Ultraviolet laser device and method for manufacturing electronic device

Abstract

This UV laser device is provided with: an optical isolator arranged on the optical path between an oscillation stage laser that outputs linearly polarized laser pulses with a UV wavelength and an amplifier that amplifies and outputs the laser pulses; and a processor. The optical isolator includes a first polarizer, a first Faraday rotor which rotates, in a first rotation direction, the polarization direction of the laser pulses that have passed through the first polarizer, a second polarization element which is arranged such that the laser pulses outputted from the first Faraday rotor are transmitted, a first actuator which causes a first Faraday material and a first magnet of the first Faraday rotor to move relative to one another in the direction of the optical axis, and a first sensor which measures the power of those of the laser pulses outputted from the oscillation stage laser that have been reflected by the second polarizer, wherein the processor controls the first actuator on the basis of the measurement results of the first sensor.

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

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

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-24357 [Patent Document 2] Japanese Patent Application Publication No. 3-273208 [Patent Document 3] Summary of JP 2004-62006 A

[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, an optical isolator arranged on an optical path between the oscillation-stage laser and the amplifier, and a processor, wherein the optical isolator includes: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material and rotating the polarization direction of the pulsed laser light that has passed through the first polarizer in a first rotation direction; a second polarizer arranged to transmit the pulsed laser light output from the first Faraday rotator; a first actuator that moves the first magnet and the first Faraday material relatively in the optical axis direction of the pulsed laser light; and a first sensor that measures the power of the pulsed laser light output from the oscillation-stage laser that is reflected by the second polarizer, and the processor controls the first actuator based on the measurement result of the first sensor.

[0006] An ultraviolet laser device according to another aspect of the present disclosure comprises 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, an optical isolator arranged on an optical path between the oscillation-stage laser and the amplifier, and a processor, wherein the optical isolator includes a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser, a first Faraday rotator including a first magnet and a first Faraday material and rotating the polarization direction of the pulsed laser light that has passed through the first polarizer in a first rotation direction, a first actuator that moves the first magnet and the first Faraday material relatively in the optical axis direction of the pulsed laser light, and a third sensor that measures the power of light reflected by the first polarizer of the light returning from the amplifier to the oscillation-stage laser, and the processor controls the first actuator based on the measurement result of the third sensor.

[0007] An ultraviolet laser 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, an optical isolator arranged on an optical path between the oscillation-stage laser and the amplifier, a beam splitter arranged on an optical path between the oscillation-stage laser and the optical isolator, a fourth sensor that measures the power of light reflected by the beam splitter, and a processor, wherein the optical isolator includes a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser, a first Faraday rotator including a first magnet and a first Faraday material and rotating the polarization direction of the pulsed laser light that has passed through the first polarizer in a first rotation direction, and a first actuator that moves the first magnet and the first Faraday material relatively in the optical axis direction of the pulsed laser light, and the processor controls the first actuator based on the measurement results of the fourth sensor.

[0008] A method for manufacturing 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, an optical isolator that is arranged on an optical path between the oscillation-stage laser and the amplifier, and a processor, wherein the optical isolator includes a first polarizer that is arranged so that the pulsed laser light output from the oscillation-stage laser passes through, a first Faraday rotator that includes a first magnet and a first Faraday material and rotates the polarization direction of the pulsed laser light that has passed through the first polarizer in a first rotation direction, and a processor that rotates the pulsed laser light output from the first Faraday rotator in a first rotation direction. The method includes: a second polarizer arranged to transmit the pulsed laser light; a first actuator that moves the first magnet and the first Faraday material relatively in the optical axis direction of the pulsed laser light; and a first sensor that measures the power of the pulsed laser light output from the oscillation stage laser that is reflected by the second polarizer, wherein the processor controls the first actuator based on the measurement result of the first sensor; generating laser light amplified by an amplifier using an ultraviolet laser device, outputting the amplified laser light to an exposure device, and exposing the laser light onto a photosensitive substrate in the exposure device to manufacture an electronic device.

[0009] a first Faraday rotator including a first magnet and a first Faraday material arranged to rotate the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a first actuator for relatively moving the first magnet and the first Faraday material in the optical axis direction of the pulsed laser light; and a third sensor for measuring the power of light reflected by the first polarizer among the light returning from the amplifier to the oscillation-stage laser, wherein the processor controls the first actuator based on the measurement result of the third sensor; and a method for manufacturing an electronic device comprising: generating laser light amplified by the amplifier using an ultraviolet laser apparatus; 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 explanation of the drawings]

[0010] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [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 a problem with the ultraviolet laser device according to the comparative example. [Figure 3] FIG. 3 shows a schematic configuration of an optical isolator according to a comparative example that suppresses optical feedback. [Figure 4] FIG. 4 is an explanatory diagram of a method for adjusting an optical isolator according to a comparative example. [Figure 5] FIG. 5 is an explanatory diagram of a method for adjusting an optical isolator according to a comparative example. [Figure 6] FIG. 6 shows a schematic configuration of the ultraviolet laser device according to the first embodiment. [Figure 7]FIG. 7 is a cross-sectional view showing the details of the configuration of the Faraday rotator. [Figure 8] FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. [Figure 9] FIG. 9 is a flowchart showing an example of control of the optical isolator in the ultraviolet laser device according to the first embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of the processing content applied to step S15 in FIG. [Figure 11] FIG. 11 is a flowchart showing an example of the processing content applied to step S18 in FIG. [Figure 12] FIG. 12 is a flowchart showing another example of control of the optical isolator in the ultraviolet laser device. [Figure 13] FIG. 13 is a flowchart showing an example of the processing content applied to step S15B in FIG. [Figure 14] FIG. 14 is a flowchart showing an example of the processing content applied to step S18B in FIG. [Figure 15] FIG. 15 shows a schematic configuration of an ultraviolet laser device according to the second embodiment. [Figure 16] FIG. 16 is a flowchart showing an example of control of the optical isolator in the ultraviolet laser device according to the second embodiment. [Figure 17] FIG. 17 is a flowchart showing an example of the processing content applied to step S18C in FIG. [Figure 18] FIG. 18 is a flowchart showing another example of control of the optical isolator in the ultraviolet laser device. [Figure 19] FIG. 19 is a flowchart showing an example of the processing content applied to step S18D in FIG. [Figure 20] FIG. 20 shows a schematic configuration of an ultraviolet laser device according to the third embodiment. [Figure 21] FIG. 21 is a flowchart showing an example of control of the optical isolator in the ultraviolet laser device according to the third embodiment. [Figure 22]FIG. 22 is a flowchart showing an example of the processing content applied to step S18E in FIG. [Figure 23] FIG. 23 shows a schematic configuration of an exemplary exposure apparatus. Embodiment

[0011] -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 Actions and Effects 4.4 Variation 1-1 4.5 Variation 1-2 5. Embodiment 2 5.1 Configuration 5.2 Operation 5.3 Actions and Effects 5.4 Variation 2-1 5.5 Variation 2-2 5.6 Other 6. Embodiment 3 6.1 Configuration 6.2 Operation 6.3 Actions and Effects 6.4 Variation 3 7. Other examples of ultraviolet laser device configurations 8. Manufacturing methods for electronic devices 9.Other Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0012] 1. Explanation of terms The term "polarizer" refers to an optical element that separates light having a specific polarization direction (transmission axis direction) from light having a polarization direction perpendicular to that direction.

[0013] In this specification, unless otherwise specified, the term "parallel" is not limited to strictly parallel, but also includes the concept of approximately parallel, including a range of angle differences that are practically acceptable and do not lose their technical significance, unless otherwise specified, and in this specification, unless otherwise specified, the term "orthogonal" or "perpendicular" is not limited to strictly orthogonal or perpendicular, but also includes the concept of approximately orthogonal or approximately perpendicular ....

[0014] 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 configuration that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges.

[0015] The ultraviolet laser device 20 is an excimer laser device including a master oscillator (MO) 22, which is an oscillation stage laser, an MO beam steering unit 24, and an amplification stage laser, a power oscillator (PO) 26. The MO 22 includes a line narrowing module (LNM) 30, a chamber 32, and an output coupling mirror 34.

[0016] The LNM 30 includes a prism expander 36 for narrowing the spectral linewidth, and a grating 38. The prism expander 36 and 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 reflectivity of 40% to 60%. The output coupling mirror 34 is arranged so as to form an optical resonator together with the LNM 30.

[0017] 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 supply (not shown). The power supply may be a pulse power module (PPM) including a switch and a charging capacitor.

[0018] 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 .

[0019] An MO pulse energy monitor 54 is disposed between high-reflection mirror 50 and 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 disposed on the optical path of the pulsed laser light output from the MO 22, and is disposed so that the reflected light of the BS 55 enters the optical sensor 56.

[0020] 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.

[0021] 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 a 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%.

[0022] 2.2 Operation A high-voltage pulse is applied between discharge electrodes 40a and 40b in chamber 32 from a power supply (not shown). When a discharge occurs between discharge electrodes 40a and 40b in chamber 32, the laser gas is excited, and pulsed laser light with an ultraviolet wavelength of 150 nm to 380 nm is narrowed by an optical resonator formed by output coupling mirror 34 and LNM 30 and output from output coupling mirror 34.

[0023] The energy of the pulsed laser light output from the output coupling mirror 34 is measured by an MO pulse energy monitor 54. The pulsed laser light is also incident on a rear mirror 60 of the PO 26 by the MO beam steering unit 24 as seed light.

[0024] At the timing when 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 optical resonator formed 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.

[0025] 3. Challenges FIG. 2 illustrates a problem with the ultraviolet laser device 20 according to the comparative example. Among the pulsed laser light output from the MO 22, some light returns from the PO 26 (return light). When the return light from the PO 26 returns to the MO 22, laser performance deteriorates. The "return light" referred to here includes two types: MO return light and PO leakage light. The light emitted from the MO 22 enters the PO 26, but because the rear mirror 60 inside the PO 26 is a partial reflection mirror (reflectivity 50% to 90%), some of the light that enters the rear mirror 60 returns directly to the MO 22 without entering the PO 26. The light that is reflected by the rear mirror 60 and returns to the MO 22 without entering the chamber 62 of the PO 26 is called "MO return light."

[0026] On the other hand, light that enters PO26 from MO22 and passes through rear mirror 60 is resonated and amplified within PO26 and then output. As mentioned above, rear mirror 60 within PO26 is a partial reflection mirror, so some of the light that enters chamber 62 of PO26 and is amplified returns to MO22. Of the light amplified by PO26, the light that passes through rear mirror 60 and returns to MO22 is called "PO-leaving light."

[0027] The feedback light from the PO 26 becomes a thermal load on the LNM 30 and other components, which can cause deterioration in the stability of the linewidth and pulse energy, etc. To suppress the feedback light entering the MO 22, an optical isolator can be placed between the MO 22 and the PO 26.

[0028] Fig. 3 shows a schematic configuration example of an optical isolator 80 according to a comparative example that suppresses returning light. The optical isolator 80 is disposed between the MO 22 and the PO 26. 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 (returning light) traveling from the PO 26 to the MO 22.

[0029] The optical isolator 80 includes a half-wave plate 81, a first polarizer 83, a Faraday rotator 84, and a second polarizer 88 arranged in this order from the MO22 side. The Faraday rotator 84 includes a Faraday material 85 and a magnet 86. The magnet 86 has a hollow structure, and the Faraday material 85 is arranged inside the magnet 86 via a holder. The internal space (hollow portion) of the magnet 86 in which the Faraday material 85 is arranged is a magnetic field generating unit that generates a magnetic field to be applied to the Faraday material 85. In FIG. 3, the right-pointing arrow shown in the Faraday rotator 84 indicates the direction of the magnetic field applied to the Faraday material 85 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, i.e., the polarization direction.

[0030] 3, linearly polarized pulsed laser light polarized in a specific direction (here, the horizontal direction is illustrated) is output from MO 22. The polarization direction of the linearly polarized pulsed laser light output from MO 22 is rotated by 45 degrees counterclockwise by half-wave plate 81. First polarizer 83 is arranged such that its transmission axis is parallel to the polarization direction of the pulsed laser light output from half-wave plate 81, and the pulsed laser light output from half-wave plate 81 passes through first polarizer 83.

[0031] The polarization direction of the pulsed laser light that has passed through the first polarizer 83 is rotated 45 degrees clockwise by the Faraday material 85 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 arranged so that its transmission axis is parallel to the polarization direction of the pulsed laser light output from the Faraday rotator 84. The pulsed laser light output from the Faraday rotator 84 passes through the second polarizer 88 and then enters the PO26.

[0032] 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. As a result, even if the optical isolator 80 is provided, the polarization direction of the pulsed laser light does not change before and after the optical isolator 80.

[0033] Of the returning light, the polarized component having the same polarization direction as the pulsed laser light incident on PO26 passes through the second polarizer 88, and the polarization direction is rotated 45 degrees clockwise by the Faraday material 85 to which a magnetic field is applied. Then, the returning light is reflected by the first polarizer 83, and does not enter MO22.

[0034] Of the returning light, the polarization component having a polarization direction different from that of the pulsed laser light incident on the PO 26 is reflected by the second polarizer 88 and does not return to the MO 22. The second polarizer 88 is arranged to remove the disturbed polarization component when the polarization of the returning light from the PO 26 is disturbed, thereby achieving a higher effect of the optical isolator 80. Therefore, the second polarizer 88 may not be used if there is no disturbance in the polarization of the returning light or if a sufficient extinction ratio can be obtained even with disturbed returning light.

[0035] Here, the ratio of the returning light transmitted through the first polarizer 83 to the returning light incident on the second polarizer 88 is called the extinction ratio.

[0036] The optical isolator 80 is adjusted before being mounted on a laser to obtain the appropriate optical isolator effect. The adjustment method will be explained using Figures 4 and 5. The optical isolator 90 shown in Figures 4 and 5 includes a Faraday rotator 91 instead of the half-wave plate 81 shown in Figure 3. This is because the Faraday material 95 that makes up the Faraday rotator 91 has higher resistance to ultraviolet wavelength laser light than the half-wave plate 81.

[0037] The Faraday rotator 91 has a structure similar to that of the Faraday rotator 84, and includes a Faraday material 95 and a magnet 96. The direction of the magnetic field applied to the Faraday material 95 by the magnet 96 of the Faraday rotator 91 is opposite to the direction of the magnetic field applied to the Faraday material 85 of the Faraday rotator 84.

[0038] The adjustment locations include a relative position a1 of the Faraday material 95 with respect to the magnet 96 in the optical axis direction of the pulsed laser light, and a relative position a2 of the Faraday material 85 with respect to the magnet 86 in the optical axis direction of the pulsed laser light. These relative positions a1 and a2 are adjusted to adjust the amount of rotation of the polarization plane of the pulsed laser light in the Faraday rotators 91 and 84. The amount of rotation of the polarization plane of the pulsed laser light in the Faraday rotators 91 and 84 is determined by the strength of the magnetic field, physical quantities such as the refractive index of the Faraday materials 95 and 85, and the lengths of the Faraday materials 95 and 85.

[0039] The adjustment procedure is, for example, as follows.

[0040] Step 1: A slit SL and a sensor SE1 are disposed between the light source LS and the optical isolator 90, and the power of the pulsed laser light incident on the optical isolator 90 via the slit SL is measured by the sensor SE1.

[0041] Step 2: Then, remove the sensor SE1, and adjust the relative position a1 of the Faraday rotator 91. At this time, the first polarizer 83 is positioned at angles b1 and c1, which are the design values. The angle b1 is the angle of rotation about an axis parallel to the optical axis. The angle c1 is the tilt angle of the surface of the first polarizer 83 with respect to the optical axis. Then, place the sensor SE2 at a position where it can measure the power of the pulsed laser light transmitted through the first polarizer 83. For example, as shown in Figure 4, place the sensor SE2 between the first polarizer 83 and the Faraday rotator 84. The relative position a1 of the Faraday rotator 91 is adjusted so that the output of the sensor SE2 is maximized, and the sensor is fixed with spacers 97a, 97b, etc. After adjusting the relative position a1, remove the sensor SE2.

[0042] Step 3: Next, the sensor SE3 is placed at a position where the power of the pulsed laser light transmitted through the second polarizer 88 can be measured, and the relative position a2 of the Faraday rotator 84 is adjusted. At this time, the second polarizer 88 is placed at angles b2 and c2 of the design values. The relative position a2 of the Faraday rotator 84 is adjusted so that the output of the sensor SE3 is maximized, and the sensor is fixed with spacers 87a, 87b, etc. Then, the sensor SE3 is removed. The ratio of the output of the sensor SE3 to the output of the sensor SE1, "sensor SE3 output / sensor SE1 output," is the transmittance of the optical isolator 90. For example, the transmittance of the optical isolator 90 is approximately 65% for Faraday rotators 91 and 84 that are not equipped with anti-reflection measures.

[0043] Step 4: Next, the extinction ratio is confirmed. As shown in FIG. 5, steering mirrors MR1, MR2, MR3, and MR4 are positioned so that the pulsed laser light output from light source LS passes through second polarizer 88, Faraday rotator 84, first polarizer 83, and Faraday rotator 91 in that order. Steering mirror MR1 is positioned between slit SL and optical isolator 90. Steering mirror MR2 is positioned to reflect the light reflected by steering mirror MR1 and make it incident on steering mirror MR3. Steering mirror MR3 is positioned to reflect the light reflected by steering mirror MR2 and make it incident on steering mirror MR4. Steering mirror MR4 is positioned to reflect the light reflected by steering mirror MR3 and make it incident on second polarizer 88 of optical isolator 90 along the same optical axis as the return light from PO26.

[0044] Then, a sensor SE4 is placed between the steering mirror MR4 and the optical isolator 90, and the power of the pulsed laser light incident on the optical isolator 90 is measured by the sensor SE4. After that, the sensor SE4 is removed, and a sensor SE5 is placed in a position where it can measure the power of the pulsed laser light that has passed through the Faraday rotator 91. The ratio of the output of the sensor SE4 to the output of the sensor SE5, "sensor SE5 output / sensor SE4 output," is the extinction ratio. The extinction ratio is equal to or less than a predetermined value. For example, the extinction ratio is equal to or less than 1 / 10.

[0045] When the optical isolator 90 adjusted before being mounted on the laser as described above is mounted on the ultraviolet laser device 20 and used, physical quantities such as the strength of the magnetic field and the refractive index of the Faraday materials 85 and 95 change due to the influence of heat and other factors during laser operation, and the amount of polarization rotation changes.

[0046] When the amount of polarization rotation in the optical isolator 90 changes, the transmittance decreases and the extinction ratio deteriorates. The decrease in transmittance deteriorates the stability of the pulse energy of the pulsed laser light output from the PO 26. Furthermore, when the extinction ratio deteriorates, the amount of light returning to the MO 22 increases, which causes a thermal load on the LNM 30 and other components, deteriorating the stability of the spectral linewidth and pulse energy.

[0047] 4. Embodiment 1 4.1 Configuration FIG. 6 schematically illustrates the configuration of an ultraviolet laser device 21 including an optical isolator 110 according to the first embodiment. Differences between the configuration illustrated in FIG. 6 and those illustrated in FIGS. 1, 4, and 5 will be described below. In the ultraviolet laser device 21, the optical isolator 110 is disposed between the MO 22 and the PO 26. The optical isolator 110 may be disposed on the optical path between the beam splitter 55 and the high-reflection mirror 52, which are not illustrated in FIG. 6. The magnets 96 and 86 are selected to have a magnetic field strength that allows a slight margin for the predetermined rotation of the polarization plane in the Faraday rotator 91 and the Faraday rotator 84. The magnets 96 and 86 may be permanent magnets.

[0048] As the initial relative positions a1 and a2, the Faraday materials 95 and 85 are positioned at positions shifted from the position where the magnetic field strength is maximum. For example, the centers of the magnet 96 and the Faraday material 95 are positioned at positions shifted by 2 mm in the optical axis direction of the pulsed laser light.

[0049] The optical isolator 110 is provided with an actuator 120 that moves the Faraday material 95 relative to the magnet 96 in the optical axis direction of the pulsed laser beam, and an actuator 130 that moves the Faraday material 95 relative to the magnet 86 in the optical axis direction of the pulsed laser beam. The amount of movement of the Faraday material 95 by the actuator 120 is preferably at least half the length of the Faraday material 95 in the optical axis direction of the pulsed laser beam. The minimum movement amount of the actuator 120 may be, for example, approximately 0.2 mm. The movement amount and minimum movement amount of the actuator 130 may be the same as those of the actuator 120. Note that the actuator 120 may be configured to move the Faraday material 95 and the magnet 96 relatively in the optical axis direction of the pulsed laser beam, and may move the magnet 96 relative to the Faraday material 95 in the optical axis direction. Similarly, the actuator 130 may be configured to move the Faraday material 85 and the magnet 86 relatively in the optical axis direction of the pulsed laser beam, and may move the magnet 86 relative to the Faraday material 85 in the optical axis direction.

[0050] The optical isolator 110 is provided with a sensor SE6 that detects the power of the pulsed laser light reflected by the first polarizer 83, and a sensor SE7 that detects the power of the pulsed laser light reflected by the second polarizer 88, among the pulsed laser light propagating from MO22 to PO26.

[0051] The ultraviolet laser device 21 including the optical isolator 110 also includes a processor 140 that receives outputs from the sensors SE6 and SE7 and controls the actuators 120 and 130. The processor 140 controls the actuator 120 based on the measurement result of the sensor SE6, and controls the actuator 130 based on the measurement result of the sensor SE7.

[0052] The processor 140 may function as a laser control unit that controls the operation of the ultraviolet laser device 21. The processor 140 of the present disclosure is a processing device that includes a storage device in which a control program is stored and a CPU (Central Processing Unit) that executes the control program. The processor 140 is specially configured or programmed to execute various processes included in the present disclosure. The processor 140 may include an integrated circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0053] Fig. 7 is a cross-sectional view showing the details of the configuration of the Faraday rotator 91. Fig. 7 shows a cross section parallel to the optical axis of the pulsed laser beam. Note that the center line CL in Fig. 7 represents the center of the magnet 96. Fig. 8 is a cross-sectional view taken along line 8-8 in Fig. 7.

[0054] Since the cross section perpendicular to the optical axis of the pulsed laser light output from the MO 22 has a vertically long rectangle, the cross section of the Faraday material 95 may have a vertically long rectangle in order to make the magnet 96 smaller.

[0055] The cross-sectional shape of the magnetic field generating section 97 of the magnet 96 on which the Faraday material 95 is placed may be a vertically long rectangle oriented in the same direction as the cross-sectional shape of the Faraday material 95. The Faraday material 95 is placed on the magnetic field generating section 97 of the magnet 96 while being held by a Faraday material holder 100. The direction of the magnetic field penetrating the Faraday material 95 is parallel to the propagation direction of light. The direction of rotation of the polarization plane (polarization direction) by the Faraday rotator 91 depends on the sign of the Verdet constant and the direction of the applied magnetic field. The cross-sectional shape of the Faraday material holder 100 perpendicular to the optical axis of the pulsed laser light may also be a vertically long rectangle, similar to the Faraday material 95. A through-hole 101 is formed at one end of the vertically long rectangle of the Faraday material holder 100, and a female screw hole 102 is formed at the other end.

[0056] A guide shaft 124 is inserted into the through hole 101, and a male screw 126 is screwed into the female screw hole 102. The Faraday material holder 100 is held by plates 121a and 121b via the guide shaft 124 and the male screw 126. The male screw 126 is held rotatably and connected to the actuator 120. The plates 121a and 121b also hold a magnet 96.

[0057] The Faraday material 95 and the Faraday material 85 may be the same material, for example, calcium fluoride (CaF 2 ). The configuration of the Faraday rotator 84 is similar to that of the Faraday rotator 91.

[0058] The Faraday rotator 84 is an example of a "first Faraday rotator" in the present disclosure, and the Faraday rotator 91 is an example of a "second Faraday rotator" in the present disclosure. The Faraday material 85 and the magnet 86 are an example of a "first Faraday material" and a "first magnet" in the present disclosure, and the Faraday material 95 and the magnet 96 are an example of a "second Faraday material" and a "second magnet" in the present disclosure. The direction of rotation of the polarization plane of the pulsed laser light by the Faraday rotator 84 is an example of a "first rotation direction" in the present disclosure. The direction of rotation of the polarization plane of the pulsed laser light by the Faraday rotator 91 is an example of a "second rotation direction" in the present disclosure. The actuator 130 is an example of a "first actuator" in the present disclosure, and the actuator 120 is an example of a "second actuator" in the present disclosure. The sensor SE7 is an example of a "first sensor" in the present disclosure, and the sensor SE6 is an example of a "second sensor" in the present disclosure.

[0059] 4.2 Operation 4 and 5, the optical isolator 110 is mounted on the ultraviolet laser device 21. The ultraviolet laser device 21 is a laser device in which the optical isolator 110 is arranged on the optical path between the beam splitter 55 and the high-reflection mirror 52 in the ultraviolet laser device 20 described in FIG.

[0060] 9 is a flowchart showing an example of control of the optical isolator 110 in the ultraviolet laser device 21. Each step shown in FIG. 9 can be realized by the processor 140 executing a program.

[0061] In step S10, the ultraviolet laser device 21 performs laser irradiation. This laser irradiation may be adjusted oscillation, or may be laser operation for exposure to output laser light to the exposure device.

[0062] In step S11, the ultraviolet laser device 21 measures the initial output value P6i using the sensor SE6, and the processor 140 stores the initial output value P6i.

[0063] In step S12, the ultraviolet laser device 21 measures an initial output value P7i using the sensor SE7, and the processor 140 stores the initial output value P7i. In subsequent steps, the processor 140 monitors the outputs of the sensors SE6 and SE7 during the laser irradiation period (operation). If the amount of rotation of the polarization plane in the optical isolator 110 changes due to the influence of heat or the like during laser operation, the transmittance of each of the first polarizer 83 and the second polarizer 88 deteriorates, and the amount of pulsed laser light reflected by each of the first polarizer 83 and the second polarizer 88 increases. In other words, by monitoring the outputs of the sensors SE6 and SE7, it is possible to detect changes in the amount of rotation of the polarization plane.

[0064] In step S13, the ultraviolet laser device 21 measures the output P6c using the sensor SE6, and the processor 140 stores the output P6c.

[0065] In step S14, the processor 140 determines whether the output P6c is equal to or less than the target value P6t. The target value P6t may be, for example, 120% of the initial output value P6i (P6t = P6i × 1.2). The target value P6t is an example of the "third target value" in this disclosure.

[0066] If the determination result in step S14 is No, that is, if the output P6c of sensor SE6 is greater than the target value P6t, processor 140 proceeds to step S15, where it adjusts relative position a1 with actuator 120. The subroutine applied in step S15 will be described later with reference to FIG. 10. After step S15, processor 140 proceeds to step S16.

[0067] On the other hand, if the determination result in step S14 is Yes, that is, if the output P6c of the sensor SE6 is equal to or less than the target value P6t, the processor 140 proceeds to step S16. In step S16, the ultraviolet laser device 21 measures the output P7c using the sensor SE7, and the processor 140 stores the output P7c.

[0068] In step S17, the processor 140 determines whether the output P7c is equal to or less than the target value P7t. The target value P7t may be, for example, 120% of the initial output value P7i (P7t = P7i × 1.2). The target value P7t is an example of the "first target value" in this disclosure.

[0069] If the determination result in step S17 is No, that is, if the output P7c of sensor SE7 is greater than the target value P7t, processor 140 proceeds to step S18, where it adjusts relative position a2 with actuator 130. The subroutine applied in step S18 will be described later with reference to FIG. 11. After step S18, processor 140 proceeds to step S19.

[0070] On the other hand, if the determination result in step S17 is Yes, that is, if the output P7c of the sensor SE7 is equal to or less than the target value P7t, the processor 140 proceeds to step S19.

[0071] In step S19, processor 140 determines whether or not to end the laser irradiation. If the determination result in step S19 is No, that is, if the laser irradiation is not to be ended, processor 140 returns to step S13. Steps S13 to S19 are repeated until the laser irradiation is ended.

[0072] On the other hand, if the determination result in step S19 is Yes, that is, if laser irradiation is to be ended, the processor 140 ends the flowchart of FIG.

[0073] FIG. 10 is a flowchart showing an example of the processing content (adjustment 1 of the Faraday rotator 91) applied to step S15 in FIG.

[0074] In step S20, the processor 140 sets the distance FL1 by which the Faraday material 95 is moved to "+LP". LP is a determined amount of movement when moving the Faraday material 95 or the Faraday material 85, and the direction in which the pulsed laser light travels (propagates) from the MO 22 to the PO 26 is defined as the "+" direction. LP may be, for example, 0.2 mm. In step S20, the initial value of the distance FL1 is set to +LP.

[0075] In step S21, the processor 140 stores the output P6c of the sensor SE6 as the pre-control output P6p.

[0076] Then, in step S22, the processor 140 moves the Faraday material 95 of the Faraday rotator 91 by a distance FL1 using the actuator 120. After moving the Faraday material 95 by FL1, in step S23, the ultraviolet laser device 21 measures the output P6c using the sensor SE6, and the processor 140 stores the output P6c.

[0077] In step S24, processor 140 determines whether output P6c is equal to or less than target value P6t.

[0078] If the determination result in step S24 is No, that is, if the output P6c of the sensor SE6 is greater than the target value P6t, the processor 140 proceeds to step S25. In step S25, the processor 140 determines whether the output P6c is equal to or less than the output P6p before the control.

[0079] If the determination result in step S25 is Yes, that is, if the output P6c of sensor SE6 is equal to or less than the output P6p before the control, processor 140 returns to step S21. On the other hand, if the determination result in step S25 is No, that is, if the output P6c of sensor SE6 is greater than the output P6p before the control, processor 140 proceeds to step S26 and sets distance FL1 to -LP. After step S26, processor 140 returns to step S21.

[0080] If the determination result in step S24 is Yes, that is, if the output P6c of the sensor SE6 is equal to or less than the target value P6t, the processor 140 ends the flowchart of FIG. 10 and returns to the flowchart of FIG.

[0081] FIG. 11 is a flowchart showing an example of the processing content (adjustment 1 of the Faraday rotator 84) applied to step S18 in FIG.

[0082] In step S30, the processor 140 sets the distance FL2 for moving the Faraday material 85 to "+LP." In step S30, the initial value of the distance FL2 is set to +LP.

[0083] In step S31, the processor 140 stores the output P7c of the sensor SE7 as the pre-control output P7p.

[0084] Then, in step S32, the processor 140 moves the Faraday material 85 of the Faraday rotator 84 by a distance FL2 using the actuator 130. After moving the Faraday material 85 by FL2, in step S33, the ultraviolet laser device 21 measures the output P7c using the sensor SE7, and the processor 140 stores the output P7c.

[0085] In step S34, processor 140 determines whether output P7c is equal to or less than target value P7t. If the determination result in step S34 is No, that is, if output P7c of sensor SE7 is greater than target value P7t, processor 140 proceeds to step S35. In step S35, processor 140 determines whether output P7c is equal to or less than pre-control output P7p.

[0086] If the determination result in step S35 is Yes, that is, if output P7c is equal to or less than pre-control output P7p, processor 140 returns to step S31. On the other hand, if the determination result in step S35 is No, that is, if output P7c is greater than pre-control output P7p, processor 140 proceeds to step S36 and sets distance FL2 to -LP. After step S36, processor 140 returns to step S31.

[0087] If the determination result in step S34 is Yes, that is, if the output P7c of the sensor SE7 is equal to or less than the target value P7t, the processor 140 ends the flowchart of FIG. 11 and returns to the flowchart of FIG.

[0088] 4.3 Actions and Effects According to the first embodiment, it is possible to adjust the transmittance and extinction ratio of the optical isolator 110 during laser irradiation. According to the first embodiment, even if the amount of polarization rotation changes due to the influence of heat or the like during laser operation, by controlling the relative position a1 of the Faraday material 95 with respect to the magnet 96 in the optical axis direction of the pulsed laser light and the relative position a2 of the Faraday material 85 with respect to the magnet 86 in the optical axis direction of the pulsed laser light, a decrease in transmittance is suppressed and at the same time, a deterioration in the extinction ratio is suppressed. As a result, it is possible to suppress a deterioration in the stability of the pulse energy of the pulsed laser light output from the PO 26 due to a decrease in the transmittance of the optical isolator 110, and a deterioration in the stability of the spectral linewidth and the stability of the pulse energy due to a thermal load on the LNM 30, etc., due to the return light to the MO 22.

[0089] According to the first embodiment, the optical isolator 110 can be automatically optimized and operated even during exposure operation. Furthermore, according to the first embodiment, the optical isolator 110 can be automatically controlled and adjusted not only during exposure operation but also during adjustment oscillation.

[0090] 4.4 Variation 1-1 Figures 12 to 14 are flowcharts showing other examples of control of the optical isolator 110 in the ultraviolet laser device 21. The flowcharts of Figures 12 to 14 may be used instead of the flowcharts of Figures 9 to 11. The differences between the flowcharts of Figures 12 to 14 and Figures 9 to 11 will be described below.

[0091] The flowchart in FIG. 12 includes steps S15B and S18B instead of steps S15 and S18 in FIG.

[0092] If the determination result in step S14 is No, the processor 140 proceeds to step S15B to perform a second adjustment process for the Faraday rotator 91. Details of the subroutine applied in step S15B will be described later with reference to FIG.

[0093] Furthermore, if the determination result of step S17 is No, the processor 140 proceeds to step S18B, where it performs processing for adjustment 2 of the Faraday rotator 84. Details of the subroutine applied to step S18B will be described later with reference to Fig. 14. The other steps may be similar to those in Fig. 11.

[0094] Fig. 13 is a flowchart showing an example of the processing content (adjustment 2 of the Faraday rotator 91) applied to step S15B of Fig. 12. The flowchart of Fig. 10 describes an example of controlling the output P6c of the sensor SE6 to be equal to or less than the target value P6t, but the flowchart shown in Fig. 13 is an example of controlling the output P6c of the sensor SE6 to be the minimum value.

[0095] In step S40 of FIG. 13, the processor 140 sets the distance FL1 by which the Faraday material 95 is moved to "+LP."

[0096] In step S41, the processor 140 stores the output P6c of the sensor SE6 as the output P6(p) of the index p, where p may be any integer, for example, p may be 0.

[0097] Then, in step S42, the processor 140 moves the Faraday material 95 of the Faraday rotor 91 by a distance FL1 by the actuator 120. After moving the Faraday material 95 by FL1, in step S43, the ultraviolet laser device 21 measures the output P6c by the sensor SE6, and the processor 140 stores this output P6c as the output P6(p + 1) of index p + 1.

[0098] Next, in step S44, the processor 140 determines whether P6(p) is greater than or equal to P6(p + 1). This determination is used to determine the moving direction of the Faraday material 95. If the determination result in step S44 is a No determination, that is, if P6(p) < P6(p + 1), the processor 140 proceeds to step S45. In step S45, the processor 140 sets the distance FL1 to "-LP" and reverses the moving direction. After step S45, the processor 140 returns to step S42.

[0099] If the determination result in step S44 is a Yes determination, that is, if P6(p) ≥ P6(p + 1) is satisfied, the processor 140 proceeds to step S46.

[0100] In step S46, the processor 140 moves the Faraday material 95 of the Faraday rotor 91 by a distance FL1 by the actuator 120.

[0101] Then, in step S47, the ultraviolet laser device 21 measures the output P6c by the sensor SE6, and the processor 140 stores this output P6c as the output P6(p + 2) of index p + 2.

[0102] Next, in step S48, processor 140 determines whether P6(p)≧P6(p+1)≦P6(p+2) is satisfied. This determination is a process for searching for the minimum value of output P6c of sensor SE6. If the determination result in step S48 is No, that is, if P6(p+2) is smaller than P6(p+1), the minimum value cannot be identified, so processor 140 returns to step S41 and repeats steps S41 to S48.

[0103] If the determination result in step S48 is Yes, that is, if P6(p)≧P6(p+1)≦P6(p+2) is satisfied, processor 140 identifies P6(p+1) as the minimum value and proceeds to step S49.

[0104] In step S49, processor 140 determines whether distance FL1 is set to "+LP." If the determination result in step S49 is Yes, that is, if FL1=+LP, processor 140 proceeds to step S50 and sets distance FL1 to "-LP." On the other hand, if the determination result in step S49 is No, that is, if FL1=-LP, processor 140 proceeds to step S51 and sets distance FL1 to "+LP."

[0105] After step S50 or step S51, the processor 140 proceeds to step S52. In step S52, the processor 140 moves the Faraday material 95 of the Faraday rotator 91 by a distance FL1 using the actuator 120. By this step S52, the Faraday material 95 moves to a position corresponding to the index p+1 when the output of the sensor SE6 is determined to be the minimum value (P6(p+1)). After step S52, the processor 140 ends the flowchart of FIG. 13 and returns to the flowchart of FIG. 12.

[0106] The minimum value of the output P6c of the sensor SE6 identified by the determination in step S48 is an example of the "fourth target value" in the present disclosure.

[0107] FIG. 14 is a flowchart showing an example of the processing content applied to step S18B in FIG. 12 (adjustment 2 of the Faraday rotor 84). In the flowchart of FIG. 11, an example of controlling so that the output P7c of the sensor SE7 becomes equal to or less than the target value P7t was described. However, the flowchart shown in FIG. 14 is an example of controlling so that the output P7c of the sensor SE7 becomes the minimum value.

[0108] In step S60 of FIG. 14, the processor 140 sets the distance FL2 for moving the Faraday material 85 to “+LP”.

[0109] In step S61, the processor 140 stores the output P7c of the sensor SE7 as the output P7(p) of the index p.

[0110] Then, in step S62, the processor 140 moves the Faraday material 85 of the Faraday rotor 84 by the distance FL2 by the actuator 130. After moving the Faraday material 85 by FL2, in step S63, the ultraviolet laser device 21 measures the output P7c by the sensor SE7, and the processor 140 stores this output P7c as the output P7(p + 1) of the index p + 1.

[0111] Next, in step S64, the processor 140 determines whether P7(p) is greater than or equal to P7(p + 1). This determination is used to determine the moving direction of the Faraday material 85. If the determination result in step S64 is a No determination, that is, if P7(p) < P7(p + 1), the processor 140 proceeds to step S65. In step S65, the processor 140 sets the distance FL2 to “-LP” and reverses the moving direction. After step S65, the processor 140 returns to step S62.

[0112] If the determination result in step S64 is a Yes determination, that is, if P7(p) ≥ P7(p + 1) is satisfied, the processor 140 proceeds to step S66.

[0113] In step S66, the processor 140 causes the actuator 130 to move the Faraday material 85 of the Faraday rotator 84 by a distance FL2.

[0114] Then, in step S67, the ultraviolet laser device 21 measures the output P7c by the sensor SE7, and the processor 140 stores this output P7c as the output P7(p+2) of the index p+2.

[0115] Next, in step S68, processor 140 determines whether P7(p)≧P7(p+1)≦P7(p+2) is satisfied. This determination is a process for searching for the minimum value. If the determination result in step S68 is No, that is, if P7(p+2) is smaller than P7(p+1), the minimum value cannot be identified, so processor 140 returns to step S61 and repeats steps S61 to S68.

[0116] If the determination result in step S68 is Yes, that is, if P7(p)≧P7(p+1)≦P7(p+2) is satisfied, processor 140 identifies P7(p+1) as the minimum value and proceeds to step S69.

[0117] In step S69, processor 140 determines whether distance FL2 is set to "+LP." If the determination result in step S69 is Yes, that is, if FL2=+LP, processor 140 proceeds to step S70 and sets distance FL2 to "-LP." On the other hand, if the determination result in step S69 is No, that is, if FL2=-LP, processor 140 proceeds to step S71 and sets distance FL1 to "+LP."

[0118] After step S70 or step S71, the processor 140 proceeds to step S72. In step S72, the processor 140 moves the Faraday material 85 of the Faraday rotator 84 by a distance FL2 using the actuator 130. By this step S71, the Faraday material 85 moves to a position corresponding to the index p+1 at which it is determined that the output P7c of the sensor SE7 has a minimum value. After step S72, the processor 140 ends the flowchart of FIG. 14 and returns to the flowchart of FIG. 12.

[0119] The minimum value of the output P7c of the sensor SE7 identified by the determination in step S68 is an example of the “second target value” in this disclosure. By applying the control method of Modification 1-1, the same effects as in the first embodiment can be obtained.

[0120] 4.5 Variation 1-2 The Faraday rotator 91 is an optical system that rotates the polarization direction by 45 degrees. For example, a retarder (half-wave plate 81) that shifts the phase by 180 degrees may be used instead of the Faraday rotator 91. In this case, the sensor SE6 and the actuator 120 do not need to be provided.

[0121] 5. Embodiment 2 5.1 Configuration FIG. 15 schematically illustrates the configuration of an ultraviolet laser device 21 including an optical isolator 112 according to the second embodiment. Differences between the configuration illustrated in FIG. 15 and that illustrated in FIG. 6 will be described below. The optical isolator 112 illustrated in FIG. 15 includes a sensor SE8, instead of the sensor SE7 in FIG. 6, that detects the power of light reflected by the first polarizer 83 from the light returning from the PO26 to the optical isolator 112. The other configurations are the same as those of the first embodiment. The sensor SE8 is an example of a "third sensor" in the present disclosure.

[0122] 5.2 Operation Fig. 16 is a flowchart showing an example of control including the optical isolator 112 in the ultraviolet laser device 21 according to embodiment 2. In embodiment 2, the flowchart in Fig. 16 is adopted instead of the flowchart in Fig. 9. The differences between the flowchart in Fig. 16 and Fig. 9 will be described.

[0123] The flowchart in FIG. 16 includes steps S12C, S16C, S17C, and S18C instead of steps S12, S16, S17, and S18 in FIG.

[0124] In step S12C, the ultraviolet laser device 21 measures the initial output value P8i using the sensor SE8, and the processor 140 stores the initial output value P8i. In a subsequent step, the processor 140 monitors the outputs of the sensors SE6 and SE8 during the laser irradiation period.

[0125] If the determination result in step S14 is Yes, the processor 140 proceeds to step S16C. In step S16C, the ultraviolet laser device 21 measures the output P8c using the sensor SE8, and the processor 140 stores the output P8c.

[0126] Next, in step S17C, processor 140 determines whether output P8c of sensor SE8 is equal to or greater than target value P8t. Target value P8t may be, for example, 80% of initial output value P8i (P8t = P8i × 0.8). Target value P8t is an example of a "fifth target value" in the present disclosure.

[0127] If the determination result in step S17C is No, that is, if the output P8c is smaller than the target value P8t, processor 140 proceeds to step S18C. Details of the subroutine applied to step S18C will be described later with reference to FIG. 17. After step S18C, processor 140 proceeds to step S19. The other steps may be the same as those in FIG. 9.

[0128] FIG. 17 is a flowchart showing an example of the processing content (adjustment 3 of the Faraday rotator 84) applied to step S18C in FIG.

[0129] In step S70 of FIG. 17, the processor 140 sets the distance FL2 by which the Faraday material 85 is moved to "+LP".

[0130] In step S71, the processor 140 stores the output P8c of the sensor SE8 as the pre-control output P8p.

[0131] Then, in step S72, the processor 140 moves the Faraday material 85 of the Faraday rotator 84 by a distance FL2 using the actuator 130. After moving the Faraday material 85 by FL2, in step S73, the ultraviolet laser device 21 measures the output P8c using the sensor SE8, and the processor 140 stores the output P8c.

[0132] In step S74, processor 140 determines whether output P8c is equal to or greater than target value P8t. If the determination result in step S74 is No, that is, if output P8c of sensor SE8 is smaller than target value P8t, processor 140 proceeds to step S75. In step S75, processor 140 determines whether output P8c is equal to or greater than pre-control output P8p.

[0133] If the determination result in step S75 is Yes, that is, if output P8c is equal to or greater than pre-control output P8p (P8c≧P8p), processor 140 returns to step S71. On the other hand, if the determination result in step S75 is No, that is, if output P8c is smaller than pre-control output P8p, processor 140 proceeds to step S76 and sets distance FL2 to −LP. After step S76, processor 140 returns to step S71.

[0134] If the determination result in step S74 is Yes, that is, if the output P8c of the sensor SE8 is equal to or greater than the target value P8t, the processor 140 ends the flowchart of FIG. 17 and returns to the flowchart of FIG.

[0135] 5.3 Actions and Effects According to the second embodiment, it is possible to adjust the transmittance and extinction ratio of the optical isolator 112 during laser irradiation, and the same effects as those of the first embodiment can be obtained.

[0136] 5.4 Variation 2-1 15 does not need to be disposed if there is no change in the polarization of the light passing through the optical isolator 112 toward PO26 and the polarization of the light returning from PO26 to the optical isolator 112. That is, in the case of the second embodiment, it is also possible to configure the optical path between the Faraday rotator 84 and PO26 without disposing the second polarizer 88.

[0137] The configuration without the second polarizer 88 has the following advantages.

[0138] [1] The transmittance of the entire optical isolator 112 unit can be expected to improve.

[0139] [2] The optical isolator 112 unit can be expected to be miniaturized.

[0140] 5.5 Variation 2-2 Figures 18 and 19 are flowcharts showing another example of control of the optical isolator 112 in the ultraviolet laser device 21. The flowcharts of Figures 18 and 19 may be used instead of the flowcharts of Figures 16 and 17. The differences between the flowcharts of Figures 18 and 19 and those of Figures 16 and 17 will be described below.

[0141] The flowchart in FIG. 18 includes steps S15B and S18D instead of steps S15 and S18C in FIG.

[0142] If the determination result in step S14 is No, the processor 140 proceeds to step S15B to perform the process of adjustment 2 of the Faraday rotator 91. Details of the subroutine applied in step S15B are as described in FIG.

[0143] Furthermore, if the determination result of step S17C is No, the processor 140 proceeds to step S18D, where it performs adjustment 4 of the Faraday rotator 84. Details of the subroutine applied to step S18D will be described later with reference to FIG. 19. After step S18D, the processor 140 proceeds to step S19. The other steps may be the same as those in FIG. 16.

[0144] Fig. 19 is a flowchart showing an example of the processing content (adjustment 4 of the Faraday rotator 84) applied to step S18D of Fig. 18. The flowchart of Fig. 17 describes an example of controlling the output P8c of the sensor SE8 to be equal to or greater than the target value P8t, but the flowchart of Fig. 19 is an example of controlling the output P8c of the sensor SE8 to be its maximum value.

[0145] In step S80 of FIG. 19, the processor 140 sets the distance FL2 by which the Faraday material 85 is moved to "+LP".

[0146] In step S81, the processor 140 stores the output P8c of the sensor SE8 as the output P8(p) of the index p.

[0147] Then, in step S82, the processor 140 moves the Faraday material 85 of the Faraday rotator 84 by a distance FL2 using the actuator 130. After moving the Faraday material 85 by FL2, in step S83, the ultraviolet laser device 21 measures the output P8c using the sensor SE8, and the processor 140 stores this output P8c as the output P8(p+1) of the index p+1.

[0148] Next, in step S84, processor 140 determines whether P8(p+1) is greater than or equal to P8(p). This determination is used to determine the movement direction of Faraday material 85. If the determination result in step S84 is No, that is, if P8(p)>P8(p+1), processor 140 proceeds to step S85.

[0149] In step S85, the processor 140 sets the distance FL2 to "-LP" and reverses the movement direction. After step S85, the processor 140 returns to step S82.

[0150] On the other hand, if the determination result in step S84 is Yes, that is, if P8(p)≦P8(p+1) is satisfied, processor 140 proceeds to step S86.

[0151] In step S86, the processor 140 causes the actuator 130 to move the Faraday material 85 of the Faraday rotator 84 by a distance FL2.

[0152] Then, in step S87, the ultraviolet laser device 21 measures the output P8c by the sensor SE8, and the processor 140 stores this output P8c as the output P8(p+2) of the index p+2.

[0153] Next, in step S88, processor 140 determines whether P8(p)≦P8(p+1)≧P8(p+2) is satisfied. This determination is used to search for the maximum value. The maximum value of output P8c of sensor SE8 is an example of the "sixth target value" in this disclosure. If the determination result in step S88 is No, that is, if P8(p+2) is greater than P8(p+1), the maximum value cannot be identified, so processor 140 returns to step S81 and repeats steps S81 to S88.

[0154] On the other hand, if the determination result in step S88 is Yes, that is, if P8(p)≦P8(p+1)≧P8(p+2) is satisfied, processor 140 determines that P8(p+1) is the maximum value and proceeds to step S89.

[0155] In step S89, processor 140 determines whether distance FL2 is set to "+LP." If the determination result in step S89 is Yes, that is, if the movement distance FL2 when output P8(p+2) is obtained is +LP, processor 140 proceeds to step S90 and sets distance FL2 to "-LP."

[0156] On the other hand, if the determination result in step S89 is No, that is, if the movement distance FL2 when the output P8(p+2) is obtained is -LP, the processor 140 proceeds to step S91 and sets the distance FL2 to "+LP".

[0157] After step S90 or step S91, the processor 140 proceeds to step S92. In step S92, the processor 140 operates the actuator 130 to move the Faraday material 85 of the Faraday rotator 84 by a distance FL2 relative to the magnet 86. By this step S92, the Faraday material 85 moves to a position corresponding to the index p+1 at which it is determined that the output P8c of the sensor SE8 is maximum. After step S92, the processor 140 ends the flowchart of FIG. 19 and returns to the flowchart of FIG. 18.

[0158] By applying the control method of Modification 2-2, the same effects as those of the second embodiment can be obtained.

[0159] 5.6 Other In the second embodiment, similarly to the modified example 1-2 of the first embodiment, an optical system such as a half-wave plate 81 may be employed instead of the Faraday rotator 91.

[0160] 6. Embodiment 3 6.1 Configuration Fig. 20 shows a schematic configuration of an ultraviolet laser device 21 including an optical isolator 113 according to embodiment 3. Differences between the configuration shown in Fig. 20 and that shown in Fig. 6 will be described.

[0161] The optical isolator 113 shown in Fig. 20 does not have the sensor SE7 in Fig. 6 arranged therein. The third embodiment is configured to use the measurement value of the sensor SE9 of the MO pulse energy monitor 54 arranged between the MO 22 and the optical isolator 113 instead of the sensor SE7. The sensor SE9 may be the optical sensor 56 described in Fig. 1. The other configurations are the same as those of the first embodiment. The sensor SE9 is an example of the "fourth sensor" in this disclosure.

[0162] 6.2 Operation The light incident on the sensor SE9 includes MO injected light, MO returned light, and PO escaping light, and the outputs of these MO injected light, MO returned light, and PO escaping light are measured by the sensor SE9.

[0163] The MO injected light has a constant value, and the MO returned light and the PO escaping light have constant values if the effect of the optical isolator 113 is constant.

[0164] A change in the output (measurement value) of sensor SE9 means that there has been a change in the effectiveness of the optical isolator 113, so the processor 140 controls the position of the Faraday material 85 via the actuator 130 so that the output of sensor SE9 becomes smaller than a specified value.

[0165] 21 is a flowchart showing an example of control of the optical isolator 113 in the ultraviolet laser device 21. The differences between the flowchart in FIG. 21 and FIG. 9 will be described.

[0166] The flowchart in FIG. 21 includes steps S12E, S16E, S17E, and S18E instead of steps S12, S16, S17, and S18 in FIG.

[0167] In step S12E, the ultraviolet laser device 21 measures the initial output value P9i using the sensor SE9, and the processor 140 stores the initial output value P9i. In a subsequent step, the processor 140 monitors the outputs of the sensors SE6 and SE9 during the laser irradiation period.

[0168] If the determination result in step S14 is Yes, the processor 140 proceeds to step S16E. In step S16E, the ultraviolet laser device 21 measures the output P9c using the sensor SE9, and the processor 140 stores the output P9c.

[0169] Next, in step S17E, the processor 140 determines whether the output P9c of the sensor SE9 is equal to or less than a target value P9t. The target value P9t may be, for example, 120% of the initial output value P9i (P9t=P9i×1.2).

[0170] If the determination result in step S17E is No, that is, if output P9c is greater than target value P9t, processor 140 proceeds to step S18E. An example of a subroutine applied to step S18E will be described later with reference to Figure 22. The other steps are the same as those in the flowcharts of Figures 9 and 10.

[0171] FIG. 22 is a flowchart showing an example of the processing content (adjustment 5 of the Faraday rotator 84) applied to step S18E of FIG.

[0172] In step S100, the processor 140 sets the distance FL2 by which the Faraday material 85 is moved to "+LP".

[0173] In step S101, the processor 140 stores the output P9c of the sensor SE9 as the pre-control output P9p.

[0174] Then, in step S102, the processor 140 moves the Faraday material 85 by a distance FL2 using the actuator 130. After moving the Faraday material 85 by FL2, in step S103, the ultraviolet laser device 21 measures the output P9c using the sensor SE9, and the processor 140 stores the output P9c.

[0175] In step S104, processor 140 determines whether output P9c of sensor SE9 is equal to or less than target value P9t. If the determination result in step S104 is No, that is, if output P9c of sensor SE9 is greater than target value P9t, processor 140 proceeds to step S105.

[0176] In step S105, processor 140 determines whether output P9c is equal to or less than pre-control output P9p. If the determination result in step S105 is Yes, that is, if output P9c is equal to or less than pre-control output P9p, processor 140 returns to step S101. On the other hand, if the determination result in step S105 is No, that is, if output P9c is greater than pre-control output P9p, processor 140 proceeds to step S106 and sets distance FL2 to -LP. After step S106, processor 140 returns to step S101.

[0177] If the determination result in step S104 is Yes, that is, if the output P9c of the sensor SE9 is equal to or less than the target value P9t, the processor 140 ends the flowchart of FIG. 22 and returns to the flowchart of FIG.

[0178] 6.3 Actions and Effects According to the third embodiment, the same effects as those of the first embodiment can be obtained.

[0179] 6.4 Variation 3 Also in the third embodiment, control may be adopted in which the outputs of the sensors SE6 and SE9 become minimum values, as in the modified example 1-1 of the first embodiment. Also in the third embodiment, an optical system such as a half-wave plate 81 may be adopted instead of the Faraday rotator 91, as in the modified example 1-2 of the first embodiment.

[0180] 7. Other examples of ultraviolet laser device configurations The amplification-stage laser is not limited to a configuration having a Fabry-Perot resonator such as PO26 shown in Figure 2, but may also have a configuration having a ring resonator. Alternatively, the amplification-stage laser is not limited to a configuration having an optical resonator, but may be a simple amplifier. For example, the amplification-stage laser may be a multi-pass amplifier such as a three-pass amplifier that amplifies seed light by reflecting it off a cylindrical mirror and passing it through a discharge space three times.

[0181] The oscillation stage laser is not limited to a narrow-band gas laser such as the MO22 shown in Fig. 2, but may also be an ultraviolet solid-state laser that outputs pulsed laser light with an ultraviolet wavelength. For example, the oscillation stage laser may be a solid-state laser that oscillates at a wavelength of approximately 193.4 nm, or an ultraviolet solid-state laser that outputs fourth harmonic light of a titanium sapphire laser (wavelength approximately 774 nm).

[0182] 8. Manufacturing methods for electronic devices 23 shows a schematic configuration of an exemplary exposure apparatus 300. The exposure apparatus 300 includes an illumination optical system 304 and a projection optical system 306. The ultraviolet laser device 21 generates laser light and outputs it to the exposure apparatus 300. The illumination optical system 304 illuminates a reticle pattern of a reticle (not shown) placed on a reticle stage RT with the laser light incident from the ultraviolet laser device 21. The projection optical system 306 reduces and projects the laser light that has passed through the reticle, forming an image on a workpiece (not shown) placed on a workpiece table WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0183] The exposure apparatus 300 exposes the workpiece with laser light reflecting the reticle pattern by synchronously translating the reticle stage RT and the workpiece table WT. After the reticle pattern is transferred to the semiconductor wafer through 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.

[0184] 9.Other The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0185] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, terms such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Furthermore, it should be construed as including combinations of these with elements other than "A," "B," and "C."

Claims

1. an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength; an amplifier including an optical resonator that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier; a processor, The optical isolator comprises: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material, which rotates the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a second polarizer disposed so as to transmit the pulsed laser beam output from the first Faraday rotator; a first actuator that relatively moves the first magnet and the first Faraday material in the optical axis direction of the pulsed laser beam; a first sensor that measures the power of the pulsed laser beam reflected by the second polarizer, out of the pulsed laser beam output from the oscillation-stage laser; the processor controls the first actuator based on the measurement result of the first sensor. Ultraviolet laser device.

2. 2. The ultraviolet laser device according to claim 1, the processor controls the first actuator so that the measurement result of the first sensor is equal to or less than a first target value; Ultraviolet laser device.

3. 2. The ultraviolet laser device according to claim 1, the processor controls the first actuator so that the measurement result of the first sensor becomes a second target value; Ultraviolet laser device.

4. 2. The ultraviolet laser device according to claim 1, the first actuator moves a first Faraday material relative to the first magnet; Ultraviolet laser device.

5. 2. The ultraviolet laser device according to claim 1, the first magnet is a permanent magnet; Ultraviolet laser device.

6. 2. The ultraviolet laser device according to claim 1, the processor controls the first actuator while the oscillation stage laser is operating. Ultraviolet laser device.

7. 7. The ultraviolet laser device according to claim 6, the processor controls the first actuator when a measurement result of the first sensor becomes greater than a first target value. Ultraviolet laser device.

8. 2. The ultraviolet laser device according to claim 1, The optical isolator comprises: on the oscillation stage laser side of the first polarizer, a second Faraday rotator including a second magnet and a second Faraday material, which rotates the polarization direction of the pulsed laser light output from the oscillation-stage laser in a second rotation direction opposite to the first rotation direction; a second actuator that relatively moves the second magnet and the second Faraday material in the optical axis direction of the pulsed laser beam; a second sensor that measures the power of the pulsed laser light reflected by the first polarizer; the processor controls the second actuator based on the measurement result of the second sensor. Ultraviolet laser device.

9. 9. The ultraviolet laser device according to claim 8, the processor controls the second actuator so that the measurement result of the second sensor is equal to or less than a third target value. Ultraviolet laser device.

10. 9. The ultraviolet laser device according to claim 8, the processor controls the second actuator so that the measurement result of the second sensor becomes a fourth target value. Ultraviolet laser device.

11. 9. The ultraviolet laser device according to claim 8, the second actuator moves the second Faraday material relative to the second magnet; Ultraviolet laser device.

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

13. 2. The ultraviolet laser device according to claim 1, the oscillation stage laser and the amplifier are excimer lasers; Ultraviolet laser device.

14. 2. The ultraviolet laser device according to claim 1, the first faradic material is calcium fluoride; Ultraviolet laser device.

15. an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength; an amplifier including an optical resonator that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier; a processor, The optical isolator comprises: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material, which rotates the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a first actuator that relatively moves the first magnet and the first Faraday material in the optical axis direction of the pulsed laser beam; a third sensor that measures the power of light reflected by the first polarizer among the light returning from the amplifier to the oscillation-stage laser, the processor controls the first actuator based on the measurement result of the third sensor. Ultraviolet laser device.

16. 16. The ultraviolet laser device according to claim 15, the processor controls the first actuator so that the measurement result of the third sensor is equal to or greater than a fifth target value. Ultraviolet laser device.

17. 16. The ultraviolet laser device according to claim 15, the processor controls the first actuator so that the measurement result of the third sensor becomes a sixth target value. Ultraviolet laser device.

18. an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength; an amplifier including an optical resonator that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier; a beam splitter disposed on an optical path between the oscillation stage laser and the optical isolator; a fourth sensor that measures the power of light reflected by the beam splitter; a processor, The optical isolator comprises: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material, which rotates the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a first actuator that relatively moves the first magnet and the first Faraday material in the optical axis direction of the pulsed laser beam; Including, the processor controls the first actuator based on the measurement result of the fourth sensor. Ultraviolet laser device.

19. A method for manufacturing an electronic device, comprising: an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength; an amplifier including an optical resonator that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier; a processor, The optical isolator comprises: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material, which rotates the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a second polarizer disposed so as to transmit the pulsed laser beam output from the first Faraday rotator; a first actuator that relatively moves the first magnet and the first Faraday material in the optical axis direction of the pulsed laser beam; a first sensor that measures the power of the pulsed laser beam reflected by the second polarizer, out of the pulsed laser beam output from the oscillation-stage laser; the processor controls the first actuator based on the measurement result of the first sensor; and generates laser light using an ultraviolet laser device, which is amplified by the amplifier; 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:

20. A method for manufacturing an electronic device, comprising: an oscillation stage laser that outputs linearly polarized pulsed laser light of an ultraviolet wavelength; an amplifier including an optical resonator that amplifies and outputs the pulsed laser light; an optical isolator disposed on an optical path between the oscillation stage laser and the amplifier; a processor, The optical isolator comprises: a first polarizer arranged to transmit the pulsed laser light output from the oscillation-stage laser; a first Faraday rotator including a first magnet and a first Faraday material, which rotates the polarization direction of the pulsed laser light transmitted through the first polarizer in a first rotation direction; a first actuator that relatively moves the first magnet and the first Faraday material in the optical axis direction of the pulsed laser beam; a third sensor that measures the power of light reflected by the first polarizer among the light returning from the amplifier to the oscillation-stage laser, the processor controls the first actuator based on the measurement result of the third sensor; and generates laser light using an ultraviolet laser device, which is amplified by the amplifier; 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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