Method for manufacturing optical module, method for manufacturing gas laser apparatus, and manufacturing jig for optical module

Abstract

To provide a method for manufacturing an optical module that narrows the spectral linewidth of laser light.SOLUTION: A method for manufacturing an optical module including an output coupling mirror that transmits a portion of laser light and reflects another portion of the laser light, and a planar mirror having a reflective surface being a plane perpendicular to a surface on the incidence side of the laser light on the output coupling mirror, includes the steps of: arranging a first autocollimator so that emitted light is incident perpendicularly on the surface on the incidence side; arranging, between the surface on the incidence side and the first autocollimator, an optical element having a first reflective surface and a second reflective surface facing the surface on the incidence surface side at an angle of 45° to the first reflective surface, so that the light emitted from the first autocollimator is incident perpendicularly on the first reflective surface; arranging a second autocollimator so that the emitted light is reflected by the second reflective surface and incident perpendicularly on the surface on the incidence side; and removing the optical element and arranging the planar mirror so that the light emitted from the second autocollimator is incident perpendicularly on the reflective surface of the planar mirror.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing an optical module, a method for manufacturing a gas laser device, and a manufacturing jig for an optical module.

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, as semiconductor integrated circuits have been miniaturized and highly integrated, an improvement in resolution has been demanded. For this reason, the wavelength of light emitted from an exposure light source has been shortened. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs laser light with a wavelength of about 248.0 nm and an ArF excimer laser device that outputs laser light with a wavelength of about 193.4 nm are used.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0005] A method for manufacturing an optical module according to an aspect of the present disclosure includes an output coupling mirror that transmits a part of laser light and reflects the other part of the laser light, and a plane mirror including a reflecting surface in a plane perpendicular to the surface of the output coupling mirror on the incident side of the laser light. A method for manufacturing an optical module, comprising: a first autocollimator arrangement step of arranging a first autocollimator so as to receive light reflected by the incident side surface among the light emitted by the first autocollimator and make the light incident perpendicularly to the incident side surface; an optical element including a first reflecting surface facing the first autocollimator and a second reflecting surface facing the incident side surface at an angle of 45° with respect to the first reflecting surface, and arranging the optical element between the incident side surface and the first autocollimator so as to receive light reflected by the first reflecting surface among the light emitted by the first autocollimator and make the light incident perpendicularly to the first reflecting surface; a second autocollimator arrangement step of arranging a second autocollimator so as to receive light reflected in the order of the second reflecting surface, the incident side surface, and the second reflecting surface among the emitted light and make the light incident perpendicularly to the incident side surface; removing the optical element, and a first mirror arrangement step of arranging a plane mirror so as to receive light reflected by the reflecting surface of the plane mirror among the light emitted by the second autocollimator and make the light incident perpendicularly to the reflecting surface.

[0006] A method for manufacturing a gas laser device according to an aspect of the present disclosure includes a chamber device that amplifies laser light output from a laser oscillator, an output coupling mirror that transmits a part of the laser light emitted from the chamber device and reflects the other part of the laser light emitted from the chamber device back to the chamber device, and an optical module including a plane mirror including a reflecting surface in a plane perpendicular to the surface on the incident side of the laser light of the output coupling mirror. A method for manufacturing a gas laser device, comprising: a first autocollimator arranging step of arranging a first autocollimator so as to receive light reflected by the incident side surface among the light emitted from the first autocollimator and make the light incident perpendicularly to the incident side surface; an optical element arranging step of arranging an optical element including a first reflecting surface facing the first autocollimator and a second reflecting surface facing the incident side surface at an angle of 45° with respect to the first reflecting surface between the incident side surface and the first autocollimator so as to receive light reflected by the first reflecting surface among the light emitted from the first autocollimator and make the light incident perpendicularly to the first reflecting surface; a second autocollimator arranging step of arranging a second autocollimator so as to receive light reflected in the order of the second reflecting surface, the incident side surface, and the second reflecting surface among the emitted light and make the light incident perpendicularly to the incident side surface; a first mirror arranging step of removing the optical element and arranging a plane mirror so as to receive light reflected by the reflecting surface of the plane mirror among the light emitted from the second autocollimator and make the light incident perpendicularly to the reflecting surface. The optical module manufactured by the method for manufacturing an optical module may be arranged such that the laser light emitted from the chamber device is incident perpendicularly on the incident side surface of the output coupling mirror.

[0007] A manufacturing jig for an optical module according to an aspect of the present disclosure includes an output coupling mirror that transmits a part of a laser beam and reflects the other part of the laser beam, and a plane mirror including a reflecting surface in a plane perpendicular to the surface of the output coupling mirror on the incident side of the laser beam, and is a manufacturing jig for an optical module, and includes a first autocollimator arranged such that the emitted light is incident perpendicularly to the surface of the output coupling mirror on the incident side, a first reflecting surface facing the first autocollimator, and a second reflecting surface facing the surface on the incident side at an angle of 45° with respect to the first reflecting surface, and an optical element arranged between the surface on the incident side and the first autocollimator such that the light emitted from the first autocollimator is incident perpendicularly on the first reflecting surface, and a second autocollimator arranged such that the emitted light is reflected by the second reflecting surface and is incident perpendicularly on the surface on the incident side.

Brief Description of Drawings

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

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[0009] 1. Description of a manufacturing apparatus for an electronic device used in an exposure process of an electronic device 2. Description of a gas laser device of a comparative example 2.1 Configuration 2.2 Operation 2.3 Manufacturing method of a beam expander 2.4 Problems 3. Description of the beam expander and the manufacturing method of the beam expander according to Embodiment 1 3.1 Configuration 3.2 Manufacturing method of a beam expander 3.3 Function and effect

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0011] 1. Description of a manufacturing apparatus for an electronic device used in an exposure process of an electronic device FIG. 1 is a schematic diagram showing an overall schematic configuration example of a manufacturing apparatus for an electronic device used in an exposure process of an electronic device. As shown in FIG. 1, the manufacturing apparatus used in the exposure process includes a gas laser device 100 and an exposure device 200. The exposure device 200 includes an illumination optical system 210 including a plurality of mirrors 211, 212, 213, and a projection optical system 220. The illumination optical system 210 illuminates the reticle pattern on the reticle stage RT with the laser light incident from the gas laser device 100. The projection optical system 220 reduces and projects the laser light transmitted through the reticle and forms an image on a workpiece (not shown) disposed on the workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer on which a photoresist is applied. The exposure device 200 exposes the workpiece with the laser light reflecting the reticle pattern by synchronously translating the reticle stage RT and the workpiece table WT in parallel. By transferring the device pattern to the semiconductor wafer through the above exposure process, a semiconductor device, which is an electronic device, can be manufactured.

[0012] 2. Description of a gas laser device of a comparative example 2.1 Configuration The gas laser device of the comparative example will be described. Note that the comparative example of the present disclosure is a form recognized by the applicant as being known only to the applicant and is not a known example recognized by the applicant.

[0013] FIG. 2 is a schematic diagram showing an overall schematic configuration example of the gas laser device 100 of this example. The gas laser device 100 is, for example, an ArF excimer laser device that uses a mixed gas containing argon (Ar), fluorine (F2), and neon (Ne). This gas laser device 100 outputs laser light having a central wavelength of about 193.4 nm. Note that the gas laser device 100 may be a gas laser device other than an ArF excimer laser device, for example, a KrF excimer laser device that uses a mixed gas containing krypton (Kr), F2, and Ne. In this case, the gas laser device 100 emits laser light having a central wavelength of about 248.0 nm. A mixed gas containing Ar, F2, and Ne as a laser medium or a mixed gas containing Kr, F2, and Ne as a laser medium may be called a laser gas. Note that in the mixed gas used in each of the ArF excimer laser device and the KrF excimer laser device, helium (He) may be used instead of Ne.

[0014] The gas laser device 100 of this example mainly includes a housing 110, a laser oscillator 130 that is a master oscillator disposed in the internal space of the housing 110, an optical transmission unit 141, an amplifier 160 that is a power oscillator, a detection unit 153, a display unit 180, a processor 190, a laser gas exhaust device 701, and a laser gas supply device 703.

[0015] The laser oscillator 130 mainly includes a chamber device CH1, a charger 41, a pulse power module 43, a narrowbanding module 60, and an output coupling mirror 70.

[0016] In FIG. 2, the internal configuration of the chamber device CH1 is shown as viewed from a direction substantially perpendicular to the traveling direction of the laser light. The chamber device CH1 mainly includes a housing 30, a pair of windows 31a and 31b, a pair of electrodes 32a and 32b, an insulating portion 33, a feedthrough 34, and an electrode holder portion 36.

[0017] The housing 30 is supplied with the above laser gas from the laser gas supply device 703 through a pipe into the internal space of the housing 30, and the laser gas is enclosed in the internal space. The internal space is a space where light is generated by the excitation of the laser medium in the laser gas. This light travels toward the windows 31a and 31b.

[0018] The window 31a is disposed on the front wall surface of the housing 30 in the traveling direction of the laser light from the gas laser device 100 to the exposure device 200, and the window 31b is disposed on the rear wall surface of the housing 30 in the traveling direction. The windows 31a and 31b are calcium fluoride substrates, and the surfaces of the windows 31a and 31b on the inner side and the outer side of the housing 30 are flat. Note that the windows 31a and 31b only need to be able to transmit laser light and are not limited to calcium fluoride substrates.

[0019] The electrodes 32a and 32b are disposed to face each other in the internal space of the housing 30, and the longitudinal direction of the electrodes 32a and 32b is along the traveling direction of the light generated by the high voltage applied between the electrode 32a and the electrode 32b. The space between the electrode 32a and the electrode 32b in the housing 30 is sandwiched by the window 31a and the window 31b. The electrodes 32a and 32b are discharge electrodes for exciting the laser medium by glow discharge. In this example, the electrode 32a is a cathode and the electrode 32b is an anode.

[0020] The electrode 32a is supported by an insulating portion 33. The insulating portion 33 closes an opening formed in the housing 30. The insulating portion 33 includes an insulator. Further, a feedthrough 34 made of a conductive member is disposed in the insulating portion 33. The feedthrough 34 applies the voltage supplied from the pulse power module 43 to the electrode 32a. The electrode 32b is supported by an electrode holder portion 36 and is electrically connected to the electrode holder portion 36.

[0021] The charger 41 is a DC power supply device that charges a capacitor (not shown) provided inside the pulse power module 43 to a predetermined voltage. The charger 41 is disposed outside the housing 30 and is connected to the pulse power module 43. The pulse power module 43 includes a switch (not shown) controlled by the processor 190. When the switch changes from OFF to ON by the control, the pulse power module 43 boosts the voltage applied from the charger 41 to generate a pulsed high voltage, and is a voltage application circuit that applies this high voltage to the electrodes 32a and 32b. When the high voltage is applied, a discharge occurs between the electrode 32a and the electrode 32b. Due to the energy of this discharge, the laser medium inside the housing 30 is excited. When the excited laser gas transitions to the ground state, light is emitted, and the emitted light passes through the windows 31a and 31b and exits the housing 30. The windows 31a and 31b are tilted at the Brewster angle with respect to the traveling direction of the laser light so that the reflection of the P-polarized light of the laser light is suppressed. In this example, they are tilted with respect to the direction perpendicular to the traveling direction of the laser light and the direction in which the electrodes 32a and 32b face each other. For this reason, the laser light emitted from the chamber device CH1 includes the first linearly polarized light whose polarization direction is perpendicular to the direction in which the electrodes 32a and 32b face each other, and the linearly polarized light whose polarization direction is different from the polarization direction of the first linearly polarized light is reduced from the laser light. That is, the windows 31a and 31b also serve as polarizers that are tilted with respect to the polarization direction of the first linearly polarized light and reduce the linearly polarized light having a polarization direction different from the polarization direction of the first linearly polarized light from the laser light.

[0022] The narrowbanding module 60 includes a housing 65, a prism 61, a grating 63, and a rotating stage (not shown) disposed in the internal space of the housing 65. An opening is formed in the housing 65, and the housing 65 is connected to the rear side of the housing 30 through the opening.

[0023] The prism 61 expands the beam width of the light emitted from the window 31b and makes the light incident on the grating 63. Further, the prism 61 reduces the beam width of the reflected light from the grating 63 and returns the light to the internal space of the housing 30 through the window 31b. The prism 61 is supported by a rotating stage and rotates by the rotating stage. By rotating the prism 61, the incident angle of the light with respect to the grating 63 is changed. Therefore, by rotating the prism 61, the wavelength of the light returning from the grating 63 to the housing 30 through the prism 61 can be selected. In FIG. 2, an example in which one prism 61 is arranged is shown, but two or more prisms may be arranged.

[0024] The surface of the grating 63 is made of a material with a high reflectivity, and a large number of grooves are provided on the surface at a predetermined interval. The grating 63 is a dispersive optical element. The cross-sectional shape of each groove is, for example, a right triangle. The light incident on the grating 63 from the prism 61 is reflected by these grooves and diffracted in a direction corresponding to the wavelength of the light. The grating 63 is retrofitted so that the incident angle of the light incident on the grating 63 from the prism 61 coincides with the diffraction angle of the diffracted light of the desired wavelength. Thereby, the light of the desired wavelength is returned to the housing 30 through the prism 61.

[0025] The output coupling mirror 70 faces the window 31a, transmits a part of the laser light emitted from the window 31a, reflects the other part, and returns it to the internal space of the housing 30 through the window 31a. The output coupling mirror 70 is fixed to a holder (not shown) and is arranged in the internal space of the housing 110.

[0026] The grating 63 and the output coupling mirror 70 provided with the housing 30 interposed therebetween form a Fabry - Perot type resonator, and the housing 30 is arranged on the optical path of the resonator. For this reason, the resonator resonates light between both sides sandwiching the chamber device CH1.

[0027] The optical transmission unit 141 includes high reflection mirrors 141b and 141c as main components. The high reflection mirrors 141b and 141c are fixed to holders (not shown) respectively with their respective tilt angles adjusted, and are arranged in the internal space of the housing 110. The high reflection mirrors 141b and 141c highly reflect laser light. The high reflection mirrors 141b and 141c are arranged on the optical path of the laser light from the output coupling mirror 70. The laser light is reflected by the high reflection mirrors 141b and 141c and travels to the rear mirror 371 of the amplifier 160. At least a part of this laser light passes through the rear mirror 371.

[0028] The amplifier 160 amplifies the energy of the laser light output from the laser oscillator 130. The basic configuration of the amplifier 160 is generally the same as that of the laser oscillator 130. To distinguish the components of the amplifier 160 from those of the laser oscillator 130, the chamber device, housing, pair of windows, pair of electrodes, insulating part, feedthrough, electrode holder part, charger, pulse power module, and output coupling mirror of the amplifier 160 are described as the chamber device CH3, housing 330, pair of windows 331a, 331b, pair of electrodes 332a, 332b, insulating part 333, feedthrough 334, electrode holder part 336, charger 341, pulse power module 343, and output coupling mirror 370. The electrodes 332a, 332b generate a discharge for amplifying the laser light from the laser oscillator 130. The direction in which the electrodes 332a, 332b face each other is perpendicular to the direction of change of the first linearly polarized light in the laser light from the laser oscillator 130. The windows 331a, 331b are tilted with respect to the polarization direction of the first linearly polarized light such that the first linearly polarized light in the laser light is incident as P-polarized light and the incident angle θ of the laser light becomes the Brewster angle. For this reason, the laser light emitted from the chamber device CH3 includes the first linearly polarized light, and the linearly polarized light in a polarization direction different from the polarization direction of the first linearly polarized light is reduced from the laser light. That is, the windows 331a, 331b, like the windows 31a, 31b, are tilted with respect to the polarization direction of the first linearly polarized light and also serve as a polarizer that reduces the linearly polarized light in a polarization direction different from the polarization direction of the first linearly polarized light from the laser light. The pulse power module 343 is a voltage application circuit similar to the pulse power module 43.

[0029] Further, the amplifier 160 mainly differs from the laser oscillator 130 in that it does not include the narrowbanding module 60 and includes a rear mirror 371 and a beam expander 400 as an optical module.

[0030] FIG. 3 is a schematic diagram of the amplifier 160 of this example as viewed from the direction in which the pair of electrodes 332a, 332b face each other. In FIG. 3, the internal configuration of the chamber device CH3 is shown, and the polarization direction of the first linearly polarized light is indicated by a solid arrow.

[0031] The rear mirror 371 is provided between the highly reflective mirror 141c and the window 331b and faces each other. The rear mirror 371 transmits part of the laser light from the laser oscillator 130 toward the space between the electrodes 332a and 332b, and reflects part of the laser light amplified by the electrodes 332a and 332b toward the space between the electrodes 332a and 332b. The rear mirror 371 is attached to the cavity plate 511 located on the window 331b side among the pair of cavity plates 511 and 512 arranged so as to sandwich the chamber device CH3 in the longitudinal direction of the electrodes 332a and 332b. The cavity plate 511 is provided with a through hole through which the laser light from the laser oscillator 130 passes. The pair of cavity plates 511 and 512 are connected to a cavity frame 513 extending along a direction parallel to the longitudinal direction of the electrodes 332a and 332b around the chamber device CH3. In addition, in FIG. 2, the description of the cavity plates 511 and 512 and the cavity frame 513 is omitted.

[0032] The output coupling mirror 370 is arranged on the side opposite to the rear mirror 371 side from the chamber device CH3, and the beam expander 400 is arranged between the chamber device CH3 and the output coupling mirror 370.

[0033] FIG. 4 is a schematic diagram showing a schematic configuration example of the beam expander 400 of this example, and is a schematic diagram of the beam expander 400 viewed along the polarization direction of the first linearly polarized light. Therefore, in FIG. 4, the direction perpendicular to the paper surface is the polarization direction of the first linearly polarized light.

[0034] As shown in FIGS. 3 and 4, the beam expander 400 of this example includes a convex mirror 410, a concave mirror 420, a flat mirror 430, and a holding portion 470.

[0035] FIG. 5 is a perspective view showing the convex mirror 410, concave mirror 420, and flat mirror 430 of this example. In FIG. 5, the polarization direction of the first linearly polarized light is indicated by the solid arrow. The convex mirror 410 is a plate-shaped member having a reflecting surface 411 on one main surface that reflects light. The concave mirror 420 is a plate-shaped member having a reflecting surface 421 on one main surface that reflects light. The flat mirror 430 is a plate-shaped member having a reflecting surface 431 on one main surface that reflects light, and the reflecting surface 431 is flat. The convex mirror 410 reflects the laser light from the chamber device CH3 toward the flat mirror 430 so that the beam width of the laser light expands. The flat mirror 430 reflects the laser light reflected by the convex mirror 410 toward the concave mirror 420. The concave mirror 420 reflects the laser light toward the output coupling mirror 370 so as to collimate the expanded beam width of the laser light reflected by the flat mirror 430 to be constant. Further, the concave mirror 420 reflects the laser light from the output coupling mirror 370 toward the flat mirror 430 so that the beam width of the laser light shrinks. The flat mirror 430 reflects the laser light reflected by the concave mirror 420 toward the convex mirror 410. The convex mirror 410 reflects the laser light toward the chamber device CH3 so as to collimate the reduced beam width of the laser light reflected by the flat mirror 430 to be constant, and the laser light returns to the internal space of the housing 330 through the window 331a.

[0036] In this example, the convex mirror 410 is a convex cylindrical mirror, and the shape of the convex mirror 410 when the reflecting surface 411 is viewed from the front is a rectangle elongated in a direction parallel to the focal line 412 of the convex mirror 410. The shape of the reflecting surface 411 in a cross section perpendicular to the focal line 412 is an arc, but the shape is not limited and may be, for example, a parabola. Further, the concave mirror 420 is a concave cylindrical mirror, and the shape of the concave mirror 420 when the reflecting surface 421 is viewed from the front is a rectangle elongated in a direction parallel to the focal line 422 of the concave mirror 420. The shape of the reflecting surface 421 in a cross section perpendicular to the focal line 422 is an arc, but the shape is not limited and may be, for example, a parabola. Note that the focal line 412 is a line connecting the foci of the convex mirror 410, and the focal line 422 is a line connecting the foci of the concave mirror 420. Further, the shapes of the convex mirror 410 and the concave mirror 420 are not limited. For example, the shape of the convex mirror 410 may be a rectangle elongated in a direction perpendicular to the focal line 412, and the shape of the concave mirror 420 may be a rectangle elongated in a direction perpendicular to the focal line 422.

[0037] As shown in FIG. 4, the focal line 412 is included in a plane that includes the optical axis LA1 of the laser light and extends in a direction in which the electrodes 332a and 332b face each other, and inclines so as to approach the electrode 332a side as it moves away from the chamber device CH3. Further, the focal line 422 is included in a plane that includes the optical axis LA1 of the laser light and the focal line 412, and inclines so as to approach the electrode 332b side as it moves away from the chamber device CH3. Further, the reflecting surface 431 of the plane mirror 430 is parallel to the optical axis LA1 of the laser light and perpendicular to the surface on the beam expander 400 side of the output coupling mirror 370. The surface is the incident side surface 370s on which the laser light from the chamber device CH3 is incident. And the focal line 412v in the virtual image 410v of the convex mirror 410 formed by the reflecting surface 431 and the focal line 422 of the concave mirror 420 are located on the same straight line. That is, the positions of the convex mirror 410, the concave mirror 420, and the plane mirror 430 are adjusted so as to be like this. Note that the focal line 412v and the focal line 422 do not have to be located on the same straight line. In FIG. 4, the virtual image 410v and the focal line 412v in the virtual image 410v are shown by broken lines.

[0038] The holding part 470 includes a first holding part 471 and a second holding part 472. The first holding part 471 is a member that holds the convex mirror 410, the concave mirror 420, and the plane mirror 430. The first holding part 471 includes a planar placement surface 473, and the convex mirror 410, the concave mirror 420, and the plane mirror 430 are arranged on the placement surface 473. The placement surface 473 is parallel to the optical axis LA1 of the laser beam and perpendicular to the direction in which the electrodes 332a and 332b face each other. In this example, the convex mirror 410 is arranged on the placement surface 473 in a state where one of the two side surfaces extending along the longitudinal direction of the convex mirror 410 faces the placement surface 473. The concave mirror 420 is arranged on the placement surface 473 in a state where one of the two side surfaces extending along the longitudinal direction of the concave mirror 420 faces the placement surface 473. The plane mirror 430 is arranged on the placement surface 473 in a state where one of the two side surfaces extending along the longitudinal direction of the plane mirror 430 faces the placement surface 473. The convex mirror 410, the concave mirror 420, and the plane mirror 430 are fixed to the placement surface 473 with, for example, an adhesive (not shown) and held by the first holding part 471. Examples of the adhesive include ultraviolet curable resin.

[0039] The second holding part 472 is a member that holds the output coupling mirror 370. In this example, it is a plate-like member extending in a direction substantially perpendicular to the optical axis LA1 of the laser beam. An output coupling mirror holder 375 for holding the output coupling mirror 370 is fixed to the second holding part 472, and the output coupling mirror 370 is held by the second holding part 472. A through hole through which the laser beam passing through the output coupling mirror 370 passes is provided in the second holding part 472. Also, the first holding part 471 is fixed to the second holding part 472. The second holding part 472 is attached to the cavity plate 512 located on the window 331a side.

[0040] On the incident side surface 370s of the output coupling mirror 370, a partial reflection film having a predetermined reflectivity is coated. The output coupling mirror 370 reflects a part of the laser light from the chamber device CH3 whose beam width has been expanded by the beam expander 400 toward the beam expander 400, and transmits the other part of the laser light.

[0041] The output coupling mirror 370 may be circular. The incident side surface 370s and the surface opposite to the incident side surface 370s are flat. The rear mirror 371 has a configuration similar to that of the output coupling mirror 70.

[0042] The rear mirror 371 and the output coupling mirror 370 provided with the housing 330 interposed therebetween constitute a resonator that resonates the laser light amplified by the electrodes 332a and 332b. The housing 330 and the beam expander 400 are arranged on the optical path of the resonator. The laser light emitted from the window 331a of the housing 330 enters the output coupling mirror 370 via the beam expander 400, and a part of it is reflected by the output coupling mirror 370. The laser light reflected by the output coupling mirror 370 returns to the internal space of the housing 330 via the beam expander 400 and the window 331a, and is emitted from the window 331b. The laser light emitted from this window 331b is reflected by the rear mirror 371 and returns to the internal space of the housing 330 via the window 331b. In this way, the laser light emitted from the housing 330 reciprocates between the rear mirror 371 and the output coupling mirror 370. The reciprocating laser light is amplified each time it passes through the laser gain space between the electrode 332a and the electrode 332b. That is, the resonator resonates light between both sides sandwiching the chamber device CH3, and the output coupling mirror 370 is arranged on one side sandwiching the chamber device CH3. A part of the amplified laser light passes through the output coupling mirror 370. The laser light passing through the output coupling mirror 370 travels toward the detection unit 153.

[0043] The detection unit 153 mainly includes a beam splitter 153b and an optical sensor 153c.

[0044] The beam splitter 153b is disposed on the optical path of the laser light that passes through the output coupling mirror 370. The beam splitter 153b transmits the laser light that passes through the output coupling mirror 370 toward the output window 173 with a high transmittance, and reflects a part of the laser light toward the light receiving surface of the optical sensor 153c.

[0045] The optical sensor 153c measures the pulse energy of the laser light incident on the light receiving surface of the optical sensor 153c. The optical sensor 153c is electrically connected to the processor 190, and outputs a signal indicating the measured pulse energy to the processor 190. The processor 190 controls the voltage applied to the electrodes 32a, 32b of the amplifier 160 based on the signal.

[0046] On the side opposite to the output coupling mirror 370 with respect to the beam splitter 153b of the detection unit 153, an output window 173 is provided. The output window 173 is provided on the wall of the housing 110. The light transmitted through the beam splitter 153b is emitted from the output window 173 to the exposure apparatus 200 outside the housing 110. This laser light is, for example, pulsed laser light having a central wavelength of 193.4 nm.

[0047] The display unit 180 is a monitor that displays the state of control by the processor 190 based on a signal from the processor 190. The display unit 180 may be disposed outside the housing 110.

[0048] The processor 190 of the present disclosure is a processing device including a storage device in which a control program is stored and a CPU (Central Processing Unit) that executes the control program. The processor 190 is specially configured or programmed to execute various processes included in the present disclosure. Further, the processor 190 controls the entire gas laser device 100. Further, the processor 190 is electrically connected to an exposure processor (not shown) of the exposure apparatus 200, and transmits and receives various signals to and from the exposure processor.

[0049] The laser gas exhaust device 701 and the laser gas supply device 703 are electrically connected to the processor 190 by signal lines (not shown). The laser gas exhaust device 701 includes an exhaust pump (not shown), and exhausts laser gas from the internal space of the housings 30, 330 through a pipe by suction of the exhaust pump according to a control signal from the processor 190. The laser gas supply device 703 supplies laser gas from a laser gas supply source (not shown) disposed outside the housing 110 to the internal space of the housings 30, 330 through a pipe according to a control signal from the processor 190.

[0050] 2.2 Operation Next, the operation of the gas laser device 100 of the comparative example will be described.

[0051] Before the gas laser device 100 emits laser light, laser gas is supplied from the laser gas supply device 703 to the internal space of the housings 30, 330.

[0052] When the gas laser device 100 emits laser light, the processor 190 receives a signal indicating the target energy Et from the exposure processor and a light emission trigger signal. The target energy Et is the target value of the energy of the laser light used in the exposure process. The processor 190 sets a predetermined charging voltage to the charger 41 so that the energy E becomes the target energy Et, and turns on the switch of the pulse power module 43 in synchronization with the light emission trigger signal. As a result, the pulse power module 43 generates a pulsed high voltage from the electrical energy held in the charger 41, and a high voltage is applied between the electrode 32a and the electrode 32b. When the high voltage is applied, a discharge occurs between the electrode 32a and the electrode 32b, and the laser medium contained in the laser gas between the electrode 32a and the electrode 32b is excited, and light is emitted when the laser medium returns to the ground state. The emitted light resonates between the grating 63 and the output coupling mirror 70, and is amplified each time it passes through the discharge space in the internal space of the housing 30, and laser oscillation occurs. The laser light includes first linearly polarized light, and when passing through the windows 31a and 31b, linearly polarized light having a polarization direction different from the polarization direction of the first linearly polarized light is reduced from the laser light. A part of the laser light passes through the output coupling mirror 70, is reflected by the high reflection mirrors 141b and 141c, passes through the rear mirror 371 and the window 331b, and travels into the housing 330.

[0053] The processor 190 turns on the switch of the pulse power module 343 so that a discharge occurs when the laser light from the laser oscillator 130 travels into the discharge space in the housing 330. That is, the processor 190 controls the pulse power module 343 so that a high voltage is applied to the electrodes 332a and 332b after a predetermined delay time has elapsed with respect to the timing when the switch of the pulse power module 43 is turned on.

[0054] As a result, the laser light incident on the amplifier 160 is amplified by the amplifier 160. Further, the laser light that has traveled into the internal space of the housing 330 travels through the window 331a and the beam expander 400 as described above and proceeds to the output coupling mirror 370 and is reflected by the output coupling mirror 370. The laser light reflected by the output coupling mirror 370 travels through the beam expander 400 and the window 331a into the internal space of the housing 330 and exits through the window 331b. The light exiting through the window 331b is reflected by the rear mirror 371 and travels through the window 331b into the internal space of the housing 330. Thus, the laser light of a predetermined wavelength reciprocates between the rear mirror 371 and the output coupling mirror 370. The laser light includes first linearly polarized light, and when passing through the windows 331a and 331b, linearly polarized light having a polarization direction different from that of the first linearly polarized light is reduced from the laser light. Further, the laser light is amplified each time it passes through the discharge space inside the housing 330, and a part of the laser light becomes amplified laser light.

[0055] In the beam expander 400, the laser light emitted from the chamber device CH3 is incident on the reflecting surface 411 of the convex mirror 410 such that the first linear polarization in the laser light becomes S polarization. The reflecting surface 411 reflects the laser light so that the beam width of the laser light is expanded. The laser light reflected by the convex mirror 410 is incident on the reflecting surface 431 of the plane mirror 430 such that the first linear polarization in the laser light becomes S polarization, and the reflecting surface 431 reflects the laser light toward the concave mirror 420. The laser light reflected by the plane mirror 430 is incident on the reflecting surface 421 of the concave mirror 420 such that the first linear polarization in the laser light becomes S polarization. The reflecting surface 421 reflects the laser light toward the output coupling mirror 370 so as to collimate the expanded beam width of the laser light to be constant. Generally, an optical element that reflects light tends to be less likely to deteriorate over time compared to an optical element that transmits light. For this reason, the deterioration of the beam expander 400 over time is suppressed compared to the case where the beam expander 400 is composed of a prism that transmits light. Also, most of the deflection components included in the amplified laser light are the first linear polarization. Such laser light is incident on and reflected by the reflecting surface 411, the reflecting surface 421, and the reflecting surface 431 such that the first linear polarization in the laser light becomes S polarization. The reflectance of S polarization tends to be higher than the reflectance of P polarization. For this reason, a decrease in the amount of light is suppressed at the reflecting surface 411, the reflecting surface 421, and the reflecting surface 431.

[0056] Also, the amplified laser light from the amplifier 160 passes through the output coupling mirror 370 and travels toward the beam splitter 153b.

[0057] A part of the amplified laser light that has traveled to the beam splitter 153b passes through the beam splitter 153b and the output window 173 and travels to the exposure apparatus 200, and the other part is reflected by the beam splitter 153b and travels to the optical sensor 153c.

[0058] The optical sensor 153c measures the energy E of the received amplified laser beam. The optical sensor 153c outputs a signal indicating the measured energy E to the processor 190. The processor 190 performs feedback control on the charging voltage of the chargers 41, 341 so that the difference ΔE between the energy E and the target energy Et is within an allowable range.

[0059] 2.3 Manufacturing Method of Beam Expander Next, the manufacturing method of the beam expander 400 in the comparative example will be described.

[0060] In this example, first, a holding part 470 that holds the output coupling mirror 370, a convex mirror 410, a concave mirror 420, and a flat mirror 430 are prepared. Next, each of the convex mirror 410, the concave mirror 420, and the flat mirror 430 is arranged at the design position on the arrangement surface 473 of the first holding part 471 and fixed with an adhesive. Thus, the beam expander 400 is manufactured.

[0061] 2.4 Problems The dimensions of the convex mirror 410, the concave mirror 420, and the flat mirror 430 include manufacturing tolerances. Also, the dimensions of the design positions of these mirrors include tolerances. For this reason, even if these mirrors are arranged at the design positions, the performance of the laser beam may deviate from the design value, and it may be necessary to adjust the positions of these mirrors. In adjusting the arrangement of these mirrors, if the reflecting surface 431 of the flat mirror 430 is not perpendicular to the incident-side surface 370s of the output coupling mirror 370, the performance of the laser beam may deviate from the design value even if the positions of the convex mirror 410 and the concave mirror 420 are adjusted. For this reason, there is a demand to make the reflecting surface 431 perpendicular to the incident-side surface 370s and suppress the deviation of the performance of the laser beam from the design value.

[0062] Therefore, in the following embodiments, a manufacturing method of an optical module capable of suppressing the deviation of the performance of the laser beam from the design value is exemplified.

[0063] 3. Description of the Beam Expander and the Manufacturing Method of the Beam Expander According to Embodiment 1 Next, the beam expander 400 of Embodiment 1 and the method for manufacturing the beam expander 400 will be described. Regarding the configurations similar to those described above, the same reference numerals will be given, and redundant descriptions will be omitted unless otherwise specifically described. Also, in some of the drawings, for the sake of clarity, part of the members are omitted or simplified.

[0064] 3.1 Configuration FIG. 6 is a schematic diagram showing a schematic configuration example of the beam expander 400 of the present embodiment in the same manner as FIG. 4. As shown in FIG. 6, the beam expander 400 of the present embodiment mainly differs from the beam expander 400 of the comparative example in that it further includes a convex mirror holder 440, a concave mirror holder 450, a convex mirror base 480, and a flat mirror base 490.

[0065] The convex mirror holder 440 is a plate-like member extending along one of two side surfaces extending along the longitudinal direction of the convex mirror 410, and the side surface of the convex mirror 410 is fixed to the convex mirror holder 440 by, for example, an adhesive.

[0066] The concave mirror holder 450 is a plate-like member extending along one of two side surfaces extending along the longitudinal direction of the concave mirror 420, and the side surface of the concave mirror 420 is fixed to the concave mirror holder 450 by, for example, an adhesive. The concave mirror holder 450 is fixed to the arrangement surface 473 of the first holding portion 471 by, for example, bolts.

[0067] The convex mirror base 480 is a member to which the convex mirror holder 440 is fixed. The convex mirror base 480 of the present embodiment is a plate-like member. The convex mirror base 480 is attached to the arrangement surface 473 with three screws 481 in a state where one main surface of the convex mirror base 480 faces the arrangement surface 473 of the first holding portion 471. The convex mirror base 480 is separated from the arrangement surface 473, and the inclination with respect to the arrangement surface 473 can be changed by the three screws 481. In FIG. 6, only one screw 481 is labeled. The convex mirror holder 440 is fixed to the main surface 482 on the side opposite to the arrangement surface 473 side of the convex mirror base 480 with an adhesive 483. That is, the convex mirror 410 is fixed to the arrangement surface 473 via the convex mirror base 480 and the convex mirror holder 440. The adhesive 483 is separated into a plurality of adhesive portions, and the adhesive 483 is disposed between the convex mirror holder 440 and the main surface 482. For this reason, the convex mirror holder 440 and the main surface 482 are separated, and a space is formed in the region where the adhesive 483 is not disposed between the convex mirror holder 440 and the main surface 482. In FIG. 6, only one adhesive portion is labeled. Note that the adhesive 483 does not have to be separated into a plurality of adhesive portions. Further, the configuration of the convex mirror base 480 is not limited as long as it can change the inclination with respect to the arrangement surface 473.

[0068] The flat mirror base 490 is a member to which the flat mirror 430 is fixed. The flat mirror base 490 of the present embodiment has the same configuration as the convex mirror base 480, is attached to the arrangement surface 473, and can change the inclination with respect to the arrangement surface 473. The flat mirror 430 is fixed to the main surface 492 on the side opposite to the arrangement surface 473 side of the flat mirror base 490 with an adhesive (not shown). That is, the flat mirror 430 is fixed to the arrangement surface 473 via the flat mirror base 490. The adhesive for fixing the flat mirror 430 may be separated into a plurality of adhesive portions like the adhesive 483. Further, the configuration of the flat mirror base 490 is not limited as long as it can change the inclination with respect to the arrangement surface 473.

[0069] 3.2 Manufacturing Method of Beam Expander FIG. 7 is a diagram showing an example of a flowchart of a manufacturing method of the beam expander 400 according to the present embodiment. Hereinafter, the manufacturing method of the beam expander 400 may be simply referred to as the manufacturing method. As shown in FIG. 7, the manufacturing method according to the present embodiment includes a preparation step P1, an output coupling mirror arrangement step P2, a first autocollimator arrangement step P3, an optical element arrangement step P4, a second autocollimator arrangement step P5, a first mirror arrangement step P6, a wavefront sensor arrangement step P7, a pinhole plate arrangement step P8, a reference light source arrangement step P9, and a second mirror arrangement step P10.

[0070] (Preparation Step P1) This step is a step of preparing the components constituting the beam expander 400. In the present embodiment, an output coupling mirror 370 held by a holding portion 470, a convex mirror 410 fixed to a convex mirror holder 440, a concave mirror 420 fixed to a concave mirror holder 450, a flat mirror 430 fixed to a flat mirror base 490, and a convex mirror base 480 are prepared. The output coupling mirror 370 is adjusted in the direction with respect to the holding portion 470 such that the laser light from the chamber device CH3 is perpendicularly incident on the incident-side surface 370s when the second holding portion 472 of the holding portion 470 is attached to the cavity plate 512. Further, the arrangement surface 473 of the first holding portion 471 in the holding portion 470 and the incident-side surface 370s are adjusted to be perpendicular.

[0071] (Output Coupling Mirror Arrangement Step P2) This step involves placing the output coupling mirror 370 at a predetermined position in the manufacturing jig 600 for the beam expander 400. FIG. 8 shows the state of this step. As shown in FIG. 8, the manufacturing jig 600 of this embodiment includes a plate 610, a jig base 620, and a plurality of stages. In FIG. 8, only the first stage 630 is shown, and the description of the other stages is omitted. The plate 610 is a plate-like member with one main surface 610s being flat, and a plurality of stages can be arranged on the main surface 610s. Hereinafter, the direction perpendicular to the main surface 610s will be described as the Y direction, the direction orthogonal to the Y direction as the X direction, and the direction orthogonal to the Y direction and the X direction as the Z direction.

[0072] The configuration of the jig base 620 is the same as that of the cavity plate 512, and the holding portion 470 can be attached thereto. The jig base 620 is fixed to the main surface 610s. In this embodiment, by attaching the holding portion 470 to the jig base 620, the output coupling mirror 370 is arranged at a predetermined position.

[0073] The first stage 630 is disposed on the main surface 610s on the side opposite to the jig base 620 side from the holding part 470, and includes a mounting surface 630s on which members such as a collimator described later can be mounted. In the present embodiment, the first stage 630 includes a translation stage 631, a lifting stage 632, a rotation stage 633, and a gonio stage 634. The translation stage 631 is movable in the X direction and the Z direction. The lifting stage 632 is disposed on the mounting surface 631s of the translation stage 631, and the mounting surface 632s located on the side opposite to the mounting surface 631s side is movable in the Y direction. The rotation stage 633 is disposed on the mounting surface 632s of the lifting stage 632, and the mounting surface 633s located on the side opposite to the mounting surface 632s side is rotatable around an axis parallel to the Y direction. The gonio stage 634 is disposed on the mounting surface 633s of the rotation stage 633, and the mounting surface located on the side opposite to the mounting surface 633s side is the mounting surface 630s of the first stage 630. The gonio stage 634 can tilt the mounting surface 630s around an axis perpendicular to the Y direction. Therefore, the first stage 630 can move the mounting surface 630s in the X direction, Y direction, and Z direction, rotate the mounting surface 630s around an axis parallel to the Y direction, and tilt the mounting surface 630s around an axis perpendicular to the Y direction.

[0074] (First Auto-Collimator Arrangement Step P3) This step is to arrange the first autocollimator 710 such that the light emitted from the first autocollimator 710 is incident perpendicularly on the incident-side surface 370s of the output coupling mirror 370. FIG. 9 is a diagram showing the state of this step. In this embodiment, the first autocollimator 710 is arranged on the mounting surface 630s of the first stage 630 such that the light 711 from the first autocollimator 710 is incident on the incident-side surface 370s. Then, the light 711r reflected by the incident-side surface 370s is received by the first autocollimator 710, and the first autocollimator 710 measures the incident angle of the light 711 incident on the incident-side surface 370s. Based on this measurement result, the position of the first autocollimator 710, the inclination of the first autocollimator 710 with respect to the main surface 610s, and the orientation of the first autocollimator 710 in the direction parallel to the main surface 610s are adjusted by the first stage 630. Then, the light 711 emitted from the first autocollimator 710 is made to be incident perpendicularly on the incident-side surface 370s. In this embodiment, the first autocollimator 710 is arranged such that the incident angle of the light 711 on the incident-side surface 370s is 0.02 mrad or less.

[0075] (Optical element arrangement step P4) This step is to arrange the optical element 670. FIG. 10 is a diagram showing the state of this step. FIG. 11 is a diagram of the state shown in FIG. 10 as viewed from a direction perpendicular to the placement surface 473. As shown in FIGS. 10 and 11, the optical element 670 includes a first reflecting surface 671 and a second reflecting surface 672. The first reflecting surface 671 and the second reflecting surface 672 are planes that reflect light. The second reflecting surface 672 forms an angle of 45° with the first reflecting surface 671. The optical element 670 of this embodiment is a triangular prism, and the first reflecting surface 671 and the second reflecting surface 672 are part of the side surfaces of the prism. Both end faces in the extending direction of the optical element 670 are perpendicular to the first reflecting surface 671 and the second reflecting surface 672.

[0076] In this project, an optical element 670 is arranged between the incident-side surface 370s and the first autocollimator 710 so that the light 711 emitted from the first autocollimator 710 is perpendicularly incident on the first reflecting surface 671. At this time, the first reflecting surface 671 faces the first autocollimator 710, and the second reflecting surface 672 faces the incident-side surface 370s. In this embodiment, the optical element 670 is arranged on the arrangement surface 473 of the first holding portion 471 via the optical element base 675. The optical element base 675 is arranged on the arrangement surface 473 and is rotatable around an axis perpendicular to the arrangement surface 473. The optical element base 675 includes a mounting surface 676 parallel to the arrangement surface 473 on the side opposite to the arrangement surface 473 side. The optical element 670 is arranged on this mounting surface 676 so that the light 711 of the first autocollimator 710 is incident on the first reflecting surface 671. Then, the light 711r reflected by the first reflecting surface 671 is received by the first autocollimator 710, and the first autocollimator 710 measures the incident angle of the light 711 incident on the first reflecting surface 671. Based on this measurement result, the optical element base 675 is rotated so that the light 711 emitted from the first autocollimator 710 is perpendicularly incident on the first reflecting surface 671. In this embodiment, the optical element 670 is arranged so that the incident angle of the light 711 on the first reflecting surface 671 is 0.02 mrad or less. Note that the optical element base 675 may be able to change the inclination with respect to the arrangement surface 473. Further, the optical element base 675 is not limited as long as it can arrange the optical element 670.

[0077] (Second Autocollimator Arrangement Step P5) This step is to arrange the second autocollimator 720 such that the light emitted from the second autocollimator 720 is reflected by the second reflecting surface 672 and perpendicularly incident on the incident-side surface 370s. FIG. 12 is a diagram showing the state of this step. As shown in FIG. 12, in this embodiment, the second autocollimator 720 is arranged on the mounting surface 640s of the second stage 640 such that the light 721 from the second autocollimator 720 is reflected by the second reflecting surface 672 and incident on the incident-side surface 370s. The second stage 640 has the same configuration as the first stage 630, and can move in the X, Y, and Z directions of the mounting surface 640s, rotate around an axis parallel to the Y direction of the mounting surface 640s, and tilt around an axis perpendicular to the Y direction of the mounting surface 640s. Then, the light 721r that is reflected in the order of the second reflecting surface 672, the incident-side surface 370s, and the second reflecting surface 672 is received by the second autocollimator 720, and the incident angle of the light 721 incident on the incident-side surface 370s is measured by the second autocollimator 720. Based on this measurement result, the position, inclination, and orientation of the second autocollimator 720 are adjusted by the second stage 640. Then, the light 721 emitted from the second autocollimator 720 is reflected by the second reflecting surface 672 and perpendicularly incident on the incident-side surface 370s. In this embodiment, the second autocollimator 720 is arranged such that the incident angle of the light 721 on the incident-side surface 370s is 0.02 mrad or less.

[0078] (First Mirror Arrangement Step P6) This step involves removing the optical element 670 and arranging the planar mirror 430 such that the light 721 from the second autocollimator 720 is incident perpendicularly on the reflecting surface 431 of the planar mirror 430. FIG. 13 shows the state of this step. As shown in FIG. 13, in this embodiment, first, the optical element 670 and the optical element base 675 are removed from the first holding portion 471. Next, the planar mirror base 490 to which the planar mirror 430 is fixed is attached to the placement surface 473. That is, in this embodiment, the planar mirror 430 is arranged on the placement surface 473 via the planar mirror base 490. The position where the planar mirror base 490 is attached is a position where the light 721 is incident on the reflecting surface 431 of the planar mirror 430 and is on the side opposite to the second autocollimator 720 side from the optical axis of the light 711. Then, the light 721r reflected by the reflecting surface 431 is received by the second autocollimator 720, and the incident angle of the light 721 incident on the reflecting surface 431 is measured by the second autocollimator 720. Based on this measurement result, the inclination of the planar mirror base 490 with respect to the placement surface 473 is adjusted. Then, the light 721 from the second autocollimator 720 is made to be incident perpendicularly on the reflecting surface 431 of the planar mirror 430. In this embodiment, the planar mirror 430 is arranged such that the incident angle of the light 721 on the reflecting surface 431 is 1 mrad or less.

[0079] (Wavefront sensor arrangement step P7) This step is to arrange the wavefront sensor 730 so that the light 711 of the first autocollimator 710 transmitted through the output coupling mirror 370 is incident perpendicularly on the light receiving surface 731. Fig. 14 is a diagram showing the state of this step. The wavefront sensor 730 can measure the incident angle of the incident light and the wavefront aberration of the incident light. In this embodiment, the wavefront sensor 730 is arranged on the mounting surface 650s of the third stage 650 so that the light 711 from the first autocollimator 710 passes through the output coupling mirror 370 and is incident on the light receiving surface 731 of the wavefront sensor 730. The third stage 650 has the same configuration as the first stage 630, and can move in the X, Y, and Z directions of the mounting surface 650s, rotate around an axis parallel to the Y direction of the mounting surface 650s, and tilt around an axis perpendicular to the Y direction of the mounting surface 650s. Then, the incident angle of the light 711 incident on the light receiving surface 731 is measured by the wavefront sensor 730. Based on this measurement result, the position, inclination, and orientation of the wavefront sensor 730 are adjusted by the third stage 650. Then, the light 711 transmitted through the output coupling mirror 370 is made to be incident perpendicularly on the light receiving surface 731. In this embodiment, the wavefront sensor 730 is arranged so that the incident angle of the light 711 on the light receiving surface 731 is 0.05 mrad or less.

[0080] (Pinhole Plate Arrangement Step P8) This step is to arrange the pinhole plate 735 provided with the through hole 736 so that the light 711 passes through the through hole 736. Fig. 15 is a diagram showing the state of this step. The pinhole plate 735 is a light-shielding plate-like member provided with the through hole 736 in the thickness direction. In this embodiment, the pinhole plate 735 is arranged on the arrangement surface 473 so that the optical axis of the light 711 passes through the through hole 736. The size of the through hole 736 is larger than the beam diameter of the light 711, and the light 711 can pass through the through hole 736 without being shielded. The outer shape of the through hole 736 may be a rectangular shape elongated in the Y direction.

[0081] (Reference Light Source Arrangement Step P9) This step is to place a reference light source 740 instead of the first autocollimator 710 so that the emitted light passes through the output coupling mirror 370 and is perpendicularly incident on the light receiving surface 731 of the wavefront sensor 730. FIG. 16 shows the state of this step. The beam diameter of the light 741 emitted from the reference light source 740 is larger than the beam diameter of the light 711 of the first autocollimator 710. For example, the beam diameter of the light 741 is 10 times or more the beam diameter of the light 711 and is 10 mm or more. Also, the beam diameter of the light 741 is larger than the outer shape of the through hole 736 of the pinhole plate 735. In this embodiment, the reference light source 740 is placed on the mounting surface 630s of the first stage 630 instead of the first autocollimator 710. Then, the light 741 of the reference light source 740 passes through the through hole 736, passes through the output coupling mirror 370, and is incident on the light receiving surface 731 of the wavefront sensor 730. Also, the optical axis of the light 741 passes through the through hole 736, and the entire through hole 736 is positioned within the region of the light 741 irradiated on the pinhole plate 735. For this reason, the outer shape of the light 741 that has passed through the through hole 736 has the same shape as the outer shape of the through hole 736.

[0082] Next, the wavefront sensor 730 measures the incident angle of the light 741 incident on the light receiving surface 731. Based on this measurement result, the position, inclination, and orientation of the reference light source 740 are adjusted by the first stage 630. Then, the light 741 is perpendicularly incident on the light receiving surface 731. In this embodiment, the reference light source 740 is placed so that the incident angle of the light 741 on the light receiving surface 731 is 0.02 mrad or less.

[0083] Note that the pinhole plate 735 may be arranged after removing the first autocollimator 710. For example, after arranging the reference light source 740, the pinhole plate 735 may be arranged so that the optical axis of the light 741 passes through the through hole 736.

[0084] (Second mirror arrangement step P10) This step involves arranging the convex mirror 410 and the concave mirror 420. Specifically, the convex mirror 410 is arranged such that it reflects the light 741 from the reference light source 740, causing the beam width of the light 741 to expand and the light 741 to head towards the flat mirror 430. Also, the concave mirror 420 is arranged such that it collimates the expanded beam width of the light 741 reflected by the flat mirror 430 to be constant and reflects the light 741 so that it passes through the output coupling mirror 370 and is incident perpendicularly on the light receiving surface 731 of the wavefront sensor 730.

[0085] Figure 17 is a diagram showing the state of arranging the concave mirror 420. In this embodiment, first, the concave mirror holder 450 with the concave mirror 420 fixed is arranged on the placement surface 473 of the first holding portion 471. That is, the concave mirror 420 is arranged on the placement surface 473 via the concave mirror holder 450. The position where the concave mirror 420 is arranged is on the output coupling mirror 370 side from the pinhole plate 735. The reflecting surface 421 of the concave mirror 420 intersects the optical axis of the light 741 from the reference light source 740. Also, the concave mirror 420 is located on the output coupling mirror 370 side from the flat mirror 430 and is inclined towards the flat mirror 430 side from the output coupling mirror 370 side towards the reference light source 740 side. Also, the focal line 422 of the concave mirror 420 is parallel to the placement surface 473. That is, the position where the concave mirror 420 is arranged is a position that satisfies the above conditions. This position may be predetermined on the placement surface 473 and may be positioned by knock pins, abutting grooves, etc. For this purpose, the concave mirror holder 450 may be provided with holes for fitting knock pins. The thus arranged concave mirror holder 450 is fixed to the placement surface 473 with bolts.

[0086] Next, the convex mirror base 480 is attached to the placement surface 473. The position where the convex mirror base 480 is attached is a position that overlaps the optical axis of the light 741 in a direction perpendicular to the placement surface 473 between the concave mirror 420 and the pinhole plate 735. This position may be predetermined and may be defined by a positioning configuration similar to that of the concave mirror holder 450.

[0087] Next, the convex mirror 410 is arranged. FIG. 18 is a diagram showing the state of arranging the convex mirror 410. FIG. 19 is a diagram of a part of the state shown in FIG. 18 as viewed along the arrow A in FIG. 18. As shown in FIGS. 18 and 19, in the present embodiment, the convex mirror 410 fixed to the convex mirror holder 440 is arranged on the mounting surface 660s of the fourth stage 660 via the support stay 750. The fourth stage 660 has the same configuration as the first stage 630, and can move in the X, Y, and Z directions of the mounting surface 660s, rotate around an axis parallel to the Y direction of the mounting surface 660s, and tilt around an axis perpendicular to the Y direction of the mounting surface 660s. The support stay 750 is a rod-shaped member to which the convex mirror holder 440 is detachably attached at one end, and the other end of the support stay 750 is fixed to the mounting surface 660s. The fourth stage 660 moves the support stay 750 so that the convex mirror holder 440 holds the convex mirror 410 directly above the convex mirror base 480 and the light 741 passing through the through hole 736 of the pinhole plate 735 is incident on the reflecting surface 411 of the convex mirror 410.

[0088] Next, the position, inclination, and orientation of the convex mirror 410 are adjusted by the fourth stage 660. Then, the light 741 reflected by the convex mirror 410 is reflected in the order of the plane mirror 430 and the concave mirror 420 and is incident on the incident side surface 370s. At this time, the convex mirror holder 440 and the main surface 482 of the convex mirror base 480 are separated by a predetermined distance or more. The predetermined distance is, for example, 0.1 mm. The convex mirror 410 reflects the light 741 so that the beam width of the light 741 expands and the light 741 travels toward the plane mirror 430. Further, the concave mirror 420 reflects the light 741 so as to collimate the expanded beam width of the light 741 reflected by the plane mirror 430 to be constant. The light 741 reflected by the concave mirror 420 passes through the output coupling mirror 370 and is incident on the wavefront sensor 730.

[0089] Next, the wavefront sensor 730 measures the incident angle of the light 741 incident on the light receiving surface 731 and the RMS (Root Mean Square) value of the wavefront aberration of the light 741. Based on this measurement result, the position, tilt, and orientation of the convex mirror 410 are adjusted by the fourth stage 660 so that the light 741 transmitted through the output coupling mirror 370 is incident perpendicularly on the wavefront sensor 730. In this way, the focal line 412v in the virtual image 410v of the convex mirror 410 and the focal line 422 of the concave mirror 420 are positioned on the same straight line. In this embodiment, the reference light source 740 is arranged so that the incident angle of the light 741 on the light receiving surface 731 is 0.2 mrad or less and the RMS value of the wavefront aberration of the light 741 is 13.51 nm (0.07 × 193 nm) or less. Note that when not considering the wavefront aberration, it is not necessary to measure the RMS value of the wavefront aberration of the light 741 incident on the light receiving surface 731 by the wavefront sensor 730.

[0090] Next, the fourth stage 660 moves the convex mirror holder 440 in the Y direction by a predetermined distance so that the convex mirror holder 440 approaches the convex mirror base 480. The predetermined distance is shorter than the distance between the convex mirror holder 440 and the convex mirror base 480 before the movement, for example, 0.1 mm. Next, the inclination of the convex mirror base 480 is adjusted so that the main surface 482 of the convex mirror base 480 is in surface contact with the convex mirror holder 440. Next, the fourth stage 660 moves the convex mirror holder 440 in the Y direction by a predetermined distance so that the convex mirror holder 440 moves away from the convex mirror base 480. This predetermined distance is the same as the distance moved when the convex mirror holder 440 is moved closer to the convex mirror base 480. Then, again, the incident angle of the light 741 incident on the light receiving surface 731 and the RMS value of the wavefront aberration of the light 741 are measured, and based on this measurement result, the position, inclination, and orientation of the convex mirror 410 are adjusted by the fourth stage 660 so that the light 741 is incident perpendicularly on the wavefront sensor 730. For this reason, a gap with a predetermined distance is formed between the convex mirror holder 440 and the main surface 482 of the convex mirror base 480 in a state where the light 741 is incident perpendicularly on the wavefront sensor 730. Note that the adjustment of the position, inclination, and orientation of the convex mirror 410 after the convex mirror holder 440 is moved in the Y direction so that the convex mirror holder 440 moves away from the convex mirror base 480 may be omitted. Also, the movement of the convex mirror holder 440 in the Y direction and the adjustment of the convex mirror 410 after the convex mirror 410 is first adjusted may be omitted.

[0091] Next, with the convex mirror holder 440 separated from the convex mirror base 480, the convex mirror holder 440 is fixed to the convex mirror base 480 with an adhesive. The fixing with the adhesive is as described in FIG. 6. After the adhesive is solidified, the support stay 750 is removed from the convex mirror holder 440, and the pinhole plate 735 is removed from the placement surface 473.

[0092] In this way, the beam expander 400 is manufactured. The holding part 470 of the beam expander 400 is attached to the cavity plate 512. As described above, the orientation of the output coupling mirror 370 with respect to the holding part 470 has been adjusted in advance. Therefore, by attaching the holding part 470 to the cavity plate 512, the beam expander 400 is arranged such that the laser light emitted from the chamber device CH3 is incident perpendicularly on the incident-side surface 370s. Then, the gas laser device 100 is manufactured.

[0093] 3.3 Function and Effect The manufacturing method of this embodiment includes a first autocollimator arrangement step P3, an optical element arrangement step P4, a second autocollimator arrangement step P5, and a first mirror arrangement step P6. In the first autocollimator arrangement step P3, the first autocollimator 710 is arranged so as to receive the light 711 that is reflected by the incident-side surface 370s of the output coupling mirror 370 among the emitted light 711 and the light 711 is incident perpendicularly to the incident-side surface 370s. That is, the optical axis of the light 711 can be made perpendicular to the incident-side surface 370s. In the optical element arrangement step P4, the optical element 670 is arranged so as to receive the light 711 that is reflected by the first reflection surface 671 of the optical element 670 among the light 711 emitted from the first autocollimator 710 and the light 711 is incident perpendicularly to the first reflection surface 671. In the second autocollimator arrangement step P5, the second autocollimator 720 is arranged so as to receive the light 721 that is reflected in the order of the second reflection surface 672 of the optical element 670, the incident-side surface 370s, and the second reflection surface 672 among the emitted light 721 and the light 721 is incident perpendicularly to the incident-side surface 370s. The angle formed by the first reflection surface 671 and the second reflection surface 672 is 45°. Therefore, by the second autocollimator arrangement step P5, the optical axis of the light 721 can be made perpendicular to the optical axis of the light 711. In the first mirror arrangement step P6, the plane mirror 430 is arranged so as to receive the light 721 that is reflected by the reflection surface 431 of the plane mirror 430 among the light 721 emitted from the second autocollimator 720 and the light 721 is incident perpendicularly to the reflection surface 431. Since the optical axis of the light 711 is perpendicular to the incident-side surface 370s and the optical axis of the light 721 and the optical axis of the light 711 are perpendicular, the reflection surface 431 of the plane mirror 430 can be made perpendicular to the incident-side surface 370s. Therefore, compared with the case where the plane mirror 430 is arranged at the design position with mechanical accuracy, the deviation amount of the angle formed by the reflection surface 431 and the incident-side surface 370s from perpendicularity can be reduced. Accordingly, according to the manufacturing method of this embodiment, by adjusting the arrangement of the convex mirror 410 and the concave mirror 420, the performance of the laser light can be made to be the design value, and the deviation of the performance of the laser light from the design value can be suppressed.

[0094] In the optical element placement step P4 in the manufacturing method of this embodiment, the optical element 670 is placed on the placement surface 473 via the optical element base 675 that can rotate around an axis perpendicular to the placement surface 473. For this reason, compared with the case where the optical element 670 is directly placed on the placement surface 473 without using the optical element base 675, fine adjustment is easier and it is easier to make the light 711 perpendicularly incident on the first reflection surface 671. Note that the optical element base 675 may be directly placed on the placement surface 473.

[0095] In the second mirror placement step P10 in the manufacturing method of this embodiment, before placing the convex mirror 410, the concave mirror 420 is fixed to the holding portion 470. The convex mirror 410 is located on the side opposite to the output coupling mirror 370 side from the concave mirror 420. For this reason, in the placement of the convex mirror 410, the output coupling mirror 370 is less likely to get in the way compared with the placement of the concave mirror 420. For this reason, compared with the case where the convex mirror 410 is fixed to the holding portion 470 before placing the concave mirror 420, the second mirror placement step P10 can be made easier. Note that the convex mirror 410 may be fixed to the holding portion 470 before placing the concave mirror 420.

[0096] In the second mirror placement step P10 in the manufacturing method of this embodiment, the convex mirror 410 is placed on the holding portion 470 via the convex mirror base 480 whose inclination with respect to the placement surface 473 can be changed. For this reason, compared with the case where the convex mirror 410 is directly placed on the holding portion 470 without using the convex mirror base 480, it is easier to place the convex mirror 410 with its orientation and the like adjusted on the holding portion 470. Note that the concave mirror 420 may be placed on the holding portion 470 via a concave mirror base whose inclination with respect to the placement surface 473 can be changed in the same manner as the convex mirror base 480.

[0097] In the second mirror arrangement step P10 in the manufacturing method of the present embodiment, with the convex mirror holder 440 to which the convex mirror 410 is fixed being separated from the convex mirror base 480, the convex mirror holder 440 is fixed to the convex mirror base 480 with an adhesive. For example, when the convex mirror holder 440 is fixed to the convex mirror base 480 with bolts, the position of the convex mirror 410 may shift, such as the convex mirror holder 440 tilting with respect to the convex mirror base 480 due to the fastening force of the bolts. According to the manufacturing method of the present embodiment, compared with this case, the shift of the position of the convex mirror 410 can be suppressed. Note that the convex mirror holder 440 may be fixed with bolts.

[0098] In the reference light source arrangement step P9 in the manufacturing method of the present embodiment, the reference light source 740 is arranged such that the optical axis of the light 741 passes through the through hole 736 of the pinhole plate 735 provided with the through hole 736 smaller than the beam diameter of the light 741 of the reference light source 740. Also, in the second mirror arrangement step P10, the convex mirror 410 and the concave mirror 420 are arranged on the output coupling mirror 370 side from the pinhole plate 735. Therefore, the outer shape of the light 741 can be made into a shape corresponding to the outer shape of the through hole 736. Therefore, for example, the arrangement of the convex mirror 410 and the concave mirror 420 can be adjusted so that the wavefront aberration characteristics of the laser light with a desired outer shape satisfy the desired requirements.

[0099] The present invention has been described by taking the embodiment as an example, but the above embodiment can be changed as appropriate. For example, although the optical element 670 including the first reflecting surface 671 and the second reflecting surface 672 is a prism, it may be a columnar reflecting member that is non-transmissive to light.

[0100] Also, in the second mirror arrangement step P10, the concave mirror 420 is arranged on the arrangement surface 473 of the holding portion 470 via the concave mirror holder 450. However, the concave mirror 420 may be directly arranged on the arrangement surface 473, and the concave mirror 420 may be arranged on a surface different from the arrangement surface 473 on which the plane mirror 430 is arranged.

[0101] Also, in the second mirror arrangement step P10, the convex mirror 410 was arranged on the convex mirror base 480 via the convex mirror holder 440. However, the convex mirror 410 may be directly arranged on the convex mirror base 480. Also, the convex mirror 410 may be directly arranged on the holding portion 470, for example, directly on the arrangement surface 473.

[0102] Also, the manufacturing method of the above embodiment was a manufacturing method of the beam expander 400 as an optical module. However, the optical module is not limited to the beam expander 400.

[0103] Also, the manufacturing method of the above embodiment included the pinhole plate arrangement step P8, but may not include the pinhole plate arrangement step P8.

[0104] The above description is intended to be illustrative rather than restrictive. Therefore, it is obvious to those skilled in the art that the embodiments of the present disclosure can be modified without departing from the scope of the claims. Also, it is obvious to those skilled in the art that the embodiments of the present disclosure can be used in combination. The terms used throughout this specification and the claims should be construed as "non-limiting" terms unless otherwise specified. For example, terms such as "including", "having", "comprising", "equipped with" should be construed as "not excluding the existence of components other than those described". Also, the modifier "one" should be construed to mean "at least one" or "one or more". Also, the term "at least one of A, B, and C" should be construed as "A", "B", "C", "A + B", "A + C", "B + C", or "A + B + C", and further should be construed to include combinations with those other than "A", "B", and "C".

Claims

1. A method for manufacturing an optical module including an output coupling mirror that transmits part of a laser beam and reflects the other part of the laser beam, and a plane mirror including a reflecting surface in a plane perpendicular to the surface of the output coupling mirror on the incident side of the laser beam, comprising: a first autocollimator arranging step of arranging the first autocollimator so as to receive light reflected by the incident side surface among the light emitted from the first autocollimator and so that the light is incident perpendicularly to the incident side surface; an optical element arranging step of arranging, between the incident side surface and the first autocollimator, an optical element including a first reflecting surface facing the first autocollimator and a second reflecting surface facing the incident side surface at an angle of 45° with respect to the first reflecting surface so as to receive light reflected by the first reflecting surface among the light emitted from the first autocollimator and so that the light is incident perpendicularly to the first reflecting surface; a second autocollimator arranging step of arranging the second autocollimator so as to receive light reflected in the order of the second reflecting surface, the incident side surface, and the second reflecting surface among the emitted light and so that the light is incident perpendicularly to the incident side surface; a first mirror arranging step of removing the optical element and arranging the plane mirror so as to receive light reflected by the reflecting surface of the plane mirror among the light emitted from the second autocollimator and so that the light is incident perpendicularly to the reflecting surface; comprising a method for manufacturing an optical module.

2. The method for manufacturing an optical module according to claim 1, wherein the optical element is a prism in which the first reflecting surface and the second reflecting surface are each part of a side surface.

3. The method for manufacturing an optical module according to claim 1, wherein the optical module further includes a holding portion that holds the output coupling mirror, and in the first mirror arranging step, the plane mirror is arranged on the holding portion.

4. The method for manufacturing an optical module according to claim 3, wherein the holding portion includes an arrangement surface on which the plane mirror is arranged, and in the optical element arranging step, the optical element is arranged on the arrangement surface via an optical element base rotatable about an axis perpendicular to the arrangement surface.

5. The method for manufacturing an optical module according to claim 3, wherein the holding portion includes an arrangement surface on which the plane mirror is arranged, and in the first mirror arranging step, the plane mirror is arranged on the arrangement surface via a plane mirror base whose inclination with respect to the arrangement surface can be changed.

6. The manufacturing method of the optical module according to claim 1, wherein the optical module further includes a convex mirror and a concave mirror, after the first mirror arrangement step, a wavefront sensor arrangement step of arranging the wavefront sensor so that the light of the first autocollimator transmitted through the output coupling mirror is incident perpendicularly on the light receiving surface of the wavefront sensor; a reference light source arrangement step of arranging a reference light source having a beam diameter of emitted light larger than the beam diameter of the light of the first autocollimator so that the light of the reference light source is transmitted through the output coupling mirror and is incident perpendicularly on the light receiving surface of the wavefront sensor, instead of the first autocollimator; a second mirror arrangement step of arranging the convex mirror and the concave mirror; further comprising in the second mirror arrangement step, the convex mirror is arranged so that the beam width of the light from the reference light source is expanded and the light is reflected so as to be directed toward the plane mirror, the concave mirror is arranged so as to collimate the expanded beam width of the light reflected by the plane mirror to be constant and to reflect the light so that the light is transmitted through the output coupling mirror and is incident perpendicularly on the light receiving surface of the wavefront sensor.

7. The manufacturing method of the optical module according to claim 6, wherein the optical module further includes a holding portion that holds the output coupling mirror, in the second mirror arrangement step, the convex mirror and the concave mirror are arranged on the holding portion.

8. The manufacturing method of the optical module according to claim 7, wherein in the second mirror arrangement step, before arranging the convex mirror, the concave mirror is fixed to the holding portion.

9. The manufacturing method of the optical module according to claim 7, wherein the holding portion includes an arrangement surface on which the plane mirror is arranged, in the second mirror arrangement step, the convex mirror is arranged on the holding portion via a convex mirror base whose inclination with respect to the arrangement surface can be changed.

10. The manufacturing method of the optical module according to claim 9, wherein in the second mirror arrangement step, the convex mirror is arranged on the convex mirror base via a convex mirror holder.

11. The manufacturing method of the optical module according to claim 10, wherein in the second mirror arrangement step, with the convex mirror holder separated from the convex mirror base, the convex mirror holder is fixed to the convex mirror base with an adhesive.

12. The manufacturing method of the optical module according to claim 6, wherein in the reference light source arrangement step, the reference light source is arranged so that the optical axis of the light exiting through the through hole of the pinhole plate provided with a through hole smaller than the beam diameter of the light of the reference light source passes through; in the second mirror arrangement step, the convex mirror and the concave mirror are arranged on the output coupling mirror side from the pinhole plate.

13. A gas laser device manufacturing method comprising: a chamber device that amplifies laser light output from a laser oscillator; an output coupling mirror that transmits a part of the laser light exiting from the chamber device and reflects the other part of the laser light exiting from the chamber device back into the chamber device; and an optical module including a planar mirror including a reflecting surface on a plane perpendicular to the surface on the incident side of the laser light of the output coupling mirror. A first autocollimator arrangement step of arranging the first autocollimator so as to receive the light reflected by the incident side surface among the light emitted by the first autocollimator and so that the light is incident perpendicularly to the incident side surface; An optical element including a first reflecting surface facing the first autocollimator and a second reflecting surface facing the incident side surface at an angle of 45° with respect to the first reflecting surface is arranged between the incident side surface and the first autocollimator so as to receive the light reflected by the first reflecting surface among the light emitted by the first autocollimator and so that the light is incident perpendicularly to the first reflecting surface. A second autocollimator arrangement step of arranging the second autocollimator so as to receive the light reflected in the order of the second reflecting surface, the incident side surface, and the second reflecting surface among the emitted light and so that the light is incident perpendicularly to the incident side surface; A first mirror arrangement step of removing the optical element and arranging the planar mirror so as to receive the light reflected by the reflecting surface of the planar mirror among the light emitted by the second autocollimator and so that the light is incident perpendicularly to the reflecting surface; The optical module manufactured by the manufacturing method of the optical module comprising the above steps is arranged so that the laser light emitted from the chamber device is incident perpendicularly on the surface on the incident side of the output coupling mirror. The manufacturing method of a gas laser device.

14. An output coupling mirror that transmits part of the laser light and reflects the other part of the laser light, and a plane mirror including a reflecting surface in a plane perpendicular to the surface on the incident side of the laser light of the output coupling mirror, which is a manufacturing jig for an optical module, a first autocollimator arranged such that the emitted light is incident perpendicularly to the surface on the incident side of the output coupling mirror, an optical element disposed between the incident side surface and the first autocollimator, including a first reflecting surface facing the first autocollimator and a second reflecting surface facing the incident side surface at an angle of 45° to the first reflecting surface, with the light emitted from the first autocollimator incident perpendicularly on the first reflecting surface, a second autocollimator arranged such that the emitted light is reflected by the second reflecting surface and incident perpendicularly on the incident side surface, comprising a manufacturing jig for an optical module.

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