Light source device and energy beam introduction member

Abstract

The purpose of the present invention is to provide an energy beam introduction member of a light source device capable of stably introducing an energy beam to a light emission point so that the progress of the light beam is not inhibited.　An energy beam introduction member (3) has a housing part (7), a first window member (8a), a jig (9) fixed to the housing part (7), a second window member (8b), and a gas introduction part (12). The first window member (8a) and the second window member (8b) can pass the energy beam, the first window member (8a) is provided so as to close an incident hole (10a) of the energy beam, and the second window member (8b) is fixed to the jig (9) and positioned in an internal space (S). The gas introduction part (12) introduces gas into a first space (S1) on the incident hole (10a) side with respect to the second window member (8b) in the internal space (S), and the jig (9) has a gas conduction hole that allows the gas to flow from the first space (S1) to a second space (S2) on an emission hole (10b) side with respect to the second window member (8b).

Description

Light source device and energy beam introduction member

[0001] The present invention relates to a light source device that generates X-rays, extreme ultraviolet light, etc., and an energy beam introduction member used in the light source device.

[0002] Extreme ultraviolet light (hereinafter also referred to as "EUV light"), a type of X-ray, has recently been used as exposure light. The substrate of a mask for EUV lithography is formed by patterning a material that absorbs radiation used in EUV lithography on a multilayer film (e.g., molybdenum and silicon) that reflects EUV light.

[0003] Because the size of unacceptable defects in EUV masks has become significantly smaller and more difficult to detect, EUV masks are inspected using actinic inspection, which uses radiation with wavelengths that match the working wavelengths of lithography.

[0004] Generally, EUV light source devices include a DPP (Discharge Produced Plasma) light source device, an LDP (Laser Assisted Discharge Produced Plasma) light source device, and an LPP (Laser Produced Plasma) light source device.

[0005] A DPP light source device applies a high voltage between electrodes to which a gaseous plasma raw material (discharge gas) containing EUV radiation species is supplied, generating a high-density, high-temperature plasma through discharge, and utilizes the extreme ultraviolet light emitted from the plasma.

[0006] An LDP light source device is an improved version of a DPP light source device, and for example, it supplies a liquid high-temperature plasma raw material (e.g., Sn (tin) or Li (lithium)) containing EUV radiating species to the surface of an electrode (discharge electrode) that generates a discharge, irradiates the raw material with a laser beam to vaporize the raw material, and then generates high-temperature plasma by discharge.

[0007] An LPP light source device generates high-temperature plasma by exciting an EUV radiating species with a laser beam, etc. A known light source device of this type generates plasma by focusing a laser beam onto droplets of high-temperature plasma raw material ejected in the form of minute droplets, thereby exciting the target material.

[0008] Patent Document 1 proposes a method of obtaining radiation by supplying a plasma raw material for generating radiation such as X-rays or EUV to a rotor and irradiating the region of the rotor to which the plasma raw material has been supplied with an energy beam (laser beam). A cylindrical container with one open end is used as the rotor, and liquid plasma raw material is supplied to this container, and laser light is irradiated onto the inner peripheral surface of the container.

[0009] This method corresponds to the so-called LPP method, but instead of supplying liquid plasma raw material as droplets, it uses the centrifugal force of a rotor to supply the liquid plasma raw material to the area irradiated by the energy beam. Therefore, compared to methods such as focusing a laser beam on droplets, it is possible to obtain high-intensity radiation with a relatively simple configuration.

[0010] JP 2014-216286 A

[0011] In a light source device such as that disclosed in Patent Document 1, there is a demand for a technology that enables an energy beam to be introduced to a light-emitting point without being hindered in its travel.

[0012] In view of the above circumstances, an object of the present invention is to provide a light source device and an energy beam introduction member that enable an energy beam to be stably introduced to a light-emitting point without impeding its progression.

[0013] To achieve the above object, a light source device according to one aspect of the present technology converts a liquid raw material into plasma by irradiating it with an energy beam to extract radiation, and includes an energy beam introducing member. The energy beam introducing member includes a housing, a first window member, a jig, a second window member, and a gas introducing member. The housing has an entrance hole and an exit hole for the energy beam, and an internal space through which the energy beam passes. The first window member is configured to allow the energy beam to pass through and to block the entrance hole. The jig is fixed to the housing and is located in the internal space. The second window member is configured to allow the energy beam to pass through, is fixed to the jig, and is located in the internal space. The gas introducing member introduces a gas into the first space, when a space on the entrance hole side of the second window member is defined as a first space and a space on the exit hole side of the internal space is defined as a second space, based on the second window member. The jig has a gas introduction hole that allows the gas to pass from the first space to the second space.

[0014] In this light source device, an energy beam passes through the energy beam introducing member in the order of a first window member, a second window member, and an exit hole. The first window member closes the entrance hole, and the second window member is fixed to a jig fixed to the housing. Gas is introduced into the space on the entrance hole side, and a gas introduction hole is provided in the jig. This allows the energy beam to be stably introduced to the light-emitting point without being hindered in its travel.

[0015] The light source device may further include a heating mechanism that heats the vicinity of the emission hole of the housing portion.

[0016] The heating mechanism may be a debris mitigation mechanism that captures debris generated from the plasma.

[0017] The jigs may include a first jig on the entrance hole side and a second jig on the exit hole side, with the second window member as a reference. In this case, the second window member may be fixed by being sandwiched between the first jig and the second jig.

[0018] The first jig may have a ring shape, in which case the second window member may have a disk shape and a diameter larger than an inner diameter of the first jig and smaller than an outer diameter of the first jig.

[0019] At least the surface of the second window member on the side of the emission hole may not have an anti-reflection film.

[0020] The second window member may be made of a material containing at least one of calcium fluoride and magnesium fluoride.

[0021] The second window member may be made of at least one of a low expansion coefficient material and glass.

[0022] The gas inlet may be a hole formed in the housing.

[0023] The energy beam introduction member may have debris guiding means for guiding debris generated from the plasma and entering the internal space through the exit hole to a position different from the second window member.

[0024] The debris guiding means may be means for guiding the debris to a buffer space, which is a space configured at a position different from the second window member.

[0025] The debris guiding means may be a means for guiding the debris by evacuating the internal space.

[0026] The debris guiding means may be means for guiding the debris by blowing gas from the outside of the energy beam introduction member toward the internal space.

[0027] An energy beam introduction member according to an aspect of the present technology includes the housing, the first window member, the jig, the second window member, and the gas introduction part.

[0028] According to the present invention, it is possible to stably introduce an energy beam to a light-emitting point without impeding its travel. Note that the effects described herein are not necessarily limited to those described herein, and any of the effects described in this disclosure may be employed.

[0029] FIG. 1 is a schematic diagram showing a configuration example of a light source device 100 according to the present embodiment. FIG. 2 is a schematic diagram showing a configuration example of the interior of a chamber main body 109. FIG. 3 is a schematic diagram showing a configuration example of a laser port 3. FIG. 4 is a schematic diagram showing a configuration example of a pressure holder 9a. FIG. 5 is a schematic diagram showing an example of debris guiding means. FIG. 6 is a schematic diagram showing an example of debris guiding means. FIG. 7 is a schematic diagram showing a variation of a jig. FIG. 8 is a schematic diagram showing a variation of a gas introducing hole 18.

[0030] First Embodiment A first embodiment according to the present technology will be described below with reference to the drawings.

[0031] [Basic Configuration of Light Source Device] Figure 1 is a schematic diagram showing an example configuration of a light source device 100 according to this embodiment. The light source device 100 is an LPP-type light source device. That is, the light source device 100 is a device that irradiates a plasma raw material 101 with an energy beam EB, thereby exciting the plasma raw material 101 to generate plasma P, and extracts radiation R emitted from the plasma P to use as a light source. The radiation R is EUV light, X-rays, or other electromagnetic waves.

[0032] The plasma raw material 101 is a molten metal or alloy, such as liquid-phase tin (Sn), lithium (Li), gadolinium (Gd), terbium (Tb), gallium (Ga), bismuth (Bi), indium (In), or an alloy containing at least one of these materials. The plasma raw material 101 corresponds to one embodiment of a liquid raw material.

[0033] FIG. 1 is a diagram showing a schematic cross section of the light source device 100 taken along the horizontal direction at a predetermined height from the installation surface, as viewed from vertically above. In FIG. 1 , cross sections not necessary for explaining the cross-sectional configuration, etc., are omitted to facilitate understanding of the configuration and operation of the light source device 100. Hereinafter, the X direction may be referred to as the left-right direction of the horizontal direction (the positive side of the X axis is the right side, and the negative side is the left side), the Y direction as the front-rear direction of the horizontal direction (the positive side of the Y axis is the front side, and the negative side is the rear side), and the Z direction as the vertical direction (the positive side of the Z axis is the upper side, and the negative side is the lower side). Of course, the application of the present technology is not limited to the orientation in which the light source device 100 is used.

[0034] As shown in FIG. 1, the light source device 100 includes a housing 102, a vacuum chamber 103, an energy beam entrance chamber 104, a radiation exit chamber 105, a plasma generation mechanism 106, a control unit 107, and a beam source 108.

[0035] 1 , the housing 102 has an exit hole 102a, an entrance hole 102b, and a through-hole 102c. In this embodiment, the exit axis EA of the radiation R is set so as to pass through the exit hole 102a. The radiation R is extracted along the exit axis EA and emitted from the exit hole 102a. In this embodiment, the entrance axis IA of the energy beam EB is set so as to pass through the entrance hole 102b.

[0036] 1, a beam source 108 that emits an energy beam EB is installed outside the housing 102. The beam source 108 is installed so that the energy beam EB enters the inside of the housing 102 along an incident axis IA. An electron beam or laser light can be used as the energy beam EB.

[0037] The light source device 100 is provided with a chamber section C including a plurality of chambers. Specifically, the chamber section C includes a vacuum chamber 103, an energy beam incident chamber (hereinafter simply referred to as an incident chamber) 104, and a radiation exit chamber (hereinafter simply referred to as an exit chamber) 105. The vacuum chamber 103 and the incident chamber 104 are connected to each other, and the vacuum chamber 103 and the exit chamber 105 are also connected to each other.

[0038] The entrance chamber 104 is configured to be located on an entrance axis IA of the energy beam EB, and the exit chamber 105 is configured to be located on an exit axis EA of the radiation R. A collector (condensing mirror) 112 that guides the radiation R is disposed within the exit chamber 105. Furthermore, a plasma generation mechanism 106 that generates plasma P is disposed within the vacuum chamber 103.

[0039] A utilization device such as a mask inspection device is connected to the end of the extraction chamber 105 opposite the plasma generation mechanism 106. In the example shown in FIG. 1 , an application chamber 110 is connected as a chamber forming part of the utilization device. The pressure inside the application chamber 110 may be atmospheric pressure. Furthermore, the interior of the application chamber 110 may be purged by introducing a gas (e.g., an inert gas) through a gas injection path as needed, and then evacuated by an exhaust means (not shown). A filter film 111 and an opening are provided between the application chamber 110 and the extraction chamber 105 to physically separate the region where the plasma P is generated from the application chamber 110.

[0040] The chamber body 109 is provided with an entrance window 114. The entrance window 114 is arranged at a position aligned with the entrance hole 102b on the entrance axis IA of the energy beam EB. An exhaust pump 117 is also connected to the chamber body 109.

[0041] 1, the extraction chamber 105 and the incidence chamber 104 are provided with gas injection paths 116a and 116b, respectively, and gas is supplied from a gas supply device (not shown) to the extraction chamber 105 and the incidence chamber 104. A gas having a high transmittance to the radiation R, such as argon or helium, is supplied to the extraction chamber 105. A gas having a high transmittance to the energy beam EB, such as argon or helium, is supplied to the incidence chamber 104.

[0042] The plasma generation mechanism 106 is a mechanism for generating plasma P in the vacuum chamber 103 and emitting radiation R (X-rays or EUV light). As shown in FIG. 1 , the plasma generation mechanism 106 includes a rotating body 20, and an energy beam EB is incident on the rotating body 20. The rotating body 20 is disposed in the vacuum chamber 103 so that an irradiation position I of the energy beam EB is located at the intersection of an entrance axis IA and an exit axis EA.

[0043] A shaft member 72 is connected to the center of the rear surface (the surface on the negative side of the Y axis) of the rotating body 20. The shaft member 72 is disposed so as to penetrate the chamber main body 109 and the housing 102. A motor 71 is disposed outside the housing 102, and is connected to the end of the shaft member 72 on the side that is not connected to the rotating body 20.

[0044] When the motor 71 is driven, the shaft member 72 and the rotating body 20 rotate integrally. The direction of rotation is indicated by an arrow in FIG. 1 . In this example, the rotating body 20 rotates counterclockwise when viewed from the positive side of the Y axis, but it may also rotate clockwise. In this example, a mechanical seal 73 is provided at the portion of the chamber main body 109 where the shaft member 72 passes through. This allows smooth rotation while maintaining the airtightness of the vacuum chamber 103.

[0045] The plasma generation mechanism 106 also has a raw material container 21. The raw material container 21 stores plasma raw material 101, and the lower side of the rotor 20 is immersed in the stored plasma raw material 101.

[0046] As rotor 20 rotates, plasma raw material 101 is lifted up while adhering to rotor 20. This ensures that plasma raw material 101 is always attached to the surface of rotor 20. Furthermore, energy beam EB is irradiated from beam source 108 onto the attached plasma raw material 101. As a result, plasma P is generated at irradiation position I.

[0047] The control unit 107 controls the operation of each component of the light source device 100. For example, the control unit 107 controls the operation of the beam source 108 and the exhaust pump 117. In Fig. 1, the control unit 107 is illustrated schematically as a functional block, but the position where the control unit 107 is configured may be designed arbitrarily.

[0048] 1 , in this embodiment, a radiological diagnostic unit 119 is connected to the chamber body 109. The radiological diagnostic unit 119 is disposed at a position where the radiation R emitted in a direction different from the emission axis EA of the radiation R is incident, and measures the state of the radiation R emitted from the plasma P.

[0049] [Vacuum Chamber] Figure 2 is a schematic diagram showing an example of the internal configuration of the chamber main body 109. Figure 2 shows the interior of the chamber main body 109 as viewed from above, with the right side of Figure 1 facing downward. Inside the chamber main body 109, a rotating body 20, a shaft member 72, a light source cover 1, a DMT 2, and a laser port 3 are arranged. Note that Figure 1 omits the illustration of the light source cover 1, the DMT 2, and the laser port 3. Also, Figure 2 omits the illustration of the raw material container 21, the mechanical seal 73, and the like shown in Figure 1.

[0050] The light source cover 1 is a cover that covers the periphery of the rotating body 20. An opening 4 is provided on the surface of the light source cover 1 in a portion facing the irradiation position I on the right side in Fig. 2, and a portion of the radiation R generated at the irradiation position I passes through the opening 4. In Fig. 2, the path of the radiation R is schematically indicated by an arrow.

[0051] An opening is also provided in the center of the left side surface of the light source cover 1, and the shaft member 72 passes through this opening. By providing the light source cover 1, debris generated at the irradiation position I is prevented from scattering outside the light source cover 1.

[0052] The DMT2 (Debris Mitigation Tool) is a mechanism for capturing debris. Some of the debris generated from the plasma P at the irradiation position I passes through the opening 4 in the light source cover 1 and scatters toward the right. In this example, the DMT2 is placed to the right of the opening 4 to capture such debris.

[0053] In this embodiment, a rotary or fixed foil trap is used as the DMT2. The DMT2 is heated, and the trapped debris melts and becomes liquid, which is then collected. Gas may be introduced to create a pressure difference within the foil trap. The specific type of DMT2 is not limited. The DMT2 corresponds to one embodiment of the debris reduction mechanism according to the present technology.

[0054] The laser port 3 has a generally conical shape and is arranged to penetrate the chamber body 109 and the light source cover 1. The laser port 3 is arranged from the lower right to the upper left in Fig. 2, which corresponds to the upper right to the lower left in Fig. 1. The upper right portion of the chamber body 109 in Fig. 1 is provided with the entrance window 114, the energy beam entrance chamber 104, and the gas injection path 116b, and the laser port 3 is provided together with or in place of these mechanisms.

[0055] The energy beam EB emitted by the beam source 108 passes through the inside of the laser port 3 and reaches the surface (irradiation position I) of the rotating body 20. In other words, the laser port 3 can also be said to be an energy beam introducing member that introduces the energy beam EB onto the surface of the rotating body 20.

[0056] In this embodiment, the arrangement and shape of the DMT 2 and the laser port 3 are adjusted so that the tips of the DMT 2 and the laser port 3 are close to each other.

[0057] [Laser Port] Figure 3 is a schematic diagram showing an example of the configuration of the laser port 3. Figure 3 shows a cross section of the central portion of the laser port 3 cut in the XY plane, viewed from above. For the following explanation, a new XYZ coordinate system will be defined as shown in Figure 3. That is, in reality, the right side of Figure 2 (the positive side of the Y axis) corresponds to the diagonally lower left side of Figure 3, and the bottom side of Figure 2 (the positive side of the X axis) corresponds to the diagonally upper left side of Figure 3, but for convenience, a different coordinate system will be defined.

[0058] The laser port 3 has a housing 7, two windows 8 (8a, 8b), and two pressure holders 9 (9a, 9b). The housing 7 is a roughly conical member, with its apex pointing to the right in FIG. 3. A side portion 11 of the housing 7 has a cylindrical conical shape. The portion corresponding to the bottom of the housing 7 (left side) has a circular opening 10a covering almost the entire surface. The portion corresponding to the apex (right side) has a smaller-diameter opening 10b.

[0059] The specific shape of the housing 7 is not limited and may be changed as appropriate within the scope of feasibility of the present technology. For example, the housing 7 may have a cylindrical shape, with the entire left side being a circular opening 10a, and the right side being configured with a small opening 10b through which the energy beam EB can pass. The housing 7 corresponds to one embodiment of a housing portion related to the present technology.

[0060] The window 8a is a disk-shaped member that has the same shape as the opening 10a of the housing 7. The window 8a is disposed by being fitted into the opening 10a. That is, the window 8a is provided so as to close the opening 10a so that no gap is formed between the window 8a and the opening 10a. Hereinafter, the space surrounded by the side portion 11 and the window 8a will be referred to as the internal space S. The window 8a is made of a material that allows the energy beam EB to pass through. The window 8a corresponds to an embodiment of a first window member according to the present technology.

[0061] A gas introduction pipe 12 is connected near the opening 10a of the side portion 11. The gas introduction pipe 12 is a pipe that communicates with the internal space S, and can also be considered a hole formed in the side portion 11. A mechanism for introducing gas (not shown) is connected to the end of the gas introduction pipe 12 that is not on the internal space S side. When this mechanism is operated, gas flows into the internal space S via the gas introduction pipe 12.

[0062] In this example, four gas introduction pipes 12a to 12d are connected at equal intervals. Two of these, gas introduction pipes 12a and 12b, are shown in FIG. 3. In addition, gas introduction pipes 12c and 12d are also provided, but these are not shown in FIG. 3 because it is a cross-sectional view. Each gas introduction pipe 12 is connected perpendicularly to the side portion 11. However, this configuration is merely an example, and the specific number of gas introduction pipes 12 is not limited, and the connection position and direction may also be arbitrary. The gas introduction pipe 12 corresponds to one embodiment of a gas introduction section according to the present technology.

[0063] Fig. 4 is a schematic diagram showing an example of the configuration of the pressure holder 9a. The pressure holder 9a is a member having a circular ring shape as a whole, and is arranged in the internal space S parallel to the YZ plane as shown in Fig. 3. Note that, since Fig. 3 shows the pressure holder 9a in a schematic manner, the opening inside the ring shape is not shown. The pressure holder 9a has a ring portion 15 and a side portion 16.

[0064] The ring portion 15 is a ring-shaped flat plate. Therefore, the ring portion 15 has a circular opening 19 on the inside. The ring portion 15 also has four screw holes 17 and four gas introduction holes 18 on its surface. In Figure 4, only one screw hole 17 and one gas introduction hole 18 are represented by reference numerals.

[0065] The screw holes 17 are holes for screws to pass through. There are four screw holes 17 in total, one each at the 0 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions of the ring portion 15. The gas introducing holes 18 are holes shaped to fit the ring portion 15, and there are four gas introducing holes 18 in total, one each extending between 0 o'clock and 3 o'clock, 3 o'clock and 6 o'clock, 6 o'clock and 9 o'clock, and 9 o'clock and 12 o'clock of the ring portion 15.

[0066] The side portion 16 is a cylindrical flat plate having a predetermined thickness. The pressure holder 9a does not have a surface on the side facing the ring portion 15 across the side portion 16. The pressure holder 9a is oriented so that the ring portion 15 is on the left side and the side portion 16 is on the right side in Figure 3. Hereinafter, the inner diameter of the ring portion 15 (the diameter of the opening 19) may be referred to as the inner diameter of the pressure holder 9a, and the outer diameter of the ring portion 15 (the diameter of the side portion 16) may be referred to as the outer diameter of the pressure holder 9a.

[0067] The pressure holder 9 a is made of, for example, a rigid material. Furthermore, the material and shape of the pressure holder 9 a and the arrangement and shape of the screw holes 17 and the gas introduction holes 18 are not limited, and any configuration may be adopted within the scope of feasibility of the present technology. The pressure holder 9 a corresponds to an embodiment of a first jig according to the present technology.

[0068] The window 8b is a disk-shaped member configured to allow the energy beam EB to pass through. The window 8b is disposed in the internal space S so as to abut against the back surface of the ring portion 15 of the pressure holder 9a (the surface on the side where the side portion 16 is present). In other words, the pressure holder 9a is positioned on the side of the opening 10a on the left side of the housing 7 with respect to the window 8b. The window 8b is also disposed so that its center coincides with the center of the ring portion 15.

[0069] Here, the diameter of the window 8b is set to be larger than the inner diameter of the pressure holder 9a but not to reach the screw hole 17 or the gas introduction hole 18. In other words, the diameter of the window 8b is smaller than the diameter of the side portion 16 (the outer diameter of the pressure holder 9a), and therefore the window 8b can abut against the back surface of the ring portion 15 without getting caught on the side portion 16. Furthermore, when the window 8b abuts against the ring portion 15, the window 8b blocks the entire opening 19 of the ring portion 15, but does not block the screw hole 17 or the gas introduction hole 18. The window 8b corresponds to an embodiment of a second window member according to the present technology.

[0070] The pressure holder 9b is a conical cylindrical member. The shape of the outer surface of the pressure holder 9b is generally the same as the shape of the inner surface of the side portion 11 of the housing 7 near the opening 10b, and the pressure holder 9b is fixed so as to abut against this portion of the side portion 11. There are no particular limitations on the method for fixing the pressure holder 9b to the side portion 11. Alternatively, the pressure holder 9b and the side portion 11 may be formed integrally.

[0071] The thickness of the pressure holder 9b is greatest on the left side and gradually decreases toward the right side (closer to the opening 10). The space inside the pressure holder 9b also has a generally conical shape. The pressure holder 9b has a bottom surface 23 that is ring-shaped when viewed from the left side of FIG. 3. A plurality of protrusions 24 are formed inside the bottom surface 23. The protrusions 24 are formed discretely, and two of them, protrusions 24a and 24b, are shown in the cross-sectional view of FIG. 3, but other protrusions 24 (not shown) may also be formed, and the number and specific arrangement thereof are not limited.

[0072] Furthermore, the specific shape of the pressure holder 9b is not limited, and any shape may be adopted within the scope of feasibility of the present technology. The pressure holder 9b corresponds to an embodiment of a second jig according to the present technology. The pressure holders 9a and 9b correspond to an embodiment of a jig according to the present technology.

[0073] Each of the protrusions 24 abuts against the right surface of the window 8b. That is, the window 8b has a diameter large enough to abut against the protrusions 24. In this state, the window 8b is sandwiched between the pressure plates 9a and 9b, as shown in Figure 3. It can also be said that the pressure plate 9b is located on the right-hand opening 10b side with respect to the window 8b.

[0074] Furthermore, the pressure holder 9 a is fixed to the housing 7. Specifically, a plurality of screws are passed through the respective screw holes 17 of the pressure holder 9 a and fitted into the side portions 11 of the housing 7, thereby screwing the pressure holder 9 a to the side portions 11.

[0075] As a result, the window 8b is fixed to the pressure holders 9a and 9b. Movement of the window 8b to the left is restricted by the pressure holder 9a, movement to the right is restricted by the pressure holder 9b, and movement in the up-down and back-and-forth directions is restricted by the static frictional forces of the pressure holders 9a and 9b.

[0076] The pressure stopper 9a may be fixed to the side portion 11 by a method other than screw fastening. For example, a snap ring or the like may be used for fixing. Any other method may be used for fixing.

[0077] The window 8b (and the pressure pad 9a) divides the internal space S into two spaces. Hereinafter, of the internal space S, the space on the left opening 10a side with respect to the window 8b will be referred to as internal space S1, and the space on the right opening 10b side will be referred to as internal space S2. The internal space S1 corresponds to an embodiment of a first space according to the present technology. The internal space S2 corresponds to an embodiment of a second space according to the present technology.

[0078] [Action at Laser Port] The progression of the energy beam EB will now be described. The energy beam EB enters the opening 10a from the left side, as shown by the arrow in Fig. 3. Although the opening 10a is closed by the window 8a, the window 8a is configured to allow the energy beam EB to pass therethrough, and therefore the energy beam EB passes through the window 8a and enters the internal space S1. In other words, the opening 10a functions as an entrance hole for the energy beam EB into the internal space S1.

[0079] In this embodiment, the energy beam EB is emitted as converging light from the beam source 108. For example, an optical system is provided in the beam source 108 to converge the energy beam EB. Therefore, although the energy beam EB is incident on the entire surface of the opening 10a, it basically does not reflect on the inner surface of the side portion 11 and proceeds toward the opening 10b while converging.

[0080] The energy beam EB passes through the internal space S1 and the opening 19 of the pressure holder 9a. Next, the energy beam EB reaches the window 8b, which is configured to allow the energy beam EB to pass through, and so the energy beam EB passes through the window 8b. The energy beam EB then passes through the internal space S2 and is emitted from the opening 10b. That is, the opening 10b functions as an emission hole for the energy beam EB.

[0081] Next, the operation of the gas introduction pipe 12 will be described. When gas is introduced into the internal space S1 through the gas introduction pipe 12, the internal space S1 is filled with gas, and the pressure in the internal space S1 increases. In Fig. 3, the flow of gas occurring in the internal space S1 is schematically shown by dashed arrows, but such a gas flow does not necessarily occur.

[0082] The left side of the internal space S1 is closed by the window 8a, so gas does not leak out to the left of the window 8a. On the other hand, the right side of the internal space S1 has the pressure holder 9a, the window 8b, and the pressure holder 9b, but the pressure holder 9a has a gas introducing hole 18, and there is a gap between the window 8b and the side portion 11. In addition, because the protrusions 24 are formed discretely, there is also a gap between the window 8b and the pressure holder 9b.

[0083] Therefore, gas present in the internal space S1 flows into the internal space S2 through these paths. These paths are schematically shown by dashed arrows in Figure 3. It can be said that the gas introducing hole 18 and the gap between the window 8b and the pressure holder 9b conduct the gas from the internal space S1 to the internal space S2.

[0084] The inflow of gas causes the pressure in the internal space S2 to rise. However, because gas can only flow into the internal space S2 through this path, the increase in pressure in the internal space S2 is slower than the increase in pressure in the internal space S1. Therefore, the pressure outside the housing 7 is lowest, and the pressure increases in the order of the outside of the housing 7, the internal space S2, and the internal space S1.

[0085] [Heating Mechanism] In this technology, a heating mechanism is provided that heats the vicinity of the opening 10b of the housing 7. In particular, in this embodiment, the DMT 2 shown in Fig. 2 corresponds to the heating mechanism. The DMT 2 is heated to melt the trapped debris, and is at a temperature equal to or higher than the melting point of the plasma raw material 101. Furthermore, the DMT 2 is provided in the vicinity of the opening 10b as shown in Fig. 2.

[0086] Therefore, heat from the DMT 2 is transferred to the vicinity of the opening 10b, and the vicinity of the opening 10b is constantly heated. The type of heating mechanism is not limited, and a heating mechanism separate from the DMT 2 may be separately configured near the opening 10b to directly or indirectly heat the vicinity of the opening 10b. In this case, the DMT 2 may be provided at a position away from the opening 10b.

[0087] As described above, in the light source device 100 according to this embodiment, the energy beam EB passes through the laser port 3 in the order of window 8a, window 8b, and opening 10b. The window 8a closes opening 10a, and window 8b is fixed to pressure holders 9a and 9b that are fixed to the housing 7. Gas is introduced into the internal space S1, which is the space on the opening 10a side, and gas introduction holes 18 and the like are provided in the pressure holders 9a and 9b. This allows the energy beam EB to be stably introduced to the light-emitting point without being hindered in its travel.

[0088] In LPP-type EUV light sources, the technology for introducing laser light to the light emission point is extremely important. Moreover, since EUV light sources are always required to be compact, it is necessary to make effective use of limited space.

[0089] Because it is necessary to maintain a vacuum at the emission point, the emission point and the laser source are separated by a window that transmits laser light. However, debris is generated at the emission point, which contaminates the window and obstructs the propagation of the laser light. Furthermore, debris adhering to the window absorbs the laser light, which generates heat, creating a thermal lens effect on the window and potentially adversely affecting the direction of propagation and beam shape of the laser light.

[0090] In addition, heat is generated at the light-emitting point, which heats the center of the window locally, causing deformation due to thermal expansion, leading to distortion and breakage. Because the window separates two spaces with a large air pressure difference, if the window breaks, large fragments may fly off and damage other mechanisms. Even if the window does not break, the heat will cause a thermal lens effect on the window.

[0091] One way to reduce the impact of debris and heat on the window is to install a rotating window between the window and the light-emitting point, but this method requires a large amount of space, which is contrary to the goal of making the light source compact.

[0092] In this technology, two windows 8a and 8b are provided between the beam source 108 and the irradiation position I. Therefore, debris generated at the irradiation position I is blocked by the window 8b. This makes it possible to significantly reduce the amount of debris adhering to the window 8a. Furthermore, gas is introduced into the internal space S1, which also causes gas to flow into the internal space S2, making the pressure in the internal space S2 higher than that outside the laser port 3. This makes it difficult for debris to enter the internal space S2, and even prevents debris from adhering to the window 8b.

[0093] Furthermore, the presence of the window 8b between the irradiation position I and the window 8a suppresses absorption of radiation by the window 8a at the irradiation position I. In addition, collision of ions generated at the irradiation position I with the window 8a is suppressed. This suppresses cracking or deterioration of the window 8a, or the occurrence of a thermal lens effect on the window 8a.

[0094] Since the window 8b separates the internal spaces S1 and S2, which have a relatively small air pressure difference, even if the window 8b breaks, fragments will not fly off and basically only a crack will form. Even if fragments fly off, the introduction of gas makes the internal space S1 more pressurized than the internal space S2, so the fragments are less likely to head toward the window 8a.

[0095] Furthermore, the window 8b is cooled by the gas flowing into the internal space S1, and the thermal lens effect at the window 8b is reduced.

[0096] Furthermore, debris may adhere to the vicinity of the opening 10b and grow into a stalagmite shape, blocking the laser light. In this technology, the vicinity of the opening 10b is heated by the heating mechanism, so debris that reaches the vicinity of the opening 10b does not solidify. This prevents debris from adhering to the vicinity of the opening 10b. Furthermore, because the DMT2 is used as the heating mechanism, there is no need to provide a separate heating mechanism, making it possible to miniaturize the light source device 100.

[0097] As a result, the number of maintenance times for the laser port 3 is reduced, the life of the laser port 3 is extended, and the energy beam EB can be stably introduced to the light-emitting point.

[0098] Furthermore, in this technology, the window 8b is fixed by being sandwiched between the two clamps 9a and 9b, which makes it possible to stably fix the window 8b.

[0099] The pressure holder 9a has a ring shape, the window 8b has a disk shape, and the diameter of the window 8b is larger than the inner diameter of the pressure holder 9a and smaller than the outer diameter, which makes it possible to stably fix the window 8b while ensuring the path of travel of the energy beam EB and the path of introduction of gas into the internal space S2.

[0100] The gas is introduced through a hole formed in the side portion 11 of the housing 7. This allows the gas to flow stably into the internal space S1.

[0101] Second Embodiment A more detailed embodiment of the light source device 100 according to the present technology will be described as a second embodiment. In the following description, the description of the same parts as those in the configuration and operation of the light source device 100 described in the above embodiment will be omitted or simplified.

[0102] [Debris Guiding Means] Figure 5 is a schematic diagram showing an example of debris guiding means. Figure 5 is a cross-sectional view of the laser port 3 as viewed from the negative side of the Y axis. Note that Figure 3 is a view of the laser port 3 as viewed from the positive side of the Z axis, and therefore Figures 3 and 5 are oriented differently. For this reason, Figure 5 shows gas introduction pipes 12c and 12d, which are not shown in Figure 3.

[0103] In this example, the side portion 11 near the opening 10b is open downward, forming a space. Hereinafter, this space will be referred to as an internal space S3. In FIG. 5, the outline of the portion corresponding to the internal space S2 in FIG. 3 and the outline of the internal space S3 are each schematically shown by dashed frames. Since the internal space S3 is separated from the window 8b, it can be said that the internal space S3 is a space configured at a different position from the window 8b. The internal space S3 corresponds to one embodiment of a buffer space according to the present technology.

[0104] An exhaust device (not shown) is connected to the lower side of the internal space S3, and the internal space S3 is exhausted by the exhaust device.

[0105] As a result, the pressure in the internal space S3 becomes lower than that in the internal space S2, and debris that enters the internal space S2 from the opening 10b is guided to the internal space S3 on the lower pressure side (the path indicated by the solid arrow). In other words, the debris is guided to a position other than the window 8b. This makes it difficult for debris to adhere to the window 8b, making it possible to suppress contamination of the window 8b.

[0106] In this example, an internal space S3 is provided and exhaust is performed, but only one of these may be performed. That is, a certain effect can be achieved even if the internal space S3 is simply provided without exhausting, and conversely, an effect can also be achieved when the internal space S2 is evacuated without providing the internal space S3 by simply opening the lower side of the side portion 11. Therefore, the means for providing the internal space S3 and the means for evacuating the internal space S2 or S3 each function as debris guiding means.

[0107] In this example, the internal space S3 is provided on the vertically lower side (negative side of the Z axis), but the internal space S3 may be provided in another direction. On the other hand, by providing the internal space S3 on the vertically lower side as in this example, it becomes possible to efficiently guide debris by the action of gravity. Furthermore, since the DMT 2 and the like are often adjacent to the laser port 3 in the horizontal direction, it becomes possible to avoid such constraints.

[0108] In this example, gas does not flow in from the lower side of the pressure holder 9a and the window 8b, as shown in Figure 5. Specifically, the pressure holders 9a and 9b are appropriately designed to prevent gas from flowing in. This allows gas to flow in only from the upper side, making it possible to increase the pressure in the internal space S2 to a higher level than in the internal space S3.

[0109] 6 is a schematic diagram showing an example of the debris guiding means. In this example, a gas nozzle 27 is provided near the opening 10b. The gas nozzle 27 faces diagonally downward, and gas is sprayed diagonally downward into the internal space S3.

[0110] As a result, debris that has entered through the opening 10b is carried by the gas flow toward the internal space S3, and is less likely to travel toward the internal space S2. This makes it difficult for debris to adhere to the window 8b, making it possible to suppress contamination of the window 8b.

[0111] That is, the means for blowing gas toward the internal space S3 from the outside of the laser port 3 functions as debris guiding means. In this example, the internal space S3 is evacuated as in the example of Fig. 5, but it is also possible to only blow gas without evacuating it.

[0112] In this example, the internal space S3 tapers downward in the vertical direction. This makes it possible to strengthen the exhaust force. On the other hand, if the cylindrical shape of Figure 5 is used, the internal space S3 becomes wider, making it possible to alleviate the increase in pressure in the internal space S3. Either shape may be adopted in the design.

[0113] In addition, there are no specific limitations on the type of debris guiding means that guides debris to a position other than the window 8b, and any arbitrary means may be used.

[0114] Other Embodiments The present technology is not limited to the above-described embodiments, and various other embodiments can be realized.

[0115] [Jig Variations] Fig. 7 is a schematic diagram showing a jig variation example. In this example, the window 8b is fixed by a holder 30 instead of the pressure pads 9a and 9b. Fig. 7 shows a cross-sectional view of the window 8b and the holder 30. The holder 30 has a ring shape that is thicker than the window 8b and has the same inner diameter as the window 8b. The holder 30 corresponds to one embodiment of the jig related to the present technology.

[0116] Furthermore, a plurality of stoppers 31 are provided that abut against both the outer periphery of the window 8b and the holder 30. In Fig. 7, a reference numeral is given to one of the plurality of stoppers 31 as a representative. A screw is connected to the surface of the stopper 31 that abuts against the holder 30, and the stopper 31 is fixed to the holder 30 by the screw.

[0117] The holder 30 is also formed with gas introduction holes 32. The number and arrangement of the gas introduction holes 32 are not limited, but in this example, only some of the gas introduction holes 32a and 32b are shown. In the example on the left, the gas introduction holes 32 extend in the thickness direction of the holder 30. In the example on the right, the gas introduction holes 32 are L-shaped and face toward the window 8b (inside).

[0118] In this way, the window 8b is stably fixed by sandwiching it between the holder 30 and the stopper 31. Alternatively, the window 8b and the stopper 31 may be fixed by brazing them together. This further stably fixes the window 8b. It also improves thermal conductivity, suppressing a temperature rise in the window 8b.

[0119] 8 is a schematic diagram showing a variation of the gas introducing holes 18. The number and arrangement of the gas introducing holes 18 in the pressure holder 9a can be varied as shown in this example.

[0120] In the upper example, a total of four gas introduction holes 18 are provided, one each at the 0 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions on the outer periphery. In the lower example, gas introduction holes 18 are provided in both the upper and lower halves, extending along the outer periphery, excluding the 3 o'clock and 9 o'clock positions.

[0121] Any such variations can be adopted for the configuration of the gas introducing hole 18 in accordance with the arrangement of other components, etc. Furthermore, such variations may also be adopted when the holder 30 of FIG.

[0122] 3 extends to the position of the opening 10b, the pressure holder 9b does not have to extend to the position of the opening 10b as long as the pressure holder 9b can be fixed to the side portion 11. In addition, the configuration of the jig is not limited to the pressure holders 9a and 9b and the holder 30, and may be any configuration.

[0123] 3, at least the right side of the window 8b (the side facing the opening 10b) does not need to have an anti-reflection coating (AR coating). If the right side is AR coated, the AR coating may deteriorate, resulting in a thermal lens effect. Therefore, by not coating the right side, it is possible to prevent such a problem.

[0124] On the other hand, the left surface may or may not be AR coated. By applying an AR coating to the left surface, it becomes possible to prevent reflection of the energy beam EB.

[0125] The window 8b is made of a material containing at least one of calcium fluoride and magnesium fluoride, for example, which makes it possible to reduce the absorption of ultraviolet rays by the window 8b.

[0126] The window 8b may be made of at least one of a low-expansion material and glass. These materials absorb ultraviolet rays but have relatively high infrared transmittance, which is useful when the thermal expansion of the window 8b is small.

[0127] The window 8b may be cooled by water cooling, or the window 8a may be cooled by some means, thereby cooling the window 8b by heat conduction.

[0128] 3, the window 8b is fixed at a position approximately in the center inside the laser port 3, but the window 8b may be fixed at a position closer to the window 8a. This separates the irradiation position I (heat source) from the window 8b, making it possible to suppress the influence of heat on the window 8b.

[0129] Furthermore, the specific configuration of the windows 8a and 8b is not limited, and any configuration that allows the energy beam EB to pass through may be used.

[0130] [Variations of Other Components] In Fig. 3, an O-ring may be inserted between the protrusion 24 of the pressure holder 9b and the window 8b, or instead of the protrusion 24. This allows the window 8b to be fixed more stably. In this case, a hole may be formed in the O-ring as necessary to ensure a gas conduction path. In the example of Fig. 7, an O-ring may be inserted between the window 8b and the stopper 31. Alternatively, a Teflon (registered trademark) ring or the like may be used.

[0131] In the example of Figure 3, the laser port 3 has a conical shape. This makes it easier for a pressure difference to occur between the internal spaces S1 and S2. It is also possible to configure the opening 10a to have a diameter of approximately several millimeters, and the opening 10b to have a diameter of approximately 50 µm. However, the laser port 3 may have a shape other than a cone, and the diameters of the openings 10a and 10b are not limited.

[0132] [Type of Plasma Raw Material] There are no specific limitations on the type of plasma raw material 101. For example, not only a completely liquid plasma raw material 101, but also a plasma raw material 101 in a liquid state where a solid is in the process of being melted may be used.

[0133] [Application to Other Devices] In this example, the case where the present technology is applied to an LPP light source device has been described, but the present technology is not limited to this, and may also be applied to a DPP type or LDP type light source device.

[0134] It is also possible to combine at least two of the above-described characteristic features of the present technology. Furthermore, the various effects described above are merely examples and are not limiting, and other effects may be achieved.

[0135] EB...energy beam S1 to S3...internal space 2...DMT 3...laser port 7...casing 8a, 8b...window 9a, 9b...holding plate 10a, 10b...opening 11...side portion 12...gas introduction pipe 18, 32...gas introduction hole 27...gas nozzle 30...holder 100...light source device 101...plasma raw material 108...beam source

Claims

1. A light source device that converts a liquid raw material into plasma by irradiating it with an energy beam to extract radiation, comprising: a housing having an entrance hole and an exit hole for the energy beam and an internal space through which the energy beam passes; a first window member through which the energy beam can pass and arranged to close the entrance hole; a jig fixed to the housing and located in the internal space; a second window member through which the energy beam can pass and fixed to the jig and located in the internal space; and when the space within the internal space on the entrance hole side relative to the second window member is defined as a first space and the space on the exit hole side is defined as a second space, a gas introduction part that introduces gas into the first space, and the jig is equipped with an energy beam introduction member having a gas introduction hole that conducts the gas from the first space to the second space.

2. A light source device according to claim 1, further comprising a heating mechanism for heating the vicinity of said emission hole of said housing portion.

3. A light source device according to claim 2, wherein the heating mechanism is a debris reduction mechanism that captures debris generated from the plasma.

4. A light source device according to claim 1 or 2, wherein the jig comprises a first jig on the entrance hole side and a second jig on the exit hole side, with the second window member as a reference, and the second window member is fixed by being sandwiched between the first jig and the second jig.

5. A light source device according to claim 4, wherein the first jig has a ring shape, and the second window member has a disk shape, the diameter of which is larger than the inner diameter of the first jig and smaller than the outer diameter.

6. A light source device according to claim 1 or 2, wherein at least the surface of said second window member on the side of said emission hole does not have an anti-reflection film.

7. A light source device according to claim 1 or 2, wherein the second window member is made of a material containing at least one of calcium fluoride and magnesium fluoride.

8. A light source device according to claim 1 or 2, wherein the second window member is made of at least one of a material with a low expansion coefficient and glass.

9. A light source device according to claim 1 or 2, wherein the gas inlet is a hole formed in the housing.

10. A light source device according to claim 1 or 2, wherein the energy beam introduction member has a debris guiding means for guiding debris generated from the plasma and entering the internal space through the exit hole to a position different from the second window member.

11. A light source device according to claim 10, wherein the debris guiding means is a means for guiding the debris to a buffer space, which is a space configured at a position different from that of the second window member.

12. A light source device according to claim 10, wherein the debris guiding means is a means for guiding the debris by evacuating the internal space.

13. A light source device according to claim 10, wherein the debris guiding means is a means for guiding the debris by blowing gas from the outside of the energy beam introducing member toward the internal space.

14. An energy beam introducing member used in a light source device that converts a liquid raw material into plasma by irradiating it with an energy beam to extract radiation, comprising: a housing having an entrance hole and an exit hole for the energy beam and an internal space through which the energy beam passes; a first window member through which the energy beam can pass and arranged to close the entrance hole; a jig fixed to the housing and located in the internal space; a second window member through which the energy beam can pass and fixed to the jig and located in the internal space; and when the space within the internal space on the entrance hole side relative to the second window member is defined as a first space and the space on the exit hole side is defined as a second space, a gas introducing portion for introducing gas into the first space, and the jig has a gas introducing hole for conducting the gas from the first space to the second space.

Images