Laser apparatus, laser oscillation method, and manufacturing method of electronic device

Abstract

A laser device according to an aspect disclosed herein comprises a master oscillator that outputs a pulse laser beam at a first discharge timing synchronized with a repetition frequency, an amplifier that amplifies the pulse laser beam by exciting, at a second discharge timing, a laser medium through which the pulse laser beam passes, and a processor that sets the second discharge timing by adding a delay time to the first discharge timing, wherein the processor holds a first value as a command value of the delay time corresponding to a first repetition frequency, holds a second value as a command value of the delay time corresponding to a second repetition frequency different from the first repetition frequency; and outputs the command value of the second value after outputting a command value of a third value between the first value and the second value when the repetition frequency changes from the first repetition frequency to the second repetition frequency.

Description

[Technical field]

[0001] The present disclosure relates to a laser apparatus, a laser oscillation method, and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, in semiconductor exposure devices, there is a demand for improved resolution as semiconductor integrated circuits become finer and more highly integrated. For this reason, the wavelength of light emitted from exposure light sources is becoming shorter. For example, as gas laser devices for exposure, KrF excimer laser devices that output laser light with a wavelength of about 248 nm and ArF excimer laser devices that output laser light with a wavelength of about 193 nm are used.

[0003] The spectral line width of the spontaneous oscillation light of the KrF excimer laser device and the ArF excimer laser device is as wide as 350 to 400 pm. Therefore, if a projection lens is made of a material that transmits ultraviolet light such as KrF and ArF laser light, chromatic aberration may occur. As a result, the resolution may decrease. Therefore, it is necessary to narrow the spectral line width of the laser light output from the gas laser device to a level where the chromatic aberration can be ignored. Therefore, in order to narrow the spectral line width, a line narrow module (LNM) including a line narrowing element (such as an etalon or grating) may be provided in the laser resonator of the gas laser device. Hereinafter, a gas laser device in which the spectral line width is narrowed is referred to as a line narrowing gas laser device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 7,903,700 [Patent Document 2] Summary of JP2012-44098A

[0005] A laser device according to one aspect of the present disclosure includes a master oscillator that outputs pulsed laser light at a first discharge timing synchronized with a repetition frequency, an amplifier that amplifies the pulsed laser light by exciting a laser medium through which the pulsed laser light passes at a second discharge timing, and a processor that sets a second discharge timing by adding a delay time to the first discharge timing, the processor holding a first value as a command value for the delay time corresponding to the first repetition frequency, holding a second value as a command value for the delay time corresponding to a second repetition frequency different from the first repetition frequency, and when the repetition frequency is changed from the first repetition frequency to the second repetition frequency after outputting the command value of the first value, outputting a command value of a third value between the first value and the second value, and then outputting a command value of the second value.

[0006] A laser oscillation method according to another aspect of the present disclosure includes outputting a pulsed laser beam from a master oscillator at a first discharge timing synchronized with a repetition frequency, amplifying the pulsed laser beam by exciting a laser medium of an amplifier through which the pulsed laser beam passes at a second discharge timing, and setting a second discharge timing by a processor by adding a delay time to the first discharge timing, wherein the processor holds a first value as a command value for a delay time corresponding to the first repetition frequency, holds a second value as a command value for a delay time corresponding to a second repetition frequency different from the first repetition frequency, and when the repetition frequency is changed from the first repetition frequency to the second repetition frequency after outputting the command value of the first value, outputs a command value for a third value between the first value and the second value, and then outputs a command value for the second value.

[0007] According to another aspect of the present disclosure, a method for manufacturing an electronic device includes generating laser light using a laser apparatus including: a master oscillator that outputs pulsed laser light at a first discharge timing synchronized with a repetition frequency; an amplifier that amplifies the pulsed laser light by exciting a laser medium through which the pulsed laser light passes at a second discharge timing; and a processor that sets a second discharge timing by adding a delay time to the first discharge timing, the processor holding a first value as a command value for the delay time corresponding to the first repetition frequency, holding a second value as a command value for the delay time corresponding to a second repetition frequency different from the first repetition frequency, and outputting a command value for a third value between the first value and the second value and then outputting a command value for the second value when the repetition frequency is changed from the first repetition frequency to the second repetition frequency after outputting the command value for the first value; outputting the laser light to an exposure apparatus; and exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device. [Brief description 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. [Figure 1] FIG. 1 shows a schematic configuration example of a laser device. [Diagram 2] FIG. 2 is an example of a graph showing the relationship between repetition frequency and spectral width. [Diagram 3] FIG. 3 is an example of a graph showing the relationship between the delay time between the MO (Master Oscillator) discharge timing and the PO (Power Oscillator) discharge timing, and the spectrum width and pulse energy. [Figure 4] FIG. 4 is an example of a table that defines the correspondence between the repetition frequency and the amount of change in delay time. [Diagram 5] FIG. 5 is an example of a graph showing the relationship between the MO charging voltage and / or the PO charging voltage and the pulse energy. [Figure 6] FIG. 6 is an example of a graph showing the operation of the laser device when the control of Comparative Example 1 is applied. [Figure 7] FIG. 7 is an example of a graph showing the operation of a laser device when the control of Comparative Example 2 including the compensation control of the spectral width using the characteristic shown in FIG. 3 is applied. [Figure 8] FIG. 8 is an example of a graph showing the operation of the laser device according to the first embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of control of the delay time in the laser apparatus according to the first embodiment. [Figure 10] FIG. 10 is an example of a graph showing the relationship between the delay time change rate and the spectrum width deviation and energy stability, and shows an example of a case in which the delay time change rate can be set so that the spectrum width deviation and energy stability satisfy their respective allowable values. [Figure 11] FIG. 11 is an example of a graph showing the relationship between the delay time change rate and the spectrum width deviation and energy stability, and shows an example of a case where the delay time change rate cannot be set so that both the spectrum width deviation and energy stability satisfy the allowable values. [Figure 12] FIG. 12 shows a schematic configuration example of an exposure apparatus. Embodiment

[0009] -table of contents- 1. Overview of the laser device 1.1 Configuration 1.2 Operation 1.3 Characteristics of narrow-band lasers 1.4 Control when changing repetition rate 2. Challenges 3. Embodiment 1 3.1 Configuration 3.2 Operation 3.3 Actions and Effects 4. Embodiment 2 4.1 Configuration 4.2 Operation 4.3 Actions and Effects 5. Embodiment 3 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 6.Other Applications 7. Manufacturing methods for electronic devices 8.Other Hereinafter, the 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 contents 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 duplicated explanations will be omitted.

[0010] 1. Overview of the laser device 1.1 Configuration 1 shows a schematic configuration example of a laser device 1. The laser device 1 is an excimer laser device including a master oscillator (MO) 10, a power oscillator (PO) 20, a laser control unit 30, and an energy control unit 32. The laser device 1 may also include high-reflection mirrors 41 and 42, a beam measuring instrument 50, a wavelength control unit 60, and a wavelength tuning unit 62.

[0011] The master oscillator 10 includes a line narrowing module (LNM) 12, an MO chamber 13, an MO output coupling mirror 14, an MO pulsed power module (PPM) 15, and an MO charger 16. The LNM 12 includes a prism 122 for narrowing the spectral width, and a grating 124. The grating 124 is arranged in a Littrow arrangement so that the angle of incidence and the angle of diffraction match.

[0012] The MO output coupling mirror 14 may be, for example, a partial reflection mirror with a reflectance of 20% to 30%. The MO output coupling mirror 14 is disposed so as to configure an optical resonator together with the LNM 12.

[0013] The MO chamber 13 is disposed on the optical path of the optical resonator. The MO chamber 13 includes a pair of discharge electrodes 132, 133, and two windows 134, 136 through which the laser light passes. A laser gas is supplied into the MO chamber 13 from a gas supply device (not shown). The laser gas is an excimer laser gas including a rare gas, a halogen gas, and a buffer gas. The rare gas may be, for example, argon (Ar) or krypton (Kr) gas. The halogen gas may be, for example, fluorine (F2) gas. The buffer gas may be, for example, neon (Ne) gas.

[0014] The MO pulsed power module 15 includes a switch 152 and a charging capacitor (not shown), and is connected to the discharge electrode 132 via a feedthrough of an electrical insulating member (not shown). The discharge electrode 133 is connected to the grounded MO chamber 13. The MO charger 16 charges the charging capacitor of the MO pulsed power module 15 according to a command from the energy control unit 32.

[0015] The master oscillator 10 includes a beam splitter 17 and an MO pulse energy measuring instrument 18. The beam splitter 17 is disposed on the optical path of the laser light output from the MO output coupling mirror 14. The beam splitter 17 is disposed so that the reflected light of the beam splitter 17 is incident on the MO pulse energy measuring instrument 18. The MO pulse energy measuring instrument 18 includes a condenser lens and an optical sensor (not shown). The optical sensor may be a high-speed response photodiode that is resistant to ultraviolet light. A signal line is provided between the MO pulse energy measuring instrument 18 and the energy control unit 32 to transmit information obtained by the MO pulse energy measuring instrument 18 to the energy control unit 32.

[0016] The pulsed laser light transmitted through the beam splitter 17 is output from the master oscillator 10 .

[0017] The high-reflection mirror 41 and the high-reflection mirror 42 are disposed on the optical path between the master oscillator 10 and the power oscillator 20 so that the laser light output from the master oscillator 10 is incident on the power oscillator 20 .

[0018] Power oscillator 20 is an excimer amplifier that includes a rear mirror 22 , a PO chamber 23 , a PO output coupling mirror 24 , a PO pulsed power module 25 , a PO charger 26 , and a monitor module 27 .

[0019] The rear mirror 22 and the PO output coupling mirror 24 form an optical resonator, and the PO chamber 23 is disposed on the optical path of this optical resonator.

[0020] The configuration of the PO chamber 23 may be similar to that of the MO chamber 13. The PO chamber 23 includes a pair of discharge electrodes 232, 233 and two windows 234, 236. Laser gas is supplied into the PO chamber 23 in the same manner as the MO chamber 13. The rear mirror 22 may be, for example, a partial reflection mirror with a reflectance of 80% to 90%. The PO output coupling mirror 24 may be, for example, a partial reflection mirror with a reflectance of 20% to 30%.

[0021] The PO pulse power module 25 includes a switch 252 and a charging capacitor (not shown), and is connected to the discharge electrode 232 via a feedthrough of an electrical insulating member (not shown). The discharge electrode 233 is connected to the grounded PO chamber 23. The PO charger 26 charges the charging capacitor of the PO pulse power module 25 according to a command from the energy control unit 32.

[0022] In Fig. 1, the optical path axis direction of the laser light output from the power oscillator 20 is the z direction. Two directions substantially perpendicular to the z direction may be the h direction and the v direction. The v direction is a direction substantially perpendicular to the paper surface of Fig. 1. The discharge electrodes 232 and 233 are disposed opposite to each other in the h direction.

[0023] The monitor module 27 includes beam splitters 271 and 272 , a PO pulse energy measuring instrument 274 , and a spectrum measuring instrument 276 .

[0024] The beam splitter 271 is disposed on the optical path of the pulsed laser beam output from the PO output coupling mirror 24. The beam splitter 272 is disposed on the optical path of the pulsed laser beam reflected by the beam splitter 271. The beam splitter 272 is disposed so that the reflected light of the beam splitter 272 enters a PO pulse energy measuring instrument 274 and the transmitted light of the beam splitter 272 enters a spectrometer 276. The configuration of the PO pulse energy measuring instrument 274 may be similar to that of the MO pulse energy measuring instrument 18.

[0025] Between the PO pulse energy measuring device 274 and the energy control unit 32, a signal line is provided for transmitting information obtained by the PO pulse energy measuring device 274 to the energy control unit 32.

[0026] The spectrum measuring instrument 276 may be, for example, an etalon spectrometer including an etalon (not shown), a condenser lens, and an image sensor. The interference fringes that are transmitted through the etalon and generated on the focal plane by the condenser lens are measured using the image sensor. A signal line is provided between the spectrum measuring instrument 276 and the wavelength control unit 60 to transmit information obtained by the spectrum measuring instrument 276 to the wavelength control unit 60.

[0027] The beam measurement instrument 50 includes a beam splitter 51, a polarization measurement instrument 52, a beam pointing measurement instrument 54, and a beam profiler 56. The beam splitter 51 is disposed on the optical path of the pulsed laser light transmitted through the beam splitter 271 of the monitor module 27.

[0028] The beam splitter 51 is disposed so that reflected light from the beam splitter 51 enters each of the polarization measuring instrument 52, the beam pointing measuring instrument 54, and the beam profiler 56 via optical elements not shown, and transmitted light from the beam splitter 51 enters the exposure device 70. A signal line is provided between the beam measuring instrument 50 and the laser control unit 30 to transmit beam-related data obtained by the beam measuring instrument 50 to the laser control unit 30.

[0029] The laser control unit 30 is connected to the energy control unit 32 and the wavelength control unit 60. The energy control unit 32 is connected to the master oscillator 10 and the power oscillator 20. The energy control unit 32 transmits charging voltage data to the MO charger 16 based on the pulse energy detected by the MO pulse energy measuring instrument 18, and controls the voltage to be charged to the charging capacitor of the MO pulse power module 15. The energy control unit 32 also transmits charging voltage data to the PO charger 26 based on the pulse energy detected by the PO pulse energy measuring instrument 274, and controls the voltage to be charged to the charging capacitor of the PO pulse power module 25.

[0030] The wavelength control unit 60 generates wavelength control related data based on the data obtained by the spectrometer 276, and transmits the wavelength control related data to the laser control unit 30. The wavelength control unit 60 is connected to a wavelength tuning unit 62. The wavelength tuning unit 62 includes a rotation drive mechanism such as a rotation stage that rotates the prism 122 of the LNM 12. The wavelength tuning unit 62 is controlled based on the wavelength measured by the spectrometer 276.

[0031] Furthermore, the laser control unit 30 is connected to the beam measurement device 50 and the exposure apparatus 70. The exposure apparatus 70 includes an exposure apparatus controller 72.

[0032] The laser control unit 30, the energy control unit 32, the wavelength control unit 60, the exposure apparatus controller 72, and each of the other control units are configured using at least one processor. The processor in this disclosure is a processing device including a storage device in which a control program is stored, and a CPU (Central Processing Unit) that executes the control program. The processor is specially configured or programmed to execute various processes included in this disclosure. The processor may include an integrated circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0033] The laser control unit 30, the energy control unit 32, and the wavelength control unit 60 may each be realized by a separate processor, or the processing functions of a plurality of control units may be realized by a single processor.

[0034] 1.2 Operation The laser control unit 30 receives a light emission trigger signal and / or target data from the exposure device 70. The target data may be a target pulse energy and / or a charging voltage command value. The laser control unit 30 outputs a light emission trigger signal and a target pulse energy and / or a charging voltage command value to the energy control unit 32.

[0035] The energy control unit 32 may determine the MO charging voltage and / or the PO charging voltage based on the target pulse energy and / or the charging voltage command value. The energy control unit 32 outputs a first trigger signal synchronized with the light emission trigger signal and the MO charging voltage to the master oscillator 10. The first trigger signal is a signal that specifies the MO charging timing. The master oscillator 10 may output a seed laser beam in synchronization with the first trigger signal. The seed laser beam output by the master oscillator 10 is narrowbanded.

[0036] The seed laser light output from the master oscillator 10 can be incident on the power oscillator 20 via high-reflection mirrors 41 and 42 .

[0037] The energy control unit 32 outputs a second trigger signal synchronized with the light emission trigger signal and a PO charging voltage to the power oscillator 20. The second trigger signal is generated to have a delay time with respect to the first trigger signal. The second trigger signal is a signal that specifies the PO discharge timing. The PO discharge timing is a timing obtained by adding a delay time to the MO discharge timing. The power oscillator 20 can form a discharge region in synchronization with the second trigger signal. The seed laser light incident on the power oscillator 20 is amplified by passing through the discharge region of the PO chamber 23. The power oscillator 20 can amplify the incident seed laser light by the discharge region and output an output laser light.

[0038] 1.3 Characteristics of narrow-band lasers The characteristics of the output laser light output from the power oscillator 20 change depending on the repetition frequency. FIG. 2 is an example of a graph showing the relationship between the repetition frequency and the spectral width. For example, as shown in FIG. 2, the spectral width changes in a complex manner with respect to the repetition frequency. Therefore, when the repetition frequency changes from a nominal value RR0 to a certain value RR, the spectral width changes by ΔBW. In addition, the characteristics of the output laser light output from the power oscillator 20 change depending on the delay time D between the MO discharge timing and the PO discharge timing.

[0039] FIG. 3 is an example of a graph showing the relationship between the delay time D between the MO discharge timing and the PO discharge timing, and the spectral width and pulse energy. The horizontal axis of FIG. 3 represents the delay time D, the left vertical axis of FIG. 3 represents the spectral width, and the right vertical axis of FIG. 3 represents the pulse energy. Graph G1 shown by a solid line in FIG. 3 shows the relationship between the delay time D and the spectral width. Graph G2 shown by a dashed line in FIG. 3 shows the relationship between the delay time D and the pulse energy. As shown in FIG. 3, for example, the spectral width becomes smaller as the delay time D increases. Also, the pulse energy has a maximum value with respect to the delay time D. The laser device 1 operates with the delay time D at which this maximum value is reached as the nominal value Dt.

[0040] When changing the repetition frequency from RR0 to RR, the laser control unit 30 corrects the change amount ΔBW of the spectrum width that occurs when changing the repetition frequency by using the characteristics shown in Fig. 3. That is, ΔBW at a certain repetition frequency RR can be known from the characteristics shown in Fig. 2. Also, from the characteristics shown in Fig. 3, it can be seen that in order to cancel or reduce ΔBW, it is necessary to change the delay time D from the nominal value Dt by the delay time change amount ΔD.

[0041] As a result, a table that associates the repetition frequency RR with the delay time change amount ΔD is obtained, as shown in Fig. 4. The laser device 1 holds the data of this table.

[0042] On the other hand, the characteristics of the output laser light also change depending on the MO charging voltage and / or the PO charging voltage, and the pulse energy shows the characteristics as shown in Fig. 5. The characteristics shown in Fig. 5 are used to stabilize the pulse energy. For example, when outputting laser light to the exposure device 70, the pulse energy is feedback-controlled and stabilized within a target range by adjusting the MO charging voltage and / or the PO charging voltage. This is called HV control.

[0043] When the repetition rate is changed from RR0 to RR, if the delay time D is changed by ΔD to maintain the spectral width, the pulse energy fluctuates by ΔE (Figure 3). HV control works to compensate for this energy fluctuation.

[0044] 1.4 Control when changing repetition rate 6 is an example of a graph showing the operation of the laser device 1 when the control of Comparative Example 1 is applied. The Comparative Example of the present disclosure is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant recognizes.

[0045] In Fig. 6, from the top, graphs G6A to G6E showing the transition of the parameter values ​​of repetition frequency, delay time D, spectrum width, pulse energy, and charging voltage are shown on a common time axis. The charging voltage here may be the MO charging voltage, the PO charging voltage, or a combination of the MO charging voltage and the PO charging voltage. In Figs. 6 to 8, the charging voltage will be described as the PO charging voltage.

[0046] The exposure device 70 may instruct the laser device 1 to change the repetition frequency in order to adjust the amount of exposure (graph G6A).

[0047] When the repetition rate is changed, the spectral width may deviate from the predetermined tolerance range (graph G6C) due to the characteristics shown in Fig. 2. Note that the range of the spectral width indicated by the dashed line in graph G6C represents the predetermined tolerance range.

[0048] Fig. 7 is an example of a graph showing the operation of the laser device 1 when the control of Comparative Example 2 is applied, including the compensation control of the spectral width using the characteristic shown in Fig. 3. In Fig. 7, similar to Fig. 6, from the top, graphs G7A to G7E showing the transition of the values ​​of each parameter of the repetition frequency, the delay time D, the spectral width, the pulse energy, and the charging voltage are shown on a common time axis.

[0049] In the case of comparative example 2, the laser control unit 30 determines a delay time change amount ΔD corresponding to the changed repetition frequency RR from the data in the table shown in FIG. 4, and changes the delay time D between the MO discharge timing and the PO discharge timing by ΔD (graph G6B in FIG. 6 → graph G7B in FIG. 7).

[0050] This can suppress the variation of the spectrum width accompanying the change of the repetition frequency, as shown in graph G7C. On the other hand, when the delay time D is changed, the pulse energy also changes due to the characteristics shown in FIG. 3. As a result, the pulse energy may deviate from the target range in some cases (graph G7D). The range of the pulse energy shown by the dashed line in graph G7D represents the target range. In order to suppress such deviation of the pulse energy from the target range, the laser control unit 30 performs HV control based on the characteristics in FIG. 5. That is, the laser control unit 30 adjusts the charging voltage, as shown in graph G7E in FIG. 7. This causes the pulse energy to return to the target range (graph G7D).

[0051] However, as shown in the time range (period) indicated by the dashed line on the time axis of graph G7D, pulses may be generated with pulse energy outside the target range until HV control settles (graph G7D).

[0052] 2. Challenges If the delay time D is changed suddenly, it takes time for the HV control to settle. As a result, as explained in FIG. 7, a time period may occur during which laser light with a pulse energy outside the target range is output. During this time period, energy stability and dose stability may deteriorate. Here, the explanation has been given using a change in repetition frequency as an example, but this is not the only example, and similar issues arise when changing the delay time D even when changing other operating conditions.

[0053] 3. Embodiment 1 3.1 Configuration The configuration of the laser device 1 according to the first embodiment may be similar to that shown in FIG.

[0054] 3.2 Operation Fig. 8 is an example of a graph showing the operation of the laser device 1 according to the embodiment 1. In Fig. 8, similarly to Fig. 6, from the top, graphs G8A to G8E showing the transition of the values ​​of each parameter, namely, the repetition frequency, the delay time D, the spectral width, the pulse energy, and the charging voltage, are shown on a common time axis.

[0055] When the repetition frequency is changed, the laser control unit 30 changes the delay time D between the MO discharge timing and the PO discharge timing. At this time, the delay time D is gradually changed over multiple pulses at a rate of delay time change Δd (ns / pls) per pulse until the change amount of the delay time D reaches a target delay time change amount ΔD corresponding to the repetition frequency RR. The delay time change rate Δd is the amount of change per pulse when changing the delay time D. The delay time change rate Δd may be constant throughout the period of multiple pulses over which the delay time D is changed.

[0056] The MO discharge timing is an example of a "first discharge timing" in the present disclosure, and the PO discharge timing is an example of a "second discharge timing" in the present disclosure. The power oscillator 20 is an example of an "amplifier" in the present disclosure, and the laser gas contained in the PO chamber 23 is an example of a "laser medium" in the present disclosure.

[0057] Of the repetition frequencies for 10 pulses shown in graph G8A of Fig. 8, the repetition frequency of the first five pulses corresponds to RR0, and the repetition frequency of the last five pulses corresponds to RR. As specific numerical values, for example, RR0 may be 6.0 kHz, and RR may be 5.3 kHz. RR0 is an example of a "first repetition frequency" in the present disclosure, and RR is an example of a "second repetition frequency" in the present disclosure.

[0058] Moreover, the command value of the delay time D of the first five pulses shown in graph G8B of FIG. 8 is an example of the "first value" in the present disclosure, and the command values ​​of the delay time D of the 9th pulse and the 10th pulse are an example of the "second value" in the present disclosure. The command values ​​of the delay time D of the 6th pulse, the 7th pulse, and the 8th pulse in graph G8B of FIG. 8 are an example of the "third value" in the present disclosure. The command values ​​of the delay time D of the 6th pulse, the 7th pulse, and the 8th pulse are between the command value of the 5th pulse and the command value of the 9th pulse. The charging voltage shown in graph G8E of FIG. 8 is an example of the "excitation voltage" in the present disclosure.

[0059] Fig. 9 is a flowchart showing an example of control of the delay time D in the laser device 1 according to embodiment 1. The flowchart in Fig. 9 can be realized by a processor functioning as the laser control unit 30 executing a program.

[0060] In step S11, the laser control unit 30 determines whether or not the repetition frequency has been changed. If the repetition frequency has been changed and the determination result in step S11 is True, the process proceeds to step S12.

[0061] In step S12, the laser control unit 30 updates the delay time change amount ΔD as a target value of the change amount of the delay time D from a table. This table may be a table as described in FIG. 4. Alternatively, the laser control unit 30 may store table data indicating a correspondence relationship between the repetition frequency and an appropriate command value of the delay time D, and determine the target delay time change amount ΔD based on this table data. The difference between the command value of the delay time D corresponding to the repetition frequency after the change and the command value of the delay time D corresponding to the repetition frequency before the change can be the target delay time change amount ΔD.

[0062] Next, in step S13, the laser control unit 30 determines whether the current delay time D does not match Dt+ΔD. If the current delay time D does not match Dt+ΔD and the determination result in step S13 is True, the process proceeds to step S14.

[0063] In step S14, the laser control unit 30 determines whether the current delay time D is smaller than Dt+ΔD. If the current delay time D is smaller than Dt+ΔD and the determination result in step S14 is True, the process proceeds to step S16.

[0064] In step S16, the laser control unit 30 adds Δd to the delay time D to update the current value of the delay time D. The delay time change rate Δd when changing the delay time D may be determined in advance based on experimental data, for example, or may be determined according to a target delay time change amount ΔD. It is desirable that the delay time change rate Δd is set to a value that causes the variation of the spectral width to be within a predetermined allowable range and causes the pulse energy to be within a target range.

[0065] On the other hand, if it is determined in step S14 that the current delay time D is greater than Dt+ΔD, and the determination result in step S14 is a False determination, the process proceeds to step S17.

[0066] In step S17, the laser control unit 30 subtracts Δd from the delay time D to update the current value of the delay time D.

[0067] After step S16 or step S17, the laser control unit 30 ends the flowchart of Fig. 9. Also, in the judgment of step S11, if the repetition frequency has not been changed and the judgment result of step S11 is False, the laser control unit 30 ends the flowchart of Fig. 9. Also, in the judgment of step S13, if the current delay time D matches Dt+ΔD and the judgment result of step S13 is False, the laser control unit 30 ends the flowchart of Fig. 9.

[0068] The laser control unit 30 can repeatedly execute the process of the flowchart in FIG. 9 for each pulse.

[0069] The MOPO type laser oscillation method realized by the flowchart in FIG. 9 is an example of the "laser oscillation method" in this disclosure.

[0070] 3.3 Actions and Effects According to the laser device 1 of the first embodiment, when changing the repetition frequency, the delay time D is gradually changed over multiple pulses to the target delay time change amount ΔD, so that the change in pulse energy accompanying the change in delay time D becomes gentle, and deviation from the target range is suppressed (graph G8D in FIG. 8). As a result, deterioration of energy stability and dose stability is suppressed.

[0071] 4. Embodiment 2 4.1 Configuration The configuration of the laser device 1 according to the second embodiment may be similar to that shown in FIG.

[0072] 4.2 Operation The operation of the second embodiment will be described in terms of differences from the first embodiment. In the second embodiment, in the operation described in the first embodiment, the amount of change per pulse (the rate of change of delay time Δd) that is constant throughout the period of change of the delay time D over a plurality of pulses is determined based on the characteristics of the laser device 1. A detailed example will be described below.

[0073] 10 is an example of a graph showing the relationship between the delay time change rate Δd and the spectral width deviation and energy stability. The horizontal axis represents the delay time change rate Δd, the left vertical axis represents the spectral width deviation, and the right vertical axis represents the energy stability.

[0074] 10, Δd=0 corresponds to the case where the delay time D is not changed (as in FIG. 6), and Δd=ΔD corresponds to the case where the delay time D is changed all at once (as in FIG. 7).

[0075] The spectral width deviation indicates the magnitude of deviation between the average value of the spectral width and the target value. The energy stability is an index of the variation in the pulse energy value, and a smaller value indicates higher stability.

[0076] When the delay time change rate Δd is reduced, the change in pulse energy due to the delay time change becomes gentler, and the energy stability improves (the index value of energy stability becomes smaller). On the other hand, the drive of the spectral width due to the delay time change becomes slower, and the suppression of the fluctuation of the spectral width accompanying the switching of the repetition frequency becomes insufficient. Therefore, the fluctuation of the spectral width becomes larger, and the value of the spectral width deviation becomes larger.

[0077] It is preferable to obtain the characteristics shown in Fig. 10 in advance and select the delay time change rate Δd so that both the spectrum width deviation and the energy stability satisfy their respective tolerances. Alternatively, as shown in Fig. 11, when it is not possible to achieve both the spectrum width deviation and the energy stability, the delay time change rate Δd may be selected so that the spectrum width is improved as much as possible within the range in which the energy stability satisfies the tolerance (typically 1 ns / pls).

[0078] In this case, the spectral width deviation does not satisfy the tolerance by this method alone, but the shortfall may be compensated for by a spectral width control means (not shown). For example, the spectral width control mechanism may change the wavefront in the MO resonator to change the spectral width.

[0079] Other operations may be similar to those in the first embodiment.

[0080] 4.3 Actions and Effects According to the laser device 1 of the second embodiment, similarly to the first embodiment, the change in pulse energy accompanying the change in delay time D becomes gentle, and deviation from the target range is suppressed.

[0081] By determining the delay time change rate Δd according to operating conditions such as repetition frequency and / or laser light characteristics, it is possible to prevent the change in pulse energy from being sufficiently gradual and deviating from the target range, or from being unnecessarily gradual and reducing responsiveness.

[0082] 5. Embodiment 3 5.1 Configuration The configuration of the laser device 1 according to the third embodiment may be similar to that shown in FIG.

[0083] 5.2 Operation The operation of the third embodiment will be described in terms of differences from the first embodiment. In the third embodiment, the rate of change of delay time Δd in the operation described in the first embodiment is dynamically (adaptively) set according to the target value ΔD of the delay time change amount. That is, the rate of change of delay time Δd in the third embodiment is set so that the delay time change amount reaches the target value ΔD within a predetermined number of pulses N (for example, N=5 pls). For example, Δd=ΔD / N is set so that ΔD is reached with N pulses. The predetermined number of pulses N may be set to a value of, for example, 2 pulses or more and 10 pulses or less. Other operations may be the same as those of the first embodiment.

[0084] 5.3 Actions and Effects According to the laser device 1 of the third embodiment, as in the first embodiment, the change in pulse energy accompanying the change in the delay time D becomes gentle, and deviation from the target range is suppressed. Also, according to the laser device 1 of the third embodiment, it is guaranteed that the change in the delay time D ends after a predetermined number of pulses N has elapsed. Therefore, the third embodiment is useful in cases where the period from the start of oscillation to N pulses is not to be evaluated for the spectral width, for example.

[0085] 6.Other Applications In the above-mentioned first to third embodiments, the repetition frequency is changed as an example, but other operating conditions may be changed. Also, the spectral width is an example of a laser light characteristic, and the delay time D may be changed to suppress fluctuations in other characteristics. The laser control technology according to the present disclosure can be applied to a control for "reducing changes (fluctuations) in the laser light characteristics by changing the delay time D according to the operating conditions." When changing the delay time D according to changes in the operating conditions, the delay time D is gradually changed over multiple pulses, thereby suppressing deviation of the laser light characteristics from the target range.

[0086] 7. Manufacturing methods for electronic devices 12 shows a schematic configuration example of an exposure apparatus 70. The exposure apparatus 70 includes an illumination optical system 74 and a projection optical system 76. The illumination optical system 74 illuminates a reticle pattern of a reticle (not shown) arranged on a reticle stage RT with laser light incident from the laser device 1. The projection optical system 76 reduces and projects the laser light transmitted through the reticle to form an image on a workpiece (not shown) arranged on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0087] The exposure apparatus 70 exposes the workpiece to laser light reflecting the reticle pattern by synchronously translating the reticle stage RT and the workpiece table WT. After the reticle pattern is transferred to the semiconductor wafer by the exposure process described above, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in this disclosure.

[0088] 8.Other The above description is intended to be illustrative rather than restrictive. Thus, it will be apparent to one skilled in the art that modifications may 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 may be used in combination.

[0089] Terms used throughout the present specification and claims should be interpreted as "open ended" terms unless otherwise specified. For example, terms such as "include," "have," "comprise," and "include" should be interpreted as "not excluding the presence of elements other than those listed." In addition, the modifier "a" should be interpreted as "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Furthermore, it should be interpreted to include combinations of these with elements other than "A," "B," and "C."

Claims

1. a master oscillator that outputs a pulsed laser beam at a first discharge timing synchronized with the repetition frequency; an amplifier that amplifies the pulsed laser light by exciting a laser medium through which the pulsed laser light passes at a second discharge timing; A processor that sets the second discharge timing by adding a delay time to the first discharge timing, A first value is held as a command value of the delay time corresponding to a first repetition frequency, and a second value is held as a command value of the delay time corresponding to a second repetition frequency different from the first repetition frequency; When the repetition frequency is changed from the first repetition frequency to the second repetition frequency after the command value of the first value is output, a processor that outputs the command value of the second value after outputting the command value of a third value between the first value and the second value; A laser device comprising:

2. 2. The laser device according to claim 1, the third value is varied on a pulse-by-pulse basis over a plurality of pulses. Laser device.

3. 2. The laser device according to claim 1, the processor outputs the command value of the first value, and then gradually changes the third value over a plurality of pulses to output the command value; Laser device.

4. 2. The laser device according to claim 1, When the repetition frequency is changed from the first repetition frequency to a second repetition frequency, The command value is gradually changed from the first value to the second value over a plurality of pulses. Laser device.

5. 5. The laser device according to claim 4, a change amount per pulse of the command value which is gradually changed over the plurality of pulses is constant; Laser device.

6. 5. The laser device according to claim 4, a change amount per pulse of the command value that is gradually changed over the plurality of pulses is determined depending on the first repetition frequency and the second repetition frequency. Laser device.

7. 5. The laser device according to claim 4, a change amount per pulse of the command value which is gradually changed over the plurality of pulses is determined to be a value which satisfies both of the allowable values ​​of the spectral width deviation and the energy stability of the pulse energy. Laser device.

8. 5. The laser device according to claim 4, a change amount per pulse of the command value which is gradually changed over the plurality of pulses is determined to be a value that satisfies a tolerance of either a spectral width deviation or an energy stability of pulse energy. Laser device.

9. 5. The laser device according to claim 4, a change amount per pulse of the command value that is gradually changed over the plurality of pulses is set so that the command value reaches the second value within a predetermined number of pulses after the command value of the first value is output. Laser device.

10. 10. The laser device according to claim 9, The predetermined number of pulses is 5 pulses. Laser device.

11. 5. The laser device according to claim 4, If a target value of the change amount of the command value from the first value to the second value is ΔD and a predetermined number of pulses is N, then The processor calculates a change amount Δd per pulse of the command value that is gradually changed over the plurality of pulses as follows: Δd=ΔD / N Set to Laser device.

12. 2. The laser device according to claim 1, The processor holds a relationship between the repetition frequency and the command value as table data, determining the first value and the second value based on the table data; Laser device.

13. 2. The laser device according to claim 1, The processor holds a relationship between the repetition frequency and the command value as table data, when the repetition frequency is changed from the first repetition frequency to the second repetition frequency, a change amount of the command value is determined by referring to the table data. Laser device.

14. 2. The laser device according to claim 1, The processor controls an excitation voltage of the amplifier to stabilize the pulse energy of the pulsed laser light. Laser device.

15. 15. The laser device of claim 14, When the repetition frequency is changed from the first repetition frequency to a second repetition frequency, the processor gradually varies the excitation voltage over a number of pulses during which the command value of the third value is output. Laser device.

16. 2. The laser device according to claim 1, The amplifier includes a chamber in which a mixed gas containing a rare gas as the laser medium, a halogen gas, and a buffer gas is accommodated. Laser device.

17. A laser oscillation method, comprising: outputting a pulsed laser beam from a master oscillator at a first discharge timing synchronized with the repetition frequency; amplifying the pulsed laser light by exciting a laser medium of an amplifier through which the pulsed laser light passes at a second discharge timing; and a processor sets the second discharge timing by adding a delay time to the first discharge timing, The processor holds a first value as a command value of the delay time corresponding to a first repetition frequency, and holds a second value as a command value of the delay time corresponding to a second repetition frequency different from the first repetition frequency; When the repetition frequency is changed from the first repetition frequency to the second repetition frequency after the processor outputs the command value of the first value, outputting the command value of the second value after outputting the command value of a third value between the first value and the second value. Laser oscillation method.

18. 1. A method for manufacturing an electronic device, comprising: a master oscillator that outputs a pulsed laser beam at a first discharge timing synchronized with the repetition frequency; an amplifier that amplifies the pulsed laser light by exciting a laser medium through which the pulsed laser light passes at a second discharge timing; A processor that sets the second discharge timing by adding a delay time to the first discharge timing, A first value is held as a command value of the delay time corresponding to a first repetition frequency, and a second value is held as a command value of the delay time corresponding to a second repetition frequency different from the first repetition frequency; When the repetition frequency is changed from the first repetition frequency to the second repetition frequency after the command value of the first value is output, a processor that outputs the command value of the second value after outputting the command value of a third value between the first value and the second value; A laser beam is generated by a laser device comprising: outputting the laser light to an exposure device; exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device. A method for manufacturing an electronic device.

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