JP2019135788A - Laser device and extreme-ultraviolet light generation system - Google Patents

Abstract

To correct the change of an optical path in a slab type optical amplifier.SOLUTION: A laser device according to one aspect disclosed herein may comprises: an oscillator that outputs a laser beam; a slab type optical amplifier that amplifies the laser beam output from the oscillator by passing the beam through a slab-like light amplification region and outputs the resultant laser beam; and a mirror disposed on an optical path of a laser beam input to the slab type optical amplifier or a laser beam output from the slab type optical amplifier, which is shifted in a direction in parallel with a laser progress plane in the slab type optical amplifier. The laser device is capable of correcting an optical path change in the slab type optical amplifier.SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a laser device and an extreme ultraviolet light generation system using the laser device.

  In recent years, along with miniaturization of semiconductor processes, miniaturization of transfer patterns in optical lithography of semiconductor processes has been rapidly progressing. In the next generation, fine processing of 70 nm to 45 nm, and further fine processing of 32 nm or less will be required. Therefore, for example, an exposure apparatus combining an apparatus for generating extreme ultraviolet (EUV) light having a wavelength of about 13 nm and a reduced projection reflective optical system to meet the demand for fine processing of 32 nm or less. Development is expected.

  The EUV light generation apparatus includes an LPP (Laser Produced Plasma) system using plasma generated by irradiating a target material with laser light, and a DPP (Discharge Produced Plasma) using plasma generated by discharge. Three types of devices have been proposed: a device of the system and a device of SR (Synchrotron Radiation) system using orbital radiation.

JP 2010-135769 A JP2010-186735 JP2012-175006 JP2013-84807A US Patent Application Publication No. 2010/0127191 US Patent Application Publication No. 2012/0019826

  An example laser device of the present disclosure includes an oscillator that outputs laser light, a slab optical amplifier that amplifies and outputs the laser light output from the oscillator by passing through a slab-shaped optical amplification region, and A mirror that is disposed on an optical path of laser light input to the slab type optical amplifier or laser light output from the slab type optical amplifier and moves in a direction parallel to the laser traveling plane in the slab type optical amplifier. But you can.

Several embodiments of the present disclosure are described below by way of example only and with reference to the accompanying drawings.
FIG. 1 schematically illustrates an exemplary configuration of an exemplary LPP EUV light generation system. FIG. 2 schematically shows a comparative example of the laser device. FIG. 3A schematically shows a configuration example of a slab type optical amplifier. FIG. 3B schematically shows a configuration example of a slab type optical amplifier. FIG. 4 schematically shows a comparative example of a method for correcting an optical path changed in a slab type optical amplifier. FIG. 5 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the first embodiment. FIG. 6A schematically illustrates the configuration of the optical path correction mechanism according to the first embodiment. FIG. 6B schematically illustrates the configuration of the optical path correction mechanism according to the first embodiment. FIG. 7A schematically shows an example of a method of moving the high reflection mirror for correcting the optical path in the first embodiment. FIG. 7B schematically illustrates an example of a method of moving the high reflection mirror for correcting the optical path in the first embodiment. FIG. 7C schematically illustrates an example of a method of moving the high reflection mirror for correcting the optical path in the first embodiment. FIG. 7D schematically illustrates an example of a method of moving the high reflection mirror for correcting the optical path in the first embodiment. FIG. 8 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the second embodiment. FIG. 9 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the third embodiment. FIG. 10 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the fourth embodiment. FIG. 11A schematically illustrates a configuration of an optical path correction mechanism according to the fourth embodiment. FIG. 11B schematically illustrates the configuration of the optical path correction mechanism according to the fourth embodiment. FIG. 12A schematically shows a beam profile of a normal optical path in the fourth embodiment. FIG. 12B schematically shows the beam profile of the changed optical path in the fourth embodiment. FIG. 12C equivalently shows the normal optical path and the changed optical path in the fourth embodiment. FIG. 13A schematically shows a beam profile after correcting the changed angular component of the optical path in the fourth embodiment. FIG. 13B schematically illustrates the beam profile after correcting the changed angle component and parallel movement component of the optical path in the fourth embodiment. FIG. 14 schematically shows a partial configuration of a laser apparatus including a modification of the optical path correction mechanism in the fourth embodiment. FIG. 15 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the fifth embodiment. FIG. 16A schematically shows a configuration example of a crystal slab type optical amplifier. FIG. 16B schematically shows a configuration example of a crystal slab type optical amplifier. FIG. 17 schematically shows a partial configuration of a laser apparatus including an optical path correction mechanism in the sixth embodiment. FIG. 18 schematically shows a configuration of a laser apparatus including a main pulse laser apparatus and a prepulse laser apparatus in the seventh embodiment.

<Contents>
1. Outline 2. 2. Explanation of terms 3. Overall description of EUV light generation system 4. Comparative example of laser device including master oscillator and amplifier 5. Problems in comparative examples of laser devices Embodiment 1: Laser device including optical path correction mechanism (mirror control of optical path correction mechanism)
7). Embodiment 2: Laser device including temperature correction mechanism (temperature detection)
8). Embodiment 3: Laser apparatus including optical path correction mechanism (profile detection)
9. Embodiment 4: Laser apparatus including an optical path correction mechanism (angle component correction)
10. Embodiment 5: Laser device including optical path correction mechanism (input-side optical path correction mechanism)
11. Embodiment 6: Laser apparatus including an optical path correction mechanism (crystal slab type optical amplifier)
12 Embodiment 7: Laser apparatus including main pulse laser apparatus and pre-pulse laser apparatus

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Embodiment described below shows some examples of this indication, and does not limit the contents of this indication. In addition, all the configurations and operations described in the embodiments are not necessarily essential as the configurations and operations of the present disclosure. In addition, the same referential mark is attached | subjected to the same component and the overlapping description is abbreviate | omitted.

1. Outline The laser apparatus used in the LPP type EUV light generation system may be a pulse laser apparatus that outputs pulsed laser light. The pulse laser device may be a MOPA laser device including a master oscillator (MO) that outputs a short pulse of laser light with high repetition and at least one optical amplifier (PA). A slab optical amplifier capable of multipath amplification may be used as the optical amplifier.

  The inventors have found that the optical path of the laser light amplified by the slab type optical amplifier can change immediately after the optical amplifier is activated. In particular, it has been found that the change in the optical path is large in the in-plane direction of the surface on which the laser light travels in the slab type optical amplifier. Further, it was found that the change in the parallel movement of the optical path in the plane was large and the change in the angle of the optical path in the plane was small. By changing the optical path of the laser light amplified by the slab type optical amplifier, the laser light to the next stage apparatus does not enter through an appropriate optical path, and the pulse laser light output from the laser apparatus can be reduced.

  In one aspect of the present disclosure, the laser device may include an oscillator that outputs laser light, and a slab optical amplifier that amplifies and outputs the laser light output from the oscillator. The laser device is further disposed on the optical path of the laser light input to the slab optical amplifier or the laser light output from the slab optical amplifier, and moves in a direction parallel to the laser traveling plane in the slab optical amplifier. A mirror may be included. According to one aspect of the present disclosure, an optical path change in a slab type optical amplifier can be corrected.

2. Explanation of Terms Terms used in the present disclosure are described below. The “slab type optical amplifier” is an optical amplifier including a slab optical amplification region. The medium of the slab type optical amplifier is not limited and may be a gas or a solid. The “free space direction” is an arbitrary direction parallel to the surface in which the laser light travels in the optical amplification region. The “waveguide direction” is the normal direction of the surface in which the laser light travels in the optical amplification region, and is perpendicular to any free space direction. The “high reflection mirror” is a mirror that can reflect light of a target wavelength with a desired reflectance. The “start-up time” of the slab type optical amplifier is the time when the incident laser light can be amplified.

3. General Description of EUV Light Generation System 3.1 Configuration FIG. 1 schematically shows a configuration of an exemplary LPP EUV light generation system. The EUV light generation apparatus 1 may be used together with at least one laser apparatus 3. In the present application, a system including the EUV light generation apparatus 1 and the laser apparatus 3 is referred to as an EUV light generation system 11. As shown in FIG. 1 and described in detail below, the EUV light generation apparatus 1 may include a chamber 2 and a target supply unit 26.

  The chamber 2 may be sealable. The target supply unit 26 may be attached so as to penetrate the wall of the chamber 2, for example. The target material supplied from the target supply unit 26 may include, but is not limited to, tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more thereof.

  The wall of the chamber 2 may be provided with at least one through hole. A window 21 may be provided in the through hole, and the pulse laser beam 32 output from the laser device 3 may pass through the window 21. In the chamber 2, for example, an EUV collector mirror 23 having a spheroidal reflecting surface may be disposed. The EUV collector mirror 23 may have first and second focal points.

  For example, a multilayer reflective film in which molybdenum and silicon are alternately laminated may be formed on the surface of the EUV collector mirror 23. The EUV collector mirror 23 is preferably arranged such that, for example, the first focal point thereof is located in the plasma generation region 25 and the second focal point thereof is located at the intermediate focal point (IF) 292. A through hole 24 may be provided at the center of the EUV collector mirror 23, and the pulse laser beam 33 may pass through the through hole 24.

  The EUV light generation apparatus 1 may include an EUV light generation control unit 5, a target sensor 4, and the like. The target sensor 4 may have an imaging function and may be configured to detect at least one of the presence, locus, position, and speed of the target 27. Target 27 may also be referred to as droplet 27.

  Further, the EUV light generation apparatus 1 may include a connection unit 29 that allows the inside of the chamber 2 and the inside of the exposure apparatus 6 to communicate with each other. A wall 291 in which an aperture is formed may be provided inside the connection portion 29. The wall 291 may be arranged such that its aperture is located at the second focal position of the EUV collector mirror 23.

  Furthermore, the EUV light generation apparatus 1 may include a laser beam traveling direction control unit 34, a laser beam collector mirror 22, a target collector 28 for collecting the target 27, and the like. The laser beam traveling direction control unit 34 may include an optical element for defining the traveling direction of the laser beam and an actuator for adjusting the position, posture, and the like of the optical element.

3.2 Operation Referring to FIG. 1, the pulsed laser beam 31 output from the laser device 3 passes through the window 21 as the pulsed laser beam 32 through the laser beam traveling direction control unit 34 and enters the chamber 2. May be. The pulse laser beam 32 may travel through the chamber 2 along at least one laser beam path, be reflected by the laser beam collector mirror 22, and be irradiated to the at least one target 27 as the pulse laser beam 33.

  The target supply unit 26 may be configured to discharge the target 27 toward the plasma generation region 25 inside the chamber 2. The target 27 may be irradiated with at least one pulse included in the pulse laser beam 33. The target 27 irradiated with the pulsed laser light is turned into plasma, and radiation light 251 can be emitted from the plasma.

  The EUV light 252 included in the radiation light 251 may be selectively reflected by the EUV collector mirror 23. The EUV light 252 reflected by the EUV collector mirror 23 may be condensed at the intermediate condensing point 292 and output to the exposure apparatus 6. A single target 27 may be irradiated with a plurality of pulses included in the pulse laser beam 33.

  The EUV light generation controller 5 may be configured to control the entire EUV light generation system 11. The EUV light generation controller 5 may be configured to process image data of the target 27 imaged by the target sensor 4. Further, the EUV light generation controller 5 may be configured to control, for example, the timing at which the target 27 is supplied, the output direction of the target 27, and the like.

  Further, the EUV light generation control unit 5 is configured to perform at least one of, for example, control of the light emission timing of the laser device 3, control of the traveling direction of the pulse laser light 32, and control of the focusing position of the pulse laser light 33. May be. The various controls described above are merely examples, and other controls may be added as necessary.

4). Comparative Example of Laser Device Including Master Oscillator and Optical Amplifier 4.1 Configuration of Laser Device FIG. 2 schematically shows a comparative example of the laser device. The laser device 3 may include a master oscillator (MO) 350 and optical amplifiers 351_1 to 351_N. The master oscillator 350 may be, for example, a laser oscillator including a Q switch, a CO ₂ laser gas medium, and an optical resonator. Alternatively, the master oscillator 350 may be a quantum cascade laser that oscillates at a wavelength in the gain region of the CO ₂ laser. The pulsed laser light output from the master oscillator 350 may be linearly polarized light.

  The optical amplifiers 351_1 to 351_N may be arranged in series on the optical path of the pulse laser beam output from the master oscillator 350, and sequentially amplify the pulse laser beam output from the master oscillator 350. The optical amplifiers 351_1 to 351_N may be first to Nth stage optical amplifiers. The number of stages of the optical amplifier may be one or more and may vary depending on the design.

Each of the optical amplifiers 351_1 to 351_N may be a discharge excitation type optical amplifier using a CO ₂ laser gas as a medium. Each of the optical amplifiers 351_1 to 351_N may include a CO ₂ laser gas, a pair of electrodes, and a power source that performs high-frequency discharge between the pair of electrodes. One or more of the optical amplifiers 351_1 to 351_N may be optical amplifiers that perform multipath amplification. The optical amplifier that performs multipath amplification may be a slab type optical amplifier. In the example of FIG. 2, at least the optical amplifier 351_1 may be a slab type optical amplifier.

  When the master oscillator 350 is a device with a small output (several tens of mW) such as a QCL, an optical resonator, an EO (Electro-Optic) Pockels cell, and a polarizer are included in front of the first stage optical amplifier 351_1. A regenerative amplifier may be arranged. An optical isolator may be disposed between the master oscillator 350 and the optical amplifier 351_1, between each of two consecutive optical amplifiers, and / or on an optical path downstream of the optical amplifier 351_N.

4.2 Operation of Laser Device Each of the optical amplifiers 351_1 to 351_N may be discharged by applying a potential between electrodes by a power source (not shown). The master oscillator 350 may oscillate at a predetermined repetition frequency.

Each of the optical amplifiers 351_1 to 351_N may generate a high frequency discharge by a power source (not shown) and pump CO ₂ laser gas. Thereby, the excitation intensity of the optical amplifiers 351_1 to 351_N can be a predetermined value. The optical amplifiers 351_1 to 351_N may excite the CO ₂ laser gas by generating a discharge between the electrodes even when the laser light is not incident from the master oscillator 350.

  The laser light output from the master oscillator 350 can be amplified by entering the optical amplifier 351_1 and passing through the optical amplifier 351_1. The amplified laser light output from the optical amplifier 351_1 can be further amplified by entering the optical amplifier 351_2 and passing through the optical amplifier 351_2.

  Similarly, laser light output from the optical amplifier 351_K-1 (not shown) can be further amplified by entering the optical amplifier 351_K and passing through the optical amplifier 351_K. The laser light amplified by the optical amplifier 351_N may be collected by the laser light collecting mirror 22 and applied to the target 27 in the chamber 2.

  The target 27 irradiated with the laser light may be turned into plasma to emit EUV light. The EUV light may be collected by the EUV collector mirror 23 and output to the exposure apparatus 6 connected to the chamber 2.

4.3 Configuration of Slab Type Optical Amplifier FIGS. 3A and 3B schematically show a configuration example of a slab type optical amplifier. The slab type optical amplifier may amplify laser light that forms a multipath that repeatedly passes through a slab-shaped amplification region by repeating reflection between opposing reflecting surfaces.

  3A and 3B, the X axis, the Y axis, and the Z axis may be perpendicular to each other. The Z-axis direction may coincide with the optical path direction of the laser beam emitted from the slab type optical amplifier 351_1. The Y-axis direction may coincide with the waveguide direction. The waveguide direction may be the normal direction of the surface of the maximum area of the slab amplification region 514. The arbitrary in-plane direction of the XZ plane may be a free space direction.

  FIG. 3A shows a cross-sectional view of the slab type optical amplifier 351_1 viewed in the X-axis direction. FIG. 3B shows a cross-sectional view of the slab type optical amplifier 351_1 viewed in the Y-axis direction. FIG. 3B shows a change in the optical path due to thermal deformation of the slab type optical amplifier 351_1.

  FIG. 3B (a) shows an optical path in the slab type optical amplifier 351_1 before thermal deformation. FIG. 3B (b) shows the optical path in the slab type optical amplifier 351_1 before thermal deformation by a dotted line, and shows the optical path in the slab type optical amplifier 351_1 after thermal deformation by a solid line. In the description including the following embodiments, a dotted arrow indicates an optical path before change, and a solid arrow indicates an optical path after change. The change of the optical path in the slab type optical amplifier 351_1 will be described later.

  The slab type optical amplifier 351_1 may include a chamber 511 and an RF power source 525. A holder 521 that holds the entrance window 519 and a holder 522 that holds the exit window 520 may be fixed to the outer surface of the chamber 511.

  A pair of plate-like electrodes 512 and 513 may be disposed in the chamber 511 so as to face each other at a predetermined interval, and may be electrically connected to the RF power source 525. The Y-axis direction is perpendicular to the wide surfaces of the electrodes 512 and 513, and the electrodes 512 and 513 may be arranged to face each other in the Y-axis direction. The wide surfaces of the electrodes 512 and 513 may be the widest surfaces of the electrodes 512 and 513. The RF power source 525 may apply a voltage between the electrodes 512 and 513 to generate a discharge in the discharge region 514 between the electrodes 512 and 513. The discharge region may be a slab amplification region.

  A surface on the discharge side of the electrodes 512 and 513 perpendicular to the discharge direction may be called a discharge surface. The discharge surfaces of the electrodes 512 and 513 may be parallel. The discharge direction may be the Y-axis direction, that is, the waveguide direction. The free space direction may be a direction parallel to the discharge surfaces of the electrodes 512 and 513.

A CO ₂ laser gas may be sealed in the chamber 511. The holder 521 that holds the entrance window 519 and the holder 522 that holds the exit window 520 may be sealed at a position on the optical path 311 of the incident light and a position on the optical path 312 of the amplified outgoing light, respectively. Good.

  In the chamber 511, the concave mirrors 515 and 516 may be arranged to face each other at a position sandwiching the discharge region 514. The concave mirrors 515 and 516 may be high reflection mirrors. The concave mirrors 515 and 516 may face each other in the free space direction.

  The concave mirror 515 may be held by the mirror holder 517, and the concave mirror 516 may be held by the mirror holder 518. The mirror holders 517 and 518 may be fixed to the inner surface of the chamber 511. The concave mirrors 515 and 516 may be arranged so that the laser light incident from the incident window 519 is output from the exit window 520 after being multipassed in a zigzag manner in the discharge region 514.

4.4 Operation of Slab Optical Amplifier In FIG. 3B (a), laser light may enter the slab optical amplifier 351_1 through the optical path 311 and be amplified in the discharge region 514. The slab type optical amplifier 351_1 can output the amplified laser beam in the optical path 312. In the slab type optical amplifier 351_1, a voltage may be applied between the pair of electrodes 512 and 513 by the RF power source 525. A discharge occurs between the electrodes 512 and 513, and the CO ₂ laser gas can be excited by the discharge.

  In this state, a pulsed incident laser beam may enter the chamber 511 through the incident window 519 in the optical path 311. The laser light can be amplified through the discharge region 514 and reach the concave mirror 516. The amplified laser light is reflected by the concave mirror 516, further amplified by passing through the discharge region 514, and can reach the concave mirror 515.

  The amplified laser light is reflected by the concave mirror 515 and further amplified by passing through the discharge region 514, and can reach the concave mirror 516. The laser beam amplified by repeating the reflection between the concave mirrors 515 and 516 can travel in a zigzag manner in the discharge region 514 and be multipass amplified. In FIG. 3B, the number of multipaths may be five.

  The laser light amplified at the end of the fifth pass can be output in the optical path 312 via the emission window 520. The outgoing light output from the outgoing window 520 can enter the next-stage apparatus. The incident light of the slab type optical amplifier may be a laser beam output from the master oscillator 350, or may be a laser beam amplified by an optical amplifier arranged in front of the slab type optical amplifier.

5. Problems in Comparative Example of Laser Device If discharge is continuously generated between the electrodes 512 and 513 by the RF power source 525, the chamber 511 can be deformed by receiving heat from the discharge. The inventors have found that the optical path 312 of the emitted light can be greatly moved in the free space direction by deformation of the chamber 511. In particular, it has been found that the translation component in the free space direction can be large.

  For example, as shown in FIG. 3B (b), as the chamber 511 expands, the concave mirrors 515 and 516 fixed to the chamber 511 via the mirror holders 517 and 518 move, and the space between the concave mirrors 515 and 516 is increased. The distance can be extended.

  When the distance between the concave mirrors 515 and 516 is extended, the reflection position of the laser light incident thereon can be displaced. As a result, the optical path of the emitted light emitted from the slab type optical amplifier 351_1 can be translated in the free space direction in the XZ plane. In FIG. 3B (b), the optical path of the emitted light can be translated from the optical path 312 to the optical path 315. As a result, the laser beam may not be incident on the next-stage apparatus through an appropriate optical path.

  For example, when the outgoing light whose optical path has moved in parallel is further amplified by the next-stage optical amplifier 351_2, vignetting of the laser light may occur in the incident portion of the next-stage optical amplifier 351_2 or in the optical path inside the next-stage optical amplifier 351_2. As a result, part or all of the amplified light is not emitted from the next-stage optical amplifier 351_2, the amplification factor of the laser device 3 is reduced, and the laser device 3 may not function properly.

  Here, in order to correct the optical path translated in the free space direction, an optical path correction mechanism for adjusting the angle of the high reflection mirror can be used. However, the optical path correction mechanism may require a high-reflection mirror capable of adjusting at least two angles.

  FIG. 4 shows an angle adjustment example of two high reflection mirrors for correcting an optical path translated in the free space direction. In FIG. 4, the light emitted from the slab type optical amplifier 351 </ b> _ <b> 1 can be reflected by the second high reflection mirror 402 after being reflected by the first high reflection mirror 401. The optical path correction may be performed by adjusting the angle of each of the two high reflection mirrors 401 and 402.

  In FIG. 4, the optical path of the emitted light from the slab type optical amplifier 351_1 can change from the optical path 312 to the optical path 315. In FIG. 4, the angles of the two high reflection mirrors 401 and 402 may be changed clockwise. As a result, the optical path of the reflected light of the high reflection mirror 402 can coincide with the optical paths 312 and 315. However, this optical path correction mechanism needs to accurately adjust the angles of the two high reflection mirrors 401 and 402, and may require complicated control.

6). Embodiment 1: Laser device including optical path correction mechanism (mirror control of optical path correction mechanism)
6.1 Configuration of Laser Device FIG. 5 schematically illustrates a partial configuration of the laser device 3 according to the first embodiment. The laser device 3 of the present embodiment may include the configuration shown in FIG. 5 in the laser device configuration shown in FIG. The laser device 3 may include an optical path correction mechanism 450 disposed on the optical path of the laser light output from the slab optical amplifier 351_1, and a high reflection mirror 481 disposed on the downstream side of the optical path correction mechanism 450. . The position and posture of the high reflection mirror 481 may be fixed, and the high reflection mirror 481 may be omitted.

  The optical path correction mechanism 450 may be disposed on the optical path of the laser light between the slab type optical amplifier 351_1 and the next-stage optical device, and may correct the optical path of the laser light. The next-stage optical device may be, for example, an optical isolator or an optical amplifier 351_2.

  The controller 526 may be electrically connected to the RF power source 525 and the optical path correction mechanism 450. The controller 526 may include a processor and / or hardware logic that operates according to a program stored in memory. The controller 526 may include a timer realized by a processor or a dedicated circuit.

  The optical path correction mechanism 450 may include a high reflection mirror 451. The high reflection mirror 451 can reflect the light emitted from the slab type optical amplifier 351_1, and the high reflection mirror 481 can reflect the laser light reflected by the high reflection mirror 451. The incident angle of the laser light on the high reflection mirrors 451 and 481 may be about 45 °, but is not limited thereto.

  The optical path correction mechanism 450 may be configured to translate the highly reflective mirror 451 along one axis in response to a command from the controller 526. The optical path correction mechanism 450 may move the high reflection mirror 451 in a specific free space direction.

6.2 Operation of Laser Device As described above, the optical path in the slab type optical amplifier 351_1 can move due to thermal deformation of the slab type optical amplifier 351_1 due to discharge. Therefore, the controller 526 may move the high reflection mirror 451 based on the elapsed time from the start of discharge. The discharge start time may be a startup time.

  For example, the controller 526 may detect the start of discharge based on a signal from the RF power source 525, and measure the elapsed time from the detected discharge start time using a timer. The controller 526 may instruct the optical path correction mechanism 450 to move the high reflection mirror 451 from the initial position based on the time measured by the timer.

  The controller 526 may hold in advance relationship information indicating the relationship between the measurement time of the timer and the amount of movement of the high reflection mirror 451 from the initial position. The relationship information may be represented by a table or a function, for example. The relationship information may be a result measured by prior measurement. In general, the movement amount from the initial position increases from the start of discharge, and can be maintained at the same value after a predetermined time has elapsed.

  The optical path correction mechanism 450 may move the high reflection mirror 451 in accordance with a command from the controller 526. The optical path correction mechanism 450 may move the high reflection mirror 451 so that the optical path of the reflected light of the high reflection mirror 451 is constant. In FIG. 5, the optical path of the emitted light from the slab type optical amplifier 351_1 is the optical path 312 at the start of discharge, and can change to the optical path 315 with the passage of time. The optical path correction mechanism 450 may translate the high reflection mirror 451 in parallel with the change of the optical path to the downstream side of the emitted light in the specific free space direction.

  Further, the controller 526 may detect the end of the discharge based on a signal from the RF power source 525 and may instruct the optical path correction mechanism 450 to move the high reflection mirror 451 to the initial position. The optical path correction mechanism 450 may move the high reflection mirror 451 to the initial position in response to a command from the controller 526.

6.3 Configuration and Operation of Optical Path Correction Mechanism FIGS. 6A and 6B schematically show the configuration of the optical path correction mechanism 450. 6A is a top view and FIG. 6B is a perspective view. The optical path correction mechanism 450 may include a high reflection mirror 451, a mirror holder 452, a single axis stage 458, and a linear motion actuator 455. The uniaxial stage 458 may include an installation unit 453 that is fixed and a moving unit 454 that is movably disposed on the installation unit 453. The moving unit 454 may be movable in both directions along one axis on the installation unit 453.

  The mirror holder 452 may hold the high reflection mirror 451. The mirror holder 452 may include a gimbal mechanism for finely adjusting the holding angle of the high reflection mirror 451. The mirror holder 452 may be fixed on the moving unit 454. The high reflection mirror 451 held by the mirror holder 452 can highly reflect the laser beam.

  The linear actuator 455 may have an arm 456 that is linearly displaced. The arm 456 may be fixed to the moving unit 454, and the moving unit 454 may be translated in the uniaxial direction with respect to the installation unit 453. In another configuration, the arm 456 may contact the moving unit 454, and a spring fixed to the installation unit 453 may apply a force to the moving unit 454 so that the moving unit 454 and the arm 456 are always in contact.

  The linear actuator 455 may be electrically connected to the controller 526 and driven by a signal from the controller 526. The linear actuator 455 may incorporate an encoder that measures the amount of displacement of the arm 456 from the initial position, and may transmit the measured amount of displacement to the controller 526.

6.4 Mirror Movement Direction of Optical Path Correction Mechanism FIGS. 7A and 7B show an example of a method for moving the high reflection mirror 451 by the optical path correction mechanism 450. 7C and 7D show an example of a method of moving the high reflection mirror 481 in place of the high reflection mirror 451.

  The optical path correction mechanism 450 may translate the high reflection mirror 451 in a specific free space direction. The free space direction is parallel to the discharge surfaces of the electrodes 512 and 513 of the slab optical amplifier 351_1 and may be a direction in the XZ plane.

  The optical path correction mechanism 450 moves the high reflection mirror 451 in a specific free space direction according to the change in the optical path of the incident light to the high reflection mirror 451 so that the optical path of the reflected light by the high reflection mirror 451 is constant. May be.

  In FIG. 7A and FIG. 7B, the optical path of the incident light to the high reflection mirror 451 can change from the optical path 312 to the optical path 315. Therefore, for example, in FIG. 7A, the high reflection mirror 451 may move parallel to the incident direction of the incident light. In FIG. 7B, the high reflection mirror 451 may move perpendicular to the incident direction of the incident light. The high reflection mirror 451 may move in a direction including a component parallel to a component perpendicular to the incident direction of incident light.

  As shown in FIGS. 7C and 7D, the optical path correction mechanism 450 may include a high reflection mirror 481 instead of the high reflection mirror 451. The position and posture of the high reflection mirror 451 may be fixed. The high reflection mirror 481 may be translated in a specific free space direction according to a change in the optical path of the incident light so that the optical path of the reflected light by the high reflection mirror 481 is constant.

  For example, in FIG. 7C, the high reflection mirror 481 may move parallel to the incident direction of the incident light. In FIG. 7D, the high reflection mirror 481 may move perpendicular to the incident direction of the incident light. The high reflection mirror 481 may move in a direction including a component parallel to a component perpendicular to the incident direction of incident light.

  As described above, according to the present embodiment, the changed optical path in the slab optical amplifier can be corrected appropriately. By moving one high reflection mirror in the free space direction, the optical path can be corrected with a simple configuration and easy control.

7). Embodiment 2: Laser device including temperature correction mechanism (temperature detection)
Hereinafter, the laser device according to the second embodiment will be described. In the present embodiment, differences from the first embodiment will be mainly described.

7.1 Configuration FIG. 8 schematically shows a partial configuration of the laser apparatus 3 of the present embodiment. The laser device 3 may include a temperature sensor 527 that measures the temperature of the slab type optical amplifier 351_1. The temperature sensor 527 may be fixed to the outer surface or the inner surface of the chamber 511, for example.

  The controller 526 may be electrically connected to the temperature sensor 527. The controller 526 may not be electrically connected to the RF power source 525. Controller 526 may not include a timer.

7.2 Operation The temperature sensor 527 may detect the wall surface temperature of the chamber 511 and output it to the controller 526. The controller 526 may command the movement position of the high reflection mirror 451 to the optical path correction mechanism 450 based on the temperature detected by the temperature sensor 527.

  The optical path correction mechanism 450 may move the high reflection mirror 451 in response to a command from the controller 526. The optical path correction mechanism 450 may translate the high reflection mirror 451 in a specific free space direction so that the optical path of the reflected light of the high reflection mirror 451 is constant.

  The controller 526 may instruct the optical path correction mechanism 450 based on the temperature detected by the temperature sensor 527, the amount of movement of the high reflection mirror 451 from the initial position. The optical path correction mechanism 450 may move the high reflection mirror 451 based on a command from the controller 526.

  The controller 526 may hold in advance relationship information indicating the relationship between the temperature detected by the temperature sensor 527 and the amount of movement of the high reflection mirror 451 from the initial position. The relationship information may be represented by a table or a function, for example. The information may be a result measured by prior measurement.

7.3 Modification The controller 526 may estimate the temperature of the chamber 511 from the operating parameters of the RF power source 525 without using the temperature sensor 527. The operating parameter may be, for example, an RF voltage or a duty. The controller 526 may be electrically connected to the RF power source 525 and obtain values of operating parameters from the RF power source 525.

  The controller 526 may hold in advance relationship information indicating the relationship between the value of the operation parameter and the temperature of the chamber 511. The controller 526 may hold in advance relationship information indicating the relationship between the value of the operation parameter and the amount of movement of the high reflection mirror 451 from the initial position. The information may be a result measured by prior measurement. The controller 526 may command the amount of movement of the high reflection mirror 451 from the initial position from the relationship information held and the value of the operation parameter acquired from the RF power source 525.

  According to the present embodiment, by controlling the position of the high reflection mirror 451 based on the temperature of the slab type optical amplifier 351_1, the optical path that changes due to thermal deformation of the slab type optical amplifier 351_1 can be corrected more accurately.

8). Embodiment 3: Laser apparatus including beam path correction mechanism (beam profile measurement)
Hereinafter, the laser device according to the third embodiment will be described. In the present embodiment, differences from the first embodiment will be mainly described.

8.1 Configuration FIG. 9 schematically illustrates a partial configuration of the laser apparatus 3 of the present embodiment. The laser device 3 may include a beam sampler 483 disposed on the downstream side of the optical path correction mechanism 450. The beam sampler 483 may be disposed on the optical path between the optical path correction mechanism 450 and the high reflection mirror 481 or may be disposed on the downstream side of the high reflection mirror 481. The beam sampler 483 may reflect part of the laser light reflected by the high reflection mirror 451 as sample light and transmit other components.

  The laser apparatus 3 may include a beam profiler 485 disposed at a position where the sample light from the beam sampler 483 is received. The type of the beam profiler 485 is not limited. For example, a camera beam profiler or a slit beam profiler may be used.

  The controller 526 may be electrically connected to the beam profiler 485 and the optical path correction mechanism 450. The controller 526 may not be electrically connected to the RF power source 525. Controller 526 may not include a timer.

8.2 Operation The controller 526 may store in advance the beam position of the normal optical path in the slab type optical amplifier 351_1. For example, the controller 526 may acquire image data indicating a beam profile from the beam profiler 485 for the laser light output from the master oscillator 350 in a state where the slab type optical amplifier 351_1 is not discharged. The controller 526 may store the acquired beam profile as the beam profile of the normal optical path.

  The controller 526 may calculate the position of the normal beam profile on the image. For example, the controller 526 may calculate the barycentric position of the normal beam profile and store the coordinates of the barycentric position on the image as the beam position of the normal optical path.

  After starting the discharge of the slab type optical amplifier 351_1, the beam sampler 483 may reflect a part of the laser light reflected by the high reflection mirror 451 to the beam profiler 485 as sample light. The beam profiler 485 may observe the beam profile of the received laser beam and output the observed image data to the controller 526.

  For example, the controller 526 may acquire beam profile data from the beam profiler 485 at a predetermined cycle, and repeatedly execute the processing described below. After a predetermined time has elapsed from the start of discharge, the controller 526 may stop the processing described below.

  The controller 526 may calculate the position of the beam profile observed by the beam profiler 485 on the image. For example, the controller 526 may calculate the position of the center of gravity on the image from the observed beam profile, and store the coordinates of the position of the center of gravity on the image as the observed beam position of the current optical path.

  The controller 526 may calculate a shift amount (difference) between the beam position coordinates of the normal optical path and the observation beam position coordinates. The controller 526 may instruct the optical path correction mechanism 450 to move the high reflection mirror 451 based on the calculated deviation amount. The optical path correction mechanism 450 may move the high reflection mirror 451 in accordance with a command from the controller 526.

  The controller 526 may send a command to the optical path correction mechanism 450 to translate the highly reflective mirror 451 so that the beam position deviation amount approaches zero. For example, the controller 526 may hold in advance relationship information indicating the relationship between the beam position shift amount and the movement amount of the high reflection mirror 451. The amount of displacement and the amount of movement can each take a positive or negative value depending on the direction. The relationship information may be represented by a table or a function, for example.

  According to the present embodiment, by controlling the position of the high reflection mirror 451 based on the beam position of the light reflected by the high reflection mirror 451, the optical path changed by the slab type optical amplifier 351_1 can be corrected more accurately. .

9. Embodiment 4: Laser apparatus including optical path correction mechanism (mirror position and mirror angle adjustment)
In the following, the laser device of Embodiment 4 will be described. In the present embodiment, differences from the third embodiment will be mainly described.

9.1 Configuration of Laser Device The optical path correction mechanism of the present embodiment can correct a change in translation and an angle of the optical path in the free space direction. The optical path correction mechanism of this embodiment may adjust the angle of the high reflection mirror by moving the high reflection mirror in parallel in order to correct the change in the optical path in the slab type optical amplifier.

  FIG. 10 schematically shows a partial configuration of the laser device 3 of the present embodiment. The laser device 3 may include an optical path correction mechanism 650 instead of the optical path correction mechanism 450 of the third embodiment. The laser apparatus 3 may include a beam sampler 484 on the downstream side of the beam sampler 483. As described above, the laser apparatus 3 may include the two beam samplers 483 and 484 arranged in series on the downstream side of the optical path correction mechanism 650.

  The laser apparatus 3 may include a beam profiler 486 disposed at a position where the sample light from the beam sampler 484 is received. The type of the beam profiler 486 is not limited and may be the same type as the beam profiler 485 or a different type. The controller 526 may be electrically connected to the beam profiler 486 and the optical path correction mechanism 650 in addition to the beam profiler 485.

9.2 Configuration of Optical Path Correction Mechanism FIGS. 11A and 11B schematically show the configuration of the optical path correction mechanism 650. 11A is a top view and FIG. 11B is a side view. The optical path correction mechanism 650 may include a high reflection mirror 451, a mirror holder 452, a single axis stage 458, a linear motion actuator 455, a rotation stage 459, and a linear motion actuator 463.

  The configurations of the single-axis stage 458 and the linear motion actuator 455 may be the same as those in the third embodiment. The rotation stage 459 may be disposed on the uniaxial stage 458. The mirror holder 452 may be disposed on the rotation stage 459. The configuration of the high reflection mirror 451 and the mirror holder 452 may be the same as that of the third embodiment.

  The rotation stage 459 may include an installation unit 462 that is fixed on the moving unit 454 of the single-axis stage 458 and a rotation unit 461 that is rotatably arranged on the installation unit 462. The mirror holder 452 may be fixed on the rotating part 461. The rotation center axis of the rotation unit 461 may be included in the reflection surface of the high reflection mirror 451.

  The linear actuator 463 may include an arm 464 that is linearly displaced. The arm 464 may contact the rotation unit 461 of the rotation stage 459 and rotate the rotation unit 461 relative to the installation unit 462. The optical path correction mechanism 650 may include a spring plunger 465. The spring plunger 465 may apply a force to the rotating unit 461 so that the arm 464 of the linear actuator 463 always contacts the rotating unit 461.

  The linear actuator 463 may be connected to the controller 526 and driven by a signal from the controller 526. The linear actuator 463 may incorporate an encoder that measures the amount of displacement of the arm 464 from the initial position, and may transmit the measured amount of displacement of the arm 464 to the controller 526.

9.3 Operation The controller 526 may store in advance the beam position of the normal optical path in the slab type optical amplifier 351_1 for each of the beam profilers 485 and 486. FIG. 12A shows observed images 811 and 812 and beam profiles 821 and 822 of the normal optical path of the beam profilers 485 and 486.

  For example, the controller 526 may acquire the data of the observed images 811 and 812 from the beam profilers 485 and 486, respectively, for the laser light output from the master oscillator 350 in a state where the slab optical amplifier 351_1 is not discharged. . The observation images 811 and 812 may include beam profiles 821 and 822. The controller 526 may store the acquired beam profiles 821 and 822 as the beam profile of the normal optical path.

  The controller 526 may calculate the positions of the normal beam profiles 821 and 822 on the images 811 and 812 for the beam profilers 485 and 486, respectively. For example, the controller 526 may calculate the centroid position of the normal beam profile 821 acquired from the beam profiler 485 and store the coordinates of the centroid position on the image 811 as the beam position of the normal optical path in the beam profiler 485.

  Further, the controller 526 may calculate the barycentric position of the normal beam profile 822 acquired from the beam profiler 486 and store the coordinates of the barycentric position on the image 812 as the beam position of the normal optical path in the beam profiler 486.

  After starting the discharge of the slab type optical amplifier 351_1, the beam sampler 483 may reflect a part of the laser light reflected by the high reflection mirror 451 to the beam profiler 485 as sample light. The beam profiler 485 may observe the beam profile of the received laser beam and output the observed data to the controller 526.

  The beam sampler 484 may reflect a part of the laser light transmitted through the beam sampler 483 to the beam profiler 486 as sample light. The beam profiler 486 may observe the beam profile of the received laser beam and output the observed data to the controller 526.

  The controller 526 may repeatedly acquire the beam profile data from the beam profilers 485 and 486 and repeatedly execute the processing described below. FIG. 12B shows beam profiles 831 and 832 of the optical path changed by the discharge of the slab type optical amplifier 351_1. In FIG. 12B, a broken line arrow indicates a normal optical path, and a solid line arrow indicates a changed optical path.

  The controller 526 may calculate the position on the image 811 of the beam profile 831 observed by the beam profiler 485. For example, the controller 526 may calculate the barycentric position on the image 811 from the observed beam profile 831 and store the coordinates of the barycentric position on the image 811 as the observed beam position of the current optical path.

  Further, the controller 526 may calculate the position on the image 812 of the beam profile 832 observed by the beam profiler 486. For example, the controller 526 may calculate the barycentric position on the image 812 from the observed beam profile 832 and store the coordinates of the barycentric position on the image 812 as the observed beam position of the current optical path.

  The controller 526 may calculate a deviation amount (difference) D1 between the beam position of the normal optical path in the beam profiler 485 and the observation beam position. Further, the controller 526 may calculate a deviation amount (difference) D2 between the beam position of the normal optical path in the beam profiler 486 and the observation beam position. The shift amounts D1 and D2 may be positive or negative depending on the direction.

  The optical path change may include an angle change component and a translation change component. FIG. 12C equivalently shows the normal optical path and the changed optical path. In FIG. 12C, L1 indicates the distance from the high reflection mirror 451 to the observation point of the beam profiler 485 along the normal optical path. L2 indicates the distance from the high reflection mirror 451 to the observation point of the beam profiler 486 along the normal optical path. L1 and L2 may be measured in advance.

  D 1 indicates the amount of deviation of the beam position observed by the beam profiler 485. D2 indicates the amount of deviation of the beam position observed by the beam profiler 486. θ represents an optical path correction angle by the optical path correction mechanism 650. θ may be positive or negative depending on the direction of deviation.

In FIG. 12C, the relationship of the following formula (1) can be established.
D2-D1 = (L2-L1) tan [theta] (1)
From the equation (1), the following equation (2) can be derived.
θ = tan ⁻¹ ((D2−D1) / (L2−L1)) (2)

  The controller 526 may transmit the correction angle θ of the high reflection mirror 451 calculated by Expression (2) to the optical path correction mechanism 650. The optical path correction mechanism 650 may change the angle of the high reflection mirror 451 by the correction angle θ. The optical path correction mechanism 650 may hold relationship information indicating the relationship between the correction angle θ and the movement amount of the arm 464, and may control the arm 464 according to the relationship information and the correction angle θ.

  FIG. 13A shows a state after the angle correction of the high reflection mirror 451. In FIG. 13A, a broken line arrow indicates a normal optical path, and a solid line arrow indicates an optical path after angle correction. After the angle correction of the high reflection mirror 451, the controller 526 may acquire the profile 831 observed by the beam profiler 485.

  The controller 526 may calculate the position of the acquired beam profile 831 on the image 811. For example, the controller 526 may calculate the barycentric position on the image 811 from the beam profile 831 and store the coordinates of the barycentric position on the image 811 as the observation beam position of the current optical path.

  The controller 526 may calculate a deviation amount (difference) D3 between the beam position of the normal optical path and the observation beam position in the beam profiler 485. The controller 526 may transmit a command for translating the high reflection mirror 451 to the optical path correction mechanism 650 so that the shift amount D3 approaches zero. The optical path correction mechanism 650 may move the optical path by moving the high reflection mirror 451 in parallel. FIG. 13B shows a state after the parallel movement is corrected in addition to the angle correction.

9.4 Modification FIG. 14 schematically illustrates a modification of the optical path correction mechanism in the present embodiment. The laser device 3 may include an optical path correction mechanism 750 instead of the optical path correction mechanism 650. The laser apparatus 3 may further include a high reflection mirror 487 disposed on the optical path between the optical path correction mechanism 750 and the beam sampler 483.

  The optical path correction mechanism 750 may include an angle adjustment actuator unit 752 and a parallel movement actuator unit 751. A high reflection mirror 457 may be disposed on the angle adjustment actuator unit 752. A high reflection mirror 451 different from the high reflection mirror 457 may be disposed in the translation actuator unit 751.

  The angle adjustment actuator unit 752 may perform only the angle adjustment of the high reflection mirror 457 in the free space direction without moving the high reflection mirror 457 in parallel. The translation actuator unit 751 may perform only translation in the free space direction without adjusting the angle of the high reflection mirror 451.

  The outgoing light from the slab type optical amplifier 351_1 may be incident on the high reflection mirror 457. The laser light reflected by the high reflection mirror 457 may enter the high reflection mirror 451. The laser beam reflected by the high reflection mirror 451 may enter the high reflection mirror 487. The laser light reflected by the high reflection mirror 487 may be incident on the beam sampler 483.

  The controller 526 may be electrically connected to the angle adjustment actuator unit 752 and the translation actuator unit 751. The controller 526 may adjust the angle of the high reflection mirror 457 by the same method as the angle adjustment of the high reflection mirror 451 in the optical path correction mechanism 650. The controller 526 may translate the high reflection mirror 451 in the same manner as the parallel movement of the high reflection mirror 451 in the optical path correction mechanism 650.

  In the present embodiment, the optical path can be corrected more accurately by correcting both the parallel movement component and the angle component of the optical path change by the slab type optical amplifier 351_1. The angle adjustment actuator unit 752 may be disposed on the downstream side of the parallel movement actuator unit 751.

  The laser device 3 may correct only the translation component without correcting the angle component of the optical path change. The laser device 3 may include an optical path correction mechanism 450 having the same configuration as that of the third embodiment. The controller 526 may calculate the translation component of the optical path change from the beam positions observed at two points, and move the high reflection mirror 451 so as to correct the translation component.

10. Embodiment 5: Laser apparatus including an optical path correction mechanism (arranged on the input side of a slab type optical amplifier)
Hereinafter, the laser apparatus according to the fifth embodiment will be described. In the present embodiment, differences from the third embodiment will be mainly described. In the present embodiment, the optical path correction mechanism may be arranged on the upstream side of the slab type optical amplifier.

  FIG. 15 shows a partial configuration of the laser apparatus 3 of the present embodiment. The laser device 3 may include an optical path correction mechanism 450 disposed on the optical path of the laser light incident on the slab type optical amplifier 351_1. The laser apparatus 3 may include a high reflection mirror 487 downstream of the slab type optical amplifier 351_1.

  The laser beam reflected by the high reflection mirror 451 may enter the slab type optical amplifier 351_1. The light emitted from the slab type optical amplifier 351_1 may be incident on the high reflection mirror 487. The laser light reflected by the high reflection mirror 487 may be incident on the beam sampler 483. The controller 526 may control the optical path correction mechanism 450 by the same method as in the third embodiment.

  In each configuration of the first and second embodiments, the optical path correction mechanism 450 may be disposed on the optical path of the laser light incident on the slab type optical amplifier 351_1. In the configuration of the fourth embodiment, the optical path correction mechanism 650 may be disposed on the optical path of the laser light incident on the slab type optical amplifier 351_1.

11. Embodiment 6: Laser apparatus including an optical path correction mechanism (crystal slab type optical amplifier)
11.1 Configuration of Crystal Slab Type Optical Amplifier FIGS. 16A and 16B show a configuration example of a crystal slab type optical amplifier. The crystal slab type optical amplifier is a kind of slab type optical amplifier. 16A is a perspective view, and FIG. 16B is a top view. The crystal slab type optical amplifier 911 includes a crystal slab 614, a cylindrical concave mirror 615, a cylindrical convex mirror 616, and diode laser stacks 612 and 613, which may be mounted on the base plate 617.

Crystal slab 614 may be a slab-shaped amplification region. The crystal slab 614 is a slab-shaped laser medium crystal, and the surface on which laser light enters and exits may be polished. An antireflection film for the wavelength of the laser beam may be formed on the polished surface. The crystal slab 614 may be, for example, an Nd: YVO ₄ crystal.

  The diode laser stacks 612 and 613 may be composed of a plurality of laser diodes. For example, the diode laser stacks 612 and 613 may be disposed on the end face of the crystal slab 614 other than the end face where the laser light to be amplified enters and exits. The diode laser stacks 612 and 613 may be connected to a power source (not shown). The oscillation wavelength of the diode laser stacks 612 and 613 may be, for example, 808 nm.

  The cylindrical concave mirror 615 and the cylindrical convex mirror 616 may be disposed to face each other with the crystal slab 614 interposed therebetween. The cylindrical concave mirror 615 and the cylindrical convex mirror 616 may be arranged so that laser light incident on the crystal slab 614 is output from the crystal slab 614 in a zigzag manner in the crystal slab 614.

  The free space direction can be any direction in the plane in which the laser light travels within the crystal slab 614. The surface on which the laser light travels can be parallel to the wide surface of the crystal slab 614. The wide surface can be the surface of the largest area of the crystal slab 614. The free space direction may be perpendicular to the plane on which the laser beam of the crystal slab 614 enters and exits. The waveguide direction can be a direction perpendicular to the plane in which the laser light travels within the crystal slab 614. The wave guide direction may be parallel to the surface of the crystal slab 614 where the laser light enters and exits.

11.2 Operation of Crystal Slab Optical Amplifier When power is supplied from a power supply (not shown), the diode laser stacks 612 and 613 are excited, and the excitation laser light can be emitted into the crystal slab 614. Thereby, the crystal slab 614 can be excited. The emission start time of the excitation laser beam may be the activation time.

  When laser light 618 enters the crystal slab 614 in an excited state from the outside, the laser light can be amplified in the crystal slab 614. Amplified laser light 619 can be output from the crystal slab 614. The laser light can travel in a zigzag manner between the cylindrical concave mirror 615 and the cylindrical convex mirror 616 and can be multipass amplified. The laser beam may be amplified between the cylindrical concave mirror 615 and the cylindrical convex mirror 616 while the beam cross-sectional area is expanded in the free space direction.

11.3 Problems of crystal slab type optical amplifier The crystal slab 614 is heated by the excitation laser from the diode laser stacks 612 and 613 and the heat generated when the laser light to be amplified enters the crystal slab 614, and the crystal slab is placed. The base plate 617 can expand. Accordingly, the distance between the cylindrical concave mirror 615 fixed to the base plate 617 and the cylindrical convex mirror 616 can be extended.

  As a result, the optical path of the amplified light emitted from the crystal slab type optical amplifier 911 can move in parallel. Further, the optical path can move due to thermal expansion and refractive index fluctuation accompanying the temperature fluctuation of the crystal slab 614.

11.4 Laser Device Including Optical Path Correction Mechanism FIG. 17 schematically shows a part of a configuration example of a laser apparatus 372 including a correction mechanism for correcting an optical path change in a crystal slab optical amplifier. The laser device 372 may include a crystal slab type optical amplifier 911, an optical path correction mechanism 920, high reflection mirrors 931 and 933, a beam sampler 932, a beam profiler 922, and a controller 950. Dashed arrows indicate the optical path before the change, and solid arrows indicate the optical path after the change.

  The optical path correction mechanism 920 may be disposed on the output side of the crystal slab type optical amplifier 911. The optical path correction mechanism 920 may include a high reflection mirror 921. The optical path correction mechanism 920 may have the same configuration as the optical path correction mechanism 450 shown in FIGS. 6A and 6B.

  The high reflection mirror 931 may reflect the laser light reflected by the high reflection mirror 921. The beam sampler 932 may be disposed on the downstream side of the high reflection mirror 921, reflect a part of the reflected light from the high reflection mirror 921 as sample light, and transmit other components. The high reflection mirror 933 may reflect the laser light transmitted through the beam sampler 932 on the downstream side of the beam sampler 932.

  The beam profiler 922 may be disposed at a position where sample light from the beam sampler 932 is received. The type of the beam profiler 922 is not limited. The controller 950 may be electrically connected to the optical path correction mechanism 920 and the beam profiler 922. The controller 950 may control the optical path correction mechanism 920 based on the beam profile acquired from the beam profiler 922 by a method similar to the method described in the third embodiment.

  According to the present embodiment, the optical path change in the crystal slab type optical amplifier 911 can be corrected appropriately. The other optical path correction configurations in the first to fifth embodiments can also be applied to the correction of the optical path change of the crystal slab type optical amplifier 911.

12 Embodiment 7: Laser apparatus including main pulse laser apparatus and pre-pulse laser apparatus 12.1 Configuration of laser apparatus FIG. 18 schematically shows the configuration of the laser apparatus 3 of the present embodiment. The laser device 3 may include a main pulse laser device 371, a pre-pulse laser device 372, a beam combiner 951, and a laser device controller 373. The main pulse laser device 371 and the pre-pulse laser device 372 may each include an optical path correction mechanism for correcting an optical path change in the slab type optical amplifier.

The main pulse laser device 371 may have the configuration shown in FIGS. The prepulse laser apparatus 372 may include a prepulse master oscillator (PMO) 901 in addition to the configuration shown in FIG. The prepulse master oscillator 901 can be a master oscillator in the prepulse laser apparatus 372. The prepulse master oscillator 901 may be, for example, a laser oscillator including a Nd: YVO ₄ crystal or a diode-pumped mode-locked laser.

  The beam combiner 951 may be disposed at a position where the optical path of the main pulse laser light output from the main pulse laser apparatus 371 and the optical path of the prepulse laser light output from the prepulse laser apparatus 372 intersect. The beam combiner 951 may include a substrate that transmits the main pulse laser beam with high transmittance. The substrate may be formed of diamond, for example.

  A thin film that suppresses reflection of the main pulse laser beam may be formed on the surface of the beam combiner 951 on which the main pulse laser beam is incident. A reflective film that reflects the prepulse laser light with high reflectance may be formed on the surface of the beam combiner 951 on which the prepulse laser light is incident.

  The laser device controller 373 may be connected to the master oscillator 350 and the prepulse master oscillator 901 and configured to control the oscillation timing of the master oscillator 350 and the prepulse master oscillator 901.

12.2 Operation of Laser Device The laser device controller 373 may cause the prepulse master oscillator 901 to oscillate. The prepulse laser beam output from the prepulse master oscillator 901 may be amplified by the crystal slab type optical amplifier 911. The optical path correction mechanism 920 may correct a change in the optical path in the crystal slab type optical amplifier 911. The operation of the optical path correction mechanism 920 may be as described with reference to FIG.

  The laser device controller 373 may cause the master oscillator 350 to perform laser oscillation. The operation of the main pulse laser device 371 may be as described with reference to FIGS. 1 and 9, for example.

  The prepulse laser beam may be reflected by the beam combiner 951, guided to the laser beam collector mirror 22, collected, and applied to the target 27 in the chamber 2. The target 27 irradiated with the pre-pulse laser beam may be diffused in a mist shape.

  The laser apparatus controller 373 outputs the main pulse laser beam from the master oscillator 350 so that the target pulse 27 is irradiated with the main pulse laser beam after a predetermined time has elapsed since the pre-pulse laser beam was irradiated onto the target 27. The timing may be controlled.

  The main pulse laser beam output from the main pulse laser device 371 may pass through the beam combiner 951, be condensed by the laser beam focusing mirror 22, and be irradiated to the diffused target 27. The diffused target 27 may be turned into plasma by irradiation with main pulse laser light. EUV light may be emitted from the plasma. The EUV light may be collected by the EUV collector mirror 23 and output to the exposure apparatus 6 (see FIG. 1) connected to the chamber 2.

  According to this embodiment, in each of the main pulse laser device 371 and the prepulse laser device 372, the optical path change in the slab type optical amplifier can be appropriately corrected. Note that an optical path correction mechanism may be mounted on only one of the main pulse laser device 371 and the pre-pulse laser device 372. The main pulse laser device 371 and the prepulse laser device 372 may include a plurality of optical path correction mechanisms.

  One or more of Embodiments 1 to 6 in this specification may be applied to the main pulse laser device 371 and the prepulse laser device 372. The same optical path correction method may be applied to the main pulse laser device 371 and the prepulse laser device 372, or different optical path correction methods may be applied. The laser apparatus described in this specification may be applied to a system different from the extreme ultraviolet light generation system. The optical path correction mechanism may change the angle of the high reflection mirror by translating the high reflection mirror by manual operation without using the controller.

  Although the present invention has been described with reference to the embodiments, the above description is intended to be illustrative only and not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the embodiments of the present disclosure without departing from the scope of the claims.

  A part of the configuration of one embodiment may be replaced with the configuration of another embodiment. The configuration of another embodiment can be added to the configuration of one embodiment. A part of the configuration of each embodiment may be deleted, added with another configuration, or replaced with another configuration.

  Terms used throughout this specification and the appended claims should be construed as "non-limiting" terms. For example, the terms “include” or “included” should be interpreted as “not limited to those described as included”. The term “comprising” should be interpreted as “not limited to what is described as having”. Also, the modifier “one” in the specification and the appended claims should be interpreted to mean “at least one” or “one or more”.

3 Laser device, 23 EUV light collector mirror, 26 Target supply unit, 27 Target, 350 Master oscillator, 351_1, 911 Slab type optical amplifier, 371 Main pulse laser device, 372 Pre-pulse laser device, 450, 650, 750, 920 Optical path Correction mechanism, 451, 457, 921 High reflection mirror, 483, 484, 932 Beam sampler, 485, 486, 922 Beam profiler, 526 controller, 901 Prepulse master oscillator

  An example laser device of the present disclosure includes an oscillator that outputs laser light, a slab optical amplifier that amplifies and outputs the laser light output from the oscillator by passing through a slab-shaped optical amplification region, and A mirror disposed on the optical path of laser light input to the slab optical amplifier or laser light output from the slab optical amplifier, an optical path correction mechanism that adjusts the mirror to correct the optical path, and the optical path correction And a controller for controlling the mechanism. The controller may determine an adjustment amount of the mirror based on an elapsed time since the activation of the slab type optical amplifier.

Claims (2)

An oscillator that outputs laser light;
A slab optical amplifier that amplifies and outputs the laser light output from the oscillator by passing through a slab-shaped optical amplification region;
A mirror disposed on an optical path of laser light input to the slab type optical amplifier or laser light output from the slab type optical amplifier and moving in a direction parallel to the laser traveling plane in the slab type optical amplifier; A laser device comprising:
An optical path correction mechanism that includes the mirror and moves the mirror;
A controller for controlling the optical path correction mechanism,
The controller is
By controlling the optical path correction mechanism and translating the mirror in a direction parallel to the laser traveling plane, the translation component of the optical path change in the slab optical amplifier is corrected,
A laser apparatus that determines a moving amount of the mirror based on a temperature of the slab type optical amplifier. An oscillator that outputs laser light;
A slab optical amplifier that amplifies and outputs the laser light output from the oscillator by passing through a slab-shaped optical amplification region;
A mirror disposed on an optical path of laser light input to the slab type optical amplifier or laser light output from the slab type optical amplifier and moving in a direction parallel to the laser traveling plane in the slab type optical amplifier; A laser device comprising:
An optical path correction mechanism that includes the mirror and moves the mirror;
A controller for controlling the optical path correction mechanism,
The controller is
By controlling the optical path correction mechanism and translating the mirror in a direction parallel to the laser traveling plane, the translation component of the optical path change in the slab optical amplifier is corrected,
A laser device that determines the amount of movement of the mirror based on an elapsed time from activation of the slab type optical amplifier.

Images