Plasma generation mechanism and light source device

Abstract

Provided are a plasma generation mechanism and a light source device which are capable of suppressing defects caused by debris that occur due to plasma generation.　A plasma generation mechanism according to an embodiment of the present invention is a plasma generation mechanism of a light source device that converts a liquid plasma raw material into plasma as a result of irradiation with an energy beam and that extracts radiation. Said plasma generation mechanism is provided with a rotating body, a rotation drive source, a raw material supply unit, and a debris reflection surface. The rotating body has a rotating surface which is a surface that rotates about a rotation axis. The rotation drive source rotates the rotating body about the rotation axis. The raw material supply unit supplies the plasma raw material to the rotating body. The debris reflection surface is located in a normal direction of an irradiation position irradiated with the energy beam, and reflects, in a direction different from the incidence path of the energy beam to the irradiation position, debris incident from the irradiation position.

Description

Plasma generation mechanism and light source device

[0001] The present invention relates to a plasma generation mechanism and a light source device that supply plasma raw material to an energy beam irradiation position to generate plasma.

[0002] Traditionally, X-rays have been used for medical, industrial, and research applications. In the medical field, X-rays are used for applications such as chest radiography, dental radiography, and CT (Computer Tomography). In the industrial field, X-rays are used for applications such as non-destructive testing and tomographic non-destructive testing to observe the interior of materials such as structures and welds. In the research field, X-rays are used for applications such as X-ray diffraction to analyze the crystalline structure of materials and X-ray spectroscopy (X-ray fluorescence analysis) to analyze the constituent elements of materials. Extreme ultraviolet light (hereinafter also referred to as "EUV (Extreme Ultra Violet) light") with a wavelength of 13.5 nm, which is in the soft X-ray region with a relatively long wavelength among X-rays, has recently been used as exposure light.

[0003] Some EUV light source devices generate EUV light by irradiating a plasma raw material, such as molten tin or lithium, with an energy beam to excite it, thereby generating high-temperature plasma, from which EUV light is extracted. Methods that use laser light as the energy beam are called LPP (Laser Produced Plasma), and methods that use electrical discharge are called DPP (Discharge Produced Plasma) or LDP (Laser Assisted Discharge Produced Plasma).

[0004] Known LPP-type EUV light source devices generate plasma by exciting plasma raw material droplets by focusing laser light on the droplets. In contrast, a method has recently been developed for supplying plasma raw material to a laser light irradiation area using the centrifugal force of a rotor (see, for example, Patent Document 1). In this method, the rotor rotates with its lower portion immersed in the stored plasma raw material, causing the plasma raw material to adhere to the rotor surface, supplying the plasma raw material to the irradiation area on the rotor surface. This method does not require the plasma raw material to be supplied as droplets, and therefore can produce high-intensity radiation with a relatively simple configuration compared to methods that focus laser light on droplets.

[0005] JP 2014-216286 A

[0006] However, when a plasma raw material is irradiated with laser light, debris, which is vapor and fumes of the plasma raw material, is generated along with the plasma. As described in Patent Document 1, when a laser light is irradiated onto the surface of a rotating body coated with a plasma raw material, a large amount of debris is ejected in the normal direction of the rotating body surface. Even if the rotating body is surrounded by a cover and the debris is sealed off with the cover, the cover still needs an opening to allow the laser light and EUV light to pass through.

[0007] If debris is released from this opening, it may adhere to external components and cause problems such as unnecessary electrical conduction. Furthermore, if debris adheres to the opening, it may narrow the opening, blocking or attenuating the laser light or EUV light passing through the opening, which may result in a decrease in the output of the EUV light. Furthermore, if debris floats near the opening, the debris may absorb the EUV light, which may also result in a decrease in the output of the EUV light.

[0008] In view of the above circumstances, an object of the present invention is to provide a plasma generation mechanism and a light source device that can suppress problems caused by debris that occurs during plasma generation.

[0009] In order to achieve the above object, one embodiment of the present invention provides a plasma generation mechanism included in a light source device that converts a liquid plasma raw material into plasma by irradiating it with an energy beam to extract radiation, and includes a rotor, a rotary drive source, a raw material supply unit, and a debris reflecting surface. The rotor has a rotation surface that rotates around a rotation axis. The rotary drive source rotates the rotor around the rotation axis. The raw material supply unit supplies the plasma raw material to the rotor. The debris reflecting surface is located in the normal direction of an irradiation position where the energy beam is irradiated, and reflects debris incident from the irradiation position in a direction different from the incident path of the energy beam to the irradiation position.

[0010] With this configuration, when an energy beam is incident on the irradiation position and debris is generated at the irradiation position, the debris is incident on a debris-reflecting surface located in the normal direction to the irradiation position and is reflected in a direction different from the incident path of the energy beam, thereby suppressing the effect of the debris on the energy beam and preventing a decrease in radiation output, etc.

[0011] The irradiation position may be located on the plane of rotation.

[0012] The debris reflecting surface may reflect debris incident from the irradiation position in a direction different from the path of incidence of the energy beam to the irradiation position and the path of emission of the radiation from the irradiation position.

[0013] The raw material supply unit may have a storage tank for storing the plasma raw material, and the rotating body may have a rotation surface that is partially immersed in the plasma raw material stored in the storage tank.

[0014] The debris reflecting surface may be configured such that a normal direction at each position on the debris reflecting surface faces into the cover.

[0015] The cover may have an opening through which the energy beam passes, and the debris reflecting surface may reflect debris incident from the irradiation position in a direction different from the direction of the opening.

[0016] The opening may include an entrance through which the energy beam passes and an exit through which the radiation passes, and the debris-reflecting surface may face the irradiation position through the opening.

[0017] The cover may have an opposing surface facing the rotation surface, and the debris reflecting surface may be a surface of a debris reflecting structure provided at a position on the opposing surface facing the irradiation position.

[0018] The debris reflecting surface may be a surface of a debris reflecting structure supported by a support member separate from the cover.

[0019] The debris-reflecting surface may be at least partially curved.

[0020] The debris reflecting surface may be a surface of a rotating debris reflecting structure.

[0021] The radiation may be extreme ultraviolet light or x-rays.

[0022] The plasma raw material may be tin, lithium, gadolinium, terbium, gallium, bismuth, indium, or an alloy containing at least one of these materials.

[0023] To achieve the above object, one aspect of the present invention provides a light source device that converts a liquid plasma raw material into plasma by irradiating it with an energy beam to produce radiation, and includes a plasma generation mechanism and a beam source. The plasma generation mechanism includes a rotor having a rotation surface that rotates around an axis of rotation, a rotary drive source that rotates the rotor about the axis of rotation, a raw material supply unit that supplies the plasma raw material to the rotor, and a debris reflection surface that is positioned in a normal direction to an irradiation position where the energy beam is irradiated and that reflects debris incident from the irradiation position in a direction different from the path of incidence of the energy beam to the irradiation position. The beam source irradiates the energy beam at the irradiation position.

[0024] According to the present invention, it is possible to provide a plasma generation mechanism and a light source device that are capable of suppressing defects caused by debris that occurs during plasma generation.

[0025] 1 is a schematic diagram of a light source device according to an embodiment of the present invention. FIG. 1 is a schematic diagram of a plasma generation mechanism provided in the light source device. FIG. 2 is a perspective view of a rotating body unit provided in the plasma generation mechanism. FIG. 2 is a schematic diagram showing the operation of the light source device. FIG. 3 is a schematic diagram showing the operation of a light source device without a debris reflection structure. FIG. 4 is a schematic diagram showing the incidence angle and reflection angle of debris incident on the debris reflection surface of the debris reflection structure. FIG. 5 is a graph of simulation results (impact angle 45°). FIG. 6 is a graph of simulation results (impact angle 60°). FIG. 7 is a graph plotting the average recoil angle against the impact angle in the simulation results. FIG. 8 is a perspective view of a debris reflection structure having another configuration. FIG. 9 is a schematic diagram showing the reflection of debris on the debris reflection surface. FIG. 10 is a schematic diagram showing the normal direction at the debris reflection surface of a debris reflection structure having another configuration. FIG. 11 is a perspective view of a debris reflection structure having another support structure. FIG. 12 is a cross-sectional view of a rotating body unit provided with a rotatably configured debris reflection structure. FIG. 13 is a cross-sectional view of a rotating body unit provided with a rotary foil trap.

[0026] A light source device according to an embodiment of the present invention will be described.

[0027] [Basic Configuration of Light Source Device] Fig. 1 is a schematic diagram showing an example of the configuration of a light source device 100 according to this embodiment. The light source device 100 is a laser-produced plasma (LPP) type light source device. That is, as shown in Fig. 1, the light source device 100 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 (Extreme Ultraviolet) light, X-rays, or other electromagnetic waves.

[0028] The plasma raw material 101 is liquid and is tin (Sn), lithium (Li), gadolinium (Gd), terbium (Tb), gallium (Ga), bismuth (Bi), indium (In), or an alloy containing at least one of these materials. When EUV light is emitted as the radiation R, molten Sn or Li is used as the plasma raw material 101. When X-rays are emitted as the radiation R, molten Ga, a Ga alloy, an Sn compound, or the like is used as the plasma raw material 101.

[0029] 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 are omitted for ease of understanding the configuration and operation of the light source device 100. Hereinafter, the X direction will be described 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 will be described as the front-to-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 will be described 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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. Furthermore, the gas inside the application chamber 110 may be exhausted by an exhaust means (not shown). A filter film 111 is 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.

[0036] 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.

[0037] 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.

[0038] 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 rotor 120, onto which an energy beam EB is incident. The rotor 120 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. The plasma generation mechanism 106 will be described in detail later.

[0039] 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. The control unit 107 has hardware circuits necessary for a computer, such as a CPU and memory (RAM, ROM). The CPU loads a control program stored in the memory into the RAM and executes it, thereby executing various processes. A device such as a PLD (Programmable Logic Device) may be used as the control unit 107. Although the control unit 107 is schematically illustrated as a functional block in FIG. 1 , the location where the control unit 107 is configured may be designed as desired.

[0040] 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 from the plasma P.

[0041] [Configuration of Plasma Generation Mechanism] As described above, 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). Figure 2 is a schematic diagram of the plasma generation mechanism 106. As shown in the figure, the plasma generation mechanism 106 includes a rotor 120, a rotary drive source 131, a shaft 132, a storage tank 133, and a film thickness adjustment mechanism 134.

[0042] Rotational drive source 131 is disposed outside vacuum chamber 103 and generates rotational power for rotating body 120. Rotational drive source 131 is, for example, a motor. Shaft 132 passes through chamber main body 109 and housing 102 to connect rotational drive source 131 and rotating body 120 and transmits the rotational power generated by rotational drive source 131 to rotating body 120. Storage tank 133 is disposed vertically below rotating body 120 and stores plasma raw material 101.

[0043] The rotating body 120 is disposed in the vacuum chamber 103 and is connected to a shaft portion 132. The rotating body 120 rotates due to the rotation of the shaft portion 132, as shown by an arrow S in Fig. 2. Hereinafter, the rotation axis of the rotating body 120 and the shaft portion 132 will be referred to as a rotation axis M.

[0044] As shown in Figure 2, the rotor 120 has a disk shape. Hereinafter, the surface of the rotor 120 opposite the shaft 132 will be referred to as the rotation surface 120a. The rotation axis M is, for example, parallel to the horizontal direction (X-Y direction), and the rotation surface 120a is arranged so that it is parallel to the vertical direction. A portion of the rotation surface 120a is immersed in the plasma raw material 101 stored in the storage tank 133, and the plasma raw material 101 adheres to the rotation surface 120a as the rotor 120 rotates. The plasma raw material 101 adhered to the rotation surface 120a is transported to the irradiation position I as the rotor 120 rotates, and is converted into plasma by the energy beam EB irradiated at the irradiation position I.

[0045] 2, film thickness adjustment mechanism 134 is disposed on rotor 120 and adjusts the film thickness of plasma raw material 101 adhering to rotation surface 120a. Film thickness adjustment mechanism 134 is, for example, a structure having a channel structure, and is disposed inside thereof with a predetermined gap so as to sandwich rotor 120, and adjusts the film thickness of plasma raw material 101 by scraping off any plasma raw material 101 that has not flowed into the gap. Film thickness adjustment mechanism 134 is disposed upstream of irradiation position I in the rotation direction of rotor 120, and determines the film thickness of plasma raw material 101 at irradiation position I.

[0046] In the plasma generation mechanism 106, the plasma raw material 101 stored in the storage tank 133 as described above adheres to the rotation surface 120a of the rotor 120 and is transported to the irradiation position I by the rotation of the rotor 120. Therefore, the storage tank 133 functions as a "raw material supply unit" that supplies the plasma raw material 101 to the rotation surface 120a.

[0047] [Configuration of Rotating Body Unit] The plasma generation mechanism 106 includes a rotating body unit that houses the rotating body 120. FIG. 3 is a perspective view of the rotating body unit 150. As shown in the figure, the rotating body unit 150 includes the rotating body 120 and a cover 160, and the rotating body 120 is housed in the cover 160. Note that the cover 160 is not shown in FIGS. 1 and 2. FIG. 4 is a cross-sectional view of the rotating body unit 150, taken along line A1-A1 (X-Y plane) in FIG. 3.

[0048] Cover 160 surrounds rotor 120 to prevent debris from scattering and also forms storage tank 133. Cover 160 is made up of a first cover member 161 and a second cover member 162. As shown in Figure 3, rotor 120 is housed inside cover 160. Plasma raw material 101 is stored in the vertically lower part of cover 160, and this vertically lower part of cover 160 forms storage tank 133. A heating mechanism (not shown) is provided around storage tank 133, and heats and melts the plasma raw material 101 stored in storage tank 133.

[0049] As shown in Fig. 4, the first cover member 161 has a bottom 161a and a side wall 161b. The bottom 161a has a disk shape and has a through hole 161c provided in the center as shown in Fig. 4. The through hole 161c is a hole through which the shaft 132 is inserted. The side wall 161b has a cylindrical shape and is continuous with the periphery of the bottom 161a.

[0050] The second cover member 162 is joined to the side wall portion 161b of the first cover member 161 as shown in Fig. 4. As shown in the figure, the second cover member 162 has a flat plate portion 163 and a debris reflecting structure 164. The flat plate portion 163 has a flat plate shape and faces the rotation surface 120a of the rotating body 120 as shown in Fig. 4. As shown in Fig. 4, the surface of the flat plate portion 163 facing the rotation surface 120a is referred to as an opposing surface 163a. ​​The opposing surface 163a is a surface parallel to the rotation surface 120a, for example, a surface parallel to the vertical direction.

[0051] 4, an opening 166 is provided in the flat plate portion 163. The opening 166 is provided to penetrate the second cover member 162, and is an opening through which the energy beam EB and the radiation R pass.

[0052] The debris reflecting structure 164 faces the irradiation position I and reflects debris generated as plasma is generated. As shown in FIG. 4 , the debris reflecting structure 164 is provided at a position on the opposing surface 163 a facing the irradiation position I, and more specifically, is provided adjacent to the opening 166.

[0053] The debris reflecting structure 164 has a debris reflecting surface 164a. The debris reflecting surface 164a is the surface of the debris reflecting structure 164 facing the rotor 120, and is a surface that reflects debris incident from the irradiation position I. As shown in Figure 4, the debris reflecting surface 164a is located in the normal direction H1 of the irradiation position I, and reflects debris incident from the irradiation position I in a direction different from the incident path of the energy beam EB to the irradiation position I and the exit path of the radiation R from the irradiation position I. Specifically, the debris reflecting surface 164a reflects debris in a direction different from the opening 166.

[0054] The debris reflecting surface 164a is a surface where at least a portion is not perpendicular to the normal direction H1 and is not parallel to the normal direction H1. As shown in Figure 4, the normal direction of the debris reflecting surface 164a is defined as normal direction H2. As shown in the figure, the debris reflecting surface 164a is a plane inclined with respect to the opposing surface 163a, and is a surface to which the normal direction H2 at each position is parallel.

[0055] [Operation and Effects of Light Source Device] The operation and effects of light source device 100 will now be described. Energy beam EB converts plasma raw material 101 into plasma at irradiation position I, generating plasma P as shown in Figure 4. Radiation R (see Figure 1) is emitted from plasma P and is emitted through opening 166. As this plasma is converted into plasma, debris D, which is vapor and mist of plasma raw material 101, is ejected from irradiation position I as shown in Figure 4. Debris D is ejected mainly along the normal direction H1 (Y direction) of the plane of rotation 120a.

[0056] Here, in the rotating body unit 150, the debris reflecting surface 164a is located in the normal direction H1 of the irradiation position I. Therefore, the debris D ejected from the irradiation position I collides with the debris reflecting surface 164a and is reflected by the debris reflecting surface 164a. If the direction in which the debris D is reflected by the debris reflecting surface 164a is taken as the reflection direction T, the reflection direction T is a direction toward the inside of the cover 160, which is a direction different from the opening 166. Specifically, the reflection direction can be controlled by the normal direction H2 of the debris reflecting surface 164a (see FIG. 4).

[0057] 5 is a schematic diagram showing the operation of the light source device 100 in the case where the debris reflecting structure 164 is not provided. As shown in the figure, when debris D is ejected from the irradiation position I, the debris D collides with the opposing surface 163a, generating debris D' containing various small particles. The debris D' diffuses within the cover 160, and some of it adheres to the opening 166. The debris D' adhering to the opening 166 narrows the opening 166, blocking or attenuating the energy beam EB and radiation R passing through the opening 166, resulting in a decrease in the output of the radiation R.

[0058] Furthermore, if debris D' floats near the opening 166, the debris D' will absorb the radiation R, which also reduces the output of the radiation R. In addition, if debris D' is released from the opening 166, it will adhere to components inside the vacuum chamber 103 (see FIG. 1), causing problems such as unnecessary electrical conduction.

[0059] 4, when the debris reflecting surface 164a is provided, the debris D is reflected by the debris reflecting surface 164a in a reflection direction T different from that of the opening 166, preventing the debris D from adhering to the opening 166. This prevents the energy beam EB and radiation R from being blocked or attenuated, and prevents a reduction in the output of the radiation R caused by the debris D. Furthermore, since the release of the debris D from the opening 166 is also suppressed, it is also possible to prevent malfunctions of external components.

[0060] [Regarding the Incident Portion and the Exit Portion] As described above, the debris reflecting surface 164a reflects the debris incident from the irradiation position I in a direction different from that of the opening 166. Here, the opening 166 may include an incident port and an exit port. The incident port 167 is provided in the flat plate portion 163 and is an opening through which the energy beam EB passes. The exit port 168 is provided in the flat plate portion 163 and is an opening through which the radiation R passes. In this case, the debris reflecting surface 164a is configured so that the component H3 faces in a direction different from that of the incident port 167 and the exit port 168. In this case, too, it is possible to suppress adhesion of debris D to the incident port 167 and the exit port 168 and release of debris D from the incident port 167 and the exit port 168. The debris reflecting surface 164a may also be configured so that the component H3 faces in the direction of the exit port 168. In this case, too, the debris D reflected by the debris reflecting surface 164a scatters at a shallower angle relative to the exit port 168 than when the debris reflecting structure 164 is not provided (see Figure 5), thereby preventing the debris D from adhering to the entrance port 167 and the exit port 168 and the debris D from being released from the entrance port 167 and the exit port 168.

[0061] [Regarding the angle of the debris reflecting surface] The angle of the debris reflecting surface 164a will now be described. Figure 6 is a schematic diagram showing the angle of incidence and the angle of reflection of debris D incident on the debris reflecting surface 164a. As shown in the figure, the angle of the debris D incident on the debris reflecting surface 164a with respect to the normal direction H2 is defined as the incidence angle θ1, and the angle of the debris D reflected by the debris reflecting surface 164a with respect to the normal direction H2 is defined as the reflection angle θ2.

[0062] Here, the angle of the debris reflecting surface 164a and the reflection angle of the debris D were investigated by simulation. Using the binary collision simulation software TRIM (Transpotation of Ion in Material), a Monte Carlo calculation using the binary collision approximation was performed to determine the recoil direction of the ion N according to the incident energy and the collision angle with the collision surface G, as shown in FIG. 6. The normal direction of the collision surface G is defined as the normal direction K, the angle of the ion N colliding with the collision surface G relative to the normal direction K is defined as the collision angle φ1, and the angle of the ion N recoiling from the collision surface G relative to the normal direction K is defined as the recoil angle φ2. In this simulation, attention is focused on the behavior of the ion N projected onto the X-Y plane.

[0063] For example, if the impact angle φ1 is 45° and the recoil angle φ2 is -45°, the ion N will return to the injection point. Because the likelihood of the ion N recoiling varies depending on the incident energy and impact angle of the ion N, calculations were performed until the number of recoiled ions N reached a sufficient number of samples to investigate the angular distribution. For example, when the incident energy was 5 keV and the impact angle φ1 was 45°, 6 million samples of ions were collided with the impact surface G, and the recoil angle φ2 was evaluated.

[0064] In calculations, the direction of ion travel may change slightly between the ion injection point and the collision surface G. Therefore, the collision angle φ1 will not be exactly the specified value. However, since debris is thought to be generated with a certain degree of spread in actual light source devices, this is not a practical problem.

[0065] Fig. 7 is a graph showing the distribution of recoiled ions at each incident energy when the collision angle φ1 is 45°, and Fig. 8 is a graph showing the distribution of recoiled ions at each incident energy when the collision angle φ1 is 60°.

[0066] As shown in these figures, when the incident energy is 1 keV, the recoil angle φ2 peaks at approximately 30° to 40°. The incident energy of 1 eV is the lowest energy among the conditions examined. The higher the energy of the debris, the greater the damage caused to the focusing mirror and other components upon collision. However, the proportion of low-energy debris in the total number of debris is thought to be higher than for the other energies simulated. Since the recoil angle φ2 peaks at approximately 30° to 40°, when the incident energy is 1 keV, the total number of debris D reflected by the debris reflecting surface 164a and incident at irradiation position I is clearly smaller than the total number of debris D incident at other positions. When the incident energy is 100 keV, the recoil angle φ2 peaks at approximately 30° to 40° in all calculation results.

[0067] 7 and 8, it can be seen that as the collision angle φ1 increases, the recoil angle φ2 converges to a certain angle. Furthermore, in this model, as the angle of the collision surface G becomes steeper, the normal direction K moves away from the incident direction of the ions N, and therefore it is shown that the reflection angle θ2 of the debris D can be controlled by changing the angle of the debris reflecting surface 164a with respect to the incident direction of the debris D.

[0068] Figure 9 is a graph plotting the average recoil angle against the impact angle φ1. The average recoil angle is the average value of the recoil angles φ2. As shown in the figure, regardless of the ion energy, the recoil angle φ2 [degrees] is 40Ln (0.018φ1) relative to the impact angle φ1 [degrees]. However, the peak of the recoil angle φ2 near 90° when the incident energy is 1 keV and the impact angle φ1 is 75° is excluded from this calculation.

[0069] As described above, the recoil angle φ2 and the total number of reflected ions N depend on the incident energy and collision angle φ1 of the ions N. Furthermore, since it was observed that ions N tend to recoil more easily as the collision angle φ1 increases, providing a debris reflecting surface 164a is effective in preventing debris D from returning to the irradiation position I as much as possible. The variation in the recoil angle φ2 was approximately σ = 15 to 35°. There are several possible factors for this variation, and one factor that may be contributing to this is that the calculated collision angle φ1 does not strictly match the specified value. Considering the variation in the collision angle φ1 and the recoil angle φ2, it is preferable to have a means for limiting the destination of debris D reflected by the debris reflecting surface 164a, as will be described later.

[0070] [Various Configurations of the Debris Reflecting Structure] As described above, the debris reflecting structure 164 can have various configurations as long as the debris reflecting surface 164a reflects debris incident from the irradiation position I in a direction different from the incidence path of the energy beam EB to the irradiation position I. Figures 10 to 12 are schematic diagrams of debris reflecting structures 164 having various configurations.

[0071] 10, the debris-reflecting surface 164a may have a flat surface 171 and a curved recess 172. As described above, the normal direction H2 of the debris-reflecting surface 164a is a direction in which the component H3 (see FIG. 4) parallel to the plane of rotation 120a (Z-X plane) faces in a direction different from the opening 166.

[0072] 11 is a schematic diagram showing the reflection of debris D by this debris reflecting surface 164a. As shown in the figure, by making the debris reflecting surface 164a curved, it is possible to reflect the debris D in a manner that concentrates it in one direction. When the irradiation position I and the debris reflecting surface 164a are close, it is sufficient to make only a portion of the surface curved in this way.

[0073] The debris reflecting surface 164a may also have a shape having a flat surface and a hemispherical recess. In this case, the debris D can be reflected in a manner that gathers it at one point. The debris reflecting surface 164a may also be configured by combining multiple small curved surfaces. In this case, the debris D cannot be gathered in one direction, but it is possible to suppress the dispersion of the debris D. Furthermore, the debris reflecting surface 164a may also be configured in a stepped shape that combines multiple small flat surfaces.

[0074] Furthermore, the debris reflecting surface 164a may have a C-shape when viewed from the normal direction H1 (Y direction) as shown in Fig. 12. As shown in Fig. 12, it is preferable that the component H3 at each position of this debris reflecting surface 164a is inside the C-shape and faces in a direction different from the opening 166. Furthermore, the debris reflecting surface 164a may have a flat surface and a curved recess.

[0075] Furthermore, the debris reflecting surface 164a may have a C-shape when viewed from the normal direction H1 (Y direction), with the component H3 at each position facing outside the C-shape and in a direction different from that of the opening 166. Also, a plurality of debris reflecting structures 164 may be provided, and a plurality of debris reflecting surfaces 164a may also be provided. In this case, the component H3 at each position may also face in a direction different from that of the opening 166.

[0076] The support structure for the debris reflection structure 164 is not limited to being disposed on the flat plate portion 163 of the cover 160 as described above. FIG. 13 is a schematic diagram showing the support structure for the debris reflection structure 164. As shown in the figure, the flat plate portion 163 has an opening 169 at a position facing the irradiation position I. The debris reflection structure 164 is supported by a support member 181 separate from the cover 160, and the debris reflection surface 164a faces the irradiation position I through the opening 169. The support member 181 is not particularly limited, but can be, for example, a cantilever structure that connects the debris reflection structure 164 to an external member such as the chamber main body 109 (see FIG. 1). The support member 181 can be moved toward and away from the rotating body 120 as indicated by the arrow in the figure, making it possible to adjust the distance between the debris reflection surface 164a and the rotating surface 120a.

[0077] The debris reflecting structure 164 may also be rotatable. Figure 14 is a cross-sectional view of a rotating body unit 150 equipped with a rotatable debris reflecting structure 164. As shown in the figure, the debris reflecting structure 164 has a rotation axis 164b and is configured to be rotatable around the rotation axis 164b. The rotation axis 164b is an axis extending in a direction (X direction) perpendicular to the normal direction H1 (see Figure 4). The debris reflecting surface 164a is the surface around the rotation axis 164b of the debris reflecting structure 164, and a part of it faces the irradiation position I through an opening 169. When the debris reflecting structure 164 rotates, the part of the debris reflecting surface 164a facing the irradiation position I changes with the rotation.

[0078] When debris D is incident on the debris reflecting surface 164a, the debris reflecting surface 164a is heated by the kinetic energy of the debris D. By rotating the debris reflecting structure 164, the debris reflecting surface 164a facing the irradiation position I can be switched, thereby extending the life of the debris reflecting structure 164.

[0079] It is also possible to make the debris reflecting surface 164a curved in the rotatable debris reflecting structure 164. In addition, it is also possible for the debris reflecting structure 164 to be rotatable and for the debris reflecting surface 164a to have any of the various shapes described above.

[0080] A rotating foil trap can also be used to rotate the debris reflective structure 164. Figure 15 is a cross-sectional view of a rotating body unit 150 including a rotating foil trap 190. As shown in the figure, the rotating foil trap 190 includes a central support 191, a foil 192, and an outer ring 193.

[0081] The central support 191 is connected to a rotary drive source (not shown) and rotates around a rotation axis F. The foils 192 are connected to the central support 191 and are plate-shaped and parallel to the traveling direction of the radiation R emitted from the irradiation position I, with a plurality of foils 192 provided radially when viewed from the direction of the rotation axis F. The outer ring 193 is an annular member centered on the rotation axis F and surrounds the periphery of the foil 192. In the rotary foil trap 190, the foil 192 rotates around the rotation axis F, causing debris that has passed through the opening 166 to collide with the foil 192 and be captured by the foil 192.

[0082] The debris reflecting structure 164 is connected to the rotary foil trap 190 and rotates as the rotary foil trap 190 rotates. Specifically, the debris reflecting structure 164 is arranged on a rotation axis F and supported by a support member 194 fixed to a central support column 191, and rotates around the rotation axis F when the central support column 191 rotates. The shape of the debris reflecting structure 164 is, for example, a cone shape centered on the rotation axis F. With this structure, the debris reflecting structure 164 can also be rotated by the rotation drive source for the rotary foil trap 190, eliminating the need to provide a separate rotation drive source for the debris reflecting structure 164.

[0083] Furthermore, in a configuration in which the debris reflective structure 164 is rotated using the rotation of the rotary foil trap 190, the debris reflective structure 164 may be supported by a support member, and the support member may be connected to the central support column 191 by a rotation transmission mechanism. The rotation transmission mechanism is a mechanism that transmits the rotation of the central support column 191 to the support member, and is composed of gears, etc.

[0084] As a result, when the central support 191 rotates around the rotation axis, the rotation is transmitted to the support member by the rotation transmission mechanism, and the support member and the debris reflection structure 164 rotate around the rotation axis. By using the rotation transmission mechanism, even if the debris reflection structure 164 is arranged away from the rotation axis of the rotary foil trap 190, it is possible to rotate the debris reflection structure 164 by the rotation drive source for the rotary foil trap 190. The shape of the debris reflection structure 164 is, for example, a cone shape centered on the rotation axis.

[0085] The configuration of the rotating foil trap 190 and the configuration that rotates the debris reflecting structure 164 through its rotation are not limited to those described above, and any configuration that can rotate the debris reflecting structure 164 through the rotation of the rotating foil trap 190 will suffice.

[0086] [About the present disclosure] It is possible to combine at least two of the above-described features of the present technology. Furthermore, the various effects described above are merely examples and are not intended to be limiting, and other effects may also be achieved.

[0087] DESCRIPTION OF SYMBOLS 100... Light source device 101... Plasma raw material 106... Plasma generation mechanism 108... Beam source 120... Rotating body 131... Rotation drive source 132... Shaft portion 133... Storage tank 134... Film thickness adjustment mechanism 150... Rotating body unit 160... Cover 161... First cover member 162... Second cover member 164... Debris reflection structure 164a... Debris reflection surface 164b... Rotating shaft 166... ​​Opening 167... Incident port 168... Exit port 169... Opening 190... Rotating foil trap

Claims

1. A plasma generation mechanism provided in a light source device that converts liquid plasma raw material into plasma by irradiating it with an energy beam to extract radiation, the plasma generation mechanism comprising: a rotor having a rotation surface that rotates around an axis of rotation; a rotary drive source that rotates said rotor about said axis of rotation; a raw material supply unit that supplies said plasma raw material to said rotor; and a debris reflection surface that is positioned in the normal direction of an irradiation position where the energy beam is irradiated, and that reflects debris incident from the irradiation position in a direction different from the incidence path of the energy beam to the irradiation position.

2. A plasma generation mechanism according to claim 1, wherein the irradiation position is located on the rotation surface.

3. A plasma generation mechanism as claimed in claim 1, wherein the debris reflecting surface reflects debris incident from the irradiation position in a direction different from the entrance path of the energy beam to the irradiation position and the exit path of the radiation from the irradiation position.

4. A plasma generation mechanism as claimed in claim 1, wherein the raw material supply unit has a storage tank for storing the plasma raw material, and the rotating body has a portion of its rotation surface immersed in the plasma raw material stored in the storage tank.

5. A plasma generation mechanism according to claim 4, further comprising a cover that forms the storage tank and surrounds the rotor, and the normal direction of the debris reflecting surface at each position on the debris reflecting surface faces into the cover.

6. A plasma generation mechanism according to claim 5, wherein the cover has an opening through which the energy beam passes, and the debris reflecting surface reflects the debris incident from the irradiation position in a direction different from that of the opening.

7. A plasma generation mechanism according to claim 6, wherein the opening includes an entrance through which the energy beam passes and an exit through which the radiation passes, and the debris reflection surface faces the irradiation position through the opening.

8. A plasma generation mechanism according to claim 5, wherein the cover has an opposing surface facing the rotating surface, and the debris reflection surface is a surface of a debris reflection structure provided at a position on the opposing surface facing the irradiation position.

9. A plasma generation mechanism according to claim 7, wherein the debris reflection surface is a surface of a debris reflection structure supported by a support member separate from the cover.

10. A plasma generation mechanism according to claim 1, wherein the debris reflecting surface is at least partially curved.

11. A plasma generation mechanism according to claim 1, wherein the debris reflecting surface is a surface of a rotating debris reflecting structure.

12. The plasma generation mechanism according to claim 1, wherein the radiation is extreme ultraviolet light or X-rays.

13. A plasma generation mechanism according to claim 1, wherein the plasma raw material is tin, lithium, gadolinium, terbium, gallium, bismuth, indium, or an alloy containing at least one of these materials.

14. A light source device that converts liquid plasma raw material into plasma by irradiating it with an energy beam to extract radiation, comprising: a rotor having a rotation surface that rotates around an axis of rotation, a rotary drive source that rotates said rotor about said axis of rotation, a raw material supply unit that supplies said plasma raw material to said rotor, a plasma generation mechanism that includes a debris reflection surface that is positioned in the normal direction of an irradiation position where the energy beam is irradiated and that reflects debris incident from the irradiation position in a direction different from the incidence path of the energy beam to the irradiation position, and a beam source that irradiates the energy beam at said irradiation position.

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