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

Abstract

To provide a laser device which suppresses instability in HV control even when switching of a repetition frequency is performed in response to instructions of an exposure device.SOLUTION: A laser device comprises: 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 which commands a charging voltage to the amplifier on the basis of a charging voltage command value commanded from an exposure device, sets the second discharge timing by adding a delay time to the first discharge timing and performs processing to change the delay time and processing to correct the charging voltage command value in accordance with changes in the repetition frequency.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a laser device, a laser control method, and a method of manufacturing an electronic device.

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, with the miniaturization and high integration of semiconductor integrated circuits, an improvement in resolution has been demanded. For this reason, the wavelength of light emitted from an exposure light source has been made shorter. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs laser light having a wavelength of about 248 nm and an ArF excimer laser device that outputs laser light having a wavelength of about 193 nm are used.

[0003] The spectral linewidth of the spontaneous emission light of a KrF excimer laser device and an ArF excimer laser device is as wide as 350 to 400 pm. Therefore, when a projection lens is configured with 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 linewidth of the laser light output from the gas laser device to such an extent that chromatic aberration can be ignored. For this reason, a narrowband module (Line Narrow Module: LNM) including a narrowband element (etalon, grating, etc.) may be provided in the laser resonator of the gas laser device in order to narrow the spectral linewidth. Hereinafter, a gas laser device whose spectral linewidth is narrowed is referred to as a narrowband gas laser device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

[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 with a charging voltage at a second discharge timing; and a processor configured to command the 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.

[0006] A laser control method according to another aspect of the present disclosure includes: outputting pulsed laser light 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 light 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 light; commanding the 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 by a laser device 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 the 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 with the laser light in the exposure device to manufacture the electronic device.

Brief Description of the Drawings

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

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[0009] -Table of Contents- 1. Overview of Laser Device 1.1 Configuration 1.2 Operation 1.3 Characteristics of Narrow-Band Laser 2. Problems 3. Embodiment 1 3.1 Configuration 3.2 Operation 3.3 Function and Effect 4. Embodiment 2 4.1 Configuration 4.2 Operation 4.3 Function and Effect 5. Other Application Examples 6. Regarding the Manufacturing Method of Electronic Devices 7. Others Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0010] 1. Overview of Laser Device 1.1 Configuration FIG. 1 schematically shows a configuration example of the 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 include high reflection mirrors 41 and 42, a beam measurer 50, a wavelength control unit 60, and a wavelength adjustment unit 62.

[0011] The master oscillator 10 includes a narrowband module (LNM) 12, an MO chamber 13, an MO output coupling mirror 14, an MO pulse power module (PPM) 15, and an MO charger 16. The LNM 12 includes a prism 122 and a grating 124 for narrowing the spectral width. The grating 124 is retrofitted so that the incident angle and the diffraction angle coincide.

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

[0013] The MO chamber 13 is arranged 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. Laser gas is supplied into the MO chamber 13 from a gas supply device (not shown). The laser gas is an excimer laser gas containing 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 pulse power module 15 includes a switch 152 and a charging capacitor (not shown), and is connected to the discharge electrode 132 through 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 pulse 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 device 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 arranged such that the reflected light of the beam splitter 17 is incident on the MO pulse energy measuring device 18. The MO pulse energy measuring device 18 includes a condenser lens (not shown) and an optical sensor. The optical sensor may be a high-speed response photodiode resistant to ultraviolet light. A signal line for transmitting the information obtained by the MO pulse energy measuring device 18 to the energy control unit 32 is provided between the MO pulse energy measuring device 18 and 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 such that the laser light output from the master oscillator 10 is incident on the power oscillator 20.

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

[0019] The rear mirror 22 and the PO output coupling mirror 24 constitute 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 the same as that of the MO chamber 13. The PO chamber 23 includes a pair of discharge electrodes 232 and 233, and two windows 234 and 236. Laser gas is supplied into the PO chamber 23 in the same manner as in the MO chamber 13. The rear mirror 22 may be, for example, a partial reflection mirror with a reflectivity of 80% to 90%. The PO output coupling mirror 24 may be, for example, a partial reflection mirror with a reflectivity 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 through a feed-through 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 axis direction of the laser light output from the power oscillator 20 is the z direction. The two directions substantially orthogonal to the z direction may be the h direction and the v direction. The v direction is a direction substantially orthogonal to the plane of the drawing of FIG. 1. The discharge electrodes 232 and 233 are arranged to face each other in the h direction.

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

[0024] The beam splitter 271 is arranged on the optical path of the pulsed laser light output from the PO output coupling mirror 24. The beam splitter 272 is arranged on the optical path of the pulsed laser light reflected by the beam splitter 271. The beam splitter 272 is arranged such that the reflected light of the beam splitter 272 is incident on the PO pulse energy meter 274 and the transmitted light of the beam splitter 272 is incident on the spectrum meter 276. The configuration of the PO pulse energy meter 274 may be the same as that of the MO pulse energy meter 18.

[0025] A signal line for transmitting the information obtained by the PO pulse energy meter 274 to the energy control unit 32 is provided between the PO pulse energy meter 274 and the energy control unit 32.

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

[0027] The beam measuring device 50 includes a beam splitter 51, a polarization measuring device 52, a beam pointing measuring device 54, and a beam profiler 56. The beam splitter 51 is disposed on the optical path of the pulsed laser beam that has passed through the beam splitter 271 of the monitor module 27.

[0028] The beam splitter 51 is arranged such that the reflected light of the beam splitter 51 is incident on each of the polarization measuring device 52, the beam pointing measuring device 54, and the beam profiler 56 via an optical element (not shown), and the transmitted light of the beam splitter 51 is incident on the exposure device 70. A signal line for transmitting the beam-related data obtained by the beam measuring device 50 to the laser control unit 30 is provided between the beam measuring device 50 and 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 for charging the charging capacitor of the MO pulse power module 15. Further, the energy control unit 32 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 for charging 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 spectrum measuring device 276, and transmits the wavelength control related data to the laser control unit 30. The wavelength control unit 60 is operatively connected to the wavelength adjustment unit 62. The wavelength adjustment unit 62 includes a rotational drive mechanism such as a rotational stage that rotates the prism 122 of the LNM12, for example. The wavelength adjustment unit 62 is controlled based on the wavelength measured by the spectrum measuring device 276.

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

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

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

[0034] 1.2 Operations 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 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 defines 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 seed laser light synchronized with the first trigger signal. The seed laser light output by the master oscillator 10 is narrowband.

[0037] The seed laser light output by the master oscillator 10 can enter the power oscillator 20 via the 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 the 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 defines the PO discharge timing. The PO discharge timing becomes a timing with a delay time added to the MO discharge timing. The power oscillator 20 can form a discharge region synchronized 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 output laser light.

[0039] 1.3 Characteristics of the narrowband laser 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 complexly with respect to the repetition frequency. Therefore, when the repetition frequency changes from the nominal value RR0 to a certain value RR, the spectral width changes by ΔBW. Also, 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, the spectral width, and the pulse energy. The horizontal axis in FIG. 3 represents the delay time D, the left vertical axis in FIG. 3 represents the spectral width, and the right vertical axis represents the pulse energy. The graph G1 shown by the solid line in FIG. 3 shows the relationship between the delay time D and the spectral width. The graph G2 shown by the broken 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 taken as the 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 referred to as the "nominal delay time Dt".

[0041] When the laser control unit 30 changes the repetition frequency from RR0 to RR, it corrects the change amount ΔBW of the spectral width that occurs when the repetition frequency is changed by 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 spectral 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, the 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, the delay time D may be changed by the change amount ΔD from the nominal value Dt. The change amount ΔD of the delay time D may be referred to as the "delay time change amount ΔD".

[0042] As a result, as shown in FIG. 4, a table that associates the repetition frequency RR with the delay time change amount ΔD is obtained. 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 exhibits characteristics such as those of the graph of the curve indicated by C0 in FIG. 5, for example. The characteristics shown in FIG. 5 are utilized for stabilizing the pulse energy. For example, when outputting laser light to the exposure apparatus 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" may be 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 with respect to 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 corresponding to the change in the repetition frequency from RR0 to RR, the pulse energy fluctuates by ΔE. HV control acts 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 meter 274.

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

[0047] On the other hand, the exposure apparatus 70 may instruct the laser apparatus 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 recognized by the applicant as being known only to the applicant and is not a known example recognized by the applicant.

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

[0049] When the repetition frequency is changed by a command from the exposure apparatus 70, due to the characteristics shown in FIG. 2, rapid spectral width fluctuations may occur with the switching of the repetition frequency (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 using the characteristics shown in FIG. 3.

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

[0051] In order to suppress the rapid spectral width fluctuation accompanying the switching of the repetition frequency, control is performed to change the delay time D from the nominal value Dt by ΔD in accordance with the change in the repetition frequency, as shown in graph G7B, by using the characteristics shown in FIG. 3. As a result, as shown in graph G7C, the spectral width can be kept within a predetermined allowable range even after the switching of the repetition frequency.

[0052] However, when changing the delay time D between the MO discharge timing and the PO discharge timing (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, when the delay time D is changed from Dt to Dt + ΔD, the pulse energy decreases according to the characteristics shown in FIG. 3, and the pulse energy at the PO charging voltage V0 decreases by ΔE and may deviate from the target range (see graph G7D in FIG. 7).

[0054] In order to compensate for the decrease amount ΔE of the pulse energy accompanying the change of the delay time D, the HV control operates again, but also the HV gain α0 and the offset β0 at the delay time D = Dt are used in this HV control.

[0055] On the other hand, when the delay time D is changed to Dt + ΔD, since the HV gain and the offset of the laser device 1 change (see FIG. 9), there is a mismatch with the HV gain and the offset used by the HV control. Due to this mismatch, the response of the HV control becomes excessive, and the control of the pulse energy may become unstable. Or the response of the HV control becomes insufficient, and more pulses may be required until the control of the pulse energy 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 switching the repetition frequency in response to the instruction of the exposure apparatus 70, the HV control may become unstable.

[0058] 3. Embodiment 1 3.1 Configuration FIG. 10 schematically shows the configuration of the laser device 101 according to Embodiment 1. Regarding the configuration shown in FIG. 10, the differences from FIG. 1 will be described.

[0059] The laser device 101 shown in FIG. 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 functions of the energy control unit 32. Alternatively, the charging voltage correction unit 34 may be configured using a processor different from the energy control unit 32.

[0060] Also, the laser device 101 has a table as shown in FIG. 11 in which HV correction coefficients A(ΔD) and B(ΔD), which are functions of the delay time change amount ΔD, are added to the table described in FIG. 4.

[0061] Each of the HV correction coefficient A(ΔD) and the HV correction coefficient B(ΔD) is calculated based on, for example, the following equations (2) and (3).

[0062] A(ΔD)=α0 / α(ΔD) (2) B(ΔD)=(β0 - β(ΔD)) / α(ΔD) (3) α0 and β0 in the equations are the HV gain and offset when the delay time D is the nominal value Dt (that is, 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 charging voltage correction unit 34 calculates a charging voltage correction value HVcmp from the charging voltage command value HVcmd received from the exposure device 70 and the HV correction coefficients A(ΔD) and B(ΔD) by the following equation (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. Thereby, the pulsed laser light amplified to the pulse energy corresponding to the PO charging voltage is output from the power oscillator 20.

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

[0066] FIG. 12 is a flowchart showing a control example of the laser device 101 according to Embodiment 1. The flowchart of 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 the repetition frequency has been changed. If the repetition frequency has been changed and the determination result in step S11 is a True determination, the process proceeds to step S12.

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

[0069] Also, in the determination of step S11, when the repetition frequency has not been changed and the determination result of 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 obtains a 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 for commanding the PO charging voltage.

[0071] After step S13, the energy control unit 32 and the charging voltage correction unit 34 end the flowchart of FIG. 12.

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

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

[0074] 3.3 Function and Effect According to the laser device 101 according to Embodiment 1, when operating with the delay time change amount ΔD, the pulse energy Ep is approximated by the following equation.

[0075]

Equation

[0076] That is, apparently from the exposure apparatus 70, the HV gain and offset with respect to the charging voltage command value HVcmd become the nominal values α0 and β0, and fluctuations associated with changes in the delay time change amount ΔD are suppressed. As a result, even when the repetition frequency is switched in response to an instruction from the exposure apparatus 70, it is possible to suppress the HV control from becoming unstable.

[0077] 4. Embodiment 2 4.1 Configuration FIG. 13 schematically shows the configuration of the laser device 102 according to Embodiment 2. Differences from FIG. 10 in the configuration of FIG. 13 will be described. The MO charging voltage in the laser device 102 according to Embodiment 2 is the same as the PO charging voltage. A signal line for transmitting a command of the same MO charging voltage as the PO charging voltage from the charging voltage correction unit 34 to the MO charger 16 is provided between the charging voltage correction unit 34 and the MO charger 16. Other configurations may be the same as those of the laser device 101 according to Embodiment 1.

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

[0079] 4.2 Operation Differences in the operation of the laser device 102 according to Embodiment 2 from that of the laser device 101 according to Embodiment 1 will be described. In Embodiment 2, the charging voltage correction unit 34 outputs the charging voltage correction value HVcmp as both the P0 charging voltage and the MO charging voltage. Other operations are the same as those in Embodiment 1.

[0080] 4.3 Effects According to the laser device 102 according to Embodiment 2, the same effects as those in Embodiment 1 can be obtained.

[0081] 5. Other application examples In each of the above-described Embodiments 1 and 2, the change in the repetition frequency was described as an example. However, the present invention is not limited to this, and other operating conditions may be changed. Further, the spectral width is an example of the characteristics of the laser light, and the delay time D may be changed in order to suppress fluctuations in other characteristics. The laser control technique according to the present disclosure can be applied to control that "reduces the change (fluctuation) in the characteristics of the laser light by changing the delay time D according to the operating conditions." When changing the delay time D in accordance with the change in the operating conditions, by correcting the charging voltage, it is possible to suppress deviation from the target range of the characteristics of the laser light.

[0082] 6. Regarding the method of manufacturing an electronic device FIG. 14 schematically shows a configuration example of the 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) disposed on the reticle stage RT with the laser light incident from the laser device 101. The projection optical system 76 reduces and projects the laser light that has passed through the reticle and forms an image on a workpiece (not shown) disposed on the workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist.

[0083] The exposure apparatus 70 exposes the workpiece with the laser light reflecting the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel. After transferring the reticle pattern to the semiconductor wafer through the exposure process as described above, a semiconductor device can be manufactured through a plurality of processes. The semiconductor device is an example of the "electronic device" in the present disclosure. Instead of the laser device 101, a laser device 102 may be used.

[0084] 7. Others The above description is intended as an illustration and not a limitation. Therefore, it is obvious to those skilled in the art that the embodiments of the present disclosure can be modified without departing from the scope of the claims. It is also obvious to those skilled in the art that the embodiments of the present disclosure can be used in combination.

[0085] The terms used throughout this specification and the claims should be construed as "non-limiting" terms unless otherwise specified. For example, terms such as "comprising", "having", "including", and "containing" should be construed as not excluding the presence of elements other than those described. Also, the modifier "one" should be construed to mean "at least one" or "one or more". Also, the term "at least one of A, B, and C" should be construed as "A", "B", "C", "A + B", "A + C", "B + C", or "A + B + C". Furthermore, it should be construed to include combinations with things other than "A", "B", and "C".

Claims

1. 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, A processor configured to command the charging voltage to the amplifier based on a charging voltage command value commanded from an exposure apparatus, and to 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, A laser device comprising the same.

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

3. The laser device according to claim 1, wherein the processor stores a table in which the repetition frequency, an amount of change in the delay time, and a correction coefficient used for correcting the charging voltage command value are associated with each other, determines the amount of change and the correction coefficient based on the table in response to a change in the repetition frequency, calculates a charging voltage correction value from the determined correction coefficient and the charging voltage command value, and outputs the charging voltage correction value as a command value for commanding the charging voltage of the amplifier. Laser device.

4. The laser device according to claim 3, wherein the correction coefficient includes a first correction coefficient to be multiplied by the charging voltage command value and a second correction coefficient to be added to the product of the charging voltage command value and the first correction coefficient. Laser device.

5. The laser device according to claim 1, wherein 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 an amount of change in the delay time, when the amount of change is ΔD, the first correction coefficient is A(ΔD), the second correction coefficient is B(ΔD), the charging voltage command value commanded from the exposure apparatus is HVcmd, and the charging voltage correction value obtained by the correction is HVcmp, the processor has the following formula, HVcmp = A(ΔD) * HVcmd + B(ΔD) correct the charging voltage command value to determine the charging voltage correction value; laser device.

6. The laser device according to claim 5, wherein 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 commanding the charging voltage, the slope of the linear function is defined as the gain and the intercept is defined as the offset, when the repetition frequency is the first repetition frequency, the delay time is set to the first delay time, when the gain and the offset at the first delay time are α0 and β0, respectively, and when the repetition frequency is changed from the first repetition frequency to the second repetition frequency, the change amount is ΔD, and the gain and the offset, which are functions of the change amount, are α(ΔD) and β(ΔD), respectively, each of the first correction coefficient and the second correction coefficient is determined based on the following equations: A(ΔD) = α0 / α(ΔD) B(ΔD) = (β0 - β(ΔD)) / α(ΔD) laser device.

7. The laser device according to claim 1, wherein the processor also commands the charging voltage to the master oscillator, laser device.

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

9. The laser device according to claim 1, further comprising a pulse energy measuring device that measures the pulse energy of the output laser light output from the amplifier, and the processor commands the charging voltage based on the measurement result of the pulse energy measuring device so that the pulse energy measured using the pulse energy measuring device is within a target range, laser device.

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

11. A laser control method, comprising outputting pulsed laser light from a master oscillator at a first discharge timing synchronized with a repetition frequency, ​ Exciting the laser medium of the amplifier through which the pulsed laser light passes with a charging voltage at a second discharge timing with a delay time added to the first discharge timing to amplify the pulsed laser light; Commanding the charging voltage to the amplifier based on a charging voltage command value commanded from an exposure apparatus; Performing a process of changing the delay time and a process of correcting the charging voltage command value in accordance with the change in the repetition frequency; A laser control method.

12. A method of manufacturing an electronic device, comprising: 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; Commanding the charging voltage to the amplifier based on a charging voltage command value commanded from an exposure apparatus; A processor configured to 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 accordance with the change in the repetition frequency; Generating laser light with a laser device including the same; Outputting the laser light to an exposure apparatus; Exposing a photosensitive substrate with the laser light in the exposure apparatus to manufacture an electronic device. A method of manufacturing an electronic device.

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