Gas laser device and method of manufacturing an electronic device

Abstract

A gas laser device has a laser oscillator including a pair of discharge electrodes disposed opposite each other and generating light with a laser gas by applying a voltage, and a laser side resonator that resonates the light, an amplifier including an amplifying section and an amplifying side resonator, a beam splitter that reflects a part of the light from the laser side resonator, a light sensor that detects the light reflected by the beam splitter, and a processor that controls the voltage based on an output of the light sensor. The amplifying side resonator includes a back mirror and an amplifying side output coupling mirror, and the laser side resonator includes a grating and a laser side output coupling mirror. In a case where the voltage is lower than a threshold value of the voltage, the processor maintains the voltage at a fixed value above the threshold value.

Description

Technical Field

[0001] This disclosure relates to methods for manufacturing gas laser devices and electronic components. Background Technology

[0002] In recent years, with the miniaturization and high integration of semiconductor integrated circuits, there has been a demand for higher resolution in semiconductor exposure equipment. Therefore, the use of shorter wavelengths of light emitted from exposure light sources has been developed. For example, as gas laser devices for exposure, KrF excimer lasers using lasers with an output wavelength of approximately 248.0 nm and ArF excimer lasers using lasers with an output wavelength of approximately 193.4 nm are examples.

[0003] The naturally oscillating light from KrF and ArF excimer lasers has a relatively wide spectral linewidth, approximately 350 pm to 400 pm. Therefore, when using projection lenses made of materials that allow ultraviolet light to pass through KrF and ArF lasers, chromatic aberration sometimes occurs. As a result, resolution may be reduced. Therefore, it is necessary to narrow the spectral linewidth of the laser output from the gas laser device to a level that eliminates chromatic aberration. Thus, in the laser resonator of a gas laser device, a line-narrowing module (LNM) containing narrowing elements (etalon, grating, etc.) is sometimes included to narrow the spectral linewidth. Hereinafter, gas laser devices with narrowed spectral linewidths will be referred to as narrow-bandgap gas laser devices.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 4364757

[0007] Patent Document 2: Japanese Patent No. 5513653

[0008] Patent Document 3: US Patent No. 7,382,816 Summary of the Invention

[0009] One aspect of the gas laser device disclosed herein may also include: a laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite to each other and generating light using laser gas by applying a voltage, the laser-side resonator causing the light to resonate; an amplifier comprising an amplification section for amplifying light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; a beam splitter for reflecting a portion of the light from the laser-side resonator; a light sensor for detecting the light reflected by the beam splitter; and a processor for controlling the voltage based on the output of the light sensor, the amplification-side resonator comprising: a rear mirror for transmitting a portion of the light from the laser-side resonator, causing the light from the laser-side resonator to resonate. Another portion of the light from the amplification unit is reflected toward the laser-side resonator, causing a portion of the light amplified by the amplification unit to pass through the laser-side resonator, and causing another portion of the light amplified by the amplification unit to be reflected; and an amplification-side output coupling mirror, which reflects a portion of the light amplified by the amplification unit, and causes another portion of the light amplified by the amplification unit to pass through. The laser-side resonator includes: a grating, which reflects the light generated by the laser gas; and a laser-side output coupling mirror, which reflects a portion of the light generated by the laser gas, causes another portion of the light generated by the laser gas to pass through the beam splitter, and causes a portion of the light from the rear mirror to be reflected toward the beam splitter. When the voltage is lower than a voltage threshold, the processor maintains the voltage at a fixed value above the threshold.

[0010] One aspect of the gas laser device disclosed herein may also include: a laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite to each other and generating light using laser gas by applying a voltage, the laser-side resonator causing the light to resonate; an amplifier comprising an amplification section for amplifying light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; a beam splitter for reflecting a portion of the light from the laser-side resonator; a light sensor for detecting the light reflected by the beam splitter; and a processor for controlling the voltage based on the output of the light sensor, the amplification-side resonator comprising: a rear mirror for transmitting a portion of the light from the laser-side resonator, causing the light from the laser-side resonator to resonate. Another portion of the light from the amplified part is reflected toward the laser-side resonator, causing a portion of the light amplified by the amplified part to pass through the laser-side resonator, and causing another portion of the light amplified by the amplified part to be reflected; and an amplified-side output coupling mirror, which causes a portion of the light amplified by the amplified part to be reflected, and causes another portion of the light amplified by the amplified part to pass through. The laser-side resonator includes: a grating, which causes the light generated by the laser gas to be reflected; and a laser-side output coupling mirror, which causes a portion of the light generated by the laser gas to be reflected, causing another portion of the light generated by the laser gas to pass through the beam splitter, and causing a portion of the light from the rear mirror to be reflected toward the beam splitter. When the voltage is lower than a voltage threshold, the processor increases the voltage to a predetermined value greater than the threshold.

[0011] One method of manufacturing an electronic device according to this disclosure may also include the following steps: generating laser light using a gas laser device, outputting the laser light to an exposure device, and exposing the laser light on a photosensitive substrate within the exposure device to manufacture the electronic device. The gas laser device comprises: a laser oscillator including a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using laser gas by applying a voltage, the laser-side resonator causing the light to resonate; an amplifier including an amplification section amplifying the light transmitted through the laser-side resonator and an amplification-side resonator causing the light amplified by the amplification section to resonate; a beam splitter reflecting a portion of the light from the laser-side resonator; a light sensor detecting the light reflected by the beam splitter; and a processor controlling the voltage based on the output of the light sensor. The amplification-side resonator includes: Includes: a rear mirror that allows a portion of the light from the laser-side resonator to pass through and another portion of the light from the laser-side resonator to reflect toward the laser-side resonator, allows a portion of the light amplified by the amplification unit to pass through toward the laser-side resonator, and allows another portion of the light amplified by the amplification unit to reflect; and an amplification-side output coupling mirror that allows a portion of the light amplified by the amplification unit to reflect and another portion of the light amplified by the amplification unit to pass through. The laser-side resonator includes: a grating that allows light generated by laser gas to reflect; and a laser-side output coupling mirror that allows a portion of the light generated by laser gas to reflect and another portion of the light generated by laser gas to pass through toward the beam splitter, and allows a portion of the light from the rear mirror to reflect toward the beam splitter. When the voltage is lower than a voltage threshold, the processor maintains the voltage at a fixed value above the threshold.

[0012] One method of manufacturing an electronic device according to this disclosure may also include the following steps: generating laser light using a gas laser device, outputting the laser light to an exposure device, and exposing the laser light on a photosensitive substrate within the exposure device to manufacture the electronic device. The gas laser device comprises: a laser oscillator including a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using laser gas by applying a voltage, the laser-side resonator causing the light to resonate; an amplifier including an amplification section amplifying the light transmitted through the laser-side resonator and an amplification-side resonator causing the light amplified by the amplification section to resonate; a beam splitter reflecting a portion of the light from the laser-side resonator; a light sensor detecting the light reflected by the beam splitter; and a processor controlling the voltage based on the output of the light sensor. The amplification-side resonator includes: Includes: a rear mirror that allows a portion of the light from the laser-side resonator to pass through and another portion of the light from the laser-side resonator to reflect toward the laser-side resonator, allows a portion of the light amplified by the amplification unit to pass through toward the laser-side resonator, and allows another portion of the light amplified by the amplification unit to reflect; and an amplification-side output coupling mirror that allows a portion of the light amplified by the amplification unit to reflect and another portion of the light amplified by the amplification unit to pass through. The laser-side resonator includes: a grating that allows light generated by laser gas to reflect; and a laser-side output coupling mirror that allows a portion of the light generated by laser gas to reflect and another portion of the light generated by laser gas to pass through toward the beam splitter, and allows a portion of the light from the rear mirror to reflect toward the beam splitter. When the voltage is lower than a voltage threshold, the processor increases the voltage to a predetermined value greater than the threshold. Attached Figure Description

[0013] Hereinafter, several embodiments of the present disclosure will be described as simple examples with reference to the accompanying drawings.

[0014] Figure 1 This is a schematic diagram illustrating a general structural example of an electronic device manufacturing apparatus.

[0015] Figure 2 This is a schematic diagram showing the overall general structure of a comparative example gas laser device.

[0016] Figure 3 This is an example diagram showing the control flow of a processor for a comparative example.

[0017] Figure 4 yes Figure 3 The diagram shows the control flow of the processor in the MO oscillation control process.

[0018] Figure 5 yes Figure 3 The diagram shows the control flow of the processor in the PO oscillation control process.

[0019] Figure 6 yes Figure 3 The diagram shows the control flow chart of the processor in the MO energy control process.

[0020] Figure 7 yes Figure 3 The diagram shows the control flow chart of the processor in the PO energy control process.

[0021] Figure 8 This is a graph showing the relationship between the voltage of the pulse power module of the laser oscillator in the comparative example and the timing of voltage changes.

[0022] Figure 9 This is a graph showing the relationship between the voltage of the pulse power module of the laser oscillator in Embodiment 1 and the timing of voltage changes.

[0023] Figure 10 This is a diagram illustrating an example of the control flow diagram of the processor in Embodiment 1.

[0024] Figure 11 yes Figure 10 The diagram shows the control flow of the processor in the MO oscillation control process.

[0025] Figure 12 yes Figure 10 The diagram shows the control flow of the processor in the pull-up control mode of the degradation control mode transfer processing.

[0026] Figure 13 yes Figure 10 The diagram shows the control flow of the processor in the fixed control mode of the degradation control mode transfer process.

[0027] Figure 14 yes Figure 10 The diagram shows the control flow of the processor in the degradation control mode termination determination process.

[0028] Figure 15 This is a graph showing the relationship between the voltage of the pulse power module of the laser oscillator in Embodiment 2 and the timing of voltage changes.

[0029] Figure 16 This is a control flowchart of the processor in the oscillation control process of Implementation Method 2.

[0030] Figure 17 This is a control flowchart of the processor in the degradation control mode transfer process of Implementation Method 2.

[0031] Figure 18 This is a control flowchart of the processor in the degradation control mode termination determination process of Implementation Method 2.

[0032] Figure 19This is a graph showing the relationship between the voltage of the pulse power module of the laser oscillator in Embodiment 3 and the timing of voltage changes.

[0033] Figure 20 This is a control flowchart of the processor in the degradation control mode transfer process of Implementation Method 3.

[0034] Figure 21 This is a control flowchart of the processor in the degradation control mode termination determination process of Implementation Method 3. Detailed Implementation

[0035] 1. Description of the electronic device manufacturing apparatus used in the exposure process of electronic devices

[0036] 2. Description of the comparative gas laser device

[0037] 2.1 Structure

[0038] 2.2 Actions

[0039] 2.3 Research Topic

[0040] 3. Description of the gas laser device in Embodiment 1

[0041] 3.1 Structure

[0042] 3.2 Actions

[0043] 3.3 Functions / Effects

[0044] 4. Description of the gas laser device in Embodiment 2

[0045] 4.1 Structure

[0046] 4.2 Actions

[0047] 4.3 Functions / Effects

[0048] 5. Description of the gas laser device in Embodiment 3

[0049] 5.1 Structure

[0050] 5.2 Actions

[0051] 5.3 Functions / Effects

[0052] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0053] The embodiments described below illustrate several examples of this disclosure and do not limit the scope of this disclosure. Furthermore, the structures and operations described in each embodiment are not necessarily all necessary for the structures and operations of this disclosure. Additionally, the same reference numerals are used to denote the same structural elements, and repeated descriptions are omitted.

[0054] 1. Description of the electronic device manufacturing apparatus used in the exposure process of electronic devices

[0055] Figure 1 This is a schematic diagram illustrating a general structural example of an electronic device manufacturing apparatus used in the exposure process of an electronic device. For example... Figure 1 As shown, the manufacturing apparatus used in the exposure process includes a gas laser device 100 and an exposure device 200. The exposure device 200 includes an illumination optics system 210 and a projection optics system 220. The illumination optics system 210 includes multiple mirrors 211, 212, and 213. The illumination optics system 210 illuminates the mask pattern on the mask stage RT using laser light incident from the gas laser device 100. The projection optics system 220 projects the laser light transmitted through the mask onto a workpiece (not shown) positioned on a workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure device 200 moves the mask stage RT and the workpiece stage WT synchronously and parallelly, thereby exposing the workpiece to laser light reflecting the mask pattern. Through this exposure process, a device pattern is transferred onto a semiconductor wafer, thereby enabling the manufacture of semiconductor devices as electronic devices.

[0056] 2. Description of the comparative gas laser device

[0057] 2.1 Structure

[0058] The gas laser device 100 of the comparative example will be described. Furthermore, the comparative examples disclosed herein are methods known only to the applicant and are not publicly known examples acknowledged by the applicant.

[0059] Figure 2 This is a schematic diagram illustrating the overall general structure of the gas laser device 100 in this example. The gas laser device 100 is, for example, an ArF excimer laser device using a mixture of argon (Ar), fluorine (F2), and neon (Ne). In this case, the gas laser device 100 outputs pulsed laser light with a center wavelength of approximately 193.4 nm. The gas laser device 100 can also be a gas laser device other than an ArF excimer laser device, for example, a KrF excimer laser device using a mixture of krypton (Kr), F2, and Ne. In this case, the gas laser device 100 emits pulsed laser light with a center wavelength of approximately 248.0 nm. Mixtures of Ar, F2, and Ne as laser media, and mixtures of Kr, F2, and Ne as laser media, are sometimes referred to as laser gases.

[0060] The gas laser device 100 in this example includes a housing 110, a laser oscillator 130 as the main oscillator, an optical transmission unit 141, a detection unit 151 as the oscillation side first detection unit, an amplifier 160 as the power oscillator, an optical transmission unit 143, a detection unit 153 as the amplification side second detection unit, a display unit 180, and a processor 190 as the main structures. The laser oscillator 130, optical transmission units 141 and 143, detection units 151 and 153, amplifier 160, display unit 180, and processor 190 are disposed within the internal space of the housing 110.

[0061] The laser oscillator 130 includes a cavity device CH, a charger 41, a pulse power module 43, a narrowband module 60, and an output coupling mirror 70, which serves as the laser-side output coupling mirror, as its main structure.

[0062] exist Figure 2 The image shows the internal structure of the cavity device CH as viewed from a direction approximately perpendicular to the direction of laser travel. The cavity device CH has a housing 30, a pair of windows 31a and 31b, a pair of electrodes 32a and 32b, an insulating portion 33, a feed hole 34, and an electrode holder portion 36 as its main structures.

[0063] A laser gas supply device (not shown) supplies the aforementioned laser gas to the internal space of the housing 30 via piping (not shown), and the housing 30 seals the laser gas within the internal space. The internal space is the space in which light is generated by the excitation of the laser gas.

[0064] Windows 31a and 31b are positioned opposite each other within the housing 30. Window 31a is located on the front side of the laser traveling from the gas laser device 100 toward the exposure device 200 in the same direction of travel, and window 31b is located on the rear side of the same direction of travel. Windows 31a and 31b are tilted at a Brewster angle relative to the direction of laser travel to suppress the reflection of P-polarized light from the laser. Window 31a is disposed in a hole in the front wall of the housing 30, and window 31b is disposed in a hole in the rear wall of the housing 30.

[0065] Electrodes 32a and 32b are positioned along the direction of laser travel, and are arranged opposite each other within the internal space of housing 30. The space between electrodes 32a and 32b in housing 30 is enclosed by windows 31a and 31b. Electrodes 32a and 32b are discharge electrodes used to excite the laser medium via glow discharge. In this example, electrode 32a is the cathode, and electrode 32b is the anode.

[0066] Electrode 32a is supported by insulating portion 33. Insulating portion 33 blocks the opening continuous with housing 30. Insulating portion 33 includes an insulator. Examples of insulators include alumina ceramic, which has low reactivity with F2 gas. Furthermore, a feedthrough 34 made of conductive material is disposed in insulating portion 33. Feedthrough 34 applies the voltage supplied from pulse power module 43 to electrode 32a. Electrode 32b is supported by electrode holder portion 36 and is electrically connected to electrode holder portion 36.

[0067] Charger 41 is a DC power supply device that charges a capacitor (not shown) disposed in pulse power module 43 with a specified voltage. Charger 41 is disposed outside housing 30 and connected to pulse power module 43. Pulse power module 43 includes a switch (not shown) controlled by processor 190. When the switch changes from open to closed under the control of processor 190, pulse power module 43 boosts the voltage applied from charger 41 to generate a pulsed high voltage, which is applied to electrodes 32a and 32b. When the high voltage is applied, the insulation between electrodes 32a and 32b is broken down, resulting in a discharge. The energy of this discharge excites the laser gas inside housing 30 to transition to a higher energy level. Then, when the excited laser gas transitions to a lower energy level, it emits light corresponding to the energy level difference. The emitted light exits to the outside of housing 30 through windows 31a and 31b.

[0068] The narrowband module 60 includes a prism 61, a grating 63, a rotary stage (not shown), and a housing 65. The prism 61, grating 63, and rotary stage are disposed within the interior space of the housing 65. An opening is continuous with the housing 65, and the housing 65 is connected to the rear side of the housing 30 via the opening.

[0069] Prism 61 widens the beam width of light emitted from window 31b, allowing the light to enter the grating 63. Furthermore, prism 61 narrows the beam width of reflected light from the grating 63, causing the light to return via window 31b to the interior space of housing 30. Prism 61 is supported by a rotating stage and rotates via the stage. The rotation of prism 61 changes the angle of incidence of light relative to the grating 63. Therefore, by rotating prism 61, the wavelength of light returning from the grating 63 to housing 30 via prism 61 can be selected. Figure 2 The example shown is a configuration with one prism 61, however, at least one prism is required.

[0070] The surface of the grating 63 is made of a highly reflective material, and multiple grooves are arranged on the surface at predetermined intervals. The grating 63 is a dispersive optical element. The cross-sectional shape of each groove is, for example, a right-angled triangle. Light incident from the prism 61 onto the grating 63 is reflected by these grooves and diffracted in a direction corresponding to the wavelength of the light. The grating 63 is configured in a Littlero configuration so that the angle of incidence of the light incident from the prism 61 onto the grating 63 coincides with the diffraction angle of the diffracted light at the desired wavelength. Thus, light near the desired wavelength returns to the housing 30 via the prism 61.

[0071] The output coupling mirror 70 is positioned opposite the window 31a. A partially reflective film is coated on the output coupling mirror 70. The output coupling mirror 70 allows a portion of the laser light emitted from the housing 30 via the window 31a to pass through, while reflecting the remaining portion back into the interior space of the housing 30 via the window 31a. For example, the reflectivity of the output coupling mirror 70 can be approximately 40% to 60%. The output coupling mirror 70 is, for example, a component with a dielectric multilayer film formed on a calcium fluoride substrate. Furthermore, the output coupling mirror 70 is fixed to the interior space of the optical path tube 70a, which is connected to the front side of the housing 30, via a damper (not shown).

[0072] A laser-side resonator is constructed using a grating 63 and an output coupling mirror 70, which are separated by a housing 30, to resonate the light emitted from the aforementioned laser gas. The housing 30 is positioned in the optical path of the laser-side resonator, and the light emitted from the housing 30 reciprocates between the grating 63 and the output coupling mirror 70. The reciprocating light is amplified each time it passes through the laser gain space between electrodes 32a and 32b. A portion of the amplified light passes through the output coupling mirror 70 as a pulsed laser.

[0073] The optical transmission unit 141 comprises a housing 141a and high-reflectivity mirrors 141b and 141c as its main structures. An opening is formed in the housing 141a at a connection point connected to the optical path tube 70a, through which the housing 141a communicates with the optical path tube 70a. Furthermore, an opening is formed in the housing 141a at a connection point connected to the optical path tube 171a (described later), through which the housing 141a communicates with the optical path tube 171a. The high-reflectivity mirrors 141b and 141c are disposed within the interior space of the housing 141a with their respective tilt angles adjusted. For example, the high-reflectivity mirrors 141b and 141c are constructed by coating a reflective film that highly reflects pulsed laser light onto the surface of a transparent substrate formed of synthetic quartz and calcium fluoride. The high-reflectivity mirrors 141b and 141c are positioned in the optical path of the pulsed laser light from the output coupling mirror 70. The pulsed laser light is reflected by the high-reflectivity mirrors 141b and 141c and travels towards the rear mirror 171 of the amplifier 160. At least a portion of the laser passes through rear mirror 171.

[0074] The detection unit 151 includes a housing 151a, a beam splitter 151b, and a light sensor 151c as its main structures. An opening is continuous with the housing 151a, and the edge of the opening of the housing 151a is connected to it in a manner that surrounds the opening continuous with the housing 141a. Therefore, the housing 151a communicates with the housing 141a through this opening.

[0075] Beam splitter 151b is disposed within the internal space of housing 141a, between high-reflectivity mirrors 141b and 141c, in the optical path of the pulsed laser. Furthermore, beam splitter 151b is configured to be adjacent to an opening in housing 141a that is continuous with the internal space of housing 151a. Beam splitter 151b causes a portion of the pulsed laser light traveling from the output coupling mirror 70 side of laser oscillator 130 and reflected by high-reflectivity mirror 141b to be reflected toward the light-receiving surface of photosensor 151c. Furthermore, beam splitter 151b causes another portion of the pulsed laser light to pass through high-reflectivity mirror 141c with high transmittance.

[0076] A light sensor 151c is disposed within the internal space of the housing 151a. The light sensor 151c measures the pulse energy of the pulsed laser incident on its light-receiving surface. The light sensor 151c is electrically connected to a processor 190 and outputs a signal representing the measured pulse energy to the processor 190. The processor 190 controls the voltage of the electrodes 32a and 32b of the laser oscillator 130 based on this signal.

[0077] Amplifier 160 is an amplifier that amplifies the energy of the pulsed laser output from laser oscillator 130. The basic structure of amplifier 160 is the same as that of laser oscillator 130, and it has a cavity device CH, a charger 41, and a pulse power module 43. Electrodes 32a and 32b of amplifier 160 are amplification sections that amplify the pulsed laser from laser oscillator 130.

[0078] Furthermore, amplifier 160 has a Fabry-Perot type resonator that resonates the pulsed laser amplified by electrodes 32a and 32b of amplifier 160. This resonator is composed of an output coupling mirror 170, which serves as the amplification-side output coupling mirror, and a rear mirror 171. The rear mirror 171 is positioned between window 31b of amplifier 160 and high-reflectivity mirror 141c, while the output coupling mirror 170 is positioned between window 31a of amplifier 160 and high-reflectivity mirror 143b of optical transmission unit 143. For example, the reflectivity of output coupling mirror 170 is approximately 10% to 30%, and the reflectivity of rear mirror 171 is approximately 50% to 90%. The rear mirror 171 allows a portion of the pulsed laser from laser oscillator 130 to pass through towards electrodes 32a and 32b, and allows a portion of the pulsed laser amplified by electrodes 32a and 32b to be reflected towards the space between electrodes 32a and 32b. Furthermore, the output coupling mirror 170 reflects a portion of the pulsed laser amplified by electrodes 32a and 32b toward the space between electrodes 32a and 32b, while allowing another portion of the pulsed laser to pass through. The rear mirror 171 is disposed within the internal space of the optical path tube 171a. The optical path tube 171a is connected to the housing 30 of the amplifier 160 in a manner that surrounds the window 31b of the amplifier 160. The output coupling mirror 170 is disposed within the internal space of the optical path tube 170a. The optical path tube 170a is connected to the housing 30 of the amplifier 160 in a manner that surrounds the window 31a of the amplifier 160.

[0079] The optical transmission unit 143 comprises a housing 143a and high-reflectivity mirrors 143b and 143c as its main structures. An opening is formed in the housing 143a at the connection point connecting to the optical path tube 170a, through which the housing 143a communicates with the optical path tube 170a. Furthermore, an opening is formed in the housing 143a at the connection point connecting to the housing 153a (described later), through which the housing 143a communicates with the housing 153a. The high-reflectivity mirrors 143b and 143c are disposed within the interior space of the housing 143a with their respective tilt angles adjusted. The structures of the high-reflectivity mirrors 143b and 143c are the same as those of the high-reflectivity mirrors 141b and 141c. Laser light passing through the output coupling mirror 170 is reflected by the high-reflectivity mirrors 143b and 143c and travels towards the detection unit 153.

[0080] The detection unit 153 comprises a housing 153a, a beam splitter 153b, and a light sensor 153c as its main structures. An opening is connected to the housing 143a, which surrounds the opening. Therefore, the housing 153a communicates with the housing 143a through this opening. The beam splitter 153b and the light sensor 153c are disposed within the internal space of the housing 153a.

[0081] Beam splitter 153b is positioned in the optical path of the pulsed laser passing through output coupling mirror 170. Beam splitter 153b allows the pulsed laser passing through output coupling mirror 170 to pass through exit window 173 with high transmittance, and causes a portion of the pulsed laser to be reflected toward the light-receiving surface of photosensor 153c.

[0082] Optical sensor 153c measures the pulse energy of pulsed laser light incident on its light-receiving surface. Optical sensor 153c is electrically connected to processor 190 and outputs a signal representing the measured pulse energy to processor 190. Processor 190 controls the voltage of electrodes 32a and 32b of amplifier 160 based on this signal.

[0083] The opening is continuous with the side of the housing 153a in the detection unit 153 opposite to the side connected to the housing 143a, and the optical path tube 173a is connected to surround the opening. Therefore, the housing 153a and the optical path tube 173a are in communication with each other. In addition, the optical path tube 173a is connected to the housing 110. An exit window 173 is provided in the housing 110 at a position surrounded by the optical path tube 173a. Light passing through the beam splitter 153b of the detection unit 153 is emitted from the exit window 173 to the exposure device 200 outside the housing 110.

[0084] The internal spaces of optical path tubes 70a, 170a, 171a, and housings 30, 141a, 143a, 151a, and 153a are filled with purge gas. The purge gas contains inert gases such as high-purity nitrogen with few impurities, including oxygen. The purge gas is supplied to the internal spaces of optical path tubes 70a, 170a, 171a, and housings 30, 141a, 143a, 151a, and 153a from a purge gas supply source (not shown) located outside housing 110 via piping (not shown).

[0085] Display unit 180 is a monitor that displays the status based on the control of processor 190 according to signals from processor 190.

[0086] The processor 190 of this disclosure is a processing device including a storage device storing a control program and a CPU executing the control program. The processor 190 is specifically configured or programmed to perform the various processes included in this disclosure. Furthermore, the processor 190 controls the gas laser device 100 as a whole. Additionally, the processor 190 is electrically connected to an exposure processor (not shown) of the exposure device 200, and sends and receives various signals with and from the exposure processor.

[0087] 2.2 Actions

[0088] Next, the operation of the processor 190 of the comparative example gas laser device 100 will be explained.

[0089] Figure 3 This is an example diagram showing the control flow of the processor 190 in a comparative example. For example... Figure 3 As shown, the control flow of this embodiment includes steps SP11 to SP15. Figure 3 In the initial state shown, the processor 190 receives oscillation indication signals from the laser oscillator 130 and the amplifier 160 from the exposure processor of the exposure apparatus 200.

[0090] (Step SP11)

[0091] In this step, processor 190 moves on to the oscillation control processing of laser oscillator 130, which will be described later. Hereinafter, this processing is sometimes referred to as MO oscillation control processing. After the MO oscillation control processing is completed, processor 190 causes the control flow to proceed to step SP12.

[0092] (Step SP12)

[0093] In this step, processor 190 transfers to the oscillation control processing of amplifier 160, which will be described later. This processing is sometimes referred to as the PO oscillation control processing. After the PO oscillation control processing is completed, processor 190 causes the control flow to proceed to step SP13. Alternatively, processor 190 may cause the control flow to proceed in the order of steps SP12 and SP11, or simultaneously perform steps SP11 and SP12.

[0094] (Step SP13)

[0095] In this step, processor 190 moves on to the energy control processing of laser oscillator 130, which will be described later. This processing is sometimes referred to as MO energy control processing. After the MO energy control processing is completed, processor 190 causes the control flow to proceed to step SP14.

[0096] (Step SP14)

[0097] In this step, processor 190 moves to the energy control processing of amplifier 160, which will be described later. This processing is sometimes referred to as PO energy control processing. After the PO energy control processing is completed, processor 190 causes the control flow to proceed to step SP15. Alternatively, processor 190 may simultaneously perform steps SP13 and SP14.

[0098] (Step SP15)

[0099] In this step, if the processor 190 receives a next oscillation indication signal from the exposure processor of the exposure apparatus 200, it returns the control flow to step SP13. Alternatively, if no next oscillation indication signal is received from the exposure processor, the processor 190 controls the laser oscillator 130 and amplifier 160 to stop the application of voltage, thus ending the control flow. The next oscillation indication signal is the signal following the oscillation indication signal received in the initial state.

[0100] Figure 4 This is the control flowchart of processor 190 in the MO oscillation control process of step SP11. (See attached diagram.) Figure 4 As shown, the control flowchart includes steps SP21 to SP23.

[0101] (Step SP21)

[0102] In this step, processor 190 sets the initial value of the pulse energy EMO0 of the pulsed laser emitted from laser oscillator 130. This light will sometimes be referred to as the MO injection light. After setting the initial value EMO0, processor 190 causes the control flow to proceed to step SP22.

[0103] (Step SP22)

[0104] In this step, the processor 190 sets the initial value VMO0 of the voltage VMO applied to the electrodes 32a and 32b of the laser oscillator 130, so that MO injection light with an initial pulse energy of EMO0 is emitted from the laser oscillator 130. After setting the initial value VMO0, the processor 190 causes the control flow to proceed to step SP23.

[0105] (Step SP23)

[0106] In this step, the processor 190 sets the target value VMOt of the voltage VMO applied to the electrodes 32a and 32b of the laser oscillator 130 to the initial value VMO0. After setting the target value VMOt, the processor 190 terminates the control flow in the MO oscillation control process and causes the control flow to proceed to step SP12.

[0107] Figure 5 This is the control flowchart of processor 190 in the PO oscillation control process of step SP12. (See attached diagram.) Figure 5 As shown, the control flowchart includes steps SP31 to SP33. The PO oscillation control process involves setting the initial value EMO0 in step SP21, the initial value VMO0 in step SP22, and the target value VMOt in step SP23, which are also performed on the amplifier 160 side. Each step will be briefly explained below.

[0108] (Steps SP31, SP32, SP33)

[0109] In step SP31, processor 190 sets the initial value EPO0 of the pulse energy of the pulsed laser emitted from amplifier 160. Hereinafter, this light is sometimes referred to as amplified laser. In step SP32, processor 190 sets the initial value VPO0 of the voltage VPO applied to electrodes 32a and 32b of amplifier 160, so that amplified laser with an initial pulse energy of EPO0 is emitted from amplifier 160. In step SP33, processor 190 sets the target value VPOt of the voltage VPO applied to electrodes 32a and 32b of amplifier 160 to the initial value VPO0.

[0110] After setting the target value VPOt, the processor 190 terminates the control flow in the PO oscillation control process and allows the control flow to proceed to step SP13.

[0111] Figure 6 This is the control flowchart of processor 190 in step SP13's MO energy control processing. (Example) Figure 6 As shown, the control flowchart includes steps SP41 to SP49.

[0112] (Step SP41)

[0113] In this step, the processor 190 sets a target value EMOt for the pulse energy of the MO injection light emitted from the laser oscillator 130. After setting the target value EMOt, the processor 190 causes the control flow to proceed to step SP42.

[0114] (Step SP42)

[0115] In this step, the processor 190 turns on the switch in the pulse power module 43 of the laser oscillator 130. After the switch is turned on, the processor 190 controls the pulse power module 43 to emit MO injection light with a pulse energy of the target value EMOt from the laser oscillator 130. Specifically, the processor 190 controls the pulse power module 43 to apply a voltage VMO to electrodes 32a and 32b at the target value VMOt set in step SP23. The target value VMOt is the value set according to the target value EMOt. After the processor 190 is subjected to the voltage VMO, which is the target value VMOt, the control flow proceeds to step SP43.

[0116] After a voltage VMO, which is the target value VMOt, is applied, the insulation between electrodes 32a and 32b breaks down, resulting in a discharge. The energy from this discharge causes the laser medium contained in the laser gas between electrodes 32a and 32b to enter an excited state, emitting spontaneously emitted light upon returning to its ground state. A portion of this light is ultraviolet and passes through window 31b. The transmitted light is amplified in its direction of travel as it passes through prism 61. Furthermore, the light undergoes wavelength dispersion as it passes through prism 61 and is guided to grating 63. The light is incident on grating 63 at a predetermined angle and diffracts; light of the predetermined wavelength is reflected at grating 63 at the same angle of reflection as the incident angle. The light reflected at grating 63 propagates again through prism 61 from window 31b into the interior space of housing 30. The light propagating into the interior space of housing 30 is narrowed. Through this narrowed light, the excited laser medium undergoes stimulated emission, and the light is amplified. The light then travels through window 31a towards output coupling mirror 70. A portion of the light passes through the output coupling mirror 70, while the remainder is reflected by the output coupling mirror 70 and propagates through window 31a into the interior space of housing 30. The light propagating into the interior space of housing 30 travels through window 31b and prism 61 towards grating 63, as described above. Thus, light of a predetermined wavelength oscillates between grating 63 and output coupling mirror 70. Each time the light passes through the discharge space within housing 30, it is amplified, generating laser oscillations. Then, a portion of the laser light, as MO injection light, exits housing 30, passes through output coupling mirror 70, is reflected by high-reflectivity mirror 141b, and travels towards beam splitter 151b; this MO injection light is a pulsed laser.

[0117] A portion of the MO injection light traveling toward beamsplitter 151b passes through beamsplitter 151b and is reflected by high-reflectivity mirror 141c, traveling toward rear mirror 171. This portion of the MO injection light traveling toward rear mirror 171 travels through window 31b of rear mirror 171 and amplifier 160 into the interior of housing 30. Furthermore, another portion of the MO injection light traveling toward beamsplitter 151b is reflected by beamsplitter 151b and travels toward photosensor 151c.

[0118] Optical sensor 151c measures the pulse energy (EMO) of a pulsed laser containing MO injected light. Optical sensor 151c outputs a signal representing the measured EMO to processor 190.

[0119] (Step SP43)

[0120] In this step, processor 190 obtains the measured value EMO based on the signal from optical sensor 151c. After obtaining the measured value EMO, processor 190 causes the control flow to proceed to step SP44.

[0121] (Step SP44)

[0122] In this step, processor 190 calculates the difference between the target value EMOt and the measured value EMO of the pulse energy, which is the control quantity ΔEMO. After calculating the control quantity ΔEMO, processor 190 causes the control flow to proceed to step SP45.

[0123] (Step SP45)

[0124] In this step, processor 190 calculates the control quantity ΔVMO of voltage VMO based on the control quantity ΔEMO. After calculating the control quantity ΔVMO, processor 190 causes the control flow to proceed to step SP46.

[0125] (Step SP46)

[0126] In this step, if the measured value EMO is less than the target value EMOt, the processor 190 causes the control flow to proceed to step SP47. If the measured value EMO and the target value EMOt are the same, the processor 190 causes the control flow to proceed to step SP48. Furthermore, if the measured value EMO is greater than the target value EMOt, the processor 190 causes the control flow to proceed to step SP49.

[0127] (Steps SP47, SP48, SP49)

[0128] In step SP47, processor 190 sets the new target value VMOt of voltage VMO to the value obtained by adding the control amount ΔVMO to the target value VMOt in step SP23. In step SP48, processor 190 sets the new target value VMOt of voltage VMO to the target value VMOt in step SP23. In step SP49, processor 190 sets the new target value VMOt of voltage VMO to the value obtained by subtracting the control amount ΔVMO from the target value VMOt in step SP23.

[0129] After setting a new target value VMOt in steps SP47, SP48, and SP49, processor 190 terminates the control flow in the MO energy control process and proceeds to step SP14. Here, we will explain the case where the control flow proceeds in the order of steps SP14, SP15, SP13, and SP14. In this case, processor 190 controls the pulse power module 43 to apply voltage VMO to electrodes 32a and 32b in step SP42 with the new target value VMOt set in steps SP47, SP48, and SP49. Therefore, processor 190 controls the voltage VMO applied to electrodes 32a and 32b based on the measured value EMO.

[0130] Figure 7 This is the control flow diagram of processor 190 in the PO energy control process of step SP14. (See diagram below.) Figure 7As shown, the control flowchart includes steps SP51 to SP59. The PO energy control process is the control process in steps SP41 to SP49, which also perform MO energy control processing on the amplifier 160 side. At the beginning of the PO energy control process, part of the pulsed laser that is reflected by the high-reflectivity mirror 141c as MO injection light travels through the rear mirror 171 and window 31b into the internal space of the housing 30 of the amplifier 160.

[0131] (Step SP51)

[0132] In this step, the processor 190 sets the target value EPOt for the pulse energy of the amplified laser emitted from the amplifier 160.

[0133] (Step SP52)

[0134] In this step, the processor 190 activates the switch in the pulse power module 43 to generate a discharge as the MO injection light from the laser oscillator 130 travels into the discharge space within the housing 30 of the amplifier 160. After the switch is activated, the processor 190 controls the pulse power module 43 to emit amplified laser with a pulse energy of the target value EPOt from the laser oscillator 130. Specifically, the processor 190 controls the pulse power module 43 to apply a voltage VPO to electrodes 32a and 32b at the target value VPOt in step SP33. The target value VPOt is set based on the target value EPOt.

[0135] After a voltage VPO, which is the target value VPOt, is applied, the MO injection light incident on amplifier 160 undergoes amplification and oscillation within amplifier 160. Furthermore, the MO injection light propagating into the internal space of the housing 30 of amplifier 160, as described above, travels through windows 31a and 31b towards the rear mirror 171 and the output coupling mirror 70. Thus, light of a predetermined wavelength oscillates back and forth between the rear mirror 171 and the output coupling mirror 70. Each time the light passes through the discharge space within the internal space of housing 30, it is amplified, generating laser oscillations, and a portion of the light becomes amplified laser light.

[0136] Furthermore, the aforementioned portion of the amplified laser from amplifier 160 passes through output coupling mirror 170 and is reflected by high-reflectivity mirrors 143b and 143c, thus traveling toward beam splitter 153b.

[0137] A portion of the amplified laser beam traveling toward beam splitter 153b passes through beam splitter 153b and exit window 173 and travels toward exposure device 200, while another portion is reflected by beam splitter 153b and travels toward photosensor 153c.

[0138] The optical sensor 153c measures the measured value EPO of the amplified laser pulse. The optical sensor 153c outputs a signal representing the measured value EPO to the processor 190.

[0139] (Steps SP53, SP54, SP55)

[0140] In step SP53, processor 190 obtains the measured value EPO based on the signal from optical sensor 153c. In step SP54, processor 190 calculates the difference between the target value EPOt of the pulse energy and the measured value EPO, which is the control quantity ΔEPO. ​​In step SP55, processor 190 calculates the control quantity ΔVPO of voltage VMO based on the control quantity ΔEPO.

[0141] (Step SP56)

[0142] In this step, if the measured value EPO is less than the target value EPOt, the processor 190 causes the control flow to proceed to step SP57. If the measured value EPO and the target value EPOt are the same, the processor 190 causes the control flow to proceed to step SP58. Furthermore, if the measured value EPO is greater than the target value EPOt, the processor 190 causes the control flow to proceed to step SP59.

[0143] (Steps SP57, SP58, SP59)

[0144] In step SP57, processor 190 sets the new target value VPOt of voltage VPO to the value obtained by adding the control amount ΔVPO to the target value VPOt in step SP33. In step SP58, processor 190 sets the new target value VPOt of voltage VPO to the target value VPOt in step SP33. In step SP59, processor 190 sets the new target value VPOt of voltage VPO to the value obtained by subtracting the control amount ΔVPO from the target value VPOt in step SP33.

[0145] After setting a new target value VPOt in steps SP57, SP58, and SP59, processor 190 terminates the control flow in the PO energy control process and proceeds to step SP15. Here, we will explain the case where the control flow proceeds in the order of steps SP15, SP13, and SP14. In this case, processor 190 controls the pulse power module 43 to apply voltage VPO to electrodes 32a and 32b in step SP52 with the new target value VPOt set in steps SP57, SP58, and SP59. Therefore, processor 190 controls the voltage VPO applied to electrodes 32a and 32b based on the measured value EPO.

[0146] 2.3 Research Topic

[0147] The comparative example gas laser device 100 is a MOPA-type laser device that uses an amplifier 160 to amplify the light emitted from a laser oscillator 130 and emit it into an exposure apparatus 200. In this gas laser device 100, the laser oscillator 130 and the amplifier 160 are controlled independently so that the measured value EPO of the amplified laser pulse traveling from the amplifier 160 to the exposure apparatus 200 converges to a specified range. Hereinafter, this control is sometimes referred to as the exposure amount fixed control mode.

[0148] Furthermore, in the laser oscillator 130, the target value VMOt of the voltage VMO is controlled so that the measured value EMO of the pulse energy of the MO injected light converges within a specified range. Similarly, in the amplifier 160, the target value VPOt of the voltage VPO is also controlled so that the measured value EPO of the pulse energy of the amplified laser converges within a specified range. This control is sometimes referred to below as the output variation control mode.

[0149] However, when implementing a fixed exposure control mode using an output variation control mode, the following issues arise.

[0150] A portion of the MO injection light traveling from the laser oscillator 130 to the rear mirror 171 is reflected by the rear mirror 171. This light is sometimes referred to as MO return light. Additionally, a portion of the amplified laser light, amplified by the amplifier 160, passes through the rear mirror 171. This light is sometimes referred to as PO leakage light. The MO return light and PO leakage light, i.e., the light from the rear mirror 171, are reflected by the high-reflectivity mirror 141c, pass through the beam splitter 151b, and are reflected by the high-reflectivity mirror 141b before traveling towards the output coupler 70. A portion of the light traveling towards the output coupler 70 passes through the output coupler 70 and the window 31b of the laser oscillator 130 into the interior of the housing 30. The light traveling into the interior of the housing 30, as described above, oscillates between the output coupler 70 and the grating 63, passes through the output coupler 70 again, is reflected by the high-reflectivity mirror 141b, and travels again towards the beam splitter 151b. Furthermore, another portion of the light traveling toward the output coupling mirror 70 is reflected by the output coupling mirror 70, and as described above, is reflected by the high-reflectivity mirror 141b, traveling again toward the beam splitter 151b. A portion of the light traveling again toward the beam splitter 151b is reflected by the beam splitter 151b and travels again toward the light sensor 151c. Furthermore, another portion of the light traveling again toward the beam splitter 151b passes through the beam splitter 151b, and travels again toward the rear mirror 171 via the high-reflectivity mirror 141c. A portion of this light passes through the rear mirror 171, travels again toward the output coupling mirror 170, and the other portion is reflected by the rear mirror 171, returning to the output coupling mirror 70.

[0151] When the measured pulse energy EPO of the amplified laser is lower than the target value EPOt, the processor 190 adds a control amount ΔVPO to the voltage VPO of the pulse power module 43 in the amplifier 160 to increase the pulse energy. As a result, the pulse energy of the PO leaking light increases.

[0152] As described above, the PO leaking light is reflected by beam splitter 151b and travels towards optical sensor 151c. As the PO leaking light travels towards optical sensor 151c, it is measured along with the MO injection light and MO return light traveling towards optical sensor 151c. Optical sensor 151c measures the measured value EMO of the pulsed laser energy comprising the PO leaking light, MO injection light, and MO return light. Compared to the measured value EMO before adding a control amount ΔVPO to the voltage VPO, this measured value EMO increases. When the measured value EMO increases, sometimes the measured value EMO exceeds the target value EMOt. In this case, processor 190 subtracts the control amount ΔVMO from the target value VMOt of the pulse power module 43 of laser oscillator 130 to reduce the pulse energy of the MO injection light.

[0153] Figure 8 This illustrates the concept of the operation of the processor 190 described above. Figure 8 This is a graph showing the relationship between the voltage VMO of the pulse power module 43 of the laser oscillator 130 in the comparative example and the timing of the voltage VMO change. Figure 8 The solid line L1 shown illustrates the change in the target value VMOt. The threshold value VMOthmini of the voltage VMO is approximately 70% of the initial value VMO0. When the above operation is repeated, the target value VMOt gradually decreases from the initial value VMO0 by a control amount ΔVMO, thereby gradually reducing the amount of MO injection light emitted from the laser oscillator 130. When the target value VMOt further decreases below the threshold value VMOthmini of the voltage VMO, the amount of MO injection light becomes unstable, and the wavelength control and linewidth control based on the narrowband module 60 become unstable. Furthermore, when the amount of MO injection light becomes unstable, the pulse energy of the amplified laser also becomes unstable. Due to the aforementioned instability, the amplified laser fails to meet the performance requirements of the exposure apparatus 200, and the reliability of the gas laser apparatus 100 may decrease.

[0154] Therefore, in the following embodiments, a cavity device CH capable of suppressing the decrease in reliability of the gas laser device 100 is illustrated.

[0155] 3. Description of the gas laser device in Embodiment 1

[0156] Next, the gas laser device 100 of the embodiment will be described. Furthermore, structures identical to those described above will be labeled with the same reference numerals, and repeated descriptions will be omitted unless otherwise specified.

[0157] 3.1 Structure

[0158] The structure of the gas laser device 100 in this embodiment is the same as that of the gas laser device 100 in the comparative example, so the description is omitted.

[0159] 3.2 Actions

[0160] Figure 9 This is a graph showing the relationship between the voltage VMO of the pulse power module 43 of the laser oscillator 130 in this embodiment and the time of voltage VMO change. Figure 9 The solid line L2 shown illustrates the change in the target value VMOt. Figure 9 In order to compare this embodiment and the comparative example, a single-dotted line L1 is used to indicate that... Figure 8 The change in the target value VMOt is shown using the solid line L1.

[0161] The difference between the operation of this embodiment and the comparative example is that, when the target value VMOt of the voltage VMO is less than the threshold VMOth, the processor 190 switches the control mode of the voltage VMO to a degradation control mode. The threshold VMOth is a value greater than the threshold VMOthmini and less than the initial value VMO0, and is preset and stored in the processor 190's storage device. The threshold VMOth is set to a value greater than the threshold VMOthmini so that it does not operate when the reliability of the gas laser device 100 is reduced. Furthermore, the threshold VMOth can also be set to a value in the range of 70% to 80% of the initial value VMO0. The degradation control mode is a control mode in which the operation of the exposure apparatus 200 can continue even if the lifespan of the gas laser device 100 is shortened compared to the intended lifespan, or even if the stability of the pulsed laser emitted from the gas laser device 100 is reduced. In the degradation control mode of this embodiment, when the target value VMOt is less than the threshold VMOth, the processor 190 maintains the target value VMOt at a fixed value, regardless of the magnitude of the measured value EMO of the pulsed laser energy measured by the optical sensor 151c. The fixed value is a value greater than or equal to the threshold VMOth. The degradation control mode can be either a boost control mode or a fixed control mode. In the boost control mode, the processor 190 boosts the target value VMOt to a voltage VMOα and maintains it at that voltage VMOα, which is a fixed value that is an increment ΔVMOα greater than the threshold VMOth. Furthermore, in the fixed control mode, the processor 190 maintains the target value VMOt at the threshold VMOth, which is a fixed value. In the degradation control mode, which mode—both the boost control mode and the fixed control mode—is preset. In the degradation control mode, the processor 190 independently controls the laser oscillator 130, separate from the amplifier 160. In degradation control mode, exposure device 200 is also driven for a specified period.

[0162] Figure 10 This is a diagram illustrating an example of the control flow diagram of the processor 190 in this embodiment. For example... Figure 10 As shown, the control flow of this embodiment differs from that of the comparative example in that steps SP16 and SP17 are included between steps SP13 and SP14.

[0163] (Steps SP16, SP17)

[0164] In step SP16, processor 190 transitions to the degradation control mode transition process described later. After the degradation control mode transition process is completed, processor 190 causes the control flow to proceed to step SP17. In step SP17, processor 190 transitions to the degradation control mode end determination process described later. After the degradation control mode end determination process is completed, processor 190 causes the control flow to proceed to step SP14.

[0165] The degradation control mode transition processing and degradation control mode termination determination processing are performed in the laser oscillator 130, not in the amplifier 160. This is because only the output variation control mode is processed in the amplifier 160.

[0166] Furthermore, in the control flow of this embodiment, the MO energy control process in step SP13 is different from the MO energy control process in the comparative example.

[0167] Figure 11 This is a control flowchart of the processor 190 in the MO energy control process of step SP13 of this embodiment. The difference between the control flowchart of this embodiment and the flowchart of the comparative example is that step SP71 is included between step SP43 and step SP44.

[0168] (Step SP71)

[0169] In this step, if the current control mode is not a degenerate control mode, then the control mode is an output variation control mode, and processor 190 causes the control flow to proceed to step SP44. Alternatively, if the current control mode is a degenerate control mode, processor 190 terminates the control flow in the MO energy control processing, causing the control flow to proceed to step SP16. Regarding whether the current control mode is a degenerate control mode, in... Figure 12 and Figure 13 The degradation control mode transfer process shown in the following steps will be explained in SP108.

[0170] Figure 12 This is the control flowchart of processor 190 in the pull-up control mode of the degradation control mode transfer processing in step SP16. (See diagram below.) Figure 12 As shown, the control flowchart includes steps SP101 to SP109.

[0171] (Step SP101)

[0172] In this step, if the control mode is a degenerate control mode, the processor 190 terminates the control flow in the degenerate control mode transfer process, causing the control flow to proceed to step SP17. Furthermore, if the current control mode is not a degenerate control mode, then the control mode is an output change control mode, and the processor 190 causes the control flow to proceed to step SP102. Whether the current control mode is a degenerate control mode is explained in step SP108.

[0173] (Step SP102)

[0174] In this step, processor 190 sets a threshold VMOth. After setting the threshold VMOth, processor 190 causes the control flow to proceed to step SP103. Alternatively, the threshold VMOth can be defined based on the difference between target values ​​VMOt generated over a longer period, or based on the difference between target values ​​VMOt generated based on the number of discharges.

[0175] (Step SP103)

[0176] In this step, processor 190 calculates the moving average value VMOtave of the target value VMOt. The moving average value VMOtave is the average value of the target value VMOt over a specified period. The target value VMOt may sometimes change to unexpected values ​​due to external disturbances. To prevent the control mode from unexpectedly becoming a degenerate control mode due to this value, processor 190 calculates the moving average value VMOtave. After calculating the moving average value VMOtave, processor 190 causes the control flow to proceed to step SP104.

[0177] (Step SP104)

[0178] In this step, when the moving average value VMOtave is above the threshold VMOth, the control mode is the output variation control mode. Therefore, the processor 190 terminates the control flow in the degradation control mode transfer process, and the control flow proceeds to step SP17. Furthermore, when the moving average value VMOtave is below the threshold VMOth, the processor 190 transfers the control mode to the degradation control mode, and the control flow proceeds to step SP105.

[0179] (Step SP105)

[0180] In this step, processor 190 sets the control quantity ΔEMO calculated in step SP44. After setting the control quantity ΔEMO, processor 190 causes the control flow to proceed to step SP106.

[0181] (Step SP106)

[0182] In this step, processor 190 resets the target value EMOt of the pulse energy to the value obtained by adding the control quantity ΔEMO to the target value EMOt in step SP41. After resetting the target value EMOt, processor 190 causes the control flow to proceed to step SP107.

[0183] (Step SP107)

[0184] In this step, processor 190 calculates voltage VMOα based on the target value EMOt set again in step SP106. Voltage VMOα is a value smaller than the initial value VMO0. After calculating voltage VMOα, processor 190 causes the control flow to proceed to step SP108.

[0185] (Step SP108)

[0186] In this step, the processor 190 sets the target value VMOt of the voltage VMO to a fixed value VMOα. After setting the voltage VMOα, the processor 190 switches to a degraded control mode, causing the control flow to proceed to step SP109. Alternatively, the control flow is assumed to proceed in the order of steps SP109, SP17, SP14, SP15, and SP13. In this case, in step SP42, the processor 190 controls the pulse power module 43 to apply the voltage VMO to electrodes 32a and 32b at the new target value VMOt, which was set in step SP108. Therefore, if the moving average value VMOtave is lower than the threshold value VMOth, the processor 190 maintains the voltage VMO at the fixed value VMOα. Furthermore, when the control flow further proceeds in the order of steps SP42, SP43, and SP71, the control mode switches to a degraded control mode, and the processor 190 terminates the control flow in the MO energy control process, causing the control flow to proceed to step SP16.

[0187] (Step SP109)

[0188] In this step, the processor 190 outputs a signal to the display unit 180 indicating that the voltage VMO will be maintained at a fixed value VMOα, i.e., the degradation control mode has started. The display unit 180 then notifies the start of the degradation control mode. Even with the notification from the display unit 180, the exposure apparatus 200 continues to operate. After outputting the signal to the display unit 180, the processor 190 terminates the control flow in the pull-up control mode of the degradation control mode transfer process and proceeds to step SP17.

[0189] For example, Figure 9The time t1 shown is the moment in step SP104 when the moving average value VMOtave is lower than the threshold VMOth. In this case, in step SP106, the new target value EMOt becomes the value obtained by adding a predetermined sum ΔEMOα to the target value EMOt, and the target value VMOt in step SP108 becomes the voltage VMOα obtained by adding the sum ΔVMOα to the threshold VMOth. Figure 9 In this context, the moment when the target value VMOt becomes voltage VMOα is denoted as t11. Furthermore, time t1 is the moment when the display unit 180 notifies the start of the degradation control mode in step SP109.

[0190] Figure 13 This is the control flow diagram of processor 190 in the fixed control mode of the degradation control mode transfer process in step SP16. (See diagram for example.) Figure 13 As shown, the control flowchart is similar to... Figure 12 The difference in the pull-up control mode described herein is that step SP111 is included instead of steps SP105 to SP108. In step SP104, when the moving average value VMOtave is lower than the threshold VMOth, the processor 190 switches the control mode to the degradation control mode, causing the control flow to proceed to step SP111.

[0191] (Step SP111)

[0192] In this step, the processor 190 sets the target value VMOt of the voltage VMO to a fixed threshold VMOth. After setting the threshold VMOth, the processor 190 switches to a degradation control mode, causing the control flow to proceed to step SP109. In step SP109 of the fixed control mode, the processor 190 outputs a signal indicating that the voltage VMO will be maintained at the fixed threshold VMOth to the display unit 180, and the display unit 180 notifies the start of the degradation control mode. Alternatively, the control flow is assumed to proceed in the order of steps SP109, SP17, SP14, SP15, and SP13. In this case, in step SP42, the processor 190 controls the pulse power module 43 to apply the voltage VMO to electrodes 32a and 32b at the new target value VMOt, which was set in step SP108. Therefore, if the moving average value VMOtave is lower than the threshold VMOth, the processor 190 maintains the voltage VMO at the fixed threshold VMOth.

[0193] Figure 14 This is the control flow diagram of processor 190 in the degradation control mode termination determination process of step SP17. (See diagram below.) Figure 14 As shown, the control flowchart includes steps SP121 to SP127.

[0194] (Step SP121)

[0195] In this step, if the control mode is not a degenerate control mode, the processor 190 terminates the control flow in the degenerate control mode termination decision process, causing the control flow to proceed to step SP14. Alternatively, if the current control mode is a degenerate control mode, the processor 190 causes the control flow to proceed to step SP122.

[0196] (Step SP122)

[0197] In this step, after receiving a signal representing the number of pulses PLS of the pulsed laser from the optical sensor 151c, the processor 190 measures the number of pulses PLS in the degradation control mode. The measurement period can be a predetermined period from the start of the degradation control mode or a predetermined period within the degradation control mode. After measuring the number of pulses PLS, the processor 190 causes the control flow to proceed to step SP123.

[0198] (Step SP123)

[0199] In this step, if a signal from the exposure device 200 indicates that the exposure device 200 is in exposure mode, the processor 190 terminates the degradation control mode and ends the control flow in the determination process, causing the control flow to proceed to step SP14. Furthermore, if a signal from the exposure device 200 indicates that the exposure device 200 is not in exposure mode, or if no signal is input from the exposure device 200, the processor 190 causes the control flow to proceed to step SP124. Additionally, if a signal from the exposure device 200 indicates that the characteristics of the pulsed laser emitted from the laser oscillator 130 are to be adjusted, the processor 190 may also cause the control flow to proceed to step SP14. This signal, for example, is an indication to adjust the supply amount of laser gas from a laser gas supply device (not shown) toward the internal space of the housing 30.

[0200] (Step SP124)

[0201] In this step, processor 190 reads the pulse number threshold PLSth pre-stored in its storage device. The pulse number threshold PLSth is the maximum number of pulses that allows the gas laser device 100 and the exposure device 200 to operate in the degradation control mode. After reading the pulse number threshold PLSth, processor 190 causes the control flow to proceed to step SP125.

[0202] (Step SP125)

[0203] In this step, processor 190 calculates the cumulative value ΣPLS of the pulse count PLS measured in step SP122. After calculating the cumulative value ΣPLS, processor 190 causes the control flow to proceed to step SP126. The cumulative value ΣPLS can be the cumulative value within the specified period described in step SP122, or it can be the cumulative value from the start of measurement.

[0204] (Step SP126)

[0205] In this step, if the cumulative value ΣPLS is below the pulse count threshold PLSth, the processor 190 terminates the degradation control mode and ends the control flow in the decision-making process, causing the control flow to proceed to step SP14. Furthermore, if the cumulative value ΣPLS is greater than the pulse count threshold PLSth, the processor 190 causes the control flow to proceed to step SP127.

[0206] (Step SP127)

[0207] In this step, processor 190 stops the application of voltage to laser oscillator 130, ending the degradation control mode, and stops the application of voltage to amplifier 160. Furthermore, processor 190 outputs an error signal to exposure apparatus 200. This error could indicate, for example, a work stoppage or maintenance notification. After this signal is input to exposure apparatus 200, exposure apparatus 200 stops. After stopping the application of voltage and outputting the error signal to exposure apparatus 200, processor 190 ends the degradation control mode, terminates the control flow in the determination process, and moves the control flow to step SP14. Upon receiving this signal, exposure apparatus 200 does not output an oscillation indication signal to gas laser device 100. Therefore, after the control flow enters steps SP14 and SP15, processor 190 terminates the control flow.

[0208] 3.3 Functions / Effects

[0209] In the gas laser apparatus 100 of this embodiment, when the target value VMOt of the voltage VMO in the laser oscillator 130 is lower than the threshold VMOth, the processor 190 maintains the target value VMOt of the voltage VMO at a fixed value above the threshold VMOth. Therefore, even if the PO leakage light from the amplifier 160 increases, causing the measured value EMO of the pulsed laser detected by the photosensor 151c to rise, it is possible to prevent the target value VMOt of the voltage VMO from falling below the threshold VMOth. When the target value VMOt of the voltage VMO is suppressed from decreasing, instability in the amount of MO injected light can be suppressed. When this instability in the amount of light is suppressed, instability in the pulse energy of the amplified laser can be suppressed, and the gas laser apparatus 100 can continue to operate while meeting the performance requirements of the exposure apparatus 200, thus preventing a decrease in the reliability of the gas laser apparatus 100.

[0210] In the gas laser device 100 of this embodiment, the fixed value is a voltage VMOα that is greater than the threshold VMOth. In this case, the degradation control mode is a pull-up control mode, and compared with the fixed control mode, the amount of MO injection light emitted from the laser oscillator 130 can be increased, and the instability of the pulse energy of the amplified laser can be suppressed. Alternatively, the fixed value is the same as the threshold VMOth. In this case, the degradation control mode is a fixed control mode, and in the fixed control mode, it is not necessary to calculate the sum ΔVMOα used to pull up the threshold VMOth to the voltage VMOα in the pull-up control mode. Therefore, in the above structure, the burden on the processor 190 can be reduced compared with the pull-up control mode.

[0211] In the gas laser device 100 of this embodiment, when the moving average value VMOtave is lower than the threshold VMOth as described in step SP104, the processor 190 sets the target value VMOt of the voltage VMO to a fixed value as described in steps SP108 and SP111. Furthermore, the processor 190 maintains the voltage VMO applied to the electrodes 32a and 32b at this fixed value for the target value VMOt. The target value VMOt sometimes changes to an unexpected value due to external interference. By using the moving average value VMOtave as described above, it is possible to suppress unnecessary shifts from the output variation control mode to the degradation control mode caused by the target value VMOt temporarily falling below the threshold VMOth due to external interference. Alternatively, the processor 190 may also maintain the voltage VMOt applied to the electrodes 32a and 32b at a fixed value when the target value VMOt is lower than the threshold VMOth without using the moving average value VMOtave.

[0212] In the gas laser device 100 of this embodiment, as explained in step SP109, when the moving average value VMOtave is lower than the threshold VMOth, the display unit 180 notifies the user to start maintaining the target value VMOt of the voltage VMO at a fixed value of voltage VMOα or threshold VMOth. Thus, the user of the gas laser device 100 can be notified of this start.

[0213] In the gas laser apparatus 100 of this embodiment, as explained in step SP127, the processor 190 stops applying the voltage VMO when the cumulative pulse count ΣPLS exceeds the pulse count threshold PLSth. When the exposure apparatus 200 stops simultaneously with the start of the degradation control mode, the exposure apparatus 200 stops manufacturing midway through the completion of a workpiece such as a semiconductor wafer, sometimes resulting in workpiece waste. In the above configuration, even after the degradation control mode has started, the exposure apparatus 200 can operate for a predetermined period until the cumulative count ΣPLS exceeds the pulse count threshold PLSth. Therefore, the exposure apparatus 200 can stop after the workpiece is completed, suppressing workpiece waste.

[0214] In the gas laser apparatus 100 of this embodiment, as explained in step SP127, when the cumulative pulse count ΣPLS exceeds the pulse count threshold PLSth, the processor 190 outputs an error signal to the exposure apparatus 200. This error may indicate, for example, a notification of operation stoppage or maintenance. Thus, the exposure apparatus 200 can be notified of, for example, operation stoppage or maintenance.

[0215] The beam splitter 151b can be positioned in the optical path of the pulsed laser emitted from the output coupling mirror 70. Furthermore, the detection unit 153 can be positioned in the optical path of the pulsed laser emitted from the output coupling mirror 170. Therefore, the detection unit 153 can also be positioned inside the exposure apparatus 200. For example, the detection unit 153 can also be positioned between the projection optical system 220 and the workpiece stage WT. In the degradation control mode end determination process, the processor 190 can also measure the number of pulses PLS in the degradation control mode based on the signal representing the number of pulses PLS from the light sensor 153c. In the degradation control mode end determination process, the processor 190 can also output an error signal to the exposure apparatus 200 based on the number of times the control flow transitions to the degradation control mode end determination process after the start of the degradation control mode. In the degradation control mode end determination process, the processor 190 can also measure the number of times the control flow enters step SP122 in step SP122, and if the number exceeds a threshold, cause the control flow to enter step SP127. Furthermore, if the number of occurrences is below a threshold, the processor 190 may also cause the control flow to proceed to step SP14. In the degradation control mode end determination process, the processor 190 may also measure the time from the start of the degradation control mode in step SP122, and if the time is greater than a threshold, cause the control flow to proceed to step SP127. Furthermore, if the time is below the threshold, the processor 190 may also cause the control flow to proceed to step SP14.

[0216] 4. Description of the gas laser device in Embodiment 2

[0217] Next, the gas laser device 100 of Embodiment 2 will be described. Furthermore, structures identical to those described above will be labeled with the same reference numerals, and repeated descriptions will be omitted unless otherwise specified.

[0218] 4.1 Structure

[0219] The structure of the gas laser device 100 in this embodiment is the same as that of the gas laser device 100 in the comparative example and embodiment 1, so the description is omitted.

[0220] 4.2 Actions

[0221] Figure 15 This is a graph showing the relationship between the voltage VMO of the pulse power module 43 of the laser oscillator 130 in this embodiment and the time when the voltage VMO changes, as well as the relationship between the target value EMOt of the pulse energy and the time when the target value EMOt changes.

[0222] The degradation control mode in this embodiment differs from that in Embodiment 1 in that, even in the degradation control mode, like the output variation control mode, there is a tendency for the voltage VMO to gradually decrease with the control quantity ΔVMO. The degradation control mode in this embodiment also differs from that in Embodiment 1 in that the criterion for determining the end of the degradation control mode is based on the target value EMOt of the pulse energy variation.

[0223] In the degradation control mode of this embodiment, whenever the moving average value VMOtave of the target value VMOt falls below the threshold VMOth, the processor 190 increases the target value VMOt to a voltage VMOα, which is a predetermined value that is larger than the threshold VMOth by an increment ΔVMOα. Furthermore, the processor 190 controls the pulse power module 43 to apply this voltage VMOα to the electrodes 32a and 32b. The processor 190 repeats the above setting and application.

[0224] In determining the end of the degradation control mode, in Embodiment 1, the processor 190 determines the end of the degradation control mode based on the number of pulses PLS of the pulsed laser. In contrast, in this embodiment, the processor 190 determines the end of the degradation control mode based on the upper limit threshold EMOtth of the target value EMOt of the additionally set pulse energy of the laser oscillator 130. In this embodiment, in the degradation control mode, whenever the moving average value VMOtave of the target value VMOt falls below the threshold VMOth, the processor 190 sets a new target value EMOt by adding an additive amount ΔEMOα to the target value EMOt. Then, when the new target value EMOt exceeds the threshold EMOtth, the processor 190 terminates the degradation control mode.

[0225] Figure 16 This is a control flowchart of the processor 190 in the MO energy control process of step SP13 of this embodiment. The difference between the control flowchart of this embodiment and the flowchart of the comparative example is that the position of step SP71 is changed to between the starting state and step SP41.

[0226] (Step SP71)

[0227] In this step, if the current control mode is not a degenerate control mode, then the control mode is an output variation control mode, and the processor 190 causes the control flow to proceed to step SP41. Furthermore, if the current control mode is a degenerate control mode, the processor 190 causes the control flow to proceed to step SP42. If it is a degenerate control mode, a new target value EMOt is set as described in step SP133 later. Therefore, in the degenerate control mode, the processor 190 controls the pulse power module 43 to emit pulse energy at the MO injection light output for the target value EMOt. Specifically, the processor 190 controls the pulse power module 43 to apply a voltage VMO to the electrodes 32a and 32b of the laser oscillator 130 in step SP42 at a target value VMOt set according to the target value EMOt.

[0228] Figure 17 This is a control flowchart of the processor 190 in the degradation control mode transfer process of step SP16 of this embodiment. This control flowchart is related to... Figure 12 The difference in the lifting control mode described herein is that steps SP132 to SP134 are included instead of steps SP131 and steps SP105 to SP108.

[0229] (Step SP101)

[0230] In this step, if the current control mode is not a degenerate control mode, the processor 190 causes the control flow to proceed to step SP102. Furthermore, if the control mode is a degenerate control mode, the processor 190 causes the control flow to proceed to step SP131.

[0231] (Step SP131)

[0232] In this step, processor 190 calculates the moving average value VMOtave of the target value VMOt of the voltage VMO in the degradation control mode. The moving average value VMOtave in step SP104 is the value in the mode before degradation control, i.e., the output variation control mode; however, the moving average value VMOtave in this step is the value in the degradation control mode. The moving average value VMOtave in this step is, for example, between 50 and 200 pulses. This moving average value VMOtave is different from the moving average value VMOtave calculated in step SP103 in the output variation control mode. Therefore, processor 190 does not use the moving average value VMOtave calculated in the output variation control mode as the average value in the degradation control mode. After calculating the moving average value VMOtave, processor 190 causes the control flow to proceed to step SP104.

[0233] (Step SP104)

[0234] In step SP104, if the moving average value VMOtave is above the threshold VMOth, the processor 190 terminates the control flow in the degradation control mode transition process and moves the control flow to step SP17. Furthermore, if the moving average value VMOtave is below the threshold VMOth, the processor 190 moves the control flow to step SP132.

[0235] (Step SP132)

[0236] In this step, the processor 190 sets the sum ΔEMOα, causing the control flow to proceed to step SP133. The sum ΔEMOα is pre-stored in the processor 190's storage device.

[0237] (Step SP133)

[0238] In this step, processor 190 sets a new target value EMOt by adding an additive amount ΔEMOα to the target value EMOt. Each time the control flow enters step SP133, the new target value EMOt increases in a stepwise manner. Processor 190 stores the set new target value EMOt in its storage device, causing the control flow to enter step SP134.

[0239] However, suppose the control flow proceeds in the order of steps SP17, SP14, SP15, and SP13 after the degradation control mode transition processing. In this case, as explained in step SP71, the processor 190 controls the pulse power module 43 so that in step SP42, a voltage VMO is applied to the electrodes 32a and 32b of the laser oscillator 130 at a target value VMOt set according to the new target value EMOt. For example, Figure 15The times t1, t2, and t3 shown are the times when the moving average value VMOtave is lower than the threshold VMOth in step SP104. In this case, in step SP133, the new target value EMOt becomes the value obtained by adding an additive amount ΔEMOα to the target value EMOt, and the target value VMOt in step SP42 becomes the voltage VMOα obtained by adding an additive amount ΔVMOα to the threshold VMOth. Figure 15 In this process, the times when the target value VMOt becomes voltage VMOα are denoted as t11 and t21. Between time t11 and time t2, and between time t21 and time t3, similar to the output variation control mode, the pulse energy of the light leaking from PO increases, therefore, the target value VMOt tends to gradually decrease with the control amount ΔVMO. Therefore, if the target value VMOt, which has been increased to a predetermined value of voltage VMOα, is lower than the threshold VMOth, the processor 190 increases the target value VMOt back to voltage VMOα. Furthermore, in the degradation control mode, whenever the moving average value VMOtave is lower than the threshold VMOth, in step SP133, the processor 190 increases the target value EMOt with an additive amount ΔEMOα.

[0240] (Step SP134)

[0241] In this step, if the signal indicating the start of the degradation control mode is not output to the display unit 180 as described in step SP109, then no notification is received that it is in degradation control mode, and the processor 190 causes the control flow to proceed to step SP109. Furthermore, if the signal is output to the display unit 180 and a notification is received that it is in degradation control mode, the processor 190 terminates the control flow in the degradation control mode transfer process and causes the control flow to proceed to step SP17.

[0242] Figure 18 This is a control flowchart of the processor 190 in the degradation control mode end determination process of step SP17 of this embodiment. This control flowchart is related to... Figure 14 The difference between the degradation control mode end determination process described in this embodiment and the one described in the previous embodiment is that step SP122 is not required, and steps SP141 to SP143 are included instead of steps SP124 to SP126. Furthermore, the degradation control mode end determination process of this embodiment can also be the degradation control mode end determination process of Embodiment 1.

[0243] (Steps SP121, SP123)

[0244] In step SP121, if the current control mode is a degradation control mode, the processor 190 causes the control flow to proceed to step SP123. In step SP123, if the exposure device 200 is in exposure, the processor 190 causes the control flow to proceed to step SP141.

[0245] (Step SP141)

[0246] In this step, processor 190 reads the pre-stored threshold EMOtth from its storage device. The threshold EMOtth is the voltage value predicted to prevent damage to the narrowband module 60 by the pulsed laser. After reading the threshold EMOtth, processor 190 causes the control flow to proceed to step SP142.

[0247] (Step SP142)

[0248] In this step, processor 190 reads the target value EMOt of the pulse energy stored in the processor 190's storage device in step SP133. After reading the target value EMOt, processor 190 causes the control flow to proceed to step SP143.

[0249] (Step SP143)

[0250] In this step, if the target value EMOt is below the threshold EMOtth, the processor 190 terminates the degradation control mode and ends the control flow in the determination process, causing the control flow to proceed to step SP14. Furthermore, if the target value EMOt is greater than the threshold EMOtth, the processor 190 causes the control flow to proceed to step SP127. Additionally, in this step, if the number of additions ΔEMOα in step SP133 is less than a predetermined number, the processor 190 may also terminate the control flow and cause the control flow to proceed to step SP14. Furthermore, if the number of additions is greater than the predetermined number, the processor 190 may also cause the control flow to proceed to step SP127.

[0251] 4.3 Functions / Effects

[0252] In the gas laser apparatus 100 of this embodiment, when the target value VMOt of the voltage VMO in the laser oscillator 130 is lower than the threshold VMOth, the processor 190 increases the target value VMOt to a voltage VMOα, which is a predetermined value larger than the threshold VMOth. Therefore, even if the leakage light from the amplifier 160 increases, causing the measured value EMO of the pulsed laser detected by the photosensor 151c to rise, it is possible to suppress the voltage VMO from falling below the threshold VMOth. When the voltage VMO is suppressed, instability in the amount of MO injected light can be suppressed. When the instability in the amount of light is suppressed, instability in the pulse energy of the amplified laser can be suppressed, and the gas laser apparatus 100 can continue to operate while meeting the performance requirements of the exposure apparatus 200, thus preventing a decrease in the reliability of the gas laser apparatus 100.

[0253] In the gas laser device 100 of this embodiment, if the target value VMOt of the voltage VMO, which is increased to a predetermined value VMOα, is lower than the threshold VMOth, the processor 190 increases the target value VMOt of the voltage VMO back to the predetermined value VMOα. After the voltage VMO is increased to the voltage VMOα, the pulse energy of the PO leakage light increases, the measured value EMO rises, and sometimes the target value VMOt of the voltage VMO is lower than the threshold VMOth. In the above structure, the processor 190 increases the target value VMOt of the voltage VMO back to the predetermined value VMOα, thus suppressing the target value VMOt of the voltage VMO from falling below the threshold VMOth. When the target value VMOt of the voltage VMO is suppressed from decreasing, the instability of the amount of MO injected light can be suppressed.

[0254] In the gas laser apparatus 100 of this embodiment, whenever the target value VMOt of the voltage VMO, which is increased to voltage VMOα, is lower than the threshold VMOth, the processor 190 increases the target value EMOt of the pulse energy. Furthermore, if the target value EMOt is greater than the threshold Emotth, the processor 190 stops applying the voltage VMO. In this configuration, even after the degradation control mode has started, the exposure apparatus 200 can operate for a predetermined period until the target value EMOt is greater than the threshold Emotth. Therefore, the exposure apparatus 200 can stop after the workpiece is completed, thus suppressing workpiece waste.

[0255] In the gas laser device 100 of this embodiment, as described in steps SP143 and SP127, when the target value EMOt is greater than the threshold EMOtth, the processor 190 outputs an error signal to the exposure device 200. This allows the exposure device 200 to be notified, for example, of a shutdown or maintenance request.

[0256] 5. Description of the gas laser device in Embodiment 3

[0257] Next, the gas laser device 100 of Embodiment 3 will be described. Furthermore, structures identical to those described above will be labeled with the same reference numerals, and repeated descriptions will be omitted unless otherwise specified.

[0258] 5.1 Structure

[0259] The structure of the gas laser device 100 in this embodiment is the same as that of the gas laser device 100 in the comparative example and embodiments 1 and 2, so the description is omitted.

[0260] 5.2 Actions

[0261] Figure 19 This is a graph showing the relationship between the voltage VMO of the pulse power module 43 of the laser oscillator 130 in this embodiment and the time when the voltage VMO changes, as well as the relationship between the target value EMOt of the pulse energy and the time when the target value EMOt changes.

[0262] In the degradation control mode of this embodiment, when the moving average value VMOtave falls below the threshold VMOth, the processor 190 sets the target value VMOt of the voltage VMO to a predetermined value, VMOmax. Furthermore, the processor 190 controls the pulse power module 43 to apply this voltage VMOα to the electrodes 32a and 32b of the laser oscillator 130. The processor 190 performs this setting and application only once each, unlike the degradation control mode of Embodiment 2, which repeatedly performs the above setting and application. The voltage VMOmax is a value that is greater than the threshold VMOth by the sum of ΔVMOα and greater than the initial value VMO0. Furthermore, the voltage VMOmax is the maximum value of the voltage predicted to prevent damage to the narrowband module 60 by the pulsed laser.

[0263] Furthermore, the difference between the termination determination of the degradation control mode in this embodiment and that in Embodiment 2 is that the termination determination is based on a target value VMOt for the change in voltage VMO. In Embodiment 2, the processor 190 determines the termination of the degradation control mode based on a target value EMOt for the pulse energy. In contrast, in this embodiment, the processor 190 terminates the degradation control mode when the moving average value VMOtave of voltage VMO in the degradation control mode is lower than a threshold VMOth. Besides the moving average value VMOtave, the termination determination can also be based on the value VMOtave of voltage VMO in Embodiment 1. Figure 14 The determination is made based on the number of pulses, the time elapsed, and their combinations.

[0264] Figure 20 This is a control flowchart of the processor 190 in the degradation control mode transfer process of step SP16 of this embodiment. This control flowchart is related to... Figure 17 The difference in the degradation control mode transfer process of Implementation 2 described herein is that step SP151 is included between step SP104 and step SP132, and step SP134 is not required.

[0265] (Step SP104)

[0266] In this step, if the moving average VMOtave is lower than the threshold VMOth, the processor 190 causes the control flow to proceed to step SP151.

[0267] (Step SP151)

[0268] In this step, if the control mode is a degenerate control mode, the processor 190 terminates the control flow in the degenerate control mode transfer process, causing the control flow to proceed to step SP17. Furthermore, if the current control mode is not a degenerate control mode, the processor 190 causes the control flow to proceed to step SP132.

[0269] However, suppose the control flow proceeds in the order of steps SP17, SP14, SP15, and SP13 after the degradation control mode transition processing. In this case, as explained in step SP71, the processor 190 controls the pulse power module 43 so that in step SP42, a voltage VMO is applied to the electrodes 32a and 32b of the laser oscillator 130 at a target value VMOt set according to the new target value EMOt. For example, Figure 19 The time t1 shown is the moment in step SP104 when the moving average value VMOtave is less than the threshold VMOth. In this case, in step SP133, the new target value EMOt becomes EMOmax obtained by adding an additive amount ΔEMOα to the target value EMOt, and the target value VMOt in step SP42 becomes the voltage VMOmax obtained by adding an additive amount ΔVMOα to the threshold VMOth. Figure 19 In this context, the moment when the target value VMOt becomes the voltage VMOmax is denoted as t13. After time t13, similar to the output variation control mode, the pulse energy of the light leaking from PO increases, therefore, the voltage VMOα tends to gradually decrease with the control quantity ΔVMO.

[0270] Figure 21 This is a control flowchart of the processor 190 in the degradation control mode end determination process of step SP17 of this embodiment. This control flowchart is related to... Figure 18The difference in the degradation control mode termination determination process of Implementation 2 described herein is that step SP121 is not required, and step SP104 is included instead of steps SP141 to SP143.

[0271] (Step SP104)

[0272] In this step, if the moving average value VMOtave is above the threshold VMOth, the processor 190 terminates the degradation control mode and ends the control flow in the decision processing, causing the control flow to proceed to step SP17. Furthermore, if the moving average value VMOtave is less than the threshold VMOth, the processor 190 causes the control flow to proceed to step SP127.

[0273] 5.3 Functions / Effects

[0274] In the gas laser device 100 of this embodiment, if the moving average value VMOt of the target value VMO after the voltage VMOmax is increased to a predetermined value, VMOtave, is lower than the threshold VMOth, the processor 190 stops applying the voltage VMO. In the above structure, it is not necessary to increase the target value EMOt of the pulse energy whenever the moving average value VMOtave is lower than the threshold VMOth, as in Embodiment 2. Therefore, in the above structure, the burden on the processor 190 can be reduced.

[0275] The foregoing description is not a limitation but a simple illustration. Therefore, those skilled in the art will understand that modifications can be made to embodiments of this disclosure without departing from the claims. Furthermore, those skilled in the art will understand the use of embodiments of this disclosure in combination.

[0276] Unless explicitly stated otherwise, all terms used in this specification and claims should be interpreted as "non-limiting." For example, terms such as "comprising" or "including" should be interpreted as "not limited to the portion described as included." Terms such as "having" should be interpreted as "not limited to the portion described as having." Furthermore, the indefinite article "a" should be interpreted as meaning "at least one" or "one or more." Additionally, terms such as "at least one of A, B, and C" should be interpreted as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Moreover, it should be interpreted as also including combinations of these and portions other than "A," "B," and "C."

Claims

1. A gas laser device, comprising: A laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using a laser gas by applying a voltage, the laser-side resonator causing the light to resonate; An amplifier comprising an amplification section for amplifying the light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; A beam splitter that reflects a portion of the light from the laser-side resonator; A light sensor that detects the light reflected by the beam splitter; and The processor controls the voltage based on the output of the optical sensor. The amplification-side resonator includes: The rear mirror allows a portion of the light from the laser-side resonator to pass through, and another portion of the light from the laser-side resonator to be reflected toward the laser-side resonator. It also allows a portion of the light amplified by the amplification section to pass through toward the laser-side resonator, and another portion of the light amplified by the amplification section to be reflected. as well as A magnifying-side output coupling mirror reflects a portion of the light amplified by the magnifying section, while allowing another portion of the light amplified by the magnifying section to pass through. The laser-side resonator includes: A grating that reflects the light generated by the laser gas; and A laser-side output coupler reflects a portion of the light generated by the laser gas, allows another portion of the light generated by the laser gas to pass through towards the beam splitter, and reflects a portion of the light from the rear mirror towards the beam splitter. If the voltage is lower than a voltage threshold, the processor maintains the voltage at a fixed value above the threshold.

2. The gas laser device according to claim 1, wherein, The fixed value is a value larger than the threshold.

3. The gas laser device according to claim 1, wherein, The fixed value is the same as the threshold value.

4. The gas laser device according to claim 1, wherein, If the moving average of the voltage is lower than the threshold, the processor maintains the voltage at the fixed value.

5. The gas laser device according to claim 1, wherein, The gas laser device also has a display unit that notifies the start of maintaining the voltage at the fixed value.

6. The gas laser device according to claim 5, wherein, The light sensor inputs a signal representing the number of light pulses to the processor. If the cumulative number of pulses after the start of the notification exceeds a threshold value, the processor stops the application of the voltage.

7. The gas laser device according to claim 6, wherein, If the cumulative value is greater than the cumulative threshold, the processor outputs a signal indicating an error to the exposure device, wherein the light from the magnification-side output coupling mirror is incident on the exposure device.

8. A gas laser device, comprising: A laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using a laser gas by applying a voltage, the laser-side resonator causing the light to resonate; An amplifier comprising an amplification section for amplifying the light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; A beam splitter that reflects a portion of the light from the laser-side resonator; A light sensor that detects the light reflected by the beam splitter; and The processor controls the voltage based on the output of the optical sensor. The amplification-side resonator includes: The rear mirror allows a portion of the light from the laser-side resonator to pass through, and another portion of the light from the laser-side resonator to be reflected toward the laser-side resonator. It also allows a portion of the light amplified by the amplification section to pass through toward the laser-side resonator, and another portion of the light amplified by the amplification section to be reflected. as well as A magnifying-side output coupling mirror reflects a portion of the light amplified by the magnifying section, while allowing another portion of the light amplified by the magnifying section to pass through. The laser-side resonator includes: A grating that reflects the light generated by the laser gas; and A laser-side output coupler reflects a portion of the light generated by the laser gas, allows another portion of the light generated by the laser gas to pass through towards the beam splitter, and reflects a portion of the light from the rear mirror towards the beam splitter. If the voltage is lower than a threshold value, the processor increases the voltage to a predetermined value greater than the threshold value.

9. The gas laser device according to claim 8, wherein, If the moving average of the voltage is below the threshold, the processor increases the voltage to the specified value.

10. The gas laser device according to claim 8, wherein, The gas laser device also has a display unit that notifies the start of increasing the voltage to the specified value.

11. The gas laser device according to claim 8, wherein, If the voltage raised to the specified value is lower than the threshold, the processor raises the voltage back to the specified value.

12. The gas laser device according to claim 11, wherein, Whenever the voltage is lower than the threshold, the processor increases the target value of the pulse energy of the light; when the target value is greater than the threshold value, the processor stops the application of the voltage.

13. The gas laser device according to claim 12, wherein, If the target value is greater than the target threshold, the processor outputs an error signal to the exposure device, wherein the light from the magnification side output coupling mirror is incident on the exposure device.

14. The gas laser device according to claim 8, wherein, If the moving average of the voltage after being increased to the specified value is lower than the threshold, the processor stops the application of the voltage.

15. The gas laser device according to claim 14, wherein, If the moving average value is lower than the threshold, the processor outputs a signal indicating an error to the exposure device, wherein the light from the magnification-side output coupling mirror is incident on the exposure device.

16. A method for manufacturing an electronic device, comprising the following steps: Laser is generated using a gas laser device. The laser is output to the exposure device. The laser is exposed on a photosensitive substrate within the exposure apparatus to manufacture electronic devices. The gas laser device has the following features: A laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using a laser gas by applying a voltage, the laser-side resonator causing the light to resonate; An amplifier comprising an amplification section for amplifying the light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; A beam splitter that reflects a portion of the light from the laser-side resonator; A light sensor that detects the light reflected by the beam splitter; and The processor controls the voltage based on the output of the optical sensor. The amplification-side resonator includes: The rear mirror allows a portion of the light from the laser-side resonator to pass through, and another portion of the light from the laser-side resonator to be reflected toward the laser-side resonator. It also allows a portion of the light amplified by the amplification section to pass through toward the laser-side resonator, and another portion of the light amplified by the amplification section to be reflected. as well as A magnifying-side output coupling mirror reflects a portion of the light amplified by the magnifying section, while allowing another portion of the light amplified by the magnifying section to pass through. The laser-side resonator includes: A grating that reflects the light generated by the laser gas; and A laser-side output coupler reflects a portion of the light generated by the laser gas, allows another portion of the light generated by the laser gas to pass through towards the beam splitter, and reflects a portion of the light from the rear mirror towards the beam splitter. If the voltage is lower than a voltage threshold, the processor maintains the voltage at a fixed value above the threshold.

17. A method for manufacturing an electronic device, comprising the following steps: Laser is generated using a gas laser device. The laser is output to the exposure device. The laser is exposed on a photosensitive substrate within the exposure apparatus to manufacture electronic devices. The gas laser device has the following features: A laser oscillator comprising a pair of discharge electrodes and a laser-side resonator, the pair of discharge electrodes being disposed opposite each other and generating light using a laser gas by applying a voltage, the laser-side resonator causing the light to resonate; An amplifier comprising an amplification section for amplifying the light transmitted through the laser-side resonator and an amplification-side resonator for resonating the light amplified by the amplification section; A beam splitter that reflects a portion of the light from the laser-side resonator; A light sensor that detects the light reflected by the beam splitter; and The processor controls the voltage based on the output of the optical sensor. The amplification-side resonator includes: The rear mirror allows a portion of the light from the laser-side resonator to pass through, and another portion of the light from the laser-side resonator to be reflected toward the laser-side resonator. It also allows a portion of the light amplified by the amplification section to pass through toward the laser-side resonator, and another portion of the light amplified by the amplification section to be reflected. as well as A magnifying-side output coupling mirror reflects a portion of the light amplified by the magnifying section, while allowing another portion of the light amplified by the magnifying section to pass through. The laser-side resonator includes: A grating that reflects the light generated by the laser gas; and A laser-side output coupler reflects a portion of the light generated by the laser gas, allows another portion of the light generated by the laser gas to pass through towards the beam splitter, and reflects a portion of the light from the rear mirror towards the beam splitter. If the voltage is lower than a threshold value, the processor increases the voltage to a predetermined value greater than the threshold value.

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