As shown in Figure 4A, area T where pressure fluctuations (impacts) are large exists in area U where liquid level 18 (30) of the plasma raw materials 5 stored in reservoir 10 collides with the flow of recovered plasma raw materials 5 flowing through recovery pipe 12. The distribution of areas T where pressure fluctuations (impacts) are large almost coincided with the position of area R where erosion was confirmed, as shown in Figure 2A.

[0075] As shown in Figure 4B, part T where the pressure fluctuations (impact) are large exists in region U where liquid level 18 (30) of the plasma raw materials 5 stored in reservoir 10 collides with the flow of recovered plasma raw materials 5 flowing through recovery pipe 12. From the results in Figure 4B, it can be seen that even if there are no bent parts in recovery pipe 12, when plasma raw materials 5 enters recovery pipe 12, pressure fluctuations are concentrated at liquid level 18 (30) of the plasma raw materials 5. Therefore, when investigating the location of erosion in the configuration shown in FIG. 3B, it is believed that erosion occurs near the position of liquid level 30 in recovery pipe 12, similar to the configuration shown in FIG. 2A.

[0076] 3A, there were multiple dispersed areas V where the pressure fluctuations (impacts) were relatively large, located near the area on inner wall 32 of reservoir 10 where liquid level 18 of the plasma raw materials 5 stored in reservoir 10 collided with the flow of recovered plasma raw materials 5 flowing through recovery pipe 12. Meanwhile, although pressure fluctuations were observed inside recovery pipe 12, no areas of large pressure fluctuations (impacts) like those seen in Figures 4A and B were identified. This corresponds well to the fact that no eroded areas were observed in either the recovery pipe 12 or the inner wall of the reservoir 10 in FIG. 3A.

[0077] Through the above considerations and investigations, the inventors have newly discovered that, in the plasma raw material supply mechanism 1, damage to specific parts of the piping (recovery piping 12) and the container wall (inner wall) in the raw material supply space of the reservoir 10 is caused by impact accompanying pressure fluctuations resulting from a collision between the liquid level 18 (30) of the plasma raw material 5 stored in the reservoir 10 and the flow of recovered plasma raw material 5 flowing through the recovery piping 12. For example, during operation of the EUV light source device 2, the collisions described above occur continuously for a long period of time, and therefore the location described above is subjected to impacts continuously for a long period of time. Covalent inorganic solid materials (e.g., TiN) applied to the surfaces of piping and container walls function to provide corrosion resistance to the plasma raw material 5 with which they come into contact, but are thought to be insufficient in terms of long-term resistance to such continuous impacts.

[0078] [Protective material] Based on the newly discovered facts, the present inventors have devised a new configuration using a protective member as an effective configuration for preventing the occurrence of erosion. 5A and 5B are schematic diagrams showing an example of a configuration using a protective member. FIG. 5A is a configuration corresponding to that shown in FIG. 2A. FIG. 5B is a configuration corresponding to the configuration shown in FIG. 3B.

[0079] 5A and 5B, protective member 34 is disposed so as to cover a portion of the inner wall of recovery pipe 12 that corresponds to the position where plasma raw materials 5 flowing through recovery pipe 12 collide with plasma raw materials 5 contained in reservoir 10. Protective member 34 is also disposed on a protective film formed on the inner wall of recovery pipe 12. The position at which the plasma raw material 5 collides is the position of the liquid level 30 of the liquid metal entering the recovery pipe 12. As mentioned above, typically, the position of the liquid level 30 of the plasma raw material 5 that has entered the recovery pipe 12 is the same as the liquid level 18 of the plasma raw material 5 that has not entered the recovery pipe 12. The present invention is applicable even when the position of the liquid level 30 of the plasma raw material 5 that has entered the recovery pipe 12 is different from the liquid level 18 of the plasma raw material 5 that has not entered the recovery pipe 12.

[0080] The portion of the inner wall of recovery pipe 12 that corresponds to the position where plasma raw material 5 collides is the portion that contacts liquid surface 30 of plasma raw material 5 entering recovery pipe 12. A protective member 34 is placed to cover this portion. For example, the area to be protected is determined to be the area that will receive an impact due to pressure fluctuations caused by the collision of the plasma raw material 5, based on the portion of the plasma raw material 5 that is in contact with the liquid surface 30 entering the recovery pipe 12. A protective member 34 is arranged to cover this area to be protected. Alternatively, a protective member 34 of a predetermined size may be placed so as to cover at least the portion of the plasma raw material 5 that is in contact with the liquid surface 30 entering the recovery pipe 12, without setting a particular area to be protected.

[0081] 5A and 5B, a member having a hollow cylindrical shape is used as the protective member 34. That is, the protective member 34 is hollow and configured in a hollow cylindrical shape. The protective member 34 is inserted into the recovery pipe 12 so that the protective member 34 is entirely contained within the recovery pipe 12. Protective member 34 has an inlet 35 through which plasma raw material 5 flows in, and an outlet 36 through which plasma raw material 5 flows out after flowing into protective member 34. Protective member 34 is positioned so that inlet 35 is located above liquid level 30 of the plasma raw material 5, and so that a portion of the lower side of outlet 36 is located below the liquid level 30. Therefore, the protective member 34 is positioned so as to surround the liquid surface 30 of the plasma raw material 5 in the recovery pipe 12, with which the plasma raw material 5 recovered from the container 6 collides. The liquid surface 30 of the plasma raw material 5 in the recovery pipe 12 can also be considered a fluid collision surface. Collision of the plasma raw material 5 with the fluid collision surface (liquid surface 30) occurs in the hollow portion of protective member 34, and the impact of the collision is not transmitted to the outside of protective member 34 (the inner wall of recovery pipe 12). This makes it possible to prevent the impact caused by the pressure fluctuations generated by the collision of the plasma raw material 5 from being transmitted to the protective film formed on the inner wall of recovery pipe 12.

[0082] The material of the protective member 34 is a material having long-term resistance to continuous impacts. For example, the protective member 34 is made of molybdenum (Mo) or a molybdenum alloy. For example, a TZM (Ti-Zr-Mo: titanium zirconium molybdenum) alloy is used as the molybdenum alloy. Other materials may be used. For example, titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), ruthenium (Ru), osmium (Os), iridium (Ir), or an alloy including at least one of these materials may be used.

[0083] As the protective member 34, a deformable sheet member may be inserted into the inside of the recovery pipe 12 in a state where it is deformed so as to fit the inner wall of the recovery pipe 12. When the sheet member is rolled and the ends come into contact with each other or overlap, the sheet member becomes a member having a hollow circular shape. For example, the protective member 34 can be formed by inserting a rolled molybdenum (Mo) sheet having a thickness of about 100 μm. For example, when protective member 34 is placed inside bent portion 29 as shown in FIG. 5A, protective member 34 can be easily placed at the position of bent portion 29 by rolling up the sheet member and inserting it. In other words, by using a sheet member, it becomes possible to easily place the protective member 34 at a desired position in the manner of a stent, even for recovery pipe 12 that is not configured in a straight line. Of course, the present invention is not limited to this, and a hollow tubular member may be used as the protective member 34 and inserted into the recovery pipe 12 .

[0084] Furthermore, a component other than a cylindrical component that fits along the entire circumference of the inner wall of the recovery pipe 12 may be used as the protective member 34. For example, there may be cases where the portion of the inner wall of the recovery pipe 12 that comes into contact with the liquid surface 30 of the plasma raw material 5 does not exist over the entire 360-degree circumference. In such cases, for example, a concave protective member 34 that covers an area within a predetermined angular range rather than a cylindrical shape may be used. For example, a sheet member that has been rolled up and inserted into recovery pipe 12 may end up becoming concave rather than cylindrical as a result of trying to restore its original shape inside recovery pipe 12. Even in such a case, the sheet member will function satisfactorily as protective member 34 by covering the portion of the inner wall of recovery pipe 12 that comes into contact with liquid surface 30 of plasma raw material 5.

[0085] The size (length) and other factors of the protective member 34 may be set arbitrarily. Typically, as described above, the protective member 34 is configured with a size capable of covering an area (protection target area) determined to receive an impact accompanying pressure fluctuations caused by the collision of the plasma raw material 5. For example, it is possible to set the size of the protection member 34 by setting the area to be protected based on the possible positions of the fluid collision surface (liquid surface 30). For example, the liquid level of the plasma raw material 5 in the reservoir 10 may fluctuate during the circulation operation in which the plasma raw material 5 is returned to the container 6 of the plasma source 3 and collected from the container 6. In response to this fluctuation in the liquid level, a protection area is set, and a protective member 34 having a size capable of covering the protection area is installed. This makes it possible to configure the protective member 34 so as to respond to fluctuations in the liquid level without transmitting impacts to the outside of the protective member 34 (the inner wall of the recovery pipe).

[0086] For example, the liquid level of the plasma raw material 5 contained in the reservoir 10 may be maintained substantially constant based on the detection results of a level sensor. In this case, for example, an area offset above and below the maintained liquid level is set as the area to be protected, and the protective member 34 is configured with a size capable of covering the area to be protected. 5A and 5B, the plasma raw material 5 may be stored in the reservoir 10 so as to allow a certain fluctuation range. In this case, the protected area is set based on the position of the uppermost end level TL, where the liquid level is located at the uppermost side, and the position of the lowermost end level BL, where the liquid level is located at the lowermost side. For example, the area from a position offset upward from the position of the top end level TL to a position offset downward from the position of the bottom end level BL is set as the area to be protected, and the protective member 34 is configured to a size capable of covering the area to be protected.

[0087] By increasing the size (length) of the protective member 34, it becomes possible to protect a larger area within the recovery pipe 12. On the other hand, by making the size (length) of the protective member 34 the minimum necessary, it is possible to reduce the cost of parts. For example, a protective member 34 having a diameter of 30 mm and a length of 50 mm is used, although the size is not limited to this.

[0088] In a configuration in which the protective member 34 is not installed, damage within the recovery pipe 12 (destruction of the TiN film applied inside and subsequent damage to the pipe) could occur after several G shots of emitting EUV pulse radiation from the EUV light source device 2. In contrast, in the configuration in which the protective member 34 was installed, no damage occurred inside the recovery pipe 12 even after four times the above-mentioned several G shots. Therefore, by using the protective member 34, it is possible to prevent erosion by the plasma raw material 5.

[0089] 6A and 6B are schematic diagrams showing other configuration examples using the protective member 34. In the configuration shown in FIG. In the example shown in FIG. 6A, when the liquid level of the plasma raw material 5 reaches the lowest end level BL, the pipe outlet 24 of the recovery pipe 12 is no longer in contact with the plasma raw material 5 contained in the reservoir 10. In such a state, if the position where the plasma raw material 5 flowing in from the recovery pipe 12 collides with the liquid surface 18 is close to the inner wall of the reservoir 10, as shown in FIG. 2B, there is a high possibility that erosion will occur on the inner wall of the reservoir 10. On the other hand, as shown in FIG. 3A, if the position where the plasma raw material 5 flowing in from the recovery pipe 12 collides with the liquid surface 18 is far from the inner wall of the reservoir 10, no erosion occurs on the inner wall of the reservoir 10. Therefore, by positioning the outflow position of the plasma raw material 5 from the recovery pipe 12 away from the inner wall of the reservoir 10, it is possible to prevent the inner wall of the reservoir 10 from being eroded.

[0090] 6A, protective member 34 inserted into recovery pipe 12 is disposed so as to protrude from pipe outlet 24 of recovery pipe 12 toward the inside of reservoir 10. The portion of protective member 34 protruding from pipe outlet 24 is also referred to as protruding portion 41. The tip of the protruding portion 41 becomes the outlet 36 through which the plasma raw material 5 flowing out from the piping outlet 24 flows toward the plasma raw material 5 contained in the reservoir 10 .

[0091] It is possible to move the outflow position of the plasma raw material 5 away from the inner wall of the reservoir 10 by the length of the protruding portion 41 of the protective member 34. As a result, it is possible to move the position where the plasma raw material 5 flowing in from the recovery pipe 12 collides with the liquid surface 18 away from the inner wall of the reservoir 10, making it possible to prevent erosion of the inner wall of the reservoir 10.

[0092] 6A surrounds the fluid collision surface when the liquid level of the plasma raw material 5 moves upward, making it possible to prevent erosion of the inner wall of the recovery pipe 12. Furthermore, when the liquid level of the plasma raw material 5 moves downward, it functions to move the outflow position of the plasma raw material 5 away from the inner wall of the reservoir 10. The protective member 34 shown in FIG. 6A can also be regarded as a member for moving the outflow position or a member for extending the recovery pipe. The size (length) of the protective member 34 may be appropriately designed so as to prevent erosion of the inner wall of the recovery pipe 12 and to keep the outflow position of the plasma raw material 5 sufficiently far from the inner wall of the reservoir 10.

[0093] As shown in FIG. 6A, when the plasma raw material 5 flowing out from outlet 36 of protective member 34 collides with liquid surface 18, splashes 42 of the plasma raw material 5 may be generated. As described above, the raw material supply space S1 of the reservoir 10 is provided with a plasma raw material refill port for refilling the plasma raw material 5. If splashes 42 generated when the plasma raw material 5 collides with the liquid surface 18 adhere to and accumulate at the filling opening of the plasma raw material replenishment port, it becomes difficult to replenish the raw material supply space S1 with plasma raw material 5.

[0094] In order to prevent such problems, it is preferable to configure the protective member 34 so that its tip is parallel to the liquid surface 18 of the plasma raw material 5 in the reservoir 10, as shown in FIG. 6B. That is, the end face 43 of the protruding portion 41 , which extends in a direction inclined with respect to the liquid surface 18 of the plasma raw material 5 contained in the reservoir 10 , where the outlet 36 is formed, is configured to be parallel to the liquid surface 18 . With this configuration, it is possible for a larger area of ​​the fluid collision surface (liquid surface 18) to be covered from above by end surface 43 of protective member 34. As a result, some of the splashes 42 penetrate into protective member 34, reducing the amount that reaches the filling opening of the plasma raw material replenishment port. As a result, it is possible to prevent the problem that it becomes difficult to supply the plasma raw material 5 to the raw material supply space S1 of the reservoir 10 via the plasma raw material refill port. Any other configuration that prevents droplets 42 of the plasma raw material 5 from reaching the filling opening of the port for refilling the plasma raw material may be employed. For example, the end face 43 of the protective member 34 may be configured to be at a slight oblique angle with respect to the liquid level 18. On the other hand, by configuring the end face 43 of the protective member 34 to be parallel to the liquid level 18, the processing and design of the protective member 34 becomes easier, and the manufacturing cost of the protective member 34 can be reduced.

[0095] As described above, in the plasma raw material supply mechanism 1 and EUV light source device 2 according to this embodiment, a protective member 34 is arranged on the inner wall of the recovery pipe 12. The protective member 34 is arranged so as to cover the portion corresponding to the position where the plasma raw material 5 flowing through the recovery pipe 12 and the plasma raw material 5 contained in the reservoir 10 collide. This makes it possible to prevent the recovery pipe 12 from being eroded by the plasma raw material 5.

[0096] Furthermore, by applying the present invention, it is possible to improve the impact resistance of the inner wall of the recovery pipe 12 without changing the design of the recovery pipe 12. This makes it possible to protect the TiN coating formed on the inner wall of the recovery pipe 12, and to prevent corrosion of the recovery pipe 12. As a result, it is possible to extend the life of the recovery pipe 12, and to realize a longer life for the cooling system. This also leads to the realization of a longer service life for the plasma raw material supply mechanism 1 and the EUV light source device 2.

[0097] [EUV light source device] An example of the basic configuration and operation of an EUV light source device will be described. 7 is a cross-sectional view showing the inside of a chamber and a connecting chamber of an extreme ultraviolet light source device (EUV light source device) cut horizontally. Note that an LDP type EUV light source device is used as an example. In the following description, in order to facilitate understanding of the EUV light source device, some elements already described above will be described again with new reference symbols.

[0098] The EUV light source device 2 emits extreme ultraviolet light (EUV light). The wavelength of this extreme ultraviolet light is, for example, 13.5 nm. The EUV light corresponds to one embodiment of radiation according to the present invention. The EUV light source device 2 irradiates liquid-phase plasma raw materials SA and SB, which are supplied to the surfaces of a pair of discharge electrodes EA and EB, respectively, which generate a discharge, with an energy beam such as a laser beam LB, thereby vaporizing the plasma raw materials SA and SB. After that, a plasma P is generated by discharge in a discharge region D between the discharge electrodes EA and EB. EUV light is emitted from the plasma P.

[0099] The EUV light source device 2 can be used, for example, as a light source device for a lithography apparatus in semiconductor device manufacturing, or as a light source device for an inspection apparatus for a mask used in lithography. For example, when the EUV light source device 2 is used as a light source device for a mask inspection device, a portion of the EUV light emitted from the plasma P is extracted and guided to the mask inspection device. The mask inspection device performs mask blank inspection or pattern inspection using the EUV light emitted from the EUV light source device 2 as inspection light. Here, the use of EUV light makes it possible to support 5 nm to 7 nm processes. Note that the EUV light extracted from the EUV light source device 2 is regulated by an opening (not shown) provided in the heat shield 65 in FIG. 7.

[0100] As shown in FIG. 7, the EUV light source device 2 has a light source unit 52 and a debris trap unit 53. The light source unit 52 generates EUV light based on the LDP method. The debris trap 53 is a debris mitigation device that traps debris scattered together with the EUV light emitted from the light source 52. Debris generated by the light source 52 and debris captured by the debris trap 53 are stored in a debris storage unit (not shown) located below the debris trap 53.

[0101] The light source unit 52 includes a chamber 54 that isolates the plasma P generated inside from the outside. The chamber 54 forms a plasma generation chamber that accommodates the light source unit 52 that generates the plasma P. The chamber 54 is a rigid vacuum housing made, for example, of metal, and its interior is maintained at a reduced pressure of a predetermined pressure or less by a vacuum pump (not shown) in order to effectively generate discharges for heating and exciting the plasma raw materials SA and SB and to suppress attenuation of the EUV light.

[0102] The light source unit 52 includes a pair of discharge electrodes EA and EB. The discharge electrodes EA, EB are disk-shaped members of the same shape and size. For example, the discharge electrode EA is used as a cathode, and the discharge electrode EB is used as an anode. The discharge electrodes EA, EB are formed from a high melting point metal such as molybdenum (Mo), tungsten (W) or tantalum (Ta). The discharge electrodes EA, EB are disposed at positions spaced apart from each other, with the peripheral portions of the discharge electrodes EA, EB close to each other. At this time, the discharge region D where the plasma P is generated is located in the gap between the discharge electrodes EA, EB where the peripheral portions of the discharge electrodes EA, EB are closest to each other.

[0103] Inside the chamber 54, there are disposed a container CA in which liquid phase plasma raw material SA is stored, and a container CB in which liquid phase plasma raw material SB is stored. Heated liquid-phase plasma raw materials SA and SB are supplied to the containers CA and CB, respectively. The liquid-phase plasma raw materials SA and SB are, for example, tin (Sn), but may also be lithium (Li).

[0104] The container CA contains the plasma raw material SA such that the lower part of the discharge electrode EA is immersed in the liquid phase plasma raw material SA, and the container CB contains the plasma raw material SB such that the lower part of the discharge electrode EB is immersed in the liquid phase plasma raw material SB. Therefore, the liquid phase plasma raw materials SA, SB adhere to the lower parts of the discharge electrodes EA, EB. As the discharge electrodes EA, EB rotate, the liquid phase plasma raw materials SA, SB adhering to the lower parts of the discharge electrodes EA, EB are transported to the discharge region D where the plasma P is generated.

[0105] The discharge electrode EA is connected to a rotating shaft JA of the motor MA and rotates about the axis of the discharge electrode EA. The discharge electrode EB is connected to a rotating shaft JB of the motor MB and rotates about the axis of the discharge electrode EB. The motors MA, MB are disposed outside the chamber 54, and the rotating shafts JA, JB of the motors MA, MB extend from the outside to the inside of the chamber 54. The gap between the rotating shaft JA and the wall of the chamber 54 is sealed by a seal member PA, and the gap between the rotating shaft JB and the wall of the chamber 54 is sealed by a seal member PB. The seal members PA, PB are, for example, mechanical seals. The seal members PA, PB support the rotary shafts JA, JB rotatably while maintaining the reduced pressure atmosphere in the chamber 54.

[0106] As shown in FIG. 7, the EUV light source device 2 further includes a control unit 55, a pulsed power supply unit 56, a laser source (energy beam irradiation device) 57, and a movable mirror 58. The control unit 55 , the pulsed power supply unit 56 , the laser source 57 and the movable mirror 58 are installed outside the chamber 54 . The control unit 55 controls the operation of each unit of the EUV light source device 2. For example, the control unit 55 controls the rotational drive of the motors MA, MB to rotate the discharge electrodes EA, EB at a predetermined rotation speed. The control unit 55 also controls the operation of the pulsed power supply unit 56, the irradiation timing of the laser beam LB from the laser source 57, etc.

[0107] Two power feed lines QA, QB extending from the pulsed power supply unit 56 pass through feedthroughs FA, FB and are connected to containers CA, CB arranged inside the chamber 54, respectively. The feedthroughs FA and FB are sealing members that are embedded in the walls of the chamber 54 and maintain the reduced pressure atmosphere within the chamber 54. The containers CA, CB are made of a conductive material, and the plasma raw materials SA, SB contained inside the containers CA, CB are also made of a conductive material such as tin. The lower portions of the discharge electrodes EA, EB are immersed in the plasma raw materials SA, SB contained inside each container CA, CB. Therefore, when pulsed power is supplied from pulsed power supply unit 56 to the containers CA, CB, the pulsed power is supplied to the discharge electrodes EA, EB via the plasma raw materials SA, SB, respectively.

[0108] The pulsed power supply unit 56 generates a discharge in the discharge region D by supplying pulsed power to the discharge electrodes EA, EB. The plasma raw materials SA, SB are transported to the discharge region D based on the rotation of the discharge electrodes EA, EB, and are heated and excited by the current flowing between the discharge electrodes EA, EB during discharge, generating a plasma P that emits EUV light.

[0109] The laser source 57 irradiates an energy beam onto the plasma raw material SA attached to the discharge electrode EA transported to the discharge region D, thereby vaporizing the plasma raw material SA. The laser source 57 is, for example, a Nd:YVO4 (Neodymium-doped Yttrium Orthovanadate) laser device. At this time, the laser source 57 emits a laser beam LB in the infrared region with a wavelength of 1064 nm. However, the energy beam irradiation device may be a device that emits an energy beam other than the laser beam LB, so long as it is capable of vaporizing the plasma raw material SA.

[0110] The laser beam LB emitted from the laser source 57 is guided to the movable mirror 58 via focusing means including, for example, a focusing lens 59. The focusing means adjusts the spot diameter of the laser beam LB at the laser beam irradiated position on the discharge electrode EA. The focusing lens 59 and the movable mirror 58 are disposed outside the chamber 54.

[0111] The laser beam LB focused by the focusing lens 59 is reflected by the movable mirror 58, passes through a transparent window 60 provided in the side wall 54a of the chamber 54, and is irradiated onto the peripheral portion of the discharge electrode EA near the discharge region D. By adjusting the attitude of the movable mirror 58, the irradiation position of the laser beam LB on the discharge electrode EA is adjusted.

[0112] In order to facilitate irradiation of the peripheral portion of the discharge electrode EA near the discharge region D with the laser beam LB, the axes of the discharge electrodes EA and EB are not parallel. The distance between the rotating shafts JA, JB is narrower on the motor MA, MB side and wider on the discharge electrode EA, EB side. This allows the opposing surfaces of the discharge electrodes EA, EB to be brought closer together while the side opposite the opposing surfaces of the discharge electrodes EA, EB is moved out of the irradiation path of the laser beam LB, making it easier to irradiate the laser beam LB onto the peripheral portion of the discharge electrode EA near the discharge region D.

[0113] The discharge electrode EB is disposed between the discharge electrode EA and the movable mirror 58. The laser beam LB reflected by the movable mirror 58 passes near the outer circumferential surface of the discharge electrode EB, and then reaches the outer circumferential surface of the discharge electrode EA. At this time, the discharge electrode EB is retracted further toward the motor MB side (to the left in FIG. 7) than the discharge electrode EA so that the laser beam LB is not blocked by the discharge electrode EB. The liquid-phase plasma raw material SA attached to the outer peripheral surface of the discharge electrode EA near the discharge region D is vaporized by irradiation with the laser beam LB, and is supplied to the discharge region D as the gas-phase plasma raw material SA.

[0114] In order to generate plasma P in the discharge region D (to turn the gaseous plasma raw material SA into plasma), the pulsed power supply unit 56 supplies power to the discharge electrodes EA, EB. When the gas phase plasma raw material SA is supplied to the discharge region D by irradiation with the laser beam LB, a discharge is generated between the discharge electrodes EA, EB in the discharge region D. When a discharge occurs between the discharge electrodes EA and EB, the gas-phase plasma material SA in the discharge region D is heated and excited by the electric current, generating a plasma P. The EUV light emitted from the generated plasma P passes through a first window 61, which is a through-hole provided in the side wall 54b of the chamber 54, and enters the debris trap 53.

[0115] The debris trap 53 has a connection chamber 62 arranged on a side wall 54b of the chamber 54. The connection chamber 62 is a rigid body, for example, a vacuum housing made of metal, and the interior thereof is maintained at a reduced pressure below a predetermined pressure in order to suppress attenuation of EUV light, similar to the chamber 54. The connection chamber 62 is connected between the chamber 54 and a utilization apparatus 90 (for example, a lithography apparatus or a mask inspection apparatus).

[0116] The internal space of the connecting chamber 62 communicates with the chamber 54 via the first window 61. The connecting chamber 62 has a second window 63 as a light extraction part that introduces the EUV light incident from the first window 61 to the utilization device 90. The second window 63 is a through hole of a predetermined shape formed in a side wall 62a of the connecting chamber 62. The EUV light emitted from the plasma P in the discharge region D is introduced into the utilization device 90 through the first window portion 61 and the second window portion 63 .

[0117] Meanwhile, debris is dispersed from the plasma P in various directions at high speed along with the EUV light. The debris includes tin particles which are the plasma raw materials SA and SB, and material particles of the discharge electrodes EA and EB which are sputtered as the plasma P is generated. These debris gain large kinetic energy through the contraction and expansion processes of the plasma P. That is, the debris generated from the plasma P includes ions, neutral particles, and electrons that move at high speeds. If such debris reaches utilization device 90, it may damage or contaminate the reflective coatings of optical elements within utilization device 90, reducing performance.

[0118] Therefore, in order to prevent the debris from entering the utilization device 90, a debris trap 53 for trapping the debris is provided in the connection chamber 62. 7, a rotary foil trap 64 having multiple foils and actively colliding the multiple foils with debris by rotating is disposed as the debris capture unit 53. The rotary foil trap 64 is disposed inside the connection chamber 62 on the optical path of the EUV light traveling from the connection chamber 62 to the utilization device 90. A fixed foil trap in which the positions of multiple foils are fixed may be arranged instead of the rotating foil trap 64. Alternatively, both the rotating foil trap 64 and the fixed foil trap may be provided.

[0119] <Other embodiments> The present invention is not limited to the above-described embodiment, and various other embodiments can be realized.

[0120] In the above, an EUV light source device has been given as an example of an embodiment of an operating device that operates using liquid metal, and a case has been described in which the circulation device according to the present invention is configured within the EUV light source device. The application of the present invention is not limited to EUV light source devices, but can be applied to various cooling systems that use liquid metal as a coolant in various applications such as cooling high performance circuits, nuclear reactors, or radiation sources in the X-ray range. For example, the present invention can be applied to fast breeder reactors such as sodium-cooled fast reactors. Furthermore, the circulation mechanism according to the present invention can be applied to various devices that operate using liquid metal, even in systems for purposes other than cooling systems.

[0121] The configurations of the EUV light source device, the circulation mechanism, the protective member, and the like described with reference to the drawings are merely one embodiment, and may be modified as desired without departing from the spirit of the present technology. In other words, any other configuration for implementing the present technology may be adopted.

[0122] In this disclosure, in order to facilitate understanding of the explanation, the words "approximately", "almost", "approximately", etc. are used as appropriate. However, there is no clear difference between using the words "approximately", "almost", "approximately", etc. and not using them. In other words, in the present disclosure, concepts that define shape, size, positional relationship, state, and the like, such as "center," "central," "uniform," "equal," "same," "orthogonal," "parallel," "symmetric," "extending," "axial direction," "cylindrical," "cylindrical," "ring-shaped," and "annular," are concepts that include "substantially central," "substantially central," "substantially uniform," "substantially equal," "substantially the same," "substantially orthogonal," "substantially parallel," "substantially symmetric," "substantially extending," "substantially axial direction," "substantially cylindrical," "substantially cylindrical," "substantially ring-shaped," "substantially annular," and the like. For example, this includes states that are included within a specified range (e.g., a range of ±10%) based on standards such as "perfectly centered," "perfectly central," "perfectly uniform," "perfectly equal," "perfectly the same," "perfectly orthogonal," "perfectly parallel," "perfectly symmetrical," "perfectly extended," "perfectly axial," "perfectly cylindrical," "perfectly cylindrical," "perfectly ring-shaped," "perfectly toric," etc. Therefore, even if the words "approximately", "almost", "roughly", etc. are not added, the concept may be included that can be expressed by adding "approximately", "almost", "approximately", etc. Conversely, a state expressed by adding "approximately", "almost", "approximately", etc. does not necessarily exclude a perfect state.

[0123] In this disclosure, expressions using "more than", such as "greater than A" and "smaller than A", are expressions that comprehensively include both concepts that include equivalent to A and concepts that do not include equivalent to A. For example, "greater than A" is not limited to cases that do not include equivalent to A, but also includes "A or greater." Furthermore, "smaller than A" is not limited to "less than A" but also includes "A or less." When implementing the present technology, specific settings and the like may be appropriately adopted from the concepts included in "greater than A" and "smaller than A" so as to achieve the effects described above.

[0124] It is also possible to combine at least two of the characteristic parts of the present technology described above. That is, the various characteristic parts described in each embodiment may be arbitrarily combined without distinction between the embodiments. In addition, the various effects described above are merely examples and are not limited thereto, and other effects may be exhibited. [Explanation of symbols]

[0125] S1…Raw material supply space 1. Plasma raw material supply mechanism 2...EUV light source device 3. Plasma source 4…Discharge electrode 5...Plasma raw material (liquid metal) 6. Container 10…Reservoir 11…Supply piping 12...Recovery pipe 13…Pump 14…Cooling mechanism 16...Recovery side connection hole 17…Supply side connection hole 18, 30…Liquid metal level 23...Pipe inlet 24…Piping outlet 34...Protective material 35...Inlet 36…Outlet 41...Protrusion 43...End surface constituting the outlet

Claims

1. A circulation mechanism for supplying liquid metal to a light source device that generates plasma that emits radiation from a liquid metal that is a plasma raw material, and emits the radiation, comprising: a container for containing the liquid metal; a supply pipe for supplying the liquid metal contained in the container to the light source device; a recovery pipe that communicates with the container and recovers the liquid metal flowing out from the light source device into the container; a circulation drive unit that moves the liquid metal accommodated in the accommodation unit to the supply pipe to circulate the liquid metal between the light source device and the liquid metal; a protective member arranged to cover a portion of an inner wall of the recovery pipe corresponding to a position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container section collide with each other; Equipped with The protective member is made of a deformable sheet member, and is inserted into the inside of the recovery pipe in a deformed state so as to fit the inner wall of the recovery pipe. Circulation mechanism.

2. The circulation mechanism according to claim 1, The radiation is extreme ultraviolet light. Circulation mechanism.

3. 3. The circulation mechanism according to claim 1 or 2, the recovery pipe is in communication with the storage unit at a position where the liquid metal stored in the storage unit enters the inside of the recovery pipe; The protective member is disposed so as to cover a portion of an inner wall of the recovery pipe that contacts the liquid surface of the liquid metal entering the recovery pipe. Circulation mechanism.

4. 3. The circulation mechanism according to claim 1 or 2, The recovery pipe has a protective film formed on an inner wall of the recovery pipe, The protective member is disposed on the protective film. Circulation mechanism.

5. 3. The circulation mechanism according to claim 1 or 2, The liquid metal is tin, lithium, gadolinium, terbium, gallium, or an alloy containing at least one of these materials. Circulation mechanism.

6. 3. The circulation mechanism according to claim 1 or 2, The protective member is made of molybdenum, titanium, vanadium, chromium, zirconium, niobium, hafnium, tantalum, tungsten, rhenium, ruthenium, osmium, and iridium, or an alloy containing at least one of these materials. Circulation mechanism.

7. 5. The circulation mechanism according to claim 4, The protective film is made of titanium nitride, titanium, or an alloy containing at least one of these materials. Circulation mechanism.

8. 3. The circulation mechanism according to claim 1 or 2, The storage section has a connection hole to which the recovery pipe is connected, The recovery pipe is connected to the connection hole so as to protrude from the connection hole toward the inside of the storage portion. Circulation mechanism.

9. 3. The circulation mechanism according to claim 1 or 2, the recovery pipe has a pipe outlet through which the liquid metal flows out of the container, The protective member has a protruding portion protruding from the piping outlet toward the inside of the storage portion, The protruding portion has an outlet through which the liquid metal flowing out from the piping outlet flows toward the liquid metal contained in the container. Circulation mechanism.

10. 10. The circulation mechanism according to claim 9, The protrusion extends in a direction inclined with respect to the liquid level of the liquid metal contained in the container, and an end face where the outlet is formed is configured to be parallel to the liquid level. Circulation mechanism.

11. 3. The circulation mechanism according to claim 1 or 2, The recovery pipe has a pipe inlet into which the liquid metal flowing out from the light source device flows, and a pipe outlet located below the pipe inlet in the vertical direction and through which the liquid metal flows out to the container, and is disposed at an angle with respect to the container. Circulation mechanism.

12. The circulation mechanism according to claim 1 or 2, further comprising: The liquid metal may be supplied to the supply pipe through a supply line, and the supply pipe through a supply line may be supplied to the supply line through a supply line. Circulation mechanism.

13. A circulation mechanism for supplying liquid metal to a light source device that generates plasma that emits radiation from a liquid metal that is a plasma raw material and emits the radiation, comprising: a container for containing the liquid metal; a supply pipe for supplying the liquid metal contained in the container to the light source device; a recovery pipe that communicates with the container and recovers the liquid metal flowing out from the light source device into the container; a circulation drive unit that moves the liquid metal accommodated in the accommodation unit to the supply pipe to circulate the liquid metal between the light source device and the liquid metal; a protective member arranged to cover a portion of an inner wall of the recovery pipe corresponding to a position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container collide; a level sensor that detects a liquid level of the liquid metal contained in the container; a liquid metal replenishing unit that replenishes the liquid metal to the container unit based on a detection result of the level sensor so that the liquid level is located between a top end level and a bottom end level that are predetermined with respect to the position of the liquid level; Equipped with The protective member is disposed so as to cover a region to be protected, the region including a region of the inner wall of the recovery pipe between a position corresponding to the uppermost end level and a position corresponding to the lowermost end level. Circulation mechanism.

14. A light source unit that generates plasma that emits radiation from a liquid metal that is a plasma raw material and emits the radiation; a container for containing the liquid metal; a supply pipe for supplying the liquid metal contained in the container to the light source unit; a recovery pipe that is in communication with the container and recovers the liquid metal flowing out from the light source unit into the container; a circulation drive unit that moves the liquid metal accommodated in the accommodation unit to the supply pipe to circulate the liquid metal between the accommodation unit and the light source unit; a protective member arranged to cover a portion of an inner wall of the recovery pipe corresponding to a position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container section collide with each other; A circulation mechanism having Equipped with The protective member is made of a deformable sheet member, and is inserted into the inside of the recovery pipe in a deformed state so as to fit the inner wall of the recovery pipe. Light source device.

15. A light source unit that generates plasma that emits radiation from a liquid metal that is a plasma raw material and emits the radiation; a container for containing the liquid metal; a supply pipe for supplying the liquid metal contained in the container to the light source unit; a recovery pipe that is in communication with the container and recovers the liquid metal flowing out from the light source unit into the container; a circulation drive unit that moves the liquid metal accommodated in the accommodation unit to the supply pipe to circulate the liquid metal between the accommodation unit and the light source unit; a protective member arranged to cover a portion of an inner wall of the recovery pipe corresponding to a position where the liquid metal flowing through the recovery pipe and the liquid metal contained in the container collide; a level sensor that detects a liquid level of the liquid metal contained in the container; a liquid metal replenishing unit that replenishes the liquid metal to the container unit based on a detection result of the level sensor so that the liquid level is located between a top end level and a bottom end level that are predetermined with respect to the position of the liquid level; A circulation mechanism having Equipped with The protective member is disposed so as to cover a region to be protected, the region including a region of the inner wall of the recovery pipe between a position corresponding to the uppermost end level and a position corresponding to the lowermost end level. Light source device.

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