Light source device and radiation extraction method

Abstract

Provided are a light source device and a radiation extraction method which make it possible to efficiently remove debris.　In the present invention, a raw material supply part supplies a raw material to an energy irradiation position. An energy source injects energy into the energy irradiation position to generate plasma. A port has a guide tube and is disposed such that radiation or energy passes through an internal space. The area of a downstream side opening thereof is larger than the area of a light emission side opening thereof. A gas introduction part is at a position that is closer to the energy irradiation position than to the downstream side opening. When the minimum value of the cross sectional area of the guide tube and the internal space in a planar surface that is perpendicular to the optical axis of the radiation or the optical axis of the energy is defined as S (mm2), the distance between the energy irradiation position and a cross section which has the minimum cross sectional area is defined as X (mm), [Mathematical formula 1] is satisfied, and the distance between the energy irradiation position and the light emission side opening is defined as d (mm), [Mathematical formula 2] is satisfied.

Description

Light source device and radiation extraction method

[0001] The present invention relates to a light source device that generates radiation such as X-rays and extreme ultraviolet light, and a method for extracting radiation.

[0002] Extreme ultraviolet (EUV) light, a type of X-ray, has recently been used as exposure light. The substrate for an EUV lithography mask is constructed by patterning a material that absorbs EUV lithography radiation onto a multilayer film (for example, molybdenum and silicon) that reflects EUV light.

[0003] The size of unacceptable defects in EUV masks has become significantly smaller, making them difficult to detect. Therefore, EUV masks are now inspected using a method called actinic inspection, which uses radiation at wavelengths that match the working wavelengths of lithography.

[0004] Generally, EUV light sources include DPP (Discharge Produced Plasma) light sources, LDP (Laser Assisted Discharge Produced Plasma) light sources, and LPP (Laser Produced Plasma) light sources.

[0005] A DPP (Dynamic Pulsed Power) light source device utilizes extreme ultraviolet light emitted from a high-density, high-temperature plasma generated by a discharge, which is created by applying a high voltage between electrodes supplied with gaseous plasma material (discharge gas) containing EUV emitting species.

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

[0007] LPP (Low-Pressure Pulsed Plasma) light sources generate high-temperature plasma by exciting EUV (Extremely Ultraviolet) radiation species with a laser beam or the like. One known type of light source uses a laser beam focused onto droplets of high-temperature plasma raw material ejected in the form of tiny liquid droplets to excite the target material and generate plasma.

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

[0009] This method is equivalent to the so-called LPP method, but it supplies liquid plasma material to the energy beam irradiation area using the centrifugal force of a rotating body, eliminating the need to supply liquid plasma material as droplets. Therefore, compared to methods that focus a laser beam onto droplets, it is possible to obtain high-brightness radiation with a relatively simple configuration.

[0010] Japanese Patent Publication No. 2014-216286

[0011] In light source devices such as those described in Patent Document 1, there is a need for technology that can efficiently remove debris generated by irradiation with an energy beam.

[0012] In view of the above circumstances, the object of the present invention is to provide a light source device and a radiation extraction method that enable the efficient removal of debris.

[0013] To achieve the above objective, a light source device according to one embodiment of this technology is a light source device that generates radiation by plasmaizing a raw material by injecting energy, and comprises a chamber, a raw material supply unit, an energy source, a radiation extraction unit, and a gas introduction unit. The raw material supply unit is housed in the chamber and supplies the raw material to the energy irradiation position. The energy source injects the energy to the energy irradiation position to generate plasma. The port has a conduit and is arranged so that the radiation or energy passes through the internal space surrounded by the conduit, and in the arrangement, when the opening closer to the energy irradiation position is designated as the emission-side opening and the opening further away is designated as the downstream-side opening, the area of ​​the downstream-side opening is larger than the area of ​​the emission-side opening. The gas introduction unit is located closer to the energy irradiation position than the downstream-side opening. The minimum value of the cross-sectional area of ​​the conduit and the internal space in a plane perpendicular to the optical axis of the radiation or the optical axis of the energy is S (mm ２ ) and the distance between the energy irradiation position and the cross-section with the minimum cross-sectional area is X (mm). Assuming that the distance between the energy irradiation position and the light-emitting aperture is d (mm), That is the case.

[0014] In this light source device, a radiation extraction section is positioned where the area of ​​the downstream aperture is larger than the area of ​​the emission-side aperture, and a gas introduction section is configured closer to the energy irradiation position than the downstream aperture. Furthermore, the minimum cross-sectional area of ​​the radiation extraction section, the distance between the energy irradiation position and the cross-section with the minimum cross-sectional area, and the distance between the energy irradiation position and the emission-side aperture satisfy a predetermined relationship. This makes it possible to efficiently remove debris.

[0015] The port may be arranged so that the radiation passes through the internal space surrounded by the conduit. In this case, the S (mm ２ ) may be the minimum value of the cross-sectional area of ​​the conduit and the internal space in a plane perpendicular to the optical axis of the radiation.

[0016] The port may be arranged so that the energy passes through the internal space surrounded by the conduit. In this case, the S(mm ２ ) may be the minimum value of the cross-sectional area of ​​the conduit and the internal space by a plane perpendicular to the optical axis of the energy.

[0017] The light source device may further include a debris reduction device for capturing debris generated at the energy irradiation position.

[0018] In the aforementioned light source device, the angle may be 5° ≤ θ ≤ 20°.

[0019] The conduit may have the shape of a truncated cone.

[0020] The conduit may have two opposing substantially fan-shaped surfaces and two opposing rectangular surfaces.

[0021] The gas introduction section may be an opening formed in the conduit.

[0022] The gas introduction section may be configured in the space between the energy irradiation position and the light-emitting side opening.

[0023] The raw material supply unit may have a housing that surrounds the energy irradiation position and forms a plasma generation space.

[0024] The port may be fixed to the housing.

[0025] The light source device may further include a focusing mirror positioned on the optical axis at a location further from the energy irradiation position than the port. In this case, the chamber may have a partition separating the port and the focusing mirror. The port may also be fixed to the partition.

[0026] The minimum cross-sectional area of ​​the internal space only, as defined by the plane, is S (mm²). ２ Even in this case, the condition 5° ≤ θ ≤ 20° may still hold.

[0027] The port may have an adjustment mechanism for adjusting the position of the conduit.

[0028] The light source device may further include a measurement unit that measures the amount of gas introduced by the gas introduction unit.

[0029] A radiation extraction method according to an aspect of the present technology is a light source device that generates radiation by plasmaizing a raw material by injecting energy, including: a chamber; a raw material supply unit that is housed in the chamber and supplies the raw material to an energy irradiation position; an energy source that injects the energy into the energy irradiation position to generate plasma; a port having a conduit and arranged such that the radiation or the energy passes through an internal space surrounded by the conduit, wherein when the opening closer to the energy irradiation position in this arrangement is defined as a light emission side opening and the farther opening is defined as a downstream side opening, the area of the downstream side opening is larger than the area of the light emission side opening; and a gas introduction unit configured at a position closer to the energy irradiation position than the downstream side opening. In the light source device, the minimum value of the cross-sectional area of the conduit and the internal space by a plane perpendicular to the optical axis of the radiation or a plane perpendicular to the optical axis of the energy is defined as S (mm ２ ), the distance between the energy irradiation position and the cross-section where the cross-sectional area is minimum is defined as X (mm), and when the distance between the energy irradiation position and the light emission side opening is defined as d (mm), including setting it as such.

[0030] According to the present invention, debris can be efficiently removed. Note that the effects described here are not necessarily limited, and any of the effects described in the present disclosure may be applicable.

[0031] It is a schematic diagram showing a configuration example of a light source device according to this embodiment. It is a schematic diagram showing a configuration example of a port. It is a diagram showing an outline of a simulation model. It is a graph showing the relationship between conductance and P×D value. It is a diagram showing the shape and arrangement of ports. It is a graph showing the relationship between d, L, and θ. It is a graph showing the relationship between d and θ. It is a schematic diagram showing a configuration example of a port with a distorted shape. It is a schematic diagram showing a method of fixing a port. It is a schematic diagram showing a method of fixing a port. It is a schematic diagram showing a variation example of the shape of a port. It is a schematic diagram showing a configuration example of an incident unit.

[0032] [Basic Configuration of Light Source Device] FIG. 1 is a schematic diagram showing a configuration example of a light source device 100 according to this embodiment. The light source device 100 is a light source device using the LPP method. That is, the light source device 100 irradiates a plasma raw material 101 with an energy beam EB to excite the plasma raw material 101 to generate a plasma P, and extracts radiation R emitted from the plasma P and uses it as a light source. The radiation R is EUV light, X-rays, or other electromagnetic waves. The energy beam EB corresponds to one embodiment of energy.

[0033] The plasma raw material 101 is a molten metal or alloy, for example, 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 the raw material.

[0034] FIG. 1 is a diagram when viewing a schematic cross-section when the light source device 100 is cut along the horizontal direction at a position at a predetermined height from the installation surface from directly above vertically. In FIG. 1, for parts where it is not necessary to explain the configuration of the cross-section, etc. for easy understanding of the configuration and operation of the light source device 100, the illustration of the cross-section is omitted. Hereinafter, there may be cases where the X direction and the Y direction are described as the horizontal direction and the Z direction as the vertical direction. Of course, the orientation in which the light source device 100 is used is not limited for the application of this technology.

[0035] As shown in Figure 1, the light source device 100 comprises a housing 102, a vacuum chamber 103, an energy beam injection chamber 104, a radiation emission chamber 105, a plasma generation mechanism 106, a control unit 107, and a beam source 108. The vacuum chamber 103 corresponds to one embodiment of the chamber.

[0036] In the example shown in Figure 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 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 to pass through the entrance hole 102b.

[0037] As shown in Figure 1, a beam source 108 that emits an energy beam EB is installed outside the housing 102. The beam source 108 is positioned so that the energy beam EB is incident into the inside of the housing 102 along the incident axis IA. An electron beam or laser light can be used as the energy beam EB. The beam source corresponds to one embodiment of the energy source.

[0038] The light source device 100 is provided with a chamber section C that includes a plurality of chambers. Specifically, the chamber section C includes a vacuum chamber 103, an energy beam injection chamber (hereinafter simply referred to as the injection chamber) 104, and a radiation emission chamber (hereinafter simply referred to as the emission chamber) 105. The vacuum chamber 103 and the injection chamber 104 are connected to each other, and the vacuum chamber 103 and the emission chamber 105 are connected to each other.

[0039] The injection chamber 104 is configured to be located on the injection axis IA of the energy beam EB, and the exit chamber 105 is configured to be located on the exit axis EA of the radiation R. A focusing mirror 112 for guiding the radiation R is placed inside the exit chamber 105. A plasma generation mechanism 106 for generating plasma P is placed inside the vacuum chamber 103.

[0040] A user device, such as a mask inspection device, is connected to the end of the ejection chamber 105 opposite the plasma generation mechanism 106. In the example shown in Figure 1, an application chamber 110 is connected as a chamber that forms part of the user device. The pressure inside the application chamber 110 may be atmospheric pressure. The inside of the application chamber 110 may also be purged by introducing gas (for example, an inert gas) from a gas injection passage as needed, and exhausted by an exhaust means not shown. Between the application chamber 110 and the ejection chamber 105, a filter membrane 111 or an opening is provided to physically separate the region where plasma P is generated from the application chamber 110.

[0041] The chamber body 109 is provided with an entrance window 114. The entrance window 114 is positioned on the entrance axis IA of the energy beam EB, aligned with the entrance hole 102b. An exhaust pump 117 is also connected to the chamber body 109.

[0042] Furthermore, as shown in Figure 1, the exit chamber 105 and the injection chamber 104 are provided with gas injection passages 116a and 116b, respectively, and gas is supplied to the interiors of the exit chamber 105 and the injection chamber 104 from a gas supply device (not shown). The exit chamber 105 is supplied with a gas that has high transmittance to radiation R, such as argon or helium. The injection chamber 104 is supplied with a gas that has high transmittance to energy beam EB, such as argon or helium.

[0043] The plasma generation mechanism 106 is a mechanism that generates plasma P and emits radiation R. The plasma generation mechanism 106 is housed in a vacuum chamber 103. As shown in Figure 1, the plasma generation mechanism 106 includes a rotating body 20.

[0044] An energy beam EB is incident on the rotating body 20. The rotating body 20 is positioned such that the irradiation position I of the energy beam EB is located at the intersection of the incident axis IA and the exit axis EA.

[0045] The plasma generation mechanism 106 corresponds to one embodiment of the raw material supply unit. The irradiation position I corresponds to one embodiment of the energy irradiation position.

[0046] A shaft member 72 is connected to the center of the back surface (the negative side of the Y-axis) of the rotating body 20. The shaft member 72 is positioned to penetrate the chamber body 109 and the housing 102. A motor 71 is positioned outside the housing 102, and the motor 71 is connected to the end of the shaft member 72 that is not connected to the rotating body 20.

[0047] When the motor 71 is driven, the shaft member 72 and the rotating body 20 rotate together. The direction of these rotations is indicated by arrows in Figure 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 shaft member 72 that penetrates the chamber body 109. This ensures smooth rotation while maintaining the airtightness of the vacuum chamber 103.

[0048] Furthermore, the plasma generation mechanism 106 has a raw material container 21. Plasma raw material 101 is stored in the raw material container 21, and the lower side of the rotating body 20 is immersed in the stored plasma raw material 101.

[0049] As the rotating body 20 rotates, the plasma raw material 101 is lifted while adhering to the rotating body 20. As a result, the plasma raw material 101 is always adhering to the surface of the rotating body 20, and the plasma raw material 101 is supplied to the irradiation position I. Furthermore, the energy beam EB is irradiated (energy is injected) onto the adhering plasma raw material 101 by the beam source 108. This generates plasma P at the irradiation position I.

[0050] 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 Figure 1, the control unit 107 is schematically shown as a functional block, but the location and other aspects of the control unit 107 can be designed arbitrarily.

[0051] Furthermore, as shown in Figure 1, in this embodiment, a radiation diagnostic unit 119 is connected to the chamber body 109. The radiation diagnostic unit 119 is positioned where radiation R, which is emitted in a direction different from the radiation emission axis EA, is incident, and measures the state of radiation R emitted from the plasma P.

[0052] Furthermore, in this embodiment, a light extraction unit 22 is positioned between the irradiation position I and the emission chamber 105. In Figure 1, the position where the light extraction unit 22 is positioned is schematically shown by a shaded rectangle.

[0053] [Port Configuration Example] Figure 2 is a schematic diagram showing a configuration example of port 23. Figure 2 schematically illustrates the entire light extraction unit 22. The light extraction unit 22 includes port 23, a focusing mirror 24, and a flow meter 28. Note that the angle of the rotating body 20 and the irradiation position I on the rotating body 20 are different in Figures 1 and 2, but the arrangement of the rotating body 20 and the specific irradiation position I may be arbitrary.

[0054] Port 23 is a mechanism for extracting radiation R and has a conduit 25. In this embodiment, the conduit 25 has a frustoconical shape and has a smaller diameter opening 26a and a larger diameter opening 26b. That is, the area of ​​opening 26b is larger than the area of ​​opening 26a. The shape of the internal space T surrounded by the conduit 25 is also a frustoconical shape, and port 23 is positioned so that radiation R passes through the internal space T.

[0055] In this embodiment, the port 23 is positioned such that the central axis of the frustum of the conduit 25 coincides with the emission axis EA of the radiation R. That is, the conduit 25 faces the irradiation position I, and its central axis is parallel to the Y-axis. In Figure 2, the emission axis EA (which is also the central axis of the conduit 25) is shown as a dashed line. Furthermore, the port 23 is positioned such that the opening 26a is closer to the irradiation position I, and the opening 26b is further away from the irradiation position I. Opening 26a corresponds to one embodiment of the emission-side opening according to this technology. Opening 26b corresponds to one embodiment of the downstream-side opening according to this technology.

[0056] The radiation R is emitted from the irradiation position I in all directions within the hemisphere, but due to the arrangement of the ports 23, some of the radiation R passes through the entire internal space T. In Figure 2, the radiation R passing through the internal space T is illustrated with a shaded area.

[0057] In addition, any other arrangement is possible in which the radiation R passes through the internal space T. For example, the central axis of the conduit 25 may be slightly inclined with respect to the emission axis EA. Furthermore, the conduit 25 may have any cylindrical shape such that the area of ​​the downstream opening is larger than the area of ​​the emission-side opening.

[0058] Furthermore, in this technology, the gas introduction section is configured closer to the irradiation position I than to the opening 26b. In particular, in this embodiment, the gas introduction section is configured as a gas inlet 27 in the conduit 25. Specifically, the gas inlet 27 is configured on the cylindrical side surface of the conduit 25, at a position close to the opening 26a.

[0059] The gas inlet 27 communicates with the internal space T and a gas supply source (not shown). This gas supply source may be the same as the gas supply source for the gas injection passage 116a or 116b in Figure 1. When the gas supply source is driven, gas is introduced into the internal space T through the gas inlet 27. As the gas, for example, argon or other inert gases can be used. Note that multiple gas inlets may be configured.

[0060] The focusing mirror 24 is positioned downstream of the port 23 (on the right side in Figure 2). In Figure 2, the focusing mirror 24 is schematically shown as a rectangular block, but any shape of focusing mirror 24 that can focus the radiation R, such as a convex lens or a nested mirror, may be used. The radiation R refracted by the focusing mirror 24 converges to a point downstream of the focusing mirror 24, as shown in Figure 2, and then diffuses again before entering the discharge chamber 105 in Figure 1.

[0061] The flow meter 28 is a mechanism for measuring the flow rate of gas introduced into the internal space T through the gas inlet 27. The flow meter 28 outputs the gas flow rate in units such as sccm (Standard Cubic Centimeter per Minute). Figure 2 schematically shows the flow meter 28 as a block, but the specific type and arrangement of the flow meter 28 are not limited. The flow meter 28 corresponds to one embodiment of the measuring side part according to this technology.

[0062] [Debris Removal] At irradiation position I, debris is generated simultaneously with the generation of plasma P. Like radiation R, the debris is emitted in all directions of the hemisphere. Of this debris, the debris emitted in the direction of the focusing mirror 24 adversely affects the focusing mirror 24 and other optical components. For example, sputtering, where the reflective surface is scraped by the debris, deposition, where the debris accumulates on the reflective surface, or implantation, where the debris is driven deep into the reflective surface, can occur. These can impair the function of the optical components and reduce the overall performance of the light source device 100. Therefore, some measures are needed to protect the optical components from the debris.

[0063] In this embodiment, a port 23 is provided to capture the debris, and gas is introduced into the internal space T. As a result, the internal space T and the space between the irradiation position I and the opening 26a are filled with gas. When the debris passes through the internal space T, etc., it collides with the gas particles filling the internal space T, etc., and the debris, having lost kinetic energy due to the collision, is removed from the optical path along the gas flow.

[0064] Since debris loses kinetic energy through collisions, the ability to remove debris depends on the length of the space where the gas is introduced in the direction of the exit axis EA, and the density of the gas particles. Here, the density of the gas particles can be considered as the gas pressure. In other words, the larger the P × D value, which is the product of the average value P of the gas pressure along the optical path and the length D of the high-pressure space in the direction of the exit axis EA, the greater the debris removal ability.

[0065] The range of the region where the pressure is locally increased varies depending on the light emission method of the light source. However, in a plasma generation light source such as this method, which forms a layer of molten metal as fuel on a rotating disk, drum, etc. and irradiates the layer of the metal with an energy beam EB, it is possible to make the gas pressure around the light emission part (irradiation position I) relatively high. This method is because, for example, compared with plasma generation using discharge, it is less affected by the increase in pressure around the light emission part.

[0066] Therefore, in this method, it is possible to configure a system that forms a high-pressure region around the light emission part. The formation of such a local high-pressure region can be achieved by devising the shape and arrangement of the port 23.

[0067] Here, in order to increase the average value P of the gas pressure, it is also conceivable to increase the gas introduction amount. However, if the gas flow rate increases, it becomes necessary to increase the size of the exhaust system. Therefore, there is a limit to the gas flow rate, and it is preferably set to 3000 sccm or less, which can be easily handled by a combination of generally commercially available large turbo molecular pumps, etc. That is, when the gas flow rates introduced from a plurality of gas introduction parts are Q １ , Q ２ , Q ３ , ···, the sum ΣQ ｉ of those flow rates should satisfy ΣQ ｉ ≤ 3000 sccm.

[0068] [Simulation] Figure 3 is a diagram showing an outline of a simulation model. The inventor conducted a simulation to obtain a conductance C such that sufficient debris removal performance is realized. Conductance is a value representing the ease of gas flow. The larger C is, the easier the gas flows, and the smaller C is, the more difficult the gas flows.

[0069] Figure 3 shows an experimental port 31 used in the simulation. The port 31 has a cylindrical shape, and gas was introduced (dashed arrow) from a position on its side surface close to the bottom surface on the light emission point side.

[0070] Here, C is defined as the conductance from the gas introduction point to the outlet (right end) of port 31 (solid arrow). The direction of gas outflow is assumed to be towards the outlet of port 31. The purpose of this simulation is to determine the conditions for conductance C, but in the actual light source device 100, the introduced gas particles may move towards both the light emission point and the outlet, and may also be adsorbed onto the inner wall of port 23, etc.

[0071] The flow rate of the gas to be introduced is determined by the above conditions (ΣQ ｉ The value was set to 1200 sccm, which satisfies the condition (≤3000 sccm) and is a value that can actually be used. In addition, the exhaust speed was appropriately set so that the outer space on the outlet side of port 31 becomes 2 Pa.

[0072] Figure 4 is a graph showing the relationship between conductance and the P×D value. The inventor measured the relationship between conductance C and the P×D value under the above conditions. The horizontal axis of the graph represents conductance C, and here its unit is m. ３ The value is set to / sec. The vertical axis shows the P×D value (Pa・cm). Here, the P×D value is the value at a position 10 cm away from the light source towards port 31.

[0073] As shown in Figure 4, a straight line showing the relationship between C and the P×D value was obtained by linearly approximating the three points obtained from the simulation results. Here, paragraph

[0079] of Japanese Patent Application Publication No. 2007-298980 states that a P×D product of 500 mT·cm is a preferred value for reducing debris. Converting this value to the numerical value on the vertical axis of Figure 4, it is 66.7 Pa·cm. Therefore, reading from the graph, the conductance C is 0.07 m ３ The result indicated that it needs to be less than or equal to / sec.

[0074] Figure 5 shows the shape and arrangement of the port 23. The inventor further states that for the port 23 having a frustoconical shape, the conductance C is 0.07 m ３We considered what shape and arrangement of port 23 is necessary to keep the emission level below / sec. In particular, we examined the conditions that must be satisfied for the distance d (mm) between the irradiation position I and the aperture 26a shown in Figure 2, and for the aperture angle θ of port 23 (the inclination of the side relative to the emission axis EA).

[0075] As shown in Figure 5, let L (mm) be the length of the port 23 in the direction of the discharge axis EA. Also, let a (mm) be the value obtained by adding the thickness of the conduit 25 (margin) to the radius of the opening 26b (representative length). Similarly, let b (mm) be the value obtained by adding the thickness of the conduit 25 to the radius of the opening 26a.

[0076] Then, This holds true.

[0077] Furthermore, the conductance C is approximately It can be calculated as follows.

[0078] Substituting equations (3) and (4) into equation (5) yields the relationship between C, d, L, and θ. Furthermore, the above C ≤ 0.07 (m ３ Using the condition ( / sec), a conditional expression that d, L, and θ must satisfy can be obtained. The inventor further substituted several predetermined values ​​for L and calculated what the conditional expression that d and θ must satisfy would look like.

[0079] Figure 6 is a graph showing the relationship between d, L, and θ. The inventor substituted five different values ​​for L—5 mm, 25 mm, 50 mm, 75 mm, and 100 mm—and investigated the relationship between d and θ for each value. The vertical axis of the graph represents d (mm), and the horizontal axis represents θ (°). Furthermore, the graph is illustrated with different line and point types for each value of L.

[0080] For each value of L, the region where d and θ satisfy the condition corresponds to the region to the lower left of the graph. For example, in the case of L = 5 mm, d = 50 mm, and θ = 10°, the point where d = 50 mm and θ = 10° is to the lower left of the graph for L = 5 mm, so the condition is satisfied. That is, C ≤ 0.07 (m ３ This results in a state where the P × D value is 66.7 Pa·cm or higher ( / sec).

[0081] As shown in the graph, it was found that the relationship between d and θ does not change much with the value of L. Therefore, the inventor approximated these multiple graphs and obtained a conditional equation that includes only d and θ.

[0082] Figure 7 is a graph showing the relationship between d and θ. Approximating each graph in Figure 6 yielded the relationship shown in the graph in Figure 7. The equation for the region to the lower left of this graph is: That is the case.

[0083] Furthermore, the following results were obtained from the experiment: (1) In general, it is desirable for the aperture angle θ ≥ 5° in order to obtain sufficient radiation R output. (2) Since the debris removal performance strongly depends on the minimum area of ​​the aperture, higher debris removal performance is achieved when θ ≤ 20°. (3) Regarding d under the condition θ ≤ 10°, it is preferable that d ≤ 100 (cm) because the amount of radiation R taken in increases as you get closer to the plasma P.

[0084] Figure 8 is a schematic diagram showing an example of the configuration of a distorted port 34. The shape of the port can vary depending on its intended use and any additional mechanisms added. Through repeated experiments, the inventors found that even a typical port 34 (not limited to a frustoconical shape) as shown in Figure 8 can achieve debris removal performance if the following conditions are met.

[0085] (Condition) The minimum cross-sectional area of ​​the conduit 35 and the internal space T, measured by a plane perpendicular to the ejection axis EA, is S (mm²). ２ Let X (mm) be the distance between the irradiation position I and the cross-section with the minimum cross-sectional area. Assuming that the distance between the irradiation position I and the aperture 36a on the light-emitting side is d (mm), That is the case.

[0086] The cross-section that minimizes the cross-sectional area S can take any shape, but it could be a polygon such as a triangle or rectangle, a perfect circle, or an ellipse. In particular, in the case of port 23 which has the shape of a frustocone as shown in Figure 5, the cross-section is a perfect circle.

[0087] In Figure 8, the "plane perpendicular to the exit axis EA" is the XZ plane. The position where the cross-sectional area of ​​the conduit 25 and the internal space T is minimized by the XZ plane is the constriction position 37 of the port 34. In this example, the constriction position 37 can also be said to be the part that most restricts the shape of the radiation R. Furthermore, the constriction position 37 can also be said to be the part that defines the shape of the projection of radiation R at the downstream opening 36b.

[0088] Therefore, in this example, the cross-sectional area at the constriction is S, and the distance between this cross-section and the irradiation position I is X. Substituting these values ​​of S and X into equation (1) gives θ, which must satisfy equation (2).

[0089] Furthermore, it has been found that even for such a general port 34, higher debris removal performance can be achieved if the angle is 5° ≤ θ ≤ 20°, similar to (1) and (2) above.

[0090] Furthermore, for port 23, which has a frustoconical shape, the θ obtained by equation (Equation 1) coincides with the true θ shown in Figure 5. This will be explained. First, in Figure 5, the "plane perpendicular to the exit axis EA" is the XZ plane. The position where the cross-sectional area of ​​the conduit 25 and the internal space T is minimized by the XZ plane is the position of the opening 26a. Therefore, S is the sum of the cross-sectional area of ​​the conduit 25 and the cross-sectional area of ​​the internal space T at the position of the opening 26a. Thus, S = πb ２ This is the result.

[0091] Furthermore, since X is the distance between the irradiation position I and the aperture 26a, X = d. Therefore, substituting these values ​​of S and X into the right-hand side of equation (Equation 1), we get θ = tan －１ We obtain (b / d). This value of θ is equal to the true value of θ.

[0092] In the light source device 100 according to this embodiment, a port 23 is provided in which the area of ​​the opening 26b is larger than the area of ​​the opening 26a, and a gas inlet 27 is configured closer to the irradiation position I than to the opening 26b. Furthermore, the minimum value S of the cross-sectional area of ​​the port 23, the distance X between the irradiation position I and the cross-section with the minimum cross-sectional area, and the distance d between the irradiation position I and the opening 26a satisfy a predetermined relational expression. This makes it possible to efficiently remove debris.

[0093] Debris is generated from the plasma P in various forms, such as droplets, clusters, neutral particles, and ions. The generated debris causes damage events such as deposition, sputtering, and implantation to optical components such as the focusing mirror 24 and structures within the vacuum chamber 103. In this embodiment, gas is introduced into the internal space T of the port 23 to remove the debris, creating a localized high-pressure space.

[0094] In this case, the light source device 100 is required to always increase the output of the radiation R. One way to do this is to increase the intensity of the input energy beam EB, but there is a limit to that intensity. Therefore, it is necessary to make the aperture angle of the port 23 from which the radiation R is extracted as large as possible.

[0095] However, increasing the opening angle increases the amount of debris that enters the port 23. Also, the gas conductance increases, reducing the debris removal performance. Therefore, it was necessary to appropriately set the shape and arrangement of the port 23 in order to ensure sufficient debris removal performance while maximizing the output of radiation R.

[0096] In this technology, the shape and arrangement of the port 23 are defined to satisfy predetermined conditions, making it possible to ensure sufficient debris removal performance and radiation output R. In other words, it becomes possible to remove debris efficiently.

[0097] Furthermore, in this technology, the conduit 25 has a frustoconical shape. As a result, the shape of the internal space T is aligned with the radiation R, making it possible to further increase the output of the radiation R.

[0098] Furthermore, in this technology, a gas inlet 27 is configured in the conduit 25 as the gas introduction section. This makes it possible to introduce gas more efficiently into the internal space T and the space between the irradiation position I and the opening 26a.

[0099] Furthermore, in this technology, the gas flow rate is measured by a flow meter 28. This makes it possible to introduce an appropriate amount of gas.

[0100] <Other Embodiments> This technology is not limited to the embodiments described above, and various other embodiments can be realized. In the following description, parts that are similar to the configuration and operation of the light source device 100 described in the above embodiments will be omitted or simplified.

[0101] [Placement on the Incidence Side] An incidence unit 50 having a configuration substantially identical to that of the light extraction unit 22 may be placed on the incidence side of the energy beam EB. In Figure 1, the position where the incidence unit 50 is placed is indicated by a shaded rectangle. When the incidence unit 50 is installed, it is possible to use the incidence chamber 104 in combination as shown in Figure 1, but it is also possible to install only the incidence unit 50 without providing a special compartment such as the incidence chamber 104.

[0102] Figure 11 is a schematic diagram showing an example configuration of the injection unit 50. The injection unit 50 includes a port 51 and a flow meter 52, which have the same configuration as those in the light extraction unit 22. Note that a focusing mirror is not included. Figure 11, like Figure 1, shows each mechanism viewed from the positive side in the Z direction, which is a different viewing direction from Figure 2.

[0103] The internal space T' of the conduit 53 is the space through which the energy beam EB passes. This figure only shows the incident axis IA of the energy beam EB. Also, similar to the light extraction unit 22, the minimum value of the cross-sectional area of ​​the conduit 53 and the internal space T' by a plane perpendicular to the incident axis IA of the energy beam EB is S (mm²). ２ When this is the case, the conditions of equation (2) and 5° ≤ θ ≤ 20° are satisfied. This makes it possible to suppress the amount of debris flying towards the incident side, and a further debris reduction effect is achieved.

[0104] Furthermore, as in this example, by installing a Debris Mitigation Tool (DMT) between the focusing mirror 24 and the plasma P generated by the energy beam EB on the radiation R emission side, it is also possible to guide the radiation R to the focusing mirror 24 while reducing debris. The Debris Mitigation Tool 54 may be any mechanism capable of capturing debris, such as a foil trap. The Debris Mitigation Tool 54 corresponds to one embodiment of the debris reduction device according to this technology.

[0105] In this configuration, it is also possible to install a port 23 instead of the debris reduction tool 54 and configure a light extraction unit 22 similar to that in Figure 2. That is, ports 53 and 23 may be installed on both the inlet and outlet sides. If there are no space limitations from the plasma P to the focusing mirror 24, it is also possible to use the debris reduction tool 54 and port 23 together. In this case, it is preferable to use them together because it is expected that debris can be reduced significantly.

[0106] [Device Configuration, etc.] The light extraction unit 22 may be arranged to communicate with multiple connected chambers. For example, the first to third chambers may be connected by a partition wall, and each partition wall may have an opening for the passage of radiation R. The rotating body 20 and port 23 may be arranged in the first chamber, the focusing mirror 24 may be arranged in the second chamber, and the radiation R may be focused to a single point in the third chamber.

[0107] If the aperture angle of port 23 is increased, or if port 23 is brought closer to the irradiation position I, a portion of port 23 may overlap with the path of the energy beam EB, obstructing the propagation of the energy beam EB. In such cases, an opening may be provided in port 23 to allow the energy beam EB to pass through.

[0108] Even if the shape of the internal space T differs slightly from a precise frustocone due to a protrusion on part of the inside of port 23, the conditional equation can be applied under a shape that ignores the differing part. In other words, in practice, the most important elements of the shape of port 23 are the opening angle θ and the distance d, and the internal structure and fine details of port 23 are relatively insensitive.

[0109] In the example shown in Figure 1, the light extraction unit 22 is positioned on the path of radiation R toward the utilization device, but the light extraction unit 22 may also be positioned on the path toward the radiation diagnostic unit 119, etc. Furthermore, the specific location where the light extraction unit 22 is positioned is not limited.

[0110] A debris removal mechanism may be provided downstream of port 23 (near the opening 26b). Possible debris removal mechanisms include, for example, installing multiple thin plates or a thin film that allows a portion of the radiation R to pass through. In this case, the debris removal mechanism can be said to separate port 23 and a portion of the internal space T, but these can still be considered as a single port 23 when applying the conditions of this technology.

[0111] The focusing mirror 24 may be placed inside the port 23. In this case, only the portion of the port 23 closer to the irradiation position I than the focusing mirror 24 may be considered, and the conditional expression may be applied to that portion.

[0112] [Gas Inlet] The gas inlet may be configured at any position closer to the irradiation position I than the opening 26b. However, it is preferable that the gas pressure distribution be relatively high between the irradiation position I and the port 23 or focusing mirror 24, and low downstream. This is because the larger the high-pressure region, the more radiation R is absorbed by the gas. Therefore, the conductance from the gas inlet to the irradiation position I should be C １ The conductance from the gas introduction section to the focusing mirror 24 is C ２ In that case, C １ ≥ C ２ It is preferable that this be the case.

[0113] A configuration may be adopted in which the tip of the gas nozzle is positioned in the space between the irradiation position I and the opening 26a. In this case, a gas supply source is connected to the other end of the gas nozzle. This makes it possible to further efficiently increase the gas pressure around the irradiation position I. The gas nozzle corresponds to one embodiment of the gas introduction unit according to this technology.

[0114] The specific type of gas introduced through the gas inlet is not limited, and any type of gas can be used as long as it is feasible for this technology. For example, using argon makes it possible to obtain high debris removal performance at a low cost. Hydrogen gas may also be used. In this case, hydrogen combines with tin, which is debris, to produce stannane, and the debris is removed when the stannane vaporizes.

[0115] [Port Fixing Method] Figures 9A and 9B are schematic diagrams showing the method of fixing the port 23. In the example of Figure 9A, the plasma generation mechanism 106 is equipped with a housing 19, and the rotating body 20 is arranged inside the housing 19. The housing 19 typically serves as a cover member that covers the rotating body 20, etc. Although not shown in the figure, the housing 19 is provided with an opening for the energy beam EB to enter and an opening for the radiation R to exit.

[0116] The housing 19 is provided to prevent droplets of the plasma raw material 101 from scattering to the outside due to the generation of plasma P and the movement of the rotating body 20. The space surrounding the irradiation position I enclosed by the housing 19 becomes the plasma generation space where plasma P is generated.

[0117] In this example, the port 23 is fixed by connecting its tip to the housing 19. Alternatively, the port 23 may be fixed to a cover or the like to prevent the plasma material 101 from flowing out.

[0118] In Figure 9B, the vacuum chamber 103 has a partition wall 40 that separates the port 23 from the focusing mirror 24 (not shown), and the port 23 is fixed by connecting its rear end to the partition wall 40. With the configurations in Figures 9A and 9B, a high-pressure space is more easily formed around the irradiation position I, and further improvement in the P×D value can be expected.

[0119] In the configuration shown in Figure 9B, the exhaust system may be provided on the side closer to the irradiation position I than the partition wall 40. The inside of port 23 is under relatively high pressure, and normally the mean free path of the gas is sufficiently smaller than the length of the internal space T of port 23. Therefore, it is presumed that the gas behaves like an intermediate flow inside port 23. Debris that collides with the gas and loses kinetic energy is thought to be discharged along the gas flow.

[0120] At this time, if the debris that has lost its kinetic energy is transported to the focusing mirror 24 side, the debris will adhere to the surface of the focusing mirror 24, causing a decrease in reflectivity, etc. Therefore, it is desirable for the gas to flow toward the irradiation position I. By providing an exhaust system, the gas pressure around the irradiation position I decreases, and if a gas inlet 27 is provided on the side of the port 23, it becomes easier to form a gas flow from the internal space T toward the irradiation position I. The effective exhaust speed of the exhaust system may be adjusted as appropriate according to the configuration of the plasma generation mechanism 106 and the partition wall 40.

[0121] The port 23 may be fixed to the inner wall of the vacuum chamber 103. Specifically, in Figures 9A and 9B, a fixing part, for example, a rod shape, protrudes downward from an inner wall (not shown) located on the upper side of the paper, and the port 23 is fixed by connecting the conduit 25 of the port 23 to this fixing part.

[0122] This achieves the same effects as the configurations in Figures 9A and 9B. In addition, the port 23 becomes less susceptible to the effects of thermal deformation of the plasma generation mechanism 106 and the vacuum chamber 103. That is, it prevents the inability to adequately transmit radiation R due to the port 23 being misaligned from its design position. To further suppress thermal deformation, a cooling mechanism may be provided in the vacuum chamber 103.

[0123] Port 23 may have an adjustment mechanism to adjust the position of the conduit 25. For example, the adjustment mechanism adjusts the position of port 23 in the Z direction in Figure 2. This makes it possible to maintain the radiation R transmission performance by correcting any unintended positional or morphological displacement of port 23 due to thermal deformation or the like.

[0124] The specific configuration of the adjustment mechanism is not limited. In particular, in the configuration in which the aforementioned port 23 is fixed to the inner wall of the vacuum chamber 103, it is possible to easily provide an adjustment mechanism by attaching it to the inner wall. Conversely, the irradiation position I of the energy beam EB may also be adjusted. This method is also useful when an adjustment mechanism cannot be provided.

[0125] [Port Shape] Figure 10 is a schematic diagram showing examples of variations in port shape. Figure 10 illustrates a box-shaped port 43 as viewed from roughly the negative side in the Y direction. Specifically, the conduit 44 of the port 43 has two opposing, roughly fan-shaped surfaces 45a and 45b, and two opposing, rectangular surfaces 46a and 46b.

[0126] Faces 45a and 45b have a shape obtained by removing sector B, which is part of circle B, from sector A, which is part of circle A, when considering circle A and circle B, which has a smaller radius than circle A but the same center. Furthermore, the central angles of sector A and sector B are equal. Faces 45a and 45b are arranged opposite each other, parallel to the XY plane.

[0127] Both surfaces 46a and 46b are rectangles formed by the sides of surface 45a, the sides of surface 45b, and two sides parallel to the Z direction, and are arranged opposite each other and parallel to the Z direction. Surfaces 45a, 45b, 46a, and 46b form a cylindrical shape, and the space enclosed by these surfaces becomes the internal space T of the port 43, where the exit axis EA is located.

[0128] The area of ​​the downstream opening 47b of port 43 is larger than the area of ​​the light-emitting opening 47a. Also, the cross-sectional area of ​​the most negative portion in the Y direction, as defined by the XZ plane, is S, and the distance from the irradiation position I to that portion is X.

[0129] If there are spatial constraints when arranging port 43, such a shape may be adopted in accordance with the arrangement of other mechanisms. In addition, any port shape and arrangement may be adopted that has a cylindrical shape, through which radiation R passes, and where the area of ​​the downstream opening is larger than the area of ​​the light-emitting opening, satisfying the conditional equation.

[0130] Furthermore, a foil trap for capturing debris may be placed in the internal space of the port 23 in this invention. For example, by arranging the foil along the radiation R emitted from the irradiation position I, it is possible to allow the radiation R to pass through the internal space T of the port 23 while further enhancing the removal of debris generated from the irradiation position I.

[0131] [Margin] In the example shown in Figure 8, the minimum value of the cross-sectional area of ​​the conduit 35 and the internal space T was defined as S, so S included the cross-sectional area of ​​the conduit 35 itself. This margin was added to S to avoid a situation where radiation R would not be sufficiently transmitted, taking into account the misalignment of the port 23.

[0132] On the other hand, margins do not need to be considered. That is, even if the minimum value of the cross-sectional area of ​​only the internal space T is taken as S, equation (2) may still be satisfied for θ calculated by equation (1).

[0133] Furthermore, even if we consider the minimum value of the cross-sectional area of ​​only the internal space T as S, the condition 5° ≤ θ ≤ 20° may still hold.

[0134] Furthermore, in the case of a port 23 having a frustoconical shape, if the design opening angle is θ', the conditional equation may be examined based on θ = θ' + α with a margin. Also, considering a safety factor, processing such as multiplying a predetermined parameter by, for example, 150% may be performed.

[0135] [Types of Plasma Materials] The specific type of plasma material 101 is not limited. For example, not only completely liquid plasma material 101, but also plasma material 101 in which solid material in the process of melting is mixed in with the liquid may be used.

[0136] [Application to other devices] In this example, we have described the case in which this technology is applied to an LPP light source device, but it is not limited to this, and this technology may also be applied to DPP or LDP light source devices.

[0137] It is also possible to combine at least two of the feature features of this technology described above. Furthermore, the various effects described above are merely examples and not limiting, and other effects may also be exhibited.

[0138] EA...Exit axis EB...Energy beam I...Irradiation position P...Plasma R...Radiation T, T'...Internal space 19...Housing 22...Light extraction unit 23, 34, 43, 51...Port 24...Focusing mirror 25, 35, 44, 53...Conduit 26a, 26b, 36a, 36b, 47a, 47b...Opening 27...Gas inlet 28, 52...Flow meter 40...Partition 45a, 45b, 46a, 46b...Surface 50...Injection unit 54...Debris reduction tool 100...Light source device 101...Plasma raw material 103...Vacuum chamber 106...Plasma generation mechanism

Claims

1. A light source device that generates radiation by plasmaizing a raw material by injecting energy, comprising: a chamber; a raw material supply unit housed in the chamber and supplying the raw material to an energy irradiation position; an energy source that generates plasma by injecting the energy to the energy irradiation position; a port having a conduit, arranged such that the radiation or energy passes through the internal space surrounded by the conduit, and in the arrangement, when the opening closer to the energy irradiation position is designated as the light-emitting side opening and the opening further away is designated as the downstream side opening, the area of ​​the downstream side opening is larger than the area of ​​the light-emitting side opening; and a gas introduction unit configured closer to the energy irradiation position than the downstream side opening, wherein the minimum value of the cross-sectional area of ​​the conduit and the internal space in a plane perpendicular to the optical axis of the radiation or the optical axis of the energy is S (mm ２ ) and the distance between the energy irradiation position and the cross-section with the minimum cross-sectional area is X (mm). Assuming that the distance between the energy irradiation position and the light-emitting aperture is d (mm), A light source device.

2. A light source device according to claim 1, wherein the port is arranged such that the radiation passes through an internal space surrounded by the conduit, and the S (mm ２ ) is a light source device in which the cross-sectional area of ​​the conduit and the internal space is the minimum value of a plane perpendicular to the optical axis of the radiation.

3. A light source device according to claim 1 or 2, wherein the port is arranged such that the energy passes through an internal space surrounded by the conduit, and the S (mm ２ ) is a light source device in which the cross-sectional area of ​​the conduit and the internal space is the minimum value of a plane perpendicular to the optical axis of the energy.

4. A light source device according to claim 3, further comprising a debris reduction device for capturing debris generated at the energy irradiation position.

5. A light source device according to claim 1 or 2, wherein 5° ≤ θ ≤ 20°.

6. A light source device according to claim 1 or 2, wherein the conduit has the shape of a frustocone.

7. A light source device according to claim 1 or 2, wherein the conduit has two opposing substantially fan-shaped surfaces and two opposing rectangular surfaces.

8. A light source device according to claim 1 or 2, wherein the gas introduction section is an opening configured in the conduit.

9. A light source device according to claim 1 or 2, wherein the gas introduction section is configured in the space between the energy irradiation position and the light-emitting side opening.

10. A light source device according to claim 1 or 2, wherein the raw material supply unit has a housing that surrounds the energy irradiation position and forms a plasma generation space.

11. A light source device according to claim 10, wherein the port is a light source device fixed to the housing.

12. A light source device according to claim 1 or 2, further comprising a focusing mirror positioned on the optical axis at a position further from the energy irradiation position than the port, wherein the chamber has a partition separating the port and the focusing mirror, and the port is fixed to the partition.

13. A light source device according to claim 1 or 2, wherein the minimum value of the cross-sectional area of ​​the internal space only by the plane is S (mm ２ A light source device that satisfies the condition 5° ≤ θ ≤ 20°, even when ) is assumed.

14. A light source device according to claim 1 or 2, wherein the port has an adjustment mechanism for adjusting the position of the conduit.

15. A light source device according to claim 1 or 2, further comprising a measuring unit for measuring the amount of gas introduced by the gas introduction unit.

16. A light source device for generating radiation by plasmaizing a raw material by injecting energy, comprising: a chamber; a raw material supply unit housed in the chamber and supplying the raw material to an energy irradiation position; an energy source for generating plasma by injecting the energy to the energy irradiation position; a port having a conduit, arranged such that the radiation or energy passes through the internal space surrounded by the conduit, and in the arrangement, when the opening closer to the energy irradiation position is designated as the light-emitting side opening and the opening further away is designated as the downstream side opening, the area of ​​the downstream side opening is larger than the area of ​​the light-emitting side opening; and a gas introduction unit configured to be closer to the energy irradiation position than the downstream side opening, wherein the minimum value of the cross-sectional area of ​​the conduit and the internal space in a plane perpendicular to the optical axis of the radiation or the optical axis of the energy is S (mm ２ ) and the distance between the energy irradiation position and the cross-section with the minimum cross-sectional area is X (mm). Assuming that the distance between the energy irradiation position and the light-emitting aperture is d (mm), A method for extracting radiation.

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