EUV Light Generation Device, Electronic Device Manufacturing Method, and Inspection Method

Abstract

SOLUTION: An EUV light generation apparatus 1 that generates EUV light by irradiating a target with a pulse laser beam, and includes a chamber 2 and a target supply unit 26 that supplies a target 27 to a plasma generation region 25 in the chamber, a pulsed laser device 3 that generates pulsed laser light with which the target is irradiated, and a processor 5 for changing a generation frequency of the target generated by the target supply unit on the basis of a size of the target or related information related to the size of the target to a natural number multiple of an irradiation frequency of the pulse laser beam.EFFECT: A generation amount of debris is suppressed from increasing, and output degradation of EUV light is suppressed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an EUV light generating device, a method for manufacturing an electronic device, and an inspection method.

Background Art

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in photolithography of semiconductor processes has been rapidly progressing. In the next generation, microfabrication of 10 nm or less will be required. For this reason, development of a semiconductor exposure apparatus combining an apparatus for generating extreme ultraviolet (EUV) light with a wavelength of about 13 nm and a reduction projection reflective optical system has been expected.

[0003] As an EUV light generating device, development of a Laser Produced Plasma (LPP) type device that uses plasma generated by irradiating a target material with laser light has been progressing.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] An EUV light generation device according to one aspect of the present disclosure is an EUV light generation device that generates EUV light by plasmaizing a target by irradiating the target with pulsed laser light, and includes a chamber, a target supply unit that supplies the target to a plasma generation region in the chamber, a pulsed laser device that generates pulsed laser light to irradiate the target, and a processor that changes the generation frequency of the target generated by the target supply unit to a natural multiple of the irradiation frequency of the pulsed laser light based on the size of the target or related information related to the size of the target.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating EUV light by plasmaizing a target by irradiating the target with pulsed laser light using an EUV light generation device including a chamber, a target supply unit that supplies the target to a plasma generation region in the chamber, a pulsed laser device that generates pulsed laser light to irradiate the target, and a processor that changes the generation frequency of the target to a natural multiple of the irradiation frequency of the pulsed laser light based on the size of the target, outputting the EUV light to an exposure device, and exposing the EUV light on a photosensitive substrate in the exposure device to manufacture an electronic device.

[0007] An inspection method according to one aspect of the present disclosure includes generating EUV light by plasmaizing a target by irradiating the target with pulsed laser light using an EUV light generation device including a chamber, a target supply unit that supplies the target to a plasma generation region in the chamber, a pulsed laser device that generates pulsed laser light to irradiate the target, and a processor that changes the generation frequency of the target to a natural multiple of the irradiation frequency of the pulsed laser light based on the size of the target, outputting the EUV light to an inspection device as an inspection light source, and exposing the EUV light on a mask in the inspection device to inspect the mask.

Brief Description of the Drawings

[0008] Some embodiments of the present disclosure will be described below by way of example only with reference to the accompanying drawings.

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[0009] <Content> 1. Overall description of the EUV light generation system 1.1 Configuration 1.2 Operation 2. EUV light generation apparatus according to the comparative example 2.1 Configuration 2.2 Operation 2.3 Problems 3. EUV Light Generation Device of the First Embodiment 3.1 Configuration 3.2 Operation 3.3 Function and Effect 4. EUV Light Generation Device of the Second Embodiment 4.1 Configuration 4.2 Operation 4.3 Function and Effect 5. EUV Light Generation Device of the Third Embodiment 5.1 Configuration 5.2 Operation 5.3 Function and Effect 6. EUV Light Generation Device of the Fourth Embodiment 6.1 Configuration 6.2 Operation 6.3 Function and Effect 7. EUV Light Generation Device of the Fifth Embodiment 7.1 Configuration 7.2 Operation 7.3 Function and Effect 8. Others

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and redundant explanations are omitted.

[0011] 1. Overall Description of the EUV Light Generation System 1.1 Configuration FIG. 1 schematically shows the configuration of an LPP type EUV light generation system 11. The EUV light generation apparatus 1 is used together with at least one pulsed laser apparatus (hereinafter simply referred to as a laser apparatus) 3. In the present application, a system including the EUV light generation apparatus 1 and the laser apparatus 3 is referred to as an EUV light generation system 11. As shown in FIG. 1 and described in detail below, the EUV light generation apparatus 1 includes a chamber 2 and a target supply unit 26. The chamber 2 is configured to be sealable. The target supply unit 26 is attached, for example, so as to penetrate the wall of the chamber 2. The material of the target 27 output from the target supply unit 26 contains tin. The material of the target 27 can also contain a combination of tin and terbium, gadolinium, lithium, or xenon. The target 27 is in the form of a droplet.

[0012] At least one through hole is provided in the wall of the chamber 2. A window 21 is provided in the through hole. Pulsed laser light 32 output from the laser apparatus 3 passes through the window 21. Inside the chamber 2, for example, an EUV condenser mirror 23 having a reflective surface in the shape of a rotational ellipsoid is disposed. The EUV condenser mirror 23 has first and second focal points. On the surface of the EUV condenser mirror 23, for example, a multilayer reflective film in which molybdenum and silicon are alternately laminated is formed. The EUV condenser mirror 23 is arranged such that, for example, its first focal point is located in the plasma generation region 25 and its second focal point is located at the intermediate focus point (IF) 292. A through hole 24 is provided in the central portion of the EUV condenser mirror 23. Pulsed laser light 33 passes through the through hole 24.

[0013] The EUV light generation apparatus 1 also includes an EUV light generation processor 5, a target sensor 4, and the like. The target sensor 4 has an imaging function of imaging the target 27 and outputting a target image TP, and is configured to detect the presence, trajectory, position, speed, etc. of the target 27.

[0014] Further, the EUV light generation apparatus 1 includes a connection portion 29 that communicates the inside of the chamber 2 with the inside of the external device 6. Inside the connection portion 29, a wall 291 having an aperture 293 formed therein is provided. The wall 291 is arranged such that the aperture 293 thereof is located at the second focal position of the EUV condenser mirror 23.

[0015] Furthermore, the EUV light generation apparatus 1 includes a laser beam traveling direction control unit 34, a laser beam condenser mirror 22, a target recovery unit 28 for recovering the target 27, and the like. The laser beam traveling direction control unit 34 includes an optical element for defining the traveling direction of the laser beam and an actuator for adjusting the position, orientation, etc. of this optical element.

[0016] 1.2 Operation As shown in FIG. 1, the pulsed laser beam 31 output from the laser device 3 passes through the laser beam traveling direction control unit 34, passes through the window 21 as the pulsed laser beam 32, and enters the chamber 2. The pulsed laser beam 32 travels inside the chamber 2 along at least one optical path, is reflected by the laser beam condenser mirror 22, and is irradiated onto at least one target 27 as the pulsed laser beam 33.

[0017] The target supply unit 26A outputs the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 is irradiated with at least one pulse included in the pulsed laser beam 33. The target 27 irradiated with the pulsed laser beam 33 is turned into plasma, and radiation light 251 is emitted from the plasma. The EUV condenser mirror 23 reflects the EUV light 252 included in the radiation light 251 with a high reflectance compared to light in other wavelength ranges. The EUV light 252 reflected by the EUV condenser mirror 23 is condensed at the intermediate focus point 292 and output to the external device 6. Note that a plurality of pulses included in the pulsed laser beam 33 may be irradiated onto one target 27.

[0018] The EUV light generation processor 5 oversees the overall control of the EUV light generation system 11. The EUV light generation processor 5 processes the target image PT and the like output by the target sensor 4. Further, the EUV light generation processor 5 controls, for example, the timing at which the target 27 is output, the output direction of the target 27, and the like. Furthermore, the EUV light generation processor 5 controls, for example, the oscillation timing of the laser device 3, the traveling direction of the pulsed laser light 32, the condensing position of the pulsed laser light 33, and the like. The various controls described above are merely examples, and other controls may be added as necessary.

[0019] 2. EUV Light Generation Device According to Comparative Example 2.1 Configuration FIG. 2 is a cross-sectional view showing the configuration of an EUV light generation device 1A according to a comparative example. FIG. 3 is a cross-sectional view of the EUV light generation device 1A when viewed from a different perspective than FIG. 2. In FIGS. 2 and 3, the output direction of the EUV light is taken as the Z direction, and the direction opposite to the output direction of the target 27 is taken as the Y direction. The direction perpendicular to both the Z direction and the Y direction is taken as the X direction. FIG. 2 shows the EUV light generation device 1A viewed in the X direction. FIG. 3 shows the EUV light generation device 1A viewed in the Z direction and is a cross-sectional view showing the arrangement of the target generation system 260, the target detection unit 41, and the image measurement unit 43.

[0020] The EUV light generation device 1A includes an EUV light generation processor 5A, a delay circuit 72, a chamber 2A, a target generation system 260, a laser light traveling direction control unit 34A, a target detection unit 41, and an image measurement unit 43. The target detection unit 41 and the image measurement unit 43 constitute the target sensor 4 shown in FIG. 1.

[0021] Inside the chamber 2A, a condenser unit 22A, an EUV condenser mirror 23, a target recovery unit 28, an EUV condenser mirror holder 81, plates 82 and 83, a stage 84, and a connection unit 29 are provided.

[0022] The plate 82 is fixed to the chamber 2A. A plate 83 is supported by the plate 82. The condensing unit 22A includes a laser light condensing mirror 221 and a laser light condensing mirror 222.

[0023] The stage 84 can adjust the position of the plate 83 relative to the plate 82. By adjusting the position of the plate 83, the positions of the laser light condensing mirror 221 and the laser light condensing mirror 222 are adjusted. The positions of the laser light condensing mirror 221 and the laser light condensing mirror 222 are adjusted so that the pulsed laser light 33 reflected by these mirrors is condensed in the plasma generation region 25.

[0024] The EUV condensing mirror 23 is fixed to the plate 82 via an EUV condensing mirror holder 81.

[0025] The laser device 3A may be a MOPA (Master Oscillator Power Amplifier) system. The laser device 3A is configured to output pulsed laser light 31. The laser device 3A may have a configuration including a master oscillator (not shown), an optical isolator (not shown), and a plurality of CO2 laser amplifiers (not shown). A solid-state laser can be adopted for the master oscillator. The wavelength of the pulsed laser light 31 output by the master oscillator is, for example, 10.59 μm, and the repetition frequency of the pulsed oscillation is, for example, 100 kHz.

[0026] The laser light traveling direction control unit 34A is arranged in the optical path of the pulsed laser light 31 so as to reflect the pulsed laser light 31 reflected by the high-reflection mirrors 341 and 342 toward the inside of the chamber 2A.

[0027] As shown in FIGS. 2 and 3, the target generation system 260 includes a target generation processor 52A, a target supply unit 26A, an inert gas supply unit 290, a heater power supply 53, and a piezo power supply 54.

[0028] The target generation processor 52A controls the target generation system 260. The target generation processor 52A is, for example, a processing device including a storage device storing a control program and a CPU (Central Processing Unit) that executes the control program. The target generation processor 52A is specially configured or programmed to execute various processes.

[0029] The target generation processor 52A includes a memory 523 as a storage device, and initial setting information is stored in the memory 523. The initial setting information includes various setting information such as a pressure value for controlling the inert gas supply unit 290, temperature information for controlling the heater power supply 53, and a driving frequency for controlling the piezo power supply 54. The target generation processor 52A controls each part of the target generation system 260 based on the initial setting information. Note that the initial setting information may be stored in the memory 523 in advance, may be input from the EUV light generation processor 5A, or may be stored in a storage device external to the target generation processor 52A. Note that the EUV light generation processor 5A is also similar to the target generation processor 52A in that it is composed of a processing device including a storage device and a CPU.

[0030] The target supply unit 26A includes a reservoir 267, a heater 261, a temperature sensor 262, a pressure regulator 263, a piezo element 264, a nozzle 265, and a filter 266.

[0031] The reservoir 267 stores the material of the target 27. A heater 261 used to melt the material of the target 27 and a temperature sensor 262 for measuring the temperature of the reservoir 267 are fixed to the reservoir 267. The output signal output from the temperature sensor 262 is input to the target generation processor 52A. The target generation processor 52A outputs a drive signal to the heater power supply 53 based on the output signal from the temperature sensor 262.

[0032] The nozzle 265 is provided with a nozzle hole 268 that discharges the material of the dissolved target 27 inside the reservoir 267. The target supply unit 26A is attached to the chamber 2A such that the nozzle hole 268 of the nozzle 265 is disposed inside the chamber 2A. The filter 266 is disposed upstream of the nozzle 265 and removes impurities contained in the material of the target 27. Hereinafter, the material of the target 27 may be referred to as the target substance.

[0033] The pressure regulator 263 is installed on the pipe between the inert gas supply unit 290 and the reservoir 267 so as to regulate the pressure of the inert gas supplied from the inert gas supply unit 290 into the reservoir 267. The pressure regulator 263 is connected to the target generation processor 52A. When pressure is applied to the reservoir 267, the target substance is discharged from the nozzle 265.

[0034] A piezo element 264 is disposed near the nozzle hole 268 of the nozzle 265. A piezo power supply 54 that supplies driving power to the piezo element 264 is connected to the piezo element 264. The target generation processor 52A inputs an electrical signal corresponding to the driving frequency set for the piezo element 264 via the piezo power supply 54. The piezo element 264 vibrates by the input electrical signal. The vibration of the piezo element 264 is transmitted to the nozzle 265, causing the nozzle 265 to vibrate. The vibration frequency of the nozzle 265 and the driving frequency of the piezo element 264 are not exactly the same, but they have a positive correlation, and the higher the driving frequency of the piezo element 264, the higher the vibration frequency of the nozzle 265.

[0035] The vibration frequency of the nozzle 265 defines the generation frequency f of the target 27. A plurality of targets 27 are periodically supplied to the plasma generation region 25 at intervals. The generation frequency f of the target 27 is the number of targets 27 generated by the target supply unit 26A per unit time and supplied to the plasma generation region 25. The vibration frequency of the nozzle 265 and the generation frequency f are not exactly the same, but they also have a positive correlation, and the higher the vibration frequency of the nozzle 265, the higher the generation frequency f.

[0036] The target supply unit 26A includes an XZ stage (not shown). The EUV light generation processor 5A adjusts the trajectory 270 of the target 27 (hereinafter referred to as the target trajectory 270) so that the target 27 passes through the plasma generation region 25 by controlling the XZ stage.

[0037] The target detection unit 41 is attached to the chamber 2A. The target detection unit 41 is a sensor that detects the target 27 passing through the target detection region R. The target detection region R is a predetermined region within the chamber 2A and is located at a predetermined position on the target trajectory 270 between the target supply unit 26A and the plasma generation region 25.

[0038] As shown in FIG. 3, the target detection unit 41 includes a light receiving unit 41A and a light emitting unit 41B. The light receiving unit 41A includes a container 411, a photosensor 412, and a light receiving optical system 413. The light emitting unit 41B includes a container 415, a light source 416, and an illumination optical system 417. The light emitting unit 41B illuminates the target 27 passing through the target detection region R. The light source 416 is a CW (Continuous Wave) laser whose output remains constant without changing with time, unlike a pulsed laser. The illumination optical system 417 includes a cylindrical lens. The illumination light output by the light source 416 is condensed by the illumination optical system 417. The condensing position of the illumination optical system 417 is preferably on the target trajectory 270. More specifically, as shown in FIG. 3, once the condensed illumination light diffracts and spreads after illuminating the target 27. It is preferable that the position of the beam waist where the illumination light beam is most condensed overlaps with the target detection region R.

[0039] The light receiving unit 41A and the light emitting unit 41B are attached to windows 21a and 21b disposed on opposite sides of each other with the target trajectory 270 therebetween. The windows 21a and 21b are provided in the chamber 2A.

[0040] The light-receiving unit 41A condenses the illumination light from the light-emitting unit 41B with the light-receiving optical system 413 and receives it with the photosensor 412. The photosensor 412 is composed of a photoelectric conversion element such as a photodiode, for example, and outputs a light-receiving signal with a signal intensity corresponding to the amount of received light. When the target 27 passes through the target detection region R, the output of the photosensor 412 fluctuates. The light-receiving unit 41A outputs a passing timing signal T1 for notifying the passage of the target 27 based on the output fluctuation of the photosensor 412.

[0041] The image measurement unit 43 is arranged on the downstream side of the target detection unit 41 in the traveling direction of the target 27. The image measurement unit 43 is attached to the wall surface portion of the chamber 2A near the plasma generation region 25. The image measurement unit 43 images the target 27 supplied to the plasma generation region 25 and outputs a target image TP. The image measurement unit 43 includes a light source unit 436 and an imaging unit 431. The light source unit 436 and the imaging unit 431 are arranged to face each other with the plasma generation region 25 on the target orbit 270 interposed therebetween. The facing direction of the light source unit 436 and the imaging unit 431 is orthogonal to the target orbit 270.

[0042] The light source unit 436 outputs pulsed light for imaging the target 27 that has reached the plasma generation region 25. The light source unit 436 includes a window 437, a light source 438, and an illumination optical system 439. The light source 438 may be a light source that emits pulses, such as a xenon flash lamp or a laser light source, for example. The light source 438 is connected to the EUV light generation processor 5A. A lighting signal LU output from the EUV light generation processor 5A is input to the light source 438. The light source 438 emits pulsed light based on the input lighting signal LU.

[0043] The illumination optical system 439 is an optical system including, for example, a collimator lens or the like. The collimator lens collimates the pulsed light emitted by the light source 438. The illumination optical system 439 guides the pulsed light emitted from the light source 438 to the plasma generation region 25 on the target orbit 270 through the window 437. When the target 27 reaching the plasma generation region 25 is irradiated with the pulsed light, a part of the pulsed light is blocked, and the projection image of the target 27 is projected onto the imaging unit 431.

[0044] The imaging unit 431 images the projection image of the target 27. The imaging unit 431 includes a window 433, an image sensor 434, and a transfer optical system 435. The pulsed light including the projection image of the target 27 enters the transfer optical system 435 in the imaging unit 431 through the window 433. The transfer optical system 435 includes, for example, a plurality of lenses. The transfer optical system 435 forms an image of the projection image of the target 27 on the light receiving surface of the image sensor 434.

[0045] The image sensor 434 is a two-dimensional image sensor such as a CCD. The image sensor 434 outputs an image signal corresponding to the projection image of the target 27 formed on the light receiving surface. The image sensor 434 is provided with a shutter 432. The shutter 432 may be an electric shutter or a mechanical shutter. An imaging timing signal TS2 output from the EUV light generation processor 5A is input to the imaging unit 431 through a delay circuit 72. The opening and closing of the shutter 432 are controlled by the imaging timing signal TS2. The image sensor 434 images only while the shutter 432 is open. The operations of the imaging unit 431 and the light source unit 436 are synchronized by the imaging timing signal TS2 and the lighting signal LU.

[0046] The EUV light generation processor 5A controls the irradiation timing of the laser device 3 so that the target 27 that has reached the plasma generation region 25 is irradiated with the pulsed laser light 33. When the EUV light generation processor 5A receives the passing timing signal TS1 from the target detection unit 41, it outputs a light emission trigger signal TR that defines the irradiation timing to the laser device 3. The delay circuit 72 delays and outputs the light emission trigger signal TR input from the EUV light generation processor 5A for the delay time until the target 27 reaches the plasma generation region 25 from the target detection region R. Thereby, the target 27 that has reached the plasma generation region 25 is irradiated with the pulsed laser light 33.

[0047] Also, when the EUV light generation processor 5A receives the passing timing signal TS1 from the target detection unit 41, it outputs an imaging timing signal TS2 to the imaging unit 431. The delay circuit 72 delays and outputs the imaging timing signal TS2 input from the EUV light generation processor 5A for the above delay time. Thereby, the imaging unit 431 can image the projection image of the target 27 at the timing when the target 27 reaches the plasma generation region 25.

[0048] The EUV light generation processor 5A receives a burst signal BT from the external device 6 shown in FIG. 2. The burst signal BT is a signal for the external device 6 to request the generation and stop of EUV light to the EUV light generation device 1. The EUV light generation processor 5A generates EUV light while the burst signal BT is on and stops the generation of EUV light while the burst signal BT is off.

[0049] 2.2 Operation FIG. 4 is a main flowchart showing the operation of the EUV light generation system 11A. FIG. 5 is a flowchart showing the target generation process shown in FIG. 4.

[0050] In step S10 of FIG. 4, when a startup instruction is input, the EUV light generation processor 5A starts the EUV light generation system 11A. After startup, the EUV light generation processor 5A outputs a start signal to the target generation processor 52A to start target generation.

[0051] In step S20, when the start signal from the EUV light generation processor 5A is input, the target generation processor 52A starts target generation.

[0052] In step S30, the target generation processor 52A starts EUV light generation. Specifically, the target generation processor 52A operates the laser device 3 and starts irradiating the target 27 with the pulsed laser light 33. When the target 27 is irradiated with the pulsed laser light 33, the target 27 is turned into plasma and EUV light 252 is generated. The EUV light 252 is output to the external device 6. The pulsed laser light 33 has, for example, a pulse time width on the order of picoseconds. The order of picoseconds means 1 ps or more and less than 1 ns. The pulsed laser light 33 may have a pulse width of 1 ns or more and less than 1 μs.

[0053] The target generation in step S20 is performed according to the flowchart shown in FIG. 5. First, in step S210, the target generation processor 52A determines whether the initial setting has been completed. If the initial setting has not been completed (NO in step S210), the process proceeds to the initial setting in step S220.

[0054] In step S220, the target generation processor 52A performs an initial setting based on the initial setting information stored in the memory 523. The initial setting includes temperature adjustment of the heater 261, pressure adjustment of the reservoir 267, adjustment of the driving frequency of the piezo element 264, and the like.

[0055] First, the target generation processor 52A controls the heater 261 via the heater power supply 53 based on the detected value of the temperature sensor 262 so that the target substance in the reservoir 267 reaches a predetermined temperature equal to or higher than the melting point. When tin (Sn) is used as the target substance, the predetermined temperature is from 232°C to 300°C. When the heater 261 is driven, the target substance stored in the reservoir 267 melts and becomes liquid.

[0056] Also, in the initial setting, the target generation processor 52A sets the pressure in the reservoir 267 to the target pressure via the pressure regulator 263 in order to discharge the target substance from the nozzle hole 268. The pressure regulator 263 supplies and exhausts the gas in the reservoir 267 based on the control signal from the target generation processor 52A to set the pressure in the reservoir 267 to the target pressure. The pressure in the reservoir 267 defines the discharge pressure of the target substance discharged from the nozzle hole 268 and, as a result, defines the speed of the droplet-shaped target 27 heading towards the plasma generation region 25. The target pressure is, for example, a pressure in the range from several MPa to 40 MPa. The target speed of the target 27 is, for example, a speed in the range from 60 m / s to 120 m / s.

[0057] Furthermore, in the initial setting, the target generation processor 52A sets the driving frequency of the piezo element 264. As described above, the driving frequency of the piezo element 264 defines the generation frequency f. The driving frequency of the piezo element 264 is adjusted so that the target 27 is generated at the target generation frequency f. The initial setting of the driving frequency of the piezo element 264 is performed while operating the target supply unit 26A and supplying the target 27 to the plasma generation region 25. When pressure is applied to the reservoir 267 with the target substance in a melted state and the piezo element 264 is vibrated, the nozzle 265 vibrates and a plurality of targets 27 are periodically supplied to the plasma generation region 25.

[0058] The EUV light generation processor 5A analyzes the target image TP input from the image measurement unit 43, and calculates the measured value of the generation period of the target 27 from the intervals between a plurality of targets 27 that sequentially pass through the plasma generation region 25. The EUV light generation processor 5A calculates the difference between the calculated measured value of the generation period and the target value of the generation period, and outputs the difference from the target value to the target generation processor 52A. The target generation processor 52A adjusts the drive frequency of the piezo element 264 so that the measured value of the generation period of the target 27 becomes the target value. As a result, the generation frequency f of the target 27 is set to the target value.

[0059] When the initial setting is completed, the EUV light generation processor 5A executes the basic operation of step S230.

[0060] The basic operation of step S230 is an operation of driving the heater 261, the pressure regulator 263, and the piezo element 264 at the temperature, pressure, and drive frequency adjusted in the initial setting. In the basic operation, the target 27 is supplied to the plasma generation region 25 at the target generation frequency f.

[0061] Also, when the initial setting is completed in step S210 (YES in step S210), the process proceeds to step S230 without performing the initial setting of step S220.

[0062] 2.3 Problems In the EUV light generation apparatus 1A according to such a comparative example, when used for a long period of time, the volume of the target 27 may change. The reasons therefor may include changes in the diameter of the nozzle hole 268 of the target supply unit 26A and clogging of the filter 266. One change in the diameter of the nozzle hole 268 is an increase in diameter that occurs when the inner wall is gradually eroded by the target substance passing through the nozzle hole 268. The other is a decrease in diameter that occurs when a compound film of the target substance and another metal is deposited on the inner wall of the nozzle hole 268.

[0063] Figure 6 conceptually shows the generation mechanism of the target 27. Due to the pressure of the reservoir 267, the melted target material is discharged from the nozzle 265. The form of the target material immediately after being discharged from the nozzle 265 is a columnar body whose axial direction extends in the discharge direction. When the nozzle 265 vibrates due to the vibration applied from the piezoelectric element 264, the columnar target material is divided into droplets 127 having a volume smaller than that of the target 27. Among the plurality of droplets 127, some adjacent droplets 127 are combined during the process of traveling along the target orbit 270, and become the droplet-shaped target 27 having a volume larger than that of the droplet 127.

[0064] In FIG. 6, assuming that the diameter of the nozzle hole 268 is d, the velocity in the direction of the target orbit 270 is V, and the generation frequency of the target 27 is f, the diameter D of the target 27 can be calculated by the following formulas (1) and (2). Here, d and D are diameters respectively.

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[0065] The velocity V of the target 27 is defined by the discharge pressure, and the generation frequency f of the target 27 is defined by the drive frequency of the piezoelectric element 264. When the discharge pressure and the drive frequency are constant, that is, when V / f is constant, if the diameter d of the nozzle hole 268 increases, the discharge amount of the target material per unit time increases, so the diameter D of the target 27 increases. Similarly, considering the case where V / f is constant, if the diameter d of the nozzle hole 268 decreases, the discharge amount of the target material per unit time decreases, so the diameter D of the target 27 decreases. The larger the diameter D is, the larger the volume of the target 27 is. Furthermore, even when the diameter d of the nozzle hole 268 does not change, if the filter 266 becomes clogged, the discharge velocity of the target material decreases, and the volume of the target 27 becomes smaller.

[0066] If the volume of the target 27 is too large, the amount of debris generated when the pulsed laser light 33 is irradiated may increase. Also, if the volume of the target 27 is too small, the output of EUV light may decrease, and the change in the volume of the target 27 may make the output of EUV light unstable.

[0067] 3. EUV Light Generation Device of the First Embodiment The EUV light generation device 1B of the first embodiment shown in FIG. 7 will be described. Note that the same components as those described above are denoted by the same reference numerals, and redundant descriptions are omitted unless otherwise specified.

[0068] 3.1 Configuration The difference in configuration between the EUV light generation device 1B of the first embodiment and the EUV light generation device 1A according to the comparative example is only the target generation processor 52B. Functionally, the target generation processor 52B is different from the target generation processor 52A of the comparative example in that it has a function of changing the generation frequency f of the target 27 based on the size of the target 27. To realize such a function, the target generation processor 52B has been improved in the control program and initial setting information.

[0069] 3.2 Operation The operation of the EUV light generation device 1B of the first embodiment will be described. Also in the EUV light generation device 1B, the main flowchart related to EUV light generation is the same as the main flowchart of the EUV light generation device 1A according to the comparative example shown in FIG. 4. The difference is that the content of target generation in step S20 has been changed from the flowchart shown in FIG. 5 to the flowchart shown in FIG. 8 as an example.

[0070] The differences between the flowchart of the first embodiment shown in FIG. 8 and the flowchart of the comparative example shown in FIG. 5 are as follows: The first difference is that the initial setting in step S220 has been changed to the initial setting in step S220B. The second difference is that after the basic operation in step S230 is started, a step for changing the control of the generation frequency f of the target 27 has been added.

[0071] In step S220B, in the target generation processor 52B as well, the initial setting for adjusting the temperature of the heater 261, the pressure of the reservoir 267, and the driving frequency of the piezo element 264 to the target values is performed in the same manner. The difference is that, as information used for the change control of the generation frequency f, an allowable range of the diameter D of the target 27 is set. In the memory 523, the upper limit value Dmax and the lower limit value Dmin of the allowable range are stored as information on the allowable range of the diameter D. In the initial setting of step S220B, the target generation processor 52B reads the allowable range of the diameter D. Further, in step S220B, the target generation processor 52B calculates the frequency ratio N (= f / F) between the irradiation frequency F and the generation frequency f. When the initial setting of step S220B is completed, the target generation processor 52B proceeds to step S230.

[0072] The basic operation in step S230 is the same as the basic operation according to the comparative example shown in FIG. 5. The driving frequency of the piezo element 264 is adjusted such that the generation frequency f of the target 27 becomes the initial target value immediately after the initial setting is completed. After starting the basic operation of step S230, the target generation processor 52B starts the change control of the generation frequency f after step S240.

[0073] In step S240, the target generation processor 52B first acquires the target image TP measured by the image measurement unit 43 from the EUV light generation processor 5A. Then, the diameter D(t) of the target 27 is measured from the target image TP. The diameter D(t) is measured for a plurality of targets 27.

[0074] In step S250, the target generation processor 52B calculates the average value Du(t) of the diameters D(t) of the plurality of targets 27.

[0075] In steps S260 and S270, the target generation processor 52B determines whether or not the diameter D of the target 27 is within the allowable range.

[0076] First, in step S260, the target generation processor 52B compares the average value Du(t) with the upper limit value Dmax of the allowable range. If the average value Du(t) is less than or equal to the upper limit value Dmax (YES in step S260), the process proceeds to step S270. If the average value Du(t) exceeds the upper limit value Dmax (NO in step S260), the process proceeds to step S261.

[0077] Also, in step S270, the target generation processor 52B compares the average value Du(t) with the lower limit value Dmin of the allowable range. If the average value Du(t) is greater than or equal to the lower limit value Dmin (YES in step S270), since the average value Du(t) is within the allowable range, the target generation processor 52B returns to step S30 shown in FIG. 4 without changing the generation frequency f. On the other hand, if the average value Du(t) is less than the lower limit value Dmin (NO in step S270), the process proceeds to step S271.

[0078] In step S261, since the average value Du(t) exceeds the upper limit value Dmax of the allowable range, the generation frequency f is increased so that the average value Du(t) falls within the allowable range. On the other hand, in step S271, since the average value Du(t) is less than the lower limit value Dmin of the allowable range, the target generation processor 52B decreases the generation frequency f so that the average value Du(t) falls within the allowable range.

[0079] The target generation processor 52B changes the generation frequency f by adjusting the driving frequency of the piezoelectric element 264 in steps S261 and S271. In the initial setting of step S220B, the driving frequency of the piezoelectric element 264 is adjusted to an initial target value so that the generation frequency f becomes the target value. The change in the generation frequency f in steps S261 and S271 means changing the target value of the generation frequency f by changing the target value of the driving frequency of the piezoelectric element 264. In target generation, even after the target value of the generation frequency f is changed, the basic operation continues.

[0080] Also, the generation frequency f is changed to a natural number multiple of the irradiation frequency F of the pulsed laser beam 33. That is, in step S261, when increasing the generation frequency f, 1 is added to the frequency ratio N before the change, and the value obtained by multiplying the added value by the irradiation frequency F is set as the generation frequency f after the change. For example, when the target value of the generation frequency f before the change is 120 kHz and the irradiation frequency F is 20 kHz, the frequency ratio N before the change is 6. When increasing the generation frequency f, N + 1 = 6 + 1 = 7, f = N × F = 20 kHz × 7 = 140 kHz, and the generation frequency f is changed from 120 kHz to 140 kHz.

[0081] On the other hand, in step S271, when decreasing the generation frequency f, 1 is subtracted from the initial frequency ratio N, and the value obtained by multiplying the subtracted value by the irradiation frequency F is set as the generation frequency f after the change. For example, when the target value of the generation frequency f before the change is 120 kHz, the irradiation frequency F is 20 kHz, and the frequency ratio N before the change is 6. When decreasing the generation frequency f, N - 1 = 6 - 1 = 5, f = N × F = 20 kHz × 5 = 100 kHz, and the generation frequency f is changed from 120 kHz to 100 kHz. The target generation processor 52B repeats such processing until the diameter d of the target 27 is within the allowable range.

[0082] The change control of the generation frequency f shown in FIG. 8 will be conceptually described with reference to FIG. 9. FIG. 9 is a schematic diagram when increasing the generation frequency f when the diameter D of the target 27 has increased due to an increase in the diameter d of the nozzle hole 268.

[0083] In FIG. 9, taking time t1 as the initial state, the diameter of the nozzle hole 268 in the initial state is d(t1), and the diameter of the target 27 is D(t1). f1 is the initial target value of the generation frequency f. When the time changes from time t1 to time t2 over time, assuming that the diameter d of the nozzle hole 268 becomes larger than d(t1) and changes to d(t2). In this case, the diameter D of the target 27 changes to D(t2) which is larger than D(t1). Even at time t2, since f1 does not change, the irradiation frequency F of the pulsed laser light 33 and the generation frequency f are synchronized in the same manner as in the initial state. Therefore, the pulsed laser light 33 irradiates the target 27, but since the volume of the target 27 has become larger, the amount of debris generated increases compared to time t1.

[0084] When the diameter D(t2) of the target 27 at time t2 exceeds the upper limit value Dmax, the target generation processor 52B increases the driving frequency of the piezoelectric element 264 and increases the generation frequency f as shown in step S261 of FIG. 8. The changed generation frequency f, which is f2, is larger than the previous f1 and is a value that is a natural number multiple of the irradiation frequency F. Time t3 is the time after the generation frequency f is changed to f2. When the generation frequency f increases, the diameter D(t3) of the target 27 decreases. Since f2 is a natural number multiple of the irradiation frequency F, the pulsed laser light 33 irradiates the target 27 even after the generation frequency f is changed. Since the diameter D(t3) of the target 27 at time t3 is smaller than the diameter D(t2) at time t2, the amount of debris generated at time t3 decreases compared to time t2.

[0085] In FIG. 9, for the generation frequency f, both the initial state f1 at times t1 and t2 and f2 at the changed time t3 are natural number multiples of the irradiation frequency F. The relationship between each of f1 and f2 and the irradiation frequency F is shown by Equation (3). Both n1 and n2 are natural numbers. Also, regarding the diameter D of the target 27, the relationship between the diameter D(t3) at time t3 and the diameter D2(t2) at time t2 is shown by Equation (4).

Equation

[0086] Since FIG. 9 shows an example of increasing the generation frequency f, n2 is larger than n1. Also, at time t3, as the generation frequency f becomes higher than at times t1 and t2, the number of targets 27 not irradiated with the pulsed laser beam 33 increases. In FIG. 9, the targets 27 irradiated with the pulsed laser beam 33 are indicated by reference numeral 27A, and the targets 27 not irradiated with the pulsed laser beam 33 are indicated by reference numeral 27B. As an example in FIG. 9, when the generation frequency f is f1, the number of targets 27B existing between two targets 27A is one, whereas after changing to f2, the number of targets 27B has increased to two. Thus, when the generation frequency f is increased, the number of targets 27B not irradiated with the pulsed laser beam 33 increases.

[0087] The example of FIG. 9 corresponds to step S261 in FIG. 8 and is an example of increasing the generation frequency f. Contrary to step S261, as shown in step S271, when the targets 27 become smaller due to a decrease in the diameter d of the nozzle holes 268, the generation frequency f is decreased in order to enlarge the targets 27. In this case, in the above equations (3) and (4), n2 becomes smaller than n1, and f2 becomes smaller than f1.

[0088] Also, FIG. 10 is a schematic diagram showing a case where the generation frequency f is decreased when the diameter D of the targets 27 becomes smaller, contrary to the example of FIG. 9. Furthermore, the example of FIG. 10 is different from the example of FIG. 9 and is an example in which the cause of the decrease in the diameter D of the targets 27 is not an increase in the diameter d of the nozzle holes 268 but clogging of the filter 266.

[0089] In FIG. 10, at time t2 when time has elapsed from the initial state time t1, the deposition of impurities progresses and a part of the filter 266 is blocked. The diameter d of the nozzle hole 268 does not change at times t1 and t2 and is d(t1). When a part of the filter 266 is blocked, the discharge rate of the target substance discharged from the nozzle hole 268 decreases. As a result, since the discharge amount of the target substance per unit time decreases, the diameter D of the target 27 becomes smaller, and V / f, which is the distance that the target 27 advances per unit time, also becomes smaller. In the example of FIG. 10, the speed V of the target 27 has decreased from V(t1) at time t1 to the speed V(t2) at time t2. However, at times t1 and t2, since the generation frequency f does not change at f1, the irradiation frequency F of the pulsed laser light 33 and the generation frequency f are synchronized. However, when the volume decreases due to the reduction in the diameter D of the target 27, the output of the EUV light decreases.

[0090] When the diameter D(t2) of the target 27 at time t2 becomes less than the lower limit value Dmin, the target generation processor 52B reduces the drive frequency of the piezo element 264 and reduces the generation frequency f as shown in step S271 of FIG. 8. The changed generation frequency f, which is f2, is smaller than the previous f1 and is a value that is a natural multiple of the irradiation frequency F. Time t3 is the time after the generation frequency f is changed to f2. In this case, when the generation frequency f becomes smaller, the diameter D(t3) of the target 27 becomes larger. Since f2 is a natural multiple of the irradiation frequency F, the pulsed laser light 33 is still irradiated onto the target 27 even after the generation frequency f is changed. In the example of FIG. 10, since the diameter D(t3) of the target 27 at time t3 is larger than the diameter D(t2) at time t2, the output of the EUV light at time t3 increases compared to time t2. Contrary to the example of FIG. 9, in the example of FIG. 10, in the above formulas (3) and (4), n2 is smaller than n1 and f2 is smaller than f1.

[0091] 3.3 Operation and Effect As described above, the EUV light generation device 1B of the present embodiment is an EUV light generation device that generates EUV light by plasmaizing the target 27 by irradiating the target 27 with pulsed laser light 33, and includes a chamber 2A, a target supply unit 26A that supplies the target 27 to the plasma generation region 25 in the chamber 2A, a laser device 3A that generates the pulsed laser light 33 irradiated on the target 27, and a target generation processor 52B that changes the generation frequency f of the target 27 generated by the target supply unit 26A to a natural multiple of the irradiation frequency F of the pulsed laser light 33 based on the size of the target 27. Here, the diameter D of the target 27 is an example of the size of the target of the present disclosure, and the target generation processor 52B is an example of the processor of the present disclosure.

[0092] According to such an EUV light generation device 1B of the present embodiment, even when the volume of the target 27 changes due to a change in the diameter d of the nozzle hole 268 or clogging of the filter 266, the following effects can be obtained by changing the generation frequency f. That is, an effect of suppressing an increase in the amount of debris generated and an effect of suppressing a decrease in the output of EUV light.

[0093] Further, in the first embodiment, the EUV light generation device 1B further includes an image measurement unit 43 that images the target 27 and outputs a target image TP, and the target generation processor 52B measures the size of the target 27 from the target image TP. Since the size of the target 27 is directly measured from the target image TP, the determination accuracy of whether the size of the target 27 is within the allowable range may be higher than when the target image TP is not used.

[0094] Also, in the first embodiment, an allowable range of the size of the target 27 is preset, and when the size of the target 27 exceeds the upper limit value Dmax of the allowable range, the target generation processor 52B increases the generation frequency f, and when the size of the target 27 is less than the lower limit value Dmin of the allowable range, the target generation processor 52B decreases the generation frequency f. By setting the allowable range, since the generation frequency f is not changed within the allowable range, for example, compared with the control according to one threshold value instead of the allowable range, the control load can be suppressed.

[0095] Also, in the first embodiment, the target generation processor 52B compares the average value Du of the diameter D, which is an example of the sizes of the plurality of measured targets 27, with the upper limit value Dmax and the lower limit value Dmin. Thereby, even if there are fluctuations in the measured values, relatively stable control becomes possible. Here, the average value Du is an example of a representative value of the present disclosure. As the representative value, in addition to the average value Du, the median value of the plurality of measured values may be used.

[0096] Also, although the diameter D of the target 27 is used as the size of the target 27, the volume of the target 27 may also be used. In this case, for example, a plurality of image measurement units 43 with different imaging directions are provided. Then, the diameter D is measured from each of the target images TP captured by each image measurement unit 43, and the volume of the target 27 is obtained by calculation from the plurality of measured diameters D. Also, a pressure sensor for measuring the pressure at the time of collision of the target 27 may be provided in the target recovery unit 28, and the volume of the target 27 may be obtained by calculation from the pressure value measured by the pressure sensor. The method of calculating the volume from the pressure value is, for example, calculating the mass of the target 27 from the pressure value and obtaining the volume from the mass and the density of the target substance.

[0097] 4. EUV Light Generation Device of the Second Embodiment Next, the EUV light generation device of the second embodiment will be described. Note that the same components as those described above are denoted by the same reference numerals, and redundant descriptions are omitted unless otherwise specified.

[0098] 4.1 Configuration The basic configuration of the EUV light generation device according to the second embodiment is substantially the same as that of the EUV light generation device 1B according to the first embodiment. Therefore, the description of the overall configuration is omitted. The difference in configuration between the EUV light generation device according to the second embodiment and the EUV light generation device 1B according to the first embodiment lies only in the target generation processor 52C shown in FIG. 11. The target generation processor 52C has a function of changing the generation frequency f of the target 27 based on the size of the target 27, which is common to the EUV light generation device 1B according to the first embodiment, but the implementation method is different. In response to the change in this implementation method, the target generation processor 52C has been improved in the control program and initial setting information.

[0099] That is, the target generation processor 52C according to the second embodiment changes the generation frequency f of the target 27 based on the related information related to the size of the target 27, rather than the size of the target 27 itself. More specifically, in the second embodiment, the related information is the elapsed time t from a preset time point, and the target generation processor 52C changes the generation frequency f based on the elapsed time t. As shown in the first embodiment, the diameter d of the nozzle hole 268 changes over time, and the filter 266 also becomes clogged over time. Therefore, the elapsed time t can be said to be related information related to the size of the target 27.

[0100] As shown in FIG. 11, the target generation processor 52C has a timer - 522. The timer 522 is an example of an elapsed time measurement unit that measures the elapsed time t from a preset time point. In this example, as the elapsed time t, the cumulative value of the operation time of the target supply unit 26A is used. The target generation processor 52C causes the timer 522 to measure the operation time of the target supply unit 26A, and updates the elapsed time t in the memory 523 based on the measured value.

[0101] In addition to the initial setting information and the elapsed time t, a reference table 524 is stored in the memory 523. As shown in FIG. 12, the reference table 524 records the correspondence between a plurality of reference times RX to be compared with the elapsed time t and a plurality of generated frequencies f set corresponding to each of the plurality of reference times RX. In this example, the memory 523, which is an internal storage device of the target generation processor 52C, stores the correspondence, but an external storage device of the target generation processor 52C may store the correspondence.

[0102] For example, as shown in FIG. 13, the reference table 524 is created on the premise that the diameter d of the nozzle hole 268 increases as the elapsed time t increases. When assuming the relationship shown in FIG. 13, since the diameter D of the target 27 increases as the elapsed time t increases, in order to reduce the diameter D, it is necessary to increase the generated frequency f. Therefore, in the reference table 524, the generated frequency f increases as the reference time RX increases. The reference time RX and the generated frequency f correspond one-to-one. The reference number RN is a number assigned for each combination of the reference time RX and the generated frequency f.

[0103] The reference table 524 is created, for example, by measuring the change in the size of the target 27 according to the elapsed time t and assigning an appropriate generated frequency f according to the elapsed time t based on the measured values.

[0104] 4.2 Operation Next, the operation of the EUV light generation apparatus according to the second embodiment will be described using the flowchart shown in FIG. 14.

[0105] Also in the EUV light generation apparatus according to the second embodiment, the main flowchart related to EUV light generation is the same as the main flowchart of the EUV light generation apparatus 1A according to the comparative example shown in FIG. 4. The difference is that the content of target generation in step S20 is changed from the flowchart shown in FIG. 5 to the flowchart shown in FIG. 14 as an example.

[0106] The differences between the flowchart of the second embodiment shown in FIG. 14 and the flowchart of the first embodiment shown in FIG. 8 are as follows. The first difference is that the initial setting in step S220B is changed to step S220C. The second difference is that the control for changing the generation frequency f of the target 27 after step S3 3 0 is different.

[0107] In the initial setting of step S220C, even in the target generation processor 52C, the initial setting for adjusting the temperature of the heater 261, the pressure of the reservoir 267, and the driving frequency of the piezo element 264 to the target values is performed in the same manner as in the first embodiment. The difference is that the target generation processor 52C reads the reference table 524 instead of the allowable range. When the initial setting of step S220C is completed, the target generation processor 52C proceeds to step S230.

[0108] The basic operation in step S230 is the same as in the first embodiment. After starting the basic operation in step S230, the target generation processor 52C proceeds to step S310.

[0109] In step S310, the target generation processor 52C selects the reference number RNk of the reference table 524. The elapsed time t is the cumulative value of the operation time. Therefore, when the EUV light generation apparatus is stopped, the target generation processor 52C stores the value of k of the reference number RNk at the time of stop in the memory 523. When the EUV light generation apparatus is restarted, the target generation processor 52C proceeds to NO in step S210, passes through step S220C and step S230, and proceeds to step S310. In step S310, the target generation processor 52C reads the value of k stored in the memory 523 at the previous stop, and selects the reference number RNk corresponding to the value of k. Then, the combination of the reference time RTk and the generation frequency fk corresponding to the reference number RNk is read.

[0110] In step S320, the target generation processor 52C activates the timer 522 and starts measuring the elapsed time t. After step S320, the target generation processor 52C starts the change control of the generation frequency f after step S330.

[0111] In step S330, the target generation processor 52C compares the elapsed time t with the reference time RXk corresponding to the selected reference number RNk. If the elapsed time t does not reach the reference time RXk, it returns to step S30 shown in FIG. 4 without changing the generation frequency f. If the elapsed time t reaches the reference time RXk (YES in S330), the target generation processor 52C proceeds to step S340.

[0112] In step S340, the target generation processor 52C changes the generation frequency f to the generation frequency fk corresponding to the reference time RXk. When the generation frequency f is changed, it proceeds to step S350.

[0113] In step S350, the target generation processor 52C updates the reference number RNk by adding 1 to the value of k. After step S350, the target generation processor 52C returns to step S210. Then, when the initial setting has been completed in step S210 (YES in step S210), the target generation processor 52C proceeds to step S330. The target generation processor 52C repeats the above processing until the EUV light generation apparatus stops.

[0114] 4.3 Operations and Effects As described above, in the first embodiment, the generation frequency f was changed based on the size of the target 27 based on the image data. However, in the second embodiment, without measuring the size of the target 27, the generation frequency f is changed based on the elapsed time t from a preset time point. Also in the second embodiment, the effects of suppressing the increase in the amount of debris generated and stabilizing the output of EUV light are the same as in the first embodiment.

[0115] Also, in the second embodiment, as the elapsed time t, the cumulative value of the operation time of the target supply unit 26A is used. As described above, the causes of the change in the diameter D of the target 27 are considered to be the change in the diameter d of the nozzle hole 268 and the clogging of the filter 266. It is considered that both of these have a high correlation with the operation time of the target supply unit 26A. Therefore, by using the cumulative value of the operation time of the target supply unit 26A as the elapsed time t, it is considered that it is possible to perform more appropriate control for changing the generation frequency f than when the cumulative value of the operation time is not used.

[0116] Note that as the elapsed time t, the stop period during which the target supply unit 26A is stopped may be included. Even when the target supply unit 26A is stopped, the change in the diameter d of the nozzle hole 268 or the clogging of the filter 266 may progress. Including the stop period in the elapsed time t is effective in such cases.

[0117] Also, in the second embodiment, the target generation processor 52C increases the generation frequency f as the elapsed time t becomes longer. Therefore, compared with the case of increasing or decreasing the generation frequency f, there may be a case where the control for changing the generation frequency f can be simplified. Of course, when the clogging of the filter 266 is dominant as the cause of the change in the size of the target 27, the generation frequency f may be decreased as the elapsed time t becomes longer.

[0118] Also, in the second embodiment, a reference table 524 is used that records the correspondence between a plurality of reference times RX compared with the elapsed time t and a plurality of generation frequencies f set corresponding to each of the plurality of reference times RX. And, in the second embodiment, the target generation processor 52C includes a memory 523 that stores the reference table 524 in advance, and refers to the reference table 524 to change to the generation frequency f according to the elapsed time t. In this way, by using a correspondence such as the reference table 524, it may be easier to make a more flexible response than when defining the relationship between the elapsed time t and the generation frequency f by a mathematical formula. For example, when the diameter D of the target 27 changes due to a complex factor such as a change over time in the diameter d of the nozzle hole 268 and a clogging over time of the filter 266, the relationship between the elapsed time t and the generation frequency f may become complicated. A method using a reference table 524 or the like that records the correspondence in such a case is effective. Also, the reference table 524 may be easier to maintain, such as modification and update, compared with a mathematical formula.

[0119] 5. EUV Light Generation Apparatus of the Third Embodiment Next, an EUV light generation apparatus of the third embodiment will be described with reference to FIGS. 15 to 19. Note that the same components as those described above are denoted by the same reference numerals, and redundant descriptions are omitted unless otherwise specifically described.

[0120] 5.1 Configuration The configuration of the EUV light generation apparatus according to the third embodiment differs from that of the EUV light generation apparatus 1B according to the first embodiment in that it includes a refill mechanism 91A as shown in FIG. 15. Further, the third embodiment is the same as the first embodiment in that the generation frequency f is changed based on the diameter D of the target 27, but the method for measuring the diameter D of the target 27 is different. In the first embodiment, the diameter D of the target 27 is measured from the target image TP. In contrast, in the third embodiment, the diameter D of the target 27 is calculated from the replenishment amount of the refill mechanism 91A. So to speak, while the first embodiment directly measures the target 27, the third embodiment indirectly measures the diameter D of the target 27 based on the replenishment amount. Hereinafter, the differences will be mainly described.

[0121] As shown in FIG. 15, the refill mechanism 91A is a mechanism for replenishing the target substance to the reservoir 267 of the target supply unit 26D. The refill mechanism 91A includes a tank 97A, a metering unit 96A, a pipe 98A, a load lock chamber 92A, and a liquid level sensor 73A. The tank 97A stores solid tin, which is a solid target substance, as the material of the target 27. The solid tin is, for example, spherical. The metering unit 96A measures the mass of the solid tin supplied from the tank 97A to the pipe 98A. The metering unit 96A, for example, counts the number of solid tin supplied. Since the mass of each solid tin is known, the mass of the solid tin supplied can be calculated based on the mass and the number supplied.

[0122] The load lock chamber 92A is provided on the downstream side of the metering unit 96A in the supply direction of the solid tin. The load lock chamber 92A is connected to the reservoir 267 via an openable supply port and temporarily holds the solid tin transferred from the metering unit 96A. The load lock chamber 92A opens the supply port with the pressure inside the chamber and the tank 97A being the same, and replenishes the solid tin into the reservoir 267.

[0123] The liquid level sensor 73A detects the liquid level of the liquid target substance in the reservoir 267. The liquid level sensor 73A in this example is rod-shaped and has a detection area for detecting the liquid level at one location in the longitudinal direction. The liquid level sensor 73A detects whether the position of the liquid level of the target substance has reached the detection area or not. The liquid level sensor 73A outputs a detection signal to the target generation processor 52D, for example, when the position of the liquid level has reached the detection area, and does not output a detection signal when it has not reached the detection area. The liquid level sensor 73A is provided such that the detection area is located at the height of the liquid level in a state where the target substance in the reservoir 267 is filled up to the target value. Therefore, when the liquid level position of the target substance in the reservoir 267 exceeds the target liquid level height, a detection signal is output from the liquid level sensor 73A to the target generation processor 52D, but when the target substance is less than the target liquid level height, no detection signal is output from the liquid level sensor 73A to the target generation processor 52D. When the target generation processor 52D is receiving the detection signal, it determines that filling of the target substance is unnecessary, and when it is not receiving the detection signal, it determines that filling of the target substance is necessary.

[0124] When the target substance is discharged from the nozzle 265, the liquid level in the reservoir 267 drops. Then, when the target generation processor 52D stops receiving the detection signal from the liquid level sensor 73A, it activates the refill mechanism 91A and supplies solid tin to the reservoir 267 until it receives the detection signal again. That is, the target generation processor 52D causes the refill mechanism 91A to supply solid tin so that the liquid level of the target substance in the reservoir 267 is kept at or above the target liquid level position.

[0125] Let the discharge amount of the target substance from the reservoir 267 be Qout, and the replenishment amount from the refilling mechanism 91A to the reservoir 267 be Qin. The replenishment amount Qin is the mass of solid tin supplied to the reservoir 267 during replenishment. Assuming that Qin and Qout are approximately equal, for the replenishment amount Qin of the refilling mechanism 91A and the diameter D of the target 27, the relationships shown in the following equations (5) and (6) hold. Therefore, if Qin is known, based on equations (5) and (6), the target generation processor 52D can calculate the diameter D of the target 27.

Equation

Equation

[0126] Further, FIG. 16 is a graph showing an example of the change over time of the total mass M of solid tin replenished by the refilling mechanism 91A to the reservoir 267. Let the mass of the replenishment amount Qin per unit time be ΔM. In FIG. 16, ΔM2 is larger than ΔM1 as time elapses. In FIG. 16, Δt1 and Δt2 are the same time. FIG. 16 shows an example in which when the diameter d of the nozzle hole 268 or the discharge speed of the target substance changes, the discharge amount Qout changes, and accordingly the replenishment amount Qin changes. Also, if the mass ΔM of the replenishment amount Qin per unit time Δt and the density ρ of the liquid tin, which is the material of the target substance in the reservoir 267, are used, the replenishment amount Qin can be calculated by the following equation (7).

Equation

[0127] 5.2 Operation Next, with reference to the flowchart shown in FIG. 17, the operation of the EUV light generation apparatus according to the third embodiment will be described. The differences between the flowchart shown in FIG. 17 and the flowchart of the first embodiment shown in FIG. 8 are only steps S540 and S550. Since the others are the same, the differences will be described.

[0128] In step S540, the target generation processor 52D measures the mass ΔM per unit time Δt by the metering unit 96A, and calculates the supply amount Qin from ΔM based on Equation (7). After step S540, the process proceeds to step S550.

[0129] In step S550, the target generation processor 52D calculates the diameter D(t) of the target 27 at time t from the supply amount Qin based on Equation (6). After step S250, it is the same as the first embodiment, and the target generation processor 52D changes the generation frequency f based on the diameter D(t) of the target 27.

[0130] (Modification of the Third Embodiment) FIGS. 18 and 19 are modifications of the third embodiment. In the example shown in FIGS. 15 to 17, the diameter D of the target 27 was calculated from the supply amount Qin, but in the modifications shown in FIGS. 18 and 19, the diameter D of the target 27 is calculated from the replenishment interval.

[0131] As shown in FIG. 18, the refilling mechanism 91B of the modification includes a tank 97B, a heater 281, a pipe 98B, a valve 92B, and a liquid level sensor 73B. The tank 97B can be heated by the heater 281, and the target substance is stored in the tank 97B. The target substance is, for example, liquid tin. The tank 97B is connected to the reservoir 267 via the pipe 98B. A valve 92B for starting and stopping replenishment is provided in the middle of the pipe 98B.

[0132] The target substance in the reservoir 267 is also liquid tin, and the liquid level sensor 73B detects the liquid level of the liquid tin in the reservoir 267. The liquid level sensor 73B is the same as the liquid level sensor 73A shown in FIG. 15 in that it has only one detection area for detecting the liquid level. However, unlike the liquid level sensor 73A shown in FIG. 15, the liquid level sensor 73B is arranged such that the detection area is located at the height of the preset lower limit value of the liquid level of the liquid tin. The liquid level sensor 73B outputs a detection signal when the liquid level of the liquid tin is at a height equal to or higher than the lower limit value, and does not output a detection signal when the liquid level of the liquid tin is lower than the lower limit value. When the refill mechanism 91B does not receive the detection signal from the liquid level sensor 73B, it determines that the liquid level of the liquid tin in the reservoir 267 has dropped below the lower limit value. When the liquid level drops below the lower limit value, the refill mechanism 91B replenishes a preset amount of the target substance. The amount Qin of one-time replenishment by the refill mechanism 91B is constant.

[0133] As shown in FIG. 19, in the modified example, even if the diameter d of the nozzle hole 268 or the like changes, the mass m of the liquid tin corresponding to the amount Qin of one-time replenishment is constant, but the replenishment interval td changes. The example shown in FIG. 19 shows an example in which the replenishment interval td is shortened from td1 to td2 due to an increase in the diameter d of the nozzle hole 268.

[0134] In the case of the modified example, the volume of the liquid tin corresponding to the amount Qin of one-time replenishment can be calculated by dividing the mass m by the density ρ. The amount Qin of replenishment in the modified example is calculated by further dividing the calculated value of m / ρ by the replenishment interval td. If this amount Qin of replenishment is applied to Qin in the above formula (6), the diameter D of the target 27 can be calculated. The modified example is the same as the flowchart of FIG. 17 in other respects.

[0135] 5.3 Operations and Effects As described above, the EUV light generation apparatus according to the third embodiment further includes a refill mechanism 91A or 91B that replenishes the material of the target 27 to the target supply unit exemplified by the target supply unit 26D or 26E, and the target generation processor 52D changes the generation frequency f based on the replenishment amount Qin of the refill mechanism 91A or the replenishment interval td of the refill mechanism 91B. The third embodiment is effective, for example, when the target image TP cannot be acquired as in the first embodiment.

[0136] Further, the replenishment amount Qin is the replenishment amount Qin per unit time of the refill mechanism 91A, and the replenishment interval td is the replenishment interval td when the replenishment amount Qin per time of the refill mechanism 91B is fixed. The target generation processor 52D calculates the size of the target 27 based on the replenishment amount Qin or the replenishment interval td. In the third embodiment, by converting the replenishment amount Qin or the replenishment interval td into the size of the target 27, the common part of the first embodiment can be reused.

[0137] Further, since the third embodiment uses the allowable range of the size of the target 27, it has the same effect as the example of using the allowable range in the first embodiment.

[0138] Also, in the third embodiment, the size of the target 27 is measured from the replenishment amount Qin or the replenishment interval td, but it is not necessary to measure the size of the target 27. For example, as in the second embodiment, a reference table recording the correspondence between the replenishment amount Qin and the generation frequency f may be used, and the generation frequency f may be controlled to be changed by the reference table. The replenishment amount Qin or the replenishment interval td has a correlation with the size of the target 27. Therefore, the replenishment amount Qin or the replenishment interval td is also an example of the "related information related to the size of the target" of the present disclosure.

[0139] 6. EUV Light Generation Apparatus According to the Fourth Embodiment Next, an EUV light generation apparatus according to a fourth embodiment will be described. Note that components similar to those described above are denoted by the same reference numerals, and redundant descriptions will be omitted unless otherwise specified.

[0140] 6.1 Configuration The configuration of the EUV light generation apparatus according to the fourth embodiment is the same as that of the EUV light generation apparatus 1B according to the first embodiment, and thus the description thereof will be omitted. The EUV light generation apparatus according to the fourth embodiment includes a target detection unit 41 that optically detects a target 27 traveling from a target supply unit 26A toward a plasma generation region 25 and outputs a passing timing signal having a signal intensity corresponding to the size of the passing target 27. Note that since the overall configuration diagram of the EUV light generation apparatus according to the fourth embodiment is omitted, for convenience, the target generation processor in the fourth embodiment is denoted by the same reference numeral as that in the first embodiment and will be described as a target generation processor 52B. As described below, the content of the change control of the generation frequency f of the target generation processor 52B in the fourth embodiment is different from that of the target generation processor 52B in the first embodiment. The target generation processor 52B in the fourth embodiment changes the generation frequency f based on the signal intensity. This is different from the EUV light generation apparatus 1B according to the first embodiment in that the generation frequency f of the target 27 is changed based on the signal intensity of the passing timing signal output by the target detection unit 41.

[0141] The fourth embodiment will be described with reference to FIGS. 20 to 22. FIG. 20 is a diagram schematically showing how the target 27 passes through the target detection unit 41. As described in the first embodiment, the optical sensor 412 of the target detection unit 41 outputs a light reception signal having a signal intensity corresponding to the amount of received light. When the target 27 passes through the target detection region R, the target 27 blocks the illumination light traveling from the light emitting unit 41B toward the light receiving unit 41A, so that the signal intensity of the light reception signal, which is the output of the optical sensor 412, changes. The target detection unit 41 detects the target 27 based on the change in the signal intensity when the target 27 passes through.

[0142] FIG. 21 is a graph showing the change over time of the signal intensity I of the light reception signal output by the optical sensor 412 when the target 27 passes through the target detection region R. In FIG. 21, the signal intensity I0 is the signal intensity output by the optical sensor 412 when the target 27 has not passed through, and the signal intensity I0 serves as the baseline. When the target 27 has not passed through, the illumination light is not blocked by the target 27, so the baseline signal intensity I0 represents the maximum value of the signal intensity I. When the target 27 passes through the target detection region R, a part of the illumination light is blocked by the target 27, so the signal intensity I decreases. And the larger the size of the target 27, the more the signal intensity I decreases, and the larger the change amount ΔI from the signal intensity I0 which is the baseline. On the other hand, the smaller the size of the target 27, the smaller the decrease in the signal intensity I, and the smaller the change amount ΔI from the signal intensity I0 which is the baseline.

[0143] Since there is a correlation between the size of the target 27 and the size of the change amount ΔI in this way, the change amount ΔI is an example of the "relevant information related to the size of the target" in the present disclosure. In the fourth embodiment, the target generation processor 52B changes the generation frequency f based on the signal intensity I. Specifically, in this example, the signal intensity I of calculates the change amount ΔI from the baseline, and changes the generation frequency f based on the change amount ΔI.

[0144] In the fourth embodiment, the allowable range of the change amount ΔI is set in the memory 523 of the target generation processor 52B. As shown in FIG. 21, the lower limit value of the allowable range of the change amount ΔI is ΔImin, and the upper limit value is ΔImax.

[0145] 6.2 Operation Next, the operation of the EUV light generation device according to the fourth embodiment will be described. Specifically, with reference to FIG. 22, the operation of the target generation processor 52B according to the fourth embodiment will be described.

[0146] Figure 22 is a flowchart of the fourth embodiment. Steps S210 and S230 are the same as those in the first embodiment. In the fourth embodiment, in the initial setting of step S220E, an upper limit value ΔImax and a lower limit value ΔImin are read as the allowable range of the change amount ΔI.

[0147] When step S230 ends, the target generation processor 52B executes change control of the generated frequency f after step S650. In step S650, the target generation processor 52B acquires the passing timing signal for each target 27 and calculates the change amount ΔI of the signal intensity I from the baseline. The calculated change amount ΔI is stored in the memory 523.

[0148] In step S660, the target generation processor 52B calculates the average value ΔIμ of the plurality of change amounts ΔI for the plurality of targets 27.

[0149] In step S670, the target generation processor 52B compares the average value ΔIμ with the upper limit value ΔImax. If the average value ΔIμ exceeds the upper limit value (NO in step S670), it is considered that the target 27 is too large. In this case, the target generation processor 52B increases the generated frequency f. Thereby, the size of the target 27 can be reduced. In step S670, if the average value ΔIμ is less than or equal to the upper limit value (YES in step S670), the process proceeds to step S680.

[0150] In step S680, the target generation processor 52B compares the average value ΔIμ with the lower limit value ΔImin. If the average value ΔIμ is less than the lower limit value (NO in step S680), it is considered that the target 27 is too small. In this case, the target generation processor 52B decreases the generated frequency f. Thereby, the size of the target 27 can be increased. In step S680, if the average value ΔIμ is greater than or equal to the lower limit value (YES in step S680), the process proceeds to step S680 without changing the generated frequency f.

[0151] 6.3 Function and Effect As described above, the EUV light generation apparatus according to the fourth embodiment includes a target detection unit 41 that detects a passing timing signal, and includes a target generation processor 52B that changes the generation frequency f based on the signal intensity I of the passing timing signal of the target 27. Therefore, the fourth embodiment is effective when the size of the target 27 cannot be measured from the target image TP.

[0152] The fourth embodiment uses an allowable range as shown in FIG. 22. Therefore, the same effect of using the allowable range as in the first embodiment can be obtained. Further, in the fourth embodiment, a representative value of the change amounts ΔI of a plurality of signal intensities I is compared with the upper limit value Imax or the lower limit value Imin of the allowable range. The same effect as in the first embodiment can also be obtained for this.

[0153] Note that in the fourth embodiment, an example has been described in which the change amount ΔI of the signal intensity I is used as related information and the generation frequency f is changed based on the change amount ΔI, but the generation frequency f may be changed using a reference table in which the correspondence relationship between the signal intensity I or the change amount ΔI and the generation frequency f is recorded.

[0154] 7. EUV Light Generation Apparatus of the Fifth Embodiment Next, the EUV light generation apparatus 1F of the fifth embodiment will be described. Note that the same components as those described above will be denoted by the same reference numerals, and redundant descriptions will be omitted unless otherwise specifically described. 7.1 Configuration FIG. 23 is a diagram schematically showing the configuration of the EUV light generation apparatus 1F according to the fifth embodiment. The EUV light generation apparatus 1F according to the fifth embodiment is different in that it includes a laser apparatus 3F and a laser light traveling direction control unit 34F instead of the laser apparatus 3A and the laser light traveling direction control unit 34A of the EUV light generation apparatus 1B according to the first embodiment.

[0155] The laser device 3F includes a pre-pulse laser 3P and a main-pulse laser 3M. The pre-pulse laser 3P is configured to output pre-pulse laser light 31P. The main-pulse laser 3M is configured to output main-pulse laser light 31M. The pre-pulse laser 3P is composed of, for example, a YAG laser device or a laser device using Nd:YVO4. The main-pulse laser 3M is composed of, for example, a CO2 laser device. The main-pulse laser 3M may also be composed of a YAG laser device or a laser device using Nd:YVO4.

[0156] The laser light traveling direction control unit 34F includes high reflection mirrors 343, 344, and 345 and a combiner 346. The high reflection mirrors 343 and 344 are arranged on the optical path of the main-pulse laser light 31M. The high reflection mirror 345 is arranged on the optical path of the pre-pulse laser light 31P.

[0157] The combiner 346 is arranged on the optical paths of the pre-pulse laser light 31P reflected by the high reflection mirror 345 and the main-pulse laser light 31M reflected by the high reflection mirror 344. The combiner 346 is configured to reflect the pre-pulse laser light 31P with a high reflectivity and transmit the main-pulse laser light 31M with a high transmittance. The high reflection mirror 344 and the combiner 346 are configured to reflect the main-pulse laser light 31M and the pre-pulse laser light 31P toward the inside of the chamber 2A. The combiner 346 is configured to substantially align the optical axes of the pre-pulse laser light 31P and the main-pulse laser light 31M.

[0158] The fifth embodiment includes an image measurement unit 43 similar to that of the first embodiment. FIG. 24 is a diagram schematically showing a state in which the image measurement unit 43 detects a mist-like target. The image measurement unit 43 images a mist-like target 27A that has been irradiated with a prepulse laser beam 31P and is in a diffused state as a target instead of the droplet-like target 27 of the first embodiment. The target generation processor 52B measures the size of the mist-like target 27A from the target image TP output from the image measurement unit 43 using the target image TP. Other aspects are the same as those of the first embodiment.

[0159] 7.2 Operation Next, the operation of the EUV light generation apparatus 1F according to the fifth embodiment is substantially the same as that of the first embodiment. The difference is that the first embodiment changes the generation frequency f based on the diameter D of the droplet-like target 27, while the fifth embodiment changes the generation frequency f based on the diameter D of the mist-like target 27A.

[0160] 7.3 Function and Effect The EUV light generation apparatus 1F according to the fifth embodiment can also obtain the same effects as those of the first embodiment. Also, the fifth embodiment may be combined with the second to fourth embodiments.

[0161] 8. Others FIG. 25 schematically shows the configuration of the exposure apparatus 6A connected to the EUV light generation apparatus 1B. In FIG. 24, the exposure apparatus 6A as the external apparatus 6 includes a mask irradiation unit 68 and a workpiece irradiation unit 69. The mask irradiation unit 68 illuminates the mask pattern on the mask table MT through a reflective optical system with the EUV light incident from the EUV light generation apparatus 1B. The workpiece irradiation unit 69 forms an image of the EUV light reflected by the mask table MT on a workpiece (not shown) arranged on the workpiece table WT through a reflective optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure apparatus 6A exposes the workpiece to the EUV light reflecting the mask pattern by synchronously translating the mask table MT and the workpiece table WT in parallel. By transferring the device pattern to the semiconductor wafer through the above exposure process, an electronic device can be manufactured.

[0162] FIG. 26 schematically shows the configuration of the inspection apparatus 6B connected to the EUV light generation apparatus 1B. In FIG. 26, the inspection apparatus 6B as the external apparatus 6 includes an illumination optical system 63 and a detection optical system 66. The EUV light generation apparatus 1B outputs EUV light to the inspection apparatus 6B as a light source for inspection. The illumination optical system 63 reflects the EUV light incident from the EUV light generation apparatus 1B and irradiates the mask 65 arranged on the mask stage 64. The mask 65 here includes mask blanks before the pattern is formed. The detection optical system 66 reflects the EUV light from the illuminated mask 65 and forms an image on the light receiving surface of the detector 67. The detector 67 that receives the EUV light acquires an image of the mask 65. The detector 67 is, for example, a TDI (time delay integration) camera. Based on the image of the mask 65 obtained through the above process, defects of the mask 65 are inspected, and using the inspection results, a mask suitable for manufacturing an electronic device is selected. Then, an electronic device can be manufactured by exposing and transferring the pattern formed on the selected mask onto a photosensitive substrate using the exposure apparatus 6A.

[0163] Note that, in the inspection apparatus 6B, the above-described EUV condenser mirror 23 may be an oblique incidence type. Also, in FIGS. 25 and 26, instead of the EUV light generation apparatus 1B, any one of the EUV light generation apparatuses of the second to fifth embodiments may be used.

[0164] The above description is intended to be illustrative only and not limiting. Thus, it will be apparent to those skilled in the art that various changes may be made to each embodiment of the present disclosure without departing from the scope of the appended claims.

[0165] The terms used throughout this specification and the appended claims are to be construed as "non-limiting" terms. For example, the terms "comprising" or "comprised of" should be construed as not being limited to the elements listed as being included. The term "having" should be construed as not being limited to the elements listed as being had. Also, the modifier "one" described in this specification and the appended claims should be construed to mean "at least one" or "one or more". Also, the term "at least one of A, B, and C" should be construed as "A", "B", "C", "A + B", "A + C", "B + C", or "A + B + C", and further should be construed to include combinations with things other than "A", "B", and "C".

Claims

1. An EUV light generating apparatus that generates EUV light by irradiating a target with pulsed laser light to turn the target into plasma, comprising: a chamber; a target supply unit that supplies the target to a plasma generation region within the chamber; a pulsed laser device that generates pulsed laser light for irradiating the target; a processor that changes the generation frequency of the target generated by the target supply unit to a natural multiple of the irradiation frequency of the pulsed laser light based on the size of the target or related information related to the size of the target; An EUV light generating apparatus comprising the above components.

2. The EUV light generating apparatus according to Claim 1, further comprising an image measurement unit that images the target and outputs a target image, wherein the processor measures the size of the target from the target image. An EUV light generating apparatus.

3. The EUV light generating apparatus according to Claim 2, wherein a tolerance range for the size of the target is preset, and the processor increases the generation frequency when the size of the target exceeds the upper limit of the tolerance range and decreases the generation frequency when the size of the target is less than the lower limit of the tolerance range. An EUV light generating apparatus.

4. The EUV light generating apparatus according to Claim 3, wherein the processor compares a representative value of the sizes of a plurality of measured targets with the upper limit or the lower limit. An EUV light generating apparatus.

5. The EUV light generating apparatus according to Claim 1, further comprising an elapsed time measurement unit that measures the elapsed time from a preset time point, wherein the related information is the elapsed time, and the processor changes the generation frequency based on the elapsed time. An EUV light generating apparatus.

6. The EUV light generating apparatus according to Claim 5, wherein the elapsed time is an accumulated value of the operating time of the target supply unit. An EUV light generating apparatus.

7. The EUV light generating apparatus according to Claim 6, wherein the processor increases the generation frequency as the elapsed time becomes longer. An EUV light generating apparatus.

8. The EUV light generating apparatus according to Claim 6, further comprising a storage device that stores in advance a correspondence relationship between a plurality of reference times to be compared with the elapsed time and a plurality of generation frequencies set corresponding to each of the plurality of reference times. The EUV light generating device, wherein the processor refers to the correspondence relationship and changes to the generation frequency according to the elapsed time.

9. The EUV light generating device according to claim 1, further comprising a refill mechanism for replenishing the target material to the target supply unit, wherein the processor changes the generation frequency based on the replenishment amount or the replenishment interval of the refill mechanism.

10. The EUV light generating device according to claim 9, wherein the replenishment amount is the replenishment amount per unit time of the refill mechanism, the replenishment interval is the replenishment interval when the replenishment amount per refill of the refill mechanism is fixed, and the processor calculates the size of the target based on the replenishment amount or the replenishment interval.

11. The EUV light generating device according to claim 10, wherein an allowable range of the size of the target is preset, and the processor increases the generation frequency when the calculated size of the target exceeds the upper limit value of the allowable range, and decreases the generation frequency when the size of the target is below the lower limit value of the allowable range.

12. The EUV light generating device according to claim 1, further comprising a target detection unit that optically detects the target moving from the target supply unit toward the plasma generation region and outputs a passing timing signal having a signal intensity corresponding to the size of the target, wherein the processor changes the generation frequency based on the signal intensity.

13. The EUV light generating device according to claim 12, wherein the related information is the signal intensity, an allowable range of the change amount of the signal intensity from the baseline is preset, and the processor increases the generation frequency when the change amount exceeds the upper limit value of the allowable range, and decreases the generation frequency when the change amount is less than the lower limit value of the allowable range.

14. The EUV light generating device according to claim 13, wherein the processor measures the change amount multiple times and compares a representative value of the measured multiple change amounts with the upper limit value or the lower limit value.

15. The EUV light generating device according to claim 1, The EUV light generation device, wherein the target is in the form of a droplet, and the size of the target is the size of the droplet-shaped target generated by the target supply unit.

16. The EUV light generation device according to claim 1, wherein the pulsed laser device generates prepulse laser light and main pulse laser light as the pulsed laser light, and after irradiating the droplet-shaped target generated by the target supply unit with the prepulse laser light, irradiates the mist-shaped target in which the target has become a diffused state due to the irradiation of the prepulse laser light with the main pulse laser light.

17. The EUV light generation device according to claim 16, further comprising an image measurement unit that images the mist-shaped target and outputs a target image, wherein the processor measures the size of the mist-shaped target from the target image and changes the generation frequency based on the size of the mist-shaped target.

18. The EUV light generation device according to claim 17, wherein a tolerance range for the size of the mist-shaped target is preset, and the processor increases the generation frequency when the size of the mist-shaped target exceeds the upper limit value of the tolerance range, and decreases the generation frequency when the size of the mist-shaped target is below the lower limit value of the tolerance range.

19. A method for manufacturing an electronic device, comprising a chamber, a target supply unit that supplies a target to a plasma generation region in the chamber, a pulsed laser device that generates pulsed laser light for irradiating the target, and a processor that changes the generation frequency of the target to a natural multiple of the irradiation frequency of the pulsed laser light based on the size of the target, wherein, by an EUV light generation device comprising the above, the target is irradiated with pulsed laser light to plasmaize the target and generate EUV light, the EUV light is output to an exposure device, and the method for manufacturing an electronic device includes exposing the EUV light on a photosensitive substrate in the exposure device to manufacture the electronic device.

20. An inspection method, comprising a chamber, a target supply unit that supplies a target to a plasma generation region in the chamber, A pulse laser device that generates pulse laser light for irradiating the target; A processor that changes the generation frequency of the target to a natural multiple of the irradiation frequency of the pulse laser light based on the size of the target; by an EUV light generation device comprising: Irradiating the target with pulse laser light to plasmaize the target and generate EUV light; An inspection method including outputting the EUV light as a light source for inspection to an inspection device, and exposing the mask to the EUV light in the inspection device to inspect the mask.

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