Storage capacity estimation method, storage capacity estimation device and program

Abstract

To estimate a contained amount of a to-be-contained object while eliminating the need to measure a liquid level even when the to-be-contained object contained in a debris-containing container is maintained in a liquid phase.SOLUTION: A contained amount estimation method includes the steps of: controlling temperature of a container so that the temperature of the container, which contains a to-be-contained object, converges; and estimating a contained amount of the container on the basis of characteristics of vibration data of vibration accompanying the temperature control.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a capacity estimation method, a capacity estimation device, and a capacity estimation program. [Background technology]

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

[0003] There are several known methods for generating EUV light (EUV radiation) in EUV light source devices. One of these methods is to generate plasma by heating and exciting extreme ultraviolet radiation species (hereinafter also referred to as EUV radiation species), and extract the EUV light from the plasma.

[0004] EUV light source devices that employ this method are divided into an LPP (Laser Produced Plasma) type and a DPP (Discharge Produced Plasma) type depending on the plasma generation method.

[0005] The DPP-type EUV light source device applies a high voltage to the gap between electrodes to which a discharge gas containing an EUV radiation species (gas-phase plasma raw material) is supplied, generates high-density plasma by discharge, and utilizes the extreme ultraviolet light emitted from the plasma. As the DPP method, for example, as described in Patent Document 1, a method has been proposed in which liquid plasma raw material (e.g., tin (Sn) or lithium (Li)) is supplied to the electrode surface that generates the discharge, the raw material is irradiated with an energy beam such as a laser beam to vaporize the raw material, and then plasma is generated by discharge. This type of method is sometimes called the LDP (Laser Assisted Discharge Plasma) method.

[0006] On the other hand, an LPP type EUV light source device irradiates a target material with laser light and excites the target material to generate plasma.

[0007] The EUV light source device is used as a light source device for a lithography apparatus in semiconductor device manufacturing. Alternatively, the EUV light source device is used as a light source device for an inspection apparatus for a mask used in lithography. In other words, the EUV light source device is used as a light source device for other optical system devices (utilization devices) that utilize EUV light.

[0008] Since EUV light is significantly attenuated in the atmosphere, the spatial region through which the EUV light passes from the plasma to the utilization device is placed in a reduced pressure atmosphere, i.e., a vacuum environment, in order to suppress the attenuation of the EUV light.

[0009] On the other hand, in an EUV light source device, debris is emitted from the plasma at high speed. The debris includes particles of the plasma raw material (tin particles when the plasma raw material is tin). When plasma is generated by the DPP method or the LDP method, the debris includes particles of the material of the discharge electrode that is sputtered with the generation of plasma.

[0010] When debris reaches a utilization device, it may damage or contaminate the reflective film of an optical element in the utilization device, thereby degrading its performance. Therefore, a debris mitigation tool (also called DMT (Debris Mitigation Tool)) has been proposed to capture the scattered debris so that the debris does not enter the utilization device (Patent Document 1).

[0011] At least a portion of the debris captured by the debris mitigation device is heated so as to melt by the heating means, and collects at the bottom of the cover member due to gravity, and is discharged from the bottom of the cover member through a discharge pipe to outside the cover member, becoming waste raw material.

[0012] The waste material (debris) discharged outside the cover member through the discharge pipe is stored in a debris collection container (Tin Dump), which is a storage unit for the waste material (tin). The debris collection container is provided with a heating unit that heats the debris collection container to a temperature above the melting point of the plasma raw material. In other words, the waste material received by the debris collection container is immediately melted and stored in the debris collection container in a liquefied state.

[0013] In addition, a heat shield is placed between the debris mitigation device and the plasma. When the debris that accumulates on the heat shield reaches a certain amount, it turns into droplets and collects and falls below the heat shield due to gravity. By placing a debris container at the position where the debris falls from the heat shield, the debris that breaks off from the heat shield is stored in the debris container.

[0014] In addition, in an LDP-type EUV light source device, some of the plasma raw material (tin) supplied to the discharge part (discharge electrode, etc.) may leak. Such leaked raw material does not contribute to plasma generation and becomes waste raw material. The leaked raw material is collected, for example, by an enclosure member that surrounds the discharge part, and is stored in a debris container in the same way as the debris. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] JP 2017-219698 A [Patent Document 2] Patent No. 6241407 [Patent Document 3] US Patent Application Publication No. 2015 / 0090907 Summary of the Invention [Problem to be solved by the invention]

[0016] The debris container is removably attached to the EUV light source device main body. During maintenance of the EUV light source device, heating of the debris container is stopped, the contents (debris and waste raw materials) stored in the debris container are solidified, and the debris container containing the contents is replaced with an empty debris container. Alternatively, after removing the debris container containing the solidified contents, the debris container is heated to remove the contents, and the empty debris container is reattached to the EUV light source device main body.

[0017] As described above, the debris collection container contains the debris collected by the debris mitigation device, the debris detached from the heat shield, and the scattered raw material from the discharge part. Therefore, as the operating time of the EUV light source device increases, the amount of debris and waste raw material contained in the debris collection device increases.

[0018] If the contents of the debris container exceed its maximum capacity, the contents may overflow into the space in which the debris container of the EUV light source device is installed and communicates with the debris container, causing malfunctions in other components in that space. To avoid such a situation, it is necessary to monitor the amount of contents contained in the debris container.

[0019] As described above, when the EUV light source device is in operation, the debris container is heated by the heating unit to a temperature equal to or higher than the melting point of the plasma raw material (tin), so the contents including the debris and waste raw material are stored in the debris container in a liquefied state. At this time, a method of sensing the liquid level of the liquid contents may be used to monitor the amount of contents stored in the debris container.

[0020] As described in Patent Document 2, for example, electrical sensing of the liquid level of the contained material can be achieved by utilizing the fact that the debris container is generally made of conductive materials such as metal, and that the contained material, such as tin, is conductive. That is, a metal rod (electrode) that serves as the sensing unit is installed inside the debris container that contains the tin, and the liquid level is detected based on the presence or absence of current flow between the metal rod and the debris container. Such electrode-type liquid level sensors have a high detection responsiveness because they are configured to detect the electrical open / closed state of the circuit.

[0021] Alternatively, a temperature sensor that detects the tin liquid level by temperature change, or a laser displacement meter that detects the tin liquid level by reflection of laser light can also be used.

[0022] However, the debris container is removed during maintenance of the EUV light source device or when the amount of the contained material exceeds a predetermined level. When the liquid level is sensed using a metal rod, the metal rod is in contact with the liquid surface of the contained material or is partially immersed in the contained material when the liquid level is detected.

[0023] The debris container is removed when heating of the debris container is stopped and the contents contained in the debris container are solidified. Therefore, the metal rod is fixed by the solidified contents. Therefore, when removing the debris container, the metal rod for sensing the liquid level must also be removed from the EUV light source device. In addition, even after removing the debris container and the metal rod from the EUV light source device, it is necessary to separate the metal rod from the solidified tin and attach it again to the EUV light source device. Therefore, it takes time to attach and detach the debris container to and from the EUV light source device.

[0024] The temperature sensor in Patent Document 2 detects the liquid level from temperature information when the sensing part is immersed in the plasma raw material and temperature information when it is not immersed, so the same problems occur as with the metal rod.

[0025] Patent Document 3 discloses a method for estimating the amount of contents contained in a debris container without sensing the liquid level of the liquid contents. As mentioned above, in order to keep the contents, which are mostly tin, in a liquid state, the debris container is heated so that the temperature of the contents inside is above the melting point of tin (approximately 232°C). Here, when a debris container containing a certain volume of debris is heated from a temperature equivalent to room temperature to a target temperature (e.g., 270°C), a plateau period (a period during which the temperature is almost constant) occurs before the temperature of the debris container gradually increases from a temperature equivalent to room temperature and reaches the target temperature. Furthermore, when temperature control for maintaining a debris container containing a certain volume of debris at a target temperature is stopped, a plateau period occurs before the temperature of the debris container gradually decreases from the target temperature and reaches a temperature equivalent to room temperature.

[0026] This plateau period corresponds to a phase change of the debris contained in the debris container. That is, if the debris container is heated to a target temperature and maintained at that temperature, the plateau period corresponds to the time for the debris to change from a solid phase to a liquid phase. Similarly, if the temperature control of the debris container to maintain the target temperature is stopped, the plateau period corresponds to the time for the debris to change from a liquid phase to a solid phase.

[0027] The plateau period depends on the volume of the contents, so by calculating correlation data between the volume of debris and the plateau period in advance, measuring the plateau period, and comparing the measurement result with the correlation data calculated in advance, it is possible to estimate the amount of debris contained in the debris container.

[0028] However, since this method of estimating the capacity of the contained material utilizes the time it takes for the phase to change between the liquid phase and the solid phase, this method can only be adopted at the start or end of operation of the EUV light source device. While the EUV light source device is operating, the temperature of the debris container is maintained near the target temperature. Therefore, the debris in the debris container maintains a liquid state, and no phase change occurs between liquid and solid, so no plateau period occurs. In other words, while the EUV light source device is operating, the amount of material contained in the debris container cannot be estimated using the method for estimating the material volume using the plateau period.

[0029] The amount of material contained in the debris container depends on the operating time (continuous operation time) of the EUV light source device. In other words, as the operating time of the EUV light source device becomes longer, the amount of material contained in the debris container becomes larger. Therefore, if the operating time of the EUV light source device becomes long, the amount of material contained in the debris container may exceed the allowable value (threshold value). In this case, the method of estimating the amount of material contained in the debris container using the plateau period cannot estimate the amount of material contained while the EUV light source device is operating, and therefore cannot detect that the amount of material contained in the debris container has exceeded the allowable value while the EUV light source device is operating.

[0030] Therefore, an object of the present invention is to provide a storage capacity estimation method, a storage capacity estimation device, and a program that are capable of estimating the capacity of a debris container without the need to measure the liquid level, even when the contents stored in the debris container are maintained in a liquid phase state. [Means for solving the problem]

[0031] A capacity estimation method according to one aspect of the present invention includes a step of temperature controlling a storage container containing liquefied contents so that the temperature of the storage container converges, and a step of estimating the capacity of the contents contained in the storage container based on characteristics of vibration data that vibrates in conjunction with the temperature control.

[0032] Thus, by using data from the temperature control system that causes the temperature of the storage container to converge, the amount of the contents stored in the storage container can be estimated. At this time, the temperature control system can control the temperature of the storage container so that the temperature of the storage container converges, regardless of whether or not there is a phase change between the liquid phase and the solid phase of the contents stored in the storage container. Therefore, even when the contents stored in the storage container are maintained in a liquid phase state, the amount of the contents can be estimated without needing to measure the liquid level. As a result, even when the device that generates the contents is in operation, the amount of the contents can be estimated without immersing a temperature sensor or a metal rod in the contents in the storage container, making it possible to prevent the contents from overflowing from the storage container and to efficiently replace the storage container in which the contents are stored.

[0033] In addition, according to a capacity estimation method of one aspect of the present invention, the characteristics of the vibration data may be selected from at least one of the amplitude, frequency, and phase of the temperature vibration of the storage container when temperature control is performed so that the temperature of the storage container becomes a target temperature.

[0034] This makes it possible to estimate the amount of contents contained in the storage container based on the temperature measurement results, and makes it possible to prevent the contents from overflowing from the storage container without the need to measure the liquid level even when the device generating the contents is in operation.

[0035] In addition, according to a capacity estimation method according to one aspect of the present invention, the characteristics of the vibration data may be selected from at least one of an amplitude, a frequency, and a phase of a duty oscillation in PWM (Pulse Width Modulation) control when controlling the temperature of the storage container.

[0036] This makes it possible to estimate the amount of stored contents based on command values ​​for controlling the temperature of the storage container, and makes it possible to prevent the contents from overflowing from the storage container without the need to measure the liquid level even when the device generating the contents is in operation.

[0037] In addition, according to the storage capacity estimation method according to one aspect of the present invention, the characteristics of the vibration data change based on the storage capacity of the items stored in the storage container.

[0038] This makes it possible to estimate the capacity of the contained items based on changes in the characteristics of the vibration data, eliminating the need to develop a complex algorithm for estimating the capacity of the contained items.

[0039] In addition, a capacity estimation method according to one aspect of the present invention may include a step of collecting amplitude data of temperature vibration corresponding to the capacity of the stored items when the temperature of the storage container reaches a target temperature, a step of storing correlation data between the collected amplitude data and the capacity of the stored items, a step of collecting time-varying characteristics of the temperature of the storage container when the temperature is controlled under the same temperature control conditions as when the correlation data was collected, a step of calculating an amplitude of the temperature vibration from the collected time-varying characteristics of the temperature of the storage container after the temperature of the storage container reaches the target temperature, and a step of comparing the calculated amplitude with the amplitude of the correlation data, and setting the capacity associated with the amplitude of the correlation data corresponding to the calculated amplitude as an estimate of the capacity.

[0040] This allows the amount of the contained items to be estimated based on the comparison results of the amplitude data of the temperature vibrations collected during the temperature control of the storage container, making it unnecessary to construct a complex algorithm for estimating the amount of the contained items. In addition, the temperature sensor used for the temperature control of the storage container can be used to estimate the amount of the contained items, making it unnecessary to provide a separate temperature sensor for estimating the amount of the contained items, thereby suppressing an increase in resources required for estimating the amount of the contained items.

[0041] In addition, a capacity estimation method according to one aspect of the present invention may include a step of estimating the capacity of the contents in the storage container, then comparing the estimated value of the capacity of the contents with a threshold value, and a step of sending a warning signal to the outside if the estimated value of the capacity of the contents is equal to or greater than the threshold value.

[0042] This makes it possible to notify the outside of the state of the contents before they overflow from the storage container, and provides information on when to replace the storage container containing the contents.

[0043] In addition, according to a storage capacity estimation method according to one aspect of the present invention, if the estimated amount of the storage capacity of the stored items is smaller than the threshold value, the method may proceed to a step of acquiring a time-varying characteristic of the temperature of the storage container.

[0044] This allows the estimation of the capacity of the contents to be repeated if there is space remaining in the storage container to accommodate additional contents, and allows the estimation of the capacity of the contents to be continued until just before there is no more space left to accommodate additional contents.

[0045] In addition, a capacity estimation method according to one embodiment of the present invention may be applied to estimating the capacity of the liquid metal in a metal containing device comprising a container for containing liquid metal as the contained item, a heating means for heating the container, a temperature measuring means for measuring the temperature of the container, a power supplying means for supplying power to the heating means, and a control unit for controlling the power supplying means based on temperature information from the temperature measuring means so that the temperature of the container becomes a target temperature.

[0046] This makes it possible to store the liquid metal in the storage vessel while maintaining the liquid phase, and to estimate the amount of the stored contents, a temperature measuring means for measuring the temperature of the storage vessel and a control unit for controlling the power supply means can be used. Therefore, it is possible to estimate the amount of the stored contents based on data obtained during temperature control to set the temperature of the storage vessel to a target temperature while suppressing an increase in resources required for estimating the amount of the stored contents.

[0047] Furthermore, a storage amount estimation method according to one aspect of the present invention may be applied to estimation of the amount of debris stored in a storage container in an extreme ultraviolet light source device comprising: a light source unit that excites a plasma raw material containing a metal to generate plasma that radiates extreme ultraviolet light; a storage container that contains debris containing metal dissipated from the plasma; a heating means that heats the storage container; a temperature measuring means that measures the temperature of the storage container; a power supplying means that supplies power to the heating means; and a control unit that controls the power supplying means based on temperature information from the temperature measuring means so that the temperature of the storage container becomes a target temperature.

[0048] This makes it possible to store metal-containing debris dispersed from the plasma in a liquid state in the storage container, and to estimate the amount of stored debris, a temperature measuring means for measuring the temperature of the storage container and a control unit for controlling the power supply means can be used. This makes it possible to suppress an increase in resources required for estimating the amount of stored debris, and also makes it possible to estimate the amount of stored debris based on data obtained during temperature control to set the temperature of the storage container to a target temperature, providing information for determining when to replace a storage container containing debris even when the light source unit is in operation.

[0049] In addition, a capacity estimation device according to one embodiment of the present invention includes a temperature control unit that controls the temperature of a storage container containing liquefied contents so that the temperature of the storage container converges, and a capacity estimation unit that estimates the capacity of the contents contained in the storage container based on characteristics of vibration data that vibrates in response to the temperature control.

[0050] This makes it possible to estimate the amount of contents contained in the storage container by using data from a temperature control system that converges the temperature of the storage container, and makes it possible to prevent the contents from overflowing from the storage container without the need to measure the liquid level even when the device generating the contents is in operation.

[0051] In addition, a program according to one aspect of the present invention causes a computer to execute the steps of temperature controlling a storage container containing liquefied contents so that the temperature of the storage container converges, and estimating the capacity of the contents contained in the storage container based on characteristics of vibration data that vibrates in conjunction with the temperature control.

[0052] In this way, the capacity of the contents stored in the storage container can be estimated by having a computer execute the capacity estimation program, which eliminates the need for dedicated hardware for estimating the capacity of the contents stored in the storage container and makes it easier to implement the capacity estimation function. Effect of the Invention

[0053] In one aspect of the present invention, even when the contents contained in the debris container are maintained in a liquid phase state, the amount of the contents can be estimated without the need to measure the liquid level. [Brief description of the drawings]

[0054] [Figure 1] 2 is a cross-sectional view showing the inside of a chamber and the inside of a connecting chamber of the extreme ultraviolet light source device according to the embodiment, cut in the horizontal direction. FIG. [Diagram 2] 2 is a cross-sectional view showing a schematic configuration of a debris reduction unit and a debris storage unit according to an embodiment of the present invention. FIG. [Diagram 3] FIG. 3 is a front view showing a configuration example of the rotary foil trap shown in FIG. 2. [Figure 4] FIG. 3 is a top view showing a configuration example of the fixed foil trap shown in FIG. 2. [Diagram 5] FIG. 3 is a cross-sectional view showing a configuration example of the fixed foil trap in FIG. 2. [Figure 6] FIG. 3 is a perspective view showing a configuration example of the debris container in FIG. 2. [Figure 7] 3 is a cross-sectional view showing an example of the configuration of the debris container in FIG. 2. [Figure 8] FIG. 3 is a block diagram showing an example of a temperature control system for the heat treatment of the debris container in FIG. 2. [Figure 9] FIG. 3 is a diagram showing an example of temperature change according to the amount of stored items in the debris container of FIG. 2. [Figure 10] 10 is a diagram showing another example of temperature change according to the amount of stored items in the debris container of FIG. 2. FIG. [Figure 11] 3 is a flowchart showing an example of a process for estimating the amount of stored items in the debris container of FIG. 2. [Figure 12] 9 is a block diagram showing an example of a hardware configuration of a control unit in FIG. 8. [Figure 13] FIG. 13 is a diagram showing an example of a learning model used for capacity estimation according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] Hereinafter, the embodiments of the present invention will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be appropriately modified or changed depending on the specifications of the device to which the present invention is applied and various conditions (conditions of use, environment of use, etc.). The technical scope of the present invention is determined by the claims, and is not limited by the individual embodiments below. Also, the drawings used in the following description may differ in scale and shape from the actual structure in order to make each configuration easier to understand.

[0056] Fig. 1 is a horizontal cross-sectional view showing the inside of a chamber and a connecting chamber of an extreme ultraviolet light source device according to an embodiment, and Fig. 2 is a cross-sectional view showing a schematic configuration of a debris reduction unit and a debris storage unit according to an embodiment. Note that in this embodiment, an LDP type extreme ultraviolet light source device (EUV light source device) is taken as an example.

[0057] 1, an EUV light source device 1 emits extreme ultraviolet light (EUV light). The wavelength of this extreme ultraviolet light is, for example, 13.5 nm. Specifically, the EUV light source device 1 irradiates liquid-phase plasma raw materials SA and SB, which are supplied to the surfaces of a pair of discharge electrodes EA and EB, respectively, with an energy beam such as a laser beam LB, thereby vaporizing the plasma raw materials SA and SB. Thereafter, plasma P is generated by discharge in a discharge region D between the discharge electrodes EA and EB. EUV light is emitted from the plasma P.

[0058] The EUV light source device 1 can be used, for example, as a light source device for a lithography device in semiconductor device manufacturing or as a light source device for an inspection device for a mask used in lithography. For example, when the EUV light source device 1 is used as a light source device for a mask inspection device, a part of the EUV light emitted from the plasma P is extracted and guided to the mask inspection device. The mask inspection device performs mask blank inspection or pattern inspection using the EUV light emitted from the EUV light source device 1 as inspection light. Here, by using the EUV light, it is possible to support a 5 to 7 nm process. The EUV light extracted from the EUV light source device 1 is defined by an opening KA provided in the heat shield 23 of FIG. 2.

[0059] 1 and 2, the EUV light source device 1 includes a light source unit 2, a debris mitigation unit 3, and a debris collection unit 4. The light source unit 2 generates EUV light based on the LDP method. The debris mitigation unit 3 captures debris that is scattered along with the EUV light emitted from the light source unit 2. The debris collection unit 4 collects debris generated by the light source unit 2 and debris captured by the debris mitigation unit 3.

[0060] The EUV light source device 1 also includes a chamber 11 that isolates the plasma P generated inside from the outside. The chamber 11 is made of a rigid body, for example, metal. The chamber 11 is a vacuum housing, and its interior is kept under a reduced pressure atmosphere in order to effectively generate a discharge for heating and exciting the plasma raw materials SA and SB and to suppress attenuation of the EUV light.

[0061] The light source unit 2 is disposed inside the chamber 11. The light source unit 2 includes a pair of discharge electrodes EA, EB. The discharge electrodes EA, EB are disk-shaped members of the same shape and size, and for example, the discharge electrode EA is used as a cathode, and the discharge electrode EB is used as an anode. The discharge electrodes EA, EB are formed of a high melting point metal such as molybdenum (Mo), tungsten (W) or tantalum (Ta). The discharge electrodes EA, EB are disposed at positions spaced apart from each other, and the peripheral portions of the discharge electrodes EA, EB are close to each other. At this time, the discharge region D in which the plasma P is generated is located in the gap between the discharge electrodes EA, EB where the peripheral portions of the discharge electrodes EA, EB are closest to each other.

[0062] By supplying power to the discharge electrodes EA, EB from the pulsed power supply unit 13, a discharge is generated in the discharge region D. The plasma raw materials SA, SB transported to the discharge region D based on the rotation of the discharge electrodes EA, EB are heated and excited by the current flowing between the discharge electrodes EA, EB during discharge, generating a plasma P that emits EUV light.

[0063] The discharge electrode EA is connected to a rotating shaft JA of the motor MA and rotates around the axis of the discharge electrode EA. The discharge electrode EB is connected to a rotating shaft JB of the motor MB and rotates around the axis of the discharge electrode EB. The motors MA and MB are disposed outside the chamber 11, and the rotating shafts JA and JB of the motors MA and MB extend from the outside to the inside of the chamber 11. A gap between the rotating shaft JA and the wall of the chamber 11 is sealed by a seal member PA, and a gap between the rotating shaft JB and the wall of the chamber 11 is sealed by a seal member PB. The seal members PA and PB are, for example, mechanical seals. Each seal member PA and PB rotatably supports the rotating shafts JA and JB while maintaining a reduced pressure atmosphere in the chamber 11. In this manner, the discharge electrodes EA, EB are driven by individual motors MA, MB via the rotary shafts JA, JB, respectively. The rotational driving of these motors MA, MB is controlled by a control unit 12.

[0064] A container CA for storing liquid-phase plasma raw material SA and a container CB for storing liquid-phase plasma raw material SB are placed inside chamber 11. Heated liquid-phase plasma raw materials SA and SB are supplied to the containers CA and CB. The liquid-phase plasma raw materials SA and SB are, for example, tin.

[0065] Container CA holds the plasma raw material SA in a liquid state so that the lower part of the discharge electrode EA is immersed in the liquid plasma raw material SA. Container CB holds the plasma raw material SB in a liquid state so that the lower part of the discharge electrode EB is immersed in the liquid plasma raw material SB. Thus, the liquid plasma raw materials SA and SB adhere to the lower parts of the discharge electrodes EA and EB. As the discharge electrodes EA and EB rotate, the liquid plasma raw materials SA and SB adhering to the lower parts of the discharge electrodes EA and EB are transported to discharge region D, where plasma P is generated.

[0066] A laser source (energy beam irradiation device) 14 is disposed outside the chamber 11. The laser source 14 irradiates the plasma raw material SA attached to the discharge electrode EA transported to the discharge region D with an energy beam, thereby vaporizing the plasma raw material SA. The laser source 14 is, for example, a Nd:YVO4 (Neodymium-doped Yttrium Orthovanadate) laser device. At this time, the laser source 14 emits a laser beam LB in the infrared region with a wavelength of 1064 nm. However, the energy beam irradiation device may be a device that emits an energy beam other than the laser beam LB, so long as it is capable of vaporizing the plasma raw material SA.

[0067] The timing of irradiation of the laser beam LB by the laser source 14 is controlled by the control unit 12. The laser beam LB emitted from the laser source 14 is guided to a movable mirror 16 via a focusing means including, for example, a focusing lens 15. The focusing means adjusts the spot diameter of the laser beam LB at the laser beam irradiation position on the discharge electrode EA. The focusing lens 15 and the movable mirror 16 are disposed outside the chamber 11.

[0068] The laser beam LB focused by the focusing lens 15 is reflected by the movable mirror 16 , passes through a transparent window 20 provided in the wall of the chamber 11 , and is irradiated onto the peripheral portion of the discharge electrode EA near the discharge region D. Here, the irradiation position of the infrared laser beam LB on the discharge electrode EA is adjusted by adjusting the attitude of the movable mirror 16. The adjustment of the attitude of the movable mirror 16 may be performed manually by an operator, or the control unit 12 may control the attitude of the movable mirror 16 based on intensity information of the EUV light from a monitoring device 43 described later. In this case, the movable mirror 16 is driven by a movable mirror driving unit not shown.

[0069] The axes of the discharge electrodes EA, EB are not parallel to make it easier to irradiate the laser beam LB to the peripheral portion of the discharge electrode EA near the discharge region D. The distance between the rotation axes JA, JB is narrower on the motor MA, MB side and wider on the discharge electrode EA, EB side. This makes it possible to move the opposing surfaces of the discharge electrodes EA, EB closer to each other while retracting the opposite side to the opposing surfaces of the discharge electrodes EA, EB from the irradiation path of the laser beam LB, making it easier to irradiate the laser beam LB to the peripheral portion of the discharge electrode EA near the discharge region D.

[0070] The discharge electrode EB is disposed between the discharge electrode EA and the movable mirror 16. The laser beam LB reflected by the movable mirror 16 passes near the outer circumferential surface of the discharge electrode EB, and then reaches the outer circumferential surface of the discharge electrode EA. At this time, the discharge electrode EB is retracted further toward the motor MB side (to the left in FIG. 1) than the discharge electrode EA so that the laser beam LB is not blocked by the discharge electrode EB. The liquid-phase plasma raw material SA attached to the outer peripheral surface of the discharge electrode EA near the discharge region D is vaporized by irradiation with the laser beam LB, and is supplied to the discharge region D as the gas-phase plasma raw material SA.

[0071] To generate plasma P in the discharge region D (to turn the gaseous plasma raw material SA into plasma), the pulsed power supply unit 13 supplies power to the discharge electrodes EA, EB. When the gaseous plasma raw material SA is supplied to the discharge region D by irradiation with the laser beam LB, a discharge is generated between the discharge electrodes EA, EB in the discharge region D. At this time, the pulsed power supply unit 13 periodically supplies pulsed power to the discharge electrodes EA, EB. The pulsed power supply unit 13 is disposed outside the chamber 11. A power feeder line extending from the pulsed power supply unit 13 passes through the feedthroughs FA and FB and extends into the chamber 11. The feedthroughs FA and FB are sealing members embedded in the wall of the chamber 11 to maintain a reduced pressure atmosphere within the chamber 11. The operation of the laser source 14 for generating the plasma P and the operation of the pulsed power supply unit 13 are controlled by the control unit 12.

[0072] Two power feed lines extending from the pulsed power supply unit 13 are connected to the containers CA and CB via feedthroughs FA and FB, respectively. The containers CA and CB are made of a conductive material, and the plasma raw materials SA and SB contained inside each container CA and CB are also made of a conductive material such as tin. The lower parts of the discharge electrodes EA and EB are immersed in the plasma raw materials SA and SB contained inside each container CA and CB, respectively. Therefore, when pulsed power is supplied from the pulsed power supply unit 13 to the containers CA and CB, the pulsed power is supplied to the discharge electrodes EA and EB via the plasma raw materials SA and SB, respectively. When a discharge occurs between the discharge electrodes EA and EB, the gas-phase plasma material SA in the discharge region D is heated and excited by the current, generating plasma P.

[0073] EUV light is emitted from the plasma P. The EUV light is utilized in a utilization apparatus (lithography apparatus or mask inspection apparatus) which is another optical system apparatus. In this embodiment, the EUV light is utilized in a mask inspection apparatus.

[0074] Between the chamber 11 and the utilization device, a connection chamber 21 is disposed. The connection chamber 21 is formed of a rigid body, for example, metal. The connection chamber 21 is a vacuum housing, and the inside thereof is also kept at a reduced pressure atmosphere in order to suppress attenuation of the EUV light, similar to the inside of the chamber 11.

[0075] The internal space of the connection chamber 21 communicates with the chamber 11 via a window portion 17, which is a through-hole formed in the wall of the chamber 11. The internal space of the connection chamber 21 also communicates with the utilization device (mask inspection device) 42 via a window portion 27, which is a through-hole formed in the wall of the connection chamber 21. Only a part of the utilization device 42 is shown in Fig. 2. The EUV light emitted from the plasma P in the discharge region D is introduced into the utilization device (mask inspection device) 42 through the windows 17, 27.

[0076] Meanwhile, debris DB is dispersed in various directions at high speed from the plasma P together with the EUV light. The debris DB includes tin particles, which are the plasma raw materials SA and SB, and material particles of the discharge electrodes EA and EB that are sputtered as the plasma P is generated. These debris DB gain large kinetic energy through the contraction and expansion processes of the plasma P. That is, the debris DB generated from the plasma P includes ions, neutral atoms, and electrons that move at high speeds, and when such debris DB reaches the utilization device 42, it may damage or contaminate the reflective coating of the optical elements in the utilization device 42, thereby degrading performance.

[0077] For this reason, a debris reduction unit 3 that captures the debris DB is provided in the connection chamber 21 to prevent the debris DB from entering the utilization device 42. The debris reduction unit 3 includes a fixed foil trap 24 in which the positions of multiple foils are fixed, and a rotating foil trap 22 in which the foil actively collides with debris. The fixed foil trap 24 is provided between the rotating foil trap 22 and the utilization device 24 on the optical path of the EUV light traveling from the connection chamber 22 to the utilization device (mask inspection device) 42. Note that in one debris reduction unit 3, both the rotating foil trap 22 and the fixed foil trap 24 may be provided, or either one of them may be provided.

[0078] FIG. 3 is a front view showing a configuration example of the rotary foil trap shown in FIG. In Fig. 3, the rotary foil trap 22 comprises a central hub 53, an outer ring 52 concentric with the hub 53, and a number of foils 51 disposed between the hub 53 and the outer ring 52. Each foil 51 is a thin film or a thin flat plate. The foils 51 are radially disposed at approximately equal angular intervals. Each foil 51 lies on a plane that includes the central axis of the hub 53. The material of the rotary foil trap 22 is, for example, a high melting point metal such as tungsten and / or molybdenum.

[0079] The multiple foils 51 of the rotary foil trap 22 are arranged parallel to the beam direction of the EUV light traveling toward the window portion 27 so as not to block the EUV light traveling from the plasma P (light emission point) toward the window portion 27. 2, the rotary foil trap 22 in which each foil 51 is disposed on a plane including the central axis of the hub 53 is disposed so that the plasma P (light emitting point) is present on an extension of the central axis of the hub 53. This allows the EUV light to be blocked only by the thickness of each foil 51, excluding the hub 53 and the outer ring 52, and makes it possible to maximize the proportion of EUV light passing through the rotary foil trap 22 (also called transmittance).

[0080] The hub 53 is connected to a rotation axis JC of a motor (rotary drive device) MC, and the central axis of the hub 53 coincides with the central axis of the rotation axis JC. In this case, the rotation axis JC of the motor MC can be regarded as the rotation axis of the rotary foil trap 22. The rotary foil trap 22 is driven to rotate by the motor MC, and the rotating foil 51 collides with the debris DB arriving from the plasma P to capture the debris DB and prevent the debris DB from entering the utilization device 42.

[0081] The rotary foil trap 22 is disposed inside the connection chamber 21, whereas the motor MC is disposed outside the connection chamber 21. A through hole through which the rotating shaft JC passes is formed in the wall of the connection chamber 21. The gap between the rotating shaft JC and the wall of the connection chamber 21 is sealed by a seal member PC made of, for example, a mechanical seal. The seal member PC rotatably supports the rotating shaft JC of the motor MC while maintaining the reduced pressure atmosphere inside the connection chamber 21.

[0082] The rotary foil trap 22 becomes hot due to radiation from the plasma P. Therefore, in order to prevent the rotary foil trap 22 from overheating, the rotary shaft JC may be made hollow to allow cooling water to flow therethrough to cool the rotary foil trap 22. In addition, since the motor MC itself generates heat during rotation, water-cooled piping 41 may be wrapped around the motor MC to remove heat. Water is flowed through the water-cooled piping 41 to cool the motor MC by heat exchange.

[0083] Further, a heat shield 23 is disposed in the connection chamber 21 in order to reduce radiation from the plasma P to the rotating foil trap 22 and to prevent overheating of the rotating foil trap 22. The heat shield 23 has an opening KA of any shape (for example, circular) for extracting a portion of the EUV light emitted from the plasma P. Since the heat shield 23 is disposed near the plasma P, it is made of a high-melting point material such as molybdenum or tungsten. The opening KA is provided at a position eccentric to the rotation axis JC of the rotary foil trap 22. At this time, a part of the EUV light emitted from the plasma P passes through the opening KA and is extracted from the heat shield 23 at a predetermined solid angle with an inclination angle with respect to the rotation axis direction of the rotary foil trap 22 (the left-right direction in FIG. 2).

[0084] The rotating foil trap 22 is disposed so that the foil 51 is positioned on the chief ray UL of the EUV light beam (hereinafter also referred to as EUV extracted light) that has passed through the opening KA of the heat shield 23. The EUV light extracted from the opening KA of the heat shield 23 passes through the debris reduction unit 3 and is introduced into the utilization device (mask inspection device) 42 via the window 27.

[0085] The rotating foil trap 22 captures relatively slow-moving debris DB among the debris DB dispersed from the plasma P, while the fixed foil trap 24 captures fast-moving debris DB among the debris DB dispersed from the plasma P that could not be captured by the rotating foil trap 22. As shown in Fig. 2, the fixed foil trap 24 is disposed on the chief ray UL of the EUV extracted light. The fixed foil trap 24 has a shape corresponding to the area through which the extracted EUV light, which is EUV light whose traveling direction is restricted by the opening KA of the heat shield 23, passes.

[0086] FIG. 4 is a top view showing an example of the configuration of the fixed foil trap of FIG. 2, and FIG. 5 is a cross-sectional view showing an example of the configuration of the fixed foil trap of FIG. 4 and 5, the fixed foil trap 24 includes a plurality of foils 61 and a fixed frame (fixed member) 60 that supports the foils 61. The foils 61 are arranged at equal intervals in a cross section perpendicular to the direction of the chief ray UL of the EUV extracted light, as shown in Fig. 5. The fixed frame 60 has, for example, a rectangular shape when viewed from the front. The outer shape of the fixed frame 60 may be any shape. The multiple foils 61 are arranged radially so as to extend in the light direction of the EUV extracted light, as shown in Fig. 4, when viewed from a direction perpendicular to the direction of the chief ray UL.

[0087] The multiple foils 61 of the fixed foil trap 24 divide the space in which the fixed foil trap 24 is disposed into small parts, thereby lowering the conductance of the parts and locally increasing the pressure. The pressure in the fixed foil trap 24 is increased by appropriately supplying gas to the fixed foil trap 24. In other words, in the connection chamber 21, gas is localized in the fixed foil trap 24 to set a part with a relatively high pressure. Here, the gas supplied to the fixed foil trap 24 is desirably a gas with a high transmittance to EUV light, and for example, rare gas such as helium (He) or argon (Ar) or hydrogen (H2) is used.

[0088] The high-speed debris DB that could not be captured by the rotating foil trap 22 slows down due to an increased probability of collision with gas in the pressure-increased region of the fixed foil trap 24. The collision with gas also changes the direction of travel of the debris DB. The fixed foil trap 24 captures the debris DB, whose speed has decreased and whose direction of travel has changed, by the foil 61 or the fixed frame 60.

[0089] A cover member 25 is also disposed in the connection chamber 21. The cover member 25 surrounds the rotary foil trap 22 and prevents the debris DB captured by the rotary foil trap 22 from scattering inside the connection chamber 21. The cover member 25 includes an entrance side opening KI and exit side openings KOA and KOB. The entrance side opening KI is provided at a position where the EUV light entering the rotary foil trap 22 is not blocked. The exit side opening KOA is provided at a position where the EUV light passing through the entrance side opening KA and the rotary foil trap 22 and entering the fixed foil trap 24 is not blocked. The exit side opening KOB is provided at a position where the EUV light passing through the entrance side opening KI and the rotary foil trap 22 and entering the monitoring device 43 is not blocked.

[0090] At least a portion of the debris DB captured by the rotary foil trap 22 moves radially on the foil 51 of the rotary foil trap 22 due to centrifugal force, detaches from the end of the foil 51, and adheres to the inner surface of the cover member 25. The cover member 25 is heated by a heating means (not shown) or secondary radiation from the heat shield 23 receiving EUV radiation, and the debris DB attached to the inner surface of the cover member 25 due to the heating does not solidify but remains in a liquid state. The debris DB attached to the inner surface of the cover member 25 gathers at the bottom of the cover member 25 by gravity, and is discharged from the bottom of the cover member 25 through the discharge pipe 26 to the outside of the cover member 25, becoming waste material, and is stored in the debris storage unit 4. This allows the cover member 25 to prevent the debris DB detached from the end of the foil 51 of the rotary foil trap 22 from scattering inside the connection chamber 21.

[0091] The debris storage unit 4 includes a debris storage container 31. The debris storage container 31 is disposed outside the connection chamber 21 and attached to the connection chamber 21. The debris storage container 31 stores contents SU including debris DB and waste raw materials.

[0092] A through hole 37 is formed in the bottom wall of the connection chamber 21 to communicate the internal space of the debris container 31 with the internal space of the connection chamber 21. The debris container 31 has a flange 32 on the upper part. The opening of the debris container 31 surrounded by the flange 32 is overlapped with the through hole 37 of the connection chamber 21. The flange 32 is then fixed to the bottom wall of the connection chamber 21, for example, with screws, thereby attaching the debris container 31 to the connection chamber 21. The gap between the flange 32 and the bottom wall of the connection chamber 21 is sealed with a gasket 33. The heat shield 23 is placed above the through hole 37 in an upright state. The discharge port of the discharge pipe 26 is placed above the through hole 37. At this time, the debris container 32 is placed at a position where the debris DB falls from the heat shield 23 and the discharge pipe 26.

[0093] The waste material discharged outside the cover member 25 through the discharge pipe 26 falls in the direction of gravity and is stored in the debris container 31 arranged below the connection chamber 21 (lower side in FIG. 2). Meanwhile, part of the debris DB dispersed in various directions from the plasma P enters the connection chamber 21 through the window portion 17 of the chamber 11 and accumulates on the surface of the heat shield 23 facing the window portion 17. The debris DB accumulated on the heat shield 23 melts due to radiation from the plasma P, and when it reaches a certain amount, it turns into droplets and moves below the heat shield 23 due to gravity. Then, the debris DB that has moved below the heat shield 23 detaches from the heat shield 23 and falls below the connection chamber 21, and is stored in the debris container 31.

[0094] In this way, the heat shield 23 not only limits the EUV radiation from the plasma P to the rotating foil trap 22 to prevent overheating of the rotating foil trap 22 and enables a portion of the EUV light emitted from the plasma P to be extracted through the opening KA, but also reduces the amount of debris DB traveling toward the rotating foil trap 22 as much as possible, thereby reducing the load on the rotating foil trap 22.

[0095] Furthermore, in an LDP-type EUV light source device 1, some of the plasma raw materials (tin) SA, SB supplied to the discharge unit (discharge electrodes EA, EB, etc.) may leak. For example, some of the plasma raw materials SA, SB may leak from containers CA, CB. The leaked plasma raw materials SA, SB become waste raw materials because they do not contribute to the generation of plasma P. The plasma raw materials SA, SB that leak from the discharge unit described above are collected by a surrounding member (not shown).

[0096] A receiving plate member (shovel) 18 is installed inside the connecting chamber 21 in order to guide the plasma raw materials SA and SB collected as waste raw materials by the surrounding member to the debris collection container 31. The receiving plate member 18 is supported in an inclined position so that it spans from the window portion 17 to the through-hole 37. The receiving plate member 18 is heated by heating means (heater) (not shown) so that the plasma raw materials SA and SB collected as waste raw materials are maintained at or above their melting point on the receiving plate member 18. Then, the plasma raw materials SA and SB collected as waste raw materials by the surrounding member and some of the debris DB that has entered the connecting chamber 21 are guided by the receiving plate member 18 and fall into the debris collection container 31.

[0097] Here, most of the debris DB is tin, and the waste material is also tin, so the debris container 31 can also be called a tin recovery container. A heater wire 34 is wound around the debris container 31 as a heating means for heating the debris container 31. The heating means may be embedded in the debris container 31 body. When the EUV light source device 1 is in operation, the inside of the debris container is heated to above the melting point of tin by supplying power to the heater wiring 34, and the tin accumulated inside the debris container 31 is turned into liquid phase.

[0098] The reason why the tin inside the debris container 31 is in a liquid phase is that when the debris DB accumulated inside the debris container 31 solidifies, the accumulation at the point where the debris DB is likely to fall grows like a stalagmite in a limestone cave. When the accumulation of the debris DB grows like a stalagmite, for example, the discharge pipe 26 of the cover member 25 is blocked by the debris DB, and the debris DB accumulates inside the cover member 25. At this time, at least a part of the debris DB accumulated inside the cover member 25 may come into contact with the rotating foil trap 22, hindering the rotation of the rotating foil trap 22 or damaging the rotating foil trap 22. Alternatively, a portion of the emission side openings KOA, KOB provided in the cover member 25 may be blocked by debris DB accumulated inside the cover member 25, blocking a portion of the EUV light passing through the emission side openings KOA, KOB. Therefore, by turning the tin contained inside the debris storage container 31 into a liquid phase, it is possible to flatten the tin inside the debris storage container 31 and store the tin inside the debris storage container 31 while avoiding stalagmite-like growth.

[0099] When recovering the tin accumulated in the debris storage container 31, the power supply to the heater wiring 34 is stopped to stop heating the inside of the debris storage container 31. Then, when the temperature of the debris storage container 31 reaches room temperature and the tin stored in the debris storage container 31 is solidified, the inside of the connection chamber 21 is returned to atmospheric pressure. After that, the debris storage container 31 is removed from the connection chamber 21, and a new debris storage container that does not have any accumulated tin is attached to the connection chamber 21. The tin inside the debris storage container 31 that has been removed from the connection chamber 21 is in a solid phase, but by reheating the debris storage container 31 to make the tin inside liquid again, the tin can be removed from the debris storage container 31. The debris storage container 31 that has been removed from the connection chamber 21 and has had the tin removed from its inside can be reused.

[0100] Furthermore, a monitoring device 43 for monitoring the EUV light is disposed outside the connecting chamber 21. The monitoring device 43 is a detector for detecting the EUV light or a measuring device for measuring the intensity of the EUV light. An EUV light guide hole 28, which is a through hole through which the EUV light passes, is formed in the wall of the connecting chamber 21, and a guide tube 29, through which the EUV light passes without leaking outside the connecting chamber 21, is provided between the EUV light guide hole 28 and the monitoring device 43.

[0101] The heat shield 23 has an opening KB of any shape (for example, circular) for extracting a portion of the EUV light emitted from the plasma P at a position separate from the opening KA. The monitoring device 43, the EUV light guide hole 28, and the guide tube 29 are arranged on an extension of a straight line connecting the plasma P and the center of the opening KB. Therefore, a part of the EUV light emitted from the plasma P passes through the window 17 of the chamber 11, the opening KB of the heat shield 23, the entrance side opening KI of the cover member 25, the gaps between the multiple foils 51 of the rotary foil trap 22, the exit side opening KOB of the cover member 25, the EUV light guide hole 28 in the wall of the connecting chamber 21, and the inner cavity of the guide tube 29, in this order, to reach the monitoring device 43. In this manner, the EUV light can be monitored by the monitoring device 43.

[0102] 6 is a perspective view showing an example of the configuration of the debris container of FIG. 2, and FIG. 7 is a cross-sectional view showing an example of the configuration of the debris container of FIG. 6 and 7, the debris container 31 has a flange 32 on its upper part. The flange 32 is arranged so as to surround the opening of the debris container 31. The debris container 31 is attached by fixing the flange 32 to the bottom wall of the connection chamber 21, for example, using screws, with the opening of the debris container 31 positioned to overlap with a through-hole 37 provided in the bottom part of the connection chamber 21.

[0103] The debris storage container 31 has a heating means 35 embedded in a part of the wall surrounding the storage section for the stored items SU such as debris DB. In order to embed the heating means 35, a plurality of heating means embedded parts 38 are provided in the wall of the debris storage container 31. For example, a cartridge heater in which a heating element is covered with a sheath (metal pipe) is used as the heating means 35. The heating element of the cartridge heater is, for example, a nichrome wire. In this case, the debris storage container 31 can be heated by supplying an electric current to the nichrome wire. The tip of the sheath is sealed. The sheath of the cartridge heater is inserted into the heating means embedded part 38 and is held in the debris storage container 31.

[0104] The contents (debris and waste materials) contained in the debris container 31 are maintained in a liquid phase state at least while the EUV light source device 1 is in operation. Since most of the contents are tin, the debris container 31 is heated so that the temperature of the contents contained therein is equal to or higher than the melting point of tin. For this reason, a temperature sensor 36 for sensing the temperature is embedded in the debris container 31. In order to embed the temperature sensor 36, a temperature sensor embedding portion 39 is provided in the wall of the debris container 31. For example, a resistance temperature detector (RTD) is used as the temperature sensor 36. The resistance temperature detector utilizes the property that the electrical resistance value of metals or metal oxides changes with temperature changes, and measures the temperature by measuring the electrical resistance value. There are various metals used for the resistance temperature detector, but for example, platinum (Pt100) is used because it has stable characteristics and is easily available.

[0105] To facilitate embedding the temperature sensor 36, for example, a sheath-type resistance temperature sensor can be used. In a sheath-type resistance temperature sensor, a resistance element and a conductor connected to the resistance element are inserted into a sheath (metal pipe), and the inside of the sheath is filled with an insulating material (magnesium oxide), forming these into an integrated unit. The tip of the sheath is sealed. The sheath-type resistance temperature sensor is held in the debris container 31 with its sheath inserted into the temperature sensor embedding section 39.

[0106] Although sensors other than a resistance temperature detector can be used as the temperature sensor 36, a resistance temperature detector is capable of highly accurate measurement and has excellent stability and reproducibility. In addition, a resistance temperature detector is relatively insensitive to the effects of electrical noise, so it is suitable for use with the EUV light source device 1 that has a discharge part that generates electrical noise.

[0107] FIG. 8 is a block diagram showing an example of a temperature control system for heat treatment of the debris container in FIG. 8, the temperature control system includes a temperature detection unit 71, a control unit 72, and a heating power supply unit 73. The control unit 72 includes a temperature control unit 72A and a storage capacity estimation unit 72B.

[0108] The temperature detection unit 71 supplies power to the temperature sensor 36 (resistance temperature detector) and detects temperature information from the temperature sensor 36 (detects electrical resistance value). The temperature detection unit 71 also transmits the temperature information from the temperature sensor 36 to the control unit 72. The control unit 72 controls the heating power supply unit 73 to control the amount of power supplied to the heating means (cartridge heater) 35 and to control the power supply on and off. The heating power supply unit 73 supplies power to each heating means 35 individually.

[0109] The temperature control unit 72A controls the temperature of the debris storage container 31, which contains the liquid phase contents, so that the temperature of the debris storage container 31 converges. When the debris storage container 31 is installed in the EUV light source device 1 of FIG. 1, the contents of the debris storage container 31 are mainly tin. At this time, the temperature control unit 72A controls the heating power supply unit 73 based on the temperature information received from the temperature detection unit 71. Note that the electrical connection between the resistance element of the temperature sensor 36 and the temperature detection unit 71 is, for example, a general three-wire connection. The temperature control unit 72A performs, for example, PID control to maintain the temperature of the debris storage container 31 at a target temperature. The gains of the PID control (proportional gain, integral gain, differential gain) are appropriately set based on the heat capacity of the debris storage container 31.

[0110] The capacity estimation unit 72B estimates the capacity of the contents contained in the debris container 31 based on the characteristics of the vibration data that oscillates in accordance with the temperature control by the temperature control unit 72A. The characteristics of the vibration data may be selected from at least one of the amplitude, frequency, and phase of the vibration of the temperature of the debris container 31 when controlling the temperature of the debris container 31 to a target temperature. In addition, the characteristics of the vibration data may be selected from at least one of the amplitude, frequency, and phase of the vibration of the duty in PWM (Pulse Width Modulation) control when controlling the temperature of the debris container 31.

[0111] Here, while the EUV light source device 1 is in operation, the amount of contents (debris) contained in the debris container 31 gradually increases. Therefore, while the EUV light source device 1 is in operation, the heat capacity of the entire debris container 31 also gradually changes.

[0112] On the other hand, each gain of the PID control is set based on the heat capacity of the entire debris container 31 when the debris container 31 contains a predetermined amount of contents, for example. In this case, if the amount of contents contained in the debris container 31 does not match the above-mentioned predetermined amount, even if the temperature of the debris container 31 is tried to be maintained at the target temperature by PID control, the temperature of the debris container 31 does not converge to the target temperature and an oscillation phenomenon occurs. In addition, if the temperature of the debris container 31 does not converge to the target temperature, the temperature control unit 72A changes the amount of power supplied by the heating power supply unit 73 in order to make the temperature of the debris container 31 converge to the target temperature. In order to change the amount of power supplied by the heating power supply unit 73, the temperature control unit 72A changes the duty in the PWM control. At this time, the duty in the PWM control also oscillates in accordance with the oscillation phenomenon of the temperature of the debris container 31.

[0113] Here, when the heat capacity of the entire debris storage container 31 changes, the temperature vibration characteristics of the debris storage container 31 and the duty vibration characteristics in PWM control also change. The heat capacity of the entire debris storage container 31 is the sum of the heat capacity of the debris storage container 31 alone and the heat capacity of the contents stored in the debris storage container 31. Even if the contents stored in the debris storage container 31 change, the heat capacity of the debris storage container 31 alone does not change. For this reason, the storage capacity estimation unit 72B can estimate the amount of contents stored in the debris storage container 31 based on the temperature vibration characteristics of the debris storage container 31 or the duty vibration characteristics in PWM control.

[0114] Here, the temperature control for converging the temperature of the debris storage container 31 to the target temperature does not depend on the presence or absence of a phase change between liquid and solid phases of the contents stored in the debris storage container 31. Therefore, even when the contents stored in the debris storage container 31 are maintained in a liquid phase state, the amount of the contents can be estimated without needing to measure the liquid level. As a result, even when the EUV light source device 1 is in operation, the amount of the contents can be estimated without immersing a temperature sensor or a metal rod in the contents in the debris storage container 31, making it possible to prevent the contents from overflowing from the debris storage container 31 and to efficiently replace the debris storage container 31 containing the contents.

[0115] Figures 9 and 10 are diagrams showing an example of temperature change according to the amount of contents stored in the debris storage container in Figure 2. Figures 9 and 10 show the temperature amplitude of the debris storage container 31 as an example of the characteristics of vibration data that oscillates in conjunction with temperature control by the temperature control unit 72A. Figure 9 shows the time characteristic of the temperature of the debris storage container 31 when there is almost no content stored in the debris storage container 31, and Figure 10 shows the time characteristic of the temperature of the debris storage container 31 when there is a certain amount of content stored in the debris storage container 31. Time 0 is an arbitrary point in time after the temperature of the debris storage container 31 has almost reached the target temperature (270°C) through temperature control (PID control).

[0116] 9, each gain of the PID control is set based on a state in which a predetermined amount of contents is contained in the debris container 31. For this reason, when there is almost no content contained in the debris container 31, temperature oscillation occurs even after the temperature of the debris container 31 has almost reached the target temperature (270°C), and a temperature waveform W1 with an amplitude A1 is obtained.

[0117] On the other hand, when the debris storage container 31 contains a certain amount of contents, the amount of contents in the debris storage container 31 differs from the predetermined amount of contents contained in the debris storage container 31 when each gain of the PID control is set. For this reason, even after the temperature of the debris storage container 31 has almost reached the target temperature (270°C), temperature oscillation occurs, and a temperature waveform W2 with an amplitude A2 is obtained. At this time, the amplitude A2 of the temperature waveform W2 is smaller than the amplitude A1 of the temperature waveform W1. This is thought to be because, compared to when the debris storage container 31 contains almost no contents, when a certain amount of contents is contained, the difference between the heat capacity of the debris storage container 31 as a whole, for which each gain is set based on the state in which a predetermined amount of contents is contained, is smaller.

[0118] 9 and 10, when the gains for temperature control are set based on the state in which the debris container 31 contains a predetermined amount of contents, the amplitude of temperature oscillation after the temperature of the debris container 31 has almost reached the target temperature (270°C) depends on the amount of contents contained in the debris container 31. Therefore, by obtaining correlation data between the volume of tin and the amplitude of temperature oscillation in advance, measuring the amplitude of temperature oscillation when the target temperature is reached, and comparing the measurement result with the correlation data, it is possible to estimate the amount of contents contained in the debris container 31.

[0119] FIG. 11 is a flow chart showing an example of a process for estimating the amount of stored items in the debris container of FIG. In FIG. 11, the correlation between the amplitude AN of the temperature oscillation after the temperature of the debris container 31 has almost reached the target temperature and the amount VN of the contents (debris) contained in the debris container 31 is determined in advance, and the correlation data is stored in the control unit 72 (step S1).

[0120] The control for maintaining the temperature of the debris storage container 31 at the target temperature is performed, for example, by PID control. Parameters such as the target temperature and each gain of the PID control are stored in advance in the control unit 72. Here, each gain of the PID control is set based on a state in which the debris storage container 31 contains a predetermined amount of contained items (debris). Furthermore, collection of correlation data between the amplitude AN of the temperature vibration and the amount of contained items VN is performed under each gain condition set based on a state in which the debris storage container 31 contains a predetermined amount of contained items (debris).

[0121] The control unit 72 receives temperature information of the debris storage container 31 from the temperature detection unit 71 , and controls the heating power supply unit 73 based on the temperature information, thereby starting temperature control of the debris storage container 31 by the heating means 35 . Furthermore, the control unit 72 starts acquiring the time-varying characteristics of the temperature T of the debris container 31 from the start of the temperature control (step S2).

[0122] After the temperature of the debris container 31 reaches the target temperature (e.g., 270°C), the control unit 72 calculates the amplitude AM of the temperature vibration from the time change characteristic data of the temperature T of the debris container 31 using a calculation means not shown (step S3). Next, the control unit 72 compares the amplitude AM of the temperature vibration calculated in step S3 with the amplitude AN of the correlation data stored in step S1, and sets the capacity VN of the contents in the debris storage container 31 linked to the amplitude AN of the correlation data corresponding to the amplitude AM of the temperature vibration calculated in step S3 as an estimated value VM of the capacity of the contents in the debris storage container 31 while the EUV light source device 1 is operating (step S4).

[0123] Next, the control unit 72 compares the estimated value VM of the storage capacity of the stored material obtained in step S4 with the threshold value Vt, which is the maximum allowable value of the storage capacity stored in advance (step S5). When the estimated value VM of the storage capacity of the stored material is equal to or greater than the threshold value Vt (VM≧Vt), the control unit 72 sends a warning signal to the outside from a warning means (not shown) (step S6). Thereby, the control unit 72 can notify the outside of the state before the stored material overflows from the debris storage container 31, and can provide a determination material for the replacement timing of the debris storage container 31 in which the stored material is stored.

[0124] On the other hand, when the estimated amount VM of the storage capacity of the stored material is less than the threshold value Vt (VM < Vt), the control unit 72 returns to step S3 and calculates the amplitude AN of the temperature vibration again. Note that when VM < Vt, it may be configured to shift to step S3 after a certain period of time has elapsed since the determination in step S5. Thereby, when the estimated value VM of the storage capacity of the stored material is less than the threshold value Vt, the estimation of the storage capacity of the stored material can be repeated, and the estimation of the storage capacity of the stored material can be continued until the estimated value VM of the storage capacity of the stored material becomes equal to or greater than the threshold value Vt.

[0125] As described above, according to the above-described embodiment, it is possible to estimate the storage capacity of the stored material after the temperature of the debris storage container 31 has reached the target temperature by temperature control and while the EUV light source device 1 is operating. Therefore, when the storage capacity of the stored material exceeds the allowable value while the EUV light source device 1 is operating, it is possible to promptly send a warning signal to the outside, and it is possible to prevent the stored material from overflowing from the debris storage container 31.

[0126] In addition, the storage capacity of the stored material can be estimated based on the comparison result of the amplitude data of the temperature vibration taken during the temperature control of the debris storage container 31, and the construction of a complicated algorithm for estimating the storage capacity of the stored material can be made unnecessary. Furthermore, the temperature sensor 36 used to control the temperature of the debris storage container 31 can be used to estimate the amount of stored items in the debris storage container 31, eliminating the need to provide a separate temperature sensor to estimate the amount of stored items, thereby suppressing the increase in resources required to estimate the amount of stored items.

[0127] In the above embodiment, an example was shown in which PID control was adopted as the temperature control, but the temperature control is not limited to PID control. Any control method may be used as long as the vibration characteristics when the temperature of the debris storage container 31 oscillates after reaching the target temperature changes depending on the amount of contents stored in the debris storage container 31.

[0128] FIG. 12 is a block diagram illustrating an example of a hardware configuration of the control unit in FIG. 12, the control unit 72 includes a processor 101, a communication control device 102, a communication interface 103, a primary storage device 104, an auxiliary storage device 105, and an input / output interface 107. The processor 101, the communication control device 102, the communication interface 103, the primary storage device 104, the auxiliary storage device 105, and the input / output interface 107 are connected to each other via an internal bus 106. The primary storage device 104 and the auxiliary storage device 105 are accessible from the processor 101.

[0129] In addition, a sensor 111, a heater 112, an input device 113, and an output device 114 are provided outside the control unit 72. The sensor 111, the heater 112, the input device 113, and the output device 114 are connected to the internal bus 106 via an input / output interface 107. The input device 113 and the output device 114 can be used as a human interface.

[0130] The input device 113 is, for example, a keyboard, a mouse, a touch panel, a card reader, a voice input device, etc. The output device 114 is, for example, a screen display device (a liquid crystal monitor, an organic EL (Electro Luminescence) display, a graphic card, etc.), a voice output device (a speaker, etc.), a printer, etc.

[0131] The sensor 111 detects the temperature of the debris container 31 in Fig. 2. The sensor 111 is, for example, the temperature sensor 36 in Fig. 8. The heater 112 heats the debris container 31. The heater 112 is, for example, the heating means 35 in Fig. 8.

[0132] The processor 101 is hardware that controls the operation of the entire control unit 72. The processor 101 may be a central processing unit (CPU) or a graphics processing unit (GPU). The processor 101 may be a single-core processor or a multi-core processor. The processor 101 may include a hardware circuit (for example, a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC)) such as an accelerator that performs part of the processing. The processor 101 may operate as a neural network.

[0133] The primary storage device 104 can be composed of, for example, a semiconductor memory such as a static random access memory (SRAM) or a dynamic random access memory (DRAM). The primary storage device 104 can store programs being executed by the processor 101 and can provide a work area for the processor 101 to execute the programs.

[0134] The auxiliary storage device 105 is a storage device with a large storage capacity, such as a hard disk device or a solid state drive (SSD). The auxiliary storage device 105 can hold executable files of various programs and data used to execute the programs. The auxiliary storage device 105 can store a temperature control program 105A and a storage capacity estimation program 105B. The temperature control program 105A and the storage capacity estimation program 105B may be software that can be installed in the control unit 72, or may be incorporated in the control unit 72 as firmware.

[0135] The communication control device 102 is hardware having a function of controlling communication with the outside. The communication control device 102 is connected to a network 109 via a communication interface 103. The network 109 may be the Internet or a Wide Area Network (WAN), a Local Area Network (LAN) such as WiFi or Ethernet (registered trademark), or a mixture of the Internet, a WAN, and a LAN.

[0136] The input / output interface 107 converts data input from the sensor 112 and the input device 113 into a data format that can be processed by the processor 101, converts data output from the processor 101 into a drive signal for the heater 112, and converts data into a data format that can be processed by the output device 114.

[0137] The processor 101 reads the temperature control program 105A into the primary storage device 104 and executes the temperature control program 105A to control the temperature of the debris storage container 31 containing the liquefied contents so that the temperature of the debris storage container 31 converges. At this time, the processor 101 can operate as the temperature control unit 72A of FIG. 8.

[0138] Moreover, the processor 101 can read the storage capacity estimation program 105B into the primary storage device 104 and execute the storage capacity estimation program 105B to estimate the capacity of the contents stored in the debris storage container 31 based on the characteristics of the vibration data that vibrates in association with the temperature control of the debris storage container 31. At this time, the processor 101 can operate as the storage capacity estimation unit 72B of FIG.

[0139] The execution of the temperature control program 105A and the capacity estimation program 105B may be shared among multiple processors or computers. Alternatively, the processor 101 may instruct a cloud computer or the like to execute all or part of the temperature control program 105A and the capacity estimation program 105B via the network 109, and receive the execution results.

[0140] In the above-described embodiment, in order to estimate the amount of stored items in the debris container 31, correlation data between the amplitude AN of the temperature vibration and the amount VN of stored items in the debris container 31 is stored in advance in step S1, and a comparison is made between the amplitude AM of the temperature vibration calculated in step S3 and the amplitude AN of the correlation data stored in step S1, as shown in Fig. 11. The amount of stored items in the debris container 31 may be estimated based on such a rule base, or may be estimated based on machine learning using a neural network.

[0141] FIG. 13 is a diagram illustrating an example of a learning model used for capacity estimation according to the embodiment. 13, the learning model includes a neural network. The neural network includes an input layer LI, an intermediate layer LH, and an output layer LO. The input layer LI includes a node NI, the intermediate layer LH includes a node NH, and the output layer LO includes a node NO. The node NI is connected to the node NH via an edge EA, and the node NH is connected to the node NO via an edge EB.

[0142] In the learning stage of the neural network, when the characteristics of the vibration data that oscillates in association with the temperature control of the debris container 31 are provided to the input layer LI, the neural network learns the amount of contents contained in the debris container 31 as correct answer data. At this time, weights are set for each edge EA, EB of the neural network. The characteristics of the vibration data provided to the input layer LI may be the amplitude, frequency and phase of the vibration of the temperature of the debris container 31 when controlling the temperature of the debris container 31 to a target temperature, or the amplitude, frequency and phase of the vibration of the duty in PWM control when controlling the temperature of the debris container 31.

[0143] In the inference stage of the neural network, the characteristics of the vibration data associated with the temperature control observed during the operation of the EUV light source device 1 are input to the input layer LI. Then, the output from the output layer LO of the neural network can be used as an estimate of the amount of contents contained in the debris container 31.

[0144] At this time, the data input to each node NI in the input layer LI is weighted by the weight of each edge EA, and then input to each node NH in the hidden layer LH, and the inputs to each node NH are added for each node NH to become the value of each node NH. The values ​​of each node NH in the hidden layer LH are nonlinearly transformed by an activation function (e.g., a sigmoid function), weighted by the weight of each edge EB, and then input to each node NO in the output layer LO, and the inputs to each node NO are added for each node NO to become the value of each node NO.

[0145] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and includes various modified examples. For example, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0146] For example, the above-mentioned method for estimating the amount of contained objects is intended for the amount of debris (tin) contained in the debris container of the EUV light source device, but is not limited thereto. The object is not limited to tin, which is the main component of debris, as long as it is a metal that is solid at room temperature and is heated to a liquid state for use. For example, the method can also be used to estimate the amount of liquid metal (sodium, lithium, etc.) used in a liquid metal cooled reactor. This liquid metal can be used, for example, as a coolant for a nuclear power plant. In this case, the above-mentioned method for estimating the amount of contained objects can be used to estimate the amount of liquid metal that is reduced during circulation. If the amount of contained liquid metal is equal to or less than a minimum allowable value, an alarm signal may be sent to the outside.

[0147] In addition, the above-mentioned capacity estimation method has been used as an example of estimating the capacity of liquid metal, but the method is not limited to metal as long as the liquid is temperature-controlled, and may be applied to estimating the capacity of, for example, cooling water, liquid nitrogen, liquid helium, lubricating oil, or liquid fuel. [Explanation of symbols]

[0148] 1 Extreme ultraviolet light source device 2 Light source section 3. Debris mitigation section 4. Debris storage area 11. Chamber 21 Connection chamber 31 Debris container DB Debris SU Contents 35 Heating means 36 Temperature Sensor 71 Temperature detection section 72 Control section 72A Temperature Control Unit 72B Capacity Estimation Section 73 Heating power supply unit

Claims

1. A step of controlling the temperature of a storage container in which the liquefied contents are stored so that the temperature of the storage container converges; and estimating a capacity of the storage container based on characteristics of vibration data that oscillates in association with the temperature control, A storage capacity estimation method, characterized in that the method is applied to estimating the capacity of a metal containing device comprising a container for containing liquid metal as the contained item, a heating means for heating the container, a temperature measuring means for measuring the temperature of the container, a power supplying means for supplying power to the heating means, and a control unit for controlling the power supplying means based on temperature information from the temperature measuring means so that the temperature of the container becomes a target temperature.

2. A step of controlling the temperature of a storage container in which the liquefied contents are stored so that the temperature of the storage container converges; and estimating a capacity of the storage container based on characteristics of vibration data that oscillates in association with the temperature control, 1. A method for estimating the amount of debris contained in a storage container in an extreme ultraviolet light source device comprising: a light source unit that excites a plasma raw material containing metal to generate plasma that radiates extreme ultraviolet light; a storage container that contains debris containing metal dispersed from the plasma; a heating means that heats the storage container; a temperature measuring means that measures the temperature of the storage container; a power supply means that supplies power to the heating means; and a control unit that controls the power supply means based on temperature information from the temperature measuring means so that the temperature of the storage container becomes a target temperature.

3. 3. The method for estimating capacity according to claim 1 or 2, wherein the characteristics of the vibration data are selected from at least one of an amplitude, a frequency, and a phase of the vibration of the temperature of the storage container when the temperature of the storage container is controlled so as to become a target temperature.

4. 4. The method for estimating capacity according to claim 1, wherein the characteristic of the vibration data is selected from at least one of an amplitude, a frequency, and a phase of a duty oscillation in a PWM (Pulse Width Modulation) control when controlling the temperature of the storage container.

5. A step of acquiring amplitude data of temperature vibration corresponding to the amount of the contents when the temperature of the storage container reaches a target temperature; storing correlation data between the collected amplitude data and the amount of the contents; obtaining a time-varying characteristic of the temperature of the container when the container is temperature-controlled under the same temperature control conditions as when the correlation data was obtained; After the temperature of the storage container reaches the target temperature, calculating an amplitude of the temperature oscillation from the time-varying characteristic of the temperature of the storage container collected; 5. The method for estimating capacity according to claim 1, further comprising a step of comparing the calculated amplitude with an amplitude of the correlation data, and determining a capacity associated with an amplitude of the correlation data corresponding to the calculated amplitude as an estimated value of the capacity.

6. A step of estimating a capacity of the container and then comparing the estimated capacity of the container with a threshold value; 6. The method for estimating capacity according to claim 5, further comprising the step of: sending a warning signal to the outside when the estimated capacity of the stored items is equal to or greater than the threshold value.

7. 7. The method for estimating capacity according to claim 6, further comprising the step of acquiring a time-varying characteristic of temperature of the container when the estimated capacity of the container is smaller than the threshold value.

8. 8. The method for estimating capacity according to claim 1, wherein the characteristics of the vibration data vary based on the capacity of the container.

9. a temperature control unit that controls the temperature of a storage container in which the liquefied contents are stored so that the temperature of the storage container converges; a capacity estimation unit that estimates a capacity of the storage container based on characteristics of vibration data that oscillates in accordance with the temperature control, A storage capacity estimation device characterized in that it is applied to estimating the capacity of a metal containment device comprising a storage container that contains liquid metal as the contained item, a heating means for heating the storage container, a temperature measurement means for measuring the temperature of the storage container, a power supply means for supplying power to the heating means, and a control unit that controls the power supply means based on temperature information from the temperature measurement means so that the temperature of the storage container becomes a target temperature.

10. a temperature control unit that controls the temperature of a storage container in which the liquefied contents are stored so that the temperature of the storage container converges; a capacity estimation unit that estimates a capacity of the storage container based on characteristics of vibration data that oscillates in accordance with the temperature control, 1. A storage amount estimation device for an extreme ultraviolet light source device comprising: a light source unit that excites a plasma raw material containing metal to generate plasma that radiates extreme ultraviolet light; a storage container that contains debris containing metal dispersed from the plasma; a heating means that heats the storage container; a temperature measuring means that measures the temperature of the storage container; a power supply means that supplies power to the heating means; and a control unit that controls the power supply means based on temperature information from the temperature measuring means so that the temperature of the storage container becomes a target temperature, said device being applied to estimating the amount of debris stored in the storage container.

11. A program for causing a computer to execute each step of the capacity estimation method described in any one of claims 1 to 8.

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