Ultraviolet laser apparatus, method and system for manufacturing electronic device

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 apparatus and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, semiconductor exposure devices are required to improve their resolution in accordance with the miniaturization and high integration of semiconductor integrated circuits. For this reason, the wavelength of light emitted from the exposure light source is being shortened. For example, as gas laser devices for exposure, KrF excimer laser devices that output laser light with a wavelength of about 248 nm and ArF excimer laser devices that output laser light with a wavelength of about 193 nm are used.

[0003] The spectral line width of the spontaneous oscillation light of the KrF excimer laser device and the ArF excimer laser device is as wide as 350 to 400 pm. Therefore, if a projection lens is made of a material that transmits ultraviolet light such as KrF and ArF laser light, chromatic aberration may occur. As a result, the resolution may decrease. Therefore, it is necessary to narrow the spectral line width of the laser light output from the gas laser device to a level where the chromatic aberration can be ignored. Therefore, in order to narrow the spectral line width, a line narrow module (LNM) including a line narrowing element (such as an etalon or grating) may be provided in the laser resonator of the gas laser device. Hereinafter, a gas laser device in which the spectral line width is narrowed is referred to as a line narrowing gas laser device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-62006 A [Patent Document 2] Japanese Patent Application Laid-Open No. 61-141189 [Patent Document 3] Summary of Special Publication No. 2011-517066

[0005] An ultraviolet laser device according to one aspect of the present disclosure includes an oscillation-stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength, an amplifier that amplifies and outputs the pulsed laser light, and an optical isolator arranged on an 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, a first polarizer that is arranged so that the normalized transmittance for 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 transmitted 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 so that the normalized transmittance for the pulsed laser light output from the second Faraday rotator is 0.9 or more.

[0006] A manufacturing method for an electronic device according to another aspect of the present disclosure includes an oscillation-stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength, an amplifier that amplifies and outputs the pulsed laser light, and an optical isolator arranged on an optical path between the oscillation-stage laser and the amplifier, the optical isolator including 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 arranged so that the normalized transmittance for the pulsed laser light output from the first Faraday rotator is 0.9 or more. the first polarizer being arranged so that the normalized transmittance of the pulsed laser light output from the second Faraday rotator is 0.9 or more; generating laser light amplified by an amplifier using an ultraviolet laser apparatus including: 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 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 so that the normalized transmittance of the pulsed laser light output from the second Faraday rotator is 0.9 or more; outputting the amplified laser light to an exposure apparatus; and exposing the laser light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device. [Brief description of the drawings]

[0007] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings. [Figure 1] FIG. 1 is a side view that illustrates a schematic configuration of an ultraviolet laser device according to a comparative example. [Diagram 2] FIG. 2 is a diagram showing a problem with the ultraviolet laser device according to the comparative example. [Diagram 3] FIG. 3 shows a schematic configuration of an optical isolator according to a comparative example that suppresses return light. [Figure 4] FIG. 4 shows a schematic configuration of the ultraviolet laser device according to the first embodiment. [Diagram 5] FIG. 5 is a cross-sectional view that illustrates a schematic configuration of a Faraday rotator. [Figure 6] FIG. 6 is a chart showing preferred ranges of the magnetic field and the thickness of the Faraday material when the wavelength of the pulsed laser light is the oscillation wavelength of an ArF excimer laser. [Figure 7] FIG. 7 is a chart showing preferred ranges of the magnetic field and the thickness of the Faraday material when the wavelength of the pulsed laser light is the oscillation wavelength of a KrF excimer laser. [Figure 8] FIG. 8 is a graph showing the relationship between the extinction ratio and the angular difference between the transmission axis of a polarizer and the polarization direction of a pulsed laser beam, and a graph in which the extinction ratio is converted into a normalized transmittance. [Figure 9] FIG. 9 shows a schematic configuration of an ultraviolet laser device according to the second embodiment. [Figure 10] FIG. 10 shows a schematic configuration of an ultraviolet laser device according to the third embodiment. [Figure 11] FIG. 11 shows a schematic configuration of an ultraviolet laser device according to the fourth embodiment. [Figure 12] FIG. 12 is a top view that illustrates a schematic configuration of an amplification-stage laser that is applied to the fourth embodiment. [Figure 13] FIG. 13 shows a schematic configuration example of an exposure apparatus. Embodiment

[0008] -table of contents- 1. Explanation of terms 2. Overview of the ultraviolet laser device according to the comparative example 2.1 Configuration 2.2 Operation 3. Challenges 4. Embodiment 1 4.1 Configuration 4.2 Operation 4.3 Examples of Faraday rotators 4.4 Permissible angle difference between the transmission axis of the polarizer and the polarization direction of the laser light 4.5 Actions and Effects 4.6 Variations 5. Embodiment 2 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 6. Embodiment 3 6.1 Configuration 6.2 Operation 6.3 Actions and Effects 7. Embodiment 4 7.1 Configuration 7.2 Operation 7.3 Actions and Effects 8. Manufacturing methods for electronic devices 9.Other Hereinafter, the 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 contents of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and duplicated explanations will be omitted.

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

[0010] In this specification, the term "parallel" includes not only strictly parallel but also the concept of approximately parallel including the range of angle difference that is practically acceptable without losing technical meaning, unless otherwise specified, unless otherwise clear from the context. Similarly, in this specification, the terms "orthogonal" and "perpendicular" include not only strictly orthogonal or perpendicular but also the concept of approximately orthogonal or approximately perpendicular including the range of angle difference that is practically acceptable without losing technical meaning, unless otherwise specified, unless otherwise clear from the context.

[0011] 2. Overview of the ultraviolet laser device according to the comparative example 2.1 Configuration 1 is a side view showing a schematic configuration of an ultraviolet laser device 20 according to a comparative example. The comparative example of the present disclosure is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant recognizes.

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

[0013] The LNM 30 includes a prism expander 36 for narrowing the spectral width, and a grating 38. The prism expander 36 and the grating 38 are arranged in a Littrow configuration in which the angle of incidence and the angle of diffraction match. The output coupling mirror 34 is a partial reflection mirror with a reflectance of 40% to 60%. The output coupling mirror 34 is arranged so as to configure an optical resonator together with the LNM 30.

[0014] The chamber 32 is disposed on the optical path of the optical resonator. The chamber 32 includes a pair of discharge electrodes 40a, 40b and two windows 42, 44 through which the laser light passes. The chamber 32 is filled with a 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, 40b by a power source (not shown). The power source 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 disposed so that the laser light output from the MO 22 is incident on the PO .

[0016] Between high-reflection mirror 50 and high-reflection mirror 52, MO pulse energy monitor 54 is disposed. MO pulse energy monitor 54 includes a beam splitter (BS) 55 and an optical sensor 56. BS 55 is disposed on the optical path of the pulsed laser light output from MO 22, and is disposed so that reflected light of BS 55 is incident on optical sensor 56.

[0017] The PO 26 is an amplification stage laser including 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 disposed on the optical path of this optical resonator.

[0018] The configuration of the chamber 62 may be similar to that of the chamber 32. The 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 reflectance of 50% to 90%. The output coupling mirror 64 may be a partial reflection mirror with a reflectance of 10% to 30%.

[0019] 2.2 Operation A high voltage pulse is applied between the discharge electrodes 40a, 40b in the chamber 32 from a power source (not shown). When a discharge occurs between the discharge electrodes 40a, 40b in the chamber 32, the laser gas is excited, and pulsed laser light with an ultraviolet wavelength of 150 nm to 380 nm, which has been narrowed by the optical resonator formed by 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 an MO pulse energy monitor 54. In addition, this pulsed laser light is made incident on a rear mirror 60 of the PO 26 by the MO beam steering unit 24 as a seed beam.

[0021] At the timing when the seed light transmitted through the rear mirror 60 enters the chamber 62, a high-voltage pulse is applied between the discharge electrodes 70a, 70b in the chamber 62 from a power source (not shown). When a discharge occurs between the discharge electrodes 70a, 70b in the chamber 62, the laser gas is excited, and the seed light is amplified by a Fabry-Perot type optical resonator constituted by the output coupling mirror 64 and the rear mirror 60, and the amplified pulsed laser light is output from the output coupling mirror 64 as output laser light.

[0022] 3. Challenges FIG. 2 is a diagram showing a problem of the ultraviolet laser device 20 according to the comparative example. When the return light from the PO26 returns to the MO22, the laser performance deteriorates. The "return light" here refers to the sum of two types of light: the MO return light and the PO escape light. The light emitted from the MO22 is incident on the PO26, but since the rear mirror 60 in the PO26 is a partial reflection mirror (reflectance 50% to 90%), a part of the light incident on the rear mirror 60 does not go inside the PO26 but returns directly to the MO22 side. The light that does not go into the chamber 62 of the PO26 and is reflected by the rear mirror 60 and returns to the MO22 side is called "MO return light".

[0023] On the other hand, light that is incident on PO26 from MO22 and passes through rear mirror 60 is resonated and amplified within PO26 and then output. As described above, because rear mirror 60 within PO26 is a partial reflection mirror, a portion of the light that is incident on chamber 62 of PO26 and amplified returns to MO22. The light that is amplified in PO26 and passes through rear mirror 60 and returns to MO22 is called "PO-leaving light."

[0024] The returning light becomes a thermal load on the LNM 30 and the like, and can cause deterioration in the stability of the linewidth, the stability of the pulse energy, etc. In order to suppress the returning light entering the MO 22, an optical isolator can be placed between the MO 22 and the PO 26.

[0025] Fig. 3 shows a configuration example of an optical isolator 80 according to a comparative example that suppresses return light. The upper part of Fig. 3 shows the operation of the optical isolator 80 with respect to pulsed laser light (MO injection light: outgoing light) traveling from the MO 22 to the PO 26. The lower part of Fig. 3 shows the operation of the optical isolator 80 with respect to laser light (return light) traveling from the PO 26 to the MO 22.

[0026] In the optical isolator 80, a half-wave plate 81, a first polarizer 83, a Faraday rotator 84, and a second polarizer 88 are arranged in this order from the MO22 side. The Faraday rotator 84 includes a Faraday material 85 and a magnet 86. In FIG. 3, the right-pointing arrow shown in the Faraday rotator 84 indicates the direction of the magnetic field generated by the magnet 86. The double-pointing arrow shown in the dashed circle in the figure indicates the direction of the polarization plane of the pulsed laser light when the line of sight is aligned in the direction in which the pulsed laser light travels, that is, the polarization direction. The same applies to FIG. 4.

[0027] 3, a linearly polarized pulsed laser beam that is horizontally polarized is output from the MO 22. The polarization direction of the horizontally polarized pulsed laser beam output from the MO 22 is rotated 45 degrees counterclockwise by the half-wave plate 81. The first polarizer 83 is disposed such that its transmission axis is parallel to the polarization direction of the pulsed laser beam output from the half-wave plate 81, and the pulsed laser beam output from the half-wave plate 81 passes through the first polarizer 83.

[0028] The polarization direction of the pulsed laser light transmitted through the first polarizer 83 is rotated 45 degrees clockwise by the Faraday rotator 84 to which a magnetic field is applied. As a result, the pulsed laser light output from the Faraday rotator 84 becomes horizontally polarized. The second polarizer 88 is disposed such 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 is transmitted through the second polarizer 88 and then enters the PO26.

[0029] The half-wave plate 81 adjusts the polarization direction of the pulsed laser light from the MO 22 so that the polarization direction of the pulsed laser light output from the MO 22 is the same as the polarization direction of the pulsed laser light incident on the PO 26. This eliminates the need to change other modules that depend on the polarization direction.

[0030] 3, the return light from PO26 passes through the second polarizer 88 in the same polarization direction as the light incident on PO26, and the polarization direction is rotated 45 degrees clockwise by the Faraday rotator 84 to which a magnetic field is applied. The polarization direction of the return light that passes through the Faraday rotator 84 is perpendicular to the transmission axis of the first polarizer 83, and the return light is reflected by the first polarizer 83 and does not enter MO22.

[0031] The half-wave plate 81 in the optical isolator 80 according to the comparative example has low durability at short wavelengths such as those of an excimer laser, and it is difficult to use it stably for a long period of time.

[0032] 4. Embodiment 1 4.1 Configuration FIG. 4 is a schematic diagram of an example of the configuration of the ultraviolet laser device 100 according to the first embodiment. The configuration shown in FIG. 4 will be described with respect to differences from FIG. 1. The ultraviolet laser device 100 differs from the configuration shown in FIG. 1 in that an optical isolator 120 including a first Faraday rotator 110 and a second Faraday rotator 112 is disposed between the MO22 and the PO26. The optical isolator 120 includes the first Faraday rotator 110, the first polarizer 83, the second Faraday rotator 112, and the second polarizer 88, which are disposed in this order on the optical path in the direction in which the laser light travels from the MO22 to the PO26.

[0033] The first Faraday rotator 110 and the second Faraday rotator 112 each have a magnet, and the direction of the applied magnetic field is reversed to rotate the polarization direction in the opposite direction. The direction of the magnetic field applied to the first Faraday rotator 110 shown in FIG. 4 (the direction indicated by the downward arrow in FIG. 4) is an example of the "first direction" in the present disclosure. The direction of the magnetic field applied to the second Faraday rotator 112 shown in FIG. 4 (the direction indicated by the upward arrow in FIG. 4) is an example of the "second direction" in the present disclosure.

[0034] Furthermore, the Faraday material, size, and magnetic field of the first Faraday rotator 110 and the second Faraday rotator 112 are selected so that the rotation angle of the polarization direction of each is 45 degrees. The details of the preferable selection conditions will be described later (FIGS. 5 to 7).

[0035] The optical isolator 120 further includes a damper 116 for terminating the return light. The damper 116 is disposed so that the return light reflected by the first polarizer 83 enters the damper 116. Other configurations may be similar to those in FIG.

[0036] Fig. 4 also shows the polarization direction of the pulsed laser light at points a, b, c, and d on the optical path between MO22 and PO26. Fig. 4 shows the polarization direction of the pulsed laser light propagating from MO22 to PO26 at points a to d, and the polarization direction of the return light traveling from PO26 to MO22 at points d and c.

[0037] 4.2 Operation First, the pulsed laser light propagating from MO 22 to PO 26 will be described. The pulsed laser light (point a) output from MO 22 and polarized in a specific direction has its polarization direction 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 so that its transmission axis is parallel to the polarization direction of the pulsed laser light output from the first Faraday rotator 110, so that 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 transmitted through the first polarizer 83 enters the second Faraday rotator 112, and the polarization direction of the pulsed laser light 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 is transmitted through the second polarizer 88. The polarization direction of the pulsed laser light traveling from MO22 to PO26 at point a is the same as the polarization direction at point e.

[0040] Next, the pulsed laser light returning from PO26 to MO22 will be described. At point e in Fig. 4, the polarization direction of the pulsed laser light propagating from MO22 to PO26 is the same as the polarization direction of the pulsed laser light (return light) returning from PO26 to MO22. Therefore, the return light traveling from PO26 to MO22 passes through the second polarizer 88.

[0041] The polarization direction of the returning light transmitted through the second polarizer 88 is then rotated 45 degrees clockwise by the second Faraday rotator 112 (point c). At point c, the polarization direction of the pulsed laser light propagating in the direction 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 enters the damper 116. The damper 116 absorbs and blocks the light reflected by the first polarizer 83.

[0042] 4.3 Examples of Faraday rotators 5 is a cross-sectional view that shows a schematic configuration example of the Faraday rotator 130. The Faraday rotator 130 can be used as each of the first Faraday rotator 110 and the second Faraday rotator 112. The Faraday rotator 130 has a Faraday material 135 and a magnet 136. The Faraday material 135 is a material that is transparent in ultraviolet wavelengths and has a large Verdet constant. The term "transparent" means that the material has optical transparency.

[0043] The Verdet constant depends on the type of material and the wavelength. For example, calcium fluoride (CaF2), synthetic quartz (SiO2), magnesium fluoride (MgF2), etc. are suitable as the Faraday material 135. The Faraday material 135 is held by a 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 penetrating 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 rotator 130 depends on the sign of the Verdet constant and the direction of the applied magnetic field.

[0045] FIG. 6 shows a preferable range of the magnetic field and the thickness of the Faraday material 135 when the wavelength of the pulsed laser light is the oscillation wavelength of the ArF excimer laser. The oscillation wavelength of the ArF excimer laser includes a wavelength of about 193 nm. FIG. 6 shows the cases where the Faraday material 135 is CaF2 and SiO2, respectively. The thickness of the Faraday material 135 is evaluated based on the thickness in the optical axis direction.

[0046] Fig. 7 shows a preferable range of the magnetic field and the thickness of the Faraday material 135 when the wavelength of the pulsed laser light is the oscillation wavelength of the KrF excimer laser. The oscillation wavelength of the KrF excimer laser includes a wavelength of about 248 nm. Fig. 7 shows the cases where the 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 the magnetic field is the magnetic flux density when a neodymium magnet with strong magnetic force is used. The thickness of the Faraday material 135 is calculated based on the selected material, the magnetic flux density of the magnetic field, and the Verdet constant, to be the thickness at which the polarization plane rotates 45 degrees.

[0048] 6, when the Faraday material 135 is calcium fluoride and the wavelength of the pulsed laser light is the oscillation wavelength of an ArF excimer laser, the preferred ranges of the magnetic field applied to the Faraday rotator 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, they are 0.8T to 1.5T and 15mm to 25mm. Note that notations indicating a numerical range such as "0.5T to 3.0T" indicate a range including the numerical values ​​before and after "to", 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 an ArF excimer laser, the preferable ranges of the magnetic field applied to the Faraday rotator 130 and the thickness of the Faraday material 135 in the optical axis direction are 0.5 T to 3 T and 3 mm to 25 mm, more preferably 0.75 T to 2.9 T and 6 mm to 20 mm, and most preferably 0.8 T to 1.5 T and 8 mm to 15 mm.

[0050] 7, when the Faraday material is calcium fluoride and the wavelength of the pulsed laser light is the oscillation wavelength of a KrF excimer laser, the preferable ranges of the magnetic field applied to the Faraday rotator 130 and the thickness of the Faraday material 135 in the optical axis direction are 0.5 T to 3.0 T and 13 mm to 83 mm, more preferably 0.75 T to 2.9 T and 20 mm to 55 mm, and most preferably 0.8 T to 1.5 T and 30 mm to 50 mm.

[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 a KrF excimer laser, the preferable ranges of the magnetic field applied to the Faraday rotator 130 and the thickness of the Faraday material 135 in the optical axis direction are 0.5 T to 3.0 T and 8 mm to 53 mm, more preferably 0.75 T to 2.9 T and 10 mm to 40 mm, and most preferably 0.8 T to 1.5 T and 15 mm to 30 mm.

[0052] The Faraday material 135 may be divided into a plurality of pieces, and the total of these pieces may satisfy the above thickness. The number of pieces may be, for example, two, three, or four. It is also possible to use different types of Faraday rotators, such as different Faraday materials, different thicknesses in the optical axis direction, and different magnetic field strengths, for the first Faraday rotator 110 and the second Faraday rotator 112. On the other hand, by using the same Faraday material, the same thickness in the optical axis direction, and the same magnetic field strength for the first Faraday rotator 110 and the second Faraday rotator 112, the polarization planes rotate in opposite directions with the same rotation amount (angle), which is easy to handle and is a preferable form.

[0053] 4.4 Permissible angle difference between the transmission axis of the polarizer and the polarization direction of the laser light 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, but they do not necessarily have to be strictly parallel, and an angular difference between the two is permissible as long as the intended function can be achieved in practice.

[0054] FIG. 8 shows a graph showing the relationship between the angle difference between the transmission axis of the polarizer and the polarization direction of the pulsed laser light and the extinction ratio (dB), and a graph in which the extinction ratio is converted into a normalized transmittance. The vertical axis on the left side of FIG. 8 shows the extinction ratio, and the vertical axis on the right side shows the normalized transmittance. The normalized transmittance is a value normalized so that the transmittance is 1.0 when the angle difference is 0 degrees. In each of the first polarizer 83 that transmits the pulsed laser light output from the first Faraday rotator 110 and the second polarizer 88 that transmits the pulsed laser light output from the second Faraday rotator 112, if the normalized transmittance for the incident pulsed laser light is 0.9 or more, they can function effectively and practically. Therefore, according to FIG. 8, the preferable allowable range of the angle 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 a range of ±17.5 degrees in which the normalized transmittance is 0.9 or more.

[0055] 4.5 Actions and Effects According to the ultraviolet laser device 100 of the first embodiment, the polarization direction of the pulsed laser light can be made the same before and after passing through the optical isolator 120 without using the half-wave plate 81, which has low durability at short wavelengths. Therefore, it is possible to suppress the return light without changing other modules that depend on the polarization direction.

[0056] Moreover, according to the ultraviolet laser device 100 of the first embodiment, the pulsed laser light returning from the PO 26 toward the MO 22 is reflected by the first polarizer 83 and absorbed by the damper 116, and is prevented from entering the MO 22. This reduces the thermal load on the MO 22, and improves the energy stability, linewidth stability, and the like, compared to the configuration of the comparative example.

[0057] 4.6 Variations The MO pulse energy monitor 54 may be disposed either upstream or downstream of the optical isolator 120 in which the first Faraday rotator 110 and the second Faraday rotator 112 are disposed in tandem. However, as shown in FIG. 4, the MO pulse energy monitor 54 is preferably disposed upstream of the optical isolator 120. The MO pulse energy monitor 54 is an example of the "energy monitor" in the present disclosure. The directions of the magnetic fields applied to the first Faraday rotator 110 and the second Faraday rotator 112 may be opposite to each other, and are not limited to the example shown in FIG. 4. For example, the magnetic field applied to the first Faraday rotator 110 may be upward in FIG. 4, and the magnetic field applied to the second Faraday rotator 112 may be downward in FIG. 4.

[0058] 4, an example in which the first Faraday rotator 110 and the second Faraday rotator 112 rotate the polarization plane in opposite directions at the same rotation angle (45 degrees) has been described, but the rotation angle of the polarization direction by the first Faraday rotator 110 and the rotation angle of the polarization direction by the second Faraday rotator 112 are not limited to the opposite directions and are the same angle, and an angle difference between the two is allowed within a range in which the intended function can be achieved in practice. According to Fig. 8, the angle difference between the rotation angle in the first rotation direction by the first Faraday rotator 110 and the rotation angle in the second rotation direction (opposite to the first rotation direction) by the second Faraday rotator 112 is allowed to be within 17.5 degrees.

[0059] The rotation angle of the first rotation direction by the first Faraday rotator 110 may be within 45 degrees ± 17.5 degrees, and similarly, the rotation angle of the second rotation direction by the second Faraday rotator 112 may be within 45 degrees ± 17.5 degrees. Due to the configuration in which the polarization direction of the pulsed laser light transmitted through the first Faraday rotator 110 and incident on the first polarizer 83 and the polarization direction of the pulsed laser light returning from the PO26 transmitted through the second Faraday rotator 112 and incident on the first polarizer 83 intersect at an angle of 90 degrees ± 17.5 degrees, the returning light is reflected by the first polarizer 83 and is suppressed from entering the MO22.

[0060] 5. Embodiment 2 5.1 Configuration Fig. 9 shows a schematic configuration of an ultraviolet laser device 102 according to the second embodiment. The differences between the configuration shown in Fig. 9 and Fig. 4 will be described. The ultraviolet laser device 102 shown in Fig. 9 differs from the configuration shown in Fig. 4 in that a two-axis adjustable parallel plane substrate 202 and a two-axis adjustable high reflection mirror 52 are arranged on the optical path between the second polarizer 88 and the PO26. The parallel plane substrate 202 is held by a two-axis angle adjustment holder 204 that can adjust the angle around each of two orthogonal axes as a rotation axis.

[0061] The plane-parallel substrate 202 is disposed on the optical path between the second polarizer 88 and the high-reflection mirror 52. The plane-parallel substrate 202 may be a calcium fluoride substrate. The two-axis angle adjustment holder 204 may be a holder capable of adjusting the angle about, for example, an axis perpendicular to the paper surface of Fig. 9 and an axis parallel to the substrate surface of the plane-parallel substrate 202 and the paper surface of Fig. 9 as rotation axes.

[0062] The high reflection mirror 52 is held by a two-axis angle adjustment holder 208 that can adjust the angle around two orthogonal axes as rotation axes. The two-axis angle adjustment holder 208 may be, for example, a holder that can adjust the angle around an axis perpendicular to the paper surface of Fig. 9 and an axis parallel to the reflective surface of the high reflection mirror 52 and the paper surface of Fig. 9 as rotation axes.

[0063] 5.2 Operation The optical axis is adjusted by adjusting the two-axis adjustable parallel plane substrate 202 and the two-axis adjustable high reflection mirror 52 so that the pulsed laser light from the MO 22 is incident on the PO 26 most efficiently.

[0064] The two-axis adjustable parallel plane substrate 202 is adjusted so that the pulsed laser light from the MO 22 is most efficiently incident on the PO 26 by shifting the pulsed laser light in a direction parallel to the traveling direction.

[0065] The two-axis adjustable high-reflection mirror 52 is adjusted so that the pulsed laser light from the MO 22 is incident on the PO 26 most efficiently by changing the angle at which the pulsed laser light from the MO 22 is incident on the PO 26 .

[0066] Each of the two-axis angle adjustment holder 204 and the two-axis angle adjustment holder 208 is an example of an "optical axis adjustment mechanism" in the present disclosure. Although a configuration including both the two-axis adjustable parallel plane substrate 202 and the two-axis adjustable high reflection mirror 52 is a preferred embodiment, a configuration including only one of them is also possible.

[0067] 5.3 Actions and Effects According to the second embodiment, it is possible to obtain the same effects as those of the first embodiment. Moreover, according to the second embodiment, it is easier to adjust the optical axis of the injected light to be made incident on the PO 26 than in the first embodiment.

[0068] 6. Embodiment 3 6.1 Configuration Fig. 10 shows a schematic configuration of an ultraviolet laser device 103 according to the third embodiment. Differences between the configuration shown in Fig. 10 and Fig. 4 will be described. The ultraviolet laser device 103 shown in Fig. 10 includes an ultraviolet solid-state laser device 232 as an oscillation stage laser instead of the MO 22 in Fig. 4, and includes an excimer amplifier 236 instead of the PO 26. Other configurations may be similar to those shown in Fig. 4.

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

[0070] As an example, the ultraviolet solid-state laser device 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 a CW laser beam with a wavelength of about 773.6 nm, and a semiconductor optical amplifier (SOA) that pulses the CW laser beam. The wavelength conversion system includes a plurality of nonlinear optical crystals, and converts the wavelength of the incident pulsed laser beam to output a fourth harmonic pulsed laser beam. 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] The chamber 242 includes a pair of discharge electrodes 250a, 250b and two windows 252, 254 through which the laser light passes. The discharge electrodes 250a, 250b are disposed opposite each other with a discharge space 256 therebetween. The space between the discharge electrodes 250a, 250b forms the discharge space 256. The direction in which the discharge electrodes 250a, 250b face each other with the discharge space 256 in between corresponds to the discharge direction. The chamber 242 is filled with a laser gas similar to the laser gas described in FIG. 4.

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

[0074] The convex cylindrical mirror 244 and the concave cylindrical mirror 246 are positioned so that the seed light from the ultraviolet solid-state laser device 232 is expanded and amplified in the discharge direction 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 enters the excimer amplifier 236. The seed light having a wavelength of about 193.4 nm that enters the excimer amplifier 236 passes through the discharge space 256 between the discharge electrodes 250a, 250b three times by being reflected by the convex cylindrical mirror 244 and the concave cylindrical mirror 246. This causes the seed light beam to be expanded and amplified. The excimer amplifier 236 is an example of a "multi-pass amplifier" in this disclosure. Not limited to the three-pass excimer amplifier 236, various types of multi-pass amplifiers can be applied.

[0076] The operation of the optical isolator 120 is similar to that of the first embodiment described with reference to Fig. 4. The optical isolator 120 prevents amplified spontaneous emission (ASE) generated in the excimer amplifier 236 from entering the ultraviolet solid-state laser device 232.

[0077] 6.3 Actions and Effects According to the ultraviolet laser device 103 of the third embodiment, the polarization direction can be made the same before and after passing through the optical isolator 120 without using the half-wave plate 81, which has low durability at short wavelengths. Therefore, it is possible to suppress the return light without changing other modules that depend on the polarization direction.

[0078] According to the ultraviolet laser device 103 of embodiment 3, the light returning from the excimer amplifier 236 toward the ultraviolet solid-state laser device 232 does not enter the ultraviolet solid-state laser device 232, so that the thermal load on the ultraviolet solid-state laser device 232 is reduced and the energy stability, linewidth stability, etc. are improved compared to the configuration of the comparative example.

[0079] 7. Embodiment 4 7.1 Configuration Fig. 11 shows a schematic configuration of an ultraviolet laser device 104 according to embodiment 4. The differences between the configuration shown in Fig. 11 and Fig. 4 will be described. The ultraviolet laser device 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 the 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] 12 is a top view illustrating a schematic configuration of the PO 266 applied to the embodiment 4. The ring resonator 270 includes 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 disposed in order to introduce the laser light output from the MO 22 and reflected by the high-reflection mirror 50 and the high-reflection mirror 52 into the ring resonator 270. The high-reflection mirror 283 is disposed on 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 output from the MO 22 is reflected successively by the high-reflection mirror 50 , the high-reflection mirror 52 , and the high-reflection mirror 283 , and then enters the ring resonator 270 from the partial reflection mirror 290 .

[0084] The laser light transmitted through partial reflection mirror 290 is reflected by high reflection mirror 284 and then enters chamber 62 where it is amplified, and then is reflected by high reflection mirror 285 and high reflection mirror 286 and again enters chamber 62 where it is amplified. Then, part of the laser light output from chamber 62 is transmitted by partial reflection mirror 290 and the other part is reflected and is amplified again in ring resonator 270.

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

[0086] The optical isolator 120 suppresses return light from the PO 266 from entering the MO 22. The operation of the optical isolator 120 is similar to that of the first embodiment described with reference to FIG.

[0087] 7.3 Actions and Effects According to the ultraviolet laser device 104 of the fourth embodiment, the same effects as those of the first embodiment can be obtained.

[0088] 8. Manufacturing methods for electronic devices 13 shows a schematic configuration example of an 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 a reticle pattern of a reticle (not shown) arranged on a reticle stage RT with laser light incident from the ultraviolet laser device 100. The projection optical system 306 reduces and projects the laser light transmitted through the reticle to form an image on a workpiece (not shown) arranged on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0089] The exposure apparatus 300 exposes the workpiece to laser light reflecting a reticle pattern by synchronously translating the reticle stage RT and the workpiece table WT. After the reticle pattern is transferred to the semiconductor wafer by the exposure process described above, a semiconductor device can be manufactured through multiple processes. A semiconductor device is an example of an "electronic device" in this disclosure. Instead of the ultraviolet laser device 100, the ultraviolet laser device 102, 103, or 104 described in the second to fourth embodiments may be used to generate laser light.

[0090] 9.Other The above description is intended to be illustrative rather than restrictive. Thus, it will be apparent to one skilled in the art that modifications may be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments may be used in combination.

[0091] Terms used throughout the present specification and claims should be interpreted as "open ended" terms unless otherwise specified. For example, terms such as "include," "have," "comprise," and "include" should be interpreted as "not excluding the presence of elements other than those listed." In addition, the modifier "a" should be interpreted as "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 to include combinations of these with elements other than "A," "B," and "C."

Claims

1. 1. An ultraviolet laser device, comprising: an oscillation stage laser that outputs linearly polarized pulsed laser light having an ultraviolet wavelength; an amplifier that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier, 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 arranged so that a normalized transmittance of 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 transmitted 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; a second polarizer arranged so that a normalized transmittance of the pulsed laser light output from the second Faraday rotator is 0.9 or more; Ultraviolet laser device.

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

3. 2. The ultraviolet laser device according to claim 1, The angle difference between the first angle and the second angle is within 17.5 degrees. Ultraviolet laser device.

4. 2. The ultraviolet laser device according to claim 1, the first angle and the second angle are each within 45 degrees ±17.5 degrees; a polarization direction when the pulsed laser light traveling from the oscillation stage laser toward the amplifier is incident on the first polarizer; the direction of the pulsed laser light returning from the amplifier toward the oscillation stage laser passes through the second Faraday rotator and enters the first polarizer, and the direction of the pulsed laser light intersects with the direction of the polarization of the pulsed laser light at an angle of 90 degrees ±17.5 degrees or less; The pulsed laser light that passes through the second Faraday rotator and is incident on the first polarizer is reflected by the first polarizer. Ultraviolet laser device.

5. 2. The ultraviolet laser device according to claim 1, a magnetic flux density of a magnetic field applied to each of the first Faraday rotator and the second Faraday rotator is equal to or greater than 0.5 T and equal to or less than 3.0 T; Ultraviolet laser device.

6. 6. The ultraviolet laser device according to claim 5, the wavelength of the pulsed laser light is an oscillation wavelength of an ArF excimer laser, a Faraday material included in each of the first Faraday rotator and the second Faraday rotator 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.

7. 6. The ultraviolet laser device according to claim 5, the wavelength of the pulsed laser light is an oscillation wavelength of an ArF excimer laser, a Faraday material included in each of the first Faraday rotator and the second Faraday rotator 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.

8. 6. The ultraviolet laser device according to claim 5, the wavelength of the pulsed laser light is an oscillation wavelength of a KrF excimer laser, a Faraday material included in each of the first Faraday rotator and the second Faraday rotator 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.

9. 6. The ultraviolet laser device according to claim 5, the wavelength of the pulsed laser light is an oscillation wavelength of a KrF excimer laser, a Faraday material included in each of the first Faraday rotator and the second Faraday rotator 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.

10. 2. The ultraviolet laser device according to claim 1, The Faraday material included in each of the first Faraday rotator and the second Faraday rotator is composed of a plurality of divided materials. Ultraviolet laser device.

11. 2. The ultraviolet laser device according to claim 1, an optical axis adjustment mechanism including at least a two-axis adjustment mechanism is provided between the second polarizer and the amplifier; Ultraviolet laser device.

12. 12. The ultraviolet laser device according to claim 11, The optical axis adjustment mechanism includes a parallel plane substrate that can be adjusted along two axes by the adjustment mechanism. Ultraviolet laser device.

13. 12. The ultraviolet laser device according to claim 11, The optical axis adjustment mechanism includes a high-reflection mirror that can be adjusted in two axes by the adjustment mechanism. Ultraviolet laser device.

14. 2. The ultraviolet laser device according to claim 1, Each of the oscillation stage laser and the amplifier has a chamber filled with a laser gas. Ultraviolet laser device.

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

16. 2. The ultraviolet laser device according to claim 1, the amplifier comprises a resonator; Ultraviolet laser device.

17. 2. The ultraviolet laser device according to claim 1, The amplifier is a multi-pass amplifier. Ultraviolet laser device.

18. 2. The ultraviolet laser device according to claim 1, a damper that absorbs light that has passed from the amplifier through the second polarizer and the second Faraday rotator and is reflected by the first polarizer; Ultraviolet laser device.

19. 2. The ultraviolet laser device according to claim 1, an energy monitor for measuring pulse energy of the oscillation stage laser is provided between the oscillation stage laser and the optical isolator; Ultraviolet laser device.

20. 1. A method for manufacturing an electronic device, comprising: an oscillation stage laser that outputs linearly polarized pulsed laser light having an ultraviolet wavelength; an amplifier that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier, 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 arranged so that a normalized transmittance of 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 transmitted 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; a second polarizer arranged so that a normalized transmittance of the pulsed laser light output from the second Faraday rotator is 0.9 or more; and outputting the amplified laser light to an exposure device; exposing the laser light onto a photosensitive substrate in the exposure apparatus to manufacture an electronic device. A method for manufacturing an electronic device, comprising:

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