Laser device and method of producing electronic device

Abstract

This laser device is provided with: a first optical resonator including a first rear mirror and a first output coupling mirror; and a first laser chamber in which a laser gas is sealed and which comprises a pair of first discharge electrodes constituting a discharge space through which a first light beam traveling to and from the first optical resonator passes, a first cross flow fan for circulating the laser gas inside the first laser chamber, a first flow-rectifying guide for guiding the laser gas inside the first laser chamber to between the first discharge electrodes, and a pair of first windows located on an optical path of the first light beam, the first laser chamber being tilted in the longitudinal direction of a cross-section of the first light beam with respect to a first optical axis defined by the first optical resonator.

Description

Laser device and method for manufacturing electronic device

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

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

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

[0004] JP 2012-094750 A U.S. Patent Application Publication No. 2008 / 0037609 JP 2007-221053 A overview

[0005] A laser device according to one aspect of the present disclosure comprises: a first optical resonator including a first rear mirror and a first output coupling mirror; a first laser chamber in which laser gas is sealed, the first laser chamber including a pair of first discharge electrodes that form a discharge space through which a first light beam passes as it travels back and forth through the first optical resonator; a first cross-flow fan that circulates the laser gas in the first laser chamber; a first rectifying guide that guides the laser gas in the first laser chamber to between the first discharge electrodes; and a pair of first windows located in the optical path of the first light beam, the first laser chamber being inclined in the longitudinal direction of the cross section of the first light beam with respect to a first optical axis defined by the first optical resonator.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure includes generating laser light by a laser apparatus including: a first optical resonator including a first rear mirror and a first output coupling mirror; a first laser chamber in which laser gas is sealed, the first laser chamber including a pair of first discharge electrodes that form a discharge space through which a first optical beam passes as it travels back and forth through the first optical resonator; a first cross-flow fan that circulates the laser gas in the first laser chamber; a first rectifying guide that guides the laser gas in the first laser chamber to between the first discharge electrodes; and a pair of first windows located in the optical path of the first optical beam, the first laser chamber being inclined in the longitudinal direction of the cross section of the first optical beam with respect to a first optical axis defined by the first optical resonator; outputting the laser light to an exposure apparatus; and exposing the laser light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device.

[0007] Some embodiments of the present disclosure are described below, by way of example only, with reference to the accompanying drawings. FIG. 1 schematically illustrates the configuration of a laser device according to a comparative example. FIG. 2 illustrates a portion of the power oscillator illustrated in FIG. 1 as viewed in the −Z direction. FIG. 3 is a diagram illustrating acoustic waves generated inside a laser chamber. FIG. 4 conceptually illustrates the refractive index distribution between discharge electrodes of a comparative example. FIG. 5 schematically illustrates the configuration of a laser device according to a first embodiment. FIG. 6 conceptually illustrates the refractive index distribution between discharge electrodes of the first embodiment. FIG. 7 illustrates simulation results of the light intensity distribution in the V direction of the beam cross section of laser light output from a power oscillator. FIG. 8 illustrates the dimensions of each portion of the discharge electrode and the slit. FIG. 9 schematically illustrates the configuration of a laser device according to a first modification. FIG. 10 schematically illustrates the configuration of a laser device according to a second modification. FIG. 11 schematically illustrates the configuration of a laser device according to a third modification. FIG. 12 schematically illustrates the configuration of a laser device according to a fourth modification. Fig. 13 is a schematic diagram showing the configuration of a laser apparatus according to a second embodiment, Fig. 14 is a schematic diagram showing the configuration of a laser apparatus according to a fifth modified example, and Fig. 15 is a schematic diagram showing the configuration of an exposure apparatus connected to the laser apparatus. Embodiment

[0008] <Contents> 1. Comparative Example 1.1 Configuration of Laser Apparatus 1 1.1.1 Master Oscillator MO 1.1.2 Power Oscillator PO 1.2 Operation 1.2.1 Master Oscillator MO 1.2.2 Beam Steering Unit 30 1.2.3 Power Oscillator PO 1.2.4 Laser Gas Flowing in Discharge Space DS 1.3 Issues with the Comparative Example 2. Laser Apparatus 1a with Laser Chamber 10 Tilted 2.1 Configuration 2.2 Suppression of Imbalance in Refractive Index Distribution 2.3 Inclination Δθ of Longitudinal Direction of Discharge Electrodes 11a and 11b with Respect to Optical Axis A1 2.4 Function 3. Wheels 18g and 18h ​​with Different Diameters 3.1 Configuration 3.2 Function 4. Example of Tilting Laser Chamber 20 of Master Oscillator MO 4.1 Configuration 4.2 Function 5. 5. Example of tilting both laser chambers 10 and 20 5.1 Structure 5.2 Operation 6. Example of not including power oscillator PO 7. Laser device 1f with tilted optical resonator 7.1 Structure 7.2 Operation 8. Example of tilting cavity plates 19e and 19f 8.1 Structure 8.2 Operation 9. Others

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

[0010] 1. Comparative Example 1.1 Configuration of Laser Apparatus 1 Figure 1 schematically shows the configuration of a laser apparatus 1 according to a comparative example. The comparative example of the present disclosure is a configuration that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges. The laser apparatus 1 includes a master oscillator MO, a power oscillator PO, and a beam steering unit 30. The beam steering unit 30 includes high-reflection mirrors 31 and 32.

[0011] 1.1.1 Master Oscillator MO The master oscillator MO includes a laser chamber 20, a rear mirror 24, an output coupling mirror 25, a pair of slits 26a and 26b, a pair of rails 28a and 28b, a plurality of wheels 28c and 28d, and a pair of cavity plates 29a and 29b. The rear mirror 24 and the output coupling mirror 25 constitute an optical resonator. The rear mirror 24 includes a prism 24b and a grating 24c and constitutes a line narrowing module. Alternatively, the rear mirror 24 may be a highly reflective mirror. The output coupling mirror 25 is a partially reflective mirror. The laser chamber 20 is disposed in the optical path of the optical resonator.

[0012] The laser chamber 20 includes a pair of windows 20a and 20b, a pair of discharge electrodes 21a and 21b, rectifying guides 22a and 22b, and a cross-flow fan 27. The windows 20a and 20b are located in the optical path of the light beam B2 that travels back and forth through the optical resonator.

[0013] The direction of travel of the light beam B2 going back and forth through the optical resonator is defined as the Z direction or the −Z direction. The direction of discharge between the discharge electrodes 21a and 21b is defined as the V direction or the −V direction. The Z direction and the V direction are perpendicular to each other, and the direction perpendicular to both of these directions is defined as the H direction or the −H direction.

[0014] The laser chamber 20 is filled with a laser gas containing, for example, argon gas or krypton gas as a rare gas, fluorine gas as a halogen gas, and neon gas as a buffer gas. Alternatively, a laser gas containing fluorine gas and a buffer gas may be filled.

[0015] An opening is formed in a part of the laser chamber 20, and this opening is blocked by an electrical insulator 23. The electrical insulator 23 supports the discharge electrode 21a. A plurality of conductive parts 23a are embedded in the electrical insulator 23. Each of the conductive parts 23a is electrically connected to the discharge electrode 21a. A pulse power supply (not shown) is connected to the discharge electrode 21a via the conductive parts 23a.

[0016] A return plate 20c is disposed inside the laser chamber 20. The discharge electrode 21b is supported by the return plate 20c. The discharge electrode 21b is electrically connected to ground potential via the return plate 20c and a conductive member of the laser chamber 20. The return plate 20c has gaps (see FIG. 2) on the front and back sides of the paper surface of FIG. 1 for allowing the laser gas to pass through.

[0017] The cross flow fan 27 is supported by bearings 20 e and 20 f and is connected to a motor 27 a disposed outside the laser chamber 20 .

[0018] The slit 26a is disposed between the output coupling mirror 25 and the laser chamber 20, and the slit 26b is disposed between the rear mirror 24 and the laser chamber 20. The slits 26a and 26b are configured to limit the beam width in the V direction of the light beam B2 traveling back and forth through the optical resonator.

[0019] The rails 28a and 28b are respectively disposed near the ends in the -Z direction and the Z direction of the laser chamber 20. The H direction, which is the longitudinal direction of each of the rails 28a and 28b, corresponds to the chamber movement direction.

[0020] Wheels 28c and 28d are also arranged near the ends in the -Z direction and the Z direction, respectively, of the laser chamber 20. When the wheels 28c and 28d move along the rails 28a and 28b, respectively, the laser chamber 20 moves along the rails 28a and 28b, allowing installation and maintenance of the laser chamber 20.

[0021] The rear mirror 24 is supported by a cavity plate 29b via a holder 24a, and the output coupling mirror 25 is supported by a cavity plate 29a via a holder 25a. The cavity plates 29a and 29b are supported by a base plate 29c.

[0022] The rails 28a and 28b and the wheels 28c and 28d are not limited to being arranged near the ends of the laser chamber 20 in the -Z direction and the Z direction, but may be arranged on either side of a plane parallel to the VH plane and passing through the center of gravity of the laser chamber 20. Furthermore, the rails 28a and 28b are not limited to being fixed to the base plate 29c, and the wheels 28c and 28d are supported rotatably with respect to the laser chamber 20, but the rails 28a and 28b may be fixed to the laser chamber 20, and the wheels 28c and 28d may be supported rotatably with respect to the base plate 29c.

[0023] 1.1.2 Power Oscillator PO The components of the power oscillator PO may be substantially the same as the above-described components of the master oscillator MO. While the reference numerals of the components of the master oscillator MO are prefixed with "2," the reference numerals of the components of the power oscillator PO are prefixed with "1."

[0024] However, the rear mirror 24 included in the master oscillator MO constitutes a line narrowing module, whereas the rear mirror 14 included in the power oscillator PO is a partially reflecting mirror. The rear mirror 14 has a higher reflectivity than the output coupling mirror 15.

[0025] 1.2 Operation 1.2.1 Master Oscillator MO In the master oscillator MO, a pulsed power supply connected to the discharge electrode 21a generates a pulsed high voltage. When this high voltage is applied between the discharge electrodes 21a and 21b, a discharge occurs in the discharge space between the discharge electrodes 21a and 21b. The energy of this discharge excites the laser medium in the laser chamber 20 and causes it to transition to a higher energy level. When the excited laser medium subsequently transitions to a lower energy level, it emits light with a wavelength corresponding to the difference in energy levels.

[0026] Light generated within the laser chamber 20 is emitted to the outside of the laser chamber 20 through the windows 20a and 20b. The beam width of the light emitted from the window 20b of the laser chamber 20 in the H direction is expanded by the prism 24b, and the light is incident on the grating 24c.

[0027] Light incident on grating 24c is reflected by the multiple grooves of grating 24c and diffracted in a direction according to the wavelength of the light. The wavelength of the diffracted light incident on prism 24b from grating 24c is selected by matching the angle of incidence of the light incident on grating 24c with the diffraction angle of the diffracted light of the desired wavelength. Prism 24b reduces the beam width in the H direction of the diffracted light incident on grating 24c and returns the light to laser chamber 20 via window 20b.

[0028] The output coupling mirror 25 transmits and outputs a portion of the light emitted from the window 20 a of the laser chamber 20 , and reflects the other portion back into the laser chamber 20 .

[0029] In this way, the light emitted from the laser chamber 20 travels back and forth along the optical axis A2 defined by the optical resonator between the rear mirror 24 and the output coupling mirror 25, and is amplified each time it passes through the discharge space between the discharge electrodes 21 a and 21 b. This light is narrowed in line each time it is reflected by the rear mirror 24 that constitutes the line narrowing module. The light thus oscillated and narrowed in line is output from the output coupling mirror 25 as laser light.

[0030] 1.2.2 Beam steering unit 30 The beam steering unit 30 guides the laser beam output from the master oscillator MO to the rear mirror 14 of the power oscillator PO. The beam steering unit 30 is capable of adjusting the optical axis of the laser beam so that the laser beam is incident on the rear mirror 14 of the power oscillator PO in a desired incident direction.

[0031] 1.2.3 Power Oscillator PO In the power oscillator PO, a pulsed power supply connected to the discharge electrode 11a generates a pulsed high voltage. The discharge timing of the master oscillator MO and the power oscillator PO is controlled so that the timing when a discharge occurs between the discharge electrodes 11a and 11b is synchronized with the timing when the laser light output from the master oscillator MO enters the laser chamber 10 via the rear mirror 14 and the window 10b.

[0032] The light beam B1, which is a laser beam, travels back and forth along the optical axis A1 defined by the optical resonator between the rear mirror 14 and the output coupling mirror 15, and is amplified each time it passes through the discharge space between the discharge electrodes 11 a and 11 b. The amplified laser beam is output from the output coupling mirror 15.

[0033] 1.2.4 Laser Gas Flowing in the Discharge Space DS Figure 2 shows a portion of the power oscillator PO shown in Figure 1, viewed from the -Z direction. A light beam B1 passes through the discharge space DS defined between the discharge electrodes 11a and 11b. Near the discharge electrodes 11a and 11b, localized discharge concentration can cause beam divergence and unstable spectral width. Therefore, beam quality is ensured by blocking the light beams passing near the discharge electrodes 11a and 11b with slits 16a and 16b (see Figure 1). As a result, the beam width in the V direction of the light beam B1 traveling back and forth in the optical resonator is narrower than the width of the discharge space DS in the V direction. Meanwhile, the beam width in the H direction of the light beam B1 is smaller than the beam width in the V direction and is approximately equal to the width of the discharge electrodes 11a and 11b in the H direction. The longitudinal direction of the cross section of the light beam B1 corresponds to the V direction.

[0034] When the motor 17a rotates the cross flow fan 17 around the rotation axis Acff1, the laser gas flows as shown by the arrow C in Fig. 2 and circulates inside the laser chamber 10. The discharge products generated by the discharge between the discharge electrodes 11a and 11b are removed from the discharge space DS by the flow of the laser gas before the next discharge occurs, and the discharge space DS and its vicinity become less susceptible to discharge products, allowing the discharge to be stabilized.

[0035] The flow rectifying guides 12a and 12b guide the laser gas between the discharge electrodes 11a and 11b. The flow rectifying guides 12a and 12b are tapered to allow the laser gas to flow efficiently.

[0036] 2 shows the components of the power oscillator PO, but the components of the master oscillator MO are similar. The crossflow fan 27 rotates around a rotation axis Acff2 (see FIG. 1).

[0037] 1.3 Issues of the Comparative Example FIG. 3 is a diagram illustrating acoustic waves W1 and W2 generated inside the laser chamber 10. FIG. 3 corresponds to FIG. 2 , in which the arrow C indicating the gas flow is omitted, but instead shows the acoustic waves W1 and W2. In the discharge space DS between the discharge electrodes 11a and 11b, gas compression waves are generated by excitation and heating of the gas in the discharge space DS in synchronization with the discharge timing. The compression waves generated in the discharge space DS propagate through the space inside the laser chamber 10. This compression wave is called acoustic wave W1. The acoustic wave W1 is reflected by components inside the laser chamber 10, such as the cross-flow fan 17 and the rectifying guides 12a and 12b. When the reflected acoustic wave W2 reaches the discharge space DS, the refractive index distribution in the discharge space DS becomes non-uniform due to the density of the laser gas. Each light ray included in the light beam B1 traveling back and forth through the optical resonator is bent according to the refractive index gradient, which can result in a non-uniform light intensity distribution in the cross section of the light beam B1.

[0038] 4 conceptually illustrates the refractive index distribution between the discharge electrodes 11a and 11b of the comparative example. Each curve shown between the discharge electrodes 11a and 11b indicates the refractive index distribution in the discharge direction at each position along the optical path of the light beam B1. This refractive index distribution is not uniform in the discharge direction between the discharge electrodes 11a and 11b, but is approximately uniform in the longitudinal direction of the discharge electrodes 11a and 11b. In this case, the effect of the refractive index distribution on the light beam B1 is integrated along the longitudinal direction of the discharge electrodes 11a and 11b, which causes a bias in the light intensity distribution in the beam cross section, which may cause local damage to optical elements such as the output coupling mirror 15.

[0039] One possible solution is to tilt the discharge electrodes 11 a and 11 b with respect to the optical axis A1 defined by the optical resonator so that the refractive index distribution in the longitudinal direction of the discharge electrodes 11 a and 11 b is not uniform. However, tilting the discharge electrodes 11 a and 11 b reduces the flow rate of the laser gas in the discharge space DS, and this reduces laser performance such as the pulse energy stability of the laser light.

[0040] Although the problem of the acoustic waves W1 and W2 in the power oscillator PO has been described here, the same problem also occurs in the master oscillator MO.

[0041] Some of the embodiments described below relate to suppressing the occurrence of bias in the light intensity distribution in the beam cross section and suppressing a decrease in the flow rate of the laser gas in the discharge space DS.

[0042] 2. Laser Apparatus 1a Inclined Together with Laser Chamber 10 2.1 Configuration Figure 5 schematically shows the configuration of the laser apparatus 1a according to the first embodiment. In the laser apparatus 1a, the laser chamber 10 of the power oscillator PO, together with the discharge electrodes 11a and 11b, crossflow fan 17, and rectifying guides 12a and 12b housed in the laser chamber 10, is arranged tilted in the V direction with respect to the optical axis A1 defined by the optical resonator of the power oscillator PO. The longitudinal direction of the discharge electrodes 11a and 11b and the rotation axis Acff1 of the crossflow fan 17 are approximately parallel, and the longitudinal direction of the discharge electrodes 11a and 11b and the longitudinal direction of the rectifying guides 12a and 12b are approximately parallel.

[0043] Instead of the rails 18a and 18b in the comparative example, rails 18e and 18f are used in the first embodiment. The lengths of the rails 18e and 18f along the V direction are different from each other, so that the laser chamber 10 is disposed at an angle.

[0044] The laser chamber 10 in the first embodiment corresponds to the first laser chamber in this disclosure, and the windows 10a and 10b in the first embodiment correspond to the first window in this disclosure. The discharge electrodes 11a and 11b in the first embodiment correspond to the first discharge electrode in this disclosure, and the rectifying guides 12a and 12b in the first embodiment correspond to the first rectifying guide in this disclosure. The rear mirror 14 in the first embodiment corresponds to the first rear mirror in this disclosure, the output coupling mirror 15 in the first embodiment corresponds to the first output coupling mirror in this disclosure, and the optical resonator formed by the rear mirror 14 and the output coupling mirror 15 in the first embodiment corresponds to the first optical resonator in this disclosure. The crossflow fan 17 in the first embodiment corresponds to the first crossflow fan in this disclosure. The optical axis A1 in the first embodiment corresponds to the first optical axis in this disclosure, and the light beam B1 in the first embodiment corresponds to the first light beam in this disclosure.

[0045] The laser chamber 20 of the master oscillator MO is the same as that of the comparative example.

[0046] The laser chamber 20 in the first embodiment corresponds to the second laser chamber in this disclosure, and the windows 20a and 20b in the first embodiment correspond to the second window in this disclosure. The discharge electrodes 21a and 21b in the first embodiment correspond to the second discharge electrodes in this disclosure, and the rectifying guides 22a and 22b in the first embodiment correspond to the second rectifying guides in this disclosure. The rear mirror 24 in the first embodiment corresponds to the second rear mirror in this disclosure, the output coupling mirror 25 in the first embodiment corresponds to the second output coupling mirror in this disclosure, and the optical resonator formed by the rear mirror 24 and the output coupling mirror 25 in the first embodiment corresponds to the second optical resonator in this disclosure. The crossflow fan 27 in the first embodiment corresponds to the second crossflow fan in this disclosure. The optical axis A2 in the first embodiment corresponds to the second optical axis in this disclosure, and the light beam B2 in the first embodiment corresponds to the second light beam in this disclosure.

[0047] The optical axis A1 and the optical axis A2 are substantially parallel to each other. Note that a case where the optical axis A1 and the optical axis A2 are not parallel to each other will be described later with reference to FIGS.

[0048] 2.2 Suppression of Imbalance in Refractive Index Distribution FIG. 6 conceptually illustrates the refractive index distribution between the discharge electrodes 11a and 11b in the first embodiment. By tilting the laser chamber 10, the longitudinal direction of the rotation axis Acff1 of the crossflow fan 17, which reflects the acoustic wave W1 to generate the acoustic wave W2, and the rectifying guides 12a and 12b remain substantially parallel to the longitudinal direction of the discharge electrodes 11a and 11b. Therefore, the refractive index distribution remains uniform in the longitudinal direction of the discharge electrodes 11a and 11b, while the discharge electrodes 11a and 11b are tilted. As a result, each of the light rays contained in the light beam B1 passes through a high refractive index portion and a low refractive index portion, which cancels out the effect of the refractive index distribution on the light beam B1, thereby suppressing imbalance in the light intensity distribution in the beam cross section.

[0049] By tilting the discharge electrodes 11a and 11b, there is a possibility that part of the light beam that passes near the discharge electrode 11a or 11b will not be blocked by the slit 16a or 16b and will be output as laser light. However, by tilting the discharge electrodes 11a and 11b, the distance between the discharge electrode 11a or 11b and the light beam B1 changes along the traveling direction of the light beam B1, and therefore it is thought that the adverse effects of localized concentration of discharge will be mitigated.

[0050] FIG. 7 shows the results of a simulation of the light intensity distribution in the V direction of the beam cross section of the laser light output from the power oscillator PO. The horizontal axis of FIG. 7 indicates the position in the V direction, and the total beam width in the V direction approximately coincides with the slit length Vslit (see FIG. 8 ). The vertical axis of FIG. 7 indicates the normalized value obtained by integrating the light intensity in the H direction. In the first embodiment, when the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is set to 4 mrad, the peak intensity is reduced to 87% compared to when the inclination Δθ is set to 0 mrad in the comparative example. If damage to the optical element is attributed to two-photon absorption, the probability of two-photon absorption occurring is proportional to the square of the light intensity, so the life of the optical element is expected to be extended by approximately 1.35 times compared to the comparative example.

[0051] 2.3 Inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b with respect to the optical axis A1 Figure 8 shows the dimensions of each part of the discharge electrodes 11a and 11b and the slits 16a and 16b. The length along the longitudinal direction of each of the discharge electrodes 11a and 11b is taken as electrode length L [m], and the distance between the discharge electrodes 11a and 11b along the V direction is taken as gap length Vgap [mm]. The distance between the slits 16a and 16b along the V direction is taken as slit length Vslit [mm]. The slit length Vslit is smaller than the gap length Vgap.

[0052] The slit axis Aslit defined by the center of each of the slits 16a and 16b is approximately parallel to the optical axis A1 defined by the optical resonator, and it is desirable that the longitudinal inclination Δθ [mrad] of the discharge electrodes 11a and 11b relative to the optical axis A1 be greater than the inclination of the slit axis Aslit relative to the optical axis A1.

[0053] When the discharge electrodes 11a and 11b are not tilted, the effective discharge range is Vgap, whereas when the discharge electrodes 11a and 11b are tilted by Δθ, the effective discharge range can be approximated as Vgap-Δθ·L. It is desirable that Vgap-Δθ·L be equal to or greater than the slit length Vslit as follows: Vgap-Δθ·L≧Vslit

[0054] In this embodiment, the slope Δθ is greater than 0, so the slope Δθ is preferably in the following range: 0<Δθ≦(Vgap−Vslit) / L

[0055] The above approximation is valid because Vgap is sufficiently small with respect to the electrode length L, and furthermore, by taking the difference between Vgap and Vslit, a more accurate approximation can be obtained.

[0056] Here, if the electrode length L is 0.7 m, the gap length Vgap is 15 mm, and the slit length Vslit is 10 mm, the slope Δθ falls within the following range: 0 mrad<Δθ≦7.1 mrad

[0057] If the distance between the two slits 16a and 16b in an actual product is, for example, 1 m, and the tolerance of the V-direction positions of the slits 16a and 16b is several hundred μm, the slit axis Aslit may vary by about 0.2 mrad. Also, the laser light has a beam divergence angle of about 1 mrad to 3 mrad. Therefore, the tilt Δθ is preferably 1 mrad or more as follows: 1 mrad≦Δθ≦7.1 mrad

[0058] More preferably, the inclination Δθ is 3 mrad or more as follows: 3 mrad≦Δθ≦7.1 mrad

[0059] 2.4 Operation (1) The laser device 1a according to the first embodiment includes a first optical resonator including a rear mirror 14 and an output coupling mirror 15, and a laser chamber 10 in which laser gas is sealed. The laser chamber 10 includes a pair of discharge electrodes 11a and 11b that form a discharge space DS through which a light beam B1 traveling back and forth in the first optical resonator passes, a cross-flow fan 17 that circulates the laser gas within the laser chamber 10, rectifying guides 12a and 12b that guide the laser gas within the laser chamber 10 between the discharge electrodes 11a and 11b, and a pair of windows 10a and 10b located in the optical path of the light beam B1, and is inclined in the V direction, which is the longitudinal direction of the cross section of the light beam B1, with respect to an optical axis A1 defined by the first optical resonator.

[0060] According to this, by tilting the entire laser chamber 10 including the discharge electrodes 11 a and 11 b, the cross flow fan 17, and the rectifying guides 12 a and 12 b, the discharge space DS, which has a refractive index distribution in the longitudinal direction of the cross section of the light beam B1, is tilted with respect to the optical axis A1, so that each of the light rays contained in the light beam B1 passes through a portion with a high refractive index and a portion with a low refractive index. This cancels out the effect of the refractive index distribution on the light beam B1, and suppresses bias in the light intensity distribution in the cross section of the light beam B1.

[0061] (2) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11 a and 11 b relative to the optical axis A 1 is greater than the inclination of the longitudinal direction of the discharge electrodes 11 a and 11 b relative to the rotation axis Acff 1 of the cross flow fan 17 .

[0062] According to this, by reducing the longitudinal inclination of the discharge electrodes 11a and 11b relative to the rotation axis Acff1 of the cross flow fan 17, the refractive index distribution in the longitudinal direction of the discharge electrodes 11a and 11b becomes uniform, and bias in the light intensity distribution in the cross section of the light beam B1 when the laser chamber 10 is tilted relative to the optical axis A1 is suppressed.

[0063] (3) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is greater than the inclination of the longitudinal direction of the discharge electrodes 11a and 11b relative to the longitudinal direction of the rectifying guides 12a and 12b.

[0064] According to this, by reducing the inclination of the longitudinal direction of the discharge electrodes 11a and 11b with respect to the longitudinal direction of the rectifying guides 12a and 12b, the refractive index distribution in the longitudinal direction of the discharge electrodes 11a and 11b becomes uniform, and bias in the light intensity distribution in the cross section of the light beam B1 when the laser chamber 10 is inclined with respect to the optical axis A1 is suppressed.

[0065] (4) According to the first embodiment, the laser device 1a further includes a pair of slits 16a and 16b, the slit length Vslit along the longitudinal direction of the cross section of the light beam B1 being smaller than the gap length Vgap between the discharge electrodes 11a and 11b. The laser chamber 10 is disposed between the rear mirror 14 and the output coupling mirror 15, and the slits 16a and 16b are disposed between the rear mirror 14 and the laser chamber 10 and between the output coupling mirror 15 and the laser chamber 10.

[0066] With this, even if the laser chamber 10 is tilted, the beam width of the light beam B1 in the V direction can be defined by the slits 16a and 16b, and the quality of the laser light output from the power oscillator PO can be maintained.

[0067] (5) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is greater than the inclination of the slit axis Aslit defined by the center of each of the slits 16a and 16b relative to the optical axis A1.

[0068] According to this, by reducing the inclination of the slit axis Aslit relative to the optical axis A1, the beam width of the light beam B1 in the V direction can be made equivalent to the slit length Vslit, and the quality of the laser light output from the power oscillator PO can be maintained.

[0069] (6) According to the first embodiment, when the length of the discharge electrodes 11a and 11b along the longitudinal direction is L, the inclination Δθ of the discharge electrodes 11a and 11b in the longitudinal direction with respect to the optical axis A1 is in the following range: 0<Δθ≦(Vgap−Vslit) / L

[0070] This allows the laser chamber 10 to be tilted within a range in which the light beam B1 is not blocked by the discharge electrodes 11a and 11b.

[0071] (7) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b with respect to the optical axis A1 is in the following range: 1 mrad<Δθ≦7.1 mrad

[0072] This ensures that the effect of tilting the laser chamber 10 is fully achieved even when taking into account variations in the slit axis Aslit and the beam divergence angle, and also prevents part of the light beam B1 from being blocked by the discharge electrodes 11a and 11b.

[0073] (8) According to the first embodiment, the laser device 1a includes a pair of rails 18e and 18f arranged on either side of a plane perpendicular to the optical axis A1 and passing through the center of gravity of the laser chamber 10, and a plurality of wheels 18c and 18d that enable the laser chamber 10 to move along the rails 18e and 18f. The rails 18e and 18f have different lengths along the longitudinal direction of the cross section of the light beam B1.

[0074] This allows the tilt Δθ of the laser chamber 10 to be adjusted by adjusting the lengths of the rails 18e and 18f in the V direction.

[0075] (10) According to the first embodiment, the laser device 1a includes a second optical resonator including a rear mirror 24 and an output coupling mirror 25, and a laser chamber 20 in which laser gas is sealed. The laser chamber 20 includes a pair of discharge electrodes 21a and 21b that form a discharge space through which a light beam B2 traveling back and forth in the second optical resonator passes, a crossflow fan 27 that circulates the laser gas within the laser chamber 20, rectifying guides 22a and 22b that guide the laser gas within the laser chamber 20 to between the discharge electrodes 21a and 21b, and a pair of windows 20a and 20b located in the optical path of the light beam B2.

[0076] This makes it possible to suppress deterioration of the optical elements even in a configuration including a master oscillator MO and a power oscillator PO.

[0077] (11) According to the first embodiment, the rear mirror 14 is configured as a partially reflecting mirror, and the first optical resonator is configured to amplify and output the laser light output from the second optical resonator and incident via the rear mirror 14.

[0078] According to this, by tilting the laser chamber 10 of the power oscillator PO, it is possible to suppress deterioration of the optical elements of the power oscillator PO.

[0079] (13) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is greater than the inclination of the longitudinal direction of the discharge electrodes 21a and 21b relative to the optical axis A2 defined by the second optical resonator.

[0080] According to this, by reducing the inclination of the discharge electrodes 21a and 21b in the longitudinal direction relative to the optical axis A2, the laser chamber 20 can be installed in the conventional manner.

[0081] (14) According to the first embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is greater than the inclination of the optical axis A1 relative to the optical axis A2 defined by the second optical resonator.

[0082] This makes it possible to easily adjust the optical axes A1 and A2 by reducing the inclination of the optical axis A1 defined by the optical resonator of the power oscillator PO relative to the optical axis A2 defined by the optical resonator of the master oscillator MO.

[0083] In other respects, the first embodiment is similar to the comparative example.

[0084] 3. Wheels 18g and 18h ​​with different diameters 3.1 Configuration Figure 9 schematically shows the configuration of a laser device 1b according to a first modified example. In place of the wheels 18c and 18d in the first embodiment, wheels 18g and 18h ​​are used in the first modified example. Since the wheels 18g and 18h ​​have different diameters, the laser chamber 10 is disposed at an angle. The rails 18a and 18b may be the same as those in the comparative example.

[0085] 3.2 Operation (9) According to the first modification, the laser device 1b includes a plurality of wheels 18g and 18h ​​arranged on either side of a plane that is perpendicular to the optical axis A1 and passes through the center of gravity of the laser chamber 10, the wheels 18g and 18h ​​enabling the laser chamber 10 to move in a chamber movement direction that intersects with the optical axis A1. Furthermore, of the wheels 18g and 18h, the wheel 18g located on one side of the plane and the wheel 18h located on the other side have different diameters.

[0086] According to this, by using wheels 18g and 18h ​​with different diameters, the laser chamber 10 can be installed on the existing rails 18a and 18b.

[0087] In other respects, the first modified example is similar to the first embodiment.

[0088] 10 is a schematic diagram showing the configuration of a laser apparatus 1c according to a second modified example. Instead of tilting the laser chamber 10 of the power oscillator PO in the first embodiment, the laser chamber 20 of the master oscillator MO is tilted in the second modified example.

[0089] That is, in the second modified example, the power oscillator PO is the same as in the comparative example, and the master oscillator MO corresponds to the tilted laser chamber 20 in the same way as the tilted laser chamber 10 in the first embodiment. While Fig. 10 shows an example in which the laser chamber 20 is tilted by using rails 28e and 28f having different lengths along the V direction, as in the first modified example, rails 28a and 28b similar to those in the comparative example and wheels having different diameters may also be used.

[0090] The laser chamber 20 in the second modified example corresponds to the first laser chamber in this disclosure, and the windows 20a and 20b in the second modified example correspond to the first window in this disclosure. The discharge electrodes 21a and 21b in the second modified example correspond to the first discharge electrodes in this disclosure, and the rectifying guides 22a and 22b in the second modified example correspond to the first rectifying guides in this disclosure. The rear mirror 24 in the second modified example corresponds to the first rear mirror in this disclosure, the output coupling mirror 25 in the second modified example corresponds to the first output coupling mirror in this disclosure, and the optical resonator formed by the rear mirror 24 and the output coupling mirror 25 in the second modified example corresponds to the first optical resonator in this disclosure. The crossflow fan 27 in the second modified example corresponds to the first crossflow fan in this disclosure. The optical axis A2 in the second modified example corresponds to the first optical axis in this disclosure, and the light beam B2 in the second modified example corresponds to the first light beam in this disclosure.

[0091] The laser chamber 10 in the second modified example corresponds to the second laser chamber in this disclosure, and the windows 10a and 10b in the second modified example correspond to the second window in this disclosure. The discharge electrodes 11a and 11b in the second modified example correspond to the second discharge electrodes in this disclosure, and the rectifying guides 12a and 12b in the second modified example correspond to the second rectifying guides in this disclosure. The rear mirror 14 in the second modified example corresponds to the second rear mirror in this disclosure, the output coupling mirror 15 in the second modified example corresponds to the second output coupling mirror in this disclosure, and the optical resonator formed by the rear mirror 14 and the output coupling mirror 15 in the second modified example corresponds to the second optical resonator in this disclosure. The crossflow fan 17 in the second modified example corresponds to the second crossflow fan in this disclosure. The optical axis A1 in the second modified example corresponds to the second optical axis in this disclosure, and the light beam B1 in the second modified example corresponds to the second light beam in this disclosure.

[0092] 4.2 Operation (12) According to a second modification, the laser device 1c includes a first optical resonator including a rear mirror 24 and an output coupling mirror 25, and a laser chamber 20 in which laser gas is sealed. The laser chamber 20 includes a pair of discharge electrodes 21a and 21b that form a discharge space through which the light beam B2 traveling back and forth in the first optical resonator passes, a cross-flow fan 27 that circulates the laser gas in the laser chamber 20, rectifying guides 22a and 22b that guide the laser gas in the laser chamber 20 between the discharge electrodes 21a and 21b, and a pair of windows 20a and 20b located in the optical path of the light beam B2, and is inclined in the V direction, which is the longitudinal direction of the cross section of the light beam B2, with respect to the optical axis A2 defined by the first optical resonator. The laser device 1c further includes a second optical resonator including a rear mirror 14 and an output coupling mirror 15, and a laser chamber 10 in which laser gas is sealed. The laser chamber 10 includes a pair of discharge electrodes 11a and 11b that form a discharge space DS through which the light beam B1 traveling back and forth in the second optical resonator passes, a crossflow fan 17 that circulates the laser gas in the laser chamber 10, rectifying guides 12a and 12b that guide the laser gas in the laser chamber 10 between the discharge electrodes 11a and 11b, and a pair of windows 10a and 10b located in the optical path of the light beam B1. The rear mirror 14 is a partially reflecting mirror, and the second optical resonator is configured to amplify and output the laser light that is output from the first optical resonator and incident via the rear mirror 14. The laser chamber 10 does not need to be inclined with respect to the optical axis A1.

[0093] According to this, by tilting the laser chamber 20 of the master oscillator MO, not only can the bias in the light intensity distribution of the beam cross section of the laser light output from the master oscillator MO be suppressed, thereby suppressing deterioration of the optical elements of the power oscillator PO, but also deterioration of the optical elements of the master oscillator MO can be suppressed.

[0094] In other respects, the second modified example is similar to the first embodiment.

[0095] 5. Example in which both the laser chambers 10 and 20 are tilted 5.1 Configuration Figure 11 shows a schematic configuration of a laser apparatus 1d according to a third modified example. In the third modified example, both the laser chamber 10 of the power oscillator PO and the laser chamber 20 of the master oscillator MO are tilted.

[0096] That is, in the third modified example, the power oscillator PO is the same as in the first embodiment, and the master oscillator MO is the same as in the second modified example. 11 shows an example in which the laser chambers 10 and 20 are tilted by using rails 18 e, 18 f, 28 e, and 28 f, but as in the first modified example, rails 18 a and 18 b similar to those in the comparative example and wheels 18 g and 18 h having different diameters may be used, or rails 28 a and 28 b similar to those in the comparative example and wheels having different diameters may be used.

[0097] It is desirable that the laser chambers 10 and 20 are tilted in the same direction. Furthermore, it is desirable that the longitudinal directions of the discharge electrodes 11a and 11b and the discharge electrodes 21a and 21b are substantially parallel. It is desirable that both the tilt Δθ of the longitudinal direction of the discharge electrodes 11a and 11b with respect to the optical axis A1 and the tilt of the longitudinal direction of the discharge electrodes 21a and 21b with respect to the optical axis A2 are larger than the tilt of the optical axis A2 with respect to the optical axis A1 and larger than the tilt of the longitudinal direction of the discharge electrodes 21a and 21b with respect to the longitudinal directions of the discharge electrodes 11a and 11b.

[0098] 5.2 Operation (16) According to the third modification, the laser device 1d comprises a first optical resonator including a rear mirror 14 and an output coupling mirror 15, and a laser chamber 10 in which a laser gas is sealed, the laser chamber 10 being tilted in the longitudinal direction of the cross section of the light beam B1 with respect to the optical axis A1 defined by the first optical resonator. The laser device 1d further comprises a second optical resonator including a rear mirror 24 and an output coupling mirror 25, and a laser chamber 20 in which a laser gas is sealed. The laser chamber 20 includes a pair of discharge electrodes 21 a and 21 b that form a discharge space through which the light beam B2 travels back and forth in the second optical resonator, a cross-flow fan 27 that circulates the laser gas in the laser chamber 20, rectifying guides 22 a and 22 b that guide the laser gas in the laser chamber 20 to between the discharge electrodes 21 a and 21 b, and a pair of windows 20 a and 20 b located in the optical path of the light beam B2, and is inclined in the longitudinal direction of the cross section of the light beam B2 with respect to the optical axis A2 defined by the second optical resonator. The rear mirror 14 is a partially reflecting mirror, and the first optical resonator is configured to amplify and output the laser light that is output from the second optical resonator and incident via the rear mirror 14.

[0099] According to this, by tilting the laser chamber 10 of the power oscillator PO with respect to the optical axis A1 of the optical resonator and tilting the laser chamber 20 of the master oscillator MO with respect to the optical axis A2 of the optical resonator, the light intensity distribution in the beam cross section can be made smoother, and deterioration of the optical elements can be suppressed.

[0100] (17) According to the third modified example, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 and the inclination of the longitudinal direction of the discharge electrodes 21a and 21b relative to the optical axis A2 are larger than the inclination of the optical axis A2 relative to the optical axis A1, and are larger than the inclination of the longitudinal direction of the discharge electrodes 21a and 21b relative to the longitudinal direction of the discharge electrodes 11a and 11b.

[0101] According to this, by reducing the inclination of the optical axis A2 relative to the optical axis A1 and reducing the inclination of the longitudinal direction of the discharge electrodes 21a and 21b relative to the longitudinal direction of the discharge electrodes 11a and 11b, the optical axes A1 and A2 can be easily adjusted, and the installation and positioning of the laser chambers 10 and 20 can be easily performed.

[0102] In other respects, the third modified example is similar to the first embodiment.

[0103] 12 is a schematic diagram showing the configuration of a laser device 1e according to a fourth modification. The fourth modification includes a configuration similar to the master oscillator MO in the second modification, but does not necessarily include the power oscillator PO and the beam steering unit 30.

[0104] FIG. 12 shows an example in which the laser chamber 20 is tilted by using rails 28e and 28f, but as in the first modified example, rails 28a and 28b similar to those in the comparative example and wheels having different diameters may also be used.

[0105] In other respects, the fourth modified example is similar to the second modified example.

[0106] 13 is a schematic diagram showing the configuration of a laser apparatus 1f according to a second embodiment. In the laser apparatus 1f, instead of the laser chamber 10, an optical resonator composed of a rear mirror 14 and an output coupling mirror 15 is tilted with respect to the base plate 19c. As a result, the laser chamber 10 is positioned at an angle with respect to the optical axis A1 defined by the optical resonator.

[0107] The rear mirror 14 is supported at an angle with respect to the cavity plate 19b via a holder 14b instead of the holder 14a, and the output coupling mirror 15 is supported at an angle with respect to the cavity plate 19a via a holder 15b instead of the holder 15a. As a result, the cavity plates 19a and 19b are arranged at an angle with respect to the optical axis A1.

[0108] In the laser device 1f, slits 16c and 16d are arranged instead of the slits 16a and 16b. A slit axis Aslit (see FIG. 8) defined by the centers of the slits 16c and 16d is substantially parallel to the optical axis A1.

[0109] The optical axis A1 is inclined with respect to the optical axis A2. The longitudinal direction of the discharge electrodes 11a and 11b of the power oscillator PO and the longitudinal direction of the discharge electrodes 21a and 21b of the master oscillator MO may be substantially parallel. A beam steering unit (not shown) may be disposed in the optical path of the laser light output from the power oscillator PO to adjust the traveling direction of the laser light.

[0110] 13 shows an example in which the optical resonator of the power oscillator PO is tilted with respect to the base plate 19 c, but instead of tilting the optical resonator of the power oscillator PO with respect to the base plate 19 c, the optical resonator of the master oscillator MO may be tilted with respect to the base plate 29 c. This idea is similar to that of the second modified example.

[0111] Furthermore, the optical resonators of the power oscillator PO and the master oscillator MO may be tilted with respect to the base plates 19c and 29c, respectively. It is desirable that the optical resonators of the power oscillator PO and the master oscillator MO are tilted in the same direction. This concept is the same as in the third modified example.

[0112] Furthermore, the laser device 1f may include a master oscillator MO in which the optical resonator is tilted with respect to the base plate 29c, and may not include the power oscillator PO and the beam steering unit 30. This concept is similar to that of the fourth modified example.

[0113] 7.2 Operation (15) According to the second embodiment, the inclination Δθ of the longitudinal direction of the discharge electrodes 11a and 11b relative to the optical axis A1 is greater than the inclination of the longitudinal direction of the discharge electrodes 21a and 21b relative to the longitudinal direction of the discharge electrodes 11a and 11b.

[0114] According to this, by reducing the inclination of the longitudinal direction of the discharge electrodes 21a and 21b with respect to the longitudinal direction of the discharge electrodes 11a and 11b, the installation and positioning of the laser chambers 10 and 20 can be easily performed.

[0115] (18) According to the second embodiment, the laser device 1f includes a pair of cavity plates 19b and 19a that support the rear mirror 14 and the output coupling mirror 15, and the cavity plates 19b and 19a are inclined with respect to the optical axis A1.

[0116] According to this, even if the laser chamber 10 is not tilted relative to the cavity plates 19b and 19a, by tilting the optical axis A1, it is possible to suppress bias in the light intensity distribution in the beam cross section and suppress deterioration of the optical elements.

[0117] In other respects, the second embodiment is similar to the first embodiment.

[0118] 8. Example of Tilting the Cavity Plates 19e and 19f 8.1 Configuration Figure 14 schematically shows the configuration of a laser apparatus 1g according to a fifth modified example. In the fifth modified example, the cavity plates 19e and 19f are tilted with respect to the laser chamber 10, thereby tilting the optical resonator with respect to the base plate 19c. The cavity plates 19e and 19f support the output coupling mirror 15 and the rear mirror 14 via holders 15a and 14a, respectively. As a result, the laser chamber 10 is positioned at an angle with respect to the optical axis A1 defined by the optical resonator.

[0119] 8.2 Operation (19) According to the fifth modification, the laser device 1g includes a pair of cavity plates 19f and 19e that support the rear mirror 14 and the output coupling mirror 15, and the cavity plates 19f and 19e are inclined with respect to the laser chamber 10.

[0120] According to this, by tilting the cavity plates 19f and 19e that support the optical resonator, the optical axis A1 can be tilted, and the bias in the light intensity distribution in the beam cross section can be suppressed, thereby suppressing deterioration of the optical elements.

[0121] In other respects, the fifth modified example is similar to the second embodiment.

[0122] 15 is a schematic diagram showing the configuration of an exposure device 100 connected to a laser device 1a. The laser device 1a generates laser light and outputs it to the exposure device 100.

[0123] In FIG. 15 , exposure apparatus 100 includes illumination optical system 40 and projection optical system 41. Illumination optical system 40 illuminates a reticle pattern of a reticle (not shown) placed on reticle stage RT with laser light incident from laser device 1a. Projection optical system 41 reduces and projects the laser light transmitted through the reticle to form an image on a workpiece (not shown) placed on workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. Exposure apparatus 100 exposes the workpiece with laser light reflecting the reticle pattern by synchronously translating reticle stage RT and workpiece table WT. After transferring the reticle pattern to a semiconductor wafer through the exposure process described above, electronic devices can be manufactured through multiple processes.

[0124] Although FIG. 15 shows an example in which the exposure apparatus 100 is connected to the laser apparatus 1a, it may be connected to any of the laser apparatuses 1b to 1g.

[0125] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0126] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, terms such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C," and should also be construed as including combinations other than "A," "B," and "C."

Claims

1. A laser device comprising: a first optical resonator including a first rear mirror and a first output coupling mirror; a first laser chamber in which laser gas is sealed, the first laser chamber including: a pair of first discharge electrodes that form a discharge space through which a first light beam travels back and forth in the first optical resonator passes; a first cross-flow fan that circulates the laser gas in the first laser chamber; a first rectifying guide that guides the laser gas in the first laser chamber to between the first discharge electrodes; and a pair of first windows located in the optical path of the first light beam, the first laser chamber being inclined in the longitudinal direction of a cross section of the first light beam with respect to a first optical axis defined by the first optical resonator.

2. A laser device as described in claim 1, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis is greater than the inclination of the longitudinal direction of the first discharge electrode relative to the rotation axis of the first crossflow fan.

3. A laser device according to claim 1, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis is greater than the inclination of the longitudinal direction of the first discharge electrode relative to the longitudinal direction of the first straightening guide.

4. A laser device as described in claim 1, further comprising a pair of slits whose slit length along the longitudinal direction of the cross section of the first light beam is smaller than the gap length of the first discharge electrode, the first laser chamber is disposed between the first rear mirror and the first output coupling mirror, and the pair of slits are disposed between the first rear mirror and the first laser chamber, and between the first output coupling mirror and the first laser chamber.

5. A laser device according to claim 4, wherein the inclination of the longitudinal direction of said first discharge electrode relative to said first optical axis is greater than the inclination of a slit axis defined at the center of each of said slits relative to said first optical axis.

6. A laser device according to claim 4, wherein, when the length of the first discharge electrode along the longitudinal direction is L, the gap length is Vgap, and the slit length is Vslit, the inclination Δθ of the first discharge electrode in the longitudinal direction with respect to the first optical axis is in the following range: 0<Δθ≦(Vgap-Vslit) / L 7. A laser device according to claim 1, wherein the inclination Δθ of the longitudinal direction of the first discharge electrode with respect to the first optical axis is in the following range: 1 mrad<Δθ≦7.1 mrad 8. A laser device as described in claim 1, further comprising: a pair of rails arranged on either side of a plane perpendicular to the first optical axis and passing through the center of gravity of the first laser chamber; and a plurality of wheels enabling the first laser chamber to move along the rails, wherein the lengths of the rails along the longitudinal direction of the cross section of the first optical beam are different from each other.

9. A laser device as described in claim 1, further comprising a plurality of wheels arranged on either side of a plane perpendicular to the first optical axis and passing through the center of gravity of the first laser chamber, the wheels enabling the first laser chamber to move in a chamber movement direction intersecting the first optical axis, wherein the wheels on one side and the wheels on the other side of the plane have different diameters.

10. A laser device as claimed in claim 1, further comprising: a second optical resonator including a second rear mirror and a second output coupling mirror; a second laser chamber in which laser gas is sealed, the second laser chamber including: a pair of second discharge electrodes forming a discharge space through which a second light beam travelling back and forth in the second optical resonator passes; a second cross-flow fan for circulating the laser gas in the second laser chamber; a second rectifying guide for guiding the laser gas in the second laser chamber to between the second discharge electrodes; and a pair of second windows located in the optical path of the second light beam, wherein one of the first and second optical resonators is configured to amplify and output laser light output from the other of the first and second optical resonators.

11. A laser device as described in claim 10, wherein the first rear mirror is composed of a partially reflecting mirror, and the first optical resonator is configured to amplify and output the laser light output from the second optical resonator and incident via the first rear mirror.

12. A laser device as described in claim 10, wherein the second rear mirror is composed of a partial reflection mirror, and the second optical resonator is configured to amplify and output the laser light output from the first optical resonator and incident via the second rear mirror.

13. A laser device as described in claim 10, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis is greater than the inclination of the longitudinal direction of the second discharge electrode relative to a second optical axis defined by the second optical resonator.

14. A laser device according to claim 10, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis is greater than the inclination of the first optical axis relative to a second optical axis defined by the second optical resonator.

15. A laser device according to claim 10, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis is greater than the inclination of the longitudinal direction of the second discharge electrode relative to the longitudinal direction of the first discharge electrode.

16. A laser device as claimed in claim 1, further comprising: a second optical resonator including a second rear mirror and a second output coupling mirror; a second laser chamber in which laser gas is sealed, the second laser chamber including: a pair of second discharge electrodes forming a discharge space through which a second light beam travelling back and forth in the second optical resonator passes; a second cross-flow fan for circulating the laser gas in the second laser chamber; a second rectifying guide for directing the laser gas in the second laser chamber to between the second discharge electrodes; and a pair of second windows located in the optical path of the second light beam, the second laser chamber being inclined in the longitudinal direction of a cross section of the second light beam with respect to a second optical axis defined by the second optical resonator; wherein the first rear mirror is constituted by a partial reflection mirror; and the first optical resonator is configured to amplify and output laser light output from the second optical resonator and incident via the first rear mirror.

17. A laser device as described in claim 16, wherein the inclination of the longitudinal direction of the first discharge electrode relative to the first optical axis and the inclination of the longitudinal direction of the second discharge electrode relative to the second optical axis are greater than the inclination of the second optical axis relative to the first optical axis and greater than the inclination of the longitudinal direction of the second discharge electrode relative to the longitudinal direction of the first discharge electrode.

18. A laser device as claimed in claim 1, further comprising: a pair of cavity plates supporting said first rear mirror and said first output coupling mirror, said cavity plates being tilted with respect to said first optical axis.

19. A laser device as claimed in claim 1, further comprising a pair of cavity plates supporting said first rear mirror and said first output coupling mirror, said cavity plates being tilted relative to said first laser chamber.

20. A method for manufacturing an electronic device, comprising: generating laser light by a laser apparatus comprising: a first optical resonator including a first rear mirror and a first output coupling mirror; a first laser chamber in which laser gas is sealed, the first laser chamber including: a pair of first discharge electrodes that form a discharge space through which a first optical beam that travels back and forth in the first optical resonator passes; a first cross-flow fan that circulates the laser gas in the first laser chamber; a first rectifying guide that guides the laser gas in the first laser chamber to between the first discharge electrodes; and a pair of first windows located in the optical path of the first optical beam, the first laser chamber being inclined in the longitudinal direction of a cross section of the first optical beam with respect to a first optical axis defined by the first optical resonator; outputting the laser light to an exposure apparatus; and exposing the laser light onto a photosensitive substrate in the exposure apparatus to manufacture the electronic device.

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