Laser device and method for manufacturing electronic devices

Abstract

A laser apparatus according to an aspect of the present disclosure comprises: an oscillator that emits laser light (Lp); an amplifier (30a) that amplifies the laser light (Lp) within a chamber (32) including a pair of discharge electrodes (33a); a front-side optical system (35) and a rear-side optical system (36) that are disposed at positions facing each other across the chamber (32), and constitute a ring resonator including a first light path (P1) and a second light path (P2) that cross between the pair of discharge electrodes (33a); and a first plane-parallel substrate (61, 62) disposed on the first light path (P1) or the second light path (P2). The first light path (P1) is a light path through which the front-side optical system (35) emits the laser light (Lp) incident from the oscillator toward the rear-side optical system (36). The second light path (P2) is a light path through which the rear-side optical system (36) emits the laser light (Lp) incident via the first light path (P1) toward the front-side optical system (35). The first plane-parallel substrate (61, 62) translates the first light path (P1) and the second light path (P2) in directiond in which the first and second light paths approach each other on the chamber (32) side.

Description

Technical Field

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

Background Art

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

[0003] The spectral linewidth of spontaneous emission light of a KrF excimer laser device and an ArF excimer laser device is as wide as 350 to 400 pm. Therefore, when a projection lens is configured with a material that transmits ultraviolet rays 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. Therefore, in the laser resonator of the gas laser device, a line narrowing module (Line Narrowing Module: L NM) including a line narrowing element (such as an etalon or a grating) may be provided to narrow the spectral linewidth. Hereinafter, a gas laser device in which the spectral linewidth is narrowed is referred to as a line-narrowed gas laser device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] A laser device according to one aspect of the present disclosure comprises an oscillator that emits laser light, an amplifier that amplifies the laser light in a chamber including a pair of discharge electrodes, a front optical system and a rear optical system that constitute a ring resonator, arranged opposite each other across the chamber and including a first optical path and a second optical path that intersect between the pair of discharge electrodes, and a first parallel planar substrate arranged on the first optical path or the second optical path, wherein the first optical path is an optical path through which the front optical system emits laser light incident from the oscillator toward the rear optical system, and the second optical path is an optical path through which the rear optical system emits laser light incident via the first optical path toward the front optical system, and the first parallel planar substrate moves the first optical path and the second optical path toward each other on the chamber side.

[0006] A method for manufacturing an electronic device according to one aspect of the present disclosure is a method for manufacturing an electronic device comprising: an oscillator that emits laser light; an amplifier that amplifies the laser light in a chamber including a pair of discharge electrodes; a front optical system and a rear optical system that constitute a ring resonator, arranged opposite each other across the chamber and including a first optical path and a second optical path that intersect between the pair of discharge electrodes; and a first parallel planar substrate arranged on the first optical path or the second optical path, wherein the first optical path is an optical path through which the front optical system emits laser light incident from the oscillator toward the rear optical system, and the second optical path is an optical path through which the rear optical system emits laser light incident via the first optical path toward the front optical system, and the first parallel planar substrate is exposed to laser light in an exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0007] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 is a schematic front view showing the configuration of a laser device according to a comparative example. [Figure 2]Figure 2 is a schematic top view showing an example configuration of a power oscillator related to a comparative example. [Figure 3] Figure 3 is a schematic top view showing an example of the configuration of a power oscillator according to the first embodiment. [Figure 4] Figure 4 is a schematic perspective view showing the configuration of the first parallel planar substrate and the second parallel planar substrate. [Figure 5] Figure 5 illustrates the operation of the first parallel planar substrate and the second parallel planar substrate. [Figure 6] Figure 6 is a schematic top view showing an example of the configuration of a power oscillator according to a modification of the first embodiment. [Figure 7] Figure 7 is a schematic top view showing an example of the configuration of a power oscillator according to the second embodiment. [Figure 8] Figure 8 is a schematic top view showing an example of the configuration of a power oscillator according to the third embodiment. [Figure 9] Figure 9 is a schematic top view showing an example of the configuration of a power oscillator according to the fourth embodiment. [Figure 10] Figure 10 shows the structure of the CaF2 crystal forming the first parallel planar substrate. [Figure 11] Figure 11 shows a preferred first crystal orientation in relation to the laser light incident on the first parallel planar substrate. [Figure 12] Figure 12 shows a preferred second crystal orientation in relation to the laser light incident on the first parallel planar substrate. [Figure 13] Figure 13 shows a preferred third crystal orientation in relation to the laser light incident on the first parallel planar substrate. [Figure 14] Figure 14 is a schematic front view showing an example of the configuration of a modified laser device. [Figure 15] Figure 15 is a schematic diagram showing an example of the configuration of an exposure apparatus. Embodiment

[0008] <Contents> 1. Comparative Example 1.1 Configuration 1.2 Operations 1.3 Problems 2. First Embodiment 2.1 Configuration 2.2 Operations 2.3 Effects 2.4 Variations 3. Second Embodiment 3.1 Configuration 3.2 Operations 3.3 Effects 4. Third Embodiment 4.1 Configuration 4.2 Operations 4.3 Effects 4.4 Variations 5. Fourth Embodiment 5.1 Configuration 5.2 Operations 5.3 Effects 5.4 Variations 6. Crystal Orientation of Parallel Plane Substrate 6.1 Crystal Structure 6.2 First Crystal Orientation 6.3 Second Crystal Orientation 6.4 Third Crystal Orientation 7. Variations of Master Oscillator 7.1 Configuration 7.2 Operations 7.3 Others 8. Manufacturing Method of Electronic Device

[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. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0010] 1. Comparative Example 1.1 Configuration Figure 1 schematically shows an example configuration of the laser apparatus 2 according to the comparative example. Figure 2 schematically shows an example configuration of the power oscillator 30 according to the comparative example. The comparative examples in this disclosure are forms that the applicant recognizes as being known only to the applicant, and are not prior art that the applicant acknowledges.

[0011] In Figure 1, the height direction of the laser device 2 is the V-axis direction, the length direction is the Z-axis direction, and the depth direction is the H-axis direction. The V-axis direction may be parallel to the direction of gravity, and the direction opposite to the direction of gravity is defined as the "+V-axis direction". The direction of emission of the laser beam Lp emitted from the laser device 2 is defined as the "+Z-axis direction". The direction toward the foreground of the paper in Figure 1 is defined as the "+H-axis direction".

[0012] Laser device 2 consists of a master oscillator (MO) 10 and an MO beam. The system includes a master steering unit 20 and a power oscillator (PO) 30. The master oscillator 10 is an example of an "oscillator" according to the technology of this disclosure. The power oscillator 30 is an example of an "amplifier" according to the technology of this disclosure.

[0013] The master oscillator 10 includes a narrowband module (LNM) 11, a chamber 14, and an output coupler (OC) 17.

[0014] The LNM11 includes a prism beam expander 12 and a grating 13 for narrowing the spectral linewidth. The prism beam expander 12 and the grating 13 are arranged in a Littrow configuration such that the angle of incidence and the angle of diffraction coincide.

[0015] The output coupling mirror 17 is a reflective mirror with a reflectivity in the range of 40% to 60%. The output coupling mirror 17 and the LNM 11 constitute an optical resonator.

[0016] Chamber 14 is positioned on the optical path of the optical resonator. Chamber 14 includes a pair of discharge electrodes 15a, 15b and two windows 16a, 16b through which the laser light Lp passes. Chamber 14 is filled with laser gas. The laser gas may include, for example, Ar gas or Kr gas as a rare gas, F2 gas as a halogen gas, and Ne gas as a buffer gas.

[0017] Windows 16a and 16b are positioned such that the incident angle of the laser beam Lp is close to the Brewster angle. Furthermore, windows 16a and 16b are positioned such that the polarization state of the laser beam Lp is P-polarized.

[0018] The MO beam steering unit 20 includes a high-reflection mirror 21a and a high-reflection mirror 21b. The high-reflection mirrors 21a and 21b are positioned so that the laser beam Lp emitted from the master oscillator 10 is incident on the power oscillator 30. The laser beam Lp emitted from the master oscillator 10 is pulsed laser light.

[0019] The high-reflectivity mirror in this disclosure is a planar mirror in which a high-reflectivity film is formed on the surface of a substrate made of, for example, synthetic quartz or calcium fluoride (CaF2). The high-reflectivity film is a dielectric multilayer film, for example, a film containing fluoride.

[0020] The power oscillator 30 includes a chamber 32, a front optical system 35, and a rear optical system 36. The front optical system 35 and the rear optical system 36 constitute a ring resonator. The front optical system 35 is located on the light incidence side where laser light Lp is incident on the power oscillator 30 from the MO beam steering unit 20. The rear optical system 36 is located opposite the front optical system 35, with the chamber 32 in between.

[0021] Chamber 32 is positioned on the optical path of the ring resonator. Chamber 32 has a similar configuration to chamber 14 of the master oscillator 10. That is, chamber 32 includes a pair of discharge electrodes 33a, 33b and two windows 34a, 34b through which the laser light Lp passes. Chamber 32 is filled with laser gas.

[0022] Windows 34a and 34b are positioned such that the incident angle of the laser beam Lp is close to the Brewster angle. Furthermore, windows 34a and 34b are positioned such that the polarization state of the laser beam Lp is P-polarized.

[0023] In Figure 2, the front optical system 35 includes an output coupling mirror 40 and a high-reflection mirror 41. The output coupling mirror 40 is positioned on the optical path of the laser beam Lp incident from the MO beam steering unit 20 so that the laser beam Lp is incident at a predetermined incident angle.

[0024] The output coupling mirror 40 is, for example, a partially reflective mirror with a reflectivity in the range of 10% to 30%. The output coupling mirror 40 has opposing first surfaces 40a and second surfaces 40b. The first surface 40a and the second surface 40b are parallel to the V-axis direction, which is the discharge direction of the pair of discharge electrodes 33a and 33b. An anti-reflective coating is formed on the first surface 40a. A partially reflective coating is formed on the second surface 40b.

[0025] The output coupling mirror 40 transmits the laser light Lp incident on the first surface 40a from the MO beam steering unit 20. The output coupling mirror 40 also transmits a portion of the laser light Lp incident on the second surface 40b from the high-reflection mirror 41, and reflects a portion of it. A portion of the laser light Lp that has passed through the output coupling mirror 40 is emitted from the front optical system 35 and incident on the high-reflection mirror 42, which will be described later. A portion of the laser light Lp reflected by the second surface 40b of the output coupling mirror 40 is incident on the chamber 32.

[0026] The high-reflection mirror 41 has a high-reflection surface 41a on which a high-reflection film is formed. The output coupling mirror 40 and the high-reflection mirror 41 are arranged such that the second surface 40b and the high-reflection surface 41a face each other at a predetermined angle. The high-reflection mirror 41 reflects the laser light Lp incident from the rear optical system 36 through the chamber 32 toward the second surface 40b of the output coupling mirror 40 with its high-reflection surface 41a.

[0027] Although not shown in Figure 1, a high-reflection mirror 42 is positioned on the light-emitting side of the front optical system 35, as shown in Figure 2. The high-reflection mirror 42 reflects the laser light Lp emitted from the front optical system 35 and propagates it in the Z-axis direction.

[0028] The rear optical system 36 includes a first high-reflection mirror 50 and a second high-reflection mirror 51. The first high-reflection mirror 50 has a high-reflection surface 50a on which a high-reflection film is formed. The second high-reflection mirror 51 has a high-reflection surface 51a on which a high-reflection film is formed. The high-reflection surfaces 50a and 51a are parallel to the V-axis direction. The first high-reflection mirror 50 and the second high-reflection mirror 51 are arranged such that their high-reflection surfaces 50a and 51a face each other at a predetermined angle.

[0029] The first high-reflection mirror 50 reflects the laser light Lp incident from the front optical system 35 through the chamber 32 toward the second high-reflection mirror 51 with its high-reflection surface 50a. The second high-reflection mirror 51 reflects the laser light Lp incident from the first high-reflection mirror 50 toward the chamber 32 with its high-reflection surface 51a.

[0030] The front optical system 35 and the rear optical system 36 form a ring resonator that includes a first optical path P1 and a second optical path P2 that intersect between a pair of discharge electrodes 33a and 33b. The first optical path P1 and the second optical path P2 are in close proximity within the discharge space between the pair of discharge electrodes 33a and 33b.

[0031] The first optical path P1 is composed of an output coupling mirror 40 and a first high-reflection mirror 50. The second optical path P2 is composed of a second high-reflection mirror 51 and a high-reflection mirror 41. The first optical path P1 is the optical path through which the front optical system 35 emits laser light Lp incident from the master oscillator 10 toward the rear optical system 36. The second optical path P2 is the optical path through which the rear optical system 36 emits laser light Lp incident via the first optical path P1 toward the front optical system 35.

[0032] In other words, the first optical path P1 is the forward path from the front optical system 35 through the chamber 32 to the rear optical system 36. The second optical path P2 is the return path from the rear optical system 36 through the chamber 32 to the front optical system 35. Furthermore, the first optical path P1 and the second optical path P2 are contained in a plane perpendicular to the V-axis direction, which is the discharge direction by the pair of discharge electrodes 33a and 33b.

[0033] 1.2 Operation When a discharge occurs in the chamber 14 of the master oscillator 10, the laser gas is excited, and the laser light Lp, narrowed by the optical resonator composed of the output coupling mirror 17 and the LNM 11, is emitted from the output coupling mirror 17. This laser light Lp is then incident as seed light into the front optical system 35 of the power oscillator 30 by the MO beam steering unit 20.

[0034] The laser beam Lp incident on the front optical system 35 passes through the output coupling mirror 40 and enters the inside of the ring resonator. The laser beam Lp that has passed through the output coupling mirror 40 travels along the first optical path P1 and is incident on the chamber 32. A discharge occurs in the discharge space in synchronization with the timing of the laser beam Lp being incident on the chamber 32. As a result, the laser gas is excited and the laser beam Lp is amplified. The amplified laser beam Lp is emitted from the chamber 32, travels along the first optical path P1, and then is incident on the rear optical system 36.

[0035] The laser beam Lp incident on the rear optical system 36 is reflected by the first high-reflection mirror 50 and the second high-reflection mirror 51, causing its direction of travel to be reversed and it is emitted from the rear optical system 36. The laser beam Lp emitted from the rear optical system 36 travels along the second optical path P2 and is incident on the chamber 32. The laser beam Lp incident on the chamber 32 is amplified again in the discharge space and is emitted from the chamber 32. The laser beam Lp emitted from the chamber 32 travels along the second optical path P2 and then is incident on the front optical system 35.

[0036] The laser beam Lp incident on the front optical system 35 is reflected by the high-reflection mirror 41 toward the output coupling mirror 40. A portion of the laser beam Lp incident on the output coupling mirror 40 passes through the output coupling mirror 40 and is emitted from the front optical system 35 toward the high-reflection mirror 42, where it is reflected and emitted from the laser device 2.

[0037] Furthermore, a portion of the remaining laser beam Lp incident on the output coupling mirror 40 is reflected by the output coupling mirror 40 and emitted from the front optical system 35 toward the chamber 32. In other words, the remaining portion of the laser beam Lp has its direction of travel reversed in the front optical system 35. The reversed laser beam Lp then travels again along the first optical path P1 and is incident on the chamber 32. In this way, a portion of the laser beam Lp repeatedly circulates through the ring resonator including the first optical path P1 and the second optical path P2. The laser beam Lp passes through the discharge space multiple times within a single discharge time, resulting in amplified oscillation.

[0038] 1.3 Challenges In the power oscillator 30 of the laser device 2 in the comparative example, in order to fold back the direction of propagation of the laser beam Lp in the front optical system 35 and the rear optical system 36, the first optical path P1 and the second optical path P2 must have a certain minimum distance D between them at both ends. This is because if the distance D is small, it becomes difficult to design the front optical system 35 and the rear optical system 36. Hereinafter, the distance D at both ends of the first optical path P1 and the second optical path P2 will be referred to as the optical path end distance D.

[0039] To efficiently amplify the laser beam Lp in the discharge space, it is necessary to bring the first optical path P1 and the second optical path P2 close together in the discharge space, by making them intersect at a small angle. Therefore, in order to obtain the optical path end spacing D necessary to reverse the direction of propagation of the laser beam Lp, the resonator length L of the power oscillator 30 must be set to a certain length or longer. Here, the resonator length L refers to the distance in the Z-axis direction of the ring resonator.

[0040] However, increasing the resonator length L increases the time it takes for the laser beam Lp to orbit the ring resonator, thus reducing the number of times the laser beam Lp passes through the discharge space within a single discharge cycle. As a result, the amplification efficiency decreases.

[0041] To improve amplification efficiency, it is necessary to bring the first optical path P1 and the second optical path P2 close together in the discharge space while shortening the resonator length L.

[0042] 2. First Embodiment 2.1 Configuration Figure 3 schematically shows an example of the configuration of the power oscillator 30a included in the laser apparatus according to the first embodiment of this disclosure. Figure 4 shows the configuration of the first parallel planar substrate 61 and the second parallel planar substrate 62. Figure 5 explains the operation of the first parallel planar substrate 61 and the second parallel planar substrate 62. The laser apparatus according to the first embodiment differs from the laser apparatus 2 according to the comparative example only in the configuration of the power oscillator 30a.

[0043] In Figure 3, the power oscillator 30a includes a chamber 32, a front optical system 35, a rear optical system 36, a first parallel planar substrate 61, and a second parallel planar substrate 62. The power oscillator 30a differs from the power oscillator 30 in the comparative example in that it includes the first parallel planar substrate 61 and the second parallel planar substrate 62. The configuration of the chamber 32, the front optical system 35, and the rear optical system 36 included in the power oscillator 30a is the same as in the comparative example.

[0044] The first parallel planar substrate 61 and the second parallel planar substrate 62 are parallel planar substrates that are transparent to laser light Lp. The first parallel planar substrate 61 and the second parallel planar substrate 62 are formed from, for example, calcium fluoride (CaF2).

[0045] In this embodiment, the first parallel planar substrate 61 and the second parallel planar substrate 62 are arranged between the chamber 32 and the front-side optical system 35. Specifically, the first parallel planar substrate 61 is arranged on the first optical path P1 on the front side of the chamber 32. The second parallel planar substrate 62 is arranged on the second optical path P2 on the front side of the chamber 32. The first optical path P1 on the front side of the chamber 32 refers to the first optical path P1 between the chamber 32 and the front-side optical system 35. The second optical path P2 on the front side of the chamber 32 refers to the second optical path P2 between the chamber 32 and the front-side optical system 35.

[0046] In Figure 4, the first parallel planar substrate 61 includes a first surface 61a and a second surface 61b, and a third surface 61c, which are opposite to each other. The first surface 61a and the second surface 61b are planes that are parallel to each other and are parallel to the V-axis direction. The third surface 61c is an inclined surface that is inclined with respect to the first surface 61a and the second surface 61b, and is a plane that is parallel to the V-axis direction and the Z-axis direction. The side shape of the first parallel planar substrate 61, when viewed from the V-axis direction, is trapezoidal.

[0047] The second parallel planar substrate 62 includes a first surface 62a and a second surface 62b, and a third surface 62c, which are opposite to each other. The first surface 62a and the second surface 62b are planes that are parallel to each other and are parallel to the V-axis direction. The third surface 62c is an inclined surface that is inclined with respect to the first surface 62a and the second surface 62b, and is a plane that is parallel to the V-axis direction and the Z-axis direction. The second parallel planar substrate 62 has a trapezoidal side shape when viewed from the V-axis direction.

[0048] The first parallel planar substrate 61 and the second parallel planar substrate 62 are, for example, parallel planar substrates of the same shape and size. The first parallel planar substrate 61 and the second parallel planar substrate 62 are arranged such that the third surfaces 61c and 62c are separated, and the second surfaces 61b and 62b face each other at a predetermined angle. By configuring the first parallel planar substrate 61 and the second parallel planar substrate 62 in this way, it becomes possible to arrange the parallel planar substrates in the first optical path P1 and the second optical path P2 in the narrow space inside the ring resonator, thereby saving space.

[0049] As shown in Figure 5, the first parallel-plane substrate 61 is positioned such that the normal to the first surface 61a intersects the first optical path P1 at an angle θ1. For example, angle θ1 is the Brewster angle. That is, the angle of incidence of the laser light Lp incident on the first parallel-plane substrate 61 is the Brewster angle. The first parallel-plane substrate 61 shifts the first optical path P1 by a distance δ1. Specifically, the first parallel-plane substrate 61 shifts the first optical path P1 by a distance δ1 in the direction toward the second optical path P2 on the chamber 32 side. The distance δ1 is a value determined by the angle θ1 and the refractive index and thickness of the first parallel-plane substrate 61.

[0050] The second parallel-plane substrate 62 is positioned such that the normal to the first surface 62a intersects the second optical path P2 at an angle θ2. For example, angle θ2 is the Brewster angle. That is, the angle of incidence of the laser light Lp incident on the second parallel-plane substrate 62 is the Brewster angle. The second parallel-plane substrate 62 shifts the second optical path P2 by a distance δ2. Specifically, the second parallel-plane substrate 62 shifts the second optical path P2 by a distance δ2 in the direction toward the first optical path P1 on the chamber 32 side. The distance δ2 is a value determined according to the angle θ2 and the refractive index and thickness of the second parallel-plane substrate 62. In this embodiment, δ1 = δ2.

[0051] In other words, the first parallel planar substrate 61 and the second parallel planar substrate 62 move the first optical path P1 and the second optical path P2 toward each other on the chamber 32 side, on the front side of the chamber 32.

[0052] 2.2 Operation The operation of the laser apparatus according to the first embodiment is the same as that of the laser apparatus 2 according to the comparative example, except that in the power oscillator 30a, the laser beam Lp circulating around the ring resonator is shifted by the first parallel planar substrate 61 and the second parallel planar substrate 62.

[0053] In this embodiment, the laser beam Lp emitted from the front optical system 35 and traveling along the first optical path P1 is shifted by passing through the first parallel planar substrate 61 and enters the chamber 32. Similarly, the laser beam Lp emitted from the chamber 32 and traveling along the second optical path P2 is shifted by passing through the second parallel planar substrate 62 and enters the front optical system 35.

[0054] 2.3 Effects In Figure 5, the position of the front optical system 35 in the comparative example is shown by a dashed line, and the position of the front optical system 35 in this embodiment is shown by a solid line. In this embodiment, the first parallel planar substrate 61 and the second parallel planar substrate 62 cause the first optical path P1 and the second optical path P2 to move in parallel toward each other on the chamber 32 side, so that the position where the optical path end spacing D necessary to reverse the direction of propagation of the laser beam Lp is obtained can be brought closer to the chamber 32 side.

[0055] Therefore, in this embodiment, the front optical system 35 can be brought closer to the chamber 32 than in the comparative example. As a result, the resonator length L can be shortened while bringing the first optical path P1 and the second optical path P2 closer together in the discharge space. The distance ΔL by which the resonator length L can be shortened depends on the above-mentioned distances δ1 and δ2 and the angle at which the first optical path P1 and the second optical path P2 intersect.

[0056] By shortening the resonator length L, the time it takes for the laser beam Lp to orbit the ring resonator is reduced, increasing the number of times the laser beam Lp passes through the discharge space within a single discharge cycle. As a result, the amplification efficiency is improved.

[0057] 2.4 Variations Next, a modified example of the power oscillator 30a according to the first embodiment will be described. Figure 6 schematically shows an example of the configuration of the power oscillator 30b according to the modified example. In the first embodiment, the first parallel planar substrate 61 and the second parallel planar substrate 62 are arranged on the front side of the chamber 32, but in this modified example, they are arranged on the rear side of the chamber 32. The power oscillator 30b has the same configuration as the power oscillator 30a according to the first embodiment, except that the arrangement of the first parallel planar substrate 61 and the second parallel planar substrate 62 is different.

[0058] The first parallel planar substrate 61 and the second parallel planar substrate 62 shown in Figure 6 are rotationally symmetrical with respect to a central axis parallel to the V-axis direction, with respect to the first parallel planar substrate 61 and the second parallel planar substrate 62 shown in Figure 5, with respect to a central axis parallel to the V-axis direction.

[0059] In this modified example, the first parallel planar substrate 61 and the second parallel planar substrate 62 are arranged between the chamber 32 and the rear optical system 36. Specifically, the first parallel planar substrate 61 is located on the first optical path P1 on the rear side of the chamber 32. The second parallel planar substrate 62 is located on the second optical path P2 on the rear side of the chamber 32. The angle of incidence of the laser beam Lp incident on the first parallel planar substrate 61 is the Brewster angle. The angle of incidence of the laser beam Lp incident on the second parallel planar substrate 62 is the Brewster angle.

[0060] The first parallel planar substrate 61 moves the first optical path P1 in a direction that brings it closer to the second optical path P2 on the chamber 32 side. The second parallel planar substrate 62 moves the second optical path P2 in a direction that brings it closer to the first optical path P1 on the chamber 32 side. In other words, the first parallel planar substrate 61 and the second parallel planar substrate 62 move the first optical path P1 and the second optical path P2 in a direction that brings them closer to the chamber 32 side on the rear side of the chamber 32.

[0061] According to this modified example, the rear optical system 36 can be brought closer to the chamber 32 than in the comparative example. Therefore, the same effect as in the first embodiment, which allows the front optical system 35 to be brought closer to the chamber 32, can be obtained.

[0062] 3. Second Embodiment 3.1 Configuration Next, a laser apparatus according to the second embodiment of this disclosure will be described. Note that the differences from the configuration of the laser apparatus according to the first embodiment will be explained below.

[0063] The laser apparatus according to the second embodiment differs from the laser apparatus according to the first embodiment only in the configuration of the power oscillator. Figure 7 schematically shows an example of the configuration of the power oscillator 30c according to the second embodiment. The power oscillator 30c differs from the power oscillator 30a according to the first embodiment in that, in addition to the front optical system 35, the rear optical system 36, the first parallel planar substrate 61, and the second parallel planar substrate 62, it also includes a third parallel planar substrate 63 and a fourth parallel planar substrate 64.

[0064] The first parallel planar substrate 61 and the second parallel planar substrate 62 are located on the front side of the chamber 32, similar to the first embodiment. The third parallel planar substrate 63 and the fourth parallel planar substrate 64 are located on the rear side of the chamber 32. The third parallel planar substrate 63 and the fourth parallel planar substrate 64 have the same configuration as the first parallel planar substrate 61 and the second parallel planar substrate 62 (see Figure 6) according to a modified example of the first embodiment.

[0065] The third parallel planar substrate 63 is located on the first optical path P1 at the rear of the chamber 32. The fourth parallel planar substrate 64 is located on the second optical path P2 at the rear of the chamber 32. The angle of incidence of the laser beam Lp incident on the third parallel planar substrate 63 is the Brewster angle. The angle of incidence of the laser beam Lp incident on the fourth parallel planar substrate 64 is the Brewster angle.

[0066] The third parallel planar substrate 63 moves the first optical path P1 in a direction that brings it closer to the second optical path P2 on the chamber 32 side. The fourth parallel planar substrate 64 moves the second optical path P2 in a direction that brings it closer to the first optical path P1 on the chamber 32 side. In other words, the third parallel planar substrate 63 and the fourth parallel planar substrate 64 move the first optical path P1 and the second optical path P2 in a direction that brings them closer to the chamber 32 side on the rear side of the chamber 32.

[0067] 3.2 Operation The operation of the laser apparatus according to the second embodiment is the same as that of the laser apparatus according to the first embodiment, except that the laser beam Lp orbiting the ring resonator is shifted by the third parallel planar substrate 63 and the fourth parallel planar substrate 64, in addition to the first parallel planar substrate 61 and the second parallel planar substrate 62.

[0068] In this embodiment, the laser beam Lp emitted from the front optical system 35 and traveling along the first optical path P1 is shifted by passing through the first parallel planar substrate 61 and enters the chamber 32. The laser beam Lp emitted from the chamber 32 and traveling along the first optical path P1 is shifted by passing through the third parallel planar substrate 63 and enters the rear optical system 36.

[0069] The laser beam Lp emitted from the rear optical system 36 and traveling along the second optical path P2 is shifted by passing through the fourth parallel planar substrate 64 and enters the chamber 32. The laser beam Lp emitted from the chamber 32 and traveling along the second optical path P2 is shifted by passing through the second parallel planar substrate 62 and enters the front optical system 35.

[0070] 3.3 Effects In this embodiment, the front optical system 35 and the rear optical system 36 can be brought closer to the chamber 32. As a result, the resonator length L can be made even shorter than in the first embodiment, and the amplification efficiency is further improved.

[0071] 4. Third Embodiment 4.1 Configuration Next, a laser apparatus according to the third embodiment of this disclosure will be described. Note that the differences from the configuration of the laser apparatus according to the first embodiment will be explained below.

[0072] The laser apparatus according to the third embodiment differs from the laser apparatus according to the first embodiment only in the configuration of the power oscillator. Figure 8 schematically shows an example of the configuration of the power oscillator 30d according to the third embodiment. The power oscillator 30d includes a front optical system 35, a rear optical system 36, and two first parallel planar substrates 61. The power oscillator 30d differs from the power oscillator 30a according to the first embodiment in that it includes two first parallel planar substrates 61 instead of the first parallel planar substrate 61 and the second parallel planar substrate 62.

[0073] The two first parallel planar substrates 61 are arranged on the first optical path P1. Specifically, one of the two first parallel planar substrates 61 is arranged on the first optical path P1 on the front side of the chamber 32, and the other is arranged on the first optical path P1 on the rear side of the chamber 32. The incident angle of the laser beam Lp incident on each of the first parallel planar substrates 61 is the Brewster angle.

[0074] The first parallel planar substrate 61 positioned on the first optical path P1 on the front side of the chamber 32 has the same configuration as the first parallel planar substrate 61 according to the first embodiment. The first parallel planar substrate 61 positioned on the first optical path P1 on the rear side of the chamber 32 has the same configuration as the first parallel planar substrate 61 according to a modified example of the first embodiment (see Figure 6).

[0075] Each of the first parallel planar substrates 61 moves the first optical path P1 in a parallel direction toward the second optical path P2 on the chamber 32 side. That is, the two first parallel planar substrates 61 move the first optical path P1 and the second optical path P2 toward the chamber 32 side on the front and rear sides of the chamber 32.

[0076] 4.2 Operation The operation of the laser apparatus according to the third embodiment is the same as that of the laser apparatus according to the first embodiment, except that the laser beam Lp orbiting the ring resonator is shifted by two first parallel planar substrates 61 instead of the first parallel planar substrate 61 and the second parallel planar substrate 62.

[0077] In this embodiment, the laser beam Lp emitted from the front optical system 35 and traveling along the first optical path P1 is shifted by passing through the first parallel planar substrate 61 and enters the chamber 32. The laser beam Lp emitted from the chamber 32 and traveling along the first optical path P1 is shifted by passing through the first parallel planar substrate 61 and enters the rear optical system 36.

[0078] In this embodiment, the laser beam Lp traveling through the second optical path P2 is not shifted. The laser beam Lp emitted from the rear optical system 36 and traveling through the second optical path P2 is incident on the front optical system 35 via the chamber 32.

[0079] 4.3 Effects In this embodiment, the two first parallel planar substrates 61 make it possible to bring the front optical system 35 and the rear optical system 36 closer to the chamber 32. If the refractive index and thickness of each of the first parallel planar substrates 61 are the same as those of the first parallel planar substrate 61 and the second parallel planar substrate 62 in the first embodiment, the resonator length L can be the same as in the first embodiment. Therefore, the same effects as in the first embodiment can be obtained.

[0080] 4.4 Variations Next, a modified example of the power oscillator 30d according to the third embodiment will be described. In the third embodiment, the first parallel planar substrate 61 is arranged in each of the first optical paths P1 on the front and rear sides of the chamber 32. Alternatively, the first parallel planar substrate 61 may be arranged only on the first optical path P1 on either the front or rear side of the chamber 32.

[0081] Furthermore, in the third embodiment, two first parallel planar substrates 61 are arranged on the first optical path P1, but instead, two second parallel planar substrates 62 may be arranged on the second optical path P2. Specifically, one of the two second parallel planar substrates 62 may be arranged on the second optical path P2 on the front side of the chamber 32, and the other may be arranged on the second optical path P2 on the rear side of the chamber 32. Moreover, the second parallel planar substrates 62 may be arranged on only one of the second optical paths P2 on either the front or rear side of the chamber 32.

[0082] In other words, the power oscillator of the laser device according to the technology of this disclosure may be any device in which at least one parallel planar substrate is arranged on the first optical path P1 or the second optical path P2.

[0083] 5. Fourth Embodiment 5.1 Configuration Next, a laser apparatus according to the fourth embodiment of this disclosure will be described. Note that the differences from the configuration of the laser apparatus according to the first embodiment will be explained below.

[0084] The laser apparatus according to the fourth embodiment differs from the laser apparatus according to the first embodiment only in the configuration of the power oscillator. Figure 9 schematically shows an example of the configuration of the power oscillator 30e according to the fourth embodiment. The configuration of the front optical system 35a of the power oscillator 30e differs from the configuration of the front optical system 35 according to the first embodiment. The other configurations of the power oscillator 30e are the same as those of the power oscillator 30a according to the first embodiment.

[0085] The front optical system 35a includes an output coupling mirror 40, a first high-reflection mirror 43, and a second high-reflection mirror 44. The configuration of the output coupling mirror 40 is the same as in the first embodiment. The first high-reflection mirror 43 is positioned to reflect the laser light Lp that travels along the second optical path P2 and enters the front optical system 35a toward the second high-reflection mirror 44. The second high-reflection mirror 44 is positioned to reflect the laser light Lp that enters from the first high-reflection mirror 43 toward the second surface 40b of the output coupling mirror 40.

[0086] The output coupling mirror 40 transmits a portion of the laser light Lp incident on the second surface 40b from the second high-reflection mirror 44, and reflects a portion of it, allowing it to propagate along the first optical path P1.

[0087] In the first embodiment, the ring resonator is composed of four mirrors: an output coupling mirror 40, a high-reflection mirror 41, a first high-reflection mirror 50, and a second high-reflection mirror 51. In contrast, in this embodiment, the ring resonator is composed of five mirrors: an output coupling mirror 40, a first high-reflection mirror 43, a second high-reflection mirror 44, a first high-reflection mirror 50, and a second high-reflection mirror 51.

[0088] 5.2 Operation The operation of the laser device according to the fourth embodiment is the same as that of the laser device according to the first embodiment, except that the laser light Lp incident on the front optical system 35a is reflected by the first high-reflection mirror 43 and the second high-reflection mirror 44 before being incident on the output coupling mirror 40.

[0089] In this embodiment, the laser light Lp incident from the chamber 32 through the second parallel planar substrate 62 to the front-side optical system 35a is reflected by the first high-reflection mirror 43 and the second high-reflection mirror 44 and incident on the output coupling mirror 40. A portion of the laser light Lp incident on the output coupling mirror 40 passes through the output coupling mirror 40 and is emitted from the front-side optical system 35a toward the high-reflection mirror 42, where it is reflected by the high-reflection mirror 42 and emitted from the laser device. The remaining portion of the laser light Lp incident on the output coupling mirror 40 is reflected by the output coupling mirror 40 and emitted from the front-side optical system 35a.

[0090] 5.3 Effects In this embodiment, since the ring resonator is composed of five mirrors, the beam profile of the laser light Lp is mirror-reversed each time it completes one rotation around the ring resonator. That is, the beam profile of the laser light Lp emitted from the power oscillator 30e is mirror-reversed each time it completes one rotation, which reduces the spatial coherence of the laser light Lp. As a result, when the laser device is used as a light source for exposure, speckle on the reticle is suppressed.

[0091] Furthermore, even if there is an angular misalignment in the five mirrors that make up the ring resonator, the beam profile of the laser light Lp is mirror-reversed with each rotation, which has the advantage of suppressing the accumulation of the angular misalignment components of each mirror.

[0092] 5.4 Variations The front-side optical system 35a according to this embodiment is not limited to the front-side optical system 35 according to the first embodiment, but can also be used in place of the front-side optical system 35 according to the second embodiment, the third embodiment, or a modified version thereof.

[0093] 6. Crystal orientation of parallel-planar substrates Next, variations in the crystal orientation of the parallel planar substrate will be described. Below, several preferred crystal orientations in relation to the laser light Lp incident on the first parallel planar substrate 61 will be described. The same applies to parallel planar substrates other than the first parallel planar substrate 61.

[0094] 6.1 Crystal structure Figure 10 shows the structure of the CaF2 crystal forming the first parallel planar substrate 61. The CaF2 crystal is composed of calcium ions (Ca 2+ ) has a face-centered cubic lattice structure, and fluoride ions (F - ) has a simple cubic lattice structure. Also, the calcium ion is located at the body center of the cube formed by the fluoride ion. The fluoride ion is located at the center of the regular tetrahedron formed by the calcium ion.

[0095] In the following explanation, crystal planes in a cubic crystal are denoted as (hkl), and axis directions are denoted as [uvw]. These represent specific planes and axes in a crystal. Furthermore, all axes equivalent to the [uvw] axis, i.e., axes with the same relative relationship to the coordinate axes, are included. <uvw>That's what they say.

[0096] CaF2 crystals exhibit threefold symmetry with respect to the

[0111] axis. That is, when viewing a CaF2 crystal from directly above the

[0111] axis, the angle between the

[0100] axis and the

[0010] axis is 120°, and the angle between the

[0100] axis and the

[0001] axis is 240°. The crystal growth direction of CaF2 crystals is along the

[0111] axis, and the (111) plane has cleavage properties.

[0097] In each of the following examples, the laser beam Lp is incident on the first surface 61a of the first parallel planar substrate 61 as P-polarized light. As described above, the incident angle θ1 of the laser beam Lp incident on the first surface 61a is the Brewster angle. If the refractive index n of the CaF2 crystal is 1.501958, the Brewster angle is approximately 56.34°.

[0098] 6.2 First crystal orientation Figure 11 shows a preferred first crystal orientation in relation to the laser beam Lp incident on the first parallel planar substrate 61. In Figure 11, the first parallel planar substrate 61 is formed such that the

[0111] axis coincides with the electric field axis of the laser beam Lp passing through its interior. That is, the

[0111] axis is parallel to the incident plane and parallel to the direction perpendicular to the optical path axis of the laser beam Lp passing through the interior of the first parallel planar substrate 61.

[0099] In this disclosure, the axis parallel to the field vector of linearly polarized light is referred to as the field axis. Furthermore, if the laser light Lp contains an S-polarized component in addition to a P-polarized component whose polarization direction is parallel to the incident plane, the axis parallel to the field vector of the P-polarized component is referred to as the field axis.

[0100]

[0111] By aligning the axis with the electric field axis of the laser beam Lp, the amount of absorption of the laser beam Lp within the first parallel planar substrate 61 is reduced, resulting in a reduction in thermal stress and birefringence (for details, see U.S. Patent Application Publication No. 2020 / 0067257).

[0101] Note that the

[0111] axis is <111> It is equivalent to the axes other than the

[0111] axis included in

[0111] . For this reason, the first parallel planar substrate 61 has an electric field axis of the P-polarized component of the laser light Lp passing through its interior, <111> It is sufficient that it is formed so as to coincide with one of the axes included in it.

[0102] 6.3 Second crystal orientation Figure 12 shows a preferred second crystal orientation in relation to the laser beam Lp incident on the first parallel planar substrate 61. In Figure 12, the first parallel planar substrate 61 is formed such that the

[0111] axis coincides with the optical path axis of the laser beam Lp passing through its interior. That is, the

[0111] axis is parallel to the incident plane and parallel to the optical path axis of the laser beam Lp passing through the interior of the first parallel planar substrate 61.

[0103]

[0111] By aligning the axis with the optical path axis of the laser beam Lp, the laser beam Lp is incident perpendicularly to the (111) plane, which is the cleavage plane, thus reducing changes in the polarization state of the laser beam Lp, wavefront non-uniformity, etc. (For details, see U.S. Patent No. 6,181,724).

[0104] Furthermore, the first parallel planar substrate 61 has an optical path axis for the laser beam Lp passing through its interior, <111> It is sufficient that it is formed so as to coincide with one of the axes included in it.

[0105] 6.4 Third Crystal Orientation Figure 13 shows a preferred third crystal orientation in relation to the laser beam Lp incident on the first parallel planar substrate 61. In Figure 13, the first parallel planar substrate 61 is formed such that the

[0111] axis is perpendicular to the first surface 61a and the second surface 61b. That is, the first surface 61a and the second surface 61b are (111) surfaces, respectively. Furthermore, the first parallel planar substrate 61 is positioned at a location rotated 60° around the central axis with respect to the arrangement in which the laser beam Lp passes through the plane containing the

[0111] axis and the

[0001] axis.

[0106] By arranging the first parallel planar substrate 61 as described above, the thermal stress caused by the laser beam Lp is reduced (see U.S. Patent Application Publication No. 2011 / 0158281 for details). Furthermore, by making the first surface 61a and the second surface 61b cleavage planes (111) planes, the manufacturing of the first parallel planar substrate 61 becomes easier.

[0107] Furthermore, the surface of the first parallel planar substrate 61 is <111> It is orthogonal to one of the first axes included, and the laser beam Lp is along the first axis <001> It is sufficient that the first axis is positioned at a 60° rotation around the central axis, based on an arrangement that passes through a plane containing one of the second axes included in the first axis. An example of the first axis is the

[0111] axis, and an example of the second axis is the

[0001] axis.

[0108] 7. Modified Master Oscillator Next, modifications of the master oscillator 10 will be described. In each of the above embodiments, the laser apparatus includes a master oscillator 10 configured with an excimer laser apparatus, but the master oscillator 10 can be modified in various ways.

[0109] 7.1 Configuration Figure 14 schematically shows an example of the configuration of a modified laser device 2a. The laser device 2a includes a master oscillator 10a, an MO beam steering unit 20, and a power oscillator 30a. The MO beam steering unit 20 and the power oscillator 30a have the same configuration as in the first embodiment.

[0110] The master oscillator 10a is a solid-state laser device and includes a semiconductor laser 80 that outputs seed light, a titanium-sapphire amplifier 81 that amplifies the seed light, and a wavelength conversion system 82.

[0111] The semiconductor laser 80 uses a CW (Continuous Wave) laser with a wavelength of 773.6 nm as a seed light. This is a distributed feedback type semiconductor laser that outputs a wave laser beam. The temperature of the semiconductor laser 80 By changing the settings, the oscillation wavelength can be changed.

[0112] The titanium-sapphire amplifier 81 includes a titanium-sapphire crystal 81a and a pumping pulse laser 81b. The titanium-sapphire crystal 81a is positioned on the optical path of the seed light. The pumping pulse laser 81b is a laser device that outputs the second harmonic of a YLF laser.

[0113] The wavelength conversion system 82 is a wavelength conversion system that generates fourth harmonic light and includes an LBO (LiB3O5) crystal and a KBBF (KBe2BO3F2) crystal. Each crystal is placed on a rotating stage (not shown) and is configured to allow changing the incident angle of seed light on each crystal.

[0114] 7.2 Operation In the titanium-sapphire amplifier 81, the pumping pulse laser 81b converts the CW laser light, which serves as seed light input to the titanium-sapphire crystal 81a, into pulse laser light and outputs it based on a trigger signal input from the control unit (not shown). The pulse laser light output from the titanium-sapphire amplifier 81 is input to the wavelength conversion system 82. The wavelength conversion system 82 wavelength-converts the input pulse laser light with a wavelength of 773.6 nm into pulse laser light with a wavelength of 193.4 nm and emits it as laser light Lp toward the MO beam steering unit 20.

[0115] In this modified example, the power oscillator 30a is an ArF excimer amplifier that amplifies the 193.4 nm wavelength laser light Lp input from the MO beam steering unit 20.

[0116] 7.3 Other The master oscillator 10a may be a solid-state laser device that emits pulsed laser light with a wavelength of 248.4 nm, and the power oscillator 30a may be a KrF excimer amplifier. In this case, the semiconductor laser 80 outputs CW laser light with a wavelength of 745.2 nm, and the titanium-sapphire amplifier 81 converts the CW laser light input from the semiconductor laser 80 into pulsed laser light and outputs it. In this case, the wavelength conversion system 82 is a wavelength conversion system that generates third harmonic light, and consists of an LBO crystal and CLBO(CsLiB6O 10 The wavelength conversion system 82 emits pulsed laser light with a wavelength of 248.4 nm as laser light Lp by generating second harmonic light with the LBO crystal and third harmonic light with the CLBO crystal.

[0117] The laser device 2a may include any of the power oscillators described in the above embodiment and its modifications instead of the power oscillator 30a.

[0118] 8. Methods for Manufacturing Electronic Devices Figure 15 schematically shows an example configuration of the exposure apparatus 200. The exposure apparatus 200 includes an illumination optical system 204 and a projection optical system 206. The illumination optical system 204 illuminates the reticle pattern of a reticle (not shown) placed on a reticle stage RT with laser light Lp incident from, for example, a laser device 2a. The projection optical system 206 reduces and projects the laser light Lp that has passed through the reticle onto a workpiece (not shown) placed on a workpiece table WT, forming an image. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0119] The exposure apparatus 200 exposes the workpiece with laser light Lp reflecting the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel. After transferring the reticle pattern to the semiconductor wafer through the exposure process described above, a semiconductor device can be manufactured by going through several processes. The semiconductor device is an example of an "electronic device" in this disclosure.

[0120] The laser device that outputs laser light Lp to the exposure apparatus 200 may be any of the laser devices described in the above embodiment and its modifications.

[0121] The above description is intended to be illustrative and not restrictive. It will therefore be apparent to those skilled in the art that modifications can be made to each embodiment of this disclosure without departing from the scope of the attached claims.

[0122] Terms used throughout this specification and the accompanying claims should be interpreted as “non-limiting.” For example, the terms “includes” or “contains” should be interpreted as “not limited to what is described as included.” The term “has” should be interpreted as “not limited to what is described as having.” Furthermore, the modifying phrase “one” as used throughout this specification and the accompanying claims should be interpreted as “at least one” or “one or more.”< / uvw>

Claims

1. An oscillator that emits laser light, An amplifier that amplifies the laser light in a chamber containing a pair of discharge electrodes, A front optical system and a rear optical system are arranged opposite each other across the chamber and constitute a ring resonator including a first optical path and a second optical path that intersect between the pair of discharge electrodes, A first parallel planar substrate is arranged on the first optical path and has a first plane and a second plane that are parallel to each other and face each other, the laser light is incident on the first plane and the laser light is emitted from the second plane, Equipped with, The first optical path is an optical path through which the front optical system emits the laser light incident from the oscillator toward the rear optical system. The second optical path is an optical path through which the rear optical system emits the laser light incident via the first optical path toward the front optical system. The first parallel-plane substrate is positioned between the chamber and the front-side optical system, and by refracting light incident from the first plane and causing it to exit from the second plane, the first optical path is brought closer to the second optical path between the second plane and the chamber than when the first parallel-plane substrate is not present. Laser device.

2. A laser apparatus according to claim 1, The first optical path and the second optical path are included in a plane perpendicular to the discharge direction by the pair of discharge electrodes, The first parallel planar substrate brings the first optical path closer to the second optical path in a direction perpendicular to the discharge direction.

3. A laser apparatus according to claim 1, The invention further comprises a second parallel planar substrate arranged on the second optical path, having a third plane and a fourth plane that are parallel to each other and facing each other, with the laser light incident on the third plane and the laser light emitted from the fourth plane.

4. A laser apparatus according to claim 3, The first parallel planar substrate and the second parallel planar substrate are arranged between the chamber and the front-side optical system. The second parallel-plane substrate refracts light incident from the third plane and causes it to exit from the fourth plane, thereby moving the second optical path further from the first optical path between the fourth plane and the front optical system than would be possible if the second parallel-plane substrate were not present.

5. A laser apparatus according to claim 4, A third parallel planar substrate is disposed on the first optical path between the chamber and the rear optical system, The system further comprises a fourth parallel planar substrate disposed on the second optical path between the chamber and the rear optical system, The third parallel planar substrate refracts the incident light, thereby moving the first optical path further away from the second optical path between the third parallel planar substrate and the rear optical system than would be possible if the third parallel planar substrate were not present. The fourth parallel-plane substrate refracts the incident light, thereby bringing the second optical path closer to the first optical path between the fourth parallel-plane substrate and the chamber than would be possible if the fourth parallel-plane substrate were not present.

6. A laser apparatus according to claim 3, The first parallel planar substrate and the second parallel planar substrate each have an inclined surface that is tilted with respect to the plane into which the laser light is incident, and the inclined surface of the first parallel planar substrate and the inclined surface of the second parallel planar substrate face each other.

7. A laser apparatus according to claim 6, The inclined surface of the first parallel planar substrate and the inclined surface of the second parallel planar substrate are separated from each other.

8. A laser apparatus according to claim 1, The front optical system includes an output coupling mirror and a high-reflection mirror. The output coupling mirror transmits the laser light incident from the oscillator and causes it to travel along the first optical path.

9. A laser apparatus according to claim 8, The high-reflectivity mirror reflects the laser light traveling through the second optical path and incident on the front optical system toward the output coupling mirror. The output coupling mirror transmits a portion of the laser light incident from the high-reflection mirror, causing it to exit the front-side optical system and reflect a portion of it, allowing it to travel along the first optical path.

10. A laser apparatus according to claim 1, The front optical system includes an output coupling mirror, a first high-reflection mirror, and a second high-reflection mirror. The output coupling mirror transmits the laser light incident from the oscillator and causes it to travel along the first optical path.

11. A laser apparatus according to claim 10, The first high-reflection mirror reflects the laser light traveling through the second optical path and incident on the front optical system toward the second high-reflection mirror. The second high-reflection mirror reflects the laser light incident from the first high-reflection mirror toward the output coupling mirror. The output coupling mirror transmits a portion of the laser light incident from the second high-reflection mirror, causing it to exit the front-side optical system and reflect a portion of it, allowing it to travel along the first optical path.

12. A laser apparatus according to claim 1, The rear optical system includes a first high-reflection mirror and a second high-reflection mirror. The first high-reflection mirror reflects the laser light traveling along the first optical path and incident on the rear optical system toward the second high-reflection mirror. The second high-reflection mirror reflects the laser light incident from the first high-reflection mirror and causes it to propagate along the second optical path.

13. A laser apparatus according to claim 1, The angle of incidence of the laser beam incident on the first parallel planar substrate is the Brewster angle.

14. A laser apparatus according to claim 13, The first parallel planar substrate is formed of calcium fluoride.

15. A laser apparatus according to claim 14, The first parallel planar substrate has an electric field axis that coincides with one of the axes included in <111> of the P-polarized component of the laser light passing through its interior.

16. A laser apparatus according to claim 14, The optical path axis of the laser light passing through the first parallel planar substrate coincides with one of the axes included in <111>.

17. A laser apparatus according to claim 14, The first parallel planar substrate has a surface perpendicular to one first axis included in <111>, and is positioned at a location rotated 60° around the first axis as the central axis, with reference to an arrangement in which the laser beam passes through a plane including the first axis and one second axis included in <001>.

18. A laser apparatus according to claim 1, The oscillator is a solid-state laser device.

19. A method for manufacturing electronic devices, An oscillator that emits laser light, An amplifier that amplifies the laser light in a chamber containing a pair of discharge electrodes, A front optical system and a rear optical system are arranged opposite each other across the chamber and constitute a ring resonator including a first optical path and a second optical path that intersect between the pair of discharge electrodes, A first parallel planar substrate is arranged on the first optical path and has a first plane and a second plane that are parallel to each other and face each other, the laser light is incident on the first plane and the laser light is emitted from the second plane, Equipped with, The first optical path is an optical path through which the front optical system emits the laser light incident from the oscillator toward the rear optical system. The second optical path is an optical path through which the rear optical system emits the laser light incident via the first optical path toward the front optical system. The first parallel-plane substrate is positioned between the chamber and the front-side optical system, and by refracting light incident from the first plane and causing it to exit from the second plane, the first optical path is brought closer to the second optical path between the second plane and the chamber than when the first parallel-plane substrate is not present. The laser light is generated by the laser device, The laser light is output to the exposure apparatus, To manufacture an electronic device, the process involves exposing a photosensitive substrate to laser light within the exposure apparatus. A method for manufacturing electronic devices.

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