Target generation apparatus, extreme ultraviolet light generation system, and method of manufacturing electronic device

Abstract

When the piezo element is not operating normally, it is necessary to replace the piezo unit, and downtime occurs due to restart of the EUV light generation system. In addition, since the temperature of the reservoir tank is high, replacing the entire target generation device increases the cost.SOLUTION: The target generation device includes a nozzle including a nozzle hole configured to discharge a liquid target material for generating extreme ultraviolet light, a first piezoelectric element disposed at a position different from the nozzle in a first direction and configured to vibrate the nozzle by expanding and contracting in the first direction, and a second piezoelectric element disposed at a position different from the first piezoelectric element in the first direction and configured to vibrate the nozzle via the first piezoelectric element by expanding and contracting in the first direction.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a target generation apparatus, an extreme ultraviolet light generation system, and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in optical lithography for semiconductor processes has progressed rapidly. In the next generation, fine processing of 10 nm or less will be required. For this reason, there is a demand for the development of semiconductor exposure equipment that combines a device for generating extreme ultraviolet (EUV) light with a wavelength of approximately 13 nm and a reduced projection reflective optical system.

[0003] As an EUV light generation device, development of an LPP (Laser Produced Plasma) type device that uses plasma generated by irradiating a target material with laser light is progressing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-182555 [Patent Document 2] U.S. Patent Application Publication No. 2020 / 0166150 [Patent Document 3] Summary of the specification of U.S. Patent Application Publication No. 2012 / 0228526

[0005] A target generation device according to one aspect of the present disclosure includes a nozzle including a nozzle hole that ejects a liquid target material for generating extreme ultraviolet light; a first piezoelectric element that is arranged at a different position in a first direction relative to the nozzle and vibrates the nozzle by expanding and contracting in the first direction; and a second piezoelectric element that is arranged at a different position in the first direction relative to the first piezoelectric element and vibrates the nozzle via the first piezoelectric element by expanding and contracting in the first direction.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating extreme ultraviolet light using an extreme ultraviolet light generation system including: a target generation device including: a nozzle including a nozzle hole that ejects a liquid target material for generating extreme ultraviolet light; a first piezoelectric element that is arranged at a different position in a first direction relative to the nozzle and that vibrates the nozzle by expanding and contracting in the first direction; and a second piezoelectric element that is arranged at a different position in the first direction relative to the first piezoelectric element and that vibrates the nozzle via the first piezoelectric element by expanding and contracting in the first direction; a laser device that irradiates laser light onto the target material ejected from the nozzle; and an EUV collector mirror that collects the extreme ultraviolet light generated by irradiating the target material with the laser light; outputting the extreme ultraviolet light to an exposure device; and exposing a photosensitive substrate in the exposure device to the extreme ultraviolet light to manufacture an electronic device.

[0007] A method for manufacturing an electronic device according to one aspect of the present disclosure includes: irradiating a mask with extreme ultraviolet light generated by an extreme ultraviolet light generation system, the extreme ultraviolet light generation system including: a target generation device including a nozzle including a nozzle hole that ejects a liquid target material for generating extreme ultraviolet light; a first piezoelectric element that is arranged at a different position in a first direction relative to the nozzle and that vibrates the nozzle by expanding and contracting in the first direction; and a second piezoelectric element that is arranged at a different position in the first direction relative to the first piezoelectric element and that vibrates the nozzle via the first piezoelectric element by expanding and contracting in the first direction; a laser device that irradiates laser light onto the target material ejected from the nozzle; and an EUV collector mirror that collects the extreme ultraviolet light generated by irradiating the target material with the laser light, thereby inspecting the mask for defects; selecting a mask using the inspection results; and exposing and transferring a pattern formed on the selected mask onto a photosensitive substrate. [Brief explanation of the drawings]

[0008] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows the configuration of an LPP-type EUV light generation system in a comparative example. [Figure 2] FIG. 2 is a partial cross-sectional view showing the configuration of a target generation device in a comparative example. [Figure 3] FIG. 3 shows the configuration of a piezo unit in a comparative example. [Figure 4] FIG. 4 shows the configuration of a piezo unit in a comparative example. [Figure 5] FIG. 5 shows the configuration of a piezo unit in a comparative example. [Figure 6] FIG. 6 is a flowchart showing the operation of the EUV light generation processor, including the processing to be performed when an abnormality occurs in the piezo unit, in the comparative example. [Figure 7] FIG. 7 shows the configuration of the piezo unit in the first embodiment. [Figure 8] FIG. 8 shows the configuration of the piezo unit in the first embodiment. [Figure 9] FIG. 9 shows the configuration of the piezo unit in the first embodiment. [Figure 10] FIG. 10 is a flowchart showing the operation of the EUV light generation processor, including the processing to be performed when an abnormality occurs in the piezo unit, in the first embodiment. [Figure 11] FIG. 11 shows a switching circuit according to the first embodiment and a first example of its operation. [Figure 12] FIG. 12 shows a switching circuit according to the first embodiment and a first example of its operation. [Figure 13] FIG. 13 shows a switching circuit according to the first embodiment and a first example of its operation. [Figure 14] FIG. 14 shows a switching circuit according to the first embodiment and a second example of its operation. [Figure 15] FIG. 15 shows a switching circuit according to the first embodiment and a second example of its operation. [Figure 16] FIG. 16 shows the switching circuit according to the first embodiment and a second example of its operation. [Figure 17] FIG. 17 shows the configuration of a piezo unit in a first modified example. [Figure 18]FIG. 18 shows the configuration of a piezo unit in a first modified example. [Figure 19] FIG. 19 shows the configuration of a piezo unit in a first modified example. [Figure 20] FIG. 20 shows the configuration of a piezo unit in a second modified example. [Figure 21] FIG. 21 shows the configuration of a piezo unit in a second modified example. [Figure 22] FIG. 22 shows a first example of a switching circuit in the second modified example. [Figure 23] FIG. 23 shows a first example of a switching circuit in the second modified example. [Figure 24] FIG. 24 shows a first example of a switching circuit in the second modified example. [Figure 25] FIG. 25 shows a first example of a switching circuit in the second modified example. [Figure 26] FIG. 26 shows a first example of a switching circuit in the second modified example. [Figure 27] FIG. 27 shows a first example of a switching circuit in the second modified example. [Figure 28] FIG. 28 shows a second example of the switching circuit in the second modified example. [Figure 29] FIG. 29 shows a second example of the switching circuit in the second modified example. [Figure 30] FIG. 30 shows a second example of the switching circuit in the second modified example. [Figure 31] FIG. 31 shows a second example of the switching circuit in the second modified example. [Figure 32] FIG. 32 shows a second example of the switching circuit in the second modified example. [Figure 33] FIG. 33 shows a second example of the switching circuit in the second modified example. [Figure 34] FIG. 34 shows the configuration of a piezo unit in a third modified example. [Figure 35] FIG. 35 shows the configuration of a piezo unit in a third modified example. [Figure 36]FIG. 36 shows the configuration of a piezo unit in a fourth modified example. [Figure 37] FIG. 37 shows the configuration of a piezo unit in a fourth modified example. [Figure 38] FIG. 38 shows the configuration of a piezo unit in the second embodiment. [Figure 39] FIG. 39 shows the configuration of a piezo unit in the second embodiment. [Figure 40] FIG. 40 shows the configuration of a piezo unit in the fifth modified example. [Figure 41] FIG. 41 shows the configuration of a piezo unit in the fifth modified example. [Figure 42] FIG. 42 shows the configuration of a piezo unit in a sixth modified example. [Figure 43] FIG. 43 shows the configuration of a piezo unit in a sixth modified example. [Figure 44] FIG. 44 shows the configuration of a piezo unit in the seventh modified example. [Figure 45] FIG. 45 shows the configuration of a piezo unit in the seventh modified example. [Figure 46] FIG. 46 shows the configuration of an exposure tool connected to an EUV light generation system. [Figure 47] Figure 47 shows the configuration of the inspection device connected to the EUV light generation system. Embodiment

[0009] <Contents> 1. Comparative Example 1.1.EUV Light Generation System11 1.1.1 Configuration 1.1.2 Operation 1.2. Target Generator 26 1.2.1 Configuration 1.2.2 Operation 1.3.Target Sensor 4 1.3.1 Configuration 1.3.2 Operation 1.4.Piezo Unit 80 1.4.1 Configuration 1.4.2 Operation 1.5 Handling when Piezo Unit 80 is malfunctioning 1.6 Issues in the comparative example 2. Piezo unit 80a including multiple piezo elements arranged in the X direction 2.1 Configuration 2.2 Handling abnormalities in the piezo unit 80a 2.3 Example of Switching Circuit 59 2.3.1 First example of operation 2.3.2 Second example 2.4 First variant 2.5 Second Variant 2.5.1 Configuration 2.5.2 First Example of Switching Circuit 59 2.5.3 Second Example of Switching Circuit 59 2.6 Third Variant 2.7 Fourth Variant 2.8 Effect 3. Piezo unit 80a attached to the bottom surface of nozzle 62 3.1 Fifth Variant 3.2 Sixth Variant 3.3 Seventh Variant 3.4 Effect 4.Other 4.1 Example of EUV light utilization equipment6 4.2 Processor 4.3 Supplementary Information

[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. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0011] 1. Comparative Example 1.1.EUV Light Generation System11 1.1.1 Configuration FIG. 1 shows the configuration of an LPP-type EUV light generation system 11 as a comparative example. The comparative example in the present disclosure refers to a configuration that the applicant is aware of as being known only by the applicant, and is not a publicly known example that the applicant acknowledges. The EUV light generation apparatus 1 is used together with a laser apparatus 3. In the present disclosure, a system including the EUV light generation apparatus 1 and the laser apparatus 3 is referred to as the EUV light generation system 11. The EUV light generation apparatus 1 includes a chamber 2 and a target generation apparatus 26. The chamber 2 is a sealable container. The target generation apparatus 26 supplies a target 27 containing a target material into the chamber 2. The target material may include tin, terbium, gadolinium, lithium, xenon, or a combination of two or more of these.

[0012] A through-hole is provided in the wall of the chamber 2. The through-hole is closed by a window 21, through which laser light 32 output from the laser device 3 passes. An EUV collector mirror 23 having a reflective surface with an ellipsoidal shape is disposed inside the chamber 2. The EUV collector mirror 23 has first and second focal points. A multilayer reflective film in which molybdenum and silicon are alternately stacked is formed on the surface of the EUV collector mirror 23. The EUV collector mirror 23 is disposed so that its first focal point is located in the plasma generation region 25 and its second focal point is located at an intermediate focal point 292. A through-hole 24 is provided in the center of the EUV collector mirror 23, through which laser light 33 passes.

[0013] The EUV light generation device 1 includes an EUV light generation processor 5, a target sensor 4, etc. The configuration of the EUV light generation processor 5 will be described later. The target sensor 4 detects at least one of the presence, trajectory, position, and speed of a target 27. The target sensor 4 may also have an imaging function.

[0014] The EUV light generation system 1 also includes a connection part 29 that connects the interior of the chamber 2 with the interior of the EUV light utilization system 6. The EUV light utilization system 6 may be an exposure system 6a shown in FIG. 46 or an inspection system 6b shown in FIG. 47. A wall 291 having an aperture formed therein is provided inside the connection part 29. The wall 291 is positioned so that the aperture is located at the second focal point of the EUV collector mirror 23.

[0015] Furthermore, the EUV light generation system 1 includes a laser beam transmission device 34, a laser beam focusing mirror 22, and a target recovery unit 28 for recovering the target 27. The laser beam transmission device 34 includes an optical element for defining the transmission state of the laser beam 32, and an actuator for adjusting the position, attitude, etc. of the optical element.

[0016] 1.1.2 Operation The operation of the EUV light generation system 11 will be described with reference to Figure 1. Pulsed laser light 31 output from the laser device 3 passes through a laser light transmission device 34, passes through a window 21 as laser light 32, and enters the chamber 2. The laser light 32 travels through the chamber 2 along the laser light path, is reflected by the laser light focusing mirror 22, and is irradiated onto the target 27 as laser light 33.

[0017] The target generation device 26 outputs a target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 is irradiated with a laser beam 33. The target 27 irradiated with the laser beam 33 is converted into plasma, and the plasma emits radiation 251. The EUV light contained in the radiation 251 is reflected by the EUV collector mirror 23 with a higher reflectance than light in other wavelength ranges. Reflected light 252 containing EUV light reflected by the EUV collector mirror 23 is collected at an intermediate focus 292 and output to the EUV light utilization device 6. One target 27 may be irradiated with multiple pulses contained in the laser beam 33.

[0018] The EUV light generation processor 5 controls the entire EUV light generation system 11. The EUV light generation processor 5 processes the detection results of the target sensor 4. Based on the detection results of the target sensor 4, the EUV light generation processor 5 controls the timing and direction of output of the target 27. Furthermore, the EUV light generation processor 5 controls the oscillation timing of the laser device 3, the traveling direction of the laser beam 32, the focusing position of the laser beam 33, etc. The various controls described above are merely examples, and other controls may be added as necessary.

[0019] 1.2. Target Generator 26 1.2.1 Configuration 2 is a partial cross-sectional view showing the configuration of a target generation device 26 in a comparative example. The target generation device 26 includes a pressure regulator 12, an inert gas cylinder 13, a target generation processor 51, heater power supplies 53 and 55, a piezoelectric element power supply 58, a reservoir tank 61, and a nozzle 62. The nozzle 62 includes a nozzle hole 62a. The configuration of the target generation processor 51 will be described later.

[0020] The output direction of the target 27 is defined as the Y direction. A line passing through the center of the nozzle hole 62a in the Y direction is defined as the central axis of the nozzle 62, and the direction perpendicular to this central axis toward the piezo unit 80 is defined as the X direction. The direction perpendicular to both the X and Y directions is defined as the Z direction.

[0021] The reservoir tank 61 stores a target material containing, for example, tin in a molten state. A heater 63 is attached to the reservoir tank 61 in order to melt the target material and maintain the molten state. The heater 63 is connected to the heater power supply 53. A temperature sensor 64 is also attached to the reservoir tank 61.

[0022] A nozzle 62 is connected to the lower end of a reservoir tank 61, and a nozzle hole 62a is located at the lowest end of the nozzle 62. The liquid target material stored in the reservoir tank 61 passes through the inside of the nozzle 62 toward the nozzle hole 62a. A heater 65 is also attached to the nozzle 62 to maintain the target material in a molten state inside the nozzle 62. A heater power supply 55 is connected to the heater 65. A temperature sensor 66 is also attached to the nozzle 62.

[0023] A piezoelectric unit 80 is further attached to the nozzle 62. The piezoelectric unit 80 may include a piezoelectric crystal such as PZT (lead zirconate titanate) and electrodes attached to the piezoelectric crystal. The piezoelectric crystal and electrodes will be described later with reference to FIGS. 3 and 5. A piezoelectric element power supply 58 is connected to the piezoelectric unit 80. The piezoelectric element power supply 58 applies a drive voltage to the piezoelectric crystal included in the piezoelectric unit 80, causing the nozzle 62 to vibrate.

[0024] The inert gas cylinder 13 is connected to the pressure regulator 12 by a gas pipe. The pressure regulator 12 is in communication with the inside of the reservoir tank 61 by another gas pipe. The inert gas is supplied from the inert gas cylinder 13 to the inside of the reservoir tank 61 via these gas pipes.

[0025] 1.2.2 Operation The target generation processor 51 controls the value of the current that the heater power supply 53 supplies to the heater 63 so that the detection value detected by the temperature sensor 64 maintains the target temperature. The target generation processor 51 controls the value of the current that the heater power supply 55 supplies to the heater 65 so that the detection value detected by the temperature sensor 66 maintains the target temperature.

[0026] The pressure regulator 12 adjusts the pressure of the inert gas supplied from the inert gas cylinder 13 into the reservoir tank 61 in response to a control signal output from the target generation processor 51. The inert gas introduced into the reservoir tank 61 pressurizes the molten target material in the reservoir tank 61. As the inert gas pressurizes the target material, a jet 67 of liquid target material is ejected from the nozzle hole 62a of the nozzle 62.

[0027] Piezoelectric element power supply 58 applies a drive voltage having a waveform corresponding to a control signal output from target generation processor 51 to a piezoelectric crystal included in piezo unit 80. This causes the piezoelectric crystal to expand and contract periodically, vibrating nozzle 62. When the vibrations applied to nozzle 62 satisfy predetermined conditions, standing waves are generated in jet 67 of target material discharged from nozzle hole 62a. Due to the surface tension of the target material, jet 67 is separated into droplets, and multiple targets 27 are generated.

[0028] The target 27 output into the chamber 2 is supplied to the plasma generation region 25 in the chamber 2. The EUV light generation processor 5 controls the laser device 3 so that the target 27 output from the target generation device 26 is irradiated with laser light 33.

[0029] 1.3.Target Sensor 4 1.3.1 Configuration The target sensor 4 is used together with the light-emitting unit 7. The target sensor 4 and the light-emitting unit 7 are arranged on opposite sides of the trajectory of the target 27 discharged along the central axis of the nozzle 62. The target sensor 4 includes an optical sensor 41 and a light-receiving optical system 42. The light-emitting unit 7 includes a light source 71 and an illumination optical system 72.

[0030] 1.3.2 Operation The light source 71 continuously emits light in response to a control signal output from the EUV light generation processor 5. The illumination optical system 72 focuses the light output from the light source 71 on an area 35 that includes a predetermined position on the trajectory of the target 27 and positions surrounding the predetermined position. The light receiving optical system 42 guides the light output from the light emitting unit 7 to the light receiving surface of the optical sensor 41.

[0031] When the target 27 passes through the area 35 illuminated by the light-emitting unit 7, part of the light output from the light-emitting unit 7 is blocked by the target 27 before the light reaches the target sensor 4. This can reduce the amount of light incident on the optical sensor 41. The optical sensor 41 detects a change in the amount of incident light and outputs a target detection signal to the EUV light generation processor 5.

[0032] 1.4.Piezo Unit 80 1.4.1 Configuration 3 to 5 show the configuration of a piezo unit 80 in a comparative example. Fig. 3 shows the piezo unit 80 viewed from the -Z direction, Fig. 4 shows the piezo unit 80 viewed from the -X direction, and Fig. 5 shows the piezo unit 80 viewed from the -Y direction.

[0033] The piezo unit 80 attached to the side of the nozzle 62 is composed of a cooling member 84, a piezo element, an insulating member 83, and a pressing member 81 arranged in this order in the X direction from the side closest to the nozzle 62. The piezo element is composed of a piezoelectric crystal P1 and electrodes E1 and E2. Each of a plurality of bolts 82 passes through the pressing member 81 and the cooling member 84 and is fixed to the nozzle 62. The electrodes E1 and E2, the pressing member 81, the bolt 82, and the cooling member 84 are made of metal. There is a gap between the bolt 82 and the electrode E2 so that they are not electrically connected. The X direction is an example of a first direction in this disclosure.

[0034] The electrodes E1 and E2 are respectively connected to first and second output terminals O1 and O2 of a piezoelectric element power supply 58. The piezoelectric element power supply 58 generates a voltage between the first and second output terminals O1 and O2. The potential of the first output terminal O1 is, for example, a ground potential GND, and the potential of the second output terminal O2 is, for example, a pulse-like potential +V.

[0035] The cooling member 84 includes a flow path 84a for the cooling medium, and the flow path 84a is connected to a chiller 84b by a pipe. The chiller 84b includes a pump and a heat exchanger (not shown).

[0036] 1.4.2 Operation The piezoelectric crystal P1 expands and contracts in the X direction in response to an electric field generated inside the piezoelectric crystal P1 by a voltage applied between electrodes E1 and E2. Since the piezoelectric crystal P1 is pressed in the -X direction by the pressing member 81, the expansion and contraction of the piezoelectric crystal P1 vibrates the nozzle 62.

[0037] The nozzle 62 is connected to the ground potential GND, just like the electrode E1. There is no need for insulation between the nozzle 62 and the electrode E1. The pressing member 81 is also connected to the ground potential GND via the bolt 82 and the nozzle 62. An insulating member 83 ensures insulation between the pressing member 81 and the electrode E2.

[0038] Nozzle 62 has a temperature equal to or higher than the melting point of tin, and this temperature may exceed the upper limit of the operating temperature range of piezoelectric crystal P1, but by providing cooling member 84 between nozzle 62 and piezoelectric crystal P1, the temperature of piezoelectric crystal P1 is kept below the upper limit of the operating temperature range. A temperature sensor (not shown) may be provided in cooling member 84, and target generation processor 51 may control chiller 84b in accordance with the detection result of the temperature sensor.

[0039] 1.5 Handling when Piezo Unit 80 is malfunctioning FIG. 6 is a flowchart showing the operation of the EUV light generation processor 5, including the processing to be performed when an abnormality occurs in the piezo unit 80, in a comparative example.

[0040] In ST10, the EUV light generation processor 5 performs a startup operation of the EUV light generation system 11. The startup operation of the EUV light generation system 11 includes the following processes A to C.

[0041] Processing A: Buffer gas supply to chamber 2 The EUV light generation processor 5 controls an exhaust pump, a buffer gas supply device, a gas pressure sensor, etc. (not shown) to evacuate the chamber 2, and then supplies buffer gas to the chamber 2 to maintain a predetermined pressure.

[0042] Process B: Activation of target generator 26 The EUV light generation processor 5 sends a command signal to the target generation processor 51 to activate the target generation device 26. The target generation processor 51 heats and melts the target material inside the reservoir tank 61 and the nozzle 62, and controls the heater power supplies 53 and 55 to maintain a predetermined temperature. The target generation processor 51 controls the pressure regulator 12 to adjust the pressure inside the reservoir tank 61, and controls the piezoelectric element power supply 58 to cause the piezo unit 80 to vibrate the nozzle 62.

[0043] Processing C Other The EUV light generation processor 5 activates the target sensor 4 and the light emitter 7 and begins detecting the target 27. The detection result of the target 27 is sent from the EUV light generation processor 5 to the target generation processor 51. The EUV light generation processor 5 activates a plasma generation region imaging device (not shown), the laser device 3, and the laser light transmission device 34, and performs other startup operations for EUV light generation.

[0044] In ST11, the EUV light generation processor 5 sends a command signal to the target generation processor 51 to search for and determine the optimal duty. Searching for the optimal duty involves acquiring detection results of the targets 27 ejected from the nozzle 62 while changing the duty ratio, which is the ratio of the on time in the waveform of the voltage applied to the piezoelectric element, and searching for an appropriate value for the duty ratio. The duty ratio is changed, for example, from 1% to 99% in increments of 0.1%. The detection results of the targets 27 include determining whether the diameter of the targets 27 and the spacing between two targets 27 are within their respective normal value ranges. The target generation processor 51 determines, as the optimal duty, the center value of the widest range of continuous duty ratio values ​​within which the incidence rate of abnormal values ​​in the detection results of the targets 27 is less than a threshold.

[0045] It may be possible that the optimum duty cannot be found by searching for the duty ratio alone. In such cases, the temperature of the nozzle 62 measured by the temperature sensor 66 may be changed and the duty ratio may be searched for again. If the optimum duty cannot be found even after changing the temperature of the nozzle 62 multiple times, the on-voltage in the waveform of the voltage applied to the piezoelectric element may be changed and the duty ratio may be searched for again.

[0046] In ST12, the EUV light generation processor 5 starts EUV light generation control so that the EUV light generation system 11 starts generating EUV light. The target generation processor 51 monitors the rate of occurrence of abnormal values ​​in the detection results of the target 27, and controls the duty ratio based on the optimal duty so that the rate of occurrence of abnormal values ​​is optimized.

[0047] In ST13, the EUV light generation processor 5 sends a command signal to the target generation processor 51 to determine whether the piezoelectric element is operating normally. The target generation processor 51 determines whether the piezoelectric element is operating normally based on the detection result of the target 27 by the target sensor 4. For example, if the abnormal value occurrence rate is below a threshold, the piezoelectric element is determined to be operating normally. However, if the abnormal value occurrence rate exceeds the threshold even after controlling the duty ratio to optimize the abnormal value occurrence rate, the piezoelectric element is determined to be malfunctioning. If the piezoelectric element is operating normally (ST13: YES), the EUV light generation processor 5 proceeds to ST14. If the piezoelectric element is not operating normally (ST13: NO), the EUV light generation processor 5 proceeds to ST24.

[0048] In ST14, the EUV light generation processor 5 determines whether to stop the generation of EUV light. If the generation of EUV light is to be stopped (ST14: YES), the EUV light generation processor 5 proceeds to ST15. If the generation of EUV light is not to be stopped (ST14: NO), the EUV light generation processor 5 returns to ST13.

[0049] In ST15, the EUV light generation processor 5 performs processing to shut down the EUV light generation system 11 that was started in ST10. After ST15, the EUV light generation processor 5 ends the processing of this flowchart.

[0050] In ST24, the EUV light generation processor 5 also performs processing to shut down the EUV light generation system 11. After ST24, the operator of the EUV light generation system 11 replaces the piezo unit 80. Replacing the piezo unit 80 may also involve replacing the target generation device 26. After replacing the piezo unit 80, the EUV light generation processor 5 returns processing to ST10.

[0051] 1.6 Issues in the comparative example As described with reference to FIG. 6 , if the piezoelectric element included in the piezo unit 80 is not operating normally, the piezo unit 80 needs to be replaced. Because the nozzle 62 to which the piezo unit 80 is attached is located inside the chamber 2, replacing the piezo unit 80 requires at least opening the chamber 2. After replacing the piezo unit 80, the EUV light generation system 11 must be restarted by returning to the ST 10. This results in downtime during which EUV light cannot be generated. Furthermore, because the reservoir tank 61 and the nozzle 62 are hot immediately after shutting down the EUV light generation system 11, it may be impractical to remove and replace only the piezo unit 80 from the nozzle 62. In this case, even if the abnormality is limited to the piezo element, it would be costly to replace the entire target generation device 26.

[0052] It is also conceivable to mount a spare piezo unit in addition to the piezo unit 80 on the nozzle 62. However, because the volume occupied by the piezo unit is large, the number of piezo units that can be mounted on the nozzle 62 is limited to two at most.

[0053] Furthermore, even if a spare piezo unit is used, the search for the optimum duty in ST11 must be restarted, which still results in downtime.

[0054] 2. Piezo unit 80a including multiple piezo elements arranged in the X direction 2.1 Configuration 7 to 9 show the configuration of piezo unit 80a in the first embodiment. Piezo unit 80a attached to the side surface of nozzle 62 is composed of first, second, and fifth piezo elements, an insulating member 83, and a pressing member 81 arranged in this order in the X direction from the side closest to nozzle 62. The third and fourth piezo elements will be described in the second modified example.

[0055] The first piezoelectric element includes an electrode E1, a piezoelectric crystal P1, and an electrode E2. The second piezoelectric element includes an electrode E2, a piezoelectric crystal P2, and an electrode E3. The fifth piezoelectric element includes an electrode E3, a piezoelectric crystal P5, and an electrode E7. In this manner, the first piezoelectric element is disposed in a position in the X direction relative to the nozzle 62, the second piezoelectric element is disposed in a position in the X direction relative to the first piezoelectric element, the fifth piezoelectric element is disposed in a position in the X direction relative to the second piezoelectric element, and a pressing member 81 is disposed in a position in the X direction relative to the fifth piezoelectric element. However, the first and second piezoelectric elements share electrode E2, and the second and fifth piezoelectric elements share electrode E3. An insulating member 83 is disposed between the pressing member 81 and electrode E7. Each of a plurality of bolts 82 penetrates the pressing member 81 and is fixed to the nozzle 62. Electrodes E1, E2, and E3 correspond to the first, second, and third electrodes in this disclosure, respectively.

[0056] The electrodes E1 to E3 and E7 are each connected by an electric wire to a switching circuit 59. The switching circuit 59 is connected to first and second output terminals O1 and O2 of a piezoelectric element power supply 58. The switching circuit 59 switches the connections between the first and second output terminals O1 and O2 and the electrodes E1 to E3 and E7 to one of the following states a to c. State a: The first output terminal O1 is connected to the electrode E1, and the second output terminal O2 is connected to the electrode E2. State b: The first output terminal O1 is connected to the electrode E2, and the second output terminal O2 is connected to the electrode E3. State c: The first output terminal O1 is connected to the electrode E3, and the second output terminal O2 is connected to the electrode E7.

[0057] State a corresponds to the first state in this disclosure, and state b corresponds to the second state in this disclosure. In state a, a voltage is applied to the first piezoelectric element by the piezoelectric element power supply 58, in state b, a voltage is applied to the second piezoelectric element, and in state c, a voltage is applied to the fifth piezoelectric element. The first, second, and fifth piezoelectric elements have the same main vibration direction, and when a voltage is applied to each of them, they expand and contract in the X direction, thereby vibrating the nozzle 62.

[0058] Although the case where the piezo unit 80a includes three piezo elements has been described here, the number of piezo elements may be two or four or more. Furthermore, the conductive member of the nozzle 62 may also serve as the electrode E1, so that the piezoelectric crystal P1 comes into direct contact with the nozzle 62.

[0059] 2.2 Handling abnormalities in the piezo unit 80a FIG. 10 is a flowchart showing the operation of the EUV light generation processor 5, including the processing to be performed when an abnormality occurs in the piezo unit 80a, in the first embodiment.

[0060] The processes in ST10 to ST15 are the same as those in the comparative example. In the first embodiment, if the piezoelectric element is not operating normally in ST13 (ST13: NO), the EUV light generation processor 5 proceeds to ST20.

[0061] In ST20, the EUV light generation processor 5 determines whether the piezo unit 80a has a normal piezo element. The EUV light generation processor 5 may store whether the piezo element is normal or abnormal in a memory (not shown) and determine whether it is normal or abnormal based on the memory storage. If a normal piezo element is present (ST20: YES), the EUV light generation processor 5 proceeds to ST21. If a normal piezo element is not present (ST20: NO), the EUV light generation processor 5 proceeds to ST24. ST24 and the subsequent processing are the same as in the comparative example.

[0062] In ST21, the EUV light generation processor 5 sends a piezoelectric element switching signal to the target generation processor 51, and the target generation processor 51 switches the piezoelectric element. The piezoelectric element is switched, for example, from state a to state b, or from state b to state c.

[0063] In ST22, the EUV light generation processor 5 sends a command signal to the target generation processor 51 to determine whether the target 27 is normal. The target generation processor 51 determines whether the target 27 is generated normally based on the detection result of the target 27 by the target sensor 4. For example, if the abnormal value occurrence rate is equal to or lower than a threshold, the target 27 is determined to be generated normally. If the abnormal value occurrence rate exceeds the threshold, the target 27 is determined to be generated abnormally. If the target 27 is generated normally (ST22: YES), the EUV light generation processor 5 returns to ST13 to continue the EUV light generation process by the EUV light generation system 11. If the target 27 is not generated normally (ST22: NO), the EUV light generation processor 5 proceeds to ST23.

[0064] In ST23, the EUV light generation processor 5 suspends the EUV light generation control started in ST12 and returns to ST11. If the answer to ST22 is NO due to switching the piezo element, a search for the optimal duty again (ST11) is required, but stopping (ST24) and restarting (ST10) the EUV light generation system 11 can be avoided. Also, if the answer to ST22 is YES, a search for the optimal duty again can be avoided.

[0065] 2.3 Example of Switching Circuit 59 Figures 11 to 16 show examples of the switching circuit 59 in the first embodiment. Figures 11 to 16 all show the same circuit, and Figures 11 to 13 show a first operation example, and Figures 14 to 16 show a second operation example.

[0066] The switching circuit 59 includes two input terminals connected to the first and second output terminals O1 and O2, respectively, and four output terminals connected to the electrodes E1 to E3 and E7, respectively. The first output terminal O1 is short-circuited to the electrode E1. The electrodes E1 and E2 are connected via a switch S1. The electrodes E2 and E3 are connected via a switch S2. The second output terminal O2 is connected to the electrodes E2, E3, and E7 via switches S3, S4, and S5, respectively.

[0067] 2.3.1 First example of operation As shown in FIG. 11, when switch S3 is turned on and switches S1, S2, S4, and S5 are turned off, state a is reached in which the first output terminal O1 is connected to electrode E1 and the second output terminal O2 is connected to electrode E2.

[0068] As shown in FIG. 12, when switches S1 and S4 are turned on and switches S2, S3, and S5 are turned off, state b is reached in which the first output terminal O1 is connected to electrode E2 and the second output terminal O2 is connected to electrode E3.

[0069] As shown in FIG. 13, when switches S1, S2, and S5 are turned on and switches S3 and S4 are turned off, state c is reached in which the first output terminal O1 is connected to electrode E3 and the second output terminal O2 is connected to electrode E7.

[0070] By such an operation, one of the first, second and fifth piezoelectric elements can be used, and if it stops working properly, another one can be used.

[0071] Because the first, second, and fifth piezoelectric elements do not necessarily have exactly the same characteristics, it is possible that target 27 will not be generated correctly in ST22 of Figure 10, and that a search for the optimal duty will be required again. However, because there are common conditions between the first, second, and fifth piezoelectric elements, such as the pressing force of pressing member 81 due to the tightening of bolt 82, or the mounting position of piezo unit 80a, it is highly likely that a search for the optimal duty will not be necessary compared to switching to a different piezo unit. As a result, downtime can be reduced.

[0072] As described above, the pressing member 81 is connected to ground potential GND via the bolt 82 and the nozzle 62. Meanwhile, in FIG. 11, electrode E2 is connected to potential +V. The potential difference +V between electrode E2 and pressing member 81 generates an electric field inside the piezoelectric crystals P2 and P5 that is opposite to the electric field inside the piezoelectric crystal P1. This electric field may cause the piezoelectric crystals P2 and P5 to expand and contract. Increasing the thickness of the insulating member 83 can reduce the electric field inside the piezoelectric crystals P2 and P5 and reduce the expansion and contraction of the piezoelectric crystals P2 and P5, but it does not reduce the electric field to zero. Therefore, the expansion and contraction of the piezoelectric crystals P2 and P5 may weaken the vibration applied to the nozzle 62 by the expansion and contraction of the piezoelectric crystal P1. In FIG. 12, the potential difference +V between electrode E3 and pressing member 81 generates an electric field inside the piezoelectric crystal P5, which may cause the piezoelectric crystal P5 to expand and contract, weakening the vibration applied to the nozzle 62. The second operation example described below can solve this problem.

[0073] 2.3.2 Second example 14, when switches S3, S4, and S5 are turned on and switches S1 and S2 are turned off, a state a is reached in which the first output terminal O1 is connected to electrode E1 and the second output terminal O2 is connected to electrode E2. Furthermore, the second output terminal O2 is also connected to electrodes E3 and E7. This results in both ends of piezoelectric crystal P2 being connected to potential +V, and both ends of piezoelectric crystal P5 being connected to potential +V, thereby suppressing expansion and contraction of piezoelectric crystals P2 and P5.

[0074] 15, when switches S1, S4, and S5 are turned on and switches S2 and S3 are turned off, a state b is reached in which the first output terminal O1 is connected to electrode E2 and the second output terminal O2 is connected to electrode E3. Furthermore, the second output terminal O2 is also connected to electrode E7. This connects both ends of the piezoelectric crystal P5 to potential +V, thereby suppressing expansion and contraction of the piezoelectric crystal P5.

[0075] FIG. 16 is similar to FIG. 13, and shows a state c in which the first output terminal O1 is connected to the electrode E3 and the second output terminal O2 is connected to the electrode E7.

[0076] This operation can suppress expansion and contraction of the other piezoelectric elements when any one of the first, second, and fifth piezoelectric elements is used, so the conditions for use of the first, second, and fifth piezoelectric elements are the same. Therefore, there is a higher possibility that re-searching for the optimal duty is not necessary than in the first operation example. As a result, downtime can be reduced.

[0077] 12 and 15, in state b where the first output terminal O1 is connected to electrode E2 and the second output terminal O2 is connected to electrode E3, the first output terminal O1 is also connected to electrode E1. This connects both ends of the piezoelectric crystal P1 to ground potential GND, thereby suppressing expansion and contraction of the piezoelectric crystal P1. Also, in state c where the first output terminal O1 is connected to electrode E3 and the second output terminal O2 is connected to electrode E7, the first output terminal O1 is also connected to electrodes E1 and E2. This connects both ends of the piezoelectric crystal P1 to ground potential GND, while the second output terminal O2 is connected to electrode E7, thereby suppressing expansion and contraction of the piezoelectric crystals P1 and P2.

[0078] In other respects, the first embodiment is similar to the comparative example.

[0079] 2.4 First variant 17 to 19 show the configuration of a piezo unit 80b in a first modified example. In FIG. 17, the piezo element power supply 58 and the switching circuit 59 are not shown. The piezo unit 80b differs from the first embodiment in that a cooling member 84 is disposed between the first piezo element and the nozzle 62. The cooling member 84 is the same as in the comparative example. This makes it possible to suppress heating of the three piezoelectric crystals P1, P2, and P5 by using a single cooling member 84. The cooling member 84 may also serve as the electrode E1.

[0080] In other respects, the first modified example is similar to the first embodiment.

[0081] 2.5 Second Variant 2.5.1 Configuration 20 and 21 show the configuration of piezo units 80a and 85a in the second modified example. FIG. 20 shows the piezo units 80a and 85a viewed from the -Z direction, and FIG. 21 shows them viewed from the -Y direction. The piezo unit 80a is the same as in the first embodiment. The piezo unit 85a is composed of third, fourth, and sixth piezo elements, an insulating member 88, and a pressing member 86, arranged in this order from the side closest to the nozzle 62 in the -X direction. The nozzle 62 is located between the first, second, and fifth piezo elements and the third, fourth, and sixth piezo elements.

[0082] The third piezoelectric element includes electrode E4, piezoelectric crystal P3, and electrode E5. The fourth piezoelectric element includes electrode E5, piezoelectric crystal P4, and electrode E6. The sixth piezoelectric element includes electrode E6, piezoelectric crystal P6, and electrode E8. In this manner, the third piezoelectric element is disposed in the -X direction relative to the nozzle 62, the fourth piezoelectric element is disposed in the -X direction relative to the third piezoelectric element, the sixth piezoelectric element is disposed in the -X direction relative to the fourth piezoelectric element, and the pressing member 86 is disposed in the -X direction relative to the sixth piezoelectric element. However, the third and fourth piezoelectric elements share electrode E5, and the fourth and sixth piezoelectric elements share electrode E6. An insulating member 88 is disposed between the pressing member 86 and electrode E8. Each of a plurality of bolts 87 penetrates the pressing member 86 and is fixed to the nozzle 62. Electrodes E4, E5, and E6 correspond to the fourth, fifth, and sixth electrodes, respectively, in this disclosure. The -X direction is an example of the second direction in this disclosure.

[0083] The electrodes E4 to E6 and E8 are each connected by an electric wire to a switching circuit 59. The switching circuit 59 switches the connections between the first and second output terminals O1 and O2 and the electrodes E1 to E8 to one of the above-mentioned states a to c and the following states d to f. State d: The first output terminal O1 is connected to the electrode E4, and the second output terminal O2 is connected to the electrode E5. State e: The first output terminal O1 is connected to the electrode E5, and the second output terminal O2 is connected to the electrode E6. State f: The first output terminal O1 is connected to the electrode E6, and the second output terminal O2 is connected to the electrode E8.

[0084] State d corresponds to the third state in this disclosure, and state e corresponds to the fourth state in this disclosure. By the piezoelectric element power supply 58, a voltage is applied to the third piezoelectric element in state d, a voltage is applied to the fourth piezoelectric element in state e, and a voltage is applied to the sixth piezoelectric element in state f. The third, fourth, and sixth piezoelectric elements have the same main vibration direction, and when a voltage is applied to each of them, they expand and contract in the X direction, thereby vibrating the nozzle 62.

[0085] Although the case where piezo unit 85a includes three piezo elements has been described here, the number of piezo elements may be two or four or more. Furthermore, the conductive member of nozzle 62 may also serve as electrode E4, so that piezoelectric crystal P3 is in direct contact with nozzle 62. Although the case where two piezo units 80a and 85a are arranged in one nozzle 62 has been described, three or more piezo units may be arranged if there is sufficient installation space. It is desirable that the multiple piezo units be arranged rotationally symmetrically with respect to the central axis of nozzle 62.

[0086] 2.5.2 First Example of Switching Circuit 59 22 to 27 show a first example of the switching circuit 59 in the second modified example. All of the circuits in FIGS. 22 to 27 are the same.

[0087] The switching circuit 59 includes two input terminals connected to the first and second output terminals O1 and O2, respectively, and eight output terminals connected to the electrodes E1 to E8, respectively. The first output terminal O1 is short-circuited to the electrodes E1 and E4. The electrodes E1 and E2 are connected via a switch S1a. The electrodes E2 and E3 are connected via a switch S2a. The electrodes E4 and E5 are connected via a switch S1b. The electrodes E5 and E6 are connected via a switch S2b. The second output terminal O2 is connected to a selector switch S6. The selector switch S6 switches and connects the second output terminal O2 to the first and second nodes N1 and N2. The first node N1 is connected to the electrodes E2, E3, and E7 via switches S3a, S4a, and S5a, respectively. The second node N2 is connected to the electrodes E5, E6, and E8 via switches S3b, S4b, and S5b, respectively. The switches S1a to S5a form a first switching section C1, and the switches S1b to S5b form a second switching section C2.

[0088] 22, when switches S3a, S4a, and S5a are turned on and switches S1a and S2a are turned off in the first switching unit C1, a first connection state is established in which the first output terminal O1 is connected to electrode E1 and the first node N1 is connected to electrode E2. With the second output terminal O2 connected to the first node N1 by the switching switch S6, setting the first switching unit C1 to the first connection state establishes state a, and a voltage is applied to the piezoelectric crystal P1.

[0089] 23, when switches S1a, S4a, and S5a are turned on and switches S2a and S3a are turned off in the first switching unit C1, a second connection state is established in which the first output terminal O1 is connected to electrode E2 and the first node N1 is connected to electrode E3. With the second output terminal O2 connected to the first node N1 by the switching switch S6, the first switching unit C1 is set to the second connection state, resulting in state b, in which a voltage is applied to the piezoelectric crystal P2.

[0090] 24, when switches S1a, S2a, and S5a are turned on and switches S3a and S4a are turned off in first switching section C1, first output terminal O1 is connected to electrode E3 and first node N1 is connected to electrode E7. When second output terminal O2 is connected to first node N1 by switch S6, state c is reached and voltage is applied to piezoelectric crystal P5.

[0091] 25, when switches S3b, S4b, and S5b are turned on and switches S1b and S2b are turned off in the second switching unit C2, a third connection state is established in which the first output terminal O1 is connected to electrode E4 and the second node N2 is connected to electrode E5. With the second output terminal O2 connected to the second node N2 by the switching switch S6, setting the second switching unit C2 to the third connection state establishes state d, and a voltage is applied to the piezoelectric crystal P3.

[0092] 26, when switches S1b, S4b, and S5b are turned on and switches S2b and S3b are turned off in the second switching unit C2, a fourth connection state is established in which the first output terminal O1 is connected to electrode E5 and the second node N2 is connected to electrode E6. With the second output terminal O2 connected to the second node N2 by the switching switch S6, setting the second switching unit C2 to the fourth connection state establishes state e, and a voltage is applied to the piezoelectric crystal P4.

[0093] 27, when switches S1b, S2b, and S5b are turned on and switches S3b and S4b are turned off in second switching section C2, first output terminal O1 is connected to electrode E6 and second node N2 is connected to electrode E8. When second output terminal O2 is connected to second node N2 by switch S6, state f is reached and voltage is applied to piezoelectric crystal P6.

[0094] Here, the first and second switching units C1 and C2 each operate as in the second operation example (see FIGS. 14 to 16), so that no voltage is applied to the piezoelectric crystals other than the selected one. The present disclosure is not limited to this, and the first and second switching units C1 and C2 each may operate as in the first operation example (see FIGS. 11 to 13).

[0095] 2.5.3 Second Example of Switching Circuit 59 28 to 33 show a second example of the switching circuit 59 in the second modified example. All of the circuits in FIGS. 28 to 33 are the same.

[0096] The switching circuit 59 includes two input terminals connected to the first and second output terminals O1 and O2, respectively, and eight output terminals connected to the electrodes E1 to E8, respectively. The first output terminal O1 is short-circuited to the electrodes E1 and E4 via the third node N3. The third node N3 and the fourth node N4 are connected via a switch S1. The fourth node N4 and the fifth node N5 are connected via a switch S2. The second output terminal O2 and the fourth, fifth, and sixth nodes N4, N5, and N6 are connected via switches S3, S4, and S5, respectively. The fourth, fifth, and sixth nodes N4, N5, and N6 are connected to changeover switches S61, S62, and S63, respectively. The changeover switch S61 switches between connecting the fourth node N4 to the electrodes E2 and E5. The changeover switch S62 switches between connecting the fifth node N5 to the electrodes E3 and E6. The changeover switch S63 switches and connects the sixth node N6 to the electrodes E7 and E8. The switches S1 to S5 form a third changeover section C3, and the changeover switches S61 to S63 form a fourth changeover section C4.

[0097] 28 and 31, when the switches S3, S4, and S5 in the third switching unit C3 are turned on and the switches S1 and S2 are turned off, the first output terminal O1 is connected to the third node N3 and the second output terminal O2 is connected to the fourth node N4, which is called a fifth connection state.

[0098] 29 and 32, when the switches S1, S4, and S5 in the third switching unit C3 are turned on and the switches S2 and S3 are turned off, the first output terminal O1 is connected to the fourth node N4 and the second output terminal O2 is connected to the fifth node N5, which is called a sixth connection state.

[0099] 30 and 33, when the switches S1, S2, and S5 in the third switching unit C3 are turned on and the switches S3 and S4 are turned off, the first output terminal O1 is connected to the fifth node N5 and the second output terminal O2 is connected to the sixth node N6, which is called a ninth connection state.

[0100] 28 to 30, the fourth switching unit C4 can connect the fourth, fifth, and sixth nodes N4, N5, and N6 to the electrodes E2, E3, and E7 by the changeover switches S61, S62, and S63, respectively. This is called a seventh connection state.

[0101] 31 to 33, the fourth switching unit C4 can connect the fourth, fifth, and sixth nodes N4, N5, and N6 to the electrodes E5, E6, and E8 via the changeover switches S61, S62, and S63, respectively. This is called an eighth connection state.

[0102] FIG. 28 shows a combination of the fifth and seventh connection states, which results in state a, and a voltage is applied to the piezoelectric crystal P1.

[0103] FIG. 29 shows a combination of the sixth and seventh connection states, which results in state b, and a voltage is applied to the piezoelectric crystal P2.

[0104] FIG. 30 shows a combination of the ninth connection state and the seventh connection state, which results in state c, and voltage is applied to the piezoelectric crystal P5.

[0105] FIG. 31 shows a combination of the fifth and eighth connection states, which results in state d, and voltage is applied to the piezoelectric crystal P3.

[0106] FIG. 32 shows a combination of the sixth and eighth connection states, which results in state e, and voltage is applied to the piezoelectric crystal P4.

[0107] FIG. 33 shows a combination of the ninth connection state and the eighth connection state, which results in state f, and a voltage is applied to the piezoelectric crystal P6.

[0108] Here, the third switching unit C3 operates as in the second operation example (see FIGS. 14 to 16), so that no voltage is applied to the piezoelectric crystals other than the selected one. The present disclosure is not limited to this, and the third switching unit C3 may operate as in the first operation example (see FIGS. 11 to 13).

[0109] In other respects, the second modified example is similar to the first embodiment.

[0110] 2.6 Third Variant 34 and 35 show the configuration of piezo units 80b and 85b in a third modified example. Piezo unit 80b is similar to that in the first modified example. Piezo unit 85b differs from that in the second modified example in that a cooling member 89 is disposed between the third piezo element and nozzle 62. Cooling member 89 is similar to cooling member 84 except that it includes a cooling medium flow path 89a. While FIG. 35 shows the case where flow paths 84a and 89a are connected to a common chiller 84b, they may be connected to separate chillers.

[0111] In other respects, the third modification is similar to the second modification.

[0112] 2.7 Fourth Variant 36 and 37 show the configuration of a piezo unit 80c according to a fourth modification. The piezo unit 80c includes first, second, and fifth annular piezo elements. The first piezo element includes an annular electrode E1, an annular piezoelectric crystal P1, and an annular electrode E2, and is disposed around the capillary nozzle 62. The second piezo element includes an annular electrode E2, an annular piezoelectric crystal P2, and an annular electrode E3, and is disposed around the first piezo element. The fifth piezo element includes an annular electrode E3, an annular piezoelectric crystal P5, and an annular electrode E7, and is disposed around the second piezo element. The radial direction perpendicular to and outward from the central axis of the nozzle 62 is another example of the first direction in the present disclosure.

[0113] The first, second, and fifth piezoelectric elements can be fixed to the nozzle 62 with an adhesive, and the pressing member 81, the bolt 82, and the insulating member 83 may be omitted. The nozzle 62 may be made of an insulating material. The annular first, second, and fifth piezoelectric elements may have a length in the Y direction longer than that shown in FIG.

[0114] In other respects, the fourth modified example is similar to the first embodiment.

[0115] 2.8 Effect (1) According to the first embodiment and the first to third modifications, the target generation device 26 includes a nozzle 62, a first piezoelectric element, and a second piezoelectric element. The nozzle 62 includes a nozzle hole 62a that ejects a liquid target material for generating extreme ultraviolet light. The first piezoelectric element is disposed at a different position in the X direction relative to the nozzle 62 and vibrates the nozzle 62 by expanding and contracting in the X direction. The second piezoelectric element is disposed at a different position in the X direction relative to the first piezoelectric element and vibrates the nozzle 62 via the first piezoelectric element by expanding and contracting in the X direction.

[0116] This allows for an increased number of piezo elements to be mounted by stacking multiple piezo elements, and allows for the use of other piezo elements as spare piezo elements when one piezo element deteriorates or breaks down. This extends the life of the piezo unit 80a or the target generation device 26, potentially reducing the frequency of replacement. Furthermore, stacking multiple piezo elements in the X direction can reduce the installation space required for each piezo element in the piezo unit 80a. This also reduces the effort required to switch piezo elements, such as when searching for the optimal duty.

[0117] (2) According to the first embodiment and the first to fourth modifications, the first piezoelectric element includes the electrode E1 and the electrode E2, and the second piezoelectric element includes the electrode E2 and the electrode E3.

[0118] According to this, the first and second piezoelectric elements share the electrode E2, so that the installation space can be reduced.

[0119] (3) According to the first embodiment and the first to third modifications, the target generation device 26 includes a conductive pressing member 81 arranged at a different position in the X direction with respect to the second piezoelectric element, a conductive bolt 82 passing through the pressing member 81 and fixed to the nozzle 62, and an insulating member 83 arranged between the pressing member 81 and the electrode E3.

[0120] According to this, even if a plurality of piezoelectric elements are mounted on the target generation device 26, the pressing member 81, the bolt 82, and the insulating member 83 can be made common.

[0121] (4) According to the first embodiment and the first to fourth modifications, the target generation device 26 includes a piezoelectric element power supply 58 and a switching circuit 59. The piezoelectric element power supply 58 includes first and second output terminals O1 and O2, and generates a voltage between the first and second output terminals O1 and O2. The switching circuit 59 switches between a state a in which the first output terminal O1 is connected to the electrode E1 and the second output terminal O2 is connected to the electrode E2, and a state b in which the first output terminal O1 is connected to the electrode E2 and the second output terminal O2 is connected to the electrode E3.

[0122] According to this, by operating the switching circuit 59, it is possible to operate a plurality of piezo elements individually.

[0123] (5) According to the first embodiment and the first to fourth modifications, the target generation device 26 includes a target generation processor 51 that, when switching from state a to state b, acquires detection results of the target material ejected from the nozzle 62 while changing the duty ratio of the voltage applied to the second piezoelectric element, and searches for an appropriate value for the duty ratio.

[0124] According to this, even if the piezoelectric element is switched, an appropriate vibration can be transmitted to the nozzle 62 by searching for the optimum duty.

[0125] (6) According to the second operation example of the first embodiment, the switching circuit 59 also connects the second output terminal O2 to the electrode E3 in state a.

[0126] This makes it possible to suppress the displacement of the second piezoelectric element because the voltage between the electrodes E2 and E3 becomes almost 0. Also, it is more likely that the search for the optimum duty can be omitted.

[0127] (7) According to the first and second operation examples of the first embodiment, the switching circuit 59 also connects the first output terminal O1 to the electrode E1 in state b.

[0128] This makes it possible to suppress the displacement of the first piezoelectric element because the voltage between the electrodes E1 and E2 becomes almost zero.

[0129] (8) According to the first and third modifications, the target generation device 26 includes a cooling member 84 between the first piezoelectric element and the nozzle 62, the cooling member 84 including a flow path 84a for a cooling medium.

[0130] This allows a common cooling mechanism to be used to suppress temperature increases in a plurality of piezoelectric elements.

[0131] (9) According to the second and third modifications, the target generation device 26 includes a third piezoelectric element and a fourth piezoelectric element. The third piezoelectric element is disposed at a different position in the −X direction, which is different from the X direction, relative to the nozzle 62, and vibrates the nozzle 62 by expanding and contracting in the −X direction. The fourth piezoelectric element is disposed at a different position in the −X direction relative to the third piezoelectric element, and vibrates the nozzle 62 via the third piezoelectric element by expanding and contracting in the −X direction. The X direction and the −X direction intersect with the ejection direction of the target material.

[0132] According to this, since a plurality of piezoelectric elements are arranged in each of two directions relative to the nozzle 62, the number of piezoelectric elements that can be mounted can be increased.

[0133] (10) According to the second and third modified examples, the nozzle 62 is located between the first and third piezoelectric elements.

[0134] According to this, the first and third piezoelectric elements are arranged on both sides of the nozzle 62, so that even for a small nozzle 62, a plurality of piezoelectric elements can be arranged in each of two directions.

[0135] (11) According to the second and third variants, the first piezoelectric element includes electrodes E1 and E2, the second piezoelectric element includes electrodes E2 and E3, the third piezoelectric element includes electrodes E4 and E5, and the fourth piezoelectric element includes electrodes E5 and E6.

[0136] According to this, the first and second piezoelectric elements share the electrode E2, and the third and fourth piezoelectric elements share the electrode E5, so that the installation space can be reduced.

[0137] (12) According to second and third modifications, the target generation device 26 includes a piezoelectric element power supply 58 and a switching circuit 59. The piezoelectric element power supply 58 includes first and second output terminals O1 and O2 and generates a voltage between the first and second output terminals O1 and O2. The switching circuit 59 switches between a state a in which the first output terminal O1 is connected to electrode E1 and the second output terminal O2 is connected to electrode E2, a state b in which the first output terminal O1 is connected to electrode E2 and the second output terminal O2 is connected to electrode E3, a state d in which the first output terminal O1 is connected to electrode E4 and the second output terminal O2 is connected to electrode E5, and a state e in which the first output terminal O1 is connected to electrode E5 and the second output terminal O2 is connected to electrode E6.

[0138] According to this, by operating the switching circuit 59, the first to fourth piezoelectric elements can be operated individually.

[0139] (13) According to a first example of the switching circuit 59 of the second modified example, the target generation device 26 includes a piezoelectric element power supply 58 and a switching circuit 59. The piezoelectric element power supply 58 includes first and second output terminals O1 and O2 and generates a voltage between the first and second output terminals O1 and O2. The switching circuit 59 includes a changeover switch S6, a first switching unit C1, and a second switching unit C2. The changeover switch S6 connects the second output terminal O2 to either the first or second node N1 or N2. The first switching unit C1 switches between a first connection state in which the first output terminal O1 is connected to the electrode E1 and the first node N1 is connected to the electrode E2, and a second connection state in which the first output terminal O1 is connected to the electrode E2 and the first node N1 is connected to the electrode E3, with the second output terminal O2 connected to the first node N1. The second switching unit C2 switches between a third connection state in which the first output terminal O1 is connected to the electrode E4 and the second node N2 is connected to the electrode E5, and a fourth connection state in which the first output terminal O1 is connected to the electrode E5 and the second node N2 is connected to the electrode E6, while the second output terminal O2 is connected to the second node N2.

[0140] This allows the first and second switching units C1 and C2 to have the same configuration, which can reduce design and manufacturing costs.

[0141] (14) According to a second example of the switching circuit 59 of the second modified example, the target generation device 26 includes a piezoelectric element power supply 58 and a switching circuit 59. The piezoelectric element power supply 58 includes first and second output terminals O1 and O2 and generates a voltage between the first and second output terminals O1 and O2. The switching circuit 59 includes a third switching unit C3 and a fourth switching unit C4. The third switching unit C3 switches between a fifth connection state in which the first output terminal O1 is connected to electrodes E1 and E4 via a third node N3 and the second output terminal O2 is connected to a fourth node N4, and a sixth connection state in which the first output terminal O1 is connected to the fourth node N4 and the second output terminal O2 is connected to a fifth node N5. The fourth switching unit C4 switches between a seventh connection state in which the fourth node N4 is connected to the electrode E2 and the fifth node N5 is connected to the electrode E3, and an eighth connection state in which the fourth node N4 is connected to the electrode E5 and the fifth node N5 is connected to the electrode E6.

[0142] In this way, the third switching unit C3 is shared between the connection from the piezoelectric element power supply 58 to the electrodes E1 to E3 and E7 and the connection to the electrodes E4 to E6 and E8, so the number of switches can be reduced compared to the first example, and the risk of failure can be reduced.

[0143] (15) According to the fourth modification, the first piezoelectric element surrounds the nozzle 62, and the second piezoelectric element is disposed surrounding the first piezoelectric element.

[0144] This allows a plurality of piezoelectric elements to be reliably fixed to the thin nozzle 62.

[0145] 3. Piezo unit 80a attached to the bottom surface of nozzle 62 38 and 39 show the configuration of a piezo unit 80a in the second embodiment. Piezo unit 80a attached to the bottom surface of nozzle 62 is configured with first, second, and fifth piezo elements, an insulating member 83, and a pressing member 81 arranged in this order from the side closest to nozzle 62 in the Y direction. The Y direction is another example of the first direction in the present disclosure.

[0146] In other respects, the second embodiment is similar to the first embodiment.

[0147] 3.1 Fifth Variant 40 and 41 show the configuration of a piezo unit 80b in the fifth modified example. Piezo unit 80b attached to the bottom surface of nozzle 62 is composed of a cooling member 84, first, second, and fifth piezo elements, an insulating member 83, and a pressing member 81 arranged in this order from the side closest to nozzle 62 in the Y direction.

[0148] In other respects, the fifth modified example is similar to the first modified example.

[0149] 3.2 Sixth Variant 42 and 43 show the configuration of piezo units 80a and 85a in the sixth modified example. Piezo unit 80a attached to the bottom surface of nozzle 62 is composed of first, second, and fifth piezo elements, an insulating member 83, and a pressing member 81 arranged in this order from the side closest to nozzle 62 in the Y direction. Piezo unit 85a attached to the bottom surface of nozzle 62 is composed of third, fourth, and sixth piezo elements, an insulating member 88, and a pressing member 86 arranged in this order from the side closest to nozzle 62 in the Y direction. The trajectory of target 27 discharged from nozzle 62 is located between piezo units 80a and 85a.

[0150] In other respects, the sixth modification is similar to the second modification.

[0151] 3.3 Seventh Variant 44 and 45 show the configuration of piezo units 80b and 85b in the seventh modified example. Piezo unit 80b attached to the bottom surface of nozzle 62 is composed of a cooling member 84, first, second, and fifth piezo elements, an insulating member 83, and a pressing member 81, arranged in this order from the side closest to nozzle 62 in the Y direction. Piezo unit 85b attached to the bottom surface of nozzle 62 is composed of a cooling member 89, third, fourth, and sixth piezo elements, an insulating member 88, and a pressing member 86, arranged in this order from the side closest to nozzle 62 in the Y direction. The trajectory of target 27 ejected from nozzle 62 is located between piezo units 80b and 85b.

[0152] In other respects, the seventh modification is similar to the third modification.

[0153] 3.4 Effect (16) According to the second embodiment and the fifth to seventh modifications, the target generation device 26 includes a first piezoelectric element and a second piezoelectric element. The first piezoelectric element is disposed at a different position in the Y direction relative to the nozzle 62 and vibrates the nozzle 62 by expanding and contracting in the Y direction. The second piezoelectric element is disposed at a different position in the Y direction relative to the first piezoelectric element and vibrates the nozzle 62 via the first piezoelectric element by expanding and contracting in the Y direction. The Y direction is parallel to the ejection direction of the target material.

[0154] According to this, by arranging the piezoelectric elements on the bottom surface of the nozzle 62, it is possible to reduce the installation space in the X direction for the plurality of piezoelectric elements.

[0155] (17) According to the sixth and seventh modifications, the target generation device 26 includes a third piezoelectric element and a fourth piezoelectric element. The third piezoelectric element is disposed at a different position in the Y direction relative to the nozzle 62 and vibrates the nozzle 62 by expanding and contracting in the Y direction. The fourth piezoelectric element is disposed at a different position in the Y direction relative to the third piezoelectric element and vibrates the nozzle 62 via the third piezoelectric element by expanding and contracting in the Y direction. The trajectory of the target material discharged from the nozzle 62 is located between the first piezoelectric element and the third piezoelectric element.

[0156] According to this, the first and second piezoelectric elements and the third and fourth piezoelectric elements are arranged on both sides of the trajectory of the target material, so that many piezoelectric elements can be arranged even for a small nozzle 62.

[0157] 4.Other 4.1 Example of EUV light utilization equipment6 Figure 46 shows the configuration of an exposure apparatus 6a connected to the EUV light generation system 11. The exposure apparatus 6a, which serves as the EUV light utilization apparatus 6 (see Figure 1), includes a mask illumination unit 608 and a workpiece illumination unit 609. The mask illumination unit 608 illuminates a mask pattern on a mask table MT via a reflection optical system with EUV light incident from the EUV light generation system 11. The workpiece illumination unit 609 forms an image of the EUV light reflected by the mask table MT onto a workpiece (not shown) placed on a workpiece table WT via a reflection optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure apparatus 6a exposes the workpiece to EUV light reflecting the mask pattern by synchronously translating the mask table MT and the workpiece table WT. Electronic devices can be manufactured by transferring a device pattern onto a semiconductor wafer using the exposure process described above.

[0158] FIG. 47 shows the configuration of an inspection apparatus 6b connected to the EUV light generation system 11. The inspection apparatus 6b, which serves as the EUV light utilization apparatus 6 (see FIG. 1), includes an illumination optical system 603 and a detection optical system 606. The illumination optical system 603 reflects EUV light incident from the EUV light generation system 11 and irradiates a mask 605 placed on a mask stage 604. The mask 605 here includes a mask blank before a pattern is formed. The detection optical system 606 reflects the EUV light from the illuminated mask 605 and forms an image on the light-receiving surface of a detector 607. The detector 607 receives the EUV light and acquires an image of the mask 605. The detector 607 is, for example, a TDI (time delay integration) camera. The image of the mask 605 acquired through the above process is used to inspect the mask 605 for defects, and the inspection results are used to select a mask suitable for manufacturing electronic devices. The pattern formed on the selected mask is then exposed and transferred onto a photosensitive substrate using an exposure apparatus 6a, thereby manufacturing an electronic device.

[0159] 4.2 Processor Processors such as the EUV light generation processor 5 and the target generation processor 51 may be physically configured in the form of hardware to execute various processes included in the present disclosure. For example, the processor may be a computer including a memory in which a control program that defines various processes is stored and a processing device that executes the control program. The control program may be stored in a single memory, or may be stored separately in multiple memories that are physically separated, with the various processes defined by the control program as a collection of these memories. The processing device may be a general-purpose processing device such as a CPU, or a processing device for a specific purpose such as a GPU.

[0160] The processor may be programmed in the form of software to execute various processes included in the present disclosure. For example, the processor may be a dedicated device such as an ASIC or a programmable device such as an FPGA that implements the functions of executing various processes.

[0161] The various processes included in the present disclosure may be performed by a single computer, a single dedicated device, or a single programmable device, or may be performed by cooperation of multiple physically separate computers, multiple dedicated devices, or multiple programmable devices. The various processes may be performed by a combination of at least two of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0162] 4.3 Supplementary Information The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0163] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, words such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, 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 should also be construed as including combinations other than "A," "B," and "C."

Claims

1. a nozzle including a nozzle hole for discharging a liquid target material for generating extreme ultraviolet light; a first piezoelectric element disposed at a different position in a first direction relative to the nozzle, and vibrating the nozzle by expanding and contracting in the first direction; a second piezoelectric element that is disposed at a different position in the first direction relative to the first piezoelectric element and expands and contracts in the first direction to vibrate the nozzle via the first piezoelectric element; A target generating device including:

2. The target generation device according to claim 1, the first piezoelectric element includes a first electrode and a second electrode; the second piezoelectric element includes the second electrode and a third electrode; Target generator.

3. The target generation device according to claim 2, a conductive pressing member disposed at a different position in the first direction relative to the second piezoelectric element; a conductive bolt that passes through the pressing member and is fixed to the nozzle; an insulating member disposed between the pressing member and the third electrode; The target generation device further includes:

4. The target generation device according to claim 2, a piezoelectric element power supply including first and second output terminals, generating a voltage between the first and second output terminals; a switching circuit that switches between a first state in which the first output terminal is connected to the first electrode and the second output terminal is connected to the second electrode, and a second state in which the first output terminal is connected to the second electrode and the second output terminal is connected to the third electrode; The target generation device further includes:

5. The target generation device according to claim 4, a processor that, when switching from the first state to the second state, acquires a detection result of the target material discharged from the nozzle while changing a duty ratio of a voltage applied to the second piezoelectric element, and searches for an appropriate value of the duty ratio. The target generation device further includes:

6. The target generation device according to claim 4, the switching circuit also connects the second output terminal to the third electrode in the first state; Target generator.

7. The target generation device according to claim 4, the switching circuit also connects the first output terminal to the first electrode in the second state; Target generator.

8. The target generation device according to claim 1, a cooling member including a flow path for a cooling medium between the first piezoelectric element and the nozzle; The target generation device further includes:

9. The target generation device according to claim 1, a third piezoelectric element that is disposed at a different position in a second direction different from the first direction with respect to the nozzle, and that vibrates the nozzle by expanding and contracting in the second direction; a fourth piezoelectric element that is disposed at a different position in the second direction relative to the third piezoelectric element and expands and contracts in the second direction to vibrate the nozzle via the third piezoelectric element; further comprising the first and second directions intersect with the ejection direction of the target material; Target generator.

10. The target generation device according to claim 9, The nozzle is located between the first piezoelectric element and the third piezoelectric element. Target generator.

11. The target generation device according to claim 9, the first piezoelectric element includes a first electrode and a second electrode; the second piezoelectric element includes the second electrode and a third electrode; the third piezoelectric element includes a fourth electrode and a fifth electrode; the fourth piezoelectric element includes the fifth electrode and a sixth electrode; Target generator.

12. The target generation device according to claim 11, a piezoelectric element power supply including first and second output terminals, generating a voltage between the first and second output terminals; a switching circuit that switches between a first state in which the first output terminal is connected to the first electrode and the second output terminal is connected to the second electrode, a second state in which the first output terminal is connected to the second electrode and the second output terminal is connected to the third electrode, a third state in which the first output terminal is connected to the fourth electrode and the second output terminal is connected to the fifth electrode, and a fourth state in which the first output terminal is connected to the fifth electrode and the second output terminal is connected to the sixth electrode; The target generation device further includes:

13. The target generation device according to claim 11, a piezoelectric element power supply including first and second output terminals, generating a voltage between the first and second output terminals; A switching circuit; and the switching circuit further includes: a changeover switch that connects the second output terminal to either the first or second node; With the second output terminal connected to the first node, a first connection state in which the first output terminal is connected to the first electrode and the first node is connected to the second electrode, and a second connection state in which the first output terminal is connected to the second electrode and the first node is connected to the third electrode; a first switching unit; With the second output terminal connected to the second node, a third connection state in which the first output terminal is connected to the fourth electrode and the second node is connected to the fifth electrode, and a fourth connection state in which the first output terminal is connected to the fifth electrode and the second node is connected to the sixth electrode; a second switching unit; A target generating device comprising:

14. The target generation device according to claim 11, a piezoelectric element power supply including first and second output terminals, generating a voltage between the first and second output terminals; A switching circuit; and the switching circuit further includes: a third switching unit that switches between a fifth connection state in which the first output terminal is connected to the first and fourth electrodes via a third node and the second output terminal is connected to a fourth node, and a sixth connection state in which the first output terminal is connected to the fourth node and the second output terminal is connected to a fifth node; a fourth switching unit that switches between a seventh connection state in which the fourth node is connected to the second electrode and the fifth node is connected to the third electrode, and an eighth connection state in which the fourth node is connected to the fifth electrode and the fifth node is connected to the sixth electrode; A target generating device comprising:

15. The target generation device according to claim 1, the first piezoelectric element surrounds the nozzle, and the second piezoelectric element is disposed surrounding the first piezoelectric element; Target generator.

16. The target generation device according to claim 1, the first direction is parallel to the ejection direction of the target material; Target generator.

17. 17. The target generation device according to claim 16, a third piezoelectric element that is disposed at a different position in the first direction with respect to the nozzle and that vibrates the nozzle by expanding and contracting in the first direction; a fourth piezoelectric element that is disposed at a different position in the first direction relative to the third piezoelectric element and expands and contracts in the first direction to vibrate the nozzle via the third piezoelectric element; further comprising a trajectory of the target material discharged from the nozzle is located between the first piezoelectric element and the third piezoelectric element; Target generator.

18. The target generation device according to claim 1 ; a laser device that irradiates the target material discharged from the nozzle with laser light; an EUV collector mirror that collects the extreme ultraviolet light generated by irradiating the target material with the laser light; An extreme ultraviolet light generation system comprising:

19. A method for manufacturing an electronic device, comprising: a nozzle including a nozzle hole for discharging a liquid target material for generating extreme ultraviolet light; a first piezoelectric element disposed at a different position in a first direction relative to the nozzle, and vibrating the nozzle by expanding and contracting in the first direction; a second piezoelectric element that is disposed at a different position in the first direction relative to the first piezoelectric element and expands and contracts in the first direction to vibrate the nozzle via the first piezoelectric element; a target generation device including: a laser device that irradiates the target material discharged from the nozzle with laser light; an EUV collector mirror that collects the extreme ultraviolet light generated by irradiating the target material with the laser light; generating the extreme ultraviolet light by an extreme ultraviolet light generating system including: outputting the extreme ultraviolet light to an exposure device; exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus to manufacture an electronic device; A method for manufacturing an electronic device, comprising:

20. A method for manufacturing an electronic device, comprising: a nozzle including a nozzle hole for discharging a liquid target material for generating extreme ultraviolet light; a first piezoelectric element disposed at a different position in a first direction relative to the nozzle, and vibrating the nozzle by expanding and contracting in the first direction; a second piezoelectric element that is disposed at a different position in the first direction relative to the first piezoelectric element and expands and contracts in the first direction to vibrate the nozzle via the first piezoelectric element; a target generation device including: a laser device that irradiates the target material discharged from the nozzle with laser light; an EUV collector mirror that collects the extreme ultraviolet light generated by irradiating the target material with the laser light; and inspecting a mask for defects by irradiating the mask with the extreme ultraviolet light generated by the extreme ultraviolet light generating system, selecting a mask using the results of said testing; The pattern formed on the selected mask is transferred onto a photosensitive substrate by exposure. A method for manufacturing an electronic device, comprising:

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