Laser apparatus, method for controlling wavelength of laser apparatus, and method for manufacturing electronic device

Abstract

This laser apparatus comprises: a first semiconductor laser that outputs a continuously-oscillated first seed laser beam having a first wavelength; a second semiconductor laser that outputs a continuously-oscillated second seed laser beam having a second wavelength different from the first wavelength; an optical switch that outputs one seed laser beam selected from the first seed laser beam and the second seed laser beam as a selected seed laser beam; a first solid-state amplifier that performs pulsing and amplification of the selected seed laser beam and outputs a first pulsed laser beam; a wavelength conversion system that outputs a second pulsed laser beam by wavelength conversion using the first pulsed laser beam; an excimer amplifier that amplifies the second pulsed laser beam and outputs a third pulsed laser beam; and a processor that, on the basis of a target wavelength, selects one seed laser beam from the first seed laser beam and the second seed laser beam as a selected seed laser beam, and controls, such that the wavelength of the third pulsed laser beam becomes the target wavelength and on the basis of the wavelength of the third pulsed laser beam measured by a beam characteristic measuring instrument, the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser beam.

Description

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

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

[0002] In recent years, semiconductor exposure apparatuses 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 that output laser light with a wavelength of approximately 248 nm and ArF excimer laser devices that 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, constructing a projection lens using a material that transmits ultraviolet light, such as KrF and ArF laser light, can result in chromatic aberration. This can result in a decrease in resolution. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from a gas laser device to a level where chromatic aberration is negligible. Therefore, a line narrowing module (LNM) containing a line narrowing element (e.g., an etalon or grating) may be installed within the laser resonator of the gas laser device to narrow the spectral linewidth. Hereinafter, a gas laser device with a narrowed spectral linewidth is referred to as a line narrowing gas laser device.

[0004] International Publication No. WO 2023 / 013025 International Publication No. WO 2022 / 249444 overview

[0005] A laser device according to one aspect of the present disclosure includes a first semiconductor laser that outputs a first seed laser beam of continuous oscillation having a first wavelength, a second semiconductor laser that outputs a second seed laser beam of continuous oscillation having a second wavelength different from the first wavelength, an optical switch that outputs one seed laser beam selected from the first seed laser beam and the second seed laser beam as a selected seed laser beam, a first solid-state amplifier that pulses and amplifies the selected seed laser beam to output a first pulsed laser beam, and a second solid-state amplifier that outputs a second pulsed laser beam by wavelength conversion using the first pulsed laser beam. the wavelength conversion system includes: an excimer amplifier that amplifies the second pulsed laser beam and outputs a third pulsed laser beam; a beam characteristic measuring instrument that measures the wavelength of the third pulsed laser beam; and a processor that selects one of the first seed laser beam and the second seed laser beam as a selected seed laser beam based on a target wavelength, and controls the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser beam based on the wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser beam becomes the target wavelength.

[0006] A wavelength control method for a laser device according to one aspect of the present disclosure includes: outputting a first seed laser beam of continuous oscillation having a first wavelength from a first semiconductor laser; outputting a second seed laser beam of continuous oscillation having a second wavelength different from the first wavelength from a second semiconductor laser; outputting one seed laser beam selected from the first seed laser beam and the second seed laser beam as a selected seed laser beam from an optical switch; pulsating and amplifying the selected seed laser beam by a first solid-state amplifier to output a first pulsed laser beam; outputting a second pulsed laser beam by wavelength conversion; amplifying the second pulsed laser beam by an excimer amplifier to output a third pulsed laser beam; measuring the wavelength of the third pulsed laser beam by a beam characteristic measuring instrument; selecting one of the first seed laser beam and the second seed laser beam as a selected seed laser beam based on the target wavelength; and controlling the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser beam based on the wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser beam becomes the target wavelength.

[0007] A method for manufacturing an electronic device according to one aspect of the present disclosure includes a first semiconductor laser that outputs a first seed laser beam of continuous oscillation having a first wavelength, a second semiconductor laser that outputs a second seed laser beam of continuous oscillation having a second wavelength different from the first wavelength, an optical switch that selects one of the first seed laser beam and the second seed laser beam and outputs it as a selected seed laser beam, a first solid-state amplifier that pulses and amplifies the selected seed laser beam to output a first pulsed laser beam, a wavelength conversion system that performs wavelength conversion using the first pulsed laser beam to output a second pulsed laser beam, and a second semiconductor laser that amplifies the second pulsed laser beam to output a third pulsed laser beam. The method includes generating laser light using a laser apparatus including an excimer amplifier that outputs laser light, a beam characteristic measuring instrument that measures the wavelength of the third pulsed laser light, and a processor that selects one of the first seed laser light and the second seed laser light as a selected seed laser light based on a target wavelength, and controls the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser light based on the wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser light becomes the target wavelength, outputting the laser light to an exposure apparatus, and exposing the laser light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device.

[0008] Some embodiments of the present disclosure are described below, by way of example only, with reference to the accompanying drawings. FIG. 1 is a graph illustrating two-wavelength parameters in dual-wavelength exposure. FIG. 2 is a diagram schematically illustrating the configuration of an exposure system. FIG. 3 is a top view illustrating the configuration of a laser apparatus of a comparative example. FIG. 4 is a side view illustrating the configuration of a laser apparatus of a comparative example. FIG. 5 is a diagram schematically illustrating the configuration of a laser apparatus according to a first embodiment. FIG. 6 is an explanatory diagram illustrating an example of changing the wavelength per pulse using an optical switch. FIG. 7 is an explanatory diagram illustrating an example of changing the wavelength every four pulses using an optical switch. FIG. 8 is a flowchart illustrating example 1 of a processing procedure of a laser control processor according to the first embodiment. FIG. 9 is a flowchart illustrating example 2 of a processing procedure of a laser control processor according to the first embodiment. FIG. 10 is a diagram schematically illustrating the configuration of a distributed feedback semiconductor laser. FIG. 11 is a diagram schematically illustrating the configuration of a wavelength conversion system. FIG. 12 is a graph illustrating wavelength conversion efficiency curves for a KBBF crystal and an LBO crystal. FIG. 13 is a flowchart illustrating an example of control of the angle of incidence of a nonlinear crystal performed by a laser control processor. FIG. 14 is a graph showing the relationship between the wavelength after excimer amplification and the wavelength conversion efficiency. FIG. 15 is a graph showing the relationship between the wavelength after excimer amplification and the wavelength conversion efficiency. FIG. 16 is a graph showing an example of controlling the incident angle to correspond to the target center wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the KBBF crystal and the incident angle at which the wavelength conversion efficiency is maximized. FIG. 17 is a graph showing an example of controlling the incident angle to correspond to the target short wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the KBBF crystal and the incident angle at which the wavelength conversion efficiency is maximized. FIG. 18 is a graph showing an example of controlling the incident angle to correspond to the target long wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the KBBF crystal and the incident angle at which the wavelength conversion efficiency is maximized. FIG. 19 is a diagram schematically showing the configuration of a solid-state seeder applied to the laser device according to the second embodiment. FIG. 20 is a graph showing an example of controlling the incident angle to correspond to the target center wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the second CLBO crystal and the incident angle at which the wavelength conversion efficiency is maximized.Fig. 21 is a graph showing an example of controlling the incident angle to correspond to a target short wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the second CLBO crystal and the incident angle at which the wavelength conversion efficiency is maximized. Fig. 22 is a graph showing an example of controlling the incident angle to correspond to a target long wavelength after wavelength conversion based on the relationship between the wavelength after wavelength conversion of the second CLBO crystal and the incident angle at which the wavelength conversion efficiency is maximized. Fig. 23 is a diagram showing a schematic configuration of an exposure apparatus. Embodiment

[0009] -Table of Contents- 1. Explanation of Terms 2. Comparative Example 2.1 Exposure System 2.1.1 Configuration 2.1.2 Operation 2.2 Laser Apparatus 2.2.1 Configuration 2.2.2 Operation 3. Issues 4. First Embodiment 4.1 Laser Apparatus 4.1.1 Configuration 4.1.2 Operation 4.1.2.1 Example of Wavelength Control Method 1 4.1.2.2 Example of Wavelength Control Method 2 4.2 Example of Semiconductor Laser 4.2.1 Configuration 4.2.2 Operation 4.3 Example of Wavelength Conversion System 4.3.1 Configuration 4.3.2 Operation 4.3.3 Method of Controlling Incident Angle of Nonlinear Crystal 4.3.3.1 Example Flowchart 4.3.3.2 Operation 4.4 Actions and Effects 5. Second Embodiment 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 6. 7. Others Embodiments of the present disclosure will be described in detail below with reference to the drawings. The embodiments described below illustrate 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 to the configurations and operations of the present disclosure. Note that the same components are designated by the same reference symbols, and redundant explanations will be omitted.

[0010] 1. Explanation of Terms In this specification, "two-wavelength exposure" refers to a method in which the wavelength is changed from λ to λ every pulse or every few pulses. S and λ L By switching the laser beam to oscillate, exposure is performed so that the integrated exposure spectrum has two peaks.

[0011] 1 is a graph for explaining two-wavelength parameters in dual-wavelength exposure. In FIG. 1, the horizontal axis represents wavelength λ and the vertical axis represents light intensity In. As shown in FIG. 1, the wavelength on the shorter wavelength side in dual-wavelength exposure is λ S , the wavelength on the long wavelength side is λ L The central wavelength λc of the two-wavelength spectrum is λc = (λ L +λ S ) / 2.

[0012] 2. Comparative Example 2.1 Exposure System 2.1.1 Configuration Figure 2 is a diagram that shows a schematic configuration of an exposure system. The exposure system includes a laser apparatus 10, an exposure apparatus 300, and a beam delivery unit (BDU) 302. The laser apparatus 10 includes a laser control processor 12. In this specification, a processor refers to a processing device that includes a storage device that stores a control program and a CPU (Central Processing Unit) that executes the control program. The processor is specially configured or programmed to perform various processes included in this disclosure.

[0013] The laser device 10 is configured to output pulsed laser light, the oscillation wavelength of which can be changed, toward the exposure device 300. The configuration of the laser device 10 will be described later (FIGS. 3 and 4).

[0014] The exposure apparatus 300 includes a high-reflection mirror 304, an illumination optical system 306, a reticle stage RT, a projection optical system 308, a wafer stage WS, and an exposure control processor 310. A wafer holder WH is provided on the wafer stage WS, and a wafer W is placed on the wafer holder WH.

[0015] The BDU 302 is an optical system that transmits pulsed laser light from the laser device 10 to the exposure device 300. The high-reflection mirror 304 is disposed so that the pulsed laser light that has passed through the BDU 302 enters the illumination optical system 306.

[0016] The illumination optical system 306 is an optical system that shapes the pulsed laser light beam incident from the laser device 10 and guides it to the reticle R placed on the reticle stage RT. The illumination optical system 306 shapes the pulsed laser light beam so that it has a beam shape with a generally rectangular cross section and a generally uniform light intensity distribution, and illuminates the reticle pattern on the reticle R. The projection optical system 308 reduces and projects the pulsed laser light that has passed through the reticle R, forming an image on the wafer W on the wafer holder WH. The wafer W is a photosensitive substrate such as a semiconductor wafer coated with a resist film.

[0017] The exposure control processor 310 is a processing device that includes a storage device in which a control program is stored and a CPU that executes the control program. The exposure control processor 310 oversees the control of the exposure apparatus 300. The exposure control processor 310 is connected to the reticle stage RT and the wafer stage WS. The exposure control processor 310 is also connected to the laser control processor 12.

[0018] 2.1.2 Operation It is known that when resist is exposed and processed with a multi-wavelength (for example, two-wavelength) pulse having peak intensities at multiple central wavelengths, a deep depth of focus can be obtained and processing accuracy can be improved.

[0019] The exposure control processor 310 determines the target short wavelength λ S t and target long wavelength λ L The laser control processor 12 transmits various parameters including the pulse energy Et and the target pulse energy Et, as well as a light emission trigger signal Tr, to the laser control processor 12. The laser control processor 12 controls the laser device 10 in accordance with these parameters and signals. That is, the laser control processor 12 controls the laser device 10 so that the wavelength λ of the pulse laser light output from the laser device 10 is equal to or shorter than the target short wavelength λ. S t or target long wavelength λ L The target wavelength is periodically changed to control the oscillation wavelength so that the wavelength becomes equal to t, and the excitation intensity is controlled so that the pulse energy E becomes equal to the target pulse energy Et, and pulse laser light is output in accordance with the light emission trigger signal Tr.

[0020] In this way, the laser device 10 outputs pulsed laser light of two wavelengths, which has been controlled to have the target wavelengths, to the exposure device 300 in accordance with the light emission trigger signal Tr.

[0021] The exposure control processor 310 synchronizes the reticle stage RT and the wafer holder WH on the wafer stage WS and translates them in opposite directions, thereby exposing the wafer W to pulsed laser light that reflects the reticle pattern.

[0022] 3 and 4 are a top view and a side view showing the configuration of a laser device 10 according to 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.

[0023] The laser apparatus 10 shown in Figures 3 and 4 is a wavelength-tunable, narrow-band excimer laser apparatus, and includes a chamber 14, a power supply 17, a line-narrowing module (LNM) 20, an output coupling mirror 30, a beam characteristic measuring instrument 34, and a laser control processor 12.

[0024] The output coupling mirror 30 and the LMN 20 together constitute an optical resonator, and the chamber 14 is disposed on the optical path of the optical resonator.

[0025] The LMN 20 includes multiple (e.g., two) prisms 22 and 24, a rotation stage 26, and a grating 28. The prisms 22 and 24 and the grating 28 are supported by holders 22 a, 24 a, and 28 a, respectively. The prisms 22 and 24 are arranged to function as a beam expander. The grating 28 is Littrow-aligned so that the angle of incidence and the angle of diffraction match.

[0026] The prism 24 is placed on a rotation stage 26 that rotates the prism 24 about an axis parallel to the V axis, and is positioned so that the angle of incidence on the grating 28 changes as the prism 24 rotates.

[0027] The chamber 14 includes windows 16 a and 16 b and a pair of electrodes 18 a and 18 b. The chamber 14 is filled with a laser gas including Ar gas or Kr gas as a rare gas, F gas as a halogen gas, and Ne gas as a buffer gas.

[0028] The power supply 17 is a pulse power module (PPM) and includes a switch and a charging capacitor (not shown). The laser device 10 includes a charger (not shown), which charges the charging capacitor of the power supply 17 in accordance with commands from the laser control processor 12. The power supply 17 is connected so that a high voltage is applied between the electrodes 18a and 18b when the switch is turned on.

[0029] The electrodes 18a and 18b are arranged in the chamber 14 to face each other in the V direction, with the longitudinal direction of the electrodes 18a and 18b coinciding with the direction of the optical path of the optical resonator.

[0030] The windows 16a and 16b are arranged so that pulsed laser light amplified by discharge excitation between the electrodes 18a and 18b can pass through them.

[0031] The output coupling mirror 30 is coated with a film that reflects part of the pulsed laser light and transmits part of it.

[0032] The beam characteristic measuring instrument 34 includes a first beam splitter 36 , a second beam splitter 38 , a spectral detector 40 , and an energy detector 42 .

[0033] The first beam splitter 36 is disposed on the optical path of the pulsed laser light output from the output coupling mirror 30 so that the pulsed laser light reflected by the first beam splitter 36 enters the second beam splitter 38 .

[0034] The second beam splitter 38 is positioned so that the pulsed laser light reflected by the second beam splitter 38 enters the spectrum detector 40, and so that the pulsed laser light transmitted through the second beam splitter 38 enters the energy detector 42.

[0035] The spectrum detector 40 monitors the spectrum of the incident pulsed laser beam and detects the wavelength of the incident pulsed laser beam. The spectrum detector 40 may be, for example, an etalon spectrometer. The etalon spectrometer includes a diffuser plate that diffuses the sample light, an etalon, a condenser lens disposed on the exit side of the etalon, and a photodiode array disposed on the focal plane of the condenser lens to detect the pattern of interference fringes, and can detect the wavelength by measuring the diameter of the interference fringes.

[0036] The energy detector 42 includes an optical sensor (not shown). The optical sensor may be a photodiode that is resistant to ultraviolet light and has excellent high-speed response. The optical sensor detects the pulse energy of the incident pulse laser light.

[0037] The laser device 10 is equipped with an exit shutter (not shown) downstream of the beam characteristic measuring instrument 34. The exit shutter is disposed on the optical path of the pulsed laser light output from the laser device 10 to the outside, and is configured to be able to output the pulsed laser light to the outside and to block the light. The pulsed laser light that has passed through the first beam splitter 36 is emitted from the laser device 10 via the exit shutter.

[0038] 2.2.2 Operation The laser control processor 12 receives the target short wavelength λ from the exposure device 300. S t, target long wavelength λ L The laser control processor 12 also receives a light emission trigger signal Tr.

[0039] The laser control processor 12 turns on the switch of the power supply 17 based on the light emission trigger signal Tr received from the exposure device 300 .

[0040] When the switch of the power supply 17 is turned on, a high voltage is applied between the electrodes 18a and 18b, and when a discharge occurs between the electrodes 18a and 18b, the laser gas is excited.

[0041] When the laser gas is excited, the optical resonator causes a narrow-band pulsed laser beam to be output from the output coupling mirror 30. The wavelength of the pulsed laser beam is, for example, an ultraviolet wavelength of 150 nm to 380 nm.

[0042] The energy detector 42 detects the pulse energy of the pulsed laser light output from the output coupling mirror 30. The laser control processor 12 calculates the pulse energy E based on the detection result received from the energy detector 42. The laser control processor 12 controls the voltage of the high voltage pulse applied between the electrodes 18 a and 18 b so that the pulse energy E based on the detection result of the energy detector 42 becomes the target pulse energy Et.

[0043] The spectrum detector 40 detects the spectral linewidth and wavelength of the pulsed laser light output from the output coupling mirror 30. The spectrum detector 40 detects the wavelength λ of the pulsed laser light for each pulse. The laser control processor 12 calculates the wavelength λ based on the wavelength detection results received from the spectrum detector 40. Then, the laser control processor 12 calculates the wavelength λ based on the wavelength detection results received from the spectrum detector 40. The laser control processor 12 then calculates the wavelength λ of the pulsed laser light output from the laser device 10. S t or target long wavelength λ L The rotation stage 26 of the prism 24 is controlled so that the rotation angle t becomes equal to t.

[0044] 3. Issues In the laser device 10 according to the comparative example, the speed of wavelength change during dual wavelength exposure depends on the rotation speed of the rotary stage 26. Also, the time required for wavelength change is the reciprocal of the oscillation frequency. In the configuration of the laser device 10, for example, the wavelength can be changed within a time of 250 μs (equivalent to 4 kHz), but the wavelength change is not possible in 167 μs (equivalent to 6 kHz). For this reason, it is necessary to change the wavelength of the pulsed laser light output from the laser device 10 to the target dual wavelength (λ S t, λ L Even at repetition rates of 4 kHz or higher, it is desirable to stabilize the wavelength of the output pulsed laser light at each of the two target wavelengths.

[0045] 4. Embodiment 1 4.1 Laser Apparatus 4.1.1 Configuration Fig. 5 is a diagram schematically illustrating the configuration of a laser apparatus 100 according to embodiment 1. The laser apparatus 100 includes a solid-state seeder 102 serving as a master oscillator (MO), an excimer amplifier 112 serving as a power amplifier (PA), a beam characteristic measuring instrument 34A, and a laser control processor 12A.

[0046] The solid-state seeder 102 includes a first semiconductor laser 103, a second semiconductor laser 104, an optical switch 105, a solid-state amplifier 106, and a wavelength conversion system 108.

[0047] The first semiconductor laser 103 and the second semiconductor laser 104 are each a semiconductor laser that continuously oscillates in a single longitudinal mode around a wavelength of 773.6 nm, with the two lasers having slightly different wavelengths. The first semiconductor laser 103 and the second semiconductor laser 104 may each be a continuous wave distributed feedback semiconductor laser. The wavelengths of the first semiconductor laser 103 and the second semiconductor laser 104 may be in the range of 700 nm to 800 nm, with the wavelength difference between the two lasers being in the range of 1 pm to 110 pm.

[0048] The optical switch 105 selects one of the laser beams output from the first semiconductor laser 103 and the second semiconductor laser 104 and transmits it to a subsequent stage. The laser beam transmitted to the subsequent stage can be switched at a cycle of, for example, 10 kHz.

[0049] The optical switch 105 selects a laser beam in response to a first seed trigger signal Tr1 or a second seed trigger signal Tr2 received from the laser control processor 12A and transmits the selected laser beam to a subsequent stage. The optical switch 105 may be a mechanical optical path switch, an electro-optic effect switch, a thermo-optic optical switch, a semiconductor waveguide optical switch, or the like. The mechanical optical path switch may include a MEMS (Micro Electro Mechanical Systems).

[0050] The solid-state amplifier 106 pulses the laser light selected by the optical switch 105 and amplifies the energy of the laser light. The solid-state amplifier 106 includes a titanium sapphire crystal and a pump pulse laser. The solid-state amplifier 106 is an example of a "first solid-state amplifier" in this disclosure.

[0051] The wavelength conversion system 108 includes a nonlinear crystal that converts the first pulsed laser light of a near-infrared wavelength output from the solid-state amplifier 106 into a second pulsed laser light of an ultraviolet wavelength. The nonlinear crystal may be a combination of an LBO crystal and a KBBF crystal. "LBO" is represented by the chemical formula LiBO. "KBBF" is represented by the chemical formula KBeBOF.

[0052] The laser light may be transmitted from the first semiconductor laser 103 or the second semiconductor laser 104 to the optical switch 105 and from the optical switch 105 to the solid-state amplifier 106 using optical fibers.

[0053] The excimer amplifier 112 includes a chamber 114, a PPM 117, a charger 119, a convex mirror 120, and a concave mirror 122. The chamber 114 includes windows 116a and 116b, a pair of electrodes 118a and 118b, and an electrical insulating member 123. The chamber 114 is filled with ArF laser gas.

[0054] The PPM 117 includes a switch 118 and a charging capacitor (not shown). The PPM 117 is connected to the electrode 118b via a feedthrough in an electrical insulating member 123.

[0055] The charger 119 is connected to a charging capacitor (not shown), and the electrode 118a is connected to a ground potential.

[0056] The convex mirror 120 and the concave mirror 122 are arranged so that the second pulsed laser light output from the wavelength conversion system 108 passes through the discharge space between the electrodes 118a and 118b three times to expand the beam.

[0057] The beam characteristic measuring instrument 34A may have a configuration similar to that of the beam characteristic measuring instrument 34 described in Fig. 4. The first beam splitter 36, the second beam splitter 38, and the energy detector 42 are arranged so that a portion of the third pulsed laser beam PL3 output from the excimer amplifier 112 is reflected by the first beam splitter 36, and then passes through the second beam splitter 38 to enter the energy detector 42. In addition, the spectrum detector 40 is arranged so that the third pulsed laser beam PL3 reflected by the second beam splitter 38 enters the spectrum detector 40.

[0058] 4.1.2 Operation The first semiconductor laser 103 continuously oscillates the first seed laser light of the first wavelength.

[0059] The second semiconductor laser 104 constantly oscillates a second seed laser beam having a second wavelength in a continuous wave manner.

[0060] The laser control processor 12A determines, for each pulse, the seed laser light to be transmitted to the subsequent stage by the optical switch 105. Then, in accordance with this determination, the laser control processor 12A transmits a first seed trigger signal Tr1 or a second seed trigger signal Tr2 to the optical switch 105. For example, when the first seed trigger signal Tr1 is ON, the first seed laser light output from the first semiconductor laser 103 is transmitted to the subsequent stage of the optical switch 105. Also, when the second seed trigger signal Tr2 is ON, the second seed laser light output from the second semiconductor laser 104 is transmitted to the subsequent stage of the optical switch 105. The selected seed laser light selected by the optical switch 105 is incident on the solid-state amplifier 106.

[0061] The solid-state amplifier 106 pulses and amplifies the selected seed laser light selected by the optical switch 105 and outputs a first pulsed laser light. When the solid-state amplifier 106 receives an MO trigger signal Tr3 from the laser control processor 12A, it outputs a pulsed laser light from the pump pulsed laser. While the pulsed laser light from the pump pulsed laser is incident on the titanium sapphire crystal, the selected seed laser light incident on the titanium sapphire crystal is amplified. The pulse width of the pulsed laser light output from the pump pulsed laser is, for example, 10 to 40 ns.

[0062] The first pulsed laser light pulsed and amplified by the solid-state amplifier 106 is converted to a desired ultraviolet wavelength by the wavelength conversion system 108. For example, the first seed laser light having a first wavelength of 773.600 nm output from the first semiconductor laser 103 is used to generate a fourth harmonic in the wavelength conversion system 108, which converts the first seed laser light into a second pulsed laser light having a wavelength of 193.400 nm.

[0063] Also, a wavelength conversion system 108 generates a fourth harmonic using a second seed laser beam having a second wavelength of 773.604 nm output from a second semiconductor laser 104 and converts the fourth harmonic into a second pulsed laser beam having a wavelength of 193.401 nm.

[0064] This allows the wavelength of the first pulsed laser beam around 193 nm output from the wavelength conversion system 108 to be changed by a wavelength difference of 1 pm. The first wavelength and the second wavelength output from the first semiconductor laser 103 are preferably selected so that the wavelength difference of the pulsed laser beam output from the wavelength conversion system 108 is within 1 pm.

[0065] The laser control processor 12A sends a PA trigger signal Tr4 to the switch 118 of the PPM 117 so that a discharge occurs between the electrodes in synchronization with the second pulsed laser light output from the solid seeder 102 entering the discharge space between the electrodes 118a and 118b in the chamber 114 of the excimer amplifier 112.

[0066] As a result, the second pulsed laser light output from the solid-state seeder 102 is amplified three times by the excimer amplifier 112 .

[0067] The laser control processor 12A can change the wavelength of the third pulsed laser beam PL3 output from the excimer amplifier 112 by switching the laser beam transmitted to the subsequent stage using the optical switch 105.

[0068] The energy detector 42 detects the pulse energy of the third pulsed laser light PL 3 output from the excimer amplifier 112 .

[0069] The laser control processor 12A calculates the pulse energy E based on the detection result received from the energy detector 42. Then, the laser control processor 12A controls the voltage of the high voltage pulse applied between the electrode 118a and the electrode 118b so that the pulse energy E of the third pulsed laser light PL3 ​​output from the laser device 100 becomes the target pulse energy Et.

[0070] The spectral detector 40 detects the spectral linewidth and wavelength of the third pulsed laser light PL 3 output from the excimer amplifier 112 .

[0071] The laser control processor 12A calculates the wavelength λ based on the wavelength detection result received from the spectrum detector 40. Then, the laser control processor 12A controls at least one of the current value of the current flowing through the semiconductor of the distributed feedback semiconductor laser and the temperature of the semiconductor so that the wavelength λ of the third pulsed laser light PL3 ​​output from the laser device 100 becomes the target wavelength. The laser control processor 12A is an example of a "processor" in the present disclosure.

[0072] 6 is an explanatory diagram showing an example of changing the wavelength per pulse by the optical switch 105. As shown in FIG. 6, the wavelength change using the optical switch 105 changes the wavelength per pulse to the target short wavelength λ S t and target long wavelength λ L 6 shows the wavelength distribution accumulated in one slit when step-and-scan exposure is performed by alternately switching between two wavelengths for each pulse.

[0073] The wavelength change is not limited to that for each pulse as shown in FIG. 6, but for example, as shown in FIG. 7, the target short wavelength λ is changed every few pulses.S t and target long wavelength λ L 7, the target short wavelength λ t may be switched every four pulses. S t and target long wavelength λ L An example of switching between t is shown.

[0074] Furthermore, the present invention is not limited to the examples shown in FIGS. 6 and 7, and may be applied to, for example, the target wavelength λ S t and λ L By changing the ratio of the number of pulses oscillated between t and t, the target short wavelength λ S t and target long wavelength λ L A difference may be made between the integrated energies of t and t.

[0075] 4.1.2.1 Example 1 of Wavelength Control Method Fig. 8 is a flowchart showing Example 1 of the processing procedure of the laser control processor 12A in embodiment 1. Fig. 8 shows an example of changing the wavelength for each pulse as shown in Fig. 6 .

[0076] In step S11, the laser control processor 12A reads the target two-wavelength control parameter data from the exposure control processor 310. The target two-wavelength control parameter data includes the target short wavelength λ S t and target long wavelength λ L Includes data on t. Target short wavelength λ S t and target long wavelength λ L t is an example of the "first target wavelength" and the "second target wavelength" in this disclosure.

[0077] In step S12, the laser control processor 12A determines whether the wavelength of the first semiconductor laser 103 is λ S The laser control processor 12A sets the current value I1 so that the wavelength of the second semiconductor laser 104 is λ L The current value I2 is set so that the current value becomes ta.

[0078] The wavelength λ of the first semiconductor laser 103 S ta is a wavelength that becomes the target short wavelength λst after wavelength conversion by the wavelength conversion system 108, and corresponds to the target wavelength of the first semiconductor laser 103 that corresponds to the target short wavelength λst after wavelength conversion. Similarly, the wavelength λ of the second semiconductor laser 104 Lta is the target long wavelength λ after wavelength conversion by the wavelength conversion system 108 L t, and the target long wavelength λ after wavelength conversion. L This corresponds to the target wavelength of the second semiconductor laser 104 corresponding to t.

[0079] In step S13, the laser control processor 12A sets the state of the optical switch 105 to a state in which the first semiconductor laser 103 outputs the first seed laser light.

[0080] In step S14, the laser control processor 12A determines whether or not the third pulsed laser beam PL3 has been detected by the spectrum detector 40. If the third pulsed laser beam PL3 has not been detected (step S14: No), the laser control processor 12A waits until the third pulsed laser beam PL3 is detected. If the third pulsed laser beam PL3 has been detected (step S14: Yes), the laser control processor 12A proceeds to step S15.

[0081] In step S15, the laser control processor 12A determines the wavelength λ of the third pulsed laser beam PL3 on the short wavelength side. S The wavelength λ measured using the spectrum detector 40 S is an example of a "measured value" in this disclosure.

[0082] In step S16, the laser control processor 12A calculates the wavelength λ measured in step S15. S and the target short wavelength λ S Difference Δλ S That is, the laser control processor 12A calculates Δλ S = λ S -λ S Calculate t.

[0083] In step S17, the laser control processor 12A calculates the Δλ calculated in step S16. S The current value I1 of the first semiconductor laser 103 is set so that the current I2 becomes zero.

[0084] Steps S13 to S17 are steps for performing wavelength measurement and control at short wavelengths.

[0085] Next, in step S19, the laser control processor 12A sets the state of the optical switch 105 to a state in which the second semiconductor laser 104 outputs the second seed laser light.

[0086] In step S20, the laser control processor 12A determines whether or not the third pulsed laser beam PL3 has been detected by the spectrum detector 40. If the third pulsed laser beam PL3 has not been detected (step S20: No), the laser control processor 12A waits until the third pulsed laser beam PL3 is detected. If the third pulsed laser beam PL3 has been detected (step S20: Yes), the laser control processor 12A proceeds to step S21.

[0087] In step S21, the laser control processor 12A determines the wavelength λ of the third pulsed laser beam PL3 on the long wavelength side. L The wavelength λ measured using the spectrum detector 40 L is an example of a "measured value" in this disclosure.

[0088] In step S22, the laser control processor 12A calculates the wavelength λ measured in step S21. L and the target long wavelength λ L Difference Δλ L That is, the laser control processor 12A calculates ΔλL=λ L -λ L Calculate t.

[0089] In step S23, the laser control processor 12A calculates the Δλ calculated in step S22. L The current value I2 of the second semiconductor laser 104 is set so that the current I2 becomes zero.

[0090] Steps S19 to S23 are steps for performing wavelength measurement and control at long wavelengths.

[0091] Next, in step S25, the laser control processor 12A determines whether or not to continue the two-wavelength control. If the two-wavelength control is to be continued (step S25: Yes), the laser control processor 12A proceeds to step S24. If the two-wavelength control is not to be continued (step S25: No), the laser control processor 12A ends the processing of the flowchart shown in FIG. 8.

[0092] In step S26, the laser control processor 12A determines whether or not to update the dual-wavelength control parameter. If the dual-wavelength control parameter is not to be updated (step S26: No), the laser control processor 12A returns the process to step S13. If the dual-wavelength control parameter is to be updated (step S26: Yes), the laser control processor 12A returns the process to step S11.

[0093] 4.1.2.2 Example 2 of Wavelength Control Method Fig. 9 is a flowchart showing Example 2 of the processing procedure of the laser control processor 12A in embodiment 1. The flowchart shown in Fig. 9 shows the wavelength λ for every N pulses, as described in Fig. 7. S and λ L 9. N is an integer equal to or greater than 2. The flowchart shown in FIG. 9 will be described below in terms of differences from FIG.

[0094] In the flowchart shown in Fig. 9, in step S11, the laser control processor 12A reads the data for N in addition to the two-wavelength parameter data. Also, in the flowchart shown in Fig. 9, step S18 is added between step S17 and step S19, and step S24 is added between step S23 and step S25. The other steps may be the same as those in Fig. 8.

[0095] In step S18, the laser control processor 12A determines whether or not N pulses have been detected. If N pulses have not been detected (step S18: No), the laser control processor 12A returns to step S14. If N pulses have been detected (step S18: Yes), the laser control processor 12A proceeds to step S19. Steps S13 to S18 are processing steps for measuring and controlling the wavelength at short wavelengths.

[0096] Furthermore, in step S24, the laser control processor 12A determines whether or not N pulses have been detected. If N pulses have not been detected (step S24: No), the laser control processor 12A returns to step S20. If N pulses have been detected (step S24: Yes), the laser control processor 12A proceeds to step S25. Steps S19 to S24 are processing steps for measuring and controlling wavelengths at long wavelengths.

[0097] 10 is a diagram schematically illustrating the configuration of the semiconductor laser 130. The semiconductor laser 130 is a single-longitudinal-mode distributed feedback semiconductor laser, and can be applied to each of the first semiconductor laser 103 and the second semiconductor laser 104 in the first embodiment.

[0098] The semiconductor laser 130 includes a semiconductor laser element 138, a Peltier element 148, a temperature sensor 150, a current controller 152, and a temperature controller 154. The semiconductor laser element 138 includes a first cladding layer 140, an active layer 142, and a second cladding layer 144, and includes a grating 146 at the boundary between the active layer 142 and the second cladding layer 144.

[0099] 4.2.2 Operation The central oscillation wavelength of the semiconductor laser 130 can be changed by changing the set temperature Ts of the semiconductor laser element 138 and / or the value of current I flowing through the semiconductor laser element 138. The laser control processor 12A sets the set temperature Ts and the value of current I, and controls the temperature controller 154 and the current controller 152, respectively, in accordance with the set temperature Ts and the value of current I.

[0100] When the oscillation wavelength of the semiconductor laser 130 is to be changed at high speed, the value of the current I flowing through the semiconductor laser 130 is changed at high speed. This makes it possible to change the wavelength of the continuous wave laser light at high speed.

[0101] 4.2.3 Others Each of the first semiconductor laser 103 and the second semiconductor laser 104 is not limited to a distributed feedback semiconductor laser, and may be, for example, a distributed Bragg reflector (DBR) semiconductor laser or a sampled grating distributed Bragg reflector (SG-DBR) semiconductor laser.

[0102] 11 is a diagram schematically illustrating an example of the configuration of the wavelength conversion system 108. The wavelength conversion system 108 includes a KBBF crystal 162, an LBO crystal 164, a rotation stage 166, a rotation stage 168, and a rotation stage driver 170. Each of the KBBF crystal 162 and the LBO crystal 164 is an example of a "first nonlinear crystal" in this disclosure.

[0103] The KBBF crystal 162 is placed on a rotation stage 166. The LBO crystal 164 is placed on a rotation stage 168. In order to rotate the nonlinear crystals at high speed, each of the rotation stages 166 and 168 may be a rotation stage including a piezoelectric element. A rotation stage driver 170 controls the angles of the rotation stages 166 and 168.

[0104] 4.3.2 Operation The first pulsed laser beam PL1 input to the wavelength conversion system 108 is incident on the LBO crystal 164. The LBO crystal 164 converts the first pulsed laser beam PL1 having a wavelength of approximately 773.6 nm into pulsed laser beam having a wavelength of approximately 386.8 nm, which is second harmonic light.

[0105] The KBBF crystal 162 converts the pulsed laser light having a wavelength of approximately 386.8 nm output from the LBO crystal 164 into a second pulsed laser light PL2 having a wavelength of approximately 193.4 nm, which is second harmonic light.

[0106] The second pulsed laser light PL2 converted to a wavelength of approximately 193.4 nm is output from the wavelength conversion system 108.

[0107] In single-wavelength oscillation, the incident angle of each nonlinear crystal is controlled so that the wavelength conversion efficiency is maximized at the target wavelength λt (to achieve phase matching).

[0108] 12 is a graph showing the wavelength conversion efficiency curves of the KBBF crystal 162 and the LBO crystal 164. For example, as shown in FIG. 12, the incident angle of each nonlinear crystal is controlled so that the wavelength conversion efficiency is maximized at a wavelength of 193.4 nm.

[0109] 12, the wavelength conversion efficiency changes when the wavelength changes. t When θ is large, the wavelength conversion efficiency decreases and the pulse energy E decreases unless the angle of incidence of the nonlinear crystal is controlled so that the wavelength conversion efficiency is maximized for each pulse.

[0110] Furthermore, the change in wavelength conversion efficiency when the wavelength is changed is large for the KBBF crystal 162 shown downstream in FIG. 11, but is small for the LBO crystal 164. t Up to a certain value, the decrease in pulse energy E can be suppressed by controlling the incident angle of only the KBBF crystal 162.

[0111] 4.3.3 Method for Controlling the Incident Angle of Nonlinear Crystal 4.3.3.1 Example Flowchart FIG. 13 is a flowchart showing an example of the control of the incident angle of the nonlinear crystal executed by the laser control processor 12A.

[0112] In step S51, the laser control processor 12A reads the target center wavelength λct of the two-wavelength spectrum and the calculated value of the target wavelength difference Δλt from the two-wavelength control parameter data received from the exposure control processor 310. The target center wavelength λct is calculated based on the target short wavelength λ S t and target long wavelength λ L t, that is, λct = (λ S t+λ LThe target wavelength difference Δλt is the target long wavelength λ L t and target short wavelength λ S t, that is, Δλt=λ L t-λ S It is t.

[0113] In step S52, the laser control processor 12A determines whether the target wavelength difference Δλt between the two wavelength spectra is within the allowable range Δλtr for the decrease in wavelength conversion efficiency. That is, the laser control processor 12A determines whether Δλt≦Δλtr is satisfied. The allowable range Δλtr may be, for example, in the range of 1 pm to 2 pm. If Δλt≦Δλtr is satisfied (step S52: Yes), the laser control processor 12A proceeds to step S53. If Δλt≦Δλtr is not satisfied (step S52: No), the laser control processor 12A proceeds to step S57.

[0114] In step S53, the laser control processor 12A controls the angle of incidence of the nonlinear crystal so that the wavelength at which the wavelength conversion efficiency is maximized becomes the target central wavelength λct.

[0115] In step S54, the laser control processor 12A determines whether or not the third pulsed laser beam PL3 has been detected by the spectrum detector 40. If the third pulsed laser beam PL3 has not been detected (step S54: No), the laser control processor 12A waits until the third pulsed laser beam PL3 is detected. If the third pulsed laser beam PL3 has been detected (step S54: Yes), the laser control processor 12A proceeds to step S55.

[0116] In step S55, the laser control processor 12A determines whether or not to continue the two-wavelength control. If the two-wavelength control is to be continued (step S55: Yes), the laser control processor 12A proceeds to step S56. If the two-wavelength control is not to be continued (step S55: No), the laser control processor 12A ends the processing of the flowchart in FIG. 13.

[0117] In step S56, the laser control processor 12A determines whether to change the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum. If the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum is not to be changed (step S56: No), the laser control processor 12A returns the process to step S54. If the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum is to be changed (step S56: Yes), the laser control processor 12A returns the process to step S51.

[0118] In step S57, the laser control processor 12A determines whether the wavelength at which the wavelength conversion efficiency is maximized is the target short wavelength λ S The incident angle of the nonlinear crystal is controlled so that t is obtained.

[0119] In step S58, the laser control processor 12A determines whether or not the third pulsed laser beam PL3 has been detected by the spectrum detector 40. If the third pulsed laser beam PL3 has not been detected (step S58: No), the laser control processor 12A waits until the third pulsed laser beam PL3 is detected. If the third pulsed laser beam PL3 has been detected (step S58: Yes), the laser control processor 12A proceeds to step S59.

[0120] In step S59, the laser control processor 12A determines that the wavelength at which the wavelength conversion efficiency is maximized is the target long wavelength λ L The incident angle of the nonlinear crystal is controlled so that t is obtained.

[0121] In step S60, the laser control processor 12A determines whether or not the third pulsed laser beam PL3 has been detected. If the third pulsed laser beam PL3 has not been detected (step S60: No), the laser control processor 12A waits until the third pulsed laser beam PL3 is detected. If the third pulsed laser beam PL3 has been detected (step S60: Yes), the laser control processor 12A proceeds to step S61.

[0122] In step S61, the laser control processor 12A determines whether or not to continue the two-wavelength control. If the two-wavelength control is not to be continued (step S61: No), the laser control processor 12A ends the processing of the flowchart shown in Fig. 13. If the two-wavelength control is to be continued (step S61: Yes), the laser control processor 12A proceeds to step S62.

[0123] In step S62, the laser control processor 12A determines whether to change the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum. If the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum is to be changed (step S62: Yes), the laser control processor 12A returns the process to step S51. If the target center wavelength λct or the target wavelength difference Δλt of the two-wavelength spectrum is not to be changed (step S62: No), the laser control processor 12A returns the process to step S57.

[0124] Although Fig. 13 shows the control in the case of changing the wavelength for each pulse as described in Fig. 6, the control of the angle of incidence in the case of changing the wavelength for every N pulses as described in Fig. 7 is basically the same as the flowchart shown in Fig. 13. In the case of changing the wavelength for every N pulses, it is determined in each of steps S58 and S60 whether or not N pulses have been detected.

[0125] 13, the laser control processor 12A determines whether the target wavelength difference Δλt between the two wavelength spectra is within the allowable range Δλtr for the decrease in wavelength conversion efficiency (step S52). Depending on the result of this determination, the laser control processor 12A switches the control of the incident angle of the nonlinear crystal.

[0126] 14 and 15 are graphs showing the relationship between wavelength λ after excimer amplification and wavelength conversion efficiency, in which the horizontal axis represents wavelength λ after excimer amplification and the vertical axis represents wavelength conversion efficiency.

[0127] If the target wavelength difference Δλt of the two-wavelength spectrum is within the allowable range δλtr of the decrease in wavelength conversion efficiency, as shown in Figure 14, the laser control processor 12A controls the incident angle of the nonlinear crystal so as to achieve the maximum wavelength conversion efficiency at the target center wavelength λct of the two-wavelength spectrum (step S53).

[0128] For example, if the wavelength λ after wavelength conversion of the KBBF crystal 162 and the incident angle at which the wavelength conversion efficiency is maximized have the relationship shown in FIG. 16 , and the target center wavelength after wavelength conversion is λKct, the laser control processor 12A controls the incident angle of the KBBF crystal 162 to θKct. The relationship shown in FIG. 16 may be calculated as an approximate curve and stored in the memory unit of the laser control processor 12A, or may be stored as table data in the memory unit of the laser control processor 12A. The memory unit may be a combination of a memory as a main storage device and a storage unit as an auxiliary storage device. The laser control processor 12A obtains information regarding the incident angle θKct at which the wavelength conversion efficiency is maximized according to the target center wavelength λKct from the approximate curve or table data stored in the memory unit. Furthermore, in addition to controlling the incident angle of the KBBF crystal 162, the laser control processor 12A may also control the incident angle so as to maximize the wavelength conversion efficiency of the LBO crystal 164.

[0129] On the other hand, if the target wavelength difference Δλt of the two-wavelength spectrum is not within the allowable range Δλtr of the decrease in wavelength conversion efficiency, as shown in FIG. 15, the laser control processor 12A adjusts the target short wavelength λ S t and target long wavelength λ L The angle of incidence of the nonlinear crystal is changed for each pulse so as to maximize the wavelength conversion efficiency for each of t (steps S57 and S59).

[0130] Target short wavelength λ SFor example, when t, the laser control processor 12A controls the incident angle of the KBBF crystal 162 to θKSt when the target short wavelength after wavelength conversion is λKSt, based on the relationship between the wavelength λ after wavelength conversion of the KBBF crystal 162 and the incident angle at which the wavelength conversion efficiency is maximized, as shown in Figure 17. The relationship shown in Figure 17 is the same as the relationship shown in Figure 16, and information stored in the memory unit of the laser control processor 12A as an approximate curve or table data is applied. The same applies to the relationship shown in Figure 18, which will be described later. In addition to controlling the incident angle of the KBBF crystal 162, the laser control processor 12A may also control the incident angle so that the wavelength conversion efficiency of the LBO crystal 164 is maximized.

[0131] Similarly, the target long wavelength λ L At time t, for example, based on the relationship between the wavelength λ after wavelength conversion of the KBBF crystal 162 and the angle of incidence at which the wavelength conversion efficiency is maximized, the laser control processor 12A controls the angle of incidence of the KBBF crystal 162 to θKLt when the target long wavelength after wavelength conversion is λKLt, as shown in Fig. 18. In addition to controlling the angle of incidence of the KBBF crystal 162, the laser control processor 12A may also control the angle of incidence so that the wavelength conversion efficiency of the LBO crystal 164 is maximized.

[0132] 4.4 Actions and Effects According to the laser device 100 according to the first embodiment, even at a repetition rate of 4 kHz or more, the wavelength of the output third pulsed laser beam PL3 can be adjusted to the target wavelength (λ S t and λ L t) respectively.

[0133] Furthermore, even when the two-wavelength control parameter is changed, the wavelength of the output third pulsed laser beam PL3 can be adjusted to the target two-wavelength (λ S t and λ L t) respectively.

[0134] Furthermore, according to the laser device 100, the change in wavelength conversion efficiency in the wavelength conversion system 108 due to the two-wavelength control is suppressed, so that the pulse energy E of the output third pulse laser light PL3 ​​can be stabilized at the target pulse energy Et.

[0135] 5. Embodiment 2 5.1 Configuration Fig. 19 is a diagram schematically showing the configuration of a solid seeder 102B applied to the laser apparatus 100 according to embodiment 2. The solid seeder 102B shown in Fig. 19 may be adopted instead of the solid seeder 102 in the laser apparatus 100 shown in Fig. 5.

[0136] The solid-state seeder 102B includes a first solid-state laser device 202, a second solid-state laser device 208, a dichroic mirror 220, and a wavelength conversion system 108B.

[0137] The first solid-state laser device 202 includes a first semiconductor laser 103B, a second semiconductor laser 104B, an optical switch 105, and a first solid-state amplifier 106B.

[0138] The first semiconductor laser 103B and the second semiconductor laser 104B are each a semiconductor laser that continuously oscillates in a single longitudinal mode around a wavelength of 1554 nm, with the two lasers having slightly different wavelengths. The first semiconductor laser 103B and the second semiconductor laser 104B may each be a continuous wave distributed feedback semiconductor laser. The wavelengths of the first semiconductor laser 103B and the second semiconductor laser 104B may be in the range of 1480 nm to 1580 nm, with the wavelength difference between the two lasers being in the range of 1 pm to 110 pm.

[0139] The first solid-state amplifier 106B pulses the laser light selected by the optical switch 105 and amplifies the energy of the laser light.

[0140] The first solid-state amplifier 106B is an optical parametric amplifier (OPA), which may be, for example, a periodically poled lithium niobate (PPLN) or a periodically poled potassium titanyl phosphate (PPKTP).

[0141] The OPA uses pulsed laser light with a wavelength of 1030 nm, which will be described later, as pump light and pulse-amplifies the selected seed laser light output from the optical switch 105 .

[0142] The second solid-state laser device 208 includes a third semiconductor laser 210, a second solid-state amplifier 212, a plurality of nonlinear crystals (an LBO crystal 214 and a first CLBO crystal 216) that convert the wavelength of the fourth harmonic light, and a dichroic mirror 218. The LBO crystal 214 and the first CLBO crystal 216 are examples of the "second nonlinear crystal" in this disclosure. "CLBO" is a compound having the chemical formula CsLiBO. 10 It is expressed as:

[0143] The third semiconductor laser 210 oscillates continuously in a single longitudinal mode at around 1030 nm, and may be a continuous wave distributed feedback semiconductor laser.

[0144] The second solid-state amplifier 212 pulses the laser light output from the third semiconductor laser 210 and amplifies the energy of the laser light.

[0145] The LBO crystal 214 converts the fifth pulsed laser beam PL5 having a wavelength of 1030 nm output from the second solid-state amplifier 212 into second harmonic light having a wavelength of 515 nm.

[0146] The dichroic mirror 218 is disposed on the optical path between the LBO crystal 214 and the first CLBO crystal 216, and has high transmittance for the pulsed laser beam with a wavelength of 515 nm and high reflectance for the pulsed laser beam with a wavelength of 1030 nm. The dichroic mirror 218 is disposed so that the highly reflected pulsed laser beam with a wavelength of 1030 nm is incident on the first solid-state amplifier 106B as pump light.

[0147] The wavelength conversion system 108B includes a second CLBO crystal 224, a third CLBO crystal 226, a rotation stage 168 for changing the incident angle, and the rotation stage 166. In Fig. 19, the first CLBO crystal 216, the second CLBO crystal 224, and the third CLBO crystal 226 are denoted as "CLBO1," "CLBO2," and "CLBO3," respectively. The second CLBO crystal 224 is disposed on the rotation stage 168, and the third CLBO crystal 226 is disposed on the rotation stage 166.

[0148] The dichroic mirror 220 is arranged so as to highly reflect the first pulsed laser light PL1 having a wavelength of approximately 1554 nm output from the first solid-state laser device 202 and highly transmit the fourth pulsed laser light PL4 having a wavelength of 257.6 nm output from the second solid-state laser device 208, and so that both pulsed laser lights are incident coaxially on the wavelength conversion system 108B.

[0149] The other configurations may be similar to those of the laser device 100 according to the first embodiment.

[0150] 5.2 Operation In the solid-state seeder 102B, the wavelength of the fourth pulsed laser light PL4 output from the second solid-state laser device 208 is fixed, and the wavelength of the first pulsed laser light PL1 output from the first solid-state laser device 202 is changed every pulse or every N pulses, thereby changing the wavelength of the second pulsed laser light PL2 output from the wavelength conversion system 108B.

[0151] The laser control processor 12A in the second embodiment constantly causes the first semiconductor laser 103B and the second semiconductor laser 104B to continuously oscillate. The laser control processor 12A also keeps the current value I3 of the third semiconductor laser 210 constant, causes the third semiconductor laser 210 to continuously oscillate, and causes the third semiconductor laser 210 to output third seed laser light, which is a CW laser light with a wavelength of 1030 nm. The wavelength of 1030 nm is an example of the "third wavelength" in the present disclosure.

[0152] The second solid-state amplifier 212 pulses and amplifies the third seed laser beam output from the third semiconductor laser 210, and outputs a fifth pulsed laser beam PL5.

[0153] As described above, the LBO crystal 214 converts the fifth pulsed laser light PL5 having a wavelength of 1030 nm output from the second solid-state amplifier 212 into second harmonic light having a wavelength of 515 nm.

[0154] The dichroic mirror 218 has high transmittance for the pulsed laser beam with a wavelength of 515 nm. The first CLBO crystal 216 converts the pulsed laser beam with a wavelength of 515 nm into second-harmonic light with a wavelength of 257.6 nm. The dichroic mirror 218 also highly reflects the fifth pulsed laser beam PL5 with a wavelength of 1030 nm that could not be wavelength-converted by the LBO crystal 214, and makes it incident as pump light for the first solid-state amplifier 106B of the first solid-state laser device 202.

[0155] The first pulsed laser beam PL1 having a wavelength of approximately 1554 nm output from the first solid-state laser device 202 and the fourth pulsed laser beam PL4 having a wavelength of 257.6 nm output from the first CLBO crystal 216 are frequency-added and wavelength-converted to a wavelength of approximately 220.9 nm by the second CLBO crystal 224. Furthermore, the pulsed laser beam having a wavelength of approximately 220.9 nm and the first pulsed laser beam PL1 having a wavelength of approximately 1554 nm are frequency-added and wavelength-converted to a wavelength of approximately 193.4 nm by the third CLBO crystal 226.

[0156] The laser control processor 12A can alternately change the wavelength of the second pulsed laser beam PL2 by alternately switching the laser beam transmitted to the subsequent stage using the optical switch 105.

[0157] For example, by setting the wavelength of the laser light output from the first semiconductor laser 103B to 1552.800 nm and the wavelength of the laser light output from the second semiconductor laser 104B to 1552.840 nm, the wavelength of the second pulsed laser light PL2 output from the solid seeder 102B can be set to two wavelengths, 193.400 nm and 193.401 nm.

[0158] The control flow of wavelength change executed by the laser control processor 12A in the second embodiment may be similar to that shown in FIG. 8 or FIG.

[0159] The control flow of the incident angle of the nonlinear crystal in the wavelength conversion system 108 in embodiment 2 may also be similar to that shown in FIG. 13 . In step S53 of FIG. 13 , for example, when the target center wavelength after wavelength conversion is λC2ct and the wavelength λ after wavelength conversion of the second CLBO crystal 224 and the incident angle at which the wavelength conversion efficiency of the nonlinear crystal is maximized satisfy the relationship shown in FIG. 20 , the laser control processor 12A controls the incident angle of the second CLBO crystal 224 to θC2ct. The relationship shown in FIG. 20 may be calculated as an approximation curve and stored in the memory of the laser control processor 12A, or may be stored as table data in the memory of the laser control processor 12A. In addition to controlling the incident angle of the second CLBO crystal 224, the laser control processor 12A may also control the incident angle so that the wavelength conversion efficiency of the third CLBO crystal 226 is maximized.

[0160] In step S57, the laser control processor 12A controls the incident angle of the second CLBO crystal 224 to θC2St when the target short wavelength after wavelength conversion is λC2St, as shown in FIG. 21 , based on the relationship between the wavelength λ after wavelength conversion of the second CLBO crystal 224 and the incident angle at which the wavelength conversion efficiency of the nonlinear crystal is maximized. The relationship shown in FIG. 21 is the same as the relationship shown in FIG. 20 , and information stored in the memory unit of the laser control processor 12A as an approximate curve or table data is applied. The same applies to the relationship shown in FIG. 22 (described later). In addition to controlling the incident angle of the second CLBO crystal 224, the laser control processor 12A may also control the incident angle so as to maximize the wavelength conversion efficiency of the third CLBO crystal 226.

[0161] In step S59, the laser control processor 12A controls the incident angle of the second CLBO crystal 224 to θC2Lt when the target long wavelength after wavelength conversion is λC2Lt, based on the relationship between the wavelength λ after wavelength conversion of the second CLBO crystal 224 and the incident angle at which the wavelength conversion efficiency of the nonlinear crystal is maximized, as shown in Fig. 22. In addition to controlling the incident angle of the second CLBO crystal 224, the laser control processor 12A may also control the incident angle so that the wavelength conversion efficiency of the third CLBO crystal 226 is maximized.

[0162] 5.3 Actions and Effects According to the second embodiment, the same actions and effects as those of the first embodiment can be obtained.

[0163] 6. Electronic Device Manufacturing Method Figure 23 is a diagram showing a schematic configuration of an exposure apparatus 300. In Figure 23, the exposure apparatus 300 includes an illumination optical system 306 and a projection optical system 308. Laser light generated by the laser apparatus 100 is incident on the exposure apparatus 300. The illumination optical system 306 illuminates a reticle pattern on the reticle stage RT with the laser light incident from the laser apparatus 100. The projection optical system 308 reduces and projects the 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 photoresist.

[0164] The exposure apparatus 300 exposes the workpiece with laser light reflecting the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel in opposite directions. After the device pattern is transferred to the semiconductor wafer through the exposure process described above, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in this disclosure.

[0165] 7. Other The above description is intended to be illustrative and not restrictive. Therefore, it will be apparent to those skilled in the art that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. It will also be apparent to those skilled in the art that the embodiments of the present disclosure can be used in combination.

[0166] Terms used throughout this specification and claims should be construed as "open ended" terms unless expressly stated otherwise. For example, terms such as "comprise," "have," "include," and "comprise" should be construed as meaning "without excluding the presence of elements other than those listed." Furthermore, the modifier "a" should be construed as meaning "at least one" or "one or more." Furthermore, 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, combinations of these with elements other than "A," "B," and "C" should also be construed as including those elements.

Claims

1. A first semiconductor laser that outputs a first seed laser light of continuous oscillation having a first wavelength; a second semiconductor laser that outputs a second seed laser light of continuous oscillation having a second wavelength different from the first wavelength; an optical switch that outputs one of the first seed laser light and the second seed laser light as a selected seed laser light; a first solid-state amplifier that pulses and amplifies the selected seed laser light to output a first pulsed laser light; a wavelength conversion system that outputs a second pulsed laser light by wavelength conversion using the first pulsed laser light; an excimer amplifier that amplifies the second pulsed laser light and outputs a third pulsed laser light; and a beam characteristics measuring instrument that measures the wavelength of the third pulsed laser light. a processor that selects one of the first seed laser beam and the second seed laser beam as the selected seed laser beam based on a target wavelength, and controls the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser beam based on a wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser beam becomes the target wavelength.

2. A laser device as described in claim 1, wherein the processor controls the wavelengths of the first semiconductor laser and the second semiconductor laser by controlling at least one of the current value of the current flowing through each semiconductor of the first semiconductor laser and the second semiconductor laser and the temperature of the semiconductor.

3. A laser device according to claim 1, wherein a first target wavelength and a second target wavelength are set as the target wavelength.

4. A laser device as described in claim 3, wherein the processor controls the wavelength of the first semiconductor laser based on a measurement value of the wavelength of the third pulsed laser light obtained when the first seed laser light is selected as the selected seed laser light, so that the wavelength of the third pulsed laser light becomes the first target wavelength, and controls the wavelength of the second semiconductor laser based on a measurement value of the wavelength of the third pulsed laser light obtained when the second seed laser light is selected as the selected seed laser light, so that the wavelength of the third pulsed laser light becomes the second target wavelength.

5. A laser device according to claim 3, wherein the wavelength conversion system includes: a first nonlinear crystal; and a rotation stage that rotates the first nonlinear crystal; and the processor calculates a target central wavelength that is the average value of the first target wavelength and the second target wavelength, and controls the rotation stage so that the wavelength at which wavelength conversion efficiency is maximized becomes the target central wavelength.

6. A laser device as described in claim 5, wherein the processor includes a memory unit that stores the relationship between the target central wavelength and the incident angle at which the wavelength conversion efficiency is maximized, and obtains information regarding the incident angle at which the wavelength conversion efficiency is maximized according to the target central wavelength from the relationship stored in the memory unit.

7. A laser device as described in claim 1, wherein the wavelength conversion system includes: a first nonlinear crystal; and a rotation stage that rotates the first nonlinear crystal; and the processor controls the rotation stage so that the wavelength at which the wavelength conversion efficiency is maximized becomes the target wavelength.

8. A laser device as described in claim 1, wherein the processor includes a memory unit that stores the relationship between the target wavelength and the incident angle at which the wavelength conversion efficiency is maximized, and obtains information regarding the incident angle at which the wavelength conversion efficiency is maximized according to the target wavelength from the memory unit.

9. A laser device according to claim 1, wherein each of the first wavelength and the second wavelength is within a range of 700 nm to 800 nm, and a difference between the first wavelength and the second wavelength is within a range of 1 pm to 110 pm.

10. A laser device as described in claim 1, comprising a solid-state laser device that outputs a fourth pulsed laser beam, and the wavelength conversion system outputs the second pulsed laser beam by wavelength conversion using a sum frequency of the first pulsed laser beam and the fourth pulsed laser beam.

11. A laser device as described in claim 10, comprising: a third semiconductor laser that outputs a continuous oscillation third seed laser light having a third wavelength different from each of the first wavelength and the second wavelength; a second solid-state amplifier that pulses and amplifies the third seed laser light to output a fifth pulsed laser light; and a second nonlinear crystal that wavelength converts the fifth pulsed laser light to output fourth harmonic light, which is the fourth pulsed laser light.

12. A laser device according to claim 10, wherein each of the first wavelength and the second wavelength is within a range of 1480 nm to 1580 nm, and a difference between the first wavelength and the second wavelength is within a range of 1 pm to 110 pm.

13. A laser device as described in claim 1, wherein the processor controls the wavelength of the first semiconductor laser or the second semiconductor laser so that a wavelength difference between the wavelength of the third pulsed laser light obtained when the first seed laser light is selected as the selected seed laser light and the wavelength of the third pulsed laser light obtained when the second seed laser light is selected as the selected seed laser light is within 1 pm.

14. A laser device according to claim 1, wherein the processor outputs the second pulsed laser light at a repetition rate of 4 kHz or more.

15. A wavelength control method for a laser device, comprising: outputting a first seed laser light of continuous oscillation having a first wavelength from a first semiconductor laser; outputting a second seed laser light of continuous oscillation having a second wavelength different from the first wavelength from a second semiconductor laser; outputting one of the first seed laser light and the second seed laser light as a selected seed laser light from an optical switch; pulsing and amplifying the selected seed laser light by a first solid-state amplifier to output a first pulsed laser light; outputting a second pulsed laser light by wavelength conversion using the first pulsed laser light by a wavelength conversion system; amplifying the second pulsed laser light by an excimer amplifier to output a third pulsed laser light; measuring the wavelength of the third pulsed laser light by a beam characteristic measuring instrument; selecting one of the first seed laser light and the second seed laser light as the selected seed laser light based on a target wavelength, and controlling the wavelength of the first semiconductor laser or the second semiconductor laser outputting the selected seed laser light based on a wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser light becomes the target wavelength.

16. A method for manufacturing an electronic device, comprising: a first semiconductor laser that outputs a first seed laser light of continuous oscillation having a first wavelength; a second semiconductor laser that outputs a second seed laser light of continuous oscillation having a second wavelength different from the first wavelength; an optical switch that outputs one of the first seed laser light and the second seed laser light as a selected seed laser light; a first solid-state amplifier that pulses and amplifies the selected seed laser light to output a first pulsed laser light; a wavelength conversion system that outputs a second pulsed laser light by wavelength conversion using the first pulsed laser light; an excimer amplifier that amplifies the second pulsed laser light and outputs a third pulsed laser light; and a beam characteristics measuring instrument that measures the wavelength of the third pulsed laser light. a processor that selects one of the first seed laser beam and the second seed laser beam as the selected seed laser beam based on a target wavelength, and controls the wavelength of the first semiconductor laser or the second semiconductor laser that outputs the selected seed laser beam based on a wavelength measured by the beam characteristic measuring instrument so that the wavelength of the third pulsed laser beam becomes the target wavelength; generating laser light by a laser apparatus comprising: a processor that selects one of the first seed laser beam and the second seed laser beam as the selected seed laser beam based on a target wavelength,

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