Ultraviolet laser apparatus, method for manufacturing electronic devices, and system

Abstract

To provide an ultraviolet laser apparatus and a method for manufacturing an electronic device.SOLUTION: An ultraviolet laser apparatus includes an optical isolator disposed on an optical path between an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength and an amplifier that amplifies and outputs the pulsed laser light. The optical isolator includes a first Faraday rotator that rotates the polarization direction of the pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction by a magnetic field in a first direction, a first polarizer that is disposed to transmit the pulsed laser light output from the first Faraday rotator with a normalized transmittance of 0.9 or more, a second Faraday rotator that rotates the polarization direction of the pulsed laser light transmitted through the first polarizer by a second angle in a direction opposite to the first rotation direction by a magnetic field in a direction opposite to the first direction, and a second polarizer that is disposed to transmit the pulsed laser light output from the second Faraday rotator with a normalized transmittance of 0.9 or more.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, as semiconductor integrated circuits have become more 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 the 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. For this reason, in the laser resonator of the gas laser device, a narrowband module (Line Narrow Module: LNM) including a narrowband element (such as an etalon or a grating) may be provided to narrow the spectral linewidth. Hereinafter, a gas laser device whose spectral linewidth is narrowed is referred to as a narrowband gas laser device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] An ultraviolet laser device according to one aspect of the present disclosure comprises: an oscillation stage laser that outputs pulsed laser light with linear polarization of ultraviolet wavelength; an amplifier that amplifies and outputs the pulsed laser light; and an optical isolator disposed in the optical path between the oscillation stage laser and the amplifier, wherein the optical isolator comprises: a first Faraday rotator that rotates the polarization direction of the pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction by a magnetic field in a first direction; a first polarizer that is arranged such that the normalized transmittance to the pulsed laser light output from the first Faraday rotator is 0.9 or more; a second Faraday rotator that rotates the polarization direction of the pulsed laser light that has passed through the first polarizer by a second angle in a second rotation direction opposite to the first rotation direction by a magnetic field in a second direction opposite to the first direction; and a second polarizer that is arranged such that the normalized transmittance to the pulsed laser light output from the second Faraday rotator is 0.9 or more.

[0006] A method for manufacturing an electronic device according to another aspect of the present disclosure comprises an oscillation stage laser that outputs pulsed laser light of linear polarization in ultraviolet wavelength, an amplifier that amplifies and outputs the pulsed laser light, and an optical isolator disposed in the optical path between the oscillation stage laser and the amplifier, wherein the optical isolator includes a first Faraday rotator that rotates the polarization direction of the pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction by a magnetic field in a first direction, and a first polarizer that is disposed such that the normalized transmittance to the pulsed laser light output from the first Faraday rotator is 0.9 or more. The method includes generating laser light amplified by an amplifier using an ultraviolet laser apparatus comprising: a second Faraday rotor that rotates the polarization direction of pulsed laser light transmitted through a first polarizer by a second angle in a second rotation direction opposite to the first rotation direction by a magnetic field in a second direction opposite to the first direction; and a second polarizer that is positioned such that the normalized transmittance for pulsed laser light output from the second Faraday rotor is 0.9 or more; outputting the amplified laser light to an exposure apparatus; and exposing a photosensitive substrate to the laser light in the exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0007] Some embodiments of the present disclosure will be described below by way of example only with reference to the accompanying drawings. [Figure 1] FIG. 1 is a side view schematically showing the configuration of an ultraviolet laser device according to a comparative example. [Figure 2] FIG. 2 is a diagram showing problems of the ultraviolet laser device according to the comparative example. [Figure 3] FIG. 3 schematically shows the configuration of an optical isolator according to a comparative example for suppressing return light. [Figure 4] FIG. 4 schematically shows the configuration of an ultraviolet laser device according to Embodiment 1. [Figure 5] FIG. 5 is a cross-sectional view schematically showing the configuration of a Faraday rotor. [Figure 6] FIG. 6 is a chart showing a preferable range of a magnetic field and the thickness of a Faraday material when the wavelength of pulsed laser light is the oscillation wavelength of an ArF excimer laser. [Figure 7] FIG. 7 is a chart showing a preferable range of a magnetic field and the thickness of a Faraday material when the wavelength of pulsed laser light is the oscillation wavelength of a KrF excimer laser. [Figure 8] FIG. 8 is a graph showing the relationship between the angular difference between the transmission axis of a polarizer and the polarization direction of pulsed laser light and the extinction ratio, and a graph in which the extinction ratio is converted into normalized transmittance. [Figure 9] FIG. 9 schematically shows the configuration of an ultraviolet laser device according to Embodiment 2. [Figure 10] FIG. 10 schematically shows the configuration of an ultraviolet laser device according to Embodiment 3. [Figure 11] FIG. 11 schematically shows the configuration of an ultraviolet laser device according to Embodiment 4. [Figure 12] FIG. 12 is a top view schematically showing the configuration of an amplifier stage laser applied to Embodiment 4. [Figure 13] FIG. 13 schematically shows a configuration example of an exposure device. Embodiment

[0008] -Contents- 1. Explanation of Terms 2. Overview of the ultraviolet laser device according to the comparative example 2.1 Configuration 2.2 Operation 3. Problems 4. Embodiment 1 4.1 Configuration 4.2 Operation 4.3 Specific example of the Faraday rotator 4.4 Allowable angular difference between the transmission axis of the polarizer and the polarization direction of the laser beam 4.5 Function and effect 4.6 Modified example 5. Embodiment 2 5.1 Configuration 5.2 Operation 5.3 Function and effect 6. Embodiment 3 6.1 Configuration 6.2 Operation 6.3 Function and effect 7. Embodiment 4 7.1 Configuration 7.2 Operation 7.3 Function and effect 8. Regarding the manufacturing method of the electronic device 9. Others 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. In addition, the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0009] 1. Explanation of terms The "polarizer" refers to an optical element that separates light with a specific polarization direction (transmission axis direction) from light whose polarization direction is orthogonal thereto.

[0010] In this specification, the term "parallel," unless otherwise specified, includes the concept of approximately parallel, encompassing a range of practically acceptable angular differences that do not lose technical significance, rather than strictly parallel, unless it is clear from the context. Similarly, the terms "orthogonal" or "perpendicular," unless otherwise specified, include the concept of approximately orthogonal or approximately perpendicular, encompassing a range of practically acceptable angular differences that do not lose technical significance, rather than strictly orthogonal or perpendicular, unless it is clear from the context.

[0011] 2. Overview of the ultraviolet laser device related to the comparative example 2.1 Configuration Figure 1 is a schematic side view showing the configuration of the ultraviolet laser apparatus 20 according to the comparative example. The comparative example in this disclosure is a form that the applicant recognizes as being known only to the applicant, and is not a prior art example acknowledged by the applicant.

[0012] The ultraviolet laser apparatus 20 is an excimer laser apparatus that includes a master oscillator (MO) 22, an MO beam steering unit 24, and a power oscillator (PO) 26. The MO 22 includes a narrowband module (LNM) 30, a chamber 32, and an output coupling mirror 34.

[0013] The LNM30 includes a prism expander 36 and a grating 38 for narrowing the spectral width. The prism expander 36 and grating 38 are arranged in a Littrow configuration where the incident angle and diffraction angle coincide. The output coupling mirror 34 is a partial reflection mirror with a reflectivity of 40% to 60%. The output coupling mirror 34 is positioned together with the LNM30 to form an optical resonator.

[0014] Chamber 32 is positioned on the optical path of the optical resonator. Chamber 32 includes a pair of discharge electrodes 40a and 40b and two windows 42 and 44 through which laser light passes. The chamber 32 is filled with laser gas. The laser gas includes a rare gas, a halogen gas, and a buffer gas. The rare gas may be, for example, argon (Ar) or krypton (Kr) gas. The halogen gas may be, for example, fluorine (F2) gas. The buffer gas may be, for example, neon (Ne) gas. A voltage is applied between the discharge electrodes 40a and 40b by a power supply (not shown). The power supply may be a pulse power module (PPM) including a switch and a charging capacitor.

[0015] The MO beam steering unit 24 includes a high-reflection mirror 50 and a high-reflection mirror 52, and is positioned so that the laser light output from MO 22 is incident on PO 26.

[0016] An MO pulse energy monitor 54 is positioned between the high-reflection mirror 50 and the high-reflection mirror 52. The MO pulse energy monitor 54 includes a beam splitter (BS) 55 and an optical sensor 56. The BS 55 is positioned on the optical path of the pulsed laser light output from the MO 22, and the reflected light from the BS 55 is positioned to enter the optical sensor 56.

[0017] PO26 is an amplified laser stage that includes a rear mirror 60, a chamber 62, and an output coupling mirror 64. The rear mirror 60 and the output coupling mirror 64 form an optical resonator, and the chamber 62 is positioned on the optical path of this optical resonator.

[0018] The configuration of chamber 62 may be the same as that of chamber 32. Chamber 62 includes a pair of discharge electrodes 70a, 70b and two windows 72, 74. The chamber 62 is filled with laser gas. The rear mirror 60 may be, for example, a partial reflection mirror with a reflectivity of 50% to 90%. The output coupling mirror 64 may be a partial reflection mirror with a reflectivity of 10% to 30%.

[0019] 2.2 Operation A high-voltage pulse is applied between the discharge electrodes 40a and 40b in the chamber 32 from a power supply (not shown). When a discharge occurs between the discharge electrodes 40a and 40b in the chamber 32, the laser gas is excited, and pulsed laser light with a wavelength of ultraviolet wavelength from 150 nm to 380 nm, narrowed by an optical resonator consisting of the output coupling mirror 34 and the LNM 30, is output from the output coupling mirror 34.

[0020] The energy of the pulsed laser light output from the output coupling mirror 34 is measured by the MO pulse energy monitor 54. This pulsed laser light is also incident on the rear mirror 60 of PO26 as seed light by the MO beam steering unit 24.

[0021] At the moment the seed light that has passed through the rear mirror 60 enters the chamber 62, a high-voltage pulse is applied between the discharge electrodes 70a and 70b in the chamber 62 from a power supply (not shown). When a discharge occurs between the discharge electrodes 70a and 70b in the chamber 62, the laser gas is excited, and the seed light is amplified by a Fabry-Perot type optical resonator composed of the output coupling mirror 64 and the rear mirror 60. The amplified pulsed laser light is then output from the output coupling mirror 64 as output laser light.

[0022] 3. Challenges Figure 2 shows the problems of the ultraviolet laser apparatus 20 in the comparative example. When the reflected light from PO26 returns to MO22, the laser performance deteriorates. Here, "reflected light" refers to the sum of two types of light: MO reflected light and PO exit light. Light emitted from MO22 is incident on PO26, but since the rear mirror 60 inside PO26 is a partial reflection mirror (reflectance 50%~90%), some of the light incident on the rear mirror 60 does not go into the inside of PO26 but returns to the MO22 side. Light that is reflected by the rear mirror 60 and returns to the MO22 side without going into the chamber 62 of PO26 is called "MO reflected light".

[0023] On the other hand, light that enters PO26 from MO22 and passes through the rear mirror 60 is resonated and amplified within PO26 before being output. As mentioned above, since the rear mirror 60 in PO26 is a partial reflection mirror, some of the light that enters the chamber 62 of PO26 and is amplified returns to MO22. The light that passes through the rear mirror 60 and returns to MO22 from the light amplified in PO26 is called "PO-through light".

[0024] Reflected light can become a thermal load on components such as LNM30, potentially degrading linewidth stability and pulse energy stability. To suppress reflected light entering MO22, one method is to place an optical isolator between MO22 and PO26.

[0025] Figure 3 shows an example configuration of the optical isolator 80 in a comparative example that suppresses reflected light. The upper part of Figure 3 shows the operation of the optical isolator 80 for pulsed laser light (MO injection light: outgoing light) traveling from MO22 to PO26. The lower part of Figure 3 shows the operation of the optical isolator 80 for laser light (returning light) traveling from PO26 to MO22.

[0026] The optical isolator 80 is arranged in the following order from the MO22 side: a half-wave plate 81, a first polarizer 83, a Faraday rotor 84, and a second polarizer 88. The Faraday rotor 84 includes a Faraday material 85 and a magnet 86. In Figure 3, the rightward arrow shown in the Faraday rotor 84 represents the direction of the magnetic field created by the magnet 86. The double-headed arrows shown within the dashed circles in the figure represent the direction of the polarization plane of the pulsed laser light, i.e., the polarization direction, when the line of sight is aligned with the direction in which the pulsed laser light propagates. The same applies to Figure 4.

[0027] As shown in the upper part of Figure 3, linearly polarized pulsed laser light polarized horizontally is output from MO22. The polarization direction of the horizontally polarized pulsed laser light output from MO22 is rotated 45 degrees counterclockwise by the half-wave plate 81. The first polarizer 83 has its transmission axis parallel to the polarization direction of the pulsed laser light output from the half-wave plate 81, and the pulsed laser light output from the half-wave plate 81 passes through the first polarizer 83.

[0028] The pulsed laser light that has passed through the first polarizer 83 has its polarization direction rotated 45 degrees clockwise by the Faraday rotator 84 to which a magnetic field has been applied. As a result, the pulsed laser light output from the Faraday rotator 84 becomes horizontally polarized. The second polarizer 88 is positioned so that its transmission axis is parallel to the polarization direction of the pulsed laser light output from the Faraday rotator 84, and the pulsed laser light output from the Faraday rotator 84 passes through the second polarizer 88 before being incident on PO26.

[0029] The half-wave plate 81 adjusts the polarization direction of the pulsed laser light from MO22 so that the polarization direction of the pulsed laser light output from MO22 is the same as the polarization direction of the pulsed laser light incident on PO26. This eliminates the need to change other modules that depend on the polarization direction.

[0030] On the other hand, as shown in the lower part of Figure 3, the reflected light from PO26 passes through the second polarizer 88 with the same polarization direction as the incident light to PO26, and its polarization direction is rotated 45 degrees clockwise by the Faraday rotator 84 to which the magnetic field is applied. The polarization direction of the reflected light that has passed through the Faraday rotator 84 is perpendicular to the transmission axis of the first polarizer 83, and the reflected light is reflected by the first polarizer 83 and does not enter MO22.

[0031] The half-wave plate 81 in the comparative example optical isolator 80 has low durability at short wavelengths such as excimer lasers, making it difficult to use stably for long periods of time.

[0032] 4. Embodiment 1 4.1 Configuration Figure 4 schematically shows an example of the configuration of the ultraviolet laser apparatus 100 according to Embodiment 1. The differences between the configuration shown in Figure 4 and that of Figure 1 will be explained. The ultraviolet laser apparatus 100 differs from the configuration in Figure 1 in that an optical isolator 120 including a first Faraday rotator 110 and a second Faraday rotator 112 is arranged between MO22 and PO26. The optical isolator 120 includes the first Faraday rotator 110, a first polarizer 83, a second Faraday rotator 112, and a second polarizer 88, arranged in this order on the optical path in the direction in which the laser light travels from MO22 to PO26.

[0033] The first Faraday rotor 110 and the second Faraday rotor 112 each have magnets, and by reversing the direction of the applied magnetic field, the direction of rotation in the polarization direction is reversed. The direction of the magnetic field applied to the first Faraday rotor 110 shown in Figure 4 (indicated by the downward arrow in Figure 4) is an example of the "first direction" in this disclosure. The direction of the magnetic field applied to the second Faraday rotor 112 shown in Figure 4 (indicated by the upward arrow in Figure 4) is an example of the "second direction" in this disclosure.

[0034] Furthermore, the first Faraday rotor 110 and the second Faraday rotor 112 are selected with Faraday materials, sizes, and magnetic fields such that their respective polarization directions have a rotation angle of 45 degrees. Details regarding preferred selection conditions will be described later (Figures 5-7).

[0035] The optical isolator 120 further includes a damper 116 for terminating the backlight. The damper 116 is positioned so that the backlight reflected by the first polarizer 83 is incident on the damper 116. Other configurations may be the same as in Figure 1.

[0036] Figure 4 also shows the polarization directions of the pulsed laser light at points a, b, c, and d on the optical path between MO22 and PO26. Figure 4 shows the polarization directions at points a to d for the pulsed laser light propagating from MO22 towards PO26, and the polarization directions at points d and c for the reflected light traveling from PO26 towards MO22.

[0037] 4.2 Operation First, let's describe the pulsed laser light propagating from MO22 towards PO26. The pulsed laser light output from MO22 and polarized in a specific direction (point a) is rotated 45 degrees counterclockwise by the first Faraday rotator 110 (point b). The counterclockwise direction is an example of the "first rotation direction" in this disclosure, and 45 degrees is an example of the "first angle" in this disclosure.

[0038] The first polarizer 83 is positioned such that its transmission axis is parallel to the polarization direction of the pulsed laser light output from the first Faraday rotator 110. Therefore, the pulsed laser light whose polarization direction has been rotated by the first Faraday rotator 110 passes through the first polarizer 83 (point c).

[0039] The pulsed laser light that has passed through the first polarizer 83 is incident on the second Faraday rotator 112, and the polarization direction is rotated 45 degrees clockwise by the second Faraday rotator 112 (point d). The clockwise direction is an example of the "second rotation direction" in this disclosure, and 45 degrees is an example of the "second angle" in this disclosure. The pulsed laser light whose polarization direction has been rotated by the second Faraday rotator 112 passes through the second polarizer 88. The polarization direction at point a and point e of the pulsed laser light traveling from MO22 to PO26 are the same.

[0040] Next, we will explain the pulsed laser light returning from PO26 towards MO22. At point e in Figure 4, the polarization direction of the pulsed laser light propagating from MO22 towards PO26 is the same as the polarization direction of the pulsed laser light returning from PO26 towards MO22 (the reflected light). Therefore, the reflected light traveling from PO26 towards MO22 passes through the second polarizer 88.

[0041] The reflected light that has passed through the second polarizer 88 is then rotated 45 degrees clockwise in polarization direction by the second Faraday rotator 112 (point c). At point c, the polarization direction of the pulsed laser light propagating from MO22 to PO26 is perpendicular to the polarization direction of the pulsed laser light returning from PO26 to MO22. Therefore, the pulsed laser light returning from PO26 to MO22 is reflected by the first polarizer 83 and incident on the damper 116. The damper 116 absorbs and blocks the light reflected by the first polarizer 83.

[0042] 4.3 Specific Examples of Faraday Rotors Figure 5 is a schematic cross-sectional view showing an example configuration of the Faraday rotor 130. The Faraday rotor 130 can be applied as the first Faraday rotor 110 and the second Faraday rotor 112, respectively. The Faraday rotor 130 comprises a Faraday material 135 and a magnet 136. The Faraday material 135 is transparent at ultraviolet wavelengths and has a large Verde constant. The term "transparent" means that it is light-transmitting.

[0043] The Verde constant depends on the type of material and the wavelength. Suitable Faraday materials 135 include, for example, calcium fluoride (CaF2), synthetic quartz (SiO2), and magnesium fluoride (MgF2). The Faraday material 135 is held in the holder 137.

[0044] The magnet 136 has a hollow structure, and the Faraday material 135 is placed inside via a holder 137. The direction of the magnetic field passing through the Faraday material 135 is parallel to the direction of light propagation. The direction of rotation of the polarization plane (polarization direction) by the Faraday rotor 130 depends on the sign of the Verde constant and the direction of the applied magnetic field.

[0045] Figure 6 shows the preferred range of magnetic field and Faraday material 135 thickness when the pulsed laser wavelength is the oscillation wavelength of the ArF excimer laser. The oscillation wavelength of the ArF excimer laser includes a wavelength of approximately 193 nm. Figure 6 shows the cases where the Faraday material 135 is CaF2 and SiO2, respectively. Note that the thickness of the Faraday material 135 is evaluated by the thickness in the optical axis direction.

[0046] Figure 7 shows the preferred range of magnetic field and thickness of Faraday material 135 when the pulsed laser wavelength is the oscillation wavelength of the KrF excimer laser. The oscillation wavelength of the KrF excimer laser includes a wavelength of approximately 248 nm. Figure 7 shows the cases where Faraday material 135 is CaF2 and SiO2, respectively.

[0047] The preferred ranges shown in Figures 6 and 7 were selected based on the ease of realizing the magnetic field. The most preferred range of magnetic field corresponds to the magnetic flux density when using a strong neodymium magnet or similar. The thickness of the Faraday material 135 is calculated based on the selected material, the magnetic flux density of the magnetic field, and the Verde constant, determining the thickness at which the plane of polarization rotates by 45 degrees.

[0048] As shown in Figure 6, when the Faraday material 135 is calcium fluoride and the wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, the preferred ranges for the magnetic field applied to the Faraday rotor 130 and the thickness of the Faraday material 135 in the optical axis direction are 0.5T to 3.0T and 6mm to 40mm, respectively. More preferably, they are 0.75T to 2.9T and 10mm to 30mm, and most preferably, 0.8T to 1.5T and 15mm to 25mm. Note that numerical ranges such as "0.5T to 3.0T" indicate a range that includes the numbers before and after the "~", for example, "0.5T to 3.0T" means "0.5T or more and 3.0T or less".

[0049] When the Faraday material 135 is synthetic quartz and the wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, the preferred range for the magnetic field applied to the Faraday rotor 130 and the thickness of the Faraday material 135 in the optical axis direction is 0.5T to 3T and 3mm to 25mm. More preferably, it is 0.75T to 2.9T and 6mm to 20mm, and most preferably, it is 0.8T to 1.5T and 8mm to 15mm.

[0050] Furthermore, as shown in Figure 7, when the Faraday material is calcium fluoride and the wavelength of the pulsed laser light is the oscillation wavelength of the KrF excimer laser, the preferred range for the magnetic field applied to the Faraday rotor 130 and the thickness of the Faraday material 135 in the optical axis direction is 0.5T to 3.0T and 13mm to 83mm. More preferably, it is 0.75T to 2.9T and 20mm to 55mm, and most preferably, it is 0.8T to 1.5T and 30mm to 50mm.

[0051] When the Faraday material is synthetic quartz and the wavelength of the pulsed laser light is 248 nm, which is the oscillation wavelength of the KrF excimer laser, the preferred range for the magnetic field applied to the Faraday rotor 130 and the thickness of the Faraday material 135 in the optical axis direction is 0.5T to 3.0T and 8 mm to 53 mm. More preferably, it is 0.75T to 2.9T and 10 mm to 40 mm, and most preferably, it is 0.8T to 1.5T and 15 mm to 30 mm.

[0052] The Faraday material 135 may be divided into multiple parts, and the sum of these parts may satisfy the above thickness. The number of parts to which it is divided may be, for example, two, three, or four. It is also possible to use different types of Faraday rotors for the first Faraday rotor 110 and the second Faraday rotor 112, such as using different Faraday materials, different thicknesses in the optical axis direction, and different magnetic field magnitudes. On the other hand, using the same Faraday material, the same thickness in the optical axis direction, and the same magnetic field magnitude for the first Faraday rotor 110 and the second Faraday rotor 112 results in a configuration where the polarization planes rotate in opposite directions with the same amount of rotation (angle), which is easy to handle and a preferred configuration.

[0053] 4.4 Allowable angular difference between the polarizer's transmission axis and the polarization direction of the laser beam It is most preferable that the transmission axes of the first polarizer 83 and the second polarizer 88 are parallel to the polarization direction of the pulsed laser light incident on each polarizer. However, it is not necessary for them to be strictly parallel; an angular difference between the two is acceptable as long as it can perform the intended function in practical terms.

[0054] Figure 8 shows a graph illustrating the relationship between the angular difference between the transmission axis of the polarizer and the polarization direction of the pulsed laser light, and the extinction ratio (dB), as well as a graph showing the extinction ratio converted to normalized transmittance. The left vertical axis in Figure 8 represents the extinction ratio, and the right vertical axis represents the normalized transmittance. Normalized transmittance is a value normalized so that the transmittance is 1.0 when the angular difference is 0 degrees. For each of the first polarizer 83 that transmits pulsed laser light output from the first Faraday rotator 110 and the second polarizer 88 that transmits pulsed laser light output from the second Faraday rotator 112, if the normalized transmittance for the incident pulsed laser light is 0.9 or higher, it can function effectively for practical purposes. Therefore, according to Figure 8, the preferred allowable range for the angular difference between the transmission axis of the first polarizer 83 or the second polarizer 88 and the polarization direction of the pulsed laser light is ±17.5 degrees, where the normalized transmittance is 0.9 or higher.

[0055] 4.5 Action and Effects According to the ultraviolet laser apparatus 100 of Embodiment 1, the polarization direction of the pulsed laser light can be made the same before and after passing through the optical isolator 120 without using a half-wave plate 81 which has low durability at short wavelengths. Therefore, reflected light can be suppressed without changing modules that depend on other polarization directions.

[0056] Furthermore, according to the ultraviolet laser apparatus 100 of Embodiment 1, the pulsed laser light returning from PO26 towards MO22 is reflected by the first polarizer 83 and absorbed by the damper 116, thereby suppressing incidence onto MO22. As a result, the thermal load on MO22 is reduced, and energy stability and linewidth stability are improved compared to the comparative example configuration.

[0057] 4.6 Variations The MO pulse energy monitor 54 can be positioned either upstream or downstream of the optical isolator 120, which has the first Faraday rotor 110 and the second Faraday rotor 112 arranged in tandem. However, as shown in Figure 4, it is preferable to position it upstream of the optical isolator 120. The MO pulse energy monitor 54 is an example of an "energy monitor" in this disclosure. Furthermore, the directions of the magnetic fields applied to the first Faraday rotor 110 and the second Faraday rotor 112 do not need to be opposite to each other, and are not limited to the example shown in Figure 4. For example, it is also possible to configure the magnetic field applied to the first Faraday rotor 110 to be upward in Figure 4, and the magnetic field applied to the second Faraday rotor 112 to be downward in Figure 4.

[0058] Furthermore, while Figure 4 illustrates an example where the first Faraday rotor 110 and the second Faraday rotor 112 rotate the plane of polarization in opposite directions at the same rotation angle (45 degrees), the angle difference between the rotation angle in the polarization direction by the first Faraday rotor 110 and the rotation angle in the polarization direction by the second Faraday rotor 112 is not limited to the same angle in opposite directions. A difference in angle between the two is acceptable as long as it can perform the intended function in practical terms. According to Figure 8, the angle difference between the rotation angle in the first rotation direction by the first Faraday rotor 110 and the rotation angle in the second rotation direction (opposite to the first rotation direction) by the second Faraday rotor 112 is acceptable within 17.5 degrees.

[0059] The rotation angle in the first rotation direction by the first Faraday rotor 110 may be within 45 degrees ± 17.5 degrees, and similarly, the rotation angle in the second rotation direction by the second Faraday rotor 112 may be within 45 degrees ± 17.5 degrees. The polarization direction of the pulsed laser light that passes through the first Faraday rotor 110 and is incident on the first polarizer 83 and the polarization direction of the pulsed laser light that returns from PO26 and passes through the second Faraday rotor 112 and is incident on the first polarizer 83 intersect at an angle of 90 degrees ± 17.5 degrees, so that the reflected light is reflected by the first polarizer 83 and incident on MO22 is suppressed.

[0060] 5. Embodiment 2 5.1 Configuration Figure 9 schematically shows the configuration of the ultraviolet laser apparatus 102 according to Embodiment 2. The differences between the configuration shown in Figure 9 and that shown in Figure 4 will be explained. The ultraviolet laser apparatus 102 shown in Figure 9 differs from the configuration shown in Figure 4 in that a two-axis adjustable parallel planar substrate 202 and a two-axis adjustable high-reflectivity mirror 52 are arranged in the optical path between the second polarizer 88 and PO26. The parallel planar substrate 202 is held in a two-axis angle adjustment holder 204, which allows angle adjustment using each of the two orthogonal axes as the axis of rotation.

[0061] The parallel-plane substrate 202 is positioned in the optical path between the second polarizer 88 and the high-reflectivity mirror 52. The parallel-plane substrate 202 may be a calcium fluoride substrate. The two-axis angle adjustment holder 204 may be, for example, a holder that can adjust the angle using an axis perpendicular to the plane of paper in Figure 9 and an axis parallel to the substrate surface of the parallel-plane substrate 202 and the plane of paper in Figure 9 as axes of rotation.

[0062] The high-reflection mirror 52 is held in a two-axis angle adjustment holder 208, which allows for angle adjustment using each of two orthogonal axes as the axis of rotation. The two-axis angle adjustment holder 208 may be, for example, a holder that allows for angle adjustment using an axis perpendicular to the plane of paper in Figure 9 and an axis parallel to the reflective surface of the high-reflection mirror 52 and the plane of paper in Figure 9 as the axes of rotation.

[0063] 5.2 Operation The optical axis is adjusted by adjusting a two-axis adjustable parallel planar substrate 202 and a two-axis adjustable high-reflection mirror 52 so that the pulsed laser light from MO22 is incident on PO26 most efficiently.

[0064] The two-axis adjustable parallel planar substrate 202 is adjusted so that the pulsed laser beam from MO22 is incident on PO26 most efficiently by shifting it parallel to the direction of propagation.

[0065] The two-axis adjustable high-reflection mirror 52 is adjusted to ensure that the pulsed laser light from MO22 is incident on PO26 most efficiently by changing the angle at which the pulsed laser light is incident on PO26.

[0066] The two-axis angle adjustment holder 204 and the two-axis angle adjustment holder 208 are examples of the "optical axis adjustment mechanism" in this disclosure. A configuration comprising both a two-axis adjustable parallel planar substrate 202 and a two-axis adjustable high-reflection mirror 52 is preferred, but a configuration comprising only one of these is also possible.

[0067] 5.3 Action and Effects According to Embodiment 2, the same effects as in Embodiment 1 can be obtained. Furthermore, according to Embodiment 2, adjusting the optical axis of the injected light incident on PO26 becomes easier compared to Embodiment 1.

[0068] 6. Embodiment 3 6.1 Configuration Figure 10 schematically shows the configuration of the ultraviolet laser apparatus 103 according to Embodiment 3. The differences between the configuration shown in Figure 10 and that shown in Figure 4 will be explained. The ultraviolet laser apparatus 103 shown in Figure 10 includes an ultraviolet solid-state laser apparatus 232 as the oscillation stage laser instead of MO22 in Figure 4, and an excimer amplifier 236 instead of PO26. Other configurations may be the same as those shown in Figure 4.

[0069] The ultraviolet solid-state laser device 232 outputs, for example, the fourth, fifth, or sixth harmonics (in the range of wavelengths from 150 nm to 380 nm) of a solid-state laser whose fundamental wave is in the near-infrared band (wavelengths from 780 nm to 2500 nm). For example, the ultraviolet solid-state laser device 232 outputs a seed light with a wavelength of approximately 193 nm, and is positioned so that the seed light is incident on the excimer amplifier 236.

[0070] As an example, the ultraviolet solid-state laser apparatus 232 may include a semiconductor laser system, a titanium-sapphire amplifier, and a wavelength conversion system. The semiconductor laser system may include a distributed feedback (DFB) semiconductor laser that outputs CW laser light with a wavelength of approximately 773.6 nm, and a semiconductor optical amplifier (SOA) that pulses the CW laser light. The wavelength conversion system includes a plurality of nonlinear optical crystals and converts the wavelength of the incident pulsed laser light to output pulsed laser light at the fourth harmonic. The wavelength conversion system includes, for example, an LBO crystal and a KBBF crystal. The LBO crystal is a nonlinear optical crystal represented by the chemical formula LiB3O5. The KBBF crystal is a nonlinear optical crystal represented by the chemical formula KBe2BO3F2.

[0071] The excimer amplifier 236 includes a chamber 242, a convex cylindrical mirror 244, and a concave cylindrical mirror 246.

[0072] Chamber 242 includes a pair of discharge electrodes 250a and 250b, and two windows 252 and 254 through which laser light passes. The discharge electrodes 250a and 250b are positioned opposite each other across a discharge space 256. The space between the discharge electrodes 250a and 250b constitutes the discharge space 256. The direction in which the discharge electrodes 250a and 250b face each other across the discharge space 256 corresponds to the discharge direction. Chamber 242 is filled with a laser gas similar to the laser gas described in Figure 4.

[0073] The convex surface of the convex cylindrical mirror 244 and the concave surface of the concave cylindrical mirror 246 are coated with a highly reflective film for a wavelength of approximately 193 nm.

[0074] The convex cylindrical mirror 244 and the concave cylindrical mirror 246 are positioned so that seed light from the ultraviolet solid-state laser device 232 is beam-expanded and amplified in the direction of the discharge by passing through the discharge space 256 of the excimer amplifier 236 three times.

[0075] 6.2 Operation The seed light output from the ultraviolet solid-state laser device 232 passes through the optical isolator 120 and is incident on the excimer amplifier 236. The seed light with a wavelength of approximately 193.4 nm incident on the excimer amplifier 236 is reflected by the convex cylindrical mirror 244 and the concave cylindrical mirror 246, passing through the discharge space 256 between the discharge electrodes 250a and 250b three times. As a result, the beam of the seed light is expanded and amplified. The excimer amplifier 236 is an example of a "multipath amplifier" in this disclosure. Various multipath amplifiers are applicable, not limited to the 3-pass excimer amplifier 236.

[0076] The operation of the optical isolator 120 is the same as in Embodiment 1 described in Figure 4. The optical isolator 120 suppresses the incidence of amplified spontaneous emission (ASE) and other light generated by the excimer amplifier 236 into the ultraviolet solid-state laser device 232.

[0077] 6.3 Action and Effects According to the ultraviolet laser apparatus 103 of Embodiment 3, the polarization direction can be made the same before and after passing through the optical isolator 120 without using a half-wave plate 81 which has low durability at short wavelengths. Therefore, reflected light can be suppressed without changing modules that depend on other polarization directions.

[0078] According to the ultraviolet laser apparatus 103 of Embodiment 3, the light returning from the excimer amplifier 236 towards the ultraviolet solid-state laser apparatus 232 does not enter the ultraviolet solid-state laser apparatus 232. As a result, the thermal load on the ultraviolet solid-state laser apparatus 232 is reduced, and energy stability and linewidth stability are improved compared to the comparative example configuration.

[0079] 7. Embodiment 4 7.1 Configuration Figure 11 schematically shows the configuration of the ultraviolet laser apparatus 104 according to Embodiment 4. The differences between the configuration shown in Figure 11 and that in Figure 4 will be explained. The ultraviolet laser apparatus 104 according to Embodiment 4 differs from the configuration of Embodiment 1 in the configuration of the amplification stage laser and the configuration of the high-reflection mirror that introduces the laser light from MO22 to the amplification stage laser.

[0080] The amplification stage laser of Embodiment 1 shown in Figure 4 is a PO26 having a Fabry-Perot type optical resonator composed of a rear mirror 60 and an output coupling mirror 64, whereas the amplification stage laser of Embodiment 4 shown in Figure 11 is a PO266 having a ring resonator 270.

[0081] Figure 12 is a schematic top view showing the configuration of PO266 applied to Embodiment 4. The ring resonator 270 is composed of a high-reflection mirror 284, a high-reflection mirror 285, a high-reflection mirror 286, and a partial-reflection mirror 290.

[0082] In the ultraviolet laser device 104, a high-reflection mirror 283 is positioned to introduce the laser light output from MO22 and reflected by the high-reflection mirror 50 and high-reflection mirror 52 into the ring resonator 270. The high-reflection mirror 283 is positioned in the optical path between the high-reflection mirror 52 and the partial-reflection mirror 290 so that the laser light reflected by the high-reflection mirror 52 is incident on the partial-reflection mirror 290.

[0083] 7.2 Operation The laser light emitted from MO22 is sequentially reflected by the high-reflection mirror 50, high-reflection mirror 52, and high-reflection mirror 283, and then incident on the ring resonator 270 via the partial-reflection mirror 290.

[0084] The laser light that passes through the partial reflection mirror 290 is reflected by the high reflection mirror 284, then incident into the chamber 62 where it is amplified, and then reflected again by the high reflection mirrors 285 and 286, before being incident into the chamber 62 again where it is amplified. The laser light output from the chamber 62 is partially transmitted by the partial reflection mirror 290, and the other part is reflected and amplified again in the ring resonator 270.

[0085] The amplified pulsed laser light that has passed through the partial reflection mirror 290 is output from the ultraviolet laser device 104.

[0086] The optical isolator 120 suppresses the incidence of reflected light from PO266 onto MO22. The operation of the optical isolator 120 is the same as in Embodiment 1 described in Figure 4.

[0087] 7.3 Action and Effects According to the ultraviolet laser device 104 of Embodiment 4, the same effects as in Embodiment 1 can be obtained.

[0088] 8. Regarding the manufacturing method of electronic devices Figure 13 schematically shows an example configuration of the exposure apparatus 300. The exposure apparatus 300 includes an illumination optical system 304 and a projection optical system 306. The illumination optical system 304 illuminates the reticle pattern of a reticle (not shown) placed on the reticle stage RT with laser light incident from an ultraviolet laser device 100. The projection optical system 306 reduces and projects the laser light that has passed through the reticle onto a workpiece (not shown) placed on the workpiece table WT to form an image. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0089] The exposure apparatus 300 exposes the workpiece to a laser beam 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. Instead of the ultraviolet laser apparatus 100, the ultraviolet laser apparatus 102, 103, or 104 described in Embodiments 2 to 4 may be used to generate the laser beam.

[0090] 9. Other 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 the embodiments of this disclosure without departing from the claims. It will also be apparent to those skilled in the art that the embodiments of this disclosure can be used in combination.

[0091] Terms used in this specification and throughout the claims should be interpreted as "non-limiting" unless otherwise specified. For example, terms such as "includes," "have," "equip," and "possess" should be interpreted as "not excluding the existence of components other than those described." Also, the modifier "one" should be interpreted as "at least one" or "one or more." Furthermore, 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." In addition, it should be interpreted as including combinations of these with anything other than "A," "B," and "C."

Claims

1. It is an ultraviolet laser device, An oscillator stage laser that outputs linearly polarized pulsed laser light at ultraviolet wavelengths, An amplifier that includes a resonator and amplifies and outputs the pulsed laser light, The system comprises an optical isolator positioned in the optical path between the oscillation stage laser and the amplifier, The aforementioned optical isolator, A first Faraday rotator rotates the polarization direction of pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction using a magnetic field in a first direction, A first polarizer is arranged such that the normalized transmittance to the pulsed laser light output from the first Faraday rotator is 0.9 or more, The system comprises a second Faraday rotor that rotates the polarization direction of pulsed laser light transmitted through the first polarizer by a second rotation direction opposite to the first rotation direction by a magnetic field in a second direction opposite to the first direction, The angle difference between the first angle and the second angle is within 17.5 degrees. The first angle and the second angle are each within 45 degrees ± 17.5 degrees. The angular difference between the polarization direction of the pulsed laser light output from the first Faraday rotor and the transmission axis of the first polarizer is within 17.5 degrees. The polarization direction of the pulsed laser light traveling from the oscillation stage laser towards the amplifier when it is incident on the first polarizer, and the polarization direction of the pulsed laser light returning from the amplifier towards the oscillation stage laser when it passes through the second Faraday rotor and is incident on the first polarizer, intersect at an angle of 90 degrees ± 17.5 degrees. The pulsed laser light that passes through the second Faraday rotator and enters the first polarizer is reflected by the first polarizer. Ultraviolet laser device.

2. The ultraviolet laser apparatus according to claim 1, The angular difference between the polarization direction of the pulsed laser light output from the first Faraday rotor and the transmission axis of the first polarizer is within 17.5 degrees. Ultraviolet laser device.

3. The ultraviolet laser apparatus according to claim 1, The magnetic flux density of the magnetic field applied to the first Faraday rotor and the second Faraday rotor is 0.5 T or more and 3.0 T or less. Ultraviolet laser device.

4. The ultraviolet laser apparatus according to claim 3, The wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, The Faraday material contained in the first Faraday rotor and the second Faraday rotor is calcium fluoride. The thickness of the Faraday material in the optical axis direction is 6 mm or more and 40 mm or less. Ultraviolet laser device.

5. The ultraviolet laser apparatus according to claim 3, The wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, The Faraday material contained in the first Faraday rotor and the second Faraday rotor is synthetic quartz. The thickness of the Faraday material in the optical axis direction is 3 mm or more and 25 mm or less. Ultraviolet laser device.

6. The ultraviolet laser apparatus according to claim 3, The wavelength of the pulsed laser light is the oscillation wavelength of the KrF excimer laser. The Faraday material contained in the first Faraday rotor and the second Faraday rotor is calcium fluoride. The thickness of the Faraday material in the optical axis direction is 13 mm or more and 83 mm or less. Ultraviolet laser device.

7. The ultraviolet laser apparatus according to claim 3, The wavelength of the pulsed laser light is the oscillation wavelength of the KrF excimer laser. The Faraday material contained in the first Faraday rotor and the second Faraday rotor is synthetic quartz. The thickness of the Faraday material in the optical axis direction is 8 mm or more and 53 mm or less. Ultraviolet laser device.

8. The ultraviolet laser apparatus according to claim 1, The Faraday material contained in the first Faraday rotor and the second Faraday rotor, respectively, is composed of a plurality of divided materials. Ultraviolet laser device.

9. The ultraviolet laser apparatus according to claim 1, Between the second Faraday rotor and the amplifier, there is a first optical axis adjustment mechanism including a first adjustment mechanism capable of adjusting at least two axes, The first optical axis adjustment mechanism comprises a parallel planar substrate that is adjustable in two axes by the first adjustment mechanism, and which transmits the pulsed laser light. Ultraviolet laser device.

10. The ultraviolet laser apparatus according to claim 1, Between the second Faraday rotor and the amplifier, there is a second optical axis adjustment mechanism, which includes a second adjustment mechanism capable of adjusting at least two axes. The second optical axis adjustment mechanism includes a high-reflection mirror that can be adjusted in two axes by the second adjustment mechanism. Ultraviolet laser device.

11. The ultraviolet laser apparatus according to claim 1, Each of the oscillating laser stage and the amplifier is equipped with a chamber filled with laser gas. Ultraviolet laser device.

12. The ultraviolet laser apparatus according to claim 1, The oscillation stage laser is an ultraviolet solid-state laser. Ultraviolet laser device.

13. The ultraviolet laser apparatus according to claim 1, The amplifier further comprises a damper that absorbs light reflected by the first polarizer via the second Faraday rotor. Ultraviolet laser device.

14. The ultraviolet laser apparatus according to claim 1, An energy monitor for measuring the pulse energy of the oscillation stage laser is provided between the oscillation stage laser and the optical isolator. Ultraviolet laser device.

15. A method for manufacturing electronic devices, An oscillator stage laser that outputs linearly polarized pulsed laser light at ultraviolet wavelengths, An amplifier that includes a resonator and amplifies and outputs the pulsed laser light, The system comprises an optical isolator positioned in the optical path between the oscillation stage laser and the amplifier, The aforementioned optical isolator, A first Faraday rotator rotates the polarization direction of pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction using a magnetic field in a first direction, A first polarizer is arranged such that the normalized transmittance to the pulsed laser light output from the first Faraday rotator is 0.9 or more, The system comprises a second Faraday rotor that rotates the polarization direction of pulsed laser light transmitted through the first polarizer by a second rotation direction opposite to the first rotation direction by a magnetic field in a second direction opposite to the first direction, The angle difference between the first angle and the second angle is within 17.5 degrees. The first angle and the second angle are each within 45 degrees ± 17.5 degrees. The angular difference between the polarization direction of the pulsed laser light output from the first Faraday rotor and the transmission axis of the first polarizer is within 17.5 degrees. The polarization direction of the pulsed laser light traveling from the oscillation stage laser towards the amplifier when it is incident on the first polarizer, and the polarization direction of the pulsed laser light returning from the amplifier towards the oscillation stage laser when it passes through the second Faraday rotor and is incident on the first polarizer, intersect at an angle of 90 degrees ± 17.5 degrees. The pulsed laser light that passes through the second Faraday rotator and is incident on the first polarizer is reflected by the first polarizer. Using this ultraviolet laser device, the laser light is amplified by the amplifier. The amplified laser light is output to the exposure apparatus. To manufacture an electronic device, the laser light is exposed onto a photosensitive substrate within the exposure apparatus. A method for manufacturing electronic devices, including

16. An oscillator stage laser that outputs linearly polarized pulsed laser light at ultraviolet wavelengths, An amplifier that includes a resonator and amplifies and outputs the pulsed laser light, The system comprises an optical isolator positioned in the optical path between the oscillation stage laser and the amplifier, The aforementioned optical isolator, A first Faraday rotator rotates the polarization direction of pulsed laser light output from the oscillation stage laser by a first angle in a first rotation direction using a magnetic field in a first direction, A first polarizer is arranged such that the normalized transmittance to the pulsed laser light output from the first Faraday rotator is 0.9 or more, A second Faraday rotor rotates the polarization direction of pulsed laser light transmitted through the first polarizer by a second rotation direction opposite to the first rotation direction by a magnetic field in a second direction opposite to the first direction, and The angle difference between the first angle and the second angle is within 17.5 degrees. The first angle and the second angle are each within 45 degrees ± 17.5 degrees. The angular difference between the polarization direction of the pulsed laser light output from the first Faraday rotor and the transmission axis of the first polarizer is within 17.5 degrees. The polarization direction when the pulsed laser light traveling from the oscillation stage laser toward the amplifier is incident on the first polarizer, The pulsed laser light returning from the amplifier towards the oscillation stage laser intersects the polarization direction of the first polarizer at an angle of 90 degrees ± 17.5 degrees. In an ultraviolet laser device, pulsed laser light that passes through the second Faraday rotor and is incident on the first polarizer is reflected by the first polarizer. An exposure apparatus for exposing a photosensitive substrate to pulsed laser light amplified by the aforementioned amplifier, A system that includes this.

17. The system according to claim 16, The angular difference between the polarization direction of the pulsed laser light output from the first Faraday rotor and the transmission axis of the first polarizer is within 17.5 degrees. system.

18. The system according to claim 16, The magnetic flux density of the magnetic field applied to the first Faraday rotor and the second Faraday rotor is 0.5 T or more and 3.0 T or less. The wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, The Faraday material contained in the first Faraday rotor and the second Faraday rotor is calcium fluoride. The thickness of the Faraday material in the optical axis direction is 6 mm or more and 40 mm or less. system.

19. The system according to claim 16, The magnetic flux density of the magnetic field applied to the first Faraday rotor and the second Faraday rotor is 0.5 T or more and 3.0 T or less. The wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser, The Faraday material contained in the first Faraday rotor and the second Faraday rotor is synthetic quartz. The thickness of the Faraday material in the optical axis direction is 3 mm or more and 25 mm or less. system.

20. The system according to claim 16, Between the second Faraday rotor and the amplifier, there is a first optical axis adjustment mechanism including a first adjustment mechanism capable of adjusting at least two axes, The first optical axis adjustment mechanism comprises a parallel planar substrate that is adjustable in two axes by the first adjustment mechanism, and which transmits the pulsed laser light. system.

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