Narrow-band laser device and method for manufacturing electronic device

Abstract

A narrow-band laser apparatus according to the present invention comprises: an optical element and a diffraction optical element that are positioned in an optical path of an optical resonator; a wavelength actuator that changes the incidence angle of light incident on the diffraction optical element by moving the optical element; a wavelength driver that drives the wavelength actuator; a processor that outputs a wavelength control signal to the wavelength driver such that the wavelength of pulsed laser light output from the optical resonator periodically changes; and a notch filter that is disposed in the path of the wavelength control signal and operated at a notch frequency different from the drive frequency of the wavelength actuator.

Description

[Technical Field]

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

[0002] In recent years, semiconductor exposure devices have been required to improve their resolution in response to the miniaturization and high integration of semiconductor integrated circuits. To this end, the wavelength of light emitted from exposure light sources has been shortened. For example, KrF excimer laser devices, which output laser light with a wavelength of approximately 248 nm, and ArF excimer laser devices, which output laser light with a wavelength of approximately 193 nm, are used as gas laser devices for exposure.

[0003] The spectral linewidth of the spontaneously oscillating light from KrF excimer laser devices and ArF excimer laser devices is as wide as 350 to 400 pm. Therefore, if a projection lens is constructed using a material that transmits ultraviolet light, such as KrF and ArF laser light, chromatic aberration may occur. As a result, resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from the gas laser device to a level where chromatic aberration can be ignored. Therefore, a line narrowing module (LNM) containing a line narrowing element (e.g., an etalon or grating) may be installed inside the laser resonator of the gas laser device to narrow the spectral linewidth. A gas laser device that narrows the spectral linewidth is called a line narrowing laser device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-276128 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-266624 [Patent Document 3] Japanese Patent Application Publication No. 05-104421 [Patent Document 4] Summary of the specification of U.S. Patent No. 4,963,806

[0005] In one aspect of the present disclosure, a line-narrowing laser device includes an optical element and a diffractive optical element located in the optical path of an optical resonator, a wavelength actuator that changes the angle of incidence of light incident on the diffractive optical element by moving the optical element, a wavelength driver that drives the wavelength actuator, a processor that outputs a wavelength control signal to the wavelength driver so that the wavelength of the pulsed laser light output from the optical resonator changes periodically, and a notch filter that is located in the path of the wavelength control signal and operates at a notch frequency different from the drive frequency of the wavelength actuator.

[0006] In one aspect of the present disclosure, a method for manufacturing an electronic device includes generating pulsed laser light using a narrow-band laser apparatus including an optical element and a diffractive optical element located in an optical path of an optical resonator, a wavelength actuator that changes the angle of incidence of light incident on the diffractive optical element by moving the optical element, a wavelength driver that drives the wavelength actuator, a processor that outputs a wavelength control signal to the wavelength driver so that the wavelength of pulsed laser light output from the optical resonator changes periodically, and a notch filter that is located in a path of the wavelength control signal and operates at a notch frequency different from the drive frequency of the wavelength actuator, outputting the pulsed laser light to an exposure apparatus, and exposing the pulsed laser light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device. [Brief explanation of the drawings]

[0007] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a schematic configuration of an exposure system in a comparative example. [Figure 2] FIG. 2 shows a schematic configuration of a line-narrowed laser device in a comparative example. [Figure 3] FIG. 3 is a graph showing an example in which the target wavelength of the pulsed laser beam is changed periodically. [Figure 4]FIG. 4 is a graph showing the frequency response characteristics of the vibration system of the wavelength oscillation mechanism in the comparative example. [Figure 5] FIG. 5 is a graph showing the spectrum of the vibration frequency of the vibration system of the wavelength oscillation mechanism when the rotation stage is driven at a drive frequency of 1 kHz in the comparative example. [Figure 6] FIG. 6 is a graph showing the relationship between the target wavelength and the measured wavelength in the comparative example. [Figure 7] FIG. 7 shows a schematic configuration of a line-narrowed laser device according to the first embodiment. [Figure 8] FIG. 8 is a circuit diagram illustrating an example of a fixed notch filter included in the first embodiment. [Figure 9] FIG. 9 is a graph showing frequency response characteristics of the vibration system of the wavelength oscillation mechanism and the fixed notch filter in the first embodiment. [Figure 10] FIG. 10 is a graph showing a first example of the relationship between the target wavelength and the measured wavelength in the first embodiment. [Figure 11] FIG. 11 is a circuit diagram illustrating an example of a fixed notch filter included in the second embodiment. [Figure 12] FIG. 12 is a graph showing the frequency response characteristics of the fixed notch filter according to the first embodiment. [Figure 13] FIG. 13 is a graph showing a second example of the relationship between the target wavelength and the measured wavelength in the first embodiment. [Figure 14] FIG. 14 is a graph showing the frequency response characteristics of the fixed notch filter according to the second embodiment. [Figure 15] FIG. 15 is a graph showing an example of the relationship between the target wavelength and the measured wavelength in the second embodiment. [Figure 16] FIG. 16 shows a schematic configuration of a line-narrowed laser device according to the third embodiment. [Figure 17] FIG. 17 is a circuit diagram showing an example of a variable notch filter included in the third embodiment. [Figure 18] FIG. 18 is a circuit diagram illustrating an example of a variable notch filter included in the third embodiment. [Figure 19] FIG. 19 is a graph showing the frequency response characteristics of the vibration system of the wavelength oscillation mechanism and the variable notch filter in the third embodiment. [Figure 20] FIG. 20 is a graph showing an example of the relationship between the target wavelength and the measured wavelength in the third embodiment. [Figure 21] FIG. 21 is a flowchart showing a first example of notch parameter adjustment in the third embodiment. [Figure 22] FIG. 22 is a flowchart showing an example of adjusting the notch frequency in the third embodiment. [Figure 23] FIG. 23 is a flowchart showing an example of adjustment of the notch gain depth in the third embodiment. [Figure 24] FIG. 24 is a flowchart showing a second example of notch parameter adjustment in the third embodiment. Embodiment

[0008] <Contents> 1. Comparative Example 1.1 Exposure system 1.1.1 Configuration 1.1.2 Operation 1.2 Narrow-band laser device 100 1.2.1 Configuration 1.2.2 Operation 1.3 Band-narrowing module14 1.3.1 Configuration 1.3.2 Operation 1.4 Periodic wavelength change 1.5 Issues with the comparative example 2. Narrow-band laser device 100a including fixed notch filter 18a 2.1 Configuration 2.2 Operation 2.3 Effect 3. Fixed notch filter 18b including multiple stages of band-elimination filters 3.1 Configuration 3.2 Operation 3.3 Effect 4. Narrowed-band laser device 100c including variable notch filter 18c 4.1 Configuration 4.2 Operation 4.2.1 Notch parameter adjustment based on deviations Dλ1 and Dλ2 between measurement wavelengths λc1 and λc2 and target wavelengths λt1 and λt2 4.2.1.1 Adjusting the notch frequency Fn 4.2.1.2 Adjusting the notch gain depth Gn 4.2.2 Notch parameter adjustment based on wavelength difference between measurement wavelengths λc1 and λc2 4.3 Variable Notch Filters Including Multistage Bandstop Filters 4.4 Effect 5.Other

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

[0010] 1. Comparative Example 1.1 Exposure system 1 shows a schematic configuration of an exposure system in a comparative example. The comparative example in the present disclosure is a configuration that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges. The exposure system includes a line-narrowed laser apparatus 100 and an exposure apparatus 200. In Fig. 1, the line-narrowed laser apparatus 100 is shown in a simplified form.

[0011] The line-narrowed laser apparatus 100 includes a laser control processor 130. The laser control processor 130 is a processing device including a memory 132 in which a control program is stored and a CPU (central processing unit) 131 that executes the control program. The laser control processor 130 is specially configured or programmed to execute various processes included in the present disclosure. The laser control processor 130 corresponds to the processor in the present disclosure. The line-narrowed laser apparatus 100 is configured to output pulsed laser light toward the exposure apparatus 200.

[0012] 1.1.1 Configuration As shown in FIG. 1, the exposure apparatus 200 includes an illumination optical system 201 , a projection optical system 202 , and an exposure control processor 210 .

[0013] The illumination optical system 201 illuminates a reticle pattern of a reticle (not shown) placed on a reticle stage RT with pulsed laser light incident from the line-narrowed laser device 100 . The projection optical system 202 reduces and projects the pulsed laser light that has passed through the reticle, forming an image on a workpiece (not shown) placed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a resist film.

[0014] The exposure control processor 210 is a processing device that includes a memory 212 that stores a control program, and a CPU 211 that executes the control program. The exposure control processor 210 is specially configured or programmed to execute various processes included in the present disclosure. The exposure control processor 210 oversees the control of the exposure apparatus 200.

[0015] 1.1.2 Operation The exposure control processor 210 transmits various parameters, including the target wavelengths λt1 and λt2 and the voltage command value HV, as well as a trigger signal, to the laser control processor 130. The laser control processor 130 controls the line-narrowed laser device 100 in accordance with these parameters and signals. The target wavelengths λt1 and λt2 are target wavelength values. The target wavelength λt2 is set to be a wavelength greater than the target wavelength λt1.

[0016] The exposure control processor 210 synchronizes the reticle stage RT and the workpiece table WT and translates them in opposite directions, thereby exposing the workpiece to a pulsed laser beam that reflects the reticle pattern. The reticle pattern is transferred onto the semiconductor wafer through this exposure process, after which electronic devices can be manufactured through multiple processes.

[0017] 1.2 Narrow-band laser device 100 1.2.1 Configuration Fig. 2 shows a schematic configuration of a line-narrowed laser apparatus 100 in a comparative example. In Fig. 2, an exposure apparatus 200 is shown in a simplified form, and a V-axis, an H-axis, and a Z-axis that are perpendicular to each other are also shown.

[0018] The line-narrowing laser apparatus 100 is a discharge-pumped laser apparatus, and includes a laser control processor 130 as well as a laser chamber 10, a pulsed power supply 13, a line-narrowing module 14, an output coupling mirror 15, and a wavelength monitor 17. The line-narrowing module 14 and the output coupling mirror 15 form an optical resonator.

[0019] The laser chamber 10 is disposed in the optical path of the optical resonator and is provided with windows 10a and 10b. The laser chamber 10 is equipped with a discharge electrode 11a and a paired discharge electrode (not shown) inside. The discharge electrode (not shown) is positioned so as to overlap with the discharge electrode 11a in the direction of the V axis. The laser chamber 10 is filled with a laser gas containing, for example, argon gas or krypton gas as a rare gas, fluorine gas as a halogen gas, and neon gas as a buffer gas.

[0020] The pulse power supply 13 includes a charger, a charging capacitor, and a switch (not shown). The charger holds electrical energy to be supplied to the charging capacitor and is connected to the charging capacitor. The charging capacitor is connected to the discharge electrode 11a via the switch.

[0021] The line narrowing module 14 includes prisms 41 to 43, a grating 53, a mirror 63, and rotation stages 143 and 163. The rotation stage 143 is connected to the wavelength driver 12, and the rotation stage 163 is connected to the wavelength driver 18. The grating 53 corresponds to the diffractive optical element in this disclosure. The mirror 63 corresponds to the optical element in this disclosure. The rotation stage 163 corresponds to the wavelength actuator in this disclosure. Details of the line narrowing module 14 will be described later. The output coupling mirror 15 is made up of a partial reflection mirror.

[0022] A beam splitter 16 is disposed in the optical path of the pulsed laser beam output from the output coupling mirror 15. The beam splitter 16 transmits a portion of the pulsed laser beam with high transmittance and reflects the other portion. A wavelength monitor 17 is disposed in the optical path of the pulsed laser beam reflected by the beam splitter 16. The wavelength monitor 17 includes an etalon spectrometer (not shown) and is configured to acquire the light intensity distribution of the interference fringes. The radius of the interference fringes depends on the change in wavelength. A shutter 19 is disposed in the optical path of the pulsed laser light that has passed through the beam splitter 16 .

[0023] 1.2.2 Operation The laser control processor 130 acquires various parameters including the target wavelengths λt1 and λt2 and the voltage command value HV from the exposure control processor 210. The laser control processor 130 controls the line narrowing module 14 by outputting wavelength control signals to the wavelength drivers 12 and 18 based on the target wavelengths λt1 and λt2. The laser control processor 130 sets the voltage command value HV in a charger included in the pulsed power supply 13.

[0024] The laser control processor 130 receives a trigger signal from the exposure control processor 210. The laser control processor 130 transmits an oscillation trigger signal based on the trigger signal to the pulsed power supply 13. A switch included in the pulsed power supply 13 turns on when it receives the oscillation trigger signal from the laser control processor 130. When the switch turns on, the pulsed power supply 13 generates a pulsed high voltage from the electrical energy stored in the charger and applies this high voltage to the discharge electrode 11a.

[0025] When a high voltage is applied to the discharge electrode 11a, a discharge occurs in the discharge space between the discharge electrode 11a and another discharge electrode (not shown). The energy of this discharge excites the laser gas in the laser chamber 10 and causes it to transition to a higher energy level. When the excited laser gas subsequently transitions to a lower energy level, it emits light with a wavelength corresponding to the difference in energy levels.

[0026] Light generated within the laser chamber 10 is emitted to the outside of the laser chamber 10 through windows 10a and 10b. The light emitted from the window 10a enters the line narrowing module 14. Of the light that enters the line narrowing module 14, light having a wavelength near the desired wavelength is returned by the line narrowing module 14 to the laser chamber 10.

[0027] The output coupling mirror 15 transmits a portion of the light emitted from the window 10 b and outputs it as pulsed laser light, and reflects the other portion back into the laser chamber 10 .

[0028] In this way, the light emitted from the laser chamber 10 travels back and forth between the line-narrowing module 14 and the output-coupling mirror 15. This light is amplified each time it passes through the discharge space in the laser chamber 10. In addition, this light is narrowed in line each time it is bent back by the line-narrowing module 14, becoming light with a steep wavelength distribution with a central wavelength that is part of the range of wavelengths selected by the line-narrowing module 14. The light thus oscillates and has its line narrowed is output as pulsed laser light from the output-coupling mirror 15. Unless otherwise specified, the wavelength of the pulsed laser light refers to the central wavelength.

[0029] The wavelength monitor 17 transmits the light intensity distribution of the interference fringes generated by the pulsed laser light to the laser control processor 130. The laser control processor 130 calculates the measurement wavelength based on the light intensity distribution of the interference fringes, and outputs wavelength control signals to the wavelength drivers 12 and 18 based on the measured wavelength, thereby feedback-controlling the line-narrowing module 14.

[0030] The shutter 19 is configured to be switchable between a first state in which the pulsed laser light passes through toward the exposure device 200, and a second state in which the pulsed laser light is prevented from passing through to the exposure device 200. The switching between the first state and the second state is controlled by the laser control processor 130.

[0031] The pulsed laser beam that passes through the shutter 19 when the shutter 19 is in the first state is incident on the exposure apparatus 200. An energy monitor (not shown) included in the exposure apparatus 200 measures the pulse energy of the pulsed laser beam. Based on the measured pulse energy and a target pulse energy, the exposure control processor 210 calculates a voltage command value HV and transmits it to the laser control processor 130. The pulse energy of the pulsed laser beam is controlled in accordance with the voltage command value HV.

[0032] 1.3 Band-narrowing module14 1.3.1 Configuration Prisms 41, 42, and 43 are arranged in this order in the optical path of the light beam emitted from window 10a. Prisms 41 to 43 are arranged so that the surfaces of prisms 41 to 43 through which the light beam enters and exits are all parallel to the V axis, and each is supported by a holder (not shown). Prism 43 can be rotated around an axis parallel to the V axis by a rotation stage 143. An example of rotation stage 143 is a rotation stage equipped with a stepping motor and having a large range of motion.

[0033] Mirror 63 is disposed in the optical path of the light beam transmitted through prisms 41 to 43. Mirror 63 is disposed so that the surface that reflects the light beam is parallel to the V axis, and can be rotated around an axis parallel to the V axis by rotation stage 163. An example of rotation stage 163 is a highly responsive rotation stage equipped with a piezoelectric element.

[0034] Alternatively, the prism 42 may be rotatable by the rotation stage 143, the prism 43 may be rotatable by the rotation stage 163, and the mirror 63 may not be rotated. In this case, the prism 43 corresponds to the optical element in the present disclosure.

[0035] Grating 53 is disposed in the optical path of the light beam reflected by mirror 63. The direction of the grooves in grating 53 is parallel to the V axis. Grating 53 is supported by a holder (not shown).

[0036] 1.3.2 Operation The light beam emitted from the window 10a has its traveling direction changed by each of the prisms 41 to 43 in a plane parallel to the HZ plane, which is a plane perpendicular to the V axis, and its beam width is expanded in the plane parallel to the HZ plane. The light beams transmitted through the prisms 41 to 43 are reflected by the mirror 63 and enter the grating 53 .

[0037] The light beam incident on the grating 53 is reflected by the multiple grooves of the grating 53 and diffracted in a direction according to the wavelength of the light. The grating 53 is in a Littrow configuration so that the angle of incidence of the light beam incident on the grating 53 from the mirror 63 matches the diffraction angle of the diffracted light of the desired wavelength.

[0038] The mirror 63 reflects the light returned from the grating 53 toward the prism 43. The prisms 41 to 43 reduce the beam width of the light reflected by the mirror 63 in a plane parallel to the HZ plane, and return the light to the inside of the laser chamber 10 through the window 10a.

[0039] Wavelength drivers 12 and 18 drive rotary stages 143 and 163, respectively, by outputting drive signals based on the wavelength control signals. The angle of incidence of the light beam incident on grating 53 changes depending on the rotation angles of rotary stages 143 and 163, and the wavelength selected by line-narrowing module 14 changes accordingly. Rotary stage 143 is mainly used for coarse adjustment, and rotary stage 163 is mainly used for fine adjustment.

[0040] 1.4 Periodic wavelength change 3 is a graph showing an example in which the target wavelength of a pulsed laser beam is periodically changed, where the horizontal axis represents time and the vertical axis represents the target wavelength. The narrow-band laser device 100 performs laser oscillation at a repetition rate above a certain level for a certain period of time in response to a trigger signal from the exposure control processor 210. Performing laser oscillation at a repetition rate above a certain level and outputting pulsed laser light is called "burst oscillation."

[0041] When the trigger signal from the exposure control processor 210 stops, the line-narrowed laser apparatus 100 stops burst oscillation. After that, in accordance with the trigger signal from the exposure control processor 210, the line-narrowed laser apparatus 100 starts burst oscillation again.

[0042] The period during which burst oscillation is performed corresponds, for example, to the period during which one exposure area of ​​a semiconductor wafer is exposed in exposure apparatus 200. The period during which burst oscillation is paused corresponds, for example, to the period during which the imaging position of the reticle pattern is moved from one exposure area to another exposure area in exposure apparatus 200, or the period during which the semiconductor wafer is replaced. Adjustment oscillation may be performed during the pause period to adjust various parameters.

[0043] The laser control processor 130 controls the rotation stage 163 by outputting a wavelength control signal to the wavelength driver 18 so that the attitude of the mirror 63 changes periodically for each set of pulses, based on the target wavelengths λt1 and λt2 received from the exposure control processor 210. As a result, the wavelength of the pulsed laser light changes periodically for each set of pulses.

[0044] In the example shown in FIG. 3, the wavelength periodically changes every four pulses between the target wavelengths λt1 and λt2. The first and fourth pulses are generated at the target wavelength λt1, and the second and third pulses are generated at the target wavelength λt2. Thereafter, similarly, two pulses are generated at the target wavelength λt1, and two pulses are generated at the target wavelength λt2, and this process is repeated. The wavelength control signal is generated as a square wave, and for example, the wavelength change period is 1 ms, i.e., the frequency of the wavelength control signal is 1 kHz. In this case, the drive signal output from the wavelength driver 18 to the rotation stage 163 is also a square wave with a drive frequency of 1 kHz. The repetition frequency of the pulsed laser light is 4 kHz.

[0045] Although the wavelength of the pulsed laser beam is periodically changed to two target wavelengths λt1 and λt2 in the above description, three or more target wavelengths may be set. In this manner, the line-narrowed laser device 100 can perform two-wavelength oscillation or multi-wavelength oscillation.

[0046] The focal length in the exposure apparatus 200 depends on the wavelength of the pulsed laser beam. Periodic changes in the target wavelength periodically change the imaging position in the direction of the optical path axis of the pulsed laser beam, so that the depth of focus can be effectively increased. For example, even when exposing a thick resist film, imaging performance in the thickness direction of the resist film can be maintained. Alternatively, the resist profile, which indicates the cross-sectional shape of the developed resist film, can be adjusted.

[0047] 1.5 Issues with the comparative example However, if the target wavelength is changed periodically and at high speed, the operation of the rotary stage 163 may not be able to accurately follow the change in the target wavelength, and the wavelength of the pulsed laser light may not be able to be controlled accurately.

[0048] FIG. 4 is a graph showing the frequency response characteristics of the oscillation system of a wavelength oscillation mechanism in a comparative example. The horizontal axis of FIG. 4 represents frequency, and the vertical axis represents gain. The oscillation system of the wavelength oscillation mechanism in this disclosure is an oscillation system that oscillates due to the periodic driving of a wavelength actuator such as the rotation stage 163, and includes the wavelength actuator, a mechanical component that holds the wavelength actuator, an optical element such as the mirror 63 driven by the wavelength actuator, a component that couples the wavelength actuator and the optical element, and a mechanical driving component that transmits a driving force to the optical element. The oscillation system of the wavelength oscillation mechanism has at least one resonance frequency Fr. It is desirable that the oscillation system of the wavelength oscillation mechanism have a resonance frequency Fr higher than the driving frequency of the rotation stage 163. In the example shown in FIG. 4, the resonance frequency Fr is 3 kHz.

[0049] 5 is a graph showing the spectrum of the vibration frequency of the vibration system of the wavelength oscillation mechanism when the rotation stage 163 is driven at a drive frequency of 1 kHz in the comparative example. The horizontal axis of FIG. 5 represents frequency, and the vertical axis represents power spectral density (PSD). When the drive signal input to the rotation stage 163 is a square wave with a drive frequency of 1 kHz, the drive signal is expressed as the sum of frequency components that are odd multiples of the drive frequency through Fourier series expansion. Therefore, the frequency components that are odd multiples of the drive frequency contained in the drive signal may vibrate the oscillation system of the wavelength oscillation mechanism. For example, if 3 kHz, which is an odd multiple of the drive frequency, matches the resonant frequency Fr (see Figure 4), this oscillation system may not only vibrate at the drive frequency of 1 kHz, but also vibrate significantly at 3 kHz.

[0050] Fig. 6 is a graph showing the relationship between the target wavelength and the measured wavelength in a comparative example. The horizontal axis of Fig. 6 shows the pulse number, and the vertical axis shows the wavelength deviation when the average of the target wavelengths λt1 and λt2 is set to 0. When the repetition frequency of the pulsed laser light was set to 4 kHz, the drive frequency of the drive signal input to the rotation stage 163 was set to 1 kHz, and the difference between the target wavelengths λt1 and λt2 was set to 2 pm, the measured wavelength sometimes deviated significantly from the target wavelength.

[0051] 2. Narrow-band laser device 100a including fixed notch filter 18a 2.1 Configuration 7 is a schematic diagram illustrating the configuration of a line-narrowed laser device 100a according to the first embodiment. In the first embodiment, a fixed notch filter 18a is disposed in the path of the wavelength control signal between the laser control processor 130 and the wavelength driver 18. The fixed notch filter 18a is an example of a notch filter according to the present disclosure. A notch filter is an electric circuit that attenuates and passes some frequency components of the wavelength components included in the wavelength control signal.

[0052] 8 is a circuit diagram showing an example of a fixed notch filter 18a included in the first embodiment. The fixed notch filter 18a includes a low-pass filter LPF and a high-pass filter HPF connected in parallel, an operational amplifier OA1 connected to the output sides of the low-pass filter LPF and the high-pass filter HPF, and an operational amplifier OA2 connected to the output side of the operational amplifier OA1.

[0053] The low-pass filter LPF includes resistors R1 and R2 and a capacitor C3, and attenuates high-frequency components of the input signal IN and passes low-frequency components. The high-pass filter HPF includes capacitors C1 and C2 and a resistor R3, and attenuates low-frequency components of the input signal IN and passes high-frequency components.

[0054] The resistance values ​​of the resistor elements R1, R2, and R3 are R1, R2, and R3, respectively, and the relationship is R1=R2=2R3. The capacitance values ​​of the capacitors C1, C2, and C3 are C1, C2, and C3, respectively, and the relationship is C1=C2=C3 / 2.

[0055] The operational amplifier OA1 amplifies and outputs a signal that is a combination of the low-frequency components that have passed through the low-pass filter LPF and the high-frequency components that have passed through the high-pass filter HPF. The frequency that is attenuated by both the low-pass filter LPF and the high-pass filter HPF is called the notch frequency Fn (see FIG. 9), and is given by 1 / (2πC1R1). The fixed notch filter 18a attenuates the frequency component of the notch frequency Fn more than other frequency components and passes it.

[0056] The operational amplifier OA2 positively feeds back a portion of the output signal OUT of the operational amplifier OA1 between the capacitor C3 of the low-pass filter LPF and the resistor element R3 of the high-pass filter HPF. The feedback ratio of the operational amplifier OA2 is determined by the ratio of the resistance values ​​of the resistor elements R4 and R5 that form the voltage divider. By providing the operational amplifier OA2, the gain of frequency components other than the notch frequency Fn of the fixed notch filter 18a can be made closer to zero, thereby making the portion of the curve showing the frequency response characteristics of the fixed notch filter 18a near the notch frequency Fn, which will be described later with reference to FIG. 9, steeper.

[0057] 2.2 Operation FIG. 9 is a graph showing the frequency response characteristics of the vibration system of the wavelength oscillation mechanism and the fixed notch filter 18a in the first embodiment. The frequency response characteristics of the vibration system of the wavelength oscillation mechanism are similar to those shown in FIG. 4, and have a resonance frequency Fr of, for example, 3 kHz.

[0058] The fixed notch filter 18a significantly attenuates the wavelength control signal at the notch frequency Fn and passes the wavelength control signal without significant attenuation in other frequency regions. The notch frequency Fn is a frequency different from the drive frequency of the rotation stage 163, preferably a frequency higher than the drive frequency, and more preferably a frequency that is an odd multiple of the drive frequency. As a result, in the frequency response characteristics of the oscillation system of the wavelength oscillation mechanism driven via the fixed notch filter 18a, the gain at the notch frequency Fn is suppressed.

[0059] The notch frequency Fn is set to, for example, about 3 kHz in accordance with the resonance frequency Fr of the oscillation system of the wavelength oscillation mechanism. In this case, in the frequency response characteristics of the oscillation system of the wavelength oscillation mechanism driven via the fixed notch filter 18a, resonance at the resonance frequency Fr of 3 kHz is suppressed.

[0060] 10 is a graph showing a first example of the relationship between the target wavelength and the measured wavelength in the first embodiment. In the first embodiment, although there is a slight difference between the target wavelength and the measured wavelength at the beginning of the burst, from around the 10th pulse onwards, the measured wavelength does not deviate significantly from the target wavelength and follows the change in the target wavelength well.

[0061] 2.3 Effect (1) According to the first embodiment, the line-narrowed laser device 100a includes a mirror 63, a grating 53, a rotation stage 163, a wavelength driver 18, a laser control processor 130, and a fixed notch filter 18a. The mirror 63 and the grating 53 are located in the optical path of the optical resonator. The rotation stage 163 changes the angle of incidence of light incident on the grating 53 by moving the mirror 63. The wavelength driver 18 drives the rotation stage 163. The laser control processor 130 outputs a wavelength control signal to the wavelength driver 18 so that the wavelength of the pulsed laser light output from the optical resonator changes periodically. The fixed notch filter 18a is located in the path of the wavelength control signal and operates at a notch frequency Fn that is different from the drive frequency of the rotation stage 163. According to this, since the fixed notch filter 18a is placed in the path of the wavelength control signal, the frequency components of the wavelength control signal with a notch frequency Fn that is different from the drive frequency are attenuated by the fixed notch filter 18a, and the periodic wavelength can be accurately changed according to the drive frequency.

[0062] (2) According to the first embodiment, the notch frequency Fn is higher than the drive frequency. According to this, the frequency component of the notch frequency Fn, which is higher than the drive frequency, is attenuated by the fixed notch filter 18a, and the periodic wavelength can be accurately changed according to the drive frequency.

[0063] (3) According to the first embodiment, the notch frequency Fn is an odd multiple greater than one of the drive frequency. According to this, the fixed notch filter 18a attenuates frequency components that are odd multiples of the drive frequency, and periodic wavelength changes can be accurately performed according to the drive frequency.

[0064] (4) According to the first embodiment, the notch frequency Fn is set to match the resonance frequency Fr of the oscillation system of the wavelength oscillation mechanism that oscillates due to the periodic driving of the rotation stage 163. According to this, the resonance frequency Fr of the oscillation system of the wavelength oscillation mechanism is attenuated by the fixed notch filter 18a, thereby suppressing the natural oscillation of the oscillation system, and periodic wavelength change by the drive frequency can be performed accurately. In other respects, the first embodiment is similar to the comparative example.

[0065] 3. Fixed notch filter 18b including multiple stages of band-elimination filters 3.1 Configuration 11 is a circuit diagram showing an example of a fixed notch filter 18b included in the second embodiment. The fixed notch filter 18b includes first and second band elimination filters 181 and 182. The second band elimination filter 182 is connected in series to the output side of the first band elimination filter 181. The configurations of the first and second band elimination filters 181 and 182 are similar to that of the fixed notch filter 18a shown in FIG. 8. The first and second band elimination filters 181 and 182 have the same characteristics, and for example, both have a notch frequency Fn of 1 / (2πC1R1). The notch gain depth Gn, which will be described later, is also the same for the first and second band elimination filters 181 and 182. The fixed notch filter 18b is an example of a notch filter defined in the present disclosure.

[0066] 3.2 Operation Fig. 12 is a graph showing the frequency response characteristics of fixed notch filter 18a in the first embodiment. Fig. 12 corresponds to a re-examination of the frequency response characteristics of fixed notch filter 18a shown in Fig. 9, with the scale of the vertical axis changed. The minimum value of the gain of the notch filter is called the notch gain depth Gn.

[0067] Fig. 13 is a graph showing a second example of the relationship between the target wavelength and the measured wavelength in the first embodiment. The difference between the target wavelengths λt1 and λt2 was 2 pm in the first example shown in Fig. 10, whereas it is about 15 pm in the second example shown in Fig. 13. In the first example, the measured wavelength adequately followed the target wavelength, but in the second example, the difference between the target wavelengths λt1 and λt2 becomes large, so the measured wavelength may not adequately follow the target wavelength.

[0068] 14 is a graph showing the frequency response characteristics of the fixed notch filter 18b in the second embodiment. In the second embodiment, first and second band-elimination filters 181 and 182 similar to the fixed notch filter 18a are connected in series, so that the notch gain depth Gn is larger than that in the first embodiment.

[0069] Fig. 15 is a graph showing an example of the relationship between the target wavelength and the measured wavelength in the second embodiment. The difference between the target wavelengths λt1 and λt2 is about 15 pm, as in Fig. 13. In Fig. 13, there were cases where the measured wavelength could not sufficiently track the target wavelength, but in Fig. 15, the measured wavelength does not deviate significantly from the target wavelength and tracks well with changes in the target wavelength.

[0070] 3.3 Effect (5) According to the second embodiment, the fixed notch filter 18b includes first and second band-elimination filters 181 and 182 connected in series. According to this, by configuring the fixed notch filter 18b with a multi-stage band elimination filter including the first and second band elimination filters 181 and 182, it is possible to increase the notch gain depth Gn.

[0071] (6) According to the second embodiment, the first and second band-elimination filters 181 and 182 operate at the same notch frequency Fn. This makes it possible to increase the notch gain depth Gn at the notch frequency Fn by making the notch frequencies Fn of the first and second band-elimination filters 181 and 182 the same. The notch frequencies Fn being the same means that differences are allowed to the extent that the effect of increasing the notch gain depth Gn is not lost.

[0072] (7) According to the second embodiment, the first and second band-elimination filters 181 and 182 operate with the same notch gain depth Gn. This makes it possible to reduce the manufacturing cost of the circuit by unifying the characteristics of the semiconductor elements that make up the first and second band-elimination filters 181 and 182. The notch gain depths Gn being the same means that differences are allowed to the extent that the effect of reducing the manufacturing cost of the circuit is not lost, and the range of manufacturing error is included in the same range. In other respects, the second embodiment is similar to the first embodiment.

[0073] 4. Narrowed-band laser device 100c including variable notch filter 18c 4.1 Configuration 16 is a schematic diagram illustrating the configuration of a line-narrowed laser device 100c according to the third embodiment. In the third embodiment, a variable notch filter 18c is disposed on the path of the wavelength control signal between the laser control processor 130 and the wavelength driver 18. The variable notch filter 18c is an example of the notch filter defined in the present disclosure.

[0074] FIG. 17 is a circuit diagram showing an example of the variable notch filter 18c included in the third embodiment. The variable notch filter 18c includes variable resistors VR1, VR2, and VR3 instead of the resistive elements R1, R2, and R3, respectively. The variable resistors VR1, VR2, and VR3 are connected to control circuits Cc1, Cc2, and Cc3, respectively. The control circuits Cc1, Cc2, and Cc3 change the resistance values ​​R1, R2, and R3 of the variable resistors VR1, VR2, and VR3, respectively, based on control signals output from the laser control processor 130. For example, the resistance values ​​R1, R2, and R3 are changed while maintaining the relationship R1 = R2 = 2R3. This allows the notch frequency Fn, which is given by 1 / (2πC1R1), to be changed. In other respects, variable notch filter 18c is similar to fixed notch filter 18a.

[0075] Fig. 18 is a circuit diagram showing an example of a variable notch filter 18d included in the third embodiment. The variable notch filter 18d differs from the variable notch filter 18c shown in Fig. 17 in the following respects, but may be used in the line-narrowed laser device 100c instead of the variable notch filter 18c. Variable notch filter 18d includes a variable voltage divider VD instead of resistor elements R4 and R5. Variable voltage divider VD is connected to control circuit Cc4. Control circuit Cc4 changes the voltage division ratio of variable voltage divider VD based on a control signal output from laser control processor 130. Changing the voltage division ratio of variable voltage divider VD changes the feedback factor of operational amplifier OA2, and thereby changes the notch gain depth Gn of variable notch filter 18d.

[0076] When the notch frequency Fn of the variable notch filter 18d is changed by changing the resistance values ​​R1, R2, and R3 of the variable resistors VR1, VR2, and VR3, the phase characteristics of the variable notch filter 18d may change. When the notch frequency Fn is changed, the notch gain depth Gn may be adjusted to further adjust the phase characteristics. On the other hand, even if the notch gain depth Gn is changed by changing the voltage division ratio of the variable voltage divider VD, the notch frequency Fn does not change significantly. Therefore, as will be described later with reference to Figures 21 and 24, after the notch frequency Fn is adjusted to an appropriate value, the notch gain depth Gn may be adjusted while maintaining the notch frequency Fn. In other respects, variable notch filter 18d is similar to variable notch filter 18c.

[0077] 4.2 Operation FIG. 19 is a graph showing the frequency response characteristics of the vibration system of the wavelength oscillation mechanism and the variable notch filter 18c in the third embodiment. The frequency response characteristics of the oscillation system of the wavelength oscillation mechanism may change due to temperature changes in optical elements, mechanical parts, etc. For example, the resonance frequency Fr of the oscillation system of the wavelength oscillation mechanism may change from 3 kHz in Figure 9 to approximately 3.2 kHz as shown in Figure 19. In such a case, if the notch frequency Fn remains at 3 kHz, the component of the resonance frequency Fr may not be sufficiently attenuated in the wavelength control signal.

[0078] Fig. 20 is a graph showing an example of the relationship between the target wavelength and the measured wavelength in the third embodiment. In Fig. 10, the measured wavelength sufficiently follows the target wavelength, but in Fig. 20, there are cases where the measured wavelength cannot sufficiently follow the target wavelength due to a change in the frequency response characteristics of the vibration system of the wavelength oscillation mechanism. Therefore, the notch frequency Fn of the variable notch filter 18c is adjusted, or the notch frequency Fn and notch gain depth Gn of the variable notch filter 18d are adjusted, so that the measured wavelength can sufficiently track the target wavelength.

[0079] 4.2.1 Notch parameter adjustment based on deviations Dλ1 and Dλ2 between measurement wavelengths λc1 and λc2 and target wavelengths λt1 and λt2 FIG. 21 is a flowchart showing a first example of notch parameter adjustment in the third embodiment. The notch parameters include a notch frequency Fn and a notch gain depth Gn. Alternatively, only the notch frequency Fn may be used. In FIG. 21, whether or not the notch parameters are adjusted is determined based on whether or not the deviation Dλ1 between the measured wavelength λc1 and the target wavelength λt1 and the deviation Dλ2 between the measured wavelength λc2 and the target wavelength λt2 remain greater than thresholds Sλ1 and Sλ2, respectively, for Nmax pulses. Nmax is an integer equal to or greater than 2. For example, Nmax may be equal to or greater than 30 and equal to or less than 60.

[0080] In S11, the laser control processor 130 acquires the target wavelengths λt1 and λt2, which may be received from the exposure control processor 210.

[0081] In S12, the laser control processor 130 calculates the threshold values ​​Sλ1 and Sλ2 according to the following equations: Sλ1=λt1×D1 Sλ2=λt2×D2 The threshold values ​​Sλ1 and Sλ2 are obtained by multiplying the target wavelengths λt1 and λt2 by constants D1 and D2, respectively, which are greater than 0. The constants D1 and D2 are, for example, 0.05.

[0082] In S13, the laser control processor 130 sets the value of the counter n to an initial value of 1. In S14, the laser control processor 130 calculates the measured wavelength λc1 or λc2 based on the output of the wavelength monitor 17, and calculates the deviation Dλ1 or Dλ2 from the target wavelength λt1 or λt2 using the following equation. Dλ1=|λt1-λc1| Dλ2=|λt2-λc2| When the line narrowing module 14 is controlled in accordance with the target wavelength λt1, the measurement wavelength λc1 is calculated, and when the line narrowing module 14 is controlled in accordance with the target wavelength λt2, the measurement wavelength λc2 is calculated.

[0083] In S15, the laser control processor 130 determines whether the deviation Dλ1 or Dλ2 is greater than the threshold value Sλ1 or Sλ2, respectively. If the deviation Dλ1 is greater than the threshold value Sλ1 or the deviation Dλ2 is greater than the threshold value Sλ2 (S15: YES), the laser control processor 130 proceeds to S16. If the deviation Dλ1 is equal to or less than the threshold value Sλ1 or the deviation Dλ2 is equal to or less than the threshold value Sλ2 (S15: NO), the laser control processor 130 returns the process to S13.

[0084] In S16, the laser control processor 130 determines whether the value of the counter n is equal to or greater than Nmax. If the value of the counter n is equal to or greater than Nmax (S16: YES), the laser control processor 130 proceeds to S20. If the value of the counter n is less than Nmax (S16: NO), the laser control processor 130 proceeds to S17.

[0085] In S17, the laser control processor 130 adds 1 to the value of the counter n to update the value of n. After S17, the laser control processor 130 returns the process to S14 and calculates the deviation Dλ1 or Dλ2 between the measured wavelength λc1 or λc2 of the next pulse and the target wavelength λt1 or λt2. If the deviation Dλ1 or Dλ2 is greater than the threshold value Sλ1 or Sλ2 (S15: YES), the processes of S14 and S15 are repeated until the value of counter n reaches Nmax, thereby determining whether the state in which the deviations Dλ1 and Dλ2 are greater than the threshold values ​​Sλ1 and Sλ2, respectively, has continued for Nmax pulses. If the deviation Dλ1 is equal to or less than the threshold value Sλ1 or the deviation Dλ2 is equal to or less than the threshold value Sλ2 (S15: NO), the process returns to S13, and the counter n is restarted from 1 when the continuation in which the deviations Dλ1 and Dλ2 are greater than the threshold values ​​Sλ1 and Sλ2, respectively, is broken.

[0086] In S20, the laser control processor 130 adjusts the notch frequency Fn by outputting control signals to the control circuits Cc1 to Cc3 shown in Fig. 17 or 18. Details of S20 will be described later with reference to Fig. 22.

[0087] In S22, the laser control processor 130 adjusts the notch gain depth Gn by outputting a control signal to the control circuit Cc4 shown in Fig. 18. Details of S22 will be described later with reference to Fig. 23. During the period in which S20 and S22 are being executed, the laser control processor 130 may set the shutter 19 to the second state to inhibit the passage of the pulsed laser light to the exposure device 200. After S22, the laser control processor 130 returns the process to S13.

[0088] 4.2.1.1 Adjusting the notch frequency Fn Fig. 22 is a flowchart showing an example of adjusting the notch frequency Fn in the third embodiment. The process shown in Fig. 22 corresponds to the subroutine of S20 in Fig. 21. If the deviations Dλ1 and Dλ2 between the measured wavelengths λc1 and λc2 and the target wavelengths λt1 and λt2 are greater than the thresholds Sλ1 and Sλ2, respectively, for Nmax pulses (S16: YES), the following process is performed.

[0089] In S201, the laser control processor 130 calculates the measured wavelengths λc1 and λc2 based on the new output of the wavelength monitor 17, and calculates the deviation M from the target wavelengths λt1 and λt2 using the following equation. M = |λt1-λc1|+|λt2-λc2| The deviation M serves as a criterion for changing the notch frequency Fn to search for an appropriate notch frequency Fn.

[0090] In S202, the laser control processor 130 increases the notch frequency Fn by the following formula: Fn=Fn+dFnp dFnp indicates the amount of change in the notch frequency Fn when the notch frequency Fn is increased once. For example, dFnp is 1 Hz or more and 10 Hz or less.

[0091] In S203, the laser control processor 130 calculates the measured wavelengths λc1 and λc2 based on the new output of the wavelength monitor 17, and calculates the deviation Mc from the target wavelengths λt1 and λt2 using the following equation. Mc=|λt1-λc1|+|λt2-λc2|

[0092] In S204, the laser control processor 130 determines whether the deviation Mc is equal to or less than the reference deviation M. If the deviation Mc is equal to or less than the deviation M (S204: YES), the laser control processor 130 proceeds to S205.

[0093] In S205, the laser control processor 130 sets the value of the deviation Mc calculated in S203 as the subsequent reference deviation M. After S205, the laser control processor 130 returns the process to S202. In this way, if the deviation Mc becomes smaller or remains unchanged by increasing the notch frequency Fn (S204: YES), the notch frequency Fn can be further increased to adjust the notch frequency Fn until the deviation Mc becomes a minimum value. If the deviation Mc increases as a result of increasing the notch frequency Fn (S204: NO), the notch frequency Fn is not increased further, and the process proceeds to S207.

[0094] In S207, the laser control processor 130 lowers the notch frequency Fn according to the following formula: Fn=Fn-dFnn dFnn indicates the amount of change in the notch frequency Fn when the notch frequency Fn is lowered once. dFnn may be the same as dFnp.

[0095] The processing from S208 to S210 is the same as the processing from S203 to S205. If the deviation Mc is reduced or remains unchanged by lowering the notch frequency Fn (S209: YES), the notch frequency Fn can be further lowered to adjust the notch frequency Fn until the deviation Mc reaches a minimum value. If the deviation Mc increases as a result of lowering the notch frequency Fn (S209: NO), the notch frequency Fn is not further lowered, and the process proceeds to S211.

[0096] In S211, the laser control processor 130 increases the notch frequency Fn by the following formula: Fn=Fn+dFnn The processing of S211 is performed when the deviation Mc becomes large due to lowering the notch frequency Fn in S207, so by canceling one processing of S207, the notch frequency Fn can be adjusted to the optimum value.

[0097] After S211, the laser control processor 130 ends the processing of this flowchart and returns to the processing shown in FIG. In this manner, the laser control processor 130 calculates the deviation Mc by increasing or decreasing the notch frequency Fn, and searches for the notch frequency Fn that makes the deviation Mc approach zero.

[0098] 4.2.1.2 Adjusting the notch gain depth Gn Fig. 23 is a flowchart showing an example of adjustment of the notch gain depth Gn in the third embodiment. The process shown in Fig. 23 corresponds to the subroutine of S22 in Fig. 21. After adjustment of the notch frequency Fn (S20), the following process is performed.

[0099] 23 differs from the processing in FIG. 22 in that the processing in S202d, S207d, and S211d is performed instead of S202, S207, and S211 in FIG.

[0100] In S202d, laser control processor 130 increases the notch gain depth Gn by the following formula: Gn=Gn+dGnp dGnp indicates the amount of fluctuation in the notch gain depth Gn when the notch gain depth Gn is increased once, and is, for example, 1 dB or more and 10 dB or less.

[0101] In S207d, laser control processor 130 decreases the notch gain depth Gn according to the following formula: Gn=Gn-dGnn dGnn indicates the amount of change in the notch gain depth Gn when the notch gain depth Gn is decreased once. dGnn may be the same as dGnp.

[0102] In S211d, laser control processor 130 increases the notch gain depth Gn according to the following formula: Gn=Gn+dGnn By canceling one processing step of S207d, the notch gain depth Gn can be adjusted to an optimum value.

[0103] In this manner, the laser control processor 130 calculates the deviation Mc by increasing or decreasing the notch gain depth Gn, and searches for the notch gain depth Gn that makes the deviation Mc approach zero. In other respects, the process shown in FIG. 23 is similar to the process shown in FIG.

[0104] 4.2.2 Notch parameter adjustment based on wavelength difference between measurement wavelengths λc1 and λc2 Fig. 24 is a flowchart showing a second example of notch parameter adjustment in the third embodiment. In Fig. 24, whether or not to adjust the notch parameters is determined by calculating the wavelength difference between measurement wavelengths λc1 and λc2 Nmax times and determining whether the average value Dλc is greater than a threshold SD.

[0105] The process of S11 is the same as that described with reference to FIG. In S12c, the laser control processor 130 calculates the threshold SD according to the following formula: SD=(λt2-λt1)×D The threshold SD is obtained by multiplying the difference between the target wavelengths λt1 and λt2 by a constant D greater than 1. The constant D is, for example, 1.05.

[0106] In S13c, the laser control processor 130 sets the integrated value Aλc of the wavelength difference to an initial value of 0, and sets the value of the counter n to an initial value of 1. In S14c, the laser control processor 130 calculates the measured wavelengths λc1 and λc2 of two pulses with different target wavelengths based on the output of the wavelength monitor 17, and calculates the integrated value Aλc of the wavelength difference between the measured wavelengths λc1 and λc2 using the following formula. Aλc=Aλc+λc2-λc1

[0107] In S16, the laser control processor 130 determines whether the value of the counter n is equal to or greater than Nmax. If the value of the counter n is equal to or greater than Nmax (S16: YES), the laser control processor 130 proceeds to S18c. If the value of the counter n is less than Nmax (S16: NO), the laser control processor 130 proceeds to S17.

[0108] In S17, the laser control processor 130 adds 1 to the value of the counter n to update the value of n. After S17, the laser control processor 130 returns the process to S14c and adds the wavelength difference λc2-λc1 between the measured wavelengths λc1 and λc2 of the next two pulses having different target wavelengths to the integrated value Aλc.

[0109] In S18c, the laser control processor 130 calculates an average value Dλc of the wavelength differences by the following formula using an integrated value Aλc obtained by integrating the wavelength difference λc2−λc1 calculated Nmax times. Dλc=Aλc / Nmax

[0110] In S19c, the laser control processor 130 determines whether the average wavelength difference Dλc is greater than the threshold SD. If the average wavelength difference Dλc is greater than the threshold SD (S19c: YES), the laser control processor 130 proceeds to S20. If the average wavelength difference Dλc is equal to or less than the threshold SD (S19c: NO), the laser control processor 130 returns to S13c.

[0111] The processes in S20 and S22 are similar to those described with reference to FIGS. In Fig. 24, the notch parameters are adjusted when the average value Dλc of the wavelength differences is greater than the threshold SD, whereas in Fig. 22 and Fig. 23, the notch parameters are adjusted without taking into consideration the average value Dλc of the wavelength differences. After adjusting the notch parameters, it is possible to check whether the notch parameters have been adjusted appropriately by performing the processes of S13c to S19c again.

[0112] Alternatively, in S201, S203, and S208 of Fig. 22 and S201d, S203d, and S208d of Fig. 23, instead of calculating the deviations Dλ1 and Dλ2 between the measurement wavelengths λc1 and λc2 and the target wavelengths λt1 and λt2, the average value Dλc of the wavelength difference between the measurement wavelengths λc1 and λc2 may be calculated. For example, the laser control processor 130 may increase or decrease the notch frequency Fn to calculate the average value Dλc of the wavelength difference and search for the notch frequency Fn at which the average value Dλc approaches a minimum value. Alternatively, the laser control processor 130 may increase or decrease the notch gain depth Gn to calculate the average value Dλc of the wavelength difference and search for the notch gain depth Gn at which the average value Dλc approaches a minimum value.

[0113] 24 illustrates a case where the average value Dλc is calculated every Nmax times when the wavelength difference between the measurement wavelengths λc1 and λc2 is calculated, but a moving average may be calculated instead of the average value Dλc. For example, every time the wavelength difference is calculated, the average value of the wavelength differences for the most recent Nmax times may be calculated. In other respects, the process shown in FIG. 24 is similar to the process shown in FIG.

[0114] In the third embodiment, the notch parameters may be adjusted when both the conditions regarding the deviations Dλ1 and Dλ2 between the measured wavelengths λc1 and λc2 and the target wavelengths λt1 and λt2 shown in FIG. 21 and the conditions regarding the average value Dλc of the wavelength difference between the measured wavelengths λc1 and λc2 shown in FIG. 24 are satisfied.

[0115] 4.3 Variable Notch Filters Including Multistage Bandstop Filters In the third embodiment, the variable notch filters 18c and 18d are each configured as a single-stage band-elimination filter. However, the present disclosure is not limited to this. Instead of the variable notch filters 18c and 18d, a variable notch filter including first and second band-elimination filters (not shown) connected in series may be used. The notch parameters of the first and second band-elimination filters may be adjustable by the laser control processor 130. The laser control processor 130 may adjust the first and second band-elimination filters so that they operate at the same notch frequency Fn. The laser control processor 130 may adjust the first and second band-elimination filters so that they operate at the same notch gain depth Gn.

[0116] 4.4 Effect (8) According to the third embodiment, the variable notch filter 18c or 18d included in the line-narrowed laser device 100c is configured so that the notch parameters can be adjusted by the laser control processor . According to this, by making the notch parameters variable, it is possible to accurately change the wavelength periodically in response to changes in the characteristics of the line-narrowed laser device 100c.

[0117] (9) According to the third embodiment, the notch parameters include a notch frequency Fn and a notch gain depth Gn, and the laser control processor 130 adjusts the notch gain depth Gn after adjusting the notch frequency Fn. Although changing the notch frequency Fn may change the phase characteristics, adjusting the notch gain depth Gn makes it possible to adjust the phase characteristics. On the other hand, since changing the notch gain depth Gn does not change the notch frequency Fn significantly, adjusting the notch frequency Fn first and then adjusting the notch gain depth Gn makes it possible to appropriately adjust the notch frequency Fn and notch gain depth Gn.

[0118] (10) According to the third embodiment, the narrow-band laser device 100c includes a wavelength monitor 17 located in the optical path of the pulsed laser light, and the laser control processor 130 calculates the measured wavelengths λc1 and λc2 of the pulsed laser light based on the output of the wavelength monitor 17, and adjusts the notch parameters based on the measured wavelengths λc1 and λc2. This allows the wavelengths to be changed periodically and accurately in response to changes in the measurement wavelengths λc1 and λc2 caused by changes in the characteristics of the line-narrowed laser device 100c.

[0119] (11) According to the third embodiment, the laser control processor 130 calculates the deviations Dλ1 and Dλ2 between the measured wavelengths λc1 and λc2 and the target wavelengths λt1 and λt2 of the pulsed laser beam, and adjusts the notch parameters based on the deviations Dλ1 and Dλ2. This allows the wavelength to be changed periodically and accurately in response to changes in the deviations Dλ1 and Dλ2 caused by changes in the characteristics of the line-narrowed laser device 100c.

[0120] (12) According to the third embodiment, the laser control processor 130 compares the deviations Dλ1 and Dλ2 with the thresholds Sλ1 and Sλ2, and adjusts the notch parameters if there are Nmax consecutive pulses in which the deviations Dλ1 and Dλ2 are greater than the thresholds Sλ1 and Sλ2, respectively. According to this, when the deviations Dλ1 and Dλ2 are large, the notch parameters can be adjusted to reduce the deviations Dλ1 and Dλ2.

[0121] (13) According to the third embodiment, the notch parameters include a notch frequency Fn, and the laser control processor 130 increases or decreases the notch frequency Fn to calculate the deviation Mc between the measured wavelengths λc1 and λc2 and the target wavelengths λt1 and λt2, and searches for a notch frequency Fn that makes the deviation Mc approach zero. According to this, by searching for a notch frequency Fn that makes the deviation Mc approach 0, it is possible to find an appropriate notch frequency Fn that corresponds to the change in the characteristics of the line-narrowed laser device 100c.

[0122] (14) According to the third embodiment, the notch parameters include a notch gain depth Gn, and the laser control processor 130 increases or decreases the notch gain depth Gn to calculate the deviation Mc, and searches for the notch gain depth Gn such that the deviation Mc approaches 0. According to this, by searching for a notch gain depth Gn that makes the deviation Mc approach 0, it is possible to find an appropriate notch gain depth Gn that corresponds to the change in the characteristics of the line-narrowed laser device 100c.

[0123] (15) According to the third embodiment, the laser control processor 130 calculates the wavelength difference between the measured wavelengths λc1 and λc2 of a plurality of pulses of pulsed laser light having different target wavelengths, and adjusts the notch parameters based on the wavelength difference. This allows accurate periodic wavelength changes to be performed in response to changes in the wavelength difference between the measurement wavelengths λc1 and λc2 of the multiple pulses caused by changes in the characteristics of the line-narrowed laser device 100c.

[0124] (16) According to the third embodiment, the laser control processor 130 calculates the wavelength difference between the measurement wavelengths λc1 and λc2 multiple times to calculate the average value Dλc of the wavelength differences, and adjusts the notch parameters if the average value Dλc is greater than the threshold value SD. According to this, when the average value Dλc of the wavelength differences is large, the notch parameters can be adjusted to reduce the average value Dλc of the wavelength differences.

[0125] (17) According to a third embodiment, the notch filter includes first and second band-stop filters connected in series, and the first and second band-stop filters are configured so that the notch parameters of each can be adjusted by the laser control processor 130. According to this, by connecting the first and second band-elimination filters in series and making the notch parameters adjustable for each, the dynamic range of the notch parameters can be increased.

[0126] (18) According to a third embodiment, the laser control processor 130 adjusts the notch parameters so that the first and second band-stop filters operate at the same notch frequency Fn. According to this, by adjusting the notch parameters so as to act at the same notch frequency Fn, it is possible to increase the notch gain depth Gn at the notch frequency Fn.

[0127] (19) According to a third embodiment, the laser control processor 130 adjusts the notch parameters so that the first and second bandstop filters operate with the same notch gain depth Gn. According to this, by making the notch gain depth Gn the same, it is possible to easily adjust the notch parameters. In other respects, the third embodiment is similar to the first embodiment.

[0128] 5.Other The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0129] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, words such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Furthermore, it should be construed as including combinations of these with elements other than "A," "B," and "C."

Claims

1. an optical element and a diffractive optical element located in an optical path of the optical resonator; a wavelength actuator that changes the angle of incidence of light incident on the diffractive optical element by moving the optical element; a wavelength driver that drives the wavelength actuator; a processor that outputs a wavelength control signal to the wavelength driver so that the wavelength of the pulsed laser light output from the optical resonator changes periodically; a notch filter disposed in a path of the wavelength control signal and operating at a notch frequency different from a drive frequency of the wavelength actuator; A narrow-band laser device comprising:

2. 2. The line-narrowed laser device according to claim 1, The notch frequency is a frequency higher than the drive frequency. Narrow-band laser device.

3. 2. The line-narrowed laser device according to claim 1, the notch frequency is an odd multiple greater than one of the drive frequency; Narrow-band laser device.

4. 2. The line-narrowed laser device according to claim 1, the notch frequency is set in accordance with a resonance frequency of a vibration system of a wavelength oscillation mechanism that vibrates due to periodic driving of the wavelength actuator. Narrow-band laser device.

5. 2. The line-narrowed laser device according to claim 1, the notch filter includes first and second band-stop filters connected in series; Narrow-band laser device.

6. 6. The line-narrowed laser device according to claim 5, the first and second band-stop filters operate at the same notch frequency; Narrow-band laser device.

7. 7. The line-narrowed laser device according to claim 6, the first and second band-stop filters operate at the same notch gain depth; Narrow-band laser device.

8. 2. The line-narrowed laser device according to claim 1, the notch filter is configured so that notch parameters can be adjusted by the processor; Narrow-band laser device.

9. 9. The line-narrowed laser device according to claim 8, the notch parameters include the notch frequency and notch gain depth; the processor adjusts the notch gain depth after adjusting the notch frequency. Narrow-band laser device.

10. 9. The line-narrowed laser device according to claim 8, further comprising a wavelength monitor located in an optical path of the pulsed laser beam, the processor calculates a measured wavelength of the pulsed laser beam based on an output of the wavelength monitor, and adjusts the notch parameter based on the measured wavelength. Narrow-band laser device.

11. 11. The line-narrowed laser device according to claim 10, the processor calculates a deviation between the measured wavelength and the target wavelength of the pulsed laser beam, and adjusts the notch parameter based on the deviation. Narrow-band laser device.

12. 12. The line-narrowed laser device according to claim 11, the processor compares the deviation with a threshold value, and adjusts the notch parameter when a predetermined number of consecutive pulses have the deviation greater than the threshold value. Narrow-band laser device.

13. 13. The line-narrowed laser device according to claim 12, the notch parameters include the notch frequency; the processor calculates the deviation by increasing or decreasing the notch frequency, and searches for the notch frequency at which the deviation approaches zero. Narrow-band laser device.

14. 13. The line-narrowed laser device according to claim 12, the notch parameters further include a notch gain depth; the processor calculates the deviation by increasing or decreasing the notch gain depth, and searches for the notch gain depth at which the deviation approaches 0; Narrow-band laser device.

15. 11. The line-narrowed laser device according to claim 10, the processor calculates a wavelength difference between the measured wavelengths of a plurality of pulses of the pulsed laser beam having different target wavelengths, and adjusts the notch parameter based on the wavelength difference. Narrow-band laser device.

16. 16. The line-narrowed laser device according to claim 15, the processor calculates the wavelength difference multiple times to calculate an average value of the wavelength difference, and adjusts the notch parameter if the average value is greater than a threshold. Narrow-band laser device.

17. 2. The line-narrowed laser device according to claim 1, the notch filter includes first and second band-stop filters connected in series; the first and second band-elimination filters are configured so that notch parameters thereof can be adjusted by the processor; Narrow-band laser device.

18. 18. The line-narrowed laser device according to claim 17, the processor adjusts the notch parameters so that the first and second band-stop filters operate at the same notch frequency. Narrow-band laser device.

19. 19. The line-narrowed laser device according to claim 18, the processor adjusts the notch parameters so that the first and second band-stop filters operate with the same notch gain depth. Narrow-band laser device.

20. A method for manufacturing an electronic device, comprising: an optical element and a diffractive optical element located in an optical path of the optical resonator; a wavelength actuator that changes the angle of incidence of light incident on the diffractive optical element by moving the optical element; a wavelength driver that drives the wavelength actuator; a processor that outputs a wavelength control signal to the wavelength driver so that the wavelength of the pulsed laser light output from the optical resonator changes periodically; a notch filter disposed in a path of the wavelength control signal and operating at a notch frequency different from a drive frequency of the wavelength actuator; The pulsed laser light is generated by a line-narrowed laser device comprising: outputting the pulsed laser light to an exposure device; In order to manufacture the electronic device, a photosensitive substrate is exposed to the pulsed laser light in the exposure apparatus. A method for manufacturing an electronic device, comprising:

Images