Laser apparatus, laser control method, and electronic device manufacturing method

Abstract

The laser apparatus according to one aspect of the present disclosure comprises: a master oscillator for outputting a pulsed laser beam at a first discharge timing synchronized to a repetition frequency; an amplifier for exciting a laser medium through which the pulsed laser beam passes by using a charging voltage at a second discharge timing, thereby amplifying the pulsed laser beam; and a processor configured so as to, on the basis of a charging voltage command value commanded by an exposure apparatus, command the charging voltage to the amplifier and add a delay time to the first discharge timing to thereby set the second discharge timing, the processor changing the delay time and correcting the charging voltage command value in accordance with a change in the repetition frequency.

Description

[Technical field]

[0001] The present disclosure relates to a laser apparatus, a laser control 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. 7,756,171 [Patent Document 2] Summary of U.S. Patent Application Publication No. 2018 / 0309259

[0005] A laser device according to one aspect of the present disclosure includes a master oscillator that outputs a pulsed laser beam at a first discharge timing synchronized with a repetition frequency, an amplifier that amplifies the pulsed laser beam by exciting a laser medium through which the pulsed laser beam passes with a charging voltage at a second discharge timing, and a processor configured to command a charging voltage to the amplifier based on a charging voltage command value commanded from an exposure device and set the second discharge timing by adding a delay time to the first discharge timing, wherein the processor performs a process of changing the delay time and a process of correcting the charging voltage command value in response to a change in the repetition frequency.

[0006] A laser control 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, exciting a laser medium of an amplifier through which the pulsed laser beam passes with a charging voltage at a second discharge timing obtained by adding a delay time to the first discharge timing to amplify the pulsed laser beam, commanding a charging voltage to the amplifier based on a charging voltage command value commanded from an exposure device, and performing a process of changing the delay time and a process of correcting the charging voltage command value in response to a change in the repetition frequency.

[0007] A method for manufacturing an electronic device according to another aspect of the present disclosure 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 with a charging voltage at a second discharge timing; and a processor configured to command a charging voltage to the amplifier based on a charging voltage command value commanded from an exposure device and set the second discharge timing by adding a delay time to the first discharge timing, the processor performing a process of changing the delay time and a process of correcting the charging voltage command value in response to a change in the repetition frequency; outputting the laser light to an exposure device; and exposing a photosensitive substrate to the laser light in the exposure device 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, and shows an example of the HV gain and offset determined by linear function approximation. [Figure 6] FIG. 6 is an example of a graph showing the laser operation when the control of Comparative Example 1 is applied. [Figure 7] FIG. 7 is an example of a graph showing the laser operation when the control of Comparative Example 2, which includes the control for suppressing the spectral width fluctuation using the characteristic shown in FIG. 3, is applied. [Figure 8] FIG. 8 is an example of a graph showing the relationship between the MO charging voltage and / or the PO charging voltage and the pulse energy, and shows an example of the change in characteristics due to a change in the delay time. [Figure 9] FIG. 9 is an example of a graph showing the relationship between the MO charging voltage and / or the PO charging voltage and the pulse energy, and shows an example in which the HV gain and offset change with a change in the delay time. [Figure 10] FIG. 10 illustrates a schematic configuration example of the laser device according to the first embodiment. [Figure 11] FIG. 11 is an example of a table that defines the correspondence between the repetition frequency, the delay time change amount, and the HV correction coefficient. [Figure 12]FIG. 12 is a flowchart showing an example of control of the PO charging voltage in the laser apparatus according to the first embodiment. [Figure 13] FIG. 13 illustrates a schematic configuration example of a laser device according to the second embodiment. [Figure 14] FIG. 14 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 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.Other Applications 6. Manufacturing methods for electronic devices 7.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 (F 2 ) 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 operatively connected to the energy control unit 32 and the wavelength control unit 60. The energy control unit 32 is operatively 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 device 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 device 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 operatively 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] The laser control unit 30 is also operatively connected to the beam measurement instrument 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, a PO charging voltage command value, and other target data from the exposure device 70. The laser control unit 30 outputs the light emission trigger signal and the PO charging voltage command value to the energy control unit 32.

[0035] The energy control unit 32 outputs a first trigger signal synchronized with the light emission trigger signal and an MO charging voltage command value to the master oscillator 10. The first trigger signal is a signal that specifies the MO charging timing. The MO charging voltage may be the same as the PO charging voltage, or may be different from the PO charging voltage.

[0036] The master oscillator 10 can output a seed laser beam in synchronization with a first trigger signal. The seed laser beam output by the master oscillator 10 has a narrow band.

[0037] 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 .

[0038] 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.

[0039] 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.

[0040] 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 spectrum width and pulse energy. The horizontal axis of FIG. 3 represents the delay time D, the left vertical axis of FIG. 3 represents the spectrum width, and the right vertical axis of FIG. 3 represents the pulse energy. A graph G1 shown by a solid line in FIG. 3 shows the relationship between the delay time D and the spectrum width. A 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 spectrum 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 taken as a nominal value Dt. The delay time D when the repetition frequency is RR0 is set to Dt. The nominal value Dt of the delay time D may be expressed as a "nominal delay time Dt".

[0041] 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 the repetition frequency is changed, using the characteristics shown in FIG. 3. Here, FIG. 3 shows the characteristics after the repetition frequency is changed from RR0 to RR. Therefore, the spectrum width corresponding to the delay time Dt is the width when the repetition frequency is RR. That is, from the characteristics shown in FIG. 2, ΔBW at a certain repetition frequency RR can be known. Also, from the characteristics shown in FIG. 3, it can be seen that in order to cancel or reduce ΔBW, it is sufficient to change the delay time D from the nominal value Dt by the change amount ΔD. The change amount ΔD of the delay time D may be expressed as "delay time change amount ΔD".

[0042] 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.

[0043] 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 characteristics such as the graph of the curve indicated by C0 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. "HV gain" and "offset" are sometimes used as parameters for this feedback control.

[0044] When the pulse energy Ep of the laser device 1 can be approximated as a linear function of the charging voltage command value HV as in the following equation (1), the slope α is called the HV gain and the intercept β is called the offset.

[0045] Ep = αHV + β (1) In Fig. 3, when the delay time D is changed by ΔD so as to maintain the spectral width in response to the change in the repetition frequency from RR0 to RR, the pulse energy fluctuates by ΔE. The HV control operates to compensate for this energy fluctuation. The energy control unit 32 feedback-controls the PO charging voltage based on the measurement result of the PO pulse energy measuring device 274.

[0046] 2. Challenges In the laser device 1, the HV gain and offset in the operating region are calculated by approximating the pulse energy characteristics as shown in Fig. 5 with a linear function. Fig. 5 shows an example in which the HV gain α0 is calculated from the slope of the tangent at the nominal energy value Et in the pulse energy characteristic curve C0. The intercept of this tangent is the offset β0. In the HV control, a charging voltage based on the HV gain and offset is output so that the pulse energy becomes constant (a value within the target range).

[0047] On the other hand, there are cases where the exposure device 70 instructs the laser device 1 to switch the repetition frequency (see FIG. 6). FIG. 6 is an example of a graph showing the laser operation 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.

[0048] In FIG. 6, from the top, graphs G6A to G6D showing transitions in the values ​​of the repetition frequency, the delay time D, the spectral width, and the pulse energy are shown on a common time axis.

[0049] When the repetition frequency is changed by a command from the exposure tool 70, a rapid spectral width fluctuation may occur with the switching of the repetition frequency due to the characteristics shown in Fig. 2 (graph G6C in Fig. 6). In order to suppress this spectral width fluctuation, the delay time D between the MO discharge timing and the PO discharge timing may be changed from the nominal value Dt by utilizing the characteristics shown in Fig. 3.

[0050] Fig. 7 is an example of a graph showing laser operation when the control of Comparative Example 2 is applied, including the control of suppressing the variation in the spectral width using the characteristic shown in Fig. 3. In Fig. 7, similar to Fig. 6, from the top, graphs G7A to G7D showing the transition of the values ​​of the repetition frequency, the delay time D, the spectral width, and the pulse energy are shown on a common time axis.

[0051] In order to suppress the rapid spectral width fluctuation accompanying the switching of the repetition frequency, the delay time D is controlled to change from the nominal value Dt by ΔD in accordance with the change of the repetition frequency, as shown in graph G7B, by utilizing the characteristics shown in Fig. 3. This allows the spectral width to fall within a predetermined allowable range even after the switching of the repetition frequency, as shown in graph G7C.

[0052] However, when the delay time D between the MO discharge timing and the PO discharge timing is changed (see graph G7B), the pulse energy fluctuates according to the characteristics shown in Fig. 3. At the same time, the characteristics shown in Fig. 5 also change with the delay time D, and the HV gain and offset to be used for HV control change (see Figs. 8 and 9).

[0053] The characteristic curve C1 shown by the dashed line in Fig. 8 is an example of the characteristics when the delay time D is the nominal value Dt, and the characteristic curve C2 shown by the solid line is an example of the characteristics when the delay time D is Dt+ΔD. For example, in the case of Fig. 8, assume that the HV control operates so that the pulse energy is within the target range when the delay time D=Dt, and the PO charging voltage becomes V0. Here, if the delay time D is changed from Dt to Dt+ΔD, the pulse energy decreases due to the characteristics shown in Fig. 3, and the pulse energy at the PO charging voltage V0 decreases by ΔE, which may deviate from the target range (see graph G7D in Fig. 7).

[0054] To compensate for the pulse energy reduction amount ΔE caused by the change in delay time D, HV control is operated again, and the HV gain α0 and offset β0 at delay time D=Dt are also used in this HV control.

[0055] On the other hand, when the delay time D is changed to Dt+ΔD, the HV gain and offset of the laser device 1 change (see FIG. 9), causing a mismatch with the HV gain and offset used by the HV control. This mismatch can cause the HV control to respond excessively, making the pulse energy control unstable. Or, the HV control can respond insufficiently, requiring a larger number of pulses until the pulse energy control settles within the target range.

[0056] As a result, when the delay time D is changed, the control of the pulse energy becomes unstable and may deviate from the target range (graph G7D in FIG. 7).

[0057] As described above, when the repetition frequency is switched in response to an instruction from the exposure tool 70, the HV control may become unstable.

[0058] 3. Embodiment 1 3.1 Configuration Fig. 10 shows a schematic configuration of a laser device 101 according to embodiment 1. Differences between the configuration shown in Fig. 10 and Fig. 1 will be described.

[0059] 10 includes a charging voltage correction unit 34 between the energy control unit 32 and the PO charger 26. The charging voltage correction unit 34 may be configured by software, or may be realized as a part of the function of the energy control unit 32. Alternatively, the charging voltage correction unit 34 may be configured using a processor separate from the energy control unit 32.

[0060] Further, the laser device 101 has a table as shown in FIG. 11, which adds HV correction coefficients A(ΔD) and B(ΔD), which are functions of the delay time change amount ΔD, to the table described in FIG.

[0061] The HV correction coefficient A(ΔD) and the HV correction coefficient B(ΔD) are calculated based on the following equations (2) and (3), respectively.

[0062] A(ΔD)=α0 / α(ΔD) (2) B(ΔD)=(β0-β(ΔD)) / α(ΔD) (3) In the formula, α0 and β0 are the HV gain and offset when the delay time D is the nominal value Dt (i.e., ΔD=0). α(ΔD) and β(ΔD) are the HV gain and offset that are functions of the delay time change amount ΔD.

[0063] 3.2 Operation The energy control unit 32 determines the delay time change amount ΔD and the HV correction coefficients A(ΔD) and B(ΔD) corresponding to ΔD in response to changes in operating conditions such as switching of the repetition frequency (FIG. 12). The charge voltage correction unit 34 calculates the charge voltage correction value HVcmp from the charge voltage command value HVcmd received from the exposure device 70 and the HV correction coefficients A(ΔD) and B(ΔD) using the following formula (4).

[0064] HVcmp=A(ΔD)*HVcmd+B(ΔD) (4) Then, the charging voltage correction unit 34 outputs the charging voltage correction value HVcmp as a command value for commanding the PO charging voltage. The charging capacitor of the PO pulse power module 25 is charged by the PO charger 26, and the laser gas in the PO chamber 23 is excited by the PO charging voltage corresponding to the charging voltage correction value HVcmp. As a result, a pulse laser beam amplified to a pulse energy corresponding to the PO charging voltage is output from the power oscillator 20.

[0065] The power oscillator 20 is an example of an "amplifier" in this disclosure, and the laser gas contained in the PO chamber 23 is an example of a "laser medium" in this disclosure. The MO discharge timing is an example of a "first discharge timing" in this disclosure. The PO discharge timing is an example of a "second discharge timing" in this disclosure. The repetition frequency RR0 is an example of a "first repetition frequency" in this disclosure, and RR is an example of a "second repetition frequency" in this disclosure. The nominal delay time Dt set when the repetition frequency is RR0 is an example of a "first delay time" in this disclosure. The HV correction coefficients A(ΔD) and B(ΔD) used in the correction process performed by the charging voltage correction unit 34 are examples of "correction coefficients" in this disclosure. The HV correction coefficient A(ΔD) multiplied by the charging voltage command value HVcmd is an example of a “first correction coefficient” in this disclosure, and B(ΔD) added to the product of HVcmd and A(ΔD) is an example of a “second correction coefficient” in this disclosure.

[0066] Fig. 12 is a flowchart showing an example of control of the laser device 101 according to embodiment 1. The flowchart in Fig. 12 can be realized by a processor functioning as the energy control unit 32 and / or the charging voltage correction unit 34 executing a program.

[0067] In step S11, the energy control unit 32 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.

[0068] In step S12, the energy control unit 32 updates the delay time change amount ΔD as a target value for changing the delay time D and the HV correction coefficients A(ΔD) and B(ΔD) based on the table (FIG. 11). After step S12, the process proceeds to step S13.

[0069] Furthermore, if it is determined in step S11 that the repetition frequency has not been changed and the determination result in step S11 is a False determination, the energy control unit 32 and the charging voltage correction unit 34 skip step S12 and proceed to step S13.

[0070] Next, in step S13, the charging voltage correction unit 34 calculates the charging voltage correction value HVcmp according to equation (4), and outputs the calculated charging voltage correction value HVcmp to the PO charger 26 as a command value that commands the PO charging voltage.

[0071] After step S13, the energy control unit 32 and the charging voltage correction unit 34 end the flow chart of FIG.

[0072] The energy control unit 32 and the charging voltage correction unit 34 can repeatedly execute the process of the flowchart in FIG. 12 for each pulse.

[0073] A laser control method including the processing according to the flowchart in FIG. 12 is an example of the "laser control method" in this disclosure.

[0074] 3.3 Actions and Effects According to the laser device 101 of the first embodiment, when operating with the delay time change amount ΔD, the pulse energy Ep is approximated by the following equation.

[0075]

number

[0076] That is, the HV gain and offset for the charging voltage command value HVcmd appear to the exposure tool 70 as nominal values ​​α0, β0, and fluctuations accompanying changes in the delay time change amount ΔD are suppressed. As a result, even if the repetition frequency is switched in response to an instruction from the exposure tool 70, the HV control is prevented from becoming unstable.

[0077] 4. Embodiment 2 4.1 Configuration Fig. 13 shows a schematic configuration of a laser device 102 according to the second embodiment. Differences between the configuration in Fig. 13 and Fig. 10 will be described. The MO charging voltage in the laser device 102 according to the second embodiment is the same as the PO charging voltage. A signal line is provided between the charging voltage correction unit 34 and the MO charger 16, for transmitting a command for the MO charging voltage that is the same as the PO charging voltage from the charging voltage correction unit 34 to the MO charger 16. The other configurations may be the same as those of the laser device 101 according to the first embodiment.

[0078] However, since the MO charging voltage is different from that of embodiment 1, the values ​​of the device parameters may be different from those of embodiment 1. For example, the values ​​of α0 and β0 may be different from those of embodiment 1. Similarly, the values ​​of α(ΔD), β(ΔD), A(ΔD), and B(ΔD) may also be different from those of embodiment 1.

[0079] 4.2 Operation The operation of the laser device 102 according to the second embodiment will be described with respect to the differences from the laser device 101 according to the first embodiment. In the second embodiment, the charge voltage correction unit 34 outputs the charge voltage correction value HVcmp as the P0 charge voltage and the MO charge voltage. The other operations are the same as those of the first embodiment.

[0080] 4.3 Actions and Effects According to the laser device 102 of the second embodiment, the same actions and effects as those of the first embodiment can be obtained.

[0081] 5.Other Applications In the above first and second embodiments, the repetition frequency is changed as an example, but other operating conditions may be changed. 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 control for "reducing changes (fluctuations) in the laser light characteristics by changing the delay time D according to the operating conditions." When the delay time D is changed in accordance with changes in the operating conditions, the charging voltage is corrected to suppress deviation of the laser light characteristics from the target range.

[0082] 6. Manufacturing methods for electronic devices 14 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 a laser device 101. The projection optical system 76 reduces and projects the laser light that has passed 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.

[0083] The exposure apparatus 70 exposes the workpiece with laser light reflecting a 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. The semiconductor device is an example of an "electronic device" in this disclosure. Laser apparatus 102 may be used instead of laser apparatus 101.

[0084] 7.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.

[0085] 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 with a charging voltage at a second discharge timing; a processor configured to command the amplifier to set the charging voltage based on a charging voltage command value commanded by an exposure apparatus, and to set the second discharge timing by adding a delay time to the first discharge timing, the processor performing a process of changing the delay time and a process of correcting the charging voltage command value in response to a change in the repetition frequency; A laser device comprising:

2. 2. The laser device according to claim 1, The processor performs a process of changing the delay time and a process of correcting the charging voltage command value by using a table in which the repetition frequency, the delay time, and a correction coefficient used for correcting the charging voltage command value correspond to each other. Laser device.

3. 2. The laser device according to claim 1, The processor stores a table in which the repetition frequency, the change amount of the delay time, and a correction coefficient used to correct the charging voltage command value correspond to each other; determining the change amount and the correction coefficient based on the table in response to the change in the repetition frequency; calculating a charging voltage correction value from the determined correction coefficient and the charging voltage command value; outputting the charging voltage correction value as a command value for commanding the charging voltage of the amplifier; Laser device.

4. 4. The laser device according to claim 3, the correction coefficients include a first correction coefficient by which the charging voltage command value is multiplied, and a second correction coefficient by which a product of the charging voltage command value and the first correction coefficient is added. Laser device.

5. 2. The laser device according to claim 1, A first correction coefficient and a second correction coefficient are used in the process of correcting the charging voltage command value, each of the first correction coefficient and the second correction coefficient is a function of a change amount of the delay time; Let the change amount be ΔD, the first correction coefficient be A(ΔD), the second correction coefficient be B(ΔD), the charging voltage command value commanded from the exposure apparatus be HVcmd, and the charging voltage correction value obtained by the correction be HVcmp. The processor may include: HVcmp=A(ΔD)*HVcmd+B(ΔD) and determining the charging voltage correction value by correcting the charging voltage command value. Laser device.

6. 6. The laser device according to claim 5, When the pulse energy of the output laser light output from the amplifier is approximated by a linear function with respect to the command value for the charging voltage, the slope of the linear function is called a gain and the intercept is called an offset. the delay time is set to a first delay time when the repetition frequency is a first repetition frequency; The gain and the offset in the first delay time are α0 and β0, respectively, and the change amount when the repetition frequency is changed from the first repetition frequency to the second repetition frequency is ΔD. The gain and the offset, which are functions of the change amount, are α(ΔD) and β(ΔD), respectively. The first correction coefficient and the second correction coefficient are each expressed by the following formula: A(ΔD)=α0 / α(ΔD) B(ΔD) = (β0-β(ΔD)) / α(ΔD) Determined based on Laser device.

7. 2. The laser device according to claim 1, The processor also dictates the charging voltage to the master oscillator. Laser device.

8. 2. The laser device according to claim 1, The processor changes the delay time so as to suppress a variation in a spectral width caused by the change in the repetition frequency, and corrects the charging voltage command value so as to suppress a variation in a pulse energy caused by the change in the delay time. Laser device.

9. 2. The laser device according to claim 1, a pulse energy measuring device for measuring the pulse energy of the output laser light output from the amplifier; The processor, commanding the charging voltage based on a measurement result of the pulse energy measuring device so that the pulse energy measured using the pulse energy measuring device falls within a target range; Laser device.

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

11. 1. A method for controlling a laser, 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 by a charging voltage at a second discharge timing obtained by adding a delay time to the first discharge timing; commanding the amplifier to set a charging voltage based on a charging voltage command value commanded by an exposure device; In response to the change in the repetition frequency, a process of changing the delay time and a process of correcting the charging voltage command value are performed. Laser control method.

12. 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 with a charging voltage at a second discharge timing; commanding the amplifier to set the charging voltage based on a charging voltage command value commanded by an exposure device; A processor configured to set the second discharge timing by adding a delay time to the first discharge timing, the processor performing a process of changing the delay time and a process of correcting the charging voltage command value in response to a change in the repetition frequency; 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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