Optical Pulse Expander, Laser Device, and Method for Manufacturing Electronic Device

Abstract

The optical pulse stretcher has: a first delay optical system including a plurality of concave toroidal mirrors; and a beam splitter including a first surface and a second surface, which transmits a part of the pulsed laser incident on the first surface in a first direction to emit as a first beam, reflects the other part in a second direction to be incident on the first delay optical system, and reflects a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction to emit as a second beam.

Description

Technical Field

[0001] The present disclosure relates to an optical pulse stretcher, a laser device, and a manufacturing method of an electronic device. Background Art

[0002] With the miniaturization and high integration of semiconductor integrated circuits, an improvement in resolution is required in semiconductor exposure apparatuses. Hereinafter, a semiconductor exposure apparatus will be simply referred to as an "exposure apparatus". Therefore, the shortening of the wavelength of light output from an exposure light source has been developed. In the exposure light source, a gas laser device is used instead of an existing mercury lamp. Currently, as a gas laser device for exposure, a KrF excimer laser device that outputs ultraviolet light with a wavelength of 248 nm and an ArF excimer laser device that outputs ultraviolet light with a wavelength of 193 nm are used.

[0003] As a current exposure technique, the following immersion exposure has been put into practical use: A liquid is filled in a gap between a projection lens on the exposure apparatus side and a wafer, and by changing the refractive index of the gap, the apparent wavelength of the exposure light source is shortened. In the case of performing immersion exposure using an ArF excimer laser device as an exposure light source, ultraviolet light with a wavelength of 134 nm in water is irradiated onto the wafer. This technique is called ArF immersion exposure. ArF immersion exposure is also called ArF immersion lithography.

[0004] The spectral line width in the natural oscillation of a KrF or ArF excimer laser device is relatively wide, about 350 to 400 pm. Therefore, chromatic aberration of the laser (ultraviolet light) that is reduced and projected onto the wafer through the projection lens on the exposure apparatus side occurs, and the resolution is lowered. Therefore, it is necessary to narrow the spectral line width of the laser output from the gas laser device to such an extent that chromatic aberration can be ignored. The spectral line width is also called the spectral width. Therefore, a line narrow module having a narrowbanding element may be provided in the laser resonator of the gas laser device, and the spectral width is narrowed by this narrowbanding module. In addition, the narrowbanding element is an etalon, a grating, or the like. A laser device having such a narrowed spectral width is called a narrowbanded laser device.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: U.S. Patent No. 7,822,092 Specification

[0008] Patent Document 2: U.S. Patent No. 7,999,915 Specification

[0009] Patent Document 3: U.S. Patent No. 7,778,302 Specification

[0010] Patent Document 4: Specification of U.S. Patent Application Publication No. 2016 / 0248219

[0011] Patent Document 5: Specification of U.S. Patent Application Publication No. 2018 / 0254600 SUMMARY OF THE INVENTION

[0012] An optical pulse stretcher according to one aspect of the present disclosure includes: a first delay optical system including a plurality of concave toroidal mirrors; and a beam splitter including a first surface and a second surface, which transmits a part of the pulsed laser incident on the first surface in a first direction to emit a first beam, reflects another part in a second direction to be incident on the first delay optical system, and reflects a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction to emit a second beam.

[0013] A laser device according to one aspect of the present disclosure includes: a master oscillator that outputs pulsed laser; and a first optical pulse stretcher having a first delay optical system and a beam splitter. The first delay optical system includes a plurality of concave toroidal mirrors, and the beam splitter includes a first surface and a second surface, which transmits a part of the pulsed laser incident on the first surface in a first direction to emit a first beam, reflects another part in a second direction to be incident on the first delay optical system, and reflects a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction to emit a second beam. The first optical pulse stretcher is disposed on the optical path of the pulsed laser output from the master oscillator.

[0014] A method for manufacturing an electronic device according to one aspect of the present disclosure includes the following steps: generating pulsed laser by a laser device, outputting the pulsed laser to an exposure device, and exposing the pulsed laser on a photosensitive substrate in the exposure device to manufacture an electronic device. The laser device includes: a master oscillator that outputs pulsed laser; and a first optical pulse stretcher having a first delay optical system and a beam splitter. The first delay optical system includes a plurality of concave toroidal mirrors, and the beam splitter includes a first surface and a second surface, which transmits a part of the pulsed laser incident on the first surface in a first direction to emit a first beam, reflects another part in a second direction to be incident on the first delay optical system, and reflects a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction to emit a second beam. The first optical pulse stretcher is disposed on the optical path of the pulsed laser output from the master oscillator. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the drawings.

[0016] Figure 1 Schematically shows the structure of a laser device of a comparative example.

[0017] Figure 2 Schematically shows the structure of the laser device in the first embodiment of the present disclosure.

[0018] Figure 3A It is a view of the first optical pulse stretcher in the first embodiment as viewed in the -Z direction.

[0019] Figure 3B It is a view of the first optical pulse stretcher in the first embodiment as viewed in the -H direction.

[0020] Figure 3C It is a view of the first optical pulse stretcher in the first embodiment as viewed in the +V direction.

[0021] Figure 3D It is a perspective view of the first optical pulse stretcher in the first embodiment.

[0022] Figure 3E Shows the optical axis of the pulsed laser incident on the concave cylindrical mirror and the optical axis of the pulsed laser reflected by the concave cylindrical mirror in the first embodiment.

[0023] Figure 4 Shows an example for explaining the spectral waveform of E95.

[0024] Figure 5A It is a view of the second optical pulse stretcher in the first embodiment as viewed in the -Z direction.

[0025] Figure 5B It is a view of the second optical pulse stretcher in the first embodiment as viewed in the -H direction.

[0026] Figure 6A It is a view of the first optical pulse stretcher in the second embodiment of the present disclosure as viewed in the -Z direction.

[0027] Figure 6B It is a view of the first optical pulse stretcher in the second embodiment as viewed in the -H direction.

[0028] Figure 6C It is a view of the first optical pulse stretcher in the second embodiment as viewed in the +V direction.

[0029] Figure 6D It is a perspective view of the first optical pulse stretcher in the second embodiment.

[0030] Figure 6E Shows the optical axis of the pulsed laser incident on the concave cylindrical mirror and the optical axis of the pulsed laser reflected by the concave cylindrical mirror in the second embodiment.

[0031] Figure 7AIt is a view of the second optical pulse stretcher in the second embodiment when observed in the -Z direction.

[0032] Figure 7B It is a view of the second optical pulse stretcher in the second embodiment when observed in the -H direction.

[0033] Figure 8A It is a view of the first optical pulse stretcher in the third embodiment of the present disclosure when observed in the -Z direction.

[0034] Figure 8B It is a view of the first optical pulse stretcher in the third embodiment when observed in the -H direction.

[0035] Figure 8C It is a view of the first optical pulse stretcher in the third embodiment when observed in the +V direction.

[0036] Figure 8D It is a perspective view of the first optical pulse stretcher in the third embodiment.

[0037] Figure 8E It shows the optical axis of the pulsed laser incident on the concave toroidal mirror and the optical axis of the pulsed laser reflected by the concave toroidal mirror in the third embodiment.

[0038] Figure 9A It is a view of the second optical pulse stretcher in the third embodiment when observed in the -Z direction.

[0039] Figure 9B It is a view of the second optical pulse stretcher in the third embodiment when observed in the -H direction.

[0040] Figure 10 It schematically shows the structure of the laser device in the fourth embodiment of the present disclosure.

[0041] Figure 11 It is a view of the first optical pulse stretcher in the fourth embodiment when observed in the -Z direction.

[0042] Figure 12 It schematically shows the structure of the exposure device connected to the laser device. Detailed Description

[0043] <Content>

[0044] 1. Comparative Example

[0045] 1.1 Structure of Laser Device

[0046] 1.2 Operation of Laser Device

[0047] 1.3 Problems

[0048] 2. Optical Pulse Stretcher Using a Cylindrical Mirror That Condenses Light in the Z Direction

[0049] 2.1 Schematic Structure

[0050] 2.2 Structure of the First Optical Pulse Stretcher

[0051] 2.3 Operation of the First Optical Pulse Stretcher

[0052] 2.4 Function of the First Optical Pulse Stretcher

[0053] 2.5 Structure of the Second Optical Pulse Stretcher

[0054] 2.6 Operation of the Second Optical Pulse Stretcher

[0055] 2.7 Function of the Second Optical Pulse Stretcher

[0056] 3. Optical Pulse Stretcher Using a Cylindrical Mirror That Condenses Light in the Direction of the Short Side of the Beam Cross-Section

[0057] 3.1 Structure and Operation of the First Optical Pulse Stretcher

[0058] 3.2 Function of the First Optical Pulse Stretcher

[0059] 3.3 Structure and Operation of the Second Optical Pulse Stretcher

[0060] 3.4 Function of the Second Optical Pulse Stretcher

[0061] 4. Optical Pulse Stretcher Using a Toroidal Mirror That Condenses Light in Two Directions

[0062] 4.1 Structure and Operation of the First Optical Pulse Stretcher

[0063] 4.2 Function of the First Optical Pulse Stretcher

[0064] 4.3 Structure and Operation of the Second Optical Pulse Stretcher

[0065] 4.4 Function of the Second Optical Pulse Stretcher

[0066] 5. Optical Pulse Stretcher Capable of Changing the Output Beam Position

[0067] 5.1 Schematic Structure

[0068] 5.2 Structure of the First Optical Pulse Stretcher

[0069] 5.3 Operation

[0070] 5.4 Function

[0071] 6. Others

[0072] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The embodiments described below show several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and operations described in each embodiment are not necessarily all essential to the structures and operations of the present disclosure. In addition, the same reference numerals are assigned to the same structural elements and repeated descriptions are omitted.

[0073] 1. Comparative Example

[0074] 1.1 Structure of Laser Device

[0075] Figure 1 The structure of the laser device of the comparative example is schematically shown. The laser device of the comparative example includes a master oscillator MO, a first beam steering unit 16, an amplifier PO, a second beam steering unit 26, and an optical pulse stretcher 29. The traveling directions of the pulsed lasers B99 and B100 output from the optical pulse stretcher 29 are set as the +Z direction. The discharge directions between the discharge electrodes 11a and 11b of the master oscillator MO and between the discharge electrodes 21a and 21b of the amplifier PO are set as the +V direction or the -V direction. The directions perpendicular to both of them are set as the +H direction and the -H direction.

[0076] The master oscillator MO includes a laser cavity 10, a narrowbanding module 14, and an output coupling mirror 15.

[0077] The laser cavity 10 is disposed on the optical path of the laser resonator formed by the narrowbanding module 14 and the output coupling mirror 15. Two windows 10a and 10b are provided in the laser cavity 10. The laser cavity 10 houses the discharge electrodes 11a and 11b. The discharge electrodes 11a and 11b are connected to a pulse power supply (not shown). The laser cavity 10 houses a laser gas as a laser medium. The laser gas contains, for example, argon, fluorine, and neon. Alternatively, the laser gas contains, for example, krypton, fluorine, and neon.

[0078] The narrowbanding module 14 includes wavelength selection elements such as a prism 14a and a grating 14b. The output coupling mirror 15 is composed of a partial reflector.

[0079] The first beam steering unit 16 includes high reflection mirrors 16a and 16b.

[0080] The amplifier PO includes a laser cavity 20, a rear mirror 24, and an output coupling mirror 25. The laser cavity 20, the output coupling mirror 25, the windows 20a and 20b attached to the laser cavity 20, and the discharge electrodes 21a and 21b are the same as the corresponding structural elements in the master oscillator MO.

[0081] The rear mirror 24 is disposed on the optical path of the pulsed laser after passing through the first beam steering unit 16. The rear mirror 24 is composed of a partial reflector. An optical resonator is formed by the rear mirror 24 and the output coupling mirror 25.

[0082] The second beam steering unit 26 includes high reflectors 26a and 26b.

[0083] The optical pulse stretcher 29 is arranged on the optical path of the pulsed laser after passing through the second beam steering unit 26. The optical pulse stretcher 29 includes a beam splitter 295 and first to fourth concave mirrors 291 to 294. The first to fourth concave mirrors 291 to 294 are spherical mirrors respectively. The optical path length of the delay optical path formed by the first to fourth concave mirrors 291 to 294 is, for example, 7 m.

[0084] 1.2 Operation of the laser device

[0085] In the master oscillator MO, a pulsed high voltage is generated by a pulse power supply (not shown), and this high voltage is applied between the discharge electrodes 11a and 11b.

[0086] After applying the high voltage between the discharge electrodes 11a and 11b, a discharge is caused between the discharge electrodes 11a and 11b. By the energy of this discharge, the laser gas in the laser cavity 10 is excited and transitions to a high energy level. Then, when the excited laser gas transitions to a low energy level, light corresponding to the energy level difference is emitted.

[0087] The light generated in the laser cavity 10 exits to the outside of the laser cavity 10 via the windows 10a and 10b. The light exiting from the window 10a has its beam width amplified by the prism 14a and is incident on the grating 14b. The light incident on the grating 14b from the prism 14a is reflected by the multiple grooves of the grating 14b and diffracted in the direction corresponding to the wavelength of the light. The grating 14b is in a Littrow configuration so that the incident angle of the light incident on the grating 14b from the prism 14a is the same as the diffraction angle of the diffracted light of the desired wavelength. Thus, the light near the desired wavelength returns to the laser cavity 10 via the prism 14a.

[0088] The output coupling mirror 15 allows a part of the light exiting from the window 10b to pass through and be output, and reflects the other part back to the laser cavity 10.

[0089] In this way, the light exiting from the laser cavity 10 reciprocates between the narrowbanding module 14 and the output coupling mirror 15. This light is amplified every time it passes through the discharge space between the discharge electrodes 11a and 11b. In addition, this light is narrowed every time it turns back in the narrowbanding module 14. Laser oscillation is performed in this way, and the narrowed light is output as pulsed laser light from the output coupling mirror 15.

[0090] The pulsed laser light output from the output coupling mirror 15 is incident on the laser cavity 20 via the first beam steering unit 16 and the rear mirror 24.

[0091] Synchronously with the incidence of pulsed laser into the laser cavity 20, in the amplifier PO, a pulsed power supply (not shown) generates a pulsed high voltage, which is applied between the discharge electrodes 21a and 21b.

[0092] After applying the high voltage between the discharge electrodes 21a and 21b, a discharge is caused between the discharge electrodes 21a and 21b. By the energy of this discharge, the pulsed laser incident into the laser cavity 20 is amplified.

[0093] The light amplified in the laser cavity 20 reciprocates between the rear mirror 24 and the output coupling mirror 25. This light is amplified every time it passes through the discharge space between the discharge electrodes 21a and 21b. The light amplified in this way is output as pulsed laser from the output coupling mirror 2.

[0094] The pulsed laser output from the output coupling mirror 25 is incident on the beam splitter 295 of the optical pulse stretcher 29 in the +Z direction via the second beam turning unit 26. The beam splitter 295 transmits a part of the pulsed laser incident in the +Z direction in the +Z direction and outputs it as pulsed laser B99, and reflects the other part in the -V direction. The pulsed laser reflected in the -V direction is sequentially reflected by the first to fourth concave mirrors 291 to 294 and is incident on the beam splitter 295 in the -V direction.

[0095] By the first to fourth concave mirrors 291 to 294, the pulsed laser incident from the second beam turning unit 26 is imaged on the beam splitter 295 with a beam cross section of 1:1 size in the beam splitter 295. The beam splitter 295 reflects a part of the pulsed laser incident from the fourth concave mirror 294 in the -V direction in the +Z direction and outputs it as pulsed laser B100. The pulsed laser B99 and the pulsed laser B100 are substantially coaxial.

[0096] Between the pulsed laser B99 and the pulsed laser B100, there is a time difference corresponding to the optical path length of the delay optical path formed by the first to fourth concave mirrors 291 to 294. By spatially overlapping the pulsed laser B99 and the pulsed laser B100, a pulsed laser with an extended pulse width can be output.

[0097] By extending the pulse width of the pulsed laser, the generation of speckles on the surface of the workpiece is suppressed. Speckles are bright and dark spots generated by interference when the pulsed laser is scattered to equalize the light intensity distribution of the pulsed laser. The image obtained by photographing the bright and dark spots is called a speckle image. As an evaluation index of speckles, the following speckle contrast SC is generally used.

[0098] SC = σ(I) / Avg(I)

[0099] Here, σ(I) is the standard deviation of the intensity I in the speckle image, and Avg(I) is the average value of the intensity I.

[0100] 1.3 Subject

[0101] In the comparative example, the pulse width is extended by the optical pulse stretcher 29, thereby reducing the speckle contrast. By additionally arranging another optical pulse stretcher with a different optical path length of the delay optical path, the pulse width is further extended, and thus, the speckle contrast can be further reduced.

[0102] However, for example, when adding another optical pulse stretcher with a different optical path length of the delay optical path on the basis of the optical pulse stretcher 29 with an optical path length of the delay optical path of 7 m, a delay optical path of 14 m, 35 m, and even longer is required, which may be inconvenient during handling and maintenance.

[0103] On the other hand, even if adding an optical pulse stretcher with a shorter delay optical path, the effect of extending the pulse width is reduced. In addition, in the case of forming a shorter delay optical path by using the first to fourth concave mirrors, it is necessary to increase the incident angle of the pulsed laser onto the first to fourth concave mirrors, and it is also necessary to increase the numerical aperture (NA) of the first to fourth concave mirrors. Therefore, astigmatism may occur. When astigmatism occurs, it may have an adverse effect on the beam divergence and the beam pointing.

[0104] In several embodiments described below, in the optical pulse stretcher with a shorter delay optical path, an aspheric mirror is used instead of a spherical mirror and a plane mirror, thereby suppressing the generation of astigmatism.

[0105] 2. Optical Pulse Stretcher Using a Cylindrical Mirror that Condenses Light in the Z Direction

[0106] 2.1 Schematic Structure

[0107] Figure 2 The structure of the laser device in the first embodiment of the present disclosure is schematically shown. In the first embodiment, the first optical pulse stretcher 17 using the first delay optical system including a plurality of concave aspheric mirrors is disposed between the high reflectors 16a and 16b. That is, the first optical pulse stretcher 17 is disposed between the master oscillator MO and the power oscillator PO.

[0108] In the first embodiment, the second optical pulse stretcher 27 using a plurality of concave aspheric mirrors is further disposed between the high reflectors 26a and 26b.

[0109] In other aspects, the structure of the first embodiment is the same as that of the comparative example.

[0110] 2.2 Structure of the First Optical Pulse Stretcher

[0111] Figure 3A This is a view of the first optical pulse stretcher 17 in the first embodiment when observing in the -Z direction.Figure 3B View of the first optical pulse stretcher 17 in the -H direction. Figure 3C View of the first optical pulse stretcher 17 in the +V direction. Figure 3D Perspective view of the first optical pulse stretcher 17. Between the high reflectors 16a and 16b, the traveling direction of the pulsed laser is approximately in the +V direction.

[0112] The first optical pulse stretcher 17 includes: a first delay optical system including four concave cylindrical mirrors 171 to 174 as a plurality of concave toroidal mirrors, a beam splitter 175 including a first surface 175a and a second surface 175b, and a parallel plate 176.

[0113] The beam splitter 175 is disposed on the optical path of the pulsed laser B1 output from the master oscillator MO and reflected by the high reflector 16a. As the beam splitter 175, for example, a beam splitter having a thickness of 7 mm and a reflectivity of 64% for P-polarized light is used.

[0114] A toroidal mirror is a mirror having a toroid. A toroid is a surface having different first and second radii of curvature R1 and R2 in two orthogonal directions, and corresponds to the locus when a circle having a radius R1 rotates in the same plane as the circle about a straight line at a distance R3 from the center of the circle. Here, the first radius of curvature R1 of the toroid corresponds to the radius R1 of the circle, and the second radius of curvature R2 corresponds to the sum of the radius R1 of the circle and the distance R3 from the center of the circle to the rotation axis.

[0115] A cylindrical mirror is a mirror having a cylindrical surface. A cylindrical mirror is a type of toroidal mirror and can refer to a toroidal mirror with an infinite second radius of curvature R2.

[0116] The first optical pulse stretcher 17 constitutes a first optical path and a second optical path. The first optical path is an optical path through which a part of the pulsed laser B1 passes to become the pulsed laser B2 and is output as the pulsed laser B3. The second optical path is an optical path through which another part of the pulsed laser B1 is reflected to become the pulsed lasers B4, B5, …, B9 and is output as the pulsed laser B10. The optical paths of the pulsed lasers B4 to B8 in the second optical path are referred to as delay optical paths.

[0117] The optical path length of the delay optical path is in the range of 0.25 m or more and 1.5 m or less, for example, 0.3 m. When the optical path length of the delay optical path is 0.3 m, the first radius of curvature R1 of each of the concave cylindrical mirrors 171 to 174 is, for example, 81.6 mm. The reason for setting the optical path length of the delay optical path to 0.25 m or more is as follows. When the center wavelength λ0 of the pulsed laser is 193 nm and the spectral width Δλ is 0.15 pm, the temporal coherence length L of the pulsed laser is approximately 0.25 m as follows.

[0118] L = λ0 2 / Δλ

[0119] ≈ 0.25

[0120] When a time difference is imparted to the branched light through a delay optical path and they are made to coincide thereafter, interference sometimes occurs when the optical path length of the delay optical path is shorter than the temporal coherence length L. Therefore, it is preferable that the optical path length of the delay optical path is equal to or longer than the temporal coherence length L, that is, 0.25 m or longer.

[0121] As the above spectral width Δλ, for example, an index called E95 is used.

[0122] Figure 4 An example of a spectral waveform for explaining E95 is shown. Figure 4 The horizontal axis is the wavelength λ and the vertical axis is the light intensity I. The full width of the part that occupies 95% of the total energy of the spectrum centered on the central wavelength λ0 is defined as E95.

[0123] Figure 3E The optical axes of the pulsed laser B7 incident on the concave cylindrical mirror 174 and the pulsed laser B8 reflected by the concave cylindrical mirror 174 are shown. The optical axis means the central axis of the optical path.

[0124] As Figure 3E shown, the focal axis F is located at a position at a prescribed distance from the concave cylindrical mirror 174. The focal axis F is in the same plane as the incident surface IP of the pulsed laser B7. In the other concave cylindrical mirrors 171 to 173, their respective focal axes F are also in the same plane as the incident surface IP of the pulsed laser.

[0125] As Figure 3C shown, the pulsed laser B1 has a beam cross section with a substantially rectangular shape. The length direction of the beam cross section is substantially parallel to the Z direction. The length directions of the beam cross sections of the pulsed lasers B2 to B10 are also substantially parallel to the Z direction.

[0126] However, the pulsed laser B5 reflected by the concave cylindrical mirror 171 is condensed in the Z direction, then expanded in the Z direction and incident on the concave cylindrical mirror 172. The pulsed laser B7 reflected by the concave cylindrical mirror 173 is also condensed in the Z direction, then expanded in the Z direction and incident on the concave cylindrical mirror 174. Therefore, except near their condensation positions, the length directions of the beam cross sections of the pulsed lasers B5 and B7 are substantially parallel to the Z direction.

[0127] The concave cylindrical mirror 172 and the concave cylindrical mirror 174 reflect the pulsed lasers B5 and B7 that pass through the condensation position and are expanded and incident in the Z direction to become the pulsed lasers B6 and B8, respectively, thereby performing collimation.

[0128] The concave cylindrical mirror 171 or 173 corresponds to the first concave cylindrical mirror of the present disclosure, and the concave cylindrical mirror 172 or 174 corresponds to the second concave cylindrical mirror of the present disclosure.

[0129] The pulsed laser B4 is incident obliquely on the concave cylindrical mirror 171 about the axis in the Z direction. Similarly, the pulsed lasers B5, B6, and B7 are incident obliquely on the concave cylindrical mirrors 172, 173, and 174 about the axis in the Z direction, respectively. The incident angles θ1 of the pulsed lasers B4 to B7 with respect to the concave cylindrical mirrors 171 to 174 are in the range of 8° or more and 25° or less. For example, the incident angle θ1 becomes 23°. Thus, even when the incident angle θ1 is large, the generation of astigmatism is suppressed because the first delay optical system is constituted by the concave cylindrical mirrors 171 to 174.

[0130] 2.3 Operation of the first optical pulse stretcher

[0131] The pulsed laser B1 is incident on the first surface 175a of the beam splitter 175 in the +V direction. The beam splitter 175 transmits a part of the pulsed laser B1 incident in the +V direction in the +V direction to become the pulsed laser B2, and reflects the other part in the +H direction to become the pulsed laser B4. The pulsed laser B2 is incident on the parallel plate 176. The parallel plate 176 transmits the pulsed laser B2 in the +V direction and emits it as the pulsed laser B3. The +V direction corresponds to the first direction in the present disclosure. The +H direction corresponds to the second direction in the present disclosure.

[0132] The pulsed laser B4 is reflected successively by the concave cylindrical mirrors 171 to 174 to become the pulsed lasers B5 to B8. The pulsed laser B8 is incident on the second surface 175b of the beam splitter 175 in the +H direction. The concave cylindrical mirrors 171 and 173 condense the pulsed lasers B5 and B7, respectively, with a large NA, and the concave cylindrical mirrors 172 and 174 collimate them, thereby reducing the spatial coherence. Regarding the beam cross-section of the pulsed laser B1 in the first surface 175a, when the pulsed laser B8 reaches the first surface 175a, it is imaged in a 1:1 size in the Z direction. A part of the pulsed laser B8 is reflected from the first surface 175a and emitted in the +V direction as the pulsed laser B9, and then emitted from the parallel plate 176 as the pulsed laser B10. The pulsed lasers B9 and B10 pass through substantially the same optical paths as the pulsed lasers B2 and B3, respectively. The pulsed laser B3 corresponds to the first beam in the present disclosure, and the pulsed laser B10 corresponds to the second beam in the present disclosure.

[0133] The parallel plate 176 compensates for the offset of the optical axis generated when a part of the pulsed laser B1 passes through the beam splitter 175. Thereby, the parallel plate 176 can make the optical axis of the pulsed laser B3 substantially coaxial with the extension line of the optical axis of the pulsed laser B1. The parallel plate 176 corresponds to the optical element that compensates for the offset of the optical axis in the present disclosure.

[0134] 2.4 Function of the First Optical Pulse Expander

[0135] According to the first embodiment, the first optical pulse expander 17 spatially overlaps and emits the pulsed laser B3 that has passed through the beam splitter 175 and the pulsed laser B10 that is reflected by the beam splitter 175 and has its spatial coherence reduced by the first delay optical system. Thereby, the speckle contrast can be reduced.

[0136] According to the first embodiment, since the optical path length of the delay optical path is short, the first optical pulse expander 17 can be made compact. Therefore, the first optical pulse expander 17 can also be arranged inside the laser device. For example, the first optical pulse expander 17 can be arranged between the master oscillator MO and the power amplifier PO. In addition, the handling and maintenance of components can be easily performed.

[0137] According to the first embodiment, since the concave cylindrical mirrors 171 to 174 are used, even when the optical path length of the delay optical path is short and the incident angle θ1 is large, the generation of astigmatism is suppressed. Therefore, adverse effects on the beam divergence and beam pointing can be suppressed.

[0138] In addition, it is assumed that the delay optical path is constituted by the transfer optical system and imaged in the Z direction. Therefore, the beam expansion of the output pulsed laser B10 in the Z direction is reduced. Therefore, the energy loss is reduced.

[0139] 2.5 Structure of the Second Optical Pulse Expander

[0140] Figure 5A This is a view of the second optical pulse expander 27 in the first embodiment as viewed in the -Z direction. Figure 5B This is a view of the second optical pulse expander 27 as viewed in the -H direction. Between the high reflectors 26a and 26b, the traveling direction of the pulsed laser is substantially in the -V direction.

[0141] The second optical pulse expander 27 includes two delay optical paths with different optical path lengths. The second optical pulse expander 27 includes: a second delay optical system including four concave cylindrical mirrors 271 to 274, a third delay optical system including another four concave cylindrical mirrors 281 to 284, beam splitters 275 and 285, and a parallel plate 276. Preferably, the optical path lengths of the first, second, and third delay optical systems are different respectively. Alternatively, the optical path length of the first delay optical system may be shorter than the optical path length of the second delay optical system, and the optical path length of the second delay optical system may be shorter than the optical path length of the third delay optical system. The optical path length of the delay optical path constituted by the second delay optical system is set to 0.6 m, for example, and the optical path length of the delay optical path constituted by the third delay optical system is set to 1.2 m, for example.

[0142] The first curvature radius R1 of each of the concave cylindrical mirrors 271 to 274 is, for example, 153.7 mm. The first curvature radius R1 of each of the concave cylindrical mirrors 281 to 284 is, for example, 303.4 mm.

[0143] As the beam splitters 275 and 285, beam splitters having a thickness of 7 mm and a reflectivity of 64% for P-polarized light are used, for example.

[0144] The incident angle θ2 of the pulsed laser with respect to the concave cylindrical mirrors 271 to 274 is in the range of 8° or more and 25° or less. For example, the incident angle θ2 becomes 14°.

[0145] The incident angle θ3 of the pulsed laser with respect to the concave cylindrical mirrors 281 to 284 is in the range of 8° or more and 25° or less. For example, the incident angle θ3 becomes 9°.

[0146] Regarding other aspects, the structure of the second optical pulse stretcher 27 is the same as the structure of the first optical pulse stretcher 17.

[0147] 2.6 Operation of the Second Optical Pulse Stretcher

[0148] The pulsed laser B11 output from the amplifier PO is incident on the third surface 275a of the beam splitter 275 in the -V direction. The beam splitter 275 transmits a part of the pulsed laser B11 incident in the -V direction in the -V direction to become the pulsed laser B13, and reflects the other part in the -H direction to become the pulsed laser B14. The pulsed laser B13 is incident on the parallel plate 276. The parallel plate 276 transmits the pulsed laser B13 in the -V direction to become the pulsed laser B21. The -V direction corresponds to the third direction in the present disclosure. The -H direction corresponds to the fourth direction in the present disclosure.

[0149] The pulsed laser B14 is reflected successively by the concave cylindrical mirrors 271 to 274 to become the pulsed lasers B15 to B18. The pulsed laser B18 is incident on the fourth surface 275b of the beam splitter 275 in the -H direction. The concave cylindrical mirrors 271 and 273 condense the pulsed lasers B15 and B17 in the Z direction with a large NA, respectively, and the concave cylindrical mirrors 272 and 274 collimate them, thereby reducing the spatial coherence. Regarding the beam cross section of the pulsed laser B11 in the third surface 275a, when the pulsed laser B18 reaches the third surface 275a, it is imaged in the Z direction at a ratio of 1:1. A part of the pulsed laser B18 is reflected from the third surface 275a and exits in the -V direction as the pulsed laser B20, and then exits from the parallel plate 276 as the pulsed laser B21. The pulsed laser B20 passes through substantially the same optical path as the pulsed laser B13. The pulsed laser B13 corresponds to the first beam in the present disclosure, and the pulsed laser B20 corresponds to the second beam in the present disclosure.

[0150] Here, the operation of the second delay optical system including the concave cylindrical mirrors 271 to 274 is described. However, the operation of the third delay optical system including the concave cylindrical mirrors 281 to 284 is the same.

[0151] The parallel plate 276 can compensate for the deviation of the optical axis generated when the pulsed laser passes through the beam splitters 275 and 285, or can shift the optical axis to other desired positions.

[0152] 2.7 Function of the Second Optical Pulse Expander

[0153] According to the first embodiment, the second optical pulse expander 27 can reduce the speckle contrast by the same function as the first optical pulse expander 17. Since the optical path lengths of the first, second, and third delay optical systems are different respectively, it is possible to prevent a part of the light delayed by one delay optical system from returning to its original state due to another delay optical system. Therefore, based on the effect of reducing the speckle contrast by the first optical pulse expander 17, the speckle contrast can be further reduced by the second optical pulse expander 27.

[0154] 3. Optical Pulse Expander Using a Cylindrical Mirror that Condenses Light in the Short Side Direction of the Beam Cross Section

[0155] 3.1 Structure and Operation of the First Optical Pulse Expander

[0156] Figure 6A It is a view of the first optical pulse expander 17a in the second embodiment of the present disclosure as viewed in the -Z direction. Figure 6B It is a view of the first optical pulse expander 17a as viewed in the -H direction. Figure 6C It is a view of the first optical pulse expander 17a as viewed in the +V direction. Figure 6D It is a perspective view of the first optical pulse expander 17a.

[0157] The first optical pulse expander 17a includes four concave cylindrical mirrors 171a to 174a.

[0158] Figure 6E The optical axis of the pulsed laser B7 incident on the concave cylindrical mirror 174a and the optical axis of the pulsed laser B8 reflected by the concave cylindrical mirror 174a are shown.

[0159] As Figure 6E shown, the focal axis F of the concave cylindrical mirror 174a is perpendicular to the incident plane IP of the pulsed laser B7. In the other concave cylindrical mirrors 171a to 173a, their respective focal axes F are also perpendicular to the incident plane IP of the pulsed laser.

[0160] Thus, in the concave cylindrical mirrors 171a to 174a of the second embodiment, the orientation of the focal axis F is different from that of the concave cylindrical mirrors 171 to 174 of the first embodiment.

[0161] As Figure 6C shown, the pulsed laser B1 has a beam cross-section with a substantially rectangular shape. The length direction of the beam cross-section is substantially parallel to the Z direction. The length directions of the beam cross-sections of the pulsed lasers B2 to B10 are also substantially parallel to the Z direction. In the pulsed lasers B1 to B10, the direction perpendicular to the length direction of the beam cross-section is respectively referred to as the short side direction.

[0162] However, the pulsed laser B5 reflected by the concave cylindrical mirror 171a is condensed along the short side direction of the beam cross-section, then expands along the short side direction of the beam cross-section and is incident on the concave cylindrical mirror 172a. The pulsed laser B7 reflected by the concave cylindrical mirror 173a is also condensed along the short side direction of the beam cross-section, then expands along the short side direction of the beam cross-section and is incident on the concave cylindrical mirror 174a.

[0163] The concave cylindrical mirrors 172a and 174a reflect the pulsed lasers B5 and B7 that pass through the condensing position and expand and are incident along the short side direction of the beam cross-section to become the pulsed lasers B6 and B8 respectively, thereby performing collimation.

[0164] The concave cylindrical mirror 171a or 173a corresponds to the first concave cylindrical mirror of the present disclosure, and the concave cylindrical mirror 172a or 174a corresponds to the second concave cylindrical mirror of the present disclosure.

[0165] In other respects, the structure and operation of the first optical pulse stretcher 17a are the same as those of the first optical pulse stretcher 17 in the first embodiment.

[0166] 3.2 Function of the First Optical Pulse Stretcher

[0167] In the second embodiment, the pulsed laser also passes through the first delay optical system, thereby reducing the spatial coherence, and thus, the speckle contrast can be reduced.

[0168] In addition, the optical path length of the delay optical path is short, and thus, the first optical pulse stretcher 17a can be made compact.

[0169] According to the second embodiment, since the concave cylindrical mirrors 171a to 174a are used, even when the optical path length of the delay optical path is short and the incident angle θ1 is large, the generation of astigmatism is suppressed.

[0170] In addition, it is assumed that the delay optical path is constituted by the transfer optical system and imaging is performed in the short side direction of the beam cross-section. Therefore, the beam expansion of the output pulsed laser B10 in the short side direction of the beam cross-section is reduced. Therefore, the energy loss is reduced.

[0171] 3.3 Structure and Operation of the Second Optical Pulse Expander

[0172] Figure 7A FIG. is a view of the second optical pulse expander 27a in the second embodiment as viewed in the -Z direction. Figure 7B FIG. is a view of the second optical pulse expander 27a as viewed in the -H direction.

[0173] The second optical pulse expander 27a includes: a second delay optical system including four concave cylindrical mirrors 271a to 274a, and a third delay optical system including another four concave cylindrical mirrors 281a to 284a.

[0174] The focal axes F of the concave cylindrical mirrors 271a to 274a and 281a to 284a are perpendicular to the incident plane IP of the pulsed laser.

[0175] Therefore, the concave cylindrical mirrors 271a, 273a, 281a, and 283a condense the pulsed laser in the short side direction of the beam cross section, respectively, and the concave cylindrical mirrors 272a, 274a, 282a, and 284a collimate, thereby reducing the spatial coherence.

[0176] In other respects, the structure and operation of the second optical pulse expander 27a are the same as those of the second optical pulse expander 27 in the first embodiment.

[0177] 3.4 Function of the Second Optical Pulse Expander

[0178] In the second embodiment, the second optical pulse expander 27a can also reduce the speckle contrast by the same action as the first optical pulse expander 17a. Since the optical path lengths of the first, second, and third delay optical systems are different, respectively, it is possible to prevent a part of the light delayed by one delay optical system from returning to its original state due to another delay optical system. Therefore, on the basis of the effect of reducing the speckle contrast by the first optical pulse expander 17a, the speckle contrast can be further reduced by the second optical pulse expander 27a.

[0179] 4. Optical Pulse Expander Using a Hyperboloid Mirror Condensing in Two Directions

[0180] 4.1 Structure and Operation of the First Optical Pulse Expander

[0181] Figure 8A FIG. is a view of the first optical pulse expander 17b in the third embodiment of the present disclosure as viewed in the -Z direction. Figure 8B FIG. is a view of the first optical pulse expander 17b as viewed in the -H direction. Figure 8C FIG. is a view of the first optical pulse expander 17b as viewed in the +V direction.Figure 8D It is a perspective view of the first optical pulse stretcher 17b.

[0182] The first optical pulse stretcher 17b includes four concave toroidal mirrors 171b to 174b.

[0183] Figure 8E The optical axis of the pulsed laser B7 incident on the concave toroidal mirror 174b and the optical axis of the pulsed laser B8 reflected by the concave toroidal mirror 174b are shown.

[0184] As Figure 8E shown, the plane perpendicular to the incident plane IP of the pulsed laser B7 and including the normal line NL of the concave toroidal mirror 174b is defined as the vertical plane VP. The first radius of curvature R1 of the concave toroidal mirror 174b along the vertical plane VP and the second radius of curvature R2 of the concave toroidal mirror 174b along the incident plane IP are defined.

[0185] The first radius of curvature R1 of the concave toroidal mirror 174b along the vertical plane VP corresponds to the radius of curvature of the curve C1 depicted on the surface of the concave toroidal mirror 174b along the vertical plane VP. The second radius of curvature R2 of the concave toroidal mirror 174b along the incident plane IP corresponds to the radius of curvature of the curve C2 depicted on the surface of the concave toroidal mirror 174b along the incident plane IP.

[0186] When light is obliquely incident on a spherical mirror, the converging position of the light in the incident plane approaches the mirror and is offset from the converging position of the light in the direction perpendicular to the incident plane, thus generating astigmatism. Therefore, in the third embodiment, a concave toroidal mirror 174b with a second radius of curvature R2 along the incident plane IP larger than the first radius of curvature R1 along the vertical plane VP is adopted, thereby reducing astigmatism.

[0187] Regarding the other concave toroidal mirrors 171b to 173b, they are also toroidal mirrors with a second radius of curvature R2 along the incident plane IP larger than the first radius of curvature R1 along the vertical plane VP.

[0188] The first radius of curvature R1 along the vertical plane VP is, for example, 78.5 mm.

[0189] The second radius of curvature R2 along the incident plane IP is, for example, 88.5 mm.

[0190] The pulsed laser B5 reflected by the concave toroidal mirror 171b is condensed in two directions, namely, the length direction and the short side direction of the beam cross-section, and then expands and is incident on the concave toroidal mirror 172b in the length direction and the short side direction of the beam cross-section. The pulsed laser B7 reflected by the concave toroidal mirror 173b is also condensed in two directions, namely, the length direction and the short side direction of the beam cross-section, and then expands and is incident on the concave toroidal mirror 174b in the length direction and the short side direction of the beam cross-section.

[0191] The concave toroidal mirror 172b and the concave toroidal mirror 174b reflect the pulsed lasers B5 and B7 that pass through the condensing position and expand and are incident in the length direction and the short side direction of the beam cross-section respectively to become pulsed lasers B6 and B8, thereby performing collimation.

[0192] The concave toroidal mirror 171b or 173b corresponds to the first concave toroidal mirror of the present disclosure, and the concave toroidal mirror 172b or 174b corresponds to the second concave toroidal mirror of the present disclosure.

[0193] In other aspects, the structure and operation of the first optical pulse stretcher 17b are the same as those of the first optical pulse stretcher 17 in the first embodiment.

[0194] 4.2 Function of the First Optical Pulse Stretcher

[0195] In the third embodiment, the pulsed laser also passes through the first delay optical system, thereby reducing the spatial coherence, and thus, the speckle contrast can be reduced.

[0196] In addition, the optical path length of the delay optical path is short, and thus, the first optical pulse stretcher 17b can be made compact.

[0197] According to the third embodiment, since the concave toroidal mirrors 171b to 174b are used, the generation of astigmatism is suppressed even when the optical path length of the delay optical path is short and the incident angle θ1 is large.

[0198] In addition, it is assumed that the delay optical path is constituted by the transfer optical system and imaging is performed in two directions, namely, the length direction and the short side direction of the beam cross-section. Therefore, the beam expansion of the output pulsed laser B10 in the length direction and the short side direction of the beam cross-section is reduced. Therefore, the energy loss is reduced.

[0199] 4.3 Structure and Operation of the Second Optical Pulse Stretcher

[0200] Figure 9A It is a view of the second optical pulse stretcher 27b in the third embodiment when viewed in the -Z direction. Figure 9B It is a view of the second optical pulse stretcher 27b when viewed in the -H direction.

[0201] The second optical pulse stretcher 27b includes: a second delay optical system including four concave toroidal mirrors 271b to 274b, and a third delay optical system including another four concave toroidal mirrors 281b to 284b.

[0202] The concave toroidal mirrors 271b to 274b and 281b to 284b are toroidal mirrors in which the second curvature radius R2 along the incident plane IP is larger than the first curvature radius R1 along the vertical plane VP.

[0203] Therefore, the concave toroidal mirrors 271b, 273b, 281b, and 283b condense the pulsed laser in two directions, namely, the length direction and the short side direction of the beam cross section, respectively, and the concave toroidal mirrors 272b, 274b, 282b, and 284b collimate the light, thereby reducing the spatial coherence.

[0204] The first curvature radius R1 along the vertical plane VP of each of the concave toroidal mirrors 271b to 274b is, for example, 156.5 mm. The second curvature radius R2 along the incident plane IP of each of the concave toroidal mirrors 271b to 274b is, for example, 168.6 mm.

[0205] The first curvature radius R1 along the vertical plane VP of each of the concave toroidal mirrors 281b to 284b is, for example, 303.4 mm. The second curvature radius R2 along the incident plane IP of each of the concave toroidal mirrors 281b to 284b is, for example, 314.4 mm.

[0206] In other respects, the structure and operation of the second optical pulse stretcher 27b are the same as those of the second optical pulse stretcher 27 in the first embodiment.

[0207] 4.4 Function of the Second Optical Pulse Stretcher

[0208] In the third embodiment, the second optical pulse stretcher 27b can also reduce the speckle contrast by the same function as the first optical pulse stretcher 17b. Since the optical path lengths of the first, second, and third delay optical systems are different, it is possible to prevent a part of the light delayed by one delay optical system from returning to its original state due to another delay optical system. Therefore, on the basis of the effect of reducing the speckle contrast by the first optical pulse stretcher 17b, the speckle contrast can be further reduced by the second optical pulse stretcher 27b.

[0209] 5. Optical Pulse Stretcher Capable of Changing the Output Beam Position

[0210] 5.1 Schematic Structure

[0211] Figure 10Schematically shows the structure of the laser device in the fourth embodiment of the present disclosure. In the fourth embodiment, the first optical pulse expander 17c disposed between the master oscillator MO and the amplifier PO is configured to be able to adjust the attitude of the parallel plate 176. In addition, the laser device in the fourth embodiment further includes a laser control unit 30, a beam divergence detector 31, and a beam pointing detector 32.

[0212] The beam divergence detector 31 includes a beam splitter 31a, a condensing optical system 31b, and an image sensor 31c. The light receiving surface of the image sensor 31c is disposed at the focal position of the condensing optical system 31b.

[0213] The beam pointing detector 32 includes a beam splitter 32a, a transfer optical system 32b, and an image sensor 32c. The light receiving surface of the image sensor 32c is disposed at a position where the light intensity distribution of the beam cross section at a specified position of the pulsed laser is imaged by the transfer optical system 32b.

[0214] 5.2 Structure of the First Optical Pulse Expander

[0215] Figure 11 FIG. is a view of the first optical pulse expander 17c observed in the -Z direction. In the fourth embodiment, an actuator 177 is mounted on the parallel plate 176.

[0216] In other respects, the structure of the fourth embodiment is the same as the structure of the first embodiment. Alternatively, in other respects, the structure of the fourth embodiment may also be the same as the structure of the second or third embodiment.

[0217] 5.3 Operation

[0218] The laser control unit 30 calculates the spot diameter of the pulsed laser based on the image data of the image sensor 31c, and calculates the beam divergence of the pulsed laser based on the spot diameter.

[0219] The laser control unit 30 calculates the center position of the light intensity distribution of the beam cross section based on the image data of the image sensor 32c, and calculates the beam pointing of the pulsed laser based on the center position.

[0220] The laser control unit 30 controls the actuator 177 based on the beam divergence and beam pointing of the pulsed laser. Thereby, the attitude of the parallel plate 176 is adjusted, and the beam position of the pulsed laser incident on the amplifier PO is adjusted.

[0221] In other respects, the operation of the fourth embodiment is the same as the operation of any one of the first to third embodiments.

[0222] 5.4 Function

[0223] According to the fourth embodiment, it is possible to optimize the beam position of the pulsed laser incident on the amplifier PO based on the beam divergence and beam pointing of the pulsed laser output from the laser device. Thereby, it is possible to optimize the dose stability, beam divergence, beam pointing, etc. of the pulsed laser.

[0224] 6. Others

[0225] Figure 12 The structure of the exposure apparatus 100 connected to the laser device 1 is schematically shown. The laser device 1 generates pulsed laser light and outputs it to the exposure apparatus 100.

[0226] In Figure 12 the exposure apparatus 100 includes an illumination optical system 41 and a projection optical system 42. The illumination optical system 41 illuminates the mask pattern on the mask stage RT with the pulsed laser light incident from the laser device 1. The projection optical system 42 reduces and projects the pulsed laser light that has passed through the mask and forms an image on an unillustrated workpiece disposed on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with a photoresist. The exposure apparatus 100 moves the mask stage RT and the workpiece stage WT synchronously and in parallel, thereby exposing the pulsed laser light reflecting the mask pattern on the workpiece. By performing the above-described exposure process, the device pattern is transferred onto the semiconductor wafer, and thus, electronic devices can be manufactured.

[0227] The above description is not restrictive but a simple illustration. Therefore, those skilled in the art will understand that modifications can be made to the embodiments of the present disclosure without departing from the claims. In addition, those skilled in the art will also understand that the embodiments of the present disclosure can be used in combination.

[0228] Unless explicitly stated, the terms used throughout this specification and the claims should be interpreted as "non-limiting" terms. For example, terms such as "comprises" or "comprising" should be interpreted as "not limited to the parts described as being comprised". The term "has" should be interpreted as "not limited to the parts described as having". In addition, the indefinite article "a" should be interpreted as meaning "at least one" or "one or more". In addition, the term "at least one of A, B, and C" should be interpreted as "A", "B", "C", "A + B", "A + C", "B + C", or "A + B + C". Furthermore, it should be interpreted as also including combinations with parts other than "A", "B", and "C".

Claims

1. A laser device having: A master oscillator that outputs pulsed laser light; A first optical pulse stretcher; and A second optical pulse stretcher disposed on the optical path of the pulsed laser output from the master oscillator, The first optical pulse stretcher having: A first delay optical system including a plurality of concave toroidal mirrors; and A first beam splitter including a first surface and a second surface, transmitting a part of the pulsed laser incident on the first surface in a first direction as a first beam, reflecting the other part in a second direction and incident on the first delay optical system, and reflecting a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction as a second beam, The first optical pulse stretcher is disposed on the optical path of the pulsed laser output from the master oscillator, The second optical pulse stretcher having: A second delay optical system including a plurality of concave toroidal mirrors; and A second beam splitter including a third surface and a fourth surface, transmitting a part of the pulsed laser incident on the third surface in a third direction as a third beam, reflecting the other part in a fourth direction and incident on the second delay optical system, and reflecting a part of the pulsed laser incident on the fourth surface from the second delay optical system in the third direction as a fourth beam, The optical path length of the delay optical path formed by the first delay optical system is different from the optical path length of the delay optical path formed by the second delay optical system.

2. The laser device according to claim 1, wherein The laser device further has an amplifier disposed on the optical path of the pulsed laser output from the master oscillator, The first optical pulse stretcher is disposed between the master oscillator and the amplifier.

3. The laser device according to claim 1, wherein The optical path length of the delay optical path formed by the first delay optical system is shorter than the optical path length of the delay optical path formed by the second delay optical system.

4. The laser device according to claim 1, wherein The first optical pulse stretcher further has an optical element for compensating for the offset of the optical axis of the pulsed laser generated when a part of the pulsed laser incident on the first surface passes through the first beam splitter.

5. The laser device according to claim 4, wherein The laser device further has: A detector for measuring the beam pointing and beam divergence of the pulsed laser after passing through the first optical pulse stretcher; And An actuator for adjusting the attitude of the optical element according to the output of the detector.

6. The laser device according to claim 5, wherein The laser device further has an amplifier disposed on the optical path of the pulsed laser output from the master oscillator, The first optical pulse stretcher is disposed between the master oscillator and the amplifier.

7. A method for manufacturing an electronic device, comprising the following steps: Generating pulsed laser light by a laser device, Outputting the pulsed laser light to an exposure device, Expose the pulsed laser on a photosensitive substrate in the exposure apparatus to manufacture an electronic device. The laser device includes: A master oscillator that outputs a pulsed laser; A first optical pulse stretcher; and A second optical pulse stretcher that is disposed on the optical path of the pulsed laser output from the master oscillator. The first optical pulse stretcher includes: A first delay optical system that includes a plurality of concave toroidal mirrors; and A first beam splitter that includes a first surface and a second surface, transmits a part of the pulsed laser incident on the first surface in a first direction as a first beam, reflects the other part in a second direction and makes it incident on the first delay optical system, and reflects a part of the pulsed laser incident on the second surface from the first delay optical system in the first direction as a second beam. The first optical pulse stretcher is disposed on the optical path of the pulsed laser output from the master oscillator. The second optical pulse stretcher includes: A second delay optical system that includes a plurality of concave toroidal mirrors; and A second beam splitter that includes a third surface and a fourth surface, transmits a part of the pulsed laser incident on the third surface in a third direction as a third beam, reflects the other part in a fourth direction and makes it incident on the second delay optical system, and reflects a part of the pulsed laser incident on the fourth surface from the second delay optical system in the third direction as a fourth beam. The optical path length of the delay optical path formed by the first delay optical system is different from the optical path length of the delay optical path formed by the second delay optical system.

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