Extreme-ultraviolet light generating system and manufacturing method of electronic device

Abstract

To stably maintain EUV energy stability for a long period of time.SOLUTION: An extreme-ultraviolet light generating system irradiates a target substance with a laser beam to generate extreme-ultraviolet light. The extreme-ultraviolet light generating system includes: a tank configured to store a liquid target substance; a nozzle configured to output the target substance stored in the tank; a piezo element configured to apply an oscillation to the target substance outputted from the nozzle to generate a droplet of the target substance; a droplet detection device configured to detect a time interval of passage of droplets outputted from the nozzle; and at least one processor. The processor acquires a first value of an oscillation parameter regarding an oscillation of the piezo element, acquires a variation of a time interval corresponding to each of a plurality of values including a first value of the oscillation parameter, and generates a droplet using a second value having a smaller time interval variation than the first value.SELECTED DRAWING: Figure 12

Description

Technical Field

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

Background Art

[0002] In recent years, with the miniaturization of semiconductor processes, the miniaturization of transfer patterns in optical lithography of semiconductor processes has been rapidly progressing. In the next generation, microfabrication of 10 nm or less will be required. For this reason, development of a semiconductor exposure apparatus combining an apparatus for generating extreme ultraviolet (EUV) light with a wavelength of about 13 nm and a reduction projection reflective optical system has been expected. As an EUV light generation apparatus, development of a Laser Produced Plasma (LPP) type apparatus using plasma generated by irradiating a target material with laser light has been progressing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

[0004] An extreme ultraviolet light generation system according to one aspect of the present disclosure is an extreme ultraviolet light generation system that irradiates a target material with laser light to generate extreme ultraviolet light, including a tank that stores a liquid target material, a nozzle that outputs the target material stored in the tank, a piezo element that vibrates the target material output from the nozzle to generate droplets of the target material, a droplet detection device that detects the time interval through which the droplets output from the nozzle pass, and at least one processor. The processor obtains a first value of a vibration parameter related to the vibration of the piezo element, obtains the variation in the time interval corresponding to each of a plurality of values including the first value of the vibration parameter, and generates droplets using a second value for which the variation in the time interval is smaller than the first value.

[0005] A method for manufacturing an electronic device according to one aspect of the present disclosure includes a tank that stores a liquid target material, a nozzle that outputs the target material stored in the tank, a piezo element that vibrates the target material output from the nozzle to generate droplets of the target material, a droplet detection device that detects the time interval through which the droplets output from the nozzle pass, and at least one processor. The processor obtains a first value of a vibration parameter related to the vibration of the piezo element, obtains the variation in the time interval corresponding to each of a plurality of values including the first value of the vibration parameter, generates droplets using a second value for which the variation in the time interval is smaller than the first value, generates extreme ultraviolet light by an extreme ultraviolet light generation system that irradiates the target material with laser light to generate extreme ultraviolet light, outputs the extreme ultraviolet light to an exposure device, and includes exposing the photosensitive substrate to the extreme ultraviolet light in the exposure device in order to manufacture an electronic device.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes a tank that stores a liquid target substance, a nozzle that outputs the target substance stored in the tank, a piezo element that vibrates the target substance output from the nozzle to generate droplets of the target substance, a droplet detection device that detects a time interval through which the droplets output from the nozzle pass, and at least one processor. The processor acquires a first value of a vibration parameter related to the vibration of the piezo element, acquires the variation in the time interval corresponding to each of a plurality of values including the first value of the vibration parameter, generates droplets using a second value for which the variation in the time interval is smaller than the first value, generates extreme ultraviolet light by an extreme ultraviolet light generation system that irradiates the target substance with laser light to generate extreme ultraviolet light, inspects a reticle for defects by irradiating the reticle with the extreme ultraviolet light, selects a reticle using the result of the inspection, and includes exposing and transferring a pattern formed on the selected reticle onto a photosensitive substrate.

Brief Description of the Drawings

[0007] Some embodiments of the present disclosure will be described below by way of example only with reference to the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

[0008] -Table of Contents- 1. Explanation of Terms 1.1 Defect Bonding Rate 1.2 Duty 2. Overview of EUV Light Generation System According to Comparative Example 2.1 Configuration 2.2 Operation 2.2.1 Example of DL Bonding Adjustment 2.2.2 Example of DL Bonding Control 2.3 Problems 3. Embodiment 1 3.1 Configuration 3.2 Operation 3.2.1 Example of DL Bonding Adjustment 3.2.2 Example of DL Bonding Control 3.3 Functions and Effects 3.4 Variations 4. Embodiment 2 4.1 Configuration 4.2 Operation 4.3 Functions and Effects 5. Embodiment 3 5.1 Configuration 5.2 Operation 5.3 Functions and Effects 6. Method for Manufacturing Electronic Device 7. Others

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and duplicate explanations are omitted.

[0010] 1. Explanation of Terms 1.1 Poor Bonding Rate FIG. 1 is a schematic diagram showing a configuration for measuring a droplet passing interval which is a time interval during which a droplet passes. FIG. 1 shows a nozzle for ejecting a target substance, a droplet formed by the target substance ejected from the nozzle, and a droplet detection sensor which is a timing sensor for detecting the timing at which the droplet passes. The droplet detection sensor is disposed to face the position where the droplet passes. The droplet detection sensor includes a light receiving element (not shown) and detects a change in the voltage of the light receiving element accompanying the passage of the droplet. A detection threshold value for a light emission trigger for the pulse laser device is set for the voltage of the light receiving element.

[0011] Note that the "droplet" is a form of the target supplied into the chamber. The droplet may mean a droplet-shaped target that has become substantially spherical due to the surface tension of the molten target substance. In the specification and drawings, the notation "DL" is an abbreviation for "droplet".

[0012] The jet of the target substance ejected from the nozzle is separated into droplets and aggregates to form DL. The normally output and properly combined DLs create a relatively large shadow. Therefore, when the normally output DL passes through the droplet detection sensor, the voltage of the light receiving element drops significantly. As a result, the voltage of the light receiving element falls below the detection threshold value for the light emission trigger and becomes the trigger origin of the pulse laser device.

[0013] On the other hand, depending on the DL generation conditions, DLs with insufficient combined numbers and non-combined DLs are generated. The shadow caused by the DL with poor bonding is small and the voltage drop of the light receiving element is small, but there may be cases where the voltage of the light receiving element falls below the detection threshold value for the light emission trigger and becomes the trigger origin of the pulse laser device.

[0014] To avoid such an event, the DL generation conditions are determined using, as an index, the detection interval (DL passage interval [ns]) from when the voltage of the light-receiving element falls below the light emission trigger detection threshold until the next time the voltage of the light-receiving element falls below the light emission trigger detection threshold. That is, an allowable range is set for the DL passage interval, and it is determined whether the DL passage interval is within the allowable range.

[0015] Figure 2 is a schematic diagram of the output signal (passage timing signal) of the light-receiving element of the droplet detection sensor. The horizontal axis in Figure 2 represents time, and the vertical axis represents, for example, voltage. F2A in Figure 2 shows the case where the DL passage interval is within the allowable range. Also, F2B in Figure 2 shows the case where the DL passage interval is outside the allowable range. The "bonding defect rate" is calculated by Equation 1 below.

[0016] Bonding defect rate [%] = (number of DLs with DL passage interval outside allowable range ÷ number of DL samples) × 100 … (Equation 1)

[0017] 1.2 Duty Figure 3 is a diagram showing an example of the voltage waveform applied to the piezo element for generating droplets. Figure 3 is an example of a rectangular wave with a predetermined period. The horizontal axis in Figure 3 represents time, and the vertical axis represents voltage. "Duty" is the ratio [%] of the on-time (high potential side voltage time) Ts to one period T of the rectangular wave.

[0018] 2. Outline of EUV light generation system according to comparative example 2.1 Configuration Figure 4 is a diagram schematically showing a configuration example of an extreme ultraviolet light generation system 10 (hereinafter referred to as EUV light generation system 10) according to a comparative example. The comparative example of the present disclosure is a form that the applicant recognizes as being known only to the applicant and is not a publicly known example recognized by the applicant. The notation "EUV light" is an abbreviation notation for "extreme ultraviolet light".

[0019] The EUV light generation system 10 includes a target generation system 20, a chamber 22, an EUV light generation processor 24 including a control program 25, a delay circuit 26, and a pulse laser device 90. The target generation system 20 includes a target control system 30, a target supply unit 32, and an inert gas supply unit 34. The target control system 30 includes a target generation processor 36, a piezo power supply 37, and a heater power supply 38.

[0020] In the present disclosure, a processor includes a storage device in which a control program 25 is stored and a CPU (Central Processing Unit) that executes the control program 25. The processor is specially configured or programmed to execute various processes included in the present disclosure. In the present disclosure, the EUV light generation processor 24 and the target generation processor 36 are separate, but the EUV light generation processor 24 and the target generation processor 36 may be configured as one processor. In that case, one processor may perform the operations of the EUV light generation processor 24 and the operations of the target generation processor 36.

[0021] The target supply unit 32 includes a nozzle 42 having a hole for outputting a molten target substance 40, a filter 43, a tank 44 for storing the target substance 40, a heater 45, a temperature sensor 46, a piezo element 47, and a pressure regulator 48.

[0022] The nozzle 42 corresponds to the nozzle shown in FIG. 1. The filter 43 is disposed upstream of the nozzle 42 and removes impurities contained in the target substance 40. The target substance 40 is, for example, tin (Sn). The nozzle 42, the heater 45, and the temperature sensor 46 are fixed to the tank 44. The piezo element 47 is fixed to the nozzle 42.

[0023] The pressure regulator 48 is installed in a pipe 49 between the inert gas supply unit 34 and the tank 44. The inert gas supplied from the inert gas supply unit 34 may be, for example, Ar or He gas.

[0024] The target substance 40 inside the tank 44 is output as a jet 81 from the nozzle 42 due to the pressure difference between the inert gas supplied from the pressure regulator 48 and the pressure inside the chamber 22. When the nozzle 42 is vibrated by the piezo element 47, the jet 81 output from the nozzle 42 is separated into droplets, becoming droplets 82 (hereinafter referred to as DL82).

[0025] The chamber 22 includes a droplet detection device 50, a target image measurement device 52, a laser focusing optical system 54, an XY-axis stage 55, and a target recovery unit 56.

[0026] The droplet detection device 50 (hereinafter referred to as the DL detection device 50) corresponds to the droplet detection sensor shown in FIG. 1. The DL detection device 50 includes a light source unit 61 and a light receiving unit 62. The light source unit 61 includes a CW laser 63 as a light source, an illumination optical system 64 as a condenser lens, and a window 65. The light source unit 61 is arranged to illuminate the DL82 at a predetermined position P on the target trajectory between the nozzle 42 of the target supply unit 32 and the plasma generation region 80.

[0027] The light receiving unit 62 includes a photosensor 66 as a light receiving element, a window 67 and a light receiving optical system 68 for guiding the CW laser light to the photosensor 66. The light receiving unit 62 is arranged to receive the CW laser light output from the light source unit 61. When the DL82 blocks the CW laser light, the output of the photosensor 66 fluctuates. The light receiving unit 62 generates a passing timing signal TS indicating the timing when the DL82 passes through the position P based on this fluctuation, and inputs the passing timing signal TS to the EUV light generation processor 24.

[0028] The passing timing signal TS is input to the delay circuit 26 via the EUV light generation processor 24. A signal line for setting the delay time of the delay circuit 26 from the EUV light generation processor 24 may be connected to the delay circuit 26.

[0029] The delay circuit 26 outputs the emission trigger signal Tr to the pulse laser device 90. The delay circuit 26 also outputs the exposure signal ES and the optical shutter signal SS to the target image measurement device 52.

[0030] The target image measurement device 52 includes a light source unit 71 and a light receiving unit 72. The light source unit 71 includes a flash lamp 73 as a light source, an illumination optical system 74 as a condenser lens, and a window 75. The light source unit 71 is arranged to illuminate the DL82 in the plasma generation region 80. The light source unit 71 turns on the flash lamp 73 based on the lighting signal IS input from the EUV light generation processor 24.

[0031] The light receiving unit 72 includes an image sensor 76, a window 77 that guides the flash lamp light of the flash lamp 73 to the image sensor 76, a light receiving optical system 78, and an optical shutter 79. The light receiving unit 72 is arranged to receive the flash lamp light output from the light source unit 71.

[0032] The image sensor 76 has light receiving elements (not shown) arranged two-dimensionally, and is, for example, a CCD (Charge-coupled device) type image sensor. The light receiving unit 72 images the region including the plasma generation region 80 to generate image data ID, and inputs the image data ID to the EUV light generation processor 24.

[0033] The light receiving unit 72 starts the exposure of the image sensor 76 based on the exposure signal ES input from the delay circuit 26. The light receiving unit 72 opens and closes the optical shutter 79 based on the optical shutter signal SS input from the delay circuit 26. The light receiving optical system 78 forms an image of the DL82 by the flash lamp light output from the light source unit 71 on the light receiving surface of the image sensor 76 when the optical shutter 79 is in the open state. The image sensor 76 photoelectrically converts the image of the DL82 formed on the light receiving surface to generate image data ID representing the image of the DL82, and outputs it to the EUV light generation processor 24.

[0034] The pulsed laser device 90 outputs pulsed laser light based on the emission trigger signal Tr. The pulsed laser device 90 may be, for example, a CO2 laser device. Further, the pulsed laser device 90 may be a solid-state laser device having a crystal doped with impurities in any of YVO4 (yttrium vanadium oxide), YLF (yttrium lithium fluoride), and YAG (yttrium aluminum garnet) as the laser medium.

[0035] The laser focusing optical system 54 is an optical system that focuses the pulsed laser light output from the pulsed laser device 90 and guided into the chamber 22 onto the plasma generation region 80. The laser focusing optical system 54 is supported by the XY stage 55. The XY stage 55 can move the laser focusing optical system 54 in two axial directions, the X-axis direction and the Y-axis direction. By adjusting the position of the laser focusing optical system 54 with the XY stage 55, the focusing position of the pulsed laser light can be adjusted. The optical elements are arranged such that the focusing position of the laser focusing optical system 54 substantially coincides with the plasma generation region 80.

[0036] The target recovery unit 56 is arranged on the orbit of the DL82 and recovers the DL that has not been irradiated with the pulsed laser light.

[0037] Also, an EUV light focusing mirror (not shown) is arranged in the chamber 22. The EUV light focusing mirror has a reflecting surface in the shape of a rotational ellipsoid. A multilayer reflection film in which molybdenum and silicon are alternately laminated is formed on the reflecting surface of the EUV light focusing mirror. The EUV light focusing mirror has a first focus and a second focus, and is arranged such that the first focus is located in the plasma generation region 80. The EUV light focusing mirror selectively reflects EUV light from the radiation light emitted from the plasma generated in the plasma generation region 80. The EUV light focusing mirror focuses the selectively reflected EUV light on the second focus (intermediate focusing point). An aperture (not shown) is arranged at the intermediate focusing point, and the EUV light that has passed through the aperture is incident on an exposure device or an inspection device (not shown).

[0038] 2.2 Operation FIG. 5 is a flowchart showing the main flow of the operation of the EUV light generation system 10. In step S1, when the EUV light generation processor 24 starts executing the control program 25, a target generation signal is input from the EUV light generation processor 24 to the target generation processor 36.

[0039] In step S2, the target generation processor 36 controls the heater power supply 38 based on the detected value of the temperature sensor 46 so that the Sn in the target supply unit 32 reaches a temperature equal to or higher than the melting point, and melts the Sn accommodated in the tank 44 to make it liquid. For example, the target generation processor 36 controls the heater power supply 38 so that the Sn in the target supply unit 32 reaches a predetermined temperature of 232°C to 300°C. Further, the target generation processor 36 controls the inert gas to a predetermined pressure, for example, a pressure of 0.2 MPa to 40 MPa, by the pressure regulator 48, and outputs the liquid Sn in the tank 44 to the outside of the nozzle 42.

[0040] In step S3, the target generation processor 36 vibrates the nozzle 42 so that the jet 81 of the liquid Sn output from the nozzle 42 becomes DL, and further a plurality of DLs combine to generate a combined DL having a predetermined diameter and a predetermined period. For example, the target generation processor 36 applies a rectangular wave voltage waveform having a predetermined frequency and a predetermined duty to the piezo element 47 via the piezo power supply 37, and vibrates the nozzle 42 at a predetermined vibration frequency.

[0041] Hereinafter, in this specification, "DL" in the case of generating DL or generating DL refers to combined DL unless otherwise specified. In this specification, the duty of the rectangular wave voltage waveform applied to the piezo element 47 is referred to as "the duty of the piezo element 47" or simply "duty". Duty is one of the vibration parameters related to the vibration of the piezo element 47, and the value of duty is referred to as "duty value". The duty value is an example of "the value of duty" in the present disclosure.

[0042] Also, in step S3, the target generation processor 36 measures the coupling failure rate of DL with respect to Duty, and associates and stores Duty and the coupling failure rate. Then, the target generation processor 36 drives the piezoelectric element 47 with a rectangular wave of a Duty value whose coupling failure rate is less than the threshold value. A specific example of the subroutine applied to the DL coupling adjustment in step S3 will be described later (Fig. 6).

[0043] In step S4, the target generation processor 36 starts control to maintain the coupling state of DL by finely adjusting the Duty of the piezoelectric element 47 using the coupling failure rate of DL as an index. Note that the coupling control of DL may be performed regardless of whether the pulsed laser light is not irradiated to DL (when EUV is not emitted) or irradiated (when EUV is emitted). A specific example of the subroutine applied to the DL coupling control in step S4 will be described later (Fig. 8).

[0044] 2.2.1 Example of DL coupling adjustment Fig. 6 is a flowchart showing an example of the DL coupling adjustment subroutine applied to step S3 of Fig. 5. This subroutine is executed when EUV is not emitted.

[0045] When the process of step S3 is started, in step S11, the target generation processor 36 sets the Duty of the piezoelectric element 47 to the lower limit value D LL which is the initial value. The target generation processor 36 can change the value of Duty in units of the step amount d within the numerical range from the lower limit value D LL to the upper limit value D UL . As typical parameter values of Duty, the lower limit value D LL may be 1 [%], the upper limit value D UL may be 99 [%], and the step amount d may be 0.1 [%].

[0046] In step S12, the target generation processor 36 measures the connection failure rate of DL for the set Duty value. That is, the target generation processor 36 controls the piezo power supply 37 to apply the voltage waveform of the rectangular wave of the set Duty value to the piezo element 47, and drives the piezo element 47 via the piezo power supply 37 to generate DL82. Further, the target generation processor 36 acquires the passing timing signal TS via the EUV light generation processor 24, measures the DL passing interval based on the passing timing signal TS, and calculates the connection failure rate of the set Duty value based on the above-mentioned formula 1. The number of DLs for each Duty value, which is the number of connection failure rate calculation samples, may be 10,000. Then, the target generation processor 36 associates and stores the Duty and the connection failure rate.

[0047] In step S13, the target generation processor 36 determines whether the set Duty value is less than the upper limit value D UL If the determination result in step S13 is a Yes determination, the target generation processor 36 proceeds to step S14, sets a new Duty value obtained by adding the step amount d to the set Duty value, and then returns to step S12.

[0048] Until the Duty value reaches the upper limit value D UL , the loop of steps S12 to S14 is repeated. In this way, while increasing the Duty from the lower limit value D LL to the upper limit value D UL in increments of the step amount d and measuring the connection failure rate for each Duty value, characteristic data indicating the relationship between the Duty and the connection failure rate can be obtained.

[0049] If the determination result in step S13 is a No determination, the target generation processor 36 proceeds to step S15. In step S15, the target generation processor 36 selects the region with the largest Duty width among the region candidates having a continuous Duty width where the connection failure rate is less than the threshold value A1.

[0050] In step S16, the target generation processor 36 sets the value at the center of the region selected in step S15 as the operation Duty value. After step S16, the target generation processor 36 returns to the flowchart of FIG. 5.

[0051] FIG. 7 is a graph showing an example of the coupling failure rate measured in DL coupling adjustment. The horizontal axis of FIG. 7 represents Duty, and the vertical axis represents the coupling failure rate. FIG. 7 is an example of the coupling failure rate obtained by scanning the Duty value from 1[%] to 99[%] in steps of 0.1[%] with the irradiation of the pulsed laser light stopped.

[0052] In FIG. 7, regions that satisfy the condition that the width of continuous Duty for which the coupling failure rate is less than the threshold value A1 is equal to or greater than the specified width are four region candidates CA1, CA2, CA3, and CA4. The region candidates CA1, CA2, CA3, and CA4 are regions in the vicinity of Duty values of 3%, 28%, 77%, and 92%, respectively. Among these region candidates, the region with the largest Duty width is selected as the maximum Duty width region. Here, region candidate CA3 is selected as the maximum Duty width region, and the Duty value at the center of the Duty range of region candidate CA3 is selected as the Duty value suitable for the generation of DL82.

[0053] 2.2.2 Example of DL coupling control FIG. 8 is a flowchart showing an example of a DL coupling control subroutine applied to step S4 of FIG. 5. In this subroutine, the Duty is controlled using the coupling failure rate as an index. This subroutine can be implemented both when EUV is not emitting and when EUV is emitting.

[0054] When the process of step S4 starts, in step S21, the target generation processor 36 reads the initial settings. The parameters for the initial settings include the search range ΔDu of the Duty value when evaluating EUV performance, the search level N of Duty, the threshold value A2 of the bonding failure rate, and the number of bonding failure rate calculation samples. The target generation processor 36 reads the initial setting values of these parameters. The search range ΔDu may be 0.02 [%], the search level N may be 5, the threshold value A2 may be 0.02 [%], and the number of bonding failure rate calculation samples may be 10,000.

[0055] The processes of steps S22 to S23 are processes that are repeatedly performed as long as the condition that it is necessary to maintain the bonding state of DL is satisfied. When it is no longer necessary to maintain the bonding state of DL due to a stop command or the like from an external device such as an exposure apparatus (not shown) or an operator, the target generation processor 36 ends the loop process, ends this subroutine, and returns to the flowchart of FIG. 5.

[0056] In step S22, the target generation processor 36 obtains the bonding failure rate for each Duty value at the search level N centered on the operating Duty value which is the set Duty value. The interval of the search level N is the search range ΔDu respectively, and the order of the Duty values for which the bonding failure rate is obtained may be arbitrary.

[0057] In step S23, the target generation processor 36 specifies the Duty values that are less than the threshold value A2 of the bonding failure rate among the Duty values for which the bonding failure rate was obtained in step S22, and which are the Duty values at both ends on the plus side and the minus side. Further, the target generation processor 36 sets the center value (average value) of the Duty values at both ends on the plus side and the minus side as the new operating Duty value. The specific operations of steps S22 and S23 will be described with reference to FIG. 9.

[0058] After step S23, when it is no longer necessary to continue the loop process due to a stop command or the like as described above, the target generation processor 36 returns to the flowchart of FIG. 5.

[0059] FIG. 9 is a diagram for explaining the operation Duty value set by DL coupling control. The horizontal axis of FIG. 9 represents Duty, and the vertical axis represents the value of the coupling failure rate [%]. The circles in FIG. 9 represent the plot positions of the coupling failure rate with respect to Duty, and the numbers in the circles represent the search order. In the example shown in FIG. 9, the Duty values for search orders 1, 2, 3, 4, and 5 are "current value", "current value - ΔDu", "current value - ΔDu × 2", "current value + ΔDu", and "current value + ΔDu × 2", respectively.

[0060] Here, the coupling failure rates at the Duty values of search orders 1 to 4 are each less than the threshold value A2, and the coupling failure rate at the Duty value of search order 5 is greater than or equal to the threshold value A2. Therefore, the target generation processor 36 specifies the Duty value of search order 4, which is the most positive side, that is, the largest value, among the Duty values of search orders 1 to 4 where the coupling failure rate is less than the threshold value A2. Further, the target generation processor 36 specifies the Duty value of search order 3, which is the most negative side, that is, the smallest value, among the Duty values of search orders 1 to 4 where the coupling failure rate is less than the threshold value A2. Furthermore, the target generation processor 36 sets the central value of these two Duty values as the operation Duty value.

[0061] 2.3 Problems In the EUV light generation system 10 according to the comparative example, since the Duty cannot be optimized further if the coupling failure rate is below the threshold value, the variation in the DL passing interval due to the variation in the speed of each DL cannot be reduced below a certain level, and the EUV energy stability 3σ is not improved. Also, the coupling failure rate may vary over time, and the Duty determined by the coupling failure rate may not be maintained for a long time. In that case, it was necessary to change the Duty once set and perform a condition search.

[0062] For this reason, a Duty control method for stably maintaining the EUV energy stability 3σ for a long time has been demanded.

[0063] 3. Embodiment 1 3.1 Configuration Since the configuration of the EUV light generation system 10A according to Embodiment 1 is the same as that of the EUV light generation system 10 of the comparative example shown in FIG. 4, the description thereof is omitted.

[0064] 3.2 Operation The operation of the EUV light generation system 10A according to Embodiment 1 is different from the operation of the EUV light generation system 10 of the comparative example in that the DL coupling adjustment subroutine and the DL coupling control subroutine are different.

[0065] The DL coupling adjustment subroutine according to Embodiment 1 operates Duty using the DL passing interval variation σ as an index. Further, the DL coupling control subroutine according to Embodiment 1 uses an optimization search algorithm that operates Duty using the DL passing interval variation σ as an index. The DL passing interval variation σ [ns] is calculated by the following Equation 2.

[0066]

Equation

[0067] 3.2.1 Example of DL Coupling Adjustment FIG. 10 is a flowchart showing an example of the DL coupling adjustment subroutine according to Embodiment 1. This subroutine may be performed without EUV emission, may be performed during EUV emission, or may be continuously performed regardless of the presence or absence of EUV emission.

[0068] In step S11, the target generation processor 36 sets the Duty of the piezoelectric element 47 to the lower limit value D which is the initial value. LL As a typical value of the Duty parameter, the lower limit value D LL is 1 [%], the upper limit value D UL is 99 [%], and the step amount d may be 0.1 [%].

[0069] Also, the target generation processor 36 acquires initial parameters. The initial parameters include the number of samples for calculating the DL passing interval σ, the moving average number Nσ of the DL passing interval σ, and the continuous duty ratio determination threshold B. As typical values of the initial parameters, the number of samples for calculating the DL passing interval σ may be 10,000, and the moving average number Nσ of the DL passing interval σ may be 0.6 [%]. If the step amount d is 0.1 [%], the fact that the moving average number Nσ of the DL passing interval σ is 0.6 [%] means that the number of intervals of the moving average is 0.6 ÷ 0.1 = 6. The continuous duty ratio determination threshold B may be set by obtaining a value that can maintain a long-term connection through experiments or the like. The continuous duty ratio determination threshold B may be 0.6 [%] or more.

[0070] In step S31, the target generation processor 36 measures the DL passing interval σ of the set duty value. That is, the target generation processor 36 controls the piezo power supply 37 to apply the voltage waveform of the rectangular wave of the set duty value to the piezo element 47, and drives the piezo element 47 through the piezo power supply 37 to generate the DL82. Further, the target generation processor 36 acquires the passing timing signal TS through the EUV light generation processor 24, measures the DL passing interval based on the passing timing signal TS, and calculates the DL passing interval σ based on Equation 2. Then, the target generation processor 36 associates and stores the duty and the DL passing interval σ. Note that the target generation processor 36 measures the DL passing interval σ with conditions other than the duty being constant.

[0071] Until the duty value reaches the upper limit value D UL the process of step S31 is repeated. In this way, by increasing the duty value in increments of the step amount d from the lower limit value D LL to the upper limit value D UL and measuring the DL passing interval σ for each duty value, characteristic data indicating the relationship between the duty and the DL passing interval σ can be obtained.

[0072] In step S32, the target generation processor 36 acquires area candidates based on the characteristic data acquired in step S31. The area candidates are areas having a continuous Duty width where the DL passing interval σ is less than the threshold value S1 and where the Duty width is equal to or greater than the continuous Duty width determination threshold value B.

[0073] In step S33, the target generation processor 36 calculates the moving average of the DL passing interval σ with respect to Duty for each area candidate selected in step S32. Instead of the moving average, the target generation processor 36 may perform a filtering operation on the data series to smooth the prominent data.

[0074] In step S34, the target generation processor 36 sets the Duty value at which the moving average calculated in step S33 is minimized as the operating Duty value.

[0075] FIG. 11 is a graph showing an example of characteristic data indicating the relationship between Duty and the DL passing interval σ obtained in DL coupling adjustment. The horizontal axis in FIG. 11 represents Duty [%], and the vertical axis represents the DL passing interval σ [ns]. F11A in FIG. 11 is an example of the DL passing interval σ obtained by scanning the Duty value from 1 [%] to 99 [%] in 0.1 [%] increments with the irradiation of the pulsed laser light stopped.

[0076] In F11A, the areas that satisfy the condition that the continuous Duty width where the DL passing interval σ is less than the threshold value S1 is equal to or greater than the continuous Duty width determination threshold value B are four area candidates CA11, CA12, CA13, and CA14. The area candidates CA11, CA12, CA13, and CA14 are areas near Duty values of 3 [%], 53 [%], 56 [%], and 93 [%], respectively.

[0077] Here, for the four region candidates CA11, CA12, CA13, and CA14, the moving average of the DL passing interval σ with respect to Duty is calculated for each, and the Duty value at which the moving average is minimized is set as the operating Duty value. F11B in FIG. 11 is an enlarged graph of the region candidate CA12 and shows the set operating Duty value.

[0078] 3.2.2 Example of DL coupling control FIG. 12 is a flowchart showing an example of a DL coupling control subroutine according to Embodiment 1. In the DL coupling control subroutine of Embodiment 1, the control of Duty is performed using the DL passing interval σ as an index. This subroutine can be implemented both during EUV non-emission and during EUV emission. Duty is an example of the "oscillation parameter" in the present disclosure.

[0079] In step S21, the target generation processor 36 reads the initial settings. The parameters for initial setting include the search range ΔDu of the Duty value when evaluating EUV performance, the search level N of Duty, the movement amount d of Duty, and the number of samples for calculating the DL passing interval σ. The target generation processor 36 reads the initial setting values of these respective parameters. The search range ΔDu is preferably 0.02 [%], the search level N is preferably 2 or more, for example 5, the movement amount d of Duty is 0.02 [%], and the number of samples for calculating the DL passing interval σ may be 10000.

[0080] The processes of steps S41 to S43 are processes for maintaining the coupling state of the DL by finely adjusting the Duty value using the DL passage interval σ as an index, and are repeatedly performed as long as it is necessary to maintain the coupling state of the DL. When it becomes unnecessary to maintain the coupling state of the DL due to a stop command or the like of the DL output from an external device such as an exposure apparatus (not shown) or an operator, the target generation processor 36 ends the repetitive process and ends this subroutine. In step S41, the target generation processor 36 drives the piezo element 47 with the Duty values at the search level N centered on the current value of Duty based on the initial settings read in step S21 to generate the DL. Further, the target generation processor 36 acquires the DL passage interval σ for the generated DL and obtains the correlation between Duty and the DL passage interval σ. The intervals at the search level N are each a search width ΔDu, and the order of the Duty values for which the DL passage interval σ is acquired may be arbitrary. Also, the search range is desirably set to a width such that a significant difference appears in the DL coupling performance. The current value of Duty is an example of the "first value" in the present disclosure. The initial current value of Duty in the DL coupling control may be the operating Duty obtained by the DL coupling adjustment. The Duty values at the search level N centered on the current value of Duty are the "plurality of values including the first value" in the present disclosure.

[0081] In step S42, the target generation processor 36 calculates a linear approximation straight line with Duty on the horizontal axis and the DL passage interval σ on the vertical axis in the correlation between Duty and the DL passage interval σ acquired in step S41, and specifies the gradient thereof.

[0082] In step S43, based on the slope of the approximate straight line identified in step S42, the target generation processor 36 changes the Duty in the performance improvement direction, that is, the direction in which the DL passage interval σ decreases. For example, when the slope is positive, the target generation processor 36 changes the Duty from the current value (0 position) in the negative direction. When the slope is negative, the target generation processor 36 changes the Duty from the current value in the positive direction. The change in Duty at this time may be set to a Duty value that is different from the current value by the amount of movement d, or a Duty value in the performance improvement direction. Also, the amount of change in Duty may vary depending on the value of the slope. Thereafter, the piezo element 47 is driven by a Duty value with a smaller DL passage interval σ. The changed Duty value is an example of the "second value" in the present disclosure. Note that when the absolute value of the slope can be regarded as 0, the target generation processor 36 may not change the Duty.

[0083] The target generation processor 36 returns to step S41 and repeats the same process with the changed Duty value as the current value.

[0084] FIG. 13 is a graph for explaining the process of changing the Duty in the performance improvement direction. The horizontal axis in FIG. 13 represents the Duty, and the vertical axis represents the DL passage interval σ. The circles in FIG. 13 represent the plot positions of the DL passage interval σ with respect to the Duty, and the numbers in the circles represent the search order. In the example shown in FIG. 13, the Duty values for the search orders 1, 2, 3, 4, and 5 are "current value", "current value - ΔDu", "current value - ΔDu × 2", "current value + ΔDu", and "current value + ΔDu × 2", respectively. From these five plot points, an approximate straight line AL1 shown by a dashed line in FIG. 13 can be obtained by linear approximation.

[0085] In the example of FIG. 13, the slope S of the approximate straight line AL1 is greater than 0, and the direction of decreasing the Duty with respect to the current value is the direction of improving the value of the DL passage interval σ. Therefore, in this case, as the process of step S43, the Duty value is changed by the amount of movement d in the negative direction from the current value.

[0086] FIG. 14 is a graph showing an example of changes in the DL passing interval σ and Duty with respect to the control time in the DL coupling control according to Embodiment 1. In this example, the DL passing interval σ is improved by controlling so that the Duty value increases globally.

[0087] 3.3 Operation and Effect According to the EUV light generation system 10A according to Embodiment 1, even when the coupling failure rate is below the threshold value, the Duty of the piezo element 47 can be optimized, and the DL passing interval σ can be reduced.

[0088] Therefore, even when there are time-dependent changes in the piezo element 47 or the like, the relative irradiation position between the DL and the laser light is stable, the EUV energy stability (for example, 3σ) is improved, and the generation of fragments is also suppressed. Furthermore, the EUV emission cycle is stabilized.

[0089] Also, according to the EUV light generation system 10A according to Embodiment 1, since the moving average of the DL passing interval σ selects the minimum Duty value from a good Duty region, even if there is some disturbance, the DL passing interval σ does not deteriorate significantly, and the once-set Duty value can be maintained for a relatively long period.

[0090] FIG. 15 is a graph showing the correlation between the DL passing interval σ and the EUV performance. The horizontal axis of FIG. 15 represents the number of pulses of the generated EUV light, and the vertical axis represents the EUV energy. F15A in FIG. 15 shows the case of the EUV light generation system 10 according to the comparative example, and F15B shows the case of the EUV light generation system 10A according to Embodiment 1, and the number of pulses is the same. As shown in FIG. 15, the EUV light generation system 10A using the DL passing interval σ as an index has more stable EUV energy and less variation.

[0091] FIG. 16 is a graph showing the correlation between the DL passing interval σ and the EUV emission period. The horizontal axis of FIG. 16 represents the number of pulses of the generated EUV light, and the vertical axis represents the EUV emission period. F16A in FIG. 16 shows the case of the EUV light generation system 10 according to the comparative example, and F16B shows the case of the EUV light generation system 10A according to Embodiment 1, and the number of pulses is the same. As shown in FIG. 16, the EUV light generation system 10A using the DL passing interval σ as an index has a more stable EUV emission period and smaller variations.

[0092] FIG. 17 is a diagram numerically representing the relationship among the DL passing interval σ, EUV energy stability, and EUV emission period stability. Here, the values in the case of the EUV light generation system 10 according to the comparative example are set to 1, and each index of the EUV light generation system 10A according to Embodiment 1 is normalized. As shown in FIG. 17, the DL passing interval σ of Embodiment 1 is 0.12, and the EUV energy stability and EUV emission period stability are 0.56 and 0.08, respectively.

[0093] Thus, if the DL passing interval σ can be kept small, the EUV energy stability and the EUV emission interval can be maintained well. This is because when the DL passing interval σ is kept small, the relative position between the DL and the laser light is stabilized.

[0094] 3.4 Modification FIG. 18 is a flowchart showing an example of the DL coupling control subroutine according to the modification of Embodiment 1.

[0095] In the modification of Embodiment 1, instead of the Duty of Embodiment 1, the piezo voltage, which is the voltage for driving the piezo element 47, is manipulated. The piezo voltage may be the voltage amplitude of the rectangular wave applied to the piezo element 47. The Duty may be fixed to the operation Duty value obtained by the DL coupling adjustment. The piezo voltage is an example of the "vibration parameter" in the present disclosure.

[0096] In step S21, the target generation processor 36 reads the initial settings. As parameters for the initial settings, the search range ΔV may be 0.6 V, the search level N may be 3, and the improvement amount d of the piezo voltage may be 0.6 V. The initial value of the piezo voltage may be obtained in advance through experiments or the like, or a typical value may be selected from past operation data.

[0097] The processes of steps S51 to S53 are processes that are repeatedly performed. In step S51, the target generation processor 36 acquires the DL passage interval σ at the piezo voltage of the search level N centered on the current value, which is the currently set piezo voltage, and obtains the correlation between the piezo voltage and the DL passage interval σ. The intervals of the search level N are each the search range ΔV, and the order of the piezo voltages for acquiring the DL passage interval σ may be arbitrary. The current value of the piezo voltage is an example of the "first value" in the present disclosure.

[0098] In step S52, the target generation processor 36 calculates a linear approximation straight line with the piezo voltage on the horizontal axis and the DL passage interval σ on the vertical axis in the correlation between the piezo voltage and the DL passage interval σ acquired in step S51, and specifies the slope thereof.

[0099] In step S53, the target generation processor 36 changes the piezo voltage by d in the performance improvement direction based on the slope of the approximation straight line specified in step S52. The changed piezo voltage is an example of the "second value" in the present disclosure. The target generation processor 36 returns to step S51 and repeats the same process with the changed piezo voltage as the current value.

[0100] 4. Embodiment 2 4.1 Configuration FIG. 19 is a diagram schematically showing a configuration example of an EUV light generation system 10B according to Embodiment 2. The EUV light generation system 10B includes a temperature sensor 91 that measures the temperature of the piezo element 47. The temperature sensor 91 may be fixed to the piezo element 47. The EUV light generation system 10B may include a temperature adjustment unit that adjusts the temperature of the piezo element 47.

[0101] 4.2 Operation The operation of the EUV light generation system 10B of Embodiment 2 differs from the operation of the EUV light generation system 10A of Embodiment 1 only in the DL coupling control subroutine. That is, in Embodiment 2, as in Embodiment 1, DL coupling adjustment is performed before DL coupling control is implemented, and it is adjusted to an optimal operation Duty value.

[0102] FIG. 20 is a flowchart showing an example of the DL coupling control subroutine according to Embodiment 2. The DL coupling control of Embodiment 2 operates the piezo temperature, which is the temperature of the piezo element 47, instead of the Duty in the DL coupling control of Embodiment 1. The Duty may be fixed to the operation Duty value obtained by DL coupling adjustment. The piezo temperature is an example of a "vibration parameter".

[0103] In step S21, the target generation processor 36 reads the initial settings. As parameters for the initial settings, the search width ΔT may be 0.2 °C, the search level N may be 3, and the improvement amount d of the piezo temperature may be 0.2 °C. The initial value of the piezo temperature may be obtained in advance by experiments or the like, or a typical value may be selected from past operation data.

[0104] The processes of steps S61 to S63 are processes that are repeatedly performed. In step S61, the target generation processor 36 acquires the DL passage interval σ at the piezo temperature of the search level N centered on the current value, which is the currently set piezo temperature, and obtains the correlation between the piezo temperature and the DL passage interval σ. The intervals of the search level N are each the search width ΔT, and the order of the piezo temperatures for acquiring the DL passage interval σ may be arbitrary. The current value of the piezo temperature is an example of the "first value" in the present disclosure.

[0105] In step S62, the target generation processor 36 calculates a linear approximation straight line with the piezo temperature on the horizontal axis and the DL passage interval σ on the vertical axis in the correlation between the piezo temperature and the DL passage interval σ acquired in step S61, and specifies the slope thereof.

[0106] In step S63, based on the gradient of the approximate straight line identified in step S62, the target generation processor 36 changes the piezo temperature by an improvement amount d in the performance improvement direction. The changed piezo temperature is an example of the "second value" in the present disclosure. The target generation processor 36 returns to step S61 and repeats the same process with the changed piezo temperature as the current value.

[0107] 4.3 Operation and Effect According to the EUV light generation system 10B according to Embodiment 2, the temperature of the piezo element 47 can be optimized, and the DL passing interval σ can be reduced. Therefore, the relative irradiation position of the DL and the laser is stabilized, the EUV energy stability is improved, and the generation of fragments is also suppressed. Furthermore, the EUV emission cycle is stabilized.

[0108] 5. Embodiment 3 5.1 Configuration FIG. 21 is a diagram schematically showing a configuration example of an EUV light generation system 10C according to Embodiment 3. The EUV light generation system 10C includes a temperature sensor 92 that measures the temperature of the nozzle 42. The temperature sensor 92 may be fixed to the nozzle 42. The EUV light generation system 10C may include a temperature adjustment unit that adjusts the temperature of the nozzle 42.

[0109] 5.2 Operation The operation of the EUV light generation system 10C of Embodiment 3 is different only in the DL coupling control subroutine from the operation of the EUV light generation system 10A of Embodiment 1. That is, in Embodiment 3, similar to Embodiment 1, DL coupling adjustment is performed before the DL coupling control is implemented, and it is adjusted to the optimal operation Duty value.

[0110] FIG. 22 is a flowchart showing an example of the DL coupling control subroutine according to Embodiment 3. The DL coupling control of Embodiment 3 operates the nozzle temperature, which is the temperature of the nozzle 42, instead of the Duty in the DL coupling control of Embodiment 1. The Duty may be fixed to the operation Duty value obtained by the DL coupling adjustment. The nozzle temperature is an example of the "vibration parameter" in the present disclosure.

[0111] In step S21, the target generation processor 36 loads the initial settings. As parameters for the initial settings, the search width ΔTn may be 0.2°C, the search level N may be 3, and the improvement amount d of the nozzle temperature may be 0.2°C. The initial value of the nozzle temperature may be obtained in advance through experiments or the like, or a typical value may be selected from past operation data.

[0112] In step S71, the target generation processor 36 acquires the DL passing interval σ at the nozzle temperature of the search level N with the current value, which is the currently set nozzle temperature, as the center, and obtains the correlation between the nozzle temperature and the DL passing interval σ. The intervals of the search level N are each the search width ΔT, and the order of the nozzle temperatures for acquiring the DL passing interval σ may be arbitrary. The current value of the nozzle temperature is an example of the "first value" in the present disclosure.

[0113] In step S72, the target generation processor 36 calculates a linear approximation straight line with the nozzle temperature on the horizontal axis and the DL passing interval σ on the vertical axis in the correlation between the nozzle temperature and the DL passing interval σ acquired in step S71, and specifies its gradient.

[0114] In step S73, the target generation processor 36 changes the nozzle temperature by the improvement amount d in the performance improvement direction based on the gradient of the approximation straight line specified in step S72. The changed nozzle temperature is an example of the "second value" in the present disclosure. The target generation processor 36 returns to step S71 and repeats the same process with the changed nozzle temperature as the current value.

[0115] 5.3 Function and Effect According to the EUV light generation system 10C according to Embodiment 3, the temperature of the nozzle 42 can be optimized, and the DL passing interval σ can be reduced. Therefore, the relative irradiation position of the DL and the laser is stabilized, the EUV energy stability is improved, and the generation of fragments is also suppressed. Furthermore, the EUV emission cycle is stabilized.

[0116] 6. Method for Manufacturing an Electronic Device FIG. 23 is a diagram schematically showing the configuration of an exposure apparatus 660 connected to an EUV light generation system 10A. The exposure apparatus 660 includes a mask irradiation unit 668 and a workpiece irradiation unit 669. The mask irradiation unit 668 illuminates the reticle pattern on the reticle table MT through a reflective optical system with EUV light incident from the EUV light generation system 10A. The workpiece irradiation unit 669 forms an image of the EUV light reflected by the reticle table MT on a workpiece (not shown) disposed on the workpiece table WT through a reflective optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0117] The exposure apparatus 660 exposes the workpiece to EUV light reflecting the reticle pattern by synchronously translating the reticle table MT and the workpiece table WT in parallel. An electronic device can be manufactured by transferring a device pattern onto a semiconductor wafer through the exposure process as described above. Instead of the EUV light generation system 10A, an EUV light generation system 10B or an EUV light generation system 10C can be used.

[0118] FIG. 24 is a diagram schematically showing the configuration of an inspection apparatus 661 connected to an EUV light generation system 10A. The inspection apparatus 661 includes an illumination optical system 663 and a detection optical system 666. The illumination optical system 663 reflects the EUV light incident from the EUV light generation system 10A and irradiates the reticle 665 disposed on the reticle stage 664. The reticle 665 referred to here includes a mask blank before a pattern is formed. The detection optical system 666 reflects the EUV light from the illuminated reticle 665 and forms an image on the light receiving surface of the detector 667. The detector 667 that has received the EUV light acquires an image of the reticle 665. The detector 667 is, for example, a TDI (Time Delay Integration) camera.

[0119] Based on the image of the reticle 665 obtained through the inspection process as described above, defects in the reticle 665 are inspected. Using the inspection results, a reticle suitable for manufacturing an electronic device is selected. Then, an electronic device can be manufactured by exposing and transferring the pattern formed on the selected reticle onto a photosensitive substrate using the exposure apparatus 660. Regarding the configuration shown in FIG. 24, instead of the EUV light generation system 10A, the EUV light generation system 10B or the EUV light generation system 10C can be used.

[0120] 7. Others The above description is intended to be illustrative only and not limiting. Thus, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that the embodiments of the present disclosure can be used in combination.

[0121] The terms used throughout this specification and the claims should be construed as "non-limiting" terms unless otherwise specified. For example, terms such as "comprising," "having," "including," and "containing" should be construed as not excluding the presence of components other than those described. Also, the modifier "one" should be construed to mean "at least one" or "one or more." Also, the term "at least one of A, B, and C" should be construed as "A", "B", "C", "A + B", "A + C", "B + C", or "A + B + C". Furthermore, it should be construed to include combinations with things other than "A", "B", and "C".

Claims

1. An extreme ultraviolet light generation system that generates extreme ultraviolet light by irradiating a target material with a laser beam, a tank that houses a liquid target material, a nozzle that outputs the target material housed in the tank, a piezo element that vibrates the target material output from the nozzle to generate droplets of the target material, a droplet detection device that detects the time interval through which the droplets output from the nozzle pass, at least one processor, and comprising, wherein the processor obtains a first value of a vibration parameter related to the vibration of the piezo element, obtains the variation in the time interval corresponding to each of a plurality of values including the first value of the vibration parameter, and generates the droplets using a second value for which the variation in the time interval is smaller than the first value. An extreme ultraviolet light generation system.

2. The extreme ultraviolet light generation system according to claim 1, wherein the processor obtains at least the variation in the time interval corresponding to the first value of the vibration parameter, a value larger than the first value, and a value smaller than the first value of the vibration parameter. An extreme ultraviolet light generation system.

3. The extreme ultraviolet light generation system according to claim 1, wherein the processor calculates an approximate straight line in the correlation between the value of the vibration parameter and the variation in the time interval, and sets, as the second value, the value of the vibration parameter in the direction in which the variation in the time interval is smaller than the first value based on the slope of the approximate straight line. An extreme ultraviolet light generation system.

4. The extreme ultraviolet light generation system according to claim 1, wherein the vibration parameter is the duty of a rectangular voltage waveform that drives the piezo element. An extreme ultraviolet light generation system.

5. The extreme ultraviolet light generation system according to claim 1, wherein the vibration parameter is the voltage that drives the piezo element. An extreme ultraviolet light generation system.

6. The extreme ultraviolet light generation system according to claim 1, wherein the vibration parameter is the temperature of the piezo element. An extreme ultraviolet light generation system.

7. The extreme ultraviolet light generation system according to claim 1, wherein the vibration parameter is the temperature of the nozzle. An extreme ultraviolet light generation system.

8. The extreme ultraviolet light generation system according to claim 1, wherein the processor Drive the piezoelectric element with a rectangular-wave voltage waveform of the duty value of the operation duty to generate the droplet, Irradiate the droplet with the laser light to generate extreme ultraviolet light, Extreme ultraviolet light generation system.

9. The extreme ultraviolet light generation system according to claim 8, wherein the processor, obtains the correlation between the duty of the rectangular wave and the variation of the time interval, sets the value of the duty at which the variation of the time interval is minimized as the value of the operation duty, Extreme ultraviolet light generation system.

10. The extreme ultraviolet light generation system according to claim 9, wherein the processor, sets the value of the operation duty as the second value, Extreme ultraviolet light generation system.

11. The extreme ultraviolet light generation system according to claim 1, wherein the target substance is a liquid target substance containing tin, Extreme ultraviolet light generation system.

12. The extreme ultraviolet light generation system according to claim 11, wherein the processor melts the tin at a predetermined temperature in the target supply unit including the tank, Extreme ultraviolet light generation system.

13. The extreme ultraviolet light generation system according to claim 11, wherein the processor controls the pressure of the inert gas supplied to the tank by a pressure regulator and outputs the liquid tin inside the tank to the outside through the nozzle, Extreme ultraviolet light generation system.

14. The extreme ultraviolet light generation system according to claim 1, wherein the piezoelectric element is driven with the second value of the vibration parameter to generate the droplet, Extreme ultraviolet light generation system.

15. The extreme ultraviolet light generation system according to claim 1, wherein the piezoelectric element is driven by a rectangular wave of a duty value at which the variation of the time interval is less than a threshold value, Extreme ultraviolet light generation system.

16. The extreme ultraviolet light generation system according to claim 1, wherein control is performed to maintain the bonding state of the droplet by finely adjusting the duty value of the piezoelectric element, Extreme ultraviolet light generation system.

17. The extreme ultraviolet light generation system according to claim 1, wherein the energy stability of the extreme ultraviolet light is improved by keeping the variation of the time interval small, Extreme ultraviolet light generation system.

18. The extreme ultraviolet light generation system according to claim 1, wherein the bonding state of the droplet is controlled using the variation of the time interval as an index, Extreme ultraviolet light generation system.

19. A method for manufacturing an electronic device, comprising: a tank for containing a liquid target substance; a nozzle for outputting the target substance contained in the tank; a piezo element for vibrating the target substance output from the nozzle to generate droplets of the target substance; a droplet detection device for detecting the time interval through which the droplets output from the nozzle pass; at least one processor; and the processor obtains a first value of a vibration parameter related to the vibration of the piezo element; obtains the variation of the time interval corresponding to each of a plurality of values including the first value of the vibration parameter; generates the droplets using a second value for which the variation of the time interval is smaller than the first value; generates the extreme ultraviolet light by an extreme ultraviolet light generation system that irradiates a target substance with a laser beam to generate extreme ultraviolet light; outputs the extreme ultraviolet light to an exposure apparatus; and includes exposing the extreme ultraviolet light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device. A method for manufacturing an electronic device.

20. A method for manufacturing an electronic device, comprising: a tank for containing a liquid target substance; a nozzle for outputting the target substance contained in the tank; a piezo element for vibrating the target substance output from the nozzle to generate droplets of the target substance; a droplet detection device for detecting the time interval through which the droplets output from the nozzle pass; at least one processor; and the processor obtains a first value of a vibration parameter related to the vibration of the piezo element; obtains the variation of the time interval corresponding to each of a plurality of values including the first value of the vibration parameter; generates the droplets using a second value for which the variation of the time interval is smaller than the first value; generates the extreme ultraviolet light by an extreme ultraviolet light generation system that irradiates a target substance with a laser beam to generate extreme ultraviolet light; irradiates the extreme ultraviolet light onto a reticle to inspect for defects in the reticle; selects a reticle using the result of the inspection; and includes exposing and transferring a pattern formed on the selected reticle onto a photosensitive substrate. A method for manufacturing an electronic device.

Images