Light source device and cleaning method

Abstract

To provide a light source device capable of suppressing a change in a pressure on a light source side caused by a change in a pressure on an introduction side of emission light, and a cleaning method.SOLUTION: A light source device according to an embodiment of the present invention comprises a first vacuum chamber, a light source part, and a debris reduction device. The light source part generates plasma which becomes a light source in the first vacuum chamber. The debris reduction device reduces debris diffused from the plasma, forms a vacuum path which connects the first vacuum chamber to a second vacuum chamber into which emission light emitted from the plasma is introduced, and allows the emission light to pass therethrough, and generates a high pressure region having higher pressure than a pressure of the first vacuum chamber and a pressure of the second vacuum chamber so as to block the vacuum path.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a light source device that uses plasma as a light source and a cleaning method. [Background technology]

[0002] Conventionally, light source devices have been developed that generate synchrotron radiation using plasma as a light source. For example, synchrotron radiation in the X-ray region can be obtained by appropriately selecting the type of plasma raw material and the excitation energy for generating plasma. Among such synchrotron radiation, for example, X-rays with short wavelengths are used for various purposes such as X-ray photography, non-destructive testing, X-ray analysis, and X-ray spectroscopy. In recent years, extreme ultraviolet light (hereinafter also referred to as "EUV (Extreme Ultra Violet) light") with a wavelength of 13.5 nm in the soft X-ray region has been used as exposure light or inspection light.

[0003] Generally, EUV light source devices include a discharge produced plasma (DPP) light source device, a laser assisted discharge produced plasma (LDP) light source device, and a laser produced plasma (LPP) light source device.

[0004] The DPP light source device applies a high voltage between electrodes to which gaseous plasma raw material (discharge gas) containing EUV radiating species is supplied, generating high-density, high-temperature plasma through discharge, and utilizes the extreme ultraviolet light emitted from the plasma.

[0005] An LDP light source device is an improved version of a DPP light source device, and for example, it supplies liquid high-temperature plasma raw material (e.g., Sn (tin) or Li (lithium)) containing EUV radiating species to the surface of an electrode (discharge electrode) that generates a discharge, irradiates the raw material with an energy beam (e.g., an electron beam or laser beam) to vaporize the raw material, and then generates high-temperature plasma by discharge.

[0006] An LPP light source device excites an EUV radiating species with a laser beam or the like to generate high-temperature plasma. A known light source device of this type generates plasma by concentrating laser light on droplets of EUV radiating target material, such as tin (Sn) or lithium (Li), ejected in the form of tiny droplets. Another known LPP light source device generates plasma by supplying liquid high-temperature plasma raw material containing EUV radiating species to the surface of a rotating body and irradiating the surface of the rotating body with an energy beam (laser beam).

[0007] In addition, debris is dispersed at high speed from the plasma generated by these light source devices. This debris includes particles of high-temperature plasma raw material and particles of material of the discharge electrode that are sputtered with the generation of plasma. If such debris reaches a utilization device that utilizes radiation such as EUV light, it is possible that it may damage or contaminate optical elements such as reflective films provided in the utilization device. For this reason, the light source device is provided with a debris mitigation tool (also called a DMT (Debris Mitigation Tool)) that captures debris between the plasma and the utilization device to prevent debris dispersed from the plasma from entering the utilization device.

[0008] Thus, in a light source device that generates radiation light using plasma as a light source, it is important to maintain the pressure in the space on the light source side where the plasma is generated. For example, Patent Document 1 describes a DPP type light source device that maintains the pressure on the light source side using an aperture member. In this light source device, an aperture member is provided between a discharge space where plasma is generated by discharge and a collection space where an EUV light collection section is provided. In addition, a gas curtain is formed downstream of the aperture member to reduce debris from the plasma. With this configuration, it is possible to maintain a pressure difference between the collection space and the discharge space and efficiently reduce debris (paragraphs

[0027] and

[0033] Fig. 1 of the specification of Patent Document 1, etc.).

[0009] Incidentally, there are cases where the pressure of the space on the introduction side where the synchrotron radiation is introduced needs to be changed. For example, Patent Document 2 describes a method for cleaning an optical element irradiated with light in an irradiation device that irradiates extreme ultraviolet rays or the like. In this method, a reaction partner containing hydrogen or halogen is supplied near the optical element during operation of the irradiation device, and debris attached to the optical element is cleaned using the reaction partner that has become a radical due to the light (paragraphs

[0114] -

[0116] , FIG. 1, etc. of the specification of Patent Document 1). In this method, it is considered that the pressure of the space in which the optical element is provided changes when the reaction partner is supplied or when the supply is stopped. In addition to this, there are cases where the pressure on the introduction side of the synchrotron radiation needs to be changed depending on the maintenance of the device, changes in conditions, etc. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2007-179881 A [Patent Document 2] Special Publication No. 2006-529057 Summary of the Invention [Problem to be solved by the invention]

[0011] In this way, when the pressure on the introduction side where the synchrotron radiation is introduced is changed, there is a possibility that the pressure on the light source side will change accordingly. In this case, the conditions for generating plasma on the light source side may be lost, and the emission of synchrotron radiation may become unstable. For this reason, there is a demand for a technology that suppresses the change in pressure on the light source side caused by the change in pressure on the introduction side of the synchrotron radiation.

[0012] In view of the above circumstances, an object of the present invention is to provide a light source device and a cleaning method capable of suppressing a change in pressure on the light source side caused by a change in pressure on the light source entrance side. [Means for solving the problem]

[0013] In order to achieve the above object, a light source device according to one aspect of the present invention includes a first vacuum chamber, a light source unit, and a debris reduction device. The light source unit generates plasma that serves as a light source in the first vacuum chamber. The debris mitigation device is a debris mitigation device that reduces debris dispersed from the plasma, and forms a vacuum path that connects the first vacuum chamber and a second vacuum chamber into which radiation emitted from the plasma is introduced and allows the radiation to pass through, and generates a high-pressure region whose pressure is higher than the pressure of the first vacuum chamber and the pressure of the second vacuum chamber so as to interrupt the vacuum path.

[0014] In this light source device, the debris reduction device forms a vacuum path connecting a first vacuum chamber that generates plasma and a second vacuum chamber into which radiation from the plasma is introduced. Furthermore, a high-pressure region with a pressure higher than the pressure of the first vacuum chamber and the pressure of the second vacuum chamber is formed so as to block the vacuum path. This allows, for example, pressure changes in the second vacuum chamber to be absorbed by the high-pressure region. This makes it possible to suppress pressure changes on the light source side caused by pressure changes on the radiation introduction side.

[0015] The debris mitigation apparatus may include a conductance reducer that reduces the conductance of the vacuum path between the high pressure region and the second vacuum chamber. This makes it possible to maintain a high pressure region without being affected by the pressure of the second vacuum chamber, for example, and makes it possible to sufficiently absorb changes in pressure on the introduction side.

[0016] The conductance reducing portion may be a fixed foil trap having a plurality of foils disposed in the vacuum path and a fixing member that fixes the plurality of foils. This allows for debris reduction with fixed foil traps.

[0017] The debris mitigation apparatus may include a tubular member disposed between the high pressure region and the first vacuum chamber, the tubular member having a cross section intersecting with a path direction of the vacuum path larger than that of the high pressure region. This makes it possible, for example, to reduce the pressure in the high pressure region over a short distance and maintain it at the pressure of the first vacuum chamber.

[0018] The debris mitigation device may include a rotary foil trap having a plurality of foils and a rotary member that radially supports the plurality of foils, in which case the cylindrical member may be a rotary foil trap cover that surrounds the rotary foil trap. This allows for debris reduction with a rotating foil trap.

[0019] The debris mitigation apparatus may be configured to leave the pressure in the first vacuum chamber substantially unchanged when the pressure in the second vacuum chamber varies at least within a range equal to or less than the pressure of the high pressure region. This makes it possible to sufficiently maintain the pressure in the first vacuum chamber even if the pressure in the second vacuum chamber changes, for example.

[0020] The pressure in the high pressure region may be six times or more the pressure in the first vacuum chamber. This makes it possible to reliably absorb, for example, pressure changes on the introduction side.

[0021] The light source device may further include an inlet for introducing a buffer gas that changes the pressure in the second vacuum chamber, and a pressure adjustment mechanism that adjusts the pressure in the second vacuum chamber. This makes it possible to easily adjust the pressure in, for example, the second vacuum chamber, and thus realize various operation modes.

[0022] The high pressure region may be a region into which the buffer gas is introduced. In this case, the inlet may include a first inlet leading to the high pressure region. This makes it possible, for example, to change the pressure in the second vacuum chamber while realizing a high pressure region.

[0023] The light source device may further include the second vacuum chamber. In this case, the introduction port may include a second introduction port provided in the second vacuum chamber. This makes it possible, for example, to easily change the pressure in the second vacuum chamber.

[0024] The buffer gas may be an ionized gas that is ionized by the radiation. In this case, the light source device may be capable of a normal operation and a cleaning operation using the ionized gas. This makes it possible to clean optical elements and the like provided in the second vacuum chamber while stably generating radiation, for example.

[0025] The cleaning operation may be an operation of introducing the ionized gas into a second vacuum chamber maintained at a first pressure which is the pressure during normal operation, increasing the pressure of the second vacuum chamber to a second pressure higher than the first pressure, and performing sputtering on a target placed in the second vacuum chamber using the ionized gas ionized by the synchrotron radiation while maintaining the second pressure. This makes it possible to sputter, for example, an optical element or the like disposed in the second vacuum chamber at a desired rate.

[0026] The second pressure may be 6 Pa or more. This makes it possible to perform sputtering at a desired rate, for example.

[0027] The pressure of the first vacuum chamber during normal operation may be set to a third pressure at which the radiation is stable. In this case, the second pressure may be three times or more the third pressure. This allows, for example, sputtering to be carried out at a relatively high rate.

[0028] The ionizable gas may be a noble gas. This makes it possible to prevent, for example, the members inside each chamber from being corroded by the ionized gas, and also makes it possible to easily treat the gas exhausted from each chamber.

[0029] The light source device may further include the second vacuum chamber and a light intensity monitor provided in the second vacuum chamber and configured to detect the intensity of the emitted light. In this case, the normal operation and the cleaning operation may be switched and executed based on a detection result of the light intensity monitor. This makes it possible to perform cleaning in response to contamination of, for example, optical elements.

[0030] The pressure adjustment mechanism may be at least one of a flow rate adjustment valve that adjusts the flow rate of the buffer gas introduced from the inlet, or an exhaust rate adjustment valve that adjusts the exhaust rate of the second vacuum chamber. This makes it possible to precisely adjust the pressure in, for example, the second vacuum chamber.

[0031] The radiation may be EUV light. This makes it possible to realize, for example, an EUV light source device that is easy to maintain and has a stable light output.

[0032] The light source unit may include a pair of rotating electrodes arranged within the first vacuum chamber on either side of a discharge region, a raw material supply unit that supplies plasma raw material to the pair of rotating electrodes, an energy beam injection unit that injects an energy beam that vaporizes the plasma raw material onto a portion of one of the pair of rotating electrodes facing the discharge region, and a voltage source that applies a voltage to the pair of rotating electrodes to plasmaize the plasma raw material vaporized by the energy beam.

[0033] The light source unit may include a rotating body disposed in the first vacuum chamber, a raw material supply unit that supplies plasma raw material to the rotating body, and an energy beam incident unit that incidents an energy beam to convert the plasma raw material supplied to the rotating body into plasma.

[0034] A cleaning method according to one aspect of the present invention is a cleaning method performed using the light source device, and includes the following steps. a pressure increasing step of introducing an ionized gas that is ionized by the synchrotron radiation into a second vacuum chamber maintained at a first pressure that is a pressure during normal operation while the plasma is being generated, and increasing the pressure of the second vacuum chamber to a second pressure that is higher than the first pressure. a sputtering step of performing sputtering on a target placed in the second vacuum chamber with the ionized gas ionized by the synchrotron radiation while maintaining the second pressure.

[0035] This makes it possible to suppress changes in pressure on the light source side due to changes in pressure on the input side of the synchrotron radiation, and enables stable generation of synchrotron radiation even when sputtering is performed by introducing ionized gas. This makes it possible to easily clean optical elements and the like installed in the second vacuum chamber.

[0036] The light source device may further include the second vacuum chamber and a light quantity monitor provided in the second vacuum chamber for detecting the quantity of the emitted light. In this case, the pressure increasing step and the sputtering step may be executed when the quantity of light detected by the light quantity monitor becomes lower than a first threshold. The light source device may further include a pressure decreasing step of decreasing the pressure of the second vacuum chamber to the first pressure when the quantity of light detected by the light quantity monitor becomes higher than a second threshold equal to or higher than the first threshold. This makes it possible to perform cleaning in response to contamination of, for example, optical elements.

[0037] The sputtering step may include a step of changing an amount of the synchrotron radiation from an amount of the synchrotron radiation during the normal operation while maintaining the second pressure. This allows fine control of, for example, the sputtering rate. Effect of the Invention

[0038] As described above, according to the present invention, the change in pressure on the light source side caused by the change in pressure on the radiation light introduction side can be suppressed. Note that the effects described here are not necessarily limited to those described herein, and may be any of the effects described in this disclosure. [Brief description of the drawings]

[0039] [Figure 1] 1 is a schematic diagram showing a configuration example of a light source device according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic diagram showing a configuration example of a debris reduction device mounted on a light source device. [Diagram 3] FIG. 2 is a schematic cross-sectional view showing a configuration example of a rotary foil trap. [Figure 4] FIG. 2 is a schematic front view showing a configuration example of a rotary foil trap. [Diagram 5] FIG. 2 is a schematic cross-sectional view showing a configuration example of a rotary foil trap cover. [Figure 6] FIG. 2 is a schematic front view showing a configuration example of a rotary foil trap cover. [Figure 7] FIG. 2 is a schematic cross-sectional view showing a configuration example of a fixed foil trap. [Figure 8] FIG. 2 is a schematic front view showing a configuration example of a fixed foil trap. [Figure 9] FIG. 2 is a schematic cross-sectional view showing a configuration example of a fixed foil trap cover. [Figure 10] FIG. 2 is a schematic front view showing a configuration example of a fixed foil trap cover. [Figure 11] 1 is a schematic cross-sectional view showing an example of the configuration of a debris reduction device. [Figure 12]11 is a graph showing a simulation result of the pressure inside the light source device. [Figure 13] 4 is a graph showing the relationship between the pressure in the first vacuum chamber and the pressure in the second vacuum chamber. [Figure 14] FIG. 1 is a schematic diagram showing an example of the arrangement of samples used in a sputtering experiment. [Figure 15] 1 is a graph showing the relationship between sputtering rate and pressure. [Figure 16] 1 is a graph showing the relationship between sputter rate, pressure, and sample position. [Figure 17] 1 is a graph showing the relationship between the sputtering rate and the emission frequency of plasma. [Figure 18] 4 is a flowchart showing an example of the operation of the light source device. [Figure 19] FIG. 2 is a schematic diagram illustrating a sputtering region where sputtering occurs. [Figure 20] FIG. 1 is a schematic diagram showing an example of the configuration of an optical system using a light shielding plate. [Figure 21] FIG. 13 is a schematic diagram showing another example of the configuration of an optical system using a light-shielding plate. [Figure 22] FIG. 2 is a schematic diagram showing a configuration example of a light source unit of the LPP method. [Figure 23] FIG. 13 is a schematic diagram showing another example of the configuration of the light source unit of the LPP method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0041] [Light source overview] Fig. 1 is a schematic diagram showing a configuration example of a light source device according to an embodiment of the present invention. Fig. 1 is a schematic cross-section of the light source device 100 cut horizontally at a position of a predetermined height from the installation surface, as viewed from the positive side of the Z direction. In the following description, the X direction is the left-right direction (the positive side of the X axis is the right side, and the negative side is the left side), the Y direction is the depth direction (the positive side of the Y axis is the front side, and the negative side is the back side), and the Z direction is the up-down direction (the positive side of the Z axis is the top side, and the negative side is the bottom side). Of course, the application of this technology is not limited to the direction in which the light source device 100 is used.

[0042] The light source device 100 is an EUV light source device of the LDP type, and emits extreme ultraviolet light (EUV light 1). The wavelength of the EUV light 1 is, for example, 13.5 nm.

[0043] Light source device 100 can be used, for example, as a light source device for a lithography apparatus in semiconductor device manufacturing, or as a light source device for an inspection apparatus for a mask used in lithography. For example, when light source device 100 is used as a light source device for a mask inspection apparatus, a part of EUV light 1 emitted from plasma P is extracted and guided to a mask inspection apparatus. Then, the mask inspection apparatus performs mask blank inspection or pattern inspection using EUV light 1 emitted from light source device 100 as inspection light.

[0044] In this embodiment, the EUV light 1 is an example of radiation emitted from plasma. The type of radiation is not limited. The present invention is also applicable to cases where light in the soft X-ray region other than the EUV light 1, or hard X-rays with higher energy, etc. are emitted.

[0045] The light source device 100 has a first vacuum chamber 10, a second vacuum chamber 20, a light source unit 30, and a debris reduction device 40. The first vacuum chamber 10 is a vacuum chamber in which the light source unit 30 generates plasma P. The second vacuum chamber 20 is a vacuum chamber into which the EUV light 1 emitted from the plasma P is introduced. The debris reduction device 40 is a device that reduces debris dissipated from the plasma P between the first vacuum chamber 10 and the second vacuum chamber 20.

[0046] [First vacuum chamber] The first vacuum chamber 10 is a housing that houses various mechanisms of the light source unit 30. The first vacuum chamber 10 has, for example, a rectangular parallelepiped or cylindrical shape, and is made of a rigid body such as metal. Of course, the specific shape, material, etc. of the first vacuum chamber 10 are not limited.

[0047] The inside of the first vacuum chamber 10 is maintained at a reduced pressure atmosphere below a predetermined pressure by a vacuum pump (not shown). Feedthroughs FA and FB are arranged on the left side wall 10a of the first vacuum chamber 10. The feedthroughs FA and FB are sealing members that enable the insertion of electric wires and the like into the first vacuum chamber 10 while maintaining the reduced pressure atmosphere inside the first vacuum chamber 10.

[0048] A transparent window 11 is disposed on the side wall 10b on the front side of the first vacuum chamber 10. The transparent window 11 is made of a material that is transparent to the laser beam LB described later. The specific configuration of the transparent window 11, such as its material and shape, is not limited. A through hole 12 for connecting to the second vacuum chamber 20 is provided on the right side wall 10c of the first vacuum chamber 10. In this embodiment, a debris reduction device 40 is disposed inside the first vacuum chamber 10 so as to cover the through hole 12.

[0049] [Second vacuum chamber] The second vacuum chamber 20 is a housing that houses an optical element 21 into which the EUV light 1 is incident, for example. The optical element 21 is, for example, a condenser mirror for condensing the EUV light 1, a reflecting mirror for bending the optical path of the EUV light 1, or the like. In addition, for example, the second vacuum chamber 20 may be configured as a container that connects a utilization device (such as a mask inspection device or a lithography device) that utilizes the EUV light 1 to a light source device. The second vacuum chamber 20 has, for example, a rectangular parallelepiped or cylindrical shape, and is configured of a rigid body such as metal. Of course, the specific shape, material, etc. of the second vacuum chamber 20 are not limited.

[0050] The inside of the second vacuum chamber 20 is maintained at a reduced pressure atmosphere below a predetermined pressure by a vacuum pump (not shown). A through hole 22 communicating with the through hole 12 of the first vacuum chamber 10 is arranged in the left side wall 20a of the second vacuum chamber 20. In addition, for example, an exit port (not shown) for emitting the EUV light 1 that has passed through an optical element 21 and the like are appropriately provided in the second vacuum chamber 20.

[0051] It should be noted that the light source device 100 does not necessarily have to include the second vacuum chamber 20. For example, the second vacuum chamber 20 may be provided on the utilization device side. In this case, a vacuum chamber or the like provided on the utilization device for introducing the EUV light 1 is used as the second vacuum chamber.

[0052] [Light source section] The light source unit 30 generates plasma P, which serves as a light source, in the first vacuum chamber 10. The light source unit 30 has a discharge module 31, a control unit 32, a pulsed power supply unit 33, a laser source 34, a condenser lens 35, and a movable mirror 36. Of these, the control unit 32, the pulsed power supply unit 33, the laser source 34, the condenser lens 35, and the movable mirror 36 are provided outside the first vacuum chamber 10.

[0053] The discharge module 31 is a module that performs discharge to generate plasma P in the first vacuum chamber 10. The discharge module 31 has containers CA and CB, discharge electrodes EA and EB, and motors MA and MB. Of these, the containers CA and CB and the discharge electrodes EA and EB are disposed inside the first vacuum chamber 10.

[0054] The containers CA and CB are vessels for storing plasma raw materials. In this embodiment, the containers CA and CB are made of a conductive material. The plasma raw material SA is stored in the container CA. The plasma raw material SB is stored in the container CB. The plasma raw materials SA and SB are heated liquid phase raw materials. In this embodiment, tin (Sn) is used as the plasma raw materials SA and SB. Alternatively, other raw materials capable of generating plasma, such as lithium (Li), may be used.

[0055] The discharge electrodes EA and EB have a disk shape. The discharge electrodes EA and EB are made of a high melting point metal such as molybdenum (Mo), tungsten (W), or tantalum (Ta). The specific material of the discharge electrodes EA and EB is not limited.

[0056] For example, the discharge electrode EA is used as a cathode, and the discharge electrode EB is used as an anode. The discharge electrodes EA and EB are disposed apart from each other. The discharge electrodes EA and EB are also disposed such that parts of the peripheries of the discharge electrodes EA and EB are close to each other. The gap at the position where the peripheries of the discharge electrodes EA and EB are closest to each other becomes the discharge region D formed by the discharge electrodes EA and EB.

[0057] Furthermore, the discharge electrode EA is positioned so that the lower portion of the discharge electrode EA is immersed in the plasma raw material SA stored in the container CA. Similarly, the discharge electrode EB is positioned so that the lower portion of the discharge electrode EA is immersed in the plasma raw material SB.

[0058] The motor MA rotates the discharge electrode EA. The motor MA has a rotation axis JA. A base portion of the motor MA is disposed outside the first vacuum chamber 10 on the left side, and the rotation axis JA connected to the base portion extends from the outside to the inside of the first vacuum chamber 10. The end of the rotation axis JA on the inside side of the first vacuum chamber 10 is connected to the center of the discharge electrode EA (the center of the circular surface).

[0059] The gap between the rotating shaft JA and the wall of the first vacuum chamber 10 is sealed with a seal member PA. For example, a mechanical seal is used as the seal member PA. The seal member PA supports the rotating shaft JA rotatably while maintaining the reduced pressure atmosphere in the first vacuum chamber 10.

[0060] Similarly, the motor MB has a rotating shaft JB, which is connected to the center of the discharge electrode EB. The gap between the rotating shaft JB and the wall of the first vacuum chamber 10 is sealed by a seal member PB.

[0061] The discharge electrodes EA and EB are arranged so that their axes (extension directions of the rotation shafts) are not parallel. Specifically, as shown in Fig. 1, the discharge electrode EA is arranged with its front side (lower side in Fig. 1) tilted to the right and its rear side (upper side in Fig. 1) tilted to the left. On the other hand, the discharge electrode EB is arranged with its front side tilted to the left and its rear side tilted to the right. The distance between the rotation shafts JA and JB in the depth direction (up and down direction in Fig. 1, Z direction) is also narrower on the side of the motors MA and MB and wider on the side of the discharge electrodes EA and EB. Furthermore, the discharge electrode EB, motor MB, and rotation shaft JB are arranged slightly to the left of the discharge electrode EA, motor MA, and rotation shaft JA.

[0062] The control unit 32 controls the operation of each unit of the light source unit 30. For example, the control unit 32 controls the rotational driving of the motors MA and MB, and the discharge electrodes EA and EB rotate at a predetermined rotation speed. The control unit 32 also controls the operation of the pulsed power supply unit 33 and the timing of laser beam irradiation by the laser source 34.

[0063] The control unit 32 is realized by a controller having hardware necessary for configuring a computer, such as a processor such as a CPU, a GPU, or a DSP, a memory such as a ROM or a RAM, a storage device such as a HDD, etc. Specifically, the control unit 32 is realized as a functional block by the CPU of the controller executing a program related to the present technology (e.g., an application program).

[0064] The pulsed power supply unit 33 supplies pulsed power to the discharge electrodes EA and EB, thereby generating a discharge in the discharge region D. Power feed lines QA and QB are connected to the pulsed power supply unit 33. The power feed line QA is inserted into the first vacuum chamber 10 via a feedthrough FA and is connected to a container CA. The power feed line QB is inserted into the first vacuum chamber 10 via a feedthrough FB and is connected to a container CB.

[0065] The laser source 34 emits an energy beam that vaporizes the plasma raw materials SA and SB. The laser source 34 is disposed outside the first vacuum chamber 10. For example, a Nd:YVO4 (Neodymium-doped Yttrium Orthovanadate) laser device is used as the laser source 34. In this case, the laser source 34 emits a laser beam LB in the infrared region with a wavelength of 1064 nm. Of course, as long as it is possible to vaporize the plasma raw materials SA and SB, the specific configuration of the laser source 34, such as the type of device of the laser source 34 and the wavelength of the irradiated laser beam LB, is not limited.

[0066] The condenser lens 35 is disposed on the optical path of the laser beam LB outside the first vacuum chamber 10. The laser beam LB emitted by the laser source 34 is incident on the condenser lens 35, whereby the spot diameter of the laser beam LB is adjusted.

[0067] The movable mirror 36 is disposed on the optical path of the laser beam LB outside the first vacuum chamber 10. Here, the movable mirror 36 is disposed on the optical path of the laser beam LB, behind the condenser lens 35. Therefore, the laser beam LB that has passed through the condenser lens 35 is incident on the movable mirror.

[0068] The laser beam LB incident on the movable mirror 36 is reflected by the movable mirror 36 and passes through the transparent window 11 of the first vacuum chamber 10. The laser beam LB then reaches the periphery of the discharge electrode EA near the discharge region D inside the first vacuum chamber 10. Note that by changing the attitude of the movable mirror 36, it is possible to adjust the irradiation position of the laser beam LB with respect to the discharge electrode EA.

[0069] Thus, in the light source section 30, the discharge electrodes EA and EB are arranged in the first vacuum chamber 10 on either side of the discharge region D. Furthermore, plasma raw materials SA and SB are supplied to the discharge electrodes EA and EB from containers CA and CB, respectively. In this embodiment, the discharge electrodes EA and EB correspond to a pair of rotating electrodes, and the containers CA and CB correspond to a raw material supply section.

[0070] Furthermore, a laser beam LB is incident on a portion of one of the discharge electrodes EA and EB, that faces the discharge region D, by means of the laser source 34, the condenser lens 35, and the movable mirror 36. As a result, the liquid-phase plasma raw material SA transported to the vicinity of the discharge region D as the discharge electrode EA rotates becomes gas-phase plasma raw material SA. Similarly, the plasma raw material SB transported by the discharge electrode EB also becomes gas-phase plasma raw material SB in the discharge region D. In this embodiment, an energy beam incident portion is realized by using the laser source 34, the condenser lens 35, and the movable mirror 36. Furthermore, the laser beam LB corresponds to an energy beam that vaporizes the plasma raw material.

[0071] Furthermore, a voltage (pulsed power) is applied to the discharge electrodes EA and EB by the pulsed power supply unit 33 to convert the plasma raw material vaporized by the laser beam LB into plasma. This generates a discharge in the discharge region D between the discharge electrodes EA and EB. This discharge heats and excites the gaseous plasma raw materials SA and SB present in the discharge region D with the current, generating a plasma P. In this embodiment, the pulsed power supply unit 33 corresponds to a voltage source.

[0072] EUV light 1 is emitted from the plasma P generated in the discharge region D. A portion of the emitted EUV light 1 (light directed to the right) passes through a debris mitigation device 40, which will be described later, and is introduced into the second vacuum chamber 20. In Fig. 1, an example of the optical path of the EUV light 1 is shown by a dashed arrow. The plasma P corresponds to one embodiment of the light source according to the present technology.

[0073] In this embodiment, the inside of the first vacuum chamber 10 is maintained at a reduced pressure atmosphere below a predetermined pressure. This makes it possible to satisfactorily generate a discharge for heating and exciting the plasma raw materials SA and SB. It also makes it possible to suppress attenuation of the EUV light 1.

[0074] Furthermore, debris is dispersed from the plasma P at high speed in various directions together with the EUV light 1. The debris includes tin particles which are the plasma raw materials SA and SB. The debris also includes material particles of the discharge electrodes EA and EB which are sputtered as the plasma P is generated. Specifically, the debris includes ions, neutral atoms and electrons which move at high speed. This debris gains large kinetic energy through the contraction and expansion processes of the plasma P. Part of the debris is dispersed towards the debris mitigation device 40.

[0075] [Debris Reduction Device] Fig. 2 is a schematic diagram showing a configuration example of the debris mitigation device 40 mounted on the light source device 100. Fig. 2 shows a cross section of the light source device 100 cut along the XZ plane as viewed from the front side. Note that Fig. 2 omits the configuration of the light source unit 30 other than the discharge module 31. The configuration of the discharge module 31 is also omitted in the illustration.

[0076] The debris mitigation device 40 is a device that reduces debris dispersed from the plasma P. The debris mitigation device 40 is disposed so as to overlap with the optical path of the EUV light 1 traveling from the plasma P generated in the first vacuum chamber 10 toward the second vacuum chamber 20. The debris mitigation device 40 also includes a mechanism for capturing debris on the optical path of the EUV light. That is, the debris mitigation device 40 is configured to allow the EUV light 1 from the plasma P to pass through while capturing debris from the plasma P. The debris mitigation device 40 is sometimes called a DMT (Debris Mitigation Tool).

[0077] In this embodiment, a foil trap (a rotating foil trap 43 and a fixed foil trap 45, described later) is used as a mechanism for trapping debris. A foil trap is a debris trap that uses multiple foils to trap debris from the plasma P. In a foil trap, multiple foils are arranged at a distance from each other. This allows the EUV light 1 to pass between the foils. By using a foil trap, it is possible to trap debris ranging from large mm-sized debris to small atomic-sized debris.

[0078] Furthermore, the debris reduction device 40 forms a vacuum path 13 that connects the first vacuum chamber 10 and the second vacuum chamber 20 and passes the EUV light 1. Here, the vacuum path 13 refers to a structure that connects, for example, two independent vacuum chambers without leaks to form an exhaust path. For example, when only one of two vacuum chambers connected by the vacuum path 13 is evacuated, the other vacuum chamber is always evacuated via the vacuum path 13 (exhaust path).

[0079] Such a vacuum path 13 is formed inside the debris mitigation device 40. The internal space of the first vacuum chamber 10 and the internal space of the second vacuum chamber 20 communicate with each other without leaking through this vacuum path 13. The vacuum path 13 also functions as a passage for passing the EUV light 1. For this reason, the vacuum path 13 includes at least a straight path that allows the EUV light 1 to pass without being blocked. Here, the direction of the straight path through which the EUV light 1 passes is referred to as the path direction of the vacuum path 13. In FIG. 2, the path direction of the vacuum path 13 is diagrammatically illustrated using a dotted arrow.

[0080] Furthermore, the debris reduction device 40 generates a high pressure region 14 where the pressure is higher than the pressure in the first vacuum chamber 10 and the pressure in the second vacuum chamber 20 so as to block the vacuum path 13. Here, the region that blocks the vacuum path 13 means, for example, a region that completely covers the cross section of the vacuum path 13, intersecting the path direction of the vacuum path 13. Therefore, in order to pass through the vacuum path 13, it is necessary to pass through the high pressure region 14. The debris reduction device 40 is configured so as to be able to generate such a high pressure region 14 in the middle of the vacuum path 13. In FIG. 2, the part that becomes the high pressure region 14 is diagrammatically illustrated by a hatched region using dots.

[0081] As described above, the high pressure region 14 is a region capable of maintaining an internal pressure higher than the pressure in either the first vacuum chamber 10 or the second vacuum chamber 20. That is, in the high pressure region 14, the pressure (density) of the buffer gas 2 (ambient gas) can be made higher than the pressure in each vacuum chamber. The debris mitigation device 40 is basically used in a state where the high pressure region 14 has been generated.

[0082] For example, suppose the pressure in one of the vacuum chambers changes. In this case, the presence of the high pressure region 14 absorbs the pressure change. This makes it difficult for the pressure change in one vacuum chamber to be transmitted to the other vacuum chamber. In other words, the high pressure region 14 can be said to be a region that separates the pressure of the first vacuum chamber 10 from the pressure of the second vacuum chamber 20.

[0083] As a configuration for forming the high pressure region 14, the debris reduction device 40 is provided with a cylindrical member 41 and a conductance reduction section 42.

[0084] The cylindrical member 41 is a cylindrical member that surrounds the space that becomes the vacuum path 13, and is provided between the high pressure region 14 and the first vacuum chamber 10. The cylindrical member 41 has an opening (exit side opening KO of the rotary foil trap cover 44) connected to the high pressure region 14, and an opening (incident side opening KI of the rotary foil trap cover 44) connected to the first vacuum chamber 10, and forms the vacuum path 13.

[0085] The cylindrical member 41 is a member whose cross section intersecting the path direction of the vacuum path 13 is larger than that of the high pressure region 14. That is, the cylindrical member 41 is a member that expands the width of the vacuum path 13 formed by the high pressure region 14 on the first vacuum chamber 10 side. With this configuration, the buffer gas 2 flowing out from the high pressure region 14 to the cylindrical member 41 side is diffused into a wide space while being caught in a rotary foil trap 43 described later, and is exhausted by a vacuum pump (first vacuum pump 54) that exhausts the first vacuum chamber 10. For this reason, it is possible to reduce the pressure of the high pressure region 14, for example, in a short distance. That is, the pressure of the vacuum path 13 drops suddenly while passing through the cylindrical member 41. As a result, the pressure of the first vacuum chamber 10 is maintained almost without being affected by the pressure of the high pressure region 14.

[0086] The conductance reduction unit 42 is a member that reduces the conductance of the vacuum path 13 between the high pressure region 14 and the second vacuum chamber 20. The conductance reduction unit 42 has a cylindrical structure that forms the vacuum path 13, and has an opening (the entrance end of the fixed foil trap 45) connected to the high pressure region 14, and an opening (the exit end of the fixed foil trap 45) connected to the second vacuum chamber 20. A member that reduces the conductance of the vacuum compared to the other vacuum paths 13 is disposed between these two openings.

[0087] The vacuum conductance is a parameter that indicates the ease of flow of the buffer gas 2, and corresponds to, for example, the inverse of the exhaust resistance. The lower the conductance, the higher the exhaust resistance, and the more difficult it is for the buffer gas 2 to flow. Therefore, it can be said that the conductance reduction section 42 is a member that makes it difficult for the buffer gas 2 to flow. By providing the conductance reduction section 42, it becomes difficult for the buffer gas 2 to flow between the second vacuum chamber 20 and the high pressure region 14. As a result, it becomes possible to maintain the high pressure region 14 without being affected by the pressure of the second vacuum chamber 20, and it becomes possible to sufficiently absorb changes in pressure on the introduction side.

[0088] Here, the configuration for capturing the debris will be described. As shown in Fig. 2, the debris mitigation device 40 has a rotary foil trap 43, a rotary foil trap cover 44, a fixed foil trap 45, and a fixed foil trap cover 46.

[0089] The rotating foil trap 43 is a foil trap in which multiple foils are rotated to actively collide with debris. The rotating foil trap 43 is also called an RFT (Rotating Foil Trap). The rotating foil trap cover 44 is a cylindrical cover configured to cover the outer periphery of the rotating foil trap 43. The rotating foil trap 43 and the rotating foil trap cover 44 are disposed on the first vacuum chamber 10 side.

[0090] The fixed foil trap 45 is a foil trap in which the positions of multiple foils are fixed. The fixed foil trap 45 is also called an SFT (Static Foil Trap). The fixed foil trap cover 46 is a cover that covers the fixed foil trap 45. The fixed foil trap cover 46 also functions as a member that connects the fixed foil trap 45 to the rotary foil trap cover 44. Note that the rotary foil trap cover 44 and the fixed foil trap cover 46 do not necessarily need to be completely connected, and for example, there may be a small gap as long as the pressure of the high pressure region 14 can be maintained. The fixed foil trap 45 and the fixed foil trap cover 46 are disposed on the second vacuum chamber 20 side.

[0091] The above-mentioned vacuum path 13, cylindrical member 41, and conductance reduction unit 42 are realized by utilizing these configurations for capturing debris. In this embodiment, a hollow area formed by connecting the rotary foil trap cover 44, the fixed foil trap cover 46, and the fixed foil trap 45 becomes the vacuum path 13. The rotary foil trap cover 44 functions as the cylindrical member 41. The fixed foil trap 45 functions as the conductance reduction unit 42. Therefore, the high pressure area 14 is formed in the space from the rotary foil trap cover 44 to the fixed foil trap 45. The specific configuration of each foil trap etc. will be described in detail later.

[0092] [Buffer gas inlet] The light source device 100 is provided with an inlet 47 for introducing the buffer gas 2. The buffer gas 2 functions as a gas that changes the pressure in the second vacuum chamber 20. Only one inlet 47 for the buffer gas 2 may be provided, or multiple inlets 47 may be provided. A pipe through which the buffer gas 2 passes is connected to the inlet 47, and a flow rate adjustment valve for adjusting the flow rate of the buffer gas 2 is attached to the pipe.

[0093] In this embodiment, the high pressure region 14 is a region in the debris mitigation device 40 where the buffer gas 2 is introduced, and the debris mitigation device 40 is provided with an inlet 47 leading to the high pressure region 14. This allows the buffer gas 2 to be directly supplied to the high pressure region 14, making it possible to easily maintain the pressure in the high pressure region 14 at a high level. This inlet 47 is provided, for example, in the fixed foil trap cover 46. In FIG. 2, the inlet 47 leading to the high pressure region 14 is diagrammatically illustrated by a dotted circle. In this embodiment, the inlet 47 leading to the high pressure region 14 corresponds to the first inlet.

[0094] Also, a buffer gas inlet (not shown) may be provided in the second vacuum chamber 20. In this case, the buffer gas 2 is directly supplied to the second vacuum chamber 20, so that it is possible to easily change the pressure in the second vacuum chamber 20. In this embodiment, the inlet provided in the second vacuum chamber 20 corresponds to the second inlet.

[0095] Thus, the light source device 100 has a structure in which the first vacuum chamber 10 in which the EUV light 1 (plasma P) is generated and the second vacuum chamber 20 in which optical elements and the like for utilizing the EUV light 1 are housed are connected via a vacuum path 13 formed by the debris mitigation device 40. Also, an inlet 47 for a buffer gas 2 is provided in the debris mitigation device 40 (high pressure region 14) or downstream of the debris mitigation device 40 (on the second vacuum chamber 20 side).

[0096] A rare gas is used as the buffer gas 2. Typically, the buffer gas 2 is argon gas. Argon gas is an inert gas that is unlikely to form a compound with other atoms. Therefore, unlike active gases such as hydrogen gas and halogen gas, there is no risk of argon gas corroding metals and the like in the chamber. In addition, since argon gas can be exhausted without any process such as inactivation, it is possible to reduce the size and cost of the exhaust system compared to the case of exhausting an active gas.

[0097] Furthermore, it is known that light in the EUV region excites and ionizes argon atoms (Ar). Therefore, it is possible to generate argon plasma by irradiating the EUV light 1. In this manner, the argon gas (buffer gas 2) is an ionized gas that is ionized by the EUV light 1. By utilizing this phenomenon, the light source device 100 performs a cleaning operation, which will be described later.

[0098] Although argon atoms have some absorption for the 13.5 nm wavelength, the absorption is one order of magnitude lower than that for light of 30-80 nm. Therefore, the attenuation of the actinic wavelength of 13.5 nm is small, and it is possible to ensure a sufficient amount of light even when argon gas is used as the buffer gas 2.

[0099] [Partition] As shown in FIG. 2, in the first vacuum chamber 10, a first partition plate 16 and a second partition plate 17 are provided between the debris mitigation device 40 and the discharge module 31.

[0100] The first partition plate 16 is a plate-shaped member having a larger planar size than the debris mitigation device 40 (rotary foil trap cover 44), and is arranged to cover the side of the debris mitigation device 40 facing the plasma P. The first partition plate 16 has an opening 16a to which the second partition plate 17 is attached. The first partition plate 16 restricts, for example, vapor of a liquid-phase plasma raw material (tin vapor in this case) from leaking into the space on the debris mitigation device 40 side, the second vacuum chamber 20, etc.

[0101] The second partition plate 17 is a plate-shaped member that covers the opening 16a provided in the first partition plate 16, and is fixed to the side of the first partition plate 16 facing the plasma P. The second partition plate 17 has an opening 17a through which the EUV light 1 to be introduced into the second vacuum chamber 20 passes, and an opening 17b through which the EUV light 1 to be introduced into a predetermined measuring instrument (first light intensity monitor 25a) passes. The second partition plate 17 reduces the thermal load applied to the debris mitigation device 40 from the plasma P generated by discharge, and limits the amount of debris heading toward the debris mitigation device 40.

[0102] [Exhaust system] As shown in FIG. 2, the light source device 100 has a first vacuum valve 50 and a first vacuum gauge 51 connected to the first vacuum chamber 10, and a second vacuum valve 52 and a second vacuum gauge 53 connected to the second vacuum chamber 20.

[0103] The first vacuum chamber 10 is provided with an exhaust hole 18 and a measurement hole 19. The first vacuum valve 50 is connected to the exhaust hole 18 and is a valve that connects the first vacuum chamber 10 to a first vacuum pump 54. The first vacuum gauge 51 is connected to the measurement hole 19 and detects the pressure of the first vacuum chamber 10. The second vacuum chamber 20 is provided with an exhaust hole 28 and a measurement hole 29. The second vacuum valve 52 is connected to the exhaust hole 28 and is a valve that connects the second vacuum chamber 20 to a second vacuum pump 55. The second vacuum gauge 53 is connected to the measurement hole 29 and detects the pressure of the second vacuum chamber 20.

[0104] In this way, in the light source device 100, the first vacuum chamber 10 and the second vacuum chamber 20 are evacuated separately. Also, the high pressure region 14 described above is formed in the vacuum path 13 connecting the vacuum chambers, restricting the flow of the buffer gas. As a result, although the first vacuum chamber 10 and the second vacuum chamber 20 are connected by the vacuum path 13, differential evacuation is possible, in which the internal spaces of each chamber are evacuated independently.

[0105] In this embodiment, mainly the pressure in the second vacuum chamber 20 is adjusted. For this reason, the light source device 100 is provided with a pressure adjustment mechanism that adjusts the pressure in the second vacuum chamber 20. The pressure adjustment mechanism is a mechanism that adjusts, for example, the amount of buffer gas 2 flowing out of the second vacuum chamber 20 or the amount of buffer gas 2 flowing into the second vacuum chamber 20.

[0106] For example, a flow rate adjustment valve (not shown) that adjusts the flow rate of the buffer gas 2 introduced from the inlet 47 is used as the pressure adjustment mechanism. In this case, for example, by increasing the flow rate of the buffer gas 2, the flow rate of the buffer gas 2 flowing into the second vacuum chamber 20 increases, and it is possible to increase the pressure of the second vacuum chamber 20.

[0107] Also, for example, the second vacuum valve 52 that adjusts the exhaust amount of the second vacuum chamber 20 is used as the pressure adjustment mechanism. In this case, for example, by reducing the exhaust amount, the flow rate of the buffer gas 2 flowing out from the second vacuum chamber 20 is reduced, and as a result, it is possible to increase the pressure of the second vacuum chamber 20. In this embodiment, the second vacuum valve 52 corresponds to an exhaust amount adjustment valve.

[0108] As the pressure adjustment mechanism, both the buffer gas flow rate adjustment valve and the second vacuum valve 52 may be used, or either one of them may be used. Also, any mechanism other than the above may be used as long as it is a mechanism capable of adjusting the pressure of the second vacuum chamber 20. By using the pressure adjustment mechanism, for example, it becomes possible to easily adjust the pressure of the second vacuum chamber, and various operation modes can be realized.

[0109] [Light level monitor] The light source device 100 has a light intensity monitor that detects the amount of EUV light 1. Here, a first light intensity monitor 25a and a second light intensity monitor 25b are provided. The first light intensity monitor 25a is connected to the right side wall 10c of the first vacuum chamber 10, and detects the EUV light 1 that has passed through the rotary foil trap 43. Therefore, the first light intensity monitor 25a functions as a sensor that detects the amount of EUV light 1 from the plasma P, i.e., the emission intensity of the plasma P.

[0110] The second light amount monitor 25b is provided in the second vacuum chamber 20 and detects the amount of EUV light 1. For example, the second light amount monitor 25b is provided at a position where the EUV light that has passed through the optical element 21 (here, a cylindrical collector mirror) is irradiated. Without being limited to this, for example, the second light amount monitor 25b may detect the EUV light 1 that has been branched using a reflecting mirror or the like. This makes it possible for the second light amount monitor 25b to detect the amount of EUV light 1 guided via the collector mirror or reflecting mirror.

[0111] For example, if the surfaces of the collector mirror or the reflecting mirror are contaminated by debris, the reflectance of the EUV light decreases, and the amount of the collected EUV light 1 or the reflected EUV light 1 decreases. Therefore, the detection result of the second light amount monitor 25b functions as a parameter representing the degree of contamination of the collector mirror or the reflecting mirror. Taking advantage of this, the detection result of the second light amount monitor 25b is used to determine whether or not to perform a cleaning operation.

[0112] [Configuration of each part of the debris mitigation device] The configuration of each part of the debris mitigation device 40 will be specifically described below.

[0113] [Rotary foil trap] Fig. 3 is a schematic cross-sectional view showing a configuration example of the rotary foil trap 43. Fig. 4 is a schematic front view showing a configuration example of the rotary foil trap 43. As shown in Figs. 3 and 4, the rotary foil trap 43 has a plurality of foils (blades) F, a central support 60, and an outer ring 61. The central support 60 is connected to a shaft member 63 that rotates around a rotation axis.

[0114] The multiple foils F are thin films or thin flat plates. The central support 60 is a member that radially supports the multiple foils F. The outer ring 61 is arranged concentrically with the central support 60 and is connected to the tip of each foil F that extends radially from the central support 60. In this embodiment, the central support 60 corresponds to a rotating member. Each foil F is radially arranged around the central support 60 at approximately equal angular intervals. At this time, each foil F is on a plane including the central axis C0 of the central support 60. The material of the rotary foil trap 43 is, for example, a high-melting point metal such as tungsten (W) or molybdenum (Mo).

[0115] 4, the multiple foils F of the rotating foil trap 43 are arranged parallel to the beam direction of the EUV light 1 so as not to block the EUV light 1 traveling from the plasma P (light emitting point) to the second vacuum chamber 20. That is, the rotating foil trap 43, in which each foil F is arranged on a plane including the central axis C0 of the central support 60, is arranged so that the plasma P (light emitting point) is on an extension of the central axis C0 of the central support 60 (see FIG. 11). As a result, except for the central support 60 and the outer ring 61, the EUV light is blocked only by the thickness of each foil F, and it is possible to maximize the proportion of the EUV light 1 passing through the rotating foil trap 43 (also called the transmittance).

[0116] [Rotating foil trap cover] Fig. 5 is a schematic cross-sectional view showing a configuration example of the rotary foil trap cover 44. Fig. 6 is a schematic front view showing a configuration example of the rotary foil trap cover 44. The rotary foil trap cover 44 surrounds the outer periphery of the rotary foil trap 43 and collects debris scattered from the rotary foil trap 43. By providing the rotary foil trap cover 44, it is possible to prevent the debris captured by the rotary foil trap 43 from scattering inside the first vacuum chamber 10.

[0117] Hereinafter, the side on which the EUV light 1 is incident (the side directed toward the plasma P) will be referred to as the incident side, and the opposite side will be referred to as the exit side. The rotating foil trap cover 44 has an incident side opening KI, an exit side opening KO, and an exit side opening KO'.

[0118] The entrance side opening KI is provided at a position where the EUV light entering the rotary foil trap 43 is not blocked. The exit side opening KO is provided at a position where the EUV light 1 passing through the opening 17a of the second partition plate 17 and entering the entrance side opening KI is not blocked. The EUV light 1 that has passed through the exit side opening KO becomes light that is introduced into the second vacuum chamber 20. The exit side opening KO' is provided at a position where the EUV light 1 passing through the opening 17b of the second partition plate 17 and entering the entrance side opening KI is not blocked. The EUV light 1 that has passed through the exit side opening KO' becomes light that is introduced into the first light quantity monitor 25a.

[0119] Further, a through hole 64 is provided on the emission side surface of the rotary foil trap cover 44, through which a shaft member 63 serving as a rotation shaft of the rotary foil trap 43 passes. Note that an end of the through hole 64 is connected to, for example, the inner wall of the first vacuum chamber 10, and is not an open end. Further, an exhaust pipe 65 for exhausting debris is provided on the lower part of the rotary foil trap cover 44.

[0120] At least a part of the debris captured by the rotary foil trap 43 moves radially on the foil F of the rotary foil trap 43 by centrifugal force, detaches from the end of the foil F, and adheres to the inner surface of the rotary foil trap cover 44. The rotary foil trap cover 44 is heated by a heating means (cover heating unit) not shown or by radiation accompanying the emission of EUV light, and the debris adhered to the inner surface of the rotary foil trap cover 44 by the heating does not solidify and maintains a liquid phase state. The debris adhered to the inner surface of the rotary foil trap cover 44 is collected at the bottom of the rotary foil trap cover 44 by gravity, and is discharged to the outside of the rotary foil trap cover 44 through the discharge pipe 65 to become waste material. The debris that has become waste material is stored in a debris storage unit not shown.

[0121] The internal space of the rotary foil trap cover 44 is large enough to accommodate the rotary foil trap 43. This size is sufficiently larger than the diameter of the exit opening KO connected to the second vacuum chamber 20. As seen from the exit opening KO, the width of the space that becomes the vacuum path 13 (the cross-sectional area intersecting with the path direction) increases rapidly. In addition, the effect of the rotation of the rotary foil trap is also combined, making it possible to rapidly reduce the pressure of the buffer gas 2.

[0122] [Fixed foil trap] FIG. 7 is a schematic cross-sectional view showing a configuration example of the fixed foil trap 45. FIG. 8 is a schematic front view showing a configuration example of the fixed foil trap 45. The fixed foil trap 45 is a foil trap FT having a plurality of foils F fixed thereto, and is disposed downstream of the rotary foil trap 43 to capture debris that has passed through the rotary foil trap 43. The fixed foil trap 45 is disposed based on a central path through which a light beam (EUV extracted light) of the EUV light 1 extracted from the through-hole 12 of the first vacuum chamber 10 passes. The central path is, for example, a path connecting the light emission point of the plasma P and the center point of the through-hole 12.

[0123] Fig. 7 is a cross-sectional view of the fixed foil trap 45 along the central path of the EUV light. Fig. 8 is a view of the fixed foil trap 45 viewed from the direction of the central path of the EUV light. As shown in Figs. 7 and 8, the fixed foil trap 45 includes a plurality of foils F arranged in the vacuum path 13, and a fixed frame 66 that fixes the plurality of foils F. In this embodiment, the fixed frame 66 corresponds to a fixing member.

[0124] As shown in Fig. 8, the multiple foils F are arranged at equal intervals when viewed from the direction of the central path of the EUV light 1. Furthermore, the fixed frame 66 is, for example, rectangular when viewed from the front. The outer shape of the fixed frame 66 may be any shape. Furthermore, the multiple foils F are arranged radially so as to extend in the light beam direction of the EUV light in a cross section cut along the central path as shown in Fig. 7.

[0125] The multiple foils F of the fixed foil trap 45 serve to reduce the conductance of the portion by finely dividing the space in which the fixed foil trap 45 is arranged. For example, the buffer gas 2 is supplied to the fixed foil trap 45 from the high pressure region 14. The buffer gas 2 does not easily flow through the fixed foil trap 45, and is therefore likely to remain between the foils F.

[0126] High-speed debris that cannot be captured by the rotating foil trap 43 slows down due to an increased probability of collision with the gas retained in the fixed foil trap 45. The collision with the gas also changes the direction of the debris. The fixed foil trap 45 captures the debris that has slowed down and changed direction in this way using the foil F or the fixed frame 66. In this way, by providing the rotating foil trap 43 and the fixed foil trap 45, it is possible to sufficiently capture the debris.

[0127] In addition, since the fixed foil trap 45 has low conductance, it limits the outflow of the buffer gas 2 to the second vacuum chamber 20 and the inflow of the buffer gas 2 from the second vacuum chamber 20. This makes it difficult for the buffer gas 2 in the high pressure region 14 to leak, for example, and also makes it difficult for pressure changes in the second vacuum chamber 20 to affect the pressure in the high pressure region 14. This makes it possible to maintain the high pressure region 14 regardless of the pressure in the second vacuum chamber 20.

[0128] [Fixed foil trap cover] Fig. 9 is a schematic cross-sectional view showing a configuration example of a fixed foil trap cover. Fig. 10 is a schematic front view showing a configuration example of a fixed foil trap cover. The fixed foil trap cover 46 is a cover that surrounds the fixed foil trap 45, and is a member that connects the fixed foil trap 45 to the rotary foil trap cover 44. The fixed foil trap cover 46 has a support plate 68 in which an opening 67 and an introduction port 47 are provided, and a surrounding part 69 that extends from the outer edge of the support plate 68 to the EUV light 1 emission side.

[0129] The support plate 68 is a plate to which the fixed foil trap 45 is fixed. The surrounding portion 69 is formed so as to surround the side surface of the fixed foil trap 45. The opening 67 provided in the support plate 68 is an entrance port for the EUV light 1. An inlet 47 for introducing a buffer gas 2 is provided inside the support plate 68 so as to communicate with the opening 67. Here, the two inlets 47 are provided at positions on opposite sides of the opening 67. By supplying the buffer gas 2 from the inlet 47, the space constituting the opening 67 becomes the high pressure region 14.

[0130] Figure 11 is a schematic cross-sectional view showing a configuration example of the debris mitigation device 40. The debris mitigation device 40 shown in Figure 11 is configured by assembling the above-mentioned rotating foil trap 43, rotating foil trap cover 44, fixed foil trap 45, and fixed foil trap cover 46.

[0131] Specifically, the rotary foil trap 43 is disposed inside the rotary foil trap cover 44. A support plate 68 of the fixed foil trap cover 46 is connected to the rear of the rotary foil trap cover 44 so that the exit side opening KO and the opening 67 overlap. A fixed frame 66 of the fixed foil trap 45 is connected inside the fixed foil trap cover 46 so as to cover the opening 67 of the support plate 68. A rear end of the fixed foil trap cover 46 is connected to the through hole 22 of the second vacuum chamber 20 via a flange or the like (not shown).

[0132] With this configuration, the first vacuum chamber 10 and the second vacuum chamber 20 are connected by a vacuum path 13 that passes through a high pressure region 14 inside the debris mitigation device 40. The pressure inside the light source device 100 when the debris mitigation device 40 is used will be specifically described below.

[0133] [Pressure inside the light source] FIG. 12 is a graph showing the simulation results of the pressure inside the light source device. For this simulation, a model of the debris mitigation device 40 shown in FIG. 11 was created, and the pressure distribution in the model was calculated. FIG. 12 shows the pressure profile along the central path O of the EUV light 1. The horizontal axis of the graph is the distance along the central path O. Here, the relative distance to the distance D from the plasma P to the measurement end in the second vacuum chamber 20 is used. The vertical axis of the graph is the pressure [Pa] at each position.

[0134] Point Oa on the graph corresponds to the generation position of plasma P. Point Ob corresponds to the entrance end of vacuum path 13 (entrance side opening KI of rotary foil trap cover 44). Point Oc corresponds to high pressure region 14 (opening 67 of support plate 68). Point Od corresponds to the exit end of vacuum path 13 (rear end of fixed foil trap 45).

[0135] 12 shows a pressure profile (solid line graph) when the pressure P2 of the second vacuum chamber 20 is set to 0.7 Pa, and a pressure profile (dotted line graph) when P2 is set to 5 Pa. In both graphs, the exhaust rate of the first vacuum pump 54 that evacuates the first vacuum chamber 10 and the flow rate of the buffer gas 2 are set to constant values ​​for the simulation. As a result, the pressure P1 of the first vacuum chamber 10 became 3 Pa.

[0136] For example, a high pressure is maintained in the shaded area centered on point Oc. This shaded area is the high pressure area 14. For example, the area formed by the entrance side opening KI of the rotary foil trap cover 44 and the opening 67 of the fixed foil trap cover 46 is the high pressure area 14. From this simulation, when P2=0.7 Pa, the pressure Ph of the high pressure area 14 is 18 Pa or more relative to the pressure near point Oa.

[0137] A fixed foil trap 45 is provided from the high pressure region 14 to point Od on the second vacuum chamber 20 side, and the pressure drops almost uniformly. A rotary foil trap cover 44 including a rotary foil trap 43 is provided from the high pressure region 14 to point Ob on the first vacuum chamber 10 side, and the pressure also drops toward point Ob. The part where the pressure gradient is bent corresponds to the end of the entrance side of the rotary foil trap 43. The pressure drop until point Ob occurs due to the buffer gas 2 spreading rapidly inside the rotary foil trap cover 44.

[0138] Now, suppose that the pressure P2 in the second vacuum chamber 20 increases from 0.7 Pa to 5 Pa. The pressure Ph in the high pressure region 14 increases slightly as P2 increases. Here, the increase in Ph is about 0.5 Pa, which is about 1 / 8 of the increase in P2 (4.3 Pa). In this way, the change in Ph is sufficiently smaller than the change in P2. In other words, the change in pressure P2 in the second vacuum chamber 20 is almost entirely absorbed by the gas diffusion effect in the high pressure region 14 and the rotary foil trap 43, and is not easily transmitted to the first vacuum chamber 10.

[0139] Furthermore, even if P2 increases, the pressure distribution from the high pressure region 14 to the first vacuum chamber 10 side hardly changes. For example, the pressure from point Oa to point Ob (the pressure from the plasma P to the entrance end of the debris mitigation device 40) is approximately constant (about 3 Pa) regardless of whether P2 increases or decreases. This means that the pressure P1 in the first vacuum chamber 10 is approximately constant, regardless of the pressure P2 in the second vacuum chamber 20.

[0140] In this way, in the debris mitigation device 40, it is possible to separate P1 and P2 by generating the high pressure region 14 so as to block the vacuum path 13. As a result, it is possible to suppress a change in pressure P1 on the light source side caused by a change in pressure P2 on the EUV light introduction side.

[0141] Furthermore, taking into consideration the debris capturing capability of the debris mitigation device 40, it is preferable to set the pressure Ph of the high pressure region 14 to a pressure that is six or more times the pressure P1 of the first vacuum chamber 10. This makes it possible to reliably maintain the pressure P1 of the first vacuum chamber 10 while sufficiently capturing debris from the plasma P.

[0142] Fig. 13 is a graph showing the relationship between the pressures of the first vacuum chamber 10 and the second vacuum chamber 20. Fig. 13 shows the relationship between the pressure P1 of the first vacuum chamber 10 and the pressure P2 of the second vacuum chamber 20, which were actually measured in the light source device 100. The vertical axis of the graph is P1, and the horizontal axis is P2. Here, the pressure P2 of the second vacuum chamber 20 was changed while keeping the exhaust amount of the first vacuum chamber 10 constant so that P1 was approximately 2 Pa.

[0143] 13, it was found that even if the pressure P2 in the second vacuum chamber 20 was changed within a range of 20 Pa or less, the pressure P1 in the first vacuum chamber 10 showed a value of around 2 Pa. That is, even though the pressure was high on the downstream side across the debris mitigation device 40, the pressure in the upstream space where the plasma P was generated hardly changed from the set value. In other words, it was found that the pressure P1 in the first vacuum chamber 10 where the plasma P was generated could be kept constant regardless of whether the pressure P2 in the second vacuum chamber 20 was high or low.

[0144] 13, the flow rate of the buffer gas 2 supplied to the high pressure region 14 was set to be approximately the same as the flow rate used in the simulation shown in FIG. 12. Therefore, the pressure Ph of the high pressure region 14 is approximately 20 Pa. Therefore, it can be said that the debris mitigation device 40 does not substantially change the pressure of the first vacuum chamber 10 when the pressure P2 of the second vacuum chamber changes at least within a range equal to or less than the pressure of the high pressure region Ph. This makes it possible to sufficiently maintain the pressure of the first vacuum chamber, for example, even if the pressure of the second vacuum chamber changes.

[0145] [Sputtering by EUV light and buffer gas] Up to this point, the description has been mainly given of the pressure characteristics in the light source device 100. In the following, sputtering caused by the EUV light 1 and the buffer gas 2 in the light source device 100 will be described.

[0146] In general, an optical system that handles EUV light 1 can become contaminated by debris dispersed from the plasma P and carbon-based deposits (carbon contamination), which can degrade its performance. In addition, high-speed debris flying inside the chamber can collide with the optical system, which can cause the reflective film on the surface of the optical system to be scraped off. As a countermeasure to this, a method is known in which high-speed debris is reduced by colliding with a buffer gas 2, for example. In addition, a method is known in which debris and carbon contamination that have adhered to the optical system are removed by using radicals from an active gas or the like.

[0147] The inventors have studied a method of protecting the optical elements 21 and other elements downstream of the debris mitigation device 40 (DMT) by utilizing the pressure distribution of argon gas, which is the buffer gas 2. In this method, for example, low-speed debris is captured by a rotating foil trap 43, and high-speed debris is decelerated by the buffer gas 2 and captured by a fixed foil trap 45.

[0148] On the other hand, debris that is not captured by the debris mitigation device 40 may enter the second vacuum chamber 20. In this case, high-speed debris may collide with the optical element 21 downstream of the debris mitigation device 40, causing the optical element 21 to be sputtered. In response, the pressure of the argon gas around the optical element 21 (the pressure of the second vacuum chamber 20) was increased in the hope of suppressing sputtering of the optical element 21 by debris, but it was found that this actually promoted sputtering of the optical element 21.

[0149] In this way, the present inventor found that sputtering occurs by introducing argon gas. It is considered that the argon gas ionized by the EUV light 1 collides with the optical element 21, and the surface of the optical element 21 is sputtered. For example, the argon gas is ionized by irradiation with the EUV light 1 to form a plasma (EUV-induced plasma). When the EUV-induced plasma is formed, the argon ions are accelerated toward the optical element 21, and the ions collide with the surface of the optical element 21 to generate sputtering. It is considered that the ions are accelerated because a potential difference occurs between the EUV-induced plasma and the optical element 21. In this way, by using an ionized gas (here, argon gas) that is ionized by the EUV light 1 as the buffer gas 2, sputtering by the ionized gas can be realized. The experimental results of sputtering will be described below.

[0150] [Sputtering experiment] Fig. 14 is a schematic diagram showing an example of the arrangement of samples used in a sputtering experiment. As shown in Fig. 14A and Fig. 14B, in the experiment, a sample 27 for sputtering was arranged on a stage 26 arranged downstream of a debris mitigation device 40. Here, the sample 27 was a sample on which a thin film of ruthenium (Ru) was formed, and the sputtering rate for the sample 27 was measured. The thin film of ruthenium is a material used for a reflective surface that reflects, for example, EUV light 1.

[0151] 14A, the tilt angle of the stage 26 with respect to the central path O of the EUV light 1 is set to about 20°. The pressure P1 of the first vacuum chamber 10 in which the plasma P that radiates the EUV light 1 is generated (the pressure in the area on the left side in the figure of the debris mitigation device 40) is set to about 2 Pa. The pressure P2 of the second vacuum chamber 20 in which the sample 27 is placed (the pressure in the area on the left side in the figure of the debris mitigation device 40) is set to a range from about 0.5 Pa to about 11 Pa.

[0152] 14A, five samples 27 were placed on the stage 26 so as to be irradiated with the EUV light 1. Below, these samples 27 are referred to as Sample 1, Sample 2, Sample 3, Sample 4, and Sample 5 in order from the side closest to the plasma P. The distance between the plasma P and the end of Sample 1 on the plasma P side was about 35 cm. The intervals between Samples 1 to 5 were about 5 cm.

[0153] In FIG. 14B, the tilt angle of the stage 26 with respect to the central path O of the EUV light 1 was set between about 25° and about 45°. The pressure P1 in the first vacuum chamber 10 was set to about 2 Pa, similar to FIG. 14A. The pressure P2 in the second vacuum chamber 20 was set in the range of about 13 Pa to about 19 Pa. One sample 27 (referred to as Sample 6) was placed on the stage 26 so as to be irradiated with the EUV light 1. The distance between the plasma P and the end of Sample 6 on the plasma P side was set to about 35 cm, similar to the case of Sample 1 in FIG. 14A.

[0154] FIG. 15 is a graph showing the relationship between the sputtering rate and pressure. The horizontal axis of the graph is the pressure P2 [Pa] in the second vacuum chamber 20. The vertical axis of the graph is the sputtering rate. The unit of the sputtering rate is nm / Gpulse. This is when the number of times the plasma P emits light (the number of power pulses) is 1×10 9 These figures show the thickness of the film (nm) sputtered when the number of times is 1.

[0155] Among the points shown in Fig. 15, the points other than the rightmost point are the results obtained by evaluating the sputtering rate for Sample 1 shown in Fig. 14A, with the tilt angle set to about 20°. The rightmost point is the result obtained by evaluating the sputtering rate for Sample 6 shown in Fig. 14B, with the tilt angle set to about 25°. The distance from the plasma P for all points was set to about 35 cm.

[0156] 15, when the pressure P2 of the second vacuum chamber 20 is 6 Pa or less, the sputtering rate for the ruthenium thin film does not change significantly even if the pressure is changed, and is approximately 5 nm / Gpulse or less. In contrast, when P2 is 6 Pa or more, it was confirmed that the sputtering rate increases with increasing pressure.

[0157] Fig. 16 is a graph showing the relationship between the sputtering rate, pressure, and sample position. In Fig. 16, the sputtering rates of the five samples 27 (Sample 1 to Sample 5) shown in Fig. 14A when the pressure P2 of the second vacuum chamber 20 is set to 0.7 Pa, 2.0 Pa, 5.5 Pa, and 11 Pa are shown in a bar graph using rectangular columns. Note that for the condition of P2=11 Pa, only the data of Sample 1, Sample 3, and Sample 5 are shown.

[0158] For example, the sputtering rate for Sample 1 is low when P2 is in the range up to 5.5 Pa, but when P2=11 Pa, the sputtering rate increases significantly compared to the previous values. Similarly, for Sample 3 and Sample 5, the sputtering rate is low when P2 is in the range below 5.5 Pa, but when P2=11 Pa, the sputtering rate increases significantly. From this, as with the data shown in FIG. 15, it can be seen that below a certain pressure, a sufficient sputtering rate is not obtained and no significant sputtering occurs.

[0159] Furthermore, for example, when P2=0.7 Pa, the sputter rate is largest in Sample 1 close to the plasma P, and the further away from the plasma P the sputter rate decreases; for example, in Sample 5, the sputter rate is approximately 0. In other words, it can be seen that the further away from the plasma P the sputter rate decreases. This is also true for other pressures (P2=2.0 Pa and P2=5.5 Pa) where the sputter rate is generally low. Also, even at a pressure (P2=11 Pa) where the sputter rate increases, the sputter rate decreases with increasing distance from the plasma P. From this, it can be seen that the sputter rate decreases with increasing distance from the plasma P, regardless of the pressure P2.

[0160] Fig. 17 is a graph showing the relationship between the sputtering rate and the emission frequency of the plasma. Fig. 17 shows the frequency dependency of the sputtering rate on the emission frequency of the plasma P (EUV light 1). Here, for Sample 6 shown in Fig. 14B, the sputtering rate was measured with the emission frequency set to 3000 Hz and 6000 Hz. The pressure P2 of the second vacuum chamber 20 was set to about 13 Pa, and the inclination angle of the sample 27 was set to about 25°.

[0161] As shown in Fig. 17, the sputtering rate increased when the emission frequency was 6000 Hz compared to when the emission frequency was 3000 Hz. In other words, it was confirmed that the sputtering rate increases according to the emission frequency. In general, when the emission frequency is increased, the average power (light amount) of the EUV light 1 increases, and the total number of argon ions ionized by the EUV light 1, i.e., the total number of argon ions generated by the EUV light 1, increases. It is believed that the sputtering rate increased in Fig. 17 for such a reason.

[0162] For example, when the emission frequency is set low, if the value of P2 is set to the same pressure as when the emission frequency is high, the sputtering speed will be slow. In such a case, P2 can be increased to ensure the cleaning speed. Conversely, when it is difficult to adjust P2, the sputtering rate can be changed by adjusting the emission frequency.

[0163] [Spatter cleaning operation] The sputtering phenomenon caused by the ionized gas (buffer gas 2) ionized by the EUV light 1 has the effect of scraping the surface of the optical element 21 provided in the second vacuum chamber 20 in the light source device 100. In other words, by utilizing sputtering, it becomes possible to remove debris and carbon contamination attached to the optical element 21 and sputter clean the optical element 21.

[0164] The present inventors have focused on this point and provided the light source device 100 with a function of performing a cleaning operation using an ionized gas that is the buffer gas 2, in addition to a normal operation of supplying the EUV light 1 to a utilization device, etc. In other words, the light source device 100 is capable of a normal operation and a cleaning operation.

[0165] The normal operation is, for example, an operation in which plasma P (EUV light 1) is stably generated and the EUV light 1 is supplied to a utilization device or the like. In other words, the normal operation is an operation in which the light source device 100 operates as a light source of EUV light 1, which is the original purpose of the light source device 100. Hereinafter, the pressure P2 in the second vacuum chamber 20 during normal operation may be referred to as a normal pressure P2n. In this embodiment, the normal pressure P2n corresponds to the first pressure.

[0166] The pressure P1 of the first vacuum chamber 10 during normal operation is set to a pressure P0 at which the EUV light 1 is stable. P0 is typically a pressure at which the plasma P is stably generated, and is, for example, about 2 Pa. The specific value of P0 is not limited. For example, a pressure at which the plasma P can be stably generated may be set to P0 depending on the type of plasma raw material, the discharge conditions, etc. In this embodiment, the pressure P0 at which the EUV light 1 is stable corresponds to the third pressure.

[0167] The cleaning operation is different from the normal operation and is an operation for cleaning the optical elements by sputtering. In the light source device 100, the normal operation and the cleaning operation are appropriately switched and executed. Hereinafter, the pressure P2 in the second vacuum chamber 20 during the cleaning operation may be referred to as a cleaning pressure P2c. In this embodiment, the cleaning pressure P2c corresponds to the second pressure.

[0168] As described above, in the light source device 100, it is possible to change only the pressure P2 in the second vacuum chamber 20 (the pressure around the optical element 21) while maintaining the pressure P1 in the first vacuum chamber 10. By utilizing this characteristic, it is possible to control the amount of sputtering on the optical element 21 without changing the pressure P1 on the plasma P side.

[0169] For example, when the optical element 21 provided in the second vacuum chamber 20 is contaminated with debris or the like flying from the plasma P, which is the light source, by changing the pressure P2 in the second vacuum chamber 20 while the light source is turned on in the first vacuum chamber 10, the debris or the like adhering to the optical element 21 can be scraped off by the sputtering phenomenon, thereby cleaning the optical element 21. In this way, in the light source device 100, for example, the optical element 21 or the like provided in the second vacuum chamber 20 can be cleaned while stably generating the EUV light 1.

[0170] As described with reference to Figures 15 and 16, sputtering by the buffer gas 2 occurs when the pressure P2 in the second vacuum chamber 20 is higher than a certain pressure. Therefore, at pressures lower than that pressure, sputtering hardly occurs. For this reason, the normal pressure P2n is set to a pressure at which no sputtering occurs, and the cleaning pressure P2c is set to a pressure higher than P2n at which significant sputtering occurs.

[0171] In other words, the cleaning operation is an operation in which a buffer gas 2 is introduced into the second vacuum chamber 20, which is maintained at the normal pressure P2n, which is the pressure during normal operation, the pressure in the second vacuum chamber 20 is increased to a cleaning pressure P2c that is higher than the normal pressure P2n, and, while maintaining the cleaning pressure P2c, sputtering is performed on the optical element 21 placed in the second vacuum chamber 20 using the buffer gas 2 ionized by the EUV light 1.

[0172] In this manner, in the cleaning operation, sputtering is performed by increasing the pressure P2 in the second vacuum chamber 20 from the normal pressure P2n to the cleaning pressure P2c. In this method, the cleaning operation can be easily performed by simply adjusting the exhaust amount of the second vacuum chamber 20, for example.

[0173] Even if the pressure in the second vacuum chamber 20 changes, the pressure P1 in the first vacuum chamber 10 changes very little due to the action of the high pressure region 14 of the debris mitigation system 40, and is maintained at the pressure P0 at which the EUV light 1 is stable. Therefore, when starting a cleaning operation or returning to normal operation, there is no need to adjust the exhaust volume of the first vacuum chamber 10.

[0174] In this embodiment, the cleaning pressure P2c is set to 6 Pa or more. For example, referring to Fig. 15, it can be seen that the sputtering rate increases according to the pressure if it is 6 Pa or more. Therefore, by setting the cleaning pressure P2c in the range of 6 Pa or more, it is possible to perform sputtering at a desired sputtering rate, for example.

[0175] Moreover, it is preferable that the cleaning pressure P2c is set to a pressure three or more times the pressure P0 at which the EUV light 1 is stable, which is set in the first vacuum chamber 10. For example, if P2c is about the same pressure as P0, it is difficult to achieve a sufficient sputtering rate, but by setting the pressure to three or more times, a relatively high sputtering rate can be achieved. This makes it possible to, for example, shorten the cleaning time for the optical element 21.

[0176] On the other hand, the normal pressure P2n of the second vacuum chamber 20 is set to, for example, a pressure equivalent to the pressure P0 at which the EUV light 1 is stable. In this case, it is possible to sufficiently lower the sputtering rate, and a state in which no significant sputtering occurs during normal operation can be maintained. This makes it possible to avoid a situation in which the optical element 21 is unnecessarily sputtered during normal operation.

[0177] In the cleaning operation, the optical element 21 is sputtered while the second vacuum chamber 20 is maintained at the cleaning pressure P2c. For example, the sputtering time is calculated based on the sputtering rate according to the cleaning pressure P2c and the target sputtering amount. Then, the cleaning pressure P2c is maintained only for the sputtering time. Alternatively, it is also possible to maintain the cleaning pressure P2c until the characteristics of the optical element 21 (such as the amount of reflected light) return to the state before contamination.

[0178] The sputtering process may also include a process of changing the amount of EUV light 1 from the amount of EUV light 1 during normal operation while maintaining the cleaning pressure P2c. For example, as described with reference to Fig. 17, the sputtering rate can also be adjusted when the amount of EUV light 1 (average power) is changed. Therefore, in this process, any parameter capable of changing the amount of EUV light 1 is adjusted.

[0179] For example, the emission frequency may be adjusted as in the case of FIG. 17. In this case, to increase the sputtering rate, the emission frequency may be increased. Also, the irradiation intensity of the laser beam LB may be adjusted, or the pulse power (charging energy) applied to the discharge electrodes EA and EB may be adjusted. The sputtering rate can be increased by increasing the irradiation intensity or pulse power of the laser beam.

[0180] In addition, in the sputtering process, other conditions that change the sputtering rate may be appropriately changed. For example, the sputtering rate may be increased by moving the position of the optical element 21 closer to the plasma. Furthermore, from the experiments in FIGS. 14A and 14B, it was found that the sputtering rate can be adjusted by changing the tilt angle of the sample 27. That is, in order to adjust the sputtering rate, the irradiation angle of the EUV light 1 with respect to the optical element 21, etc. may be adjusted. In this case, the sputtering rate can be reduced by making the irradiation angle shallower. Besides, the types of parameters adjusted in the sputtering process are not limited.

[0181] [Light source operation] Fig. 18 is a flowchart showing an example of the operation of the light source device 100. The process shown in Fig. 18 is a process for executing the cleaning method according to this embodiment. In the following, an example of cleaning the optical element 21 provided in the second vacuum chamber 20 will be described.

[0182] The determination as to whether or not to perform the cleaning operation is based on the detection result of the second light amount monitor 25b (see FIG. 2) which detects the amount of EUV light 1 that has passed through the optical element 21. That is, in the process shown in FIG. 18, the normal operation and the cleaning operation are switched and executed based on the detection result of the second light amount monitor 25b.

[0183] The process shown in Fig. 18 may be performed automatically using a controller of the light source device 100 or the like. In this case, the pressure and the like are automatically controlled based on the detection result of the second light amount monitor 25b. Also, the user of the light source device 100 may manually control the pressure and the like by checking the detection result of the second light amount monitor 25b. Also, an instruction to perform a cleaning operation may be output to the user from the controller that reads the detection result of the second light amount monitor 25b.

[0184] First, normal operation is performed (step 101). In normal operation, the pressure P1 in the first vacuum chamber 10 is set to a pressure P0 that stabilizes the EUV light 1. The pressure P2 in the second vacuum chamber 20 is set to a normal pressure P2n. This allows stable EUV light 1 to be supplied to a utilization device or the like.

[0185] Next, it is determined whether or not to start the cleaning operation (step 102). Specifically, it is determined whether or not the light amount detected by the second light amount monitor 25b (light amount of the EUV light 1 that has passed through the optical element 21) is lower than a predetermined threshold (start determination threshold). The start determination threshold is, for example, a lower limit value of the light amount of the EUV light 1 supplied to the utilization device or the like in normal operation. There are no other limitations on the method of setting the start determination threshold. In this embodiment, the start determination threshold corresponds to the first threshold.

[0186] For example, if the light amount is equal to or greater than the start determination threshold, it is determined that the dirt on the optical element 21 is within an acceptable range and the cleaning operation is not to be started (No in step 102). In this case, the process returns to step 101 and normal operation is continued.

[0187] On the other hand, if the light amount is lower than the start determination threshold, it is determined that the contamination of the optical element 21 has reached an unacceptable level, and a cleaning operation is to be started (Yes in step 102). In this case, a pressure increase step is performed to increase the pressure in the second vacuum chamber 20 (step 103).

[0188] The pressure increasing step is a step of introducing an ionized gas (buffer gas 2) that is ionized by the EUV light 1 into the second vacuum chamber 20 that is maintained at a normal pressure P2n, which is the pressure during normal operation, while the plasma P is being generated, and increasing the pressure P2 of the second vacuum chamber 20 to a cleaning pressure P2c that is higher than the normal pressure P2n. For example, the exhaust amount of the second vacuum chamber 20 is reduced, and the second vacuum valve 52 is adjusted so that P2=P2c. Also, for example, the flow rate control valve may be adjusted so that the flow rate of the buffer gas 2 flowing into the second vacuum chamber 20 is increased.

[0189] When the pressure in the second vacuum chamber 20 reaches the cleaning pressure, a sputtering process is performed to sputter the optical element 21 (step 104). The sputtering process is a process in which, while maintaining the cleaning pressure P2c, sputtering is performed on the optical element 21, which is a target placed in the second vacuum chamber 20, using the buffer gas 2 ionized by the EUV light 1. Here, by maintaining the second vacuum chamber 20 at the cleaning pressure P2c, the surface of the optical element 21 is sputtered at a sputtering rate according to P2c, and debris and the like are removed.

[0190] In addition, in the sputtering process, a process (light amount adjustment process) of changing the light amount of the EUV light 1 from the light amount of the EUV light 1 during normal operation may be performed while maintaining the cleaning pressure P2c. The light amount adjustment process is a process of adjusting parameters (e.g., the emission frequency of the EUV light 1, the brightness and pulse power of the laser beam LB) capable of changing the light amount of the EUV light 1 so as to obtain, for example, a desired sputtering rate.

[0191] By introducing the light amount adjustment process, it becomes possible to realize a desired sputtering rate even in cases where it is difficult to adjust the sputtering rate using only the cleaning pressure P2c. The method for adjusting the sputtering rate is not limited. For example, the position (distance from the plasma P) or the attitude (irradiation angle of the EUV light 1) of the optical element 21 may be adjusted.

[0192] 18, when the light amount detected by the second light amount monitor 25b becomes lower than the start determination threshold, the pressure increase step and the sputtering step are executed. This makes it possible to perform the cleaning operation (pressure increase step and sputtering step) at the timing when cleaning of the optical element 21 becomes necessary. It is also possible to avoid unnecessary cleaning operations.

[0193] When the sputtering process is performed, it is determined whether or not to end the cleaning operation (step 105). Specifically, it is determined whether or not the light amount detected by the second light amount monitor 25b is higher than a predetermined threshold (end determination threshold). The end determination threshold is set to a value equal to or greater than the above-mentioned start determination threshold. In this embodiment, the end determination threshold corresponds to the second threshold.

[0194] For example, an appropriate value for the amount of EUV light 1 supplied to a utilization device or the like during normal operation is set as the termination judgment threshold. This makes it possible to return the amount of EUV light 1 to an appropriate value. Alternatively, an upper limit value for the amount of EUV light 1 may be set as the termination judgment threshold. Also, the same value as the start judgment threshold may be set as the termination judgment threshold. Other than this, the method of setting the termination judgment threshold is not limited.

[0195] If the amount of light detected by the second light amount monitor 25b is lower than the end determination threshold, it is determined that dirt remains on the optical element 21 and the cleaning operation is not to be ended (No in step 105). In this case, the process returns to step 104 and the sputtering process is continued.

[0196] On the other hand, if the light amount is higher than the end determination threshold, it is determined that the optical element 21 has been cleaned to an acceptable level, and the cleaning operation is to be ended (Yes in step 105). In this case, a pressure reduction step is executed to reduce the pressure in the second vacuum chamber 20 (step 106).

[0197] The pressure reduction step is a step of reducing the pressure P2 in the second vacuum chamber 20 to a normal pressure P2n when the light amount detected by the second light amount monitor 25b becomes higher than the end determination threshold. For example, the second vacuum valve 52 is adjusted so that the exhaust amount of the second vacuum chamber 20 is increased and P2=P2n is satisfied. Also, for example, the flow rate control valve may be adjusted so that the flow rate of the buffer gas 2 flowing into the second vacuum chamber 20 is reduced.

[0198] This step can be said to be a step of returning, for example, the second vacuum valve 52 and the flow rate control valve to their normal operation states. Note that, if the parameters for changing the light intensity of the EUV light 1 or the position and attitude of the optical element 21 are adjusted in the sputtering step, they are returned to their normal operation states. This makes it possible to end the cleaning operation and return to normal operation.

[0199] When the pressure P2 in the second vacuum chamber 20 returns to the normal pressure P2n, it is determined whether or not to stop the operation of the light source device 100 (step 107). For example, if the operation is to be stopped for maintenance or the like (Yes in step 107), the light source device 100 is stopped. If the operation is not to be stopped (No in step 107), the process returns to step 101 and normal operation is resumed.

[0200] In this way, the cleaning operation is an operation that changes the pressure downstream of the debris mitigation device 40 in which the optical element 21 is placed (pressure P2 in the second vacuum chamber 20). In contrast, even if the pressure downstream of the debris mitigation device 40 is changed in the light source device 100, the pressure in the space where the emission point of the plasma P is located upstream of the debris mitigation device 40 (pressure P2 in the first vacuum chamber 10) does not change. In other words, even when a cleaning operation is performed, there is no need to change the main operating conditions on the light source side. This makes it possible to quickly return to normal operation when the cleaning operation is completed.

[0201] [Sputtering area and mask usage] 19 is a schematic diagram for explaining the sputtering region where sputtering occurs. Here, an experiment conducted to confirm the region (sputtering region 70) where sputtering occurs due to the buffer gas 2 irradiated with the EUV light 1 will be explained using the schematic diagram. The sputtering region 70 refers to the region where the surface of the sample 27 is actually etched by the sputtering phenomenon.

[0202] The diagram on the left side of FIG. 19 is a schematic diagram showing the state of sample 27 before being sputtered. In the experiment, a plate-shaped sample 27 was fixed with bolts to a stage 26 introduced into the second vacuum chamber 20. A thin film of tungsten (W) with an oxidized surface was used as sample 27. The tungsten oxide formed on the surface of sample 27 was black in color and had no metallic luster. Here, the color of tungsten oxide is diagrammatically shown as dark gray.

[0203] Next, as shown in the center diagram of Figure 19, the sample 27 was introduced into the second vacuum chamber 20 so that a part of it overlapped with the optical path of the EUV light 1, and sputtering was performed with P2 = 13 Pa. The dotted area in the diagram represents the optical path of the EUV light 1. In the experiment, the sample 27 was placed at the end of the optical path of the EUV light 1 (irradiation range of the EUV light 1), and the EUV light 1 was irradiated only to the left half of the sample 27, without using a light-shielding member that would generate impurities.

[0204] The diagram on the right side of FIG. 19 is a schematic diagram showing the state of sample 27 after sputtering. In the right half of sample 27, which was not irradiated with EUV light 1, the black color of tungsten oxide remained. On the other hand, a metallic luster was confirmed in the left half of sample 27, which was irradiated with EUV light 1. In other words, tungsten oxide was etched in the area irradiated with EUV light 1. Here, the color of tungsten exposed after tungsten oxide was removed is shown in light gray. The light gray area in sample 27 is the sputtered area 70.

[0205] In this way, it was found that the region irradiated with the EUV light 1 becomes the sputtering region 70 where etching by sputtering occurs. It was also found that even inside the second vacuum chamber 20, in regions not irradiated with the EUV light 1, etching by sputtering hardly occurs. In other words, it is possible to limit the sputtering region 70 by limiting the irradiation of the EUV light 1. Below, a configuration for limiting the irradiation of the EUV light 1 by using a light shielding plate will be described.

[0206] Fig. 20 is a schematic diagram showing an example of the configuration of an optical system using a light shielding plate. The optical system 24a shown in Fig. 20 is an optical system that collects the EUV light 1 emitted from the plasma P and passed through the debris mitigation device 40. The left side of the debris mitigation device 40 is the space in the first vacuum chamber 10 where the plasma P is generated, and the right side of the debris mitigation device 40 is the space in the second vacuum chamber 20 where the optical system 24a is arranged.

[0207] The optical system 24a has a cylindrical collector mirror 71a and a light shielding plate 72a. The collector mirror 71a is an example of the optical element 21 provided in the second vacuum chamber 20. The optical system 24a has a configuration in which the light shielding plate 72a is added to the light source device 100 described with reference to FIG.

[0208] The collector mirror 71a has a rotationally symmetric cylindrical reflecting surface on the inside, and is disposed so that the central axis of the reflecting surface coincides with the central path O of the EUV light 1. The collector mirror 71a is supported so as to be rotatable about the central path O. The light shielding plate 72a is a plate-shaped member that shields a portion of the EUV light that passes through the debris mitigation device 40 and heads toward the collector mirror 71a. Here, the light shielding plate 72a is disposed so as to cover the upper half of the area on the collector mirror 71a where the EUV light 1 is incident. Note that a light shielding plate 72a that covers 2 / 3 of the area on which the EUV light 1 is incident, or a light shielding plate 72a that covers 3 / 4 of the area may also be used.

[0209] In the optical system 24a, the EUV light 1 that has passed through the debris mitigation device 40 and is incident on the collector mirror 71a without being blocked by the light shielding plate 72a is collected. In this case, the reflecting surface of the collector mirror 71a that is irradiated with the EUV light 1 is etched by the buffer gas 2. This may cause deterioration of the reflecting surface over time. On the other hand, the reflecting surface that is shielded by the light shielding plate 72a is not etched by the buffer gas 2, so that the reflecting surface can be maintained without deterioration.

[0210] For example, if the characteristics of the reflective surface that has been reflecting the EUV light 1 deteriorate, the collector mirror 71a can be rotated to use an undegraded reflective surface. Since the collector mirror 71a rotates about the central path O as an axis, the optical path of the EUV light 1 is not changed by the rotation of the collector mirror 71a. This makes it possible to maintain the light collection performance without replacing the collector mirror 71a, and for example, to extend the maintenance interval.

[0211] Fig. 21 is a schematic diagram showing another example of the configuration of an optical system using a light shielding plate. The optical system 24b shown in Fig. 21 is provided, for example, in the first vacuum chamber 10, and is an optical system that collects the EUV light 1 emitted from the plasma P. The optical system 24b has a concave collector mirror 71b and a light shielding plate 72b.

[0212] The collector mirror 71b has a concave reflective surface formed, for example, by a curved surface of rotation, and is disposed with the reflective surface facing the plasma P. The collector mirror 71b is supported so as to be rotatable about a central axis C of the reflective surface. The collector mirror 71b may be constituted by a plurality of mirrors as long as the configuration does not change the focused position of the EUV light 1 when the collector mirror 71b rotates about the central axis C. The light shielding plate 72b shields a portion of the EUV light traveling from the plasma P toward the collector mirror 71b. Here, the light shielding plate 72b is disposed so as to cover the reflective surface of the lower half of the collector mirror 71b, but the range of the reflective surface covered by the light shielding plate 72b is not limited.

[0213] For example, even in the first vacuum chamber 10 where the plasma P is generated, sputtering that deteriorates optical elements such as the collector mirror 71b may occur depending on the light emission conditions of the plasma P. In the optical system 24b, for example, if the characteristics of the reflecting surface of the collector mirror 71b deteriorate, the collector mirror 71b can be rotated to use an undegraded reflecting surface, as in the case of Fig. 20. This makes it possible to maintain the light collecting performance without replacing the collector mirror 71b.

[0214] As described above, in the light source device 100 according to this embodiment, the debris reduction device 40 forms a vacuum path 13 connecting the first vacuum chamber 10 in which the plasma P is generated and the second vacuum chamber 20 in which the EUV light 1 from the plasma P is introduced. Furthermore, a high-pressure region 14 having a pressure higher than the pressure P1 of the first vacuum chamber 10 and the pressure P2 of the second vacuum chamber 20 is formed so as to block the vacuum path 13. As a result, for example, a change in pressure in the second vacuum chamber 20 is absorbed by the high-pressure region 14. This makes it possible to suppress a change in the pressure P1 on the light source side caused by a change in the pressure P2 on the introduction side of the EUV light 1.

[0215] Generally, radiation such as the EUV light 1 emitted from the plasma P is introduced into the utilization device through a passage maintained in a vacuum state. For this reason, if the pressure on the introduction side is changed due to maintenance of an optical system installed in the middle of the passage or a change in the conditions on the utilization device side, it is considered that this will lead to a change in the pressure around the plasma P. In this case, the light emission conditions of the plasma P will change, and there is a possibility that the radiation such as the EUV light 1 will become unstable.

[0216] In the light source device 100 according to this embodiment, a high-pressure region 14 that enables differential pumping is formed inside the debris mitigation device 40. As a result, changes in pressure P2 in the second vacuum chamber 20 on the introduction side of the EUV light 1 are absorbed by the flow rate of the buffer gas 2 in the high-pressure region 14, and do not affect the pressure P1 in the first vacuum chamber 10 that is the light source area where the plasma P is generated. Of course, the debris mitigation device 40 that generates the high-pressure region 14 also maintains the function of reducing debris from the plasma P.

[0217] This makes it possible to suppress the intrusion of debris into the second vacuum chamber 20 and to fully prevent a situation in which the EUV light 1 becomes unstable due to a change in the pressure P2 in the second vacuum chamber 20. Therefore, even when the pressure P2 in the second vacuum chamber 20 is changed, for example, to perform maintenance on the optical system or to change the conditions on the utilization device side, it becomes possible to stably perform the emission operation of the EUV light 1. This makes it possible to improve the operability and maintainability of the light source device 100 and the utilization device that uses it.

[0218] Furthermore, in this embodiment, the characteristic of the light source device 100 that allows the pressure P2 of the second vacuum chamber 20 to be changed while stably supplying EUV light 1 is utilized to perform sputtering cleaning of the optical element 21 provided in the second vacuum chamber 20.

[0219] In cleaning by sputtering, for example, it is possible to change the sputtering rate by increasing or decreasing the pressure in the second vacuum chamber 20. For example, if it is desired to avoid damaging the optical element 21, the apparatus is operated under conditions that make sputtering difficult. Also, if the contamination of the optical element 21 exceeds an allowable level, it is possible to etch and clean the contaminated surface by deliberately setting the pressure to perform sputtering.

[0220] The sputtering rate can also be adjusted by increasing or decreasing the emission output (light amount of EUV light 1) in the first vacuum chamber 10. Also, it is possible to improve unevenness in sputtering by changing the position and attitude of the optical element 21. It is also possible to place a shield in front of the optical element 21 to limit the area to be sputtered.

[0221] As the ionized gas that generates this sputtering phenomenon, a rare gas (typically argon gas) that has relatively little absorption of the EUV light 1 is used. In other words, the ionized gas can be used as the buffer gas 2 because it hardly reduces the amount of light of the EUV light 1. Conversely, a gas that can be used as the buffer gas 2 can be used as the ionized gas that generates sputtering. This eliminates the need to prepare a dedicated gas for cleaning optical elements, etc., making it possible to simplify the system configuration and reduce equipment costs and running costs.

[0222] For example, one method for cleaning the optical system of the EUV light 1 is to perform chemical cleaning using a highly explosive gas or a highly reactive gas. For example, in Patent Document 2, in an extreme ultraviolet light source using metal vapor, reactive gases such as hydrogen gas or halogen gas are supplied to the foil trap or downstream thereafter. The reactive gas is then excited using vacuum ultraviolet light generated from the light source or ultraviolet light generated from a dedicated ultraviolet light source, and the optical elements are cleaned.

[0223] However, hydrogen gas is explosive and therefore dangerous to use. In addition, halogen gas is highly reactive and difficult to handle. For this reason, in order to ensure the safety of the equipment and the corrosion resistance of the equipment container, operation by experts and the cost of equipment are required. For example, in order to exhaust reactive gases safely and without adversely affecting the equipment, it is necessary to install a device to treat the reactive gas before the exhaust device. In addition, the components installed inside the light source and the equipment used are corroded by the reactive gas. For this reason, it is necessary to maintain the inside of the equipment against corrosion and to use materials and coatings that are resistant to corrosion by reactive gases.

[0224] Furthermore, Japanese Patent Application Laid-Open No. 2007-13054 describes a method for cleaning an optical system using an inert gas in a projection exposure apparatus equipped with an EUV light source. This method involves cooling an inert gas such as nitrogen gas, spraying the liquid or solid inert gas onto optical elements, and cleaning contaminants that have adhered to the optical elements due to the impact.

[0225] However, in order to turn nitrogen gas into a liquid or solid, it is necessary to cool it to at least -50°C or lower, which requires a huge amount of liquid nitrogen or other cooling medium. In addition, in extreme ultraviolet light sources that use metal vapor, it is possible that the metal flying from the light source will be cooled and solidified at low temperature locations. If the metal solidifies in this way, it will have various adverse effects on the optical path and the components installed inside the light source. In addition, when vaporized metal is cooled, it may generate tiny metal particles. If such metal particles enter the vacuum exhaust system, they can be a factor in significantly shortening the life of the exhaust system.

[0226] In contrast, the sputtering phenomenon discovered by the present inventors allows sputtering (etching) with an inert ionized gas (buffer gas 2) such as a rare gas. In this way, since an inert gas is used, a light source device 100 that can be operated safely can be realized. Furthermore, the light source device 100 does not require a mechanism for processing the reactive gas or a mechanism for removing the reactive gas. Therefore, compared to devices that use reactive gases, it is possible to significantly reduce the cost of the device. Furthermore, the device configuration is simplified, and the device can be configured compactly. Furthermore, ionized gas does not cause corrosion like active gas. Therefore, the range of materials to be selected for the container, etc. is relatively wide, making it possible to reduce the cost of the device.

[0227] Also, unlike methods that use cooled inert gas, there is no need to install cooling equipment to turn the ionized gas into a liquid or solid, which reduces the cost of the device and simplifies the device configuration. In addition, there are no parts in the device that become extremely cold, so there are no problems such as concentrated solidification of metals such as tin, or an increase in metal particles that affect the exhaust system.

[0228] As described above, the ionized gas can be a gas that has low absorption of the EUV light 1. This makes it possible to clean the members downstream of the debris mitigation device 40 without attenuating the EUV light 1. As a result, for example, a relatively high sputtering rate can be achieved, and cleaning can be completed in a short time.

[0229] <Other embodiments> The present invention is not limited to the above-described embodiment, and various other embodiments can be realized.

[0230] In the above embodiment, an LDP type light source unit is used to generate plasma from the plasma raw material by the laser beam LB and discharge. The type of light source unit is not limited, and any type may be used as long as it is a type that generates radiant light from plasma.

[0231] Fig. 22 is a schematic diagram showing an example of the configuration of an LPP type light source section. Fig. 22 shows a schematic diagram of an LPP type light source section 80 that directly converts plasma raw materials into plasma using a laser beam LB. The light source section 80 has a rotor 81 arranged in the first vacuum chamber 10, a container C that supplies plasma raw materials S to the rotor 81, and a laser source 82 that irradiates a laser beam LB that converts the plasma raw materials S supplied to the rotor 81 into plasma. In the light source section 80, the container C corresponds to the raw material supply section, and the laser source 82 corresponds to the energy beam incidence section.

[0232] The rotor 81 transports the plasma raw material S to a region where the plasma P is generated. Here, the main surface of the disk-shaped rotor 81 is irradiated with a laser beam LB. This irradiation position is the position where the plasma P is generated. As shown in FIG. 22, the rotor 81 is supported so as to be rotatable along the vertical direction. The rotor 81 may be disposed in a state inclined from the vertical direction. The shape of the rotor 81 is not limited to a disk shape, and a rotor having a polygonal shape, for example, may be used. The rotor 81 is formed using a high-melting point metal such as tungsten (W), molybdenum (Mo), or tantalum (Ta).

[0233] The container C is provided so that the lower part of the rotor 81 is immersed therein, and supplies liquid plasma raw materials S to the rotor 81. For example, the plasma raw materials S contained in the container C adhere to the surface of the rotor 81. As the rotor 81 rotates in this state, the plasma raw materials S are supplied to the irradiation position of the laser beam LB. Then, as the laser beam LB is incident on the irradiation position, plasma P is generated and radiation such as EUV light is emitted.

[0234] In this way, the light source unit 80 of the type in which a part of the rotor 81 is immersed in the container C can, for example, reduce the thickness of the light source module. Also, unlike the light source unit of the LDP type described with reference to Fig. 1, the LPP type requires only one rotor and does not require any equipment for supplying pulsed power. This makes it possible to miniaturize the device and reduce the cost of the device.

[0235] Fig. 23 is a schematic diagram showing another example of the configuration of an LPP-type light source section. The light source section 90 shown in Fig. 23 is provided in the first vacuum chamber 10, and is provided with a rotating drum 91 that rotates while storing liquid plasma raw material S. The light source section 90 is an LPP-type light source module that converts the plasma raw material S stored in the rotating drum 91 into plasma by a laser beam LB.

[0236] The rotating drum 91 has a storage section 92 that is open upward and stores liquid plasma raw material S. The plasma raw material S is supplied to the storage section 92 in a liquid or solid state from a raw material supply section (not shown). The rotating drum 91 is also provided with a heating mechanism (not shown) to maintain the plasma raw material S supplied to the storage section 92 in a liquid state. The heating mechanism used is a heater that directly heats the rotating drum 91 using an electric heating wire or the like. Alternatively, a heater that heats the rotating drum 91 from the outside using radiation or the like may be used.

[0237] Rotating drum 91 has a disk-shaped base body 93 and an annular outer wall portion 94 formed on one surface of base body 93 along the periphery of base body 93. In rotating drum 91, the area surrounded by base body 93 and outer wall portion 94 becomes storage portion 92 that stores liquid plasma raw material S. A shaft member 95 that rotates about a predetermined rotation axis is connected to the surface of rotating drum 91 opposite to the surface on which storage portion 92 is formed, so that the central axis of rotating drum 91 coincides with the rotation axis. Shaft member 95 is rotated by a motor (not shown).

[0238] When rotating drum 91 is rotated continuously about its axis of rotation, the liquid plasma raw material S supplied to storage section 92 moves by centrifugal force toward inner circumferential surface 94a of outer wall section 94, and is distributed along inner circumferential surface 94a. The film thickness of the liquid plasma raw material S distributed on inner circumferential surface 94a is adjusted according to the rotation speed of the rotor.

[0239] In this way, the rotating drum 91 stores the liquid plasma raw material S on the inner circumferential surface 94a of the storage section 92. The inner circumferential surface 94a of the storage section 92 is irradiated with a laser beam LB which converts the liquid plasma raw material S into plasma. This generates plasma P at the position irradiated by the laser beam LB, and radiant light such as EUV light is emitted. In a light source section 90 of the type which uses the rotating drum 91 as the rotating body, there is no need to provide, for example, a container for storing a large amount of plasma raw material. This makes it possible to reduce the power required to heat the plasma raw material.

[0240] In the above embodiment, the debris mitigation device including both the rotating foil trap and the fixed foil trap has been described. The configuration of the debris mitigation device is not limited, and any configuration may be used as long as it is capable of generating a high pressure region to interrupt the vacuum path formed in the device.

[0241] For example, instead of a fixed foil trap, other members that reduce conductance may be used as the member disposed on the second vacuum chamber side of the debris mitigation device. For example, a member that reduces conductance by using a mesh structure or honeycomb structure may be used. In addition, when the beam diameter of the EUV light is small, a member that reduces conductance by narrowing the vacuum path may be used.

[0242] For example, the rotary foil trap and the rotary foil trap cover do not need to be arranged on the first vacuum chamber side of the debris mitigation device. In this case, by providing a cylindrical member that abruptly widens the cross section intersecting the path direction, such as the rotary foil trap cover, it is possible to maintain a high pressure region.

[0243] In the above embodiment, the buffer gas is used as the ionized gas that generates sputtering. However, the present invention is not limited to this, and the buffer gas and the ionized gas may be different types of gas.

[0244] For example, an inert gas such as nitrogen or helium may be used as the buffer gas, and a rare gas such as argon gas may be used as the ionized gas. In this case, for example, during normal operation, a high pressure region or the like may be generated with the buffer gas (nitrogen, helium, etc.), and an ionized gas (argon, etc.) may be released into the second vacuum chamber only when a cleaning operation is performed. Even in this configuration in which the ionized gas is introduced only when necessary, it is possible to clean optical elements, etc. by utilizing sputtering with the ionized gas.

[0245] In the light source device 100 described with reference to Figures 1 and 2 etc., the debris reduction device 30 is provided inside the first vacuum chamber 10. The location where the debris reduction device is provided is not limited. For example, the debris reduction device may be provided outside the first vacuum chamber and the second vacuum chamber. In this case, the debris reduction device is provided so as to connect the outer wall of the first vacuum chamber and the outer wall of the second vacuum chamber. The debris reduction device may also be provided inside the second vacuum chamber.

[0246] In the above embodiment, a method for performing sputtering using radiation from plasma and ionized gas has been described using a light source device equipped with a debris reduction device that generates a high-pressure region on a vacuum path, but the configuration of the device for performing sputtering using radiation and ionized gas is not limited.

[0247] For example, in a light source device, the debris reduction device does not necessarily need to form a vacuum path. In this case, the vacuum path connecting the space where plasma is generated (first vacuum chamber) and the space where the synchrotron radiation is introduced (second vacuum chamber) is formed of a separate member from the debris reduction device. The debris reduction device is appropriately disposed on the optical path of the synchrotron radiation. Even with such a light source device, it is possible to perform sputtering using the synchrotron radiation and the ionized gas by releasing an ionized gas into the space where the synchrotron radiation is introduced.

[0248] In addition, the configuration of the light source device for performing sputtering and the configuration of the debris reduction device mounted on the light source device are not limited, and for example, the above-mentioned sputtering phenomenon can be generated using any device capable of releasing ionized gas into the area irradiated with synchrotron radiation.

[0249] In this disclosure, expressions using "more than", such as "greater than A" and "smaller than A", are expressions that comprehensively include both concepts that include equivalent to A and concepts that do not include equivalent to A. For example, "greater than A" is not limited to cases that do not include equivalent to A, but also includes "A or greater." Furthermore, "smaller than A" is not limited to "less than A" but also includes "A or less." When implementing the present technology, specific settings and the like may be appropriately adopted from the concepts included in "greater than A" and "smaller than A" so as to achieve the effects described above.

[0250] It is also possible to combine at least two of the characteristic parts of the present technology described above. That is, the various characteristic parts described in each embodiment may be arbitrarily combined without distinction between the embodiments. In addition, the various effects described above are merely examples and are not limited thereto, and other effects may be exhibited. [Explanation of symbols]

[0251] P: Plasma 1...EUV light 2. Buffer gas 10...First vacuum chamber 13...Vacuum path 14…High pressure area 20...Second vacuum chamber 21...Optical element 30, 80, 90...Light source section 40…Debris reduction device 41...Cylindrical member 42…Conductance reduction section 44…Rotating foil trap cover 45…Fixed foil trap 47...Entrance 100…Light source device

Claims

1. a first vacuum chamber; a light source unit that generates plasma serving as a light source in the first vacuum chamber; a debris reduction apparatus for reducing debris dispersed from the plasma, the debris reduction apparatus forming a vacuum path connecting the first vacuum chamber and a second vacuum chamber into which radiation light emitted from the plasma is introduced and through which the radiation light passes, and generating a high-pressure region in which a pressure is higher than a pressure in the first vacuum chamber and a pressure in the second vacuum chamber so as to interrupt the vacuum path; A light source device comprising:

2. The light source device according to claim 1 , The debris mitigation apparatus includes a conductance reduction section that reduces the conductance of the vacuum path between the high pressure region and the second vacuum chamber. Light source device.

3. The light source device according to claim 2 , The conductance reducing unit is a fixed foil trap having a plurality of foils arranged in the vacuum path and a fixing member that fixes the plurality of foils. Light source device.

4. The light source device according to claim 1 , The debris mitigation device is provided between the high pressure region and the first vacuum chamber, and has a cylindrical member whose cross section intersecting with a path direction of the vacuum path is larger than that of the high pressure region. Light source device.

5. The light source device according to claim 4, The debris mitigation device includes a rotary foil trap having a plurality of foils and a rotating member that radially supports the plurality of foils; The cylindrical member is a rotary foil trap cover that surrounds the rotary foil trap. Light source device.

6. The light source device according to claim 1 , The debris mitigation apparatus prevents the pressure in the first vacuum chamber from substantially changing when the pressure in the second vacuum chamber changes at least within a range equal to or less than the pressure in the high pressure region. Light source device.

7. The light source device according to claim 1 , The pressure in the high pressure region is six times or more the pressure in the first vacuum chamber. Light source device.

8. The light source device according to claim 1 , further comprising: The apparatus further includes an inlet for introducing a buffer gas that changes the pressure in the second vacuum chamber, and a pressure adjustment mechanism for adjusting the pressure in the second vacuum chamber. Light source device.

9. The light source device according to claim 8, the high pressure region is a region into which the buffer gas is introduced, The inlets include a first inlet leading to the high pressure region. Light source device.

10. The light source device according to claim 8, further comprising: The second vacuum chamber includes: The inlet includes a second inlet provided in the second vacuum chamber. Light source device.

11. The light source device according to any one of claims 1 to 10, the buffer gas is an ionized gas that is ionized by the synchrotron radiation, The light source device is capable of normal operation and cleaning operation using the ionized gas. Light source device.

12. The light source device according to claim 11, The cleaning operation is an operation in which the ionized gas is introduced into a second vacuum chamber maintained at a first pressure that is a pressure during normal operation, the pressure of the second vacuum chamber is increased to a second pressure higher than the first pressure, and a target placed in the second vacuum chamber is sputtered with the ionized gas ionized by the synchrotron radiation while the second pressure is maintained. Light source device.

13. The light source device according to claim 12, The second pressure is 6 Pa or more. Light source device.

14. The light source device according to claim 12, a pressure of the first vacuum chamber during normal operation is set to a third pressure at which the radiation is stable; and The second pressure is at least three times the third pressure. Light source device.

15. The light source device according to claim 11, The ionized gas is a rare gas. Light source device.

16. The light source device according to claim 11, further comprising: the second vacuum chamber; and a light amount monitor provided in the second vacuum chamber and configured to detect an amount of the radiation light, The normal operation and the cleaning operation are switched and executed based on the detection result of the light amount monitor. Light source device.

17. The light source device according to claim 8, The pressure adjustment mechanism is at least one of a flow rate adjustment valve that adjusts the flow rate of the buffer gas introduced from the inlet, or an exhaust amount adjustment valve that adjusts the exhaust amount of the second vacuum chamber. Light source device.

18. The light source device according to claim 1 , The radiation is EUV light. Light source device.

19. The light source device according to claim 1 , The light source unit includes: A pair of rotating electrodes disposed in the first vacuum chamber with a discharge region therebetween; a raw material supply unit for supplying a plasma raw material to the pair of rotating electrodes; an energy beam injection unit that injects an energy beam that vaporizes the plasma raw material onto a portion of one of the pair of rotating electrodes that faces the discharge region; a voltage source that applies a voltage to the pair of rotating electrodes to convert the plasma raw material vaporized by the energy beam into plasma. Light source device.

20. The light source device according to claim 1 , The light source unit includes: a rotor disposed in the first vacuum chamber; A raw material supply unit that supplies a plasma raw material to the rotor; an energy beam injection unit that injects an energy beam into the rotating body to convert the plasma raw material supplied to the rotating body into plasma; Light source device.

21. A cleaning method performed using a light source device, comprising: The light source device is a first vacuum chamber; a light source unit that generates plasma serving as a light source in the first vacuum chamber; a debris mitigation apparatus for reducing debris dispersed from the plasma, the debris mitigation apparatus comprising: a first vacuum chamber and a second vacuum chamber into which radiation light emitted from the plasma is introduced, forming a vacuum path through which the radiation light passes, and generating a high-pressure region having a pressure higher than that of the first vacuum chamber and that of the second vacuum chamber so as to interrupt the vacuum path; a pressure increasing step of introducing an ionized gas that is ionized by the radiation into a second vacuum chamber that is maintained at a first pressure that is a pressure during normal operation while the plasma is being generated, and increasing the pressure of the second vacuum chamber to a second pressure that is higher than the first pressure; a sputtering step of performing sputtering on a target disposed in the second vacuum chamber with the ionized gas ionized by the synchrotron radiation while maintaining the second pressure; A cleaning method comprising:

22. 22. The cleaning method according to claim 21, the light source device further includes the second vacuum chamber and a light amount monitor provided in the second vacuum chamber and configured to detect an amount of the emitted light, When the amount of light detected by the light amount monitor becomes lower than a first threshold, the pressure increasing step and the sputtering step are performed; The method further includes a pressure reducing step of reducing the pressure in the second vacuum chamber to the first pressure when the amount of light detected by the light amount monitor becomes higher than a second threshold value that is equal to or higher than the first threshold value. Cleaning method:

23. 22. The light source device according to claim 21, The sputtering step includes a step of changing an amount of the synchrotron radiation from an amount of the synchrotron radiation during the normal operation while maintaining the second pressure. Cleaning method:

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