Gas laser apparatus, method for controlling temperature of laser gas, and method for manufacturing electronic device

Abstract

A gas laser device that outputs a pulsed laser beam includes: a laser chamber that accommodates a laser gas; a discharge electrode that is disposed in the laser chamber and that discharges and excites the laser gas; an optical element disposed on an optical path of the pulsed laser light; and a processor that changes the target temperature of the laser gas in accordance with either the number of pulses of the pulsed laser light or the elapsed time during which the pulsed laser light is output.

Description

Technical Field

[0001] The present disclosure relates to a gas laser device, a temperature control method of laser gas, and a method for manufacturing an electronic device. Background Art

[0002] In recent years, semiconductor exposure equipment has been required to achieve higher resolution as semiconductor integrated circuits become increasingly miniaturized and highly integrated. Consequently, there has been a trend toward shorter wavelengths of light emitted from exposure light sources. For example, gas laser devices used for exposure include KrF excimer lasers, which output laser light with a wavelength of approximately 248 nm, and ArF excimer lasers, which output laser light with a wavelength of approximately 193 nm.

[0003] The spectral line width of the natural oscillation light of KrF excimer laser devices and ArF excimer laser devices is relatively wide, ranging from 350 to 400 pm. Therefore, when a projection lens is constructed using a material that transmits ultraviolet light such as KrF and ArF laser light, chromatic aberration may sometimes occur. As a result, the resolution may be reduced. Therefore, it is necessary to narrow the spectral line width of the laser light output from the gas laser device to a level that can eliminate chromatic aberration. Therefore, in order to narrow the spectral line width, the laser resonator of the gas laser device sometimes has a narrowing module (Line Narrowing Module: LNM) containing narrowing elements (etalon, grating, etc.). Hereinafter, a gas laser device with a narrowed spectral line width is referred to as a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent Application Publication No. 2017 / 0149199

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-10553

[0008] Patent Document 3: U.S. Patent Application Publication No. 2021 / 0367390

[0009] Patent Document 4: Japanese Patent Application Laid-Open No. 2003-86874 Summary of the Invention

[0010] A gas laser device according to one aspect of the present disclosure outputs pulsed laser light, wherein the gas laser device comprises: a laser cavity that accommodates laser gas; a discharge electrode that is arranged in the laser cavity and excites discharge in the laser gas; an optical element that is arranged in an optical path of the pulsed laser light; and a processor that changes a target temperature of the laser gas based on either the number of pulses of the pulsed laser light or the elapsed time of outputting the pulsed laser light.

[0011] Another aspect of the present disclosure is a method for controlling the temperature of laser gas in a gas laser device that outputs pulsed laser light, wherein the gas laser device comprises: a laser cavity that accommodates the laser gas; a discharge electrode that is arranged in the laser cavity and excites the laser gas to discharge; an optical element that is arranged in an optical path of the pulsed laser light; and a processor. The method for controlling the temperature of laser gas includes the following steps: the processor changes the target temperature of the laser gas according to either the number of pulses of the pulsed laser light or the elapsed time of the output pulsed laser light.

[0012] Another aspect of the present disclosure provides a method for manufacturing an electronic device, comprising the following steps: generating laser light by a gas laser device, outputting the laser light to an exposure device, and exposing the laser light on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the gas laser device comprises: a laser cavity for accommodating laser gas; a discharge electrode disposed in the laser cavity for performing discharge excitation on the laser gas; an optical element disposed on an optical path of the pulsed laser; and a processor for changing a target temperature of the laser gas according to either the number of pulses of the pulsed laser output by the discharge excitation or the elapsed time of the output pulsed laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Several embodiments of the present disclosure are described below by way of example only with reference to the accompanying drawings.

[0014] Figure 1 The structure of a gas laser device according to a comparative example is schematically shown.

[0015] Figure 2 Yes Figure 1 The laser oscillator system is shown rotated 90° to the left.

[0016] Figure 3 This is a flow chart of laser oscillation operation in a gas laser device of a comparative example.

[0017] Figure 4 This is a flow chart of the temperature control of the laser gas.

[0018] Figure 5 is shown to be applied to Figure 4 This is a flowchart of a subroutine for the laser gas temperature control mode change process of step S26.

[0019] Figure 6 This is a graph showing the transition of the laser gas temperature in a gas laser device according to a comparative example.

[0020] Figure 7 An example of the intensity distribution of the pulsed laser light output from the laser oscillator system, that is, the beam profile is shown.

[0021] Figure 8 This is a graph showing an example of the transition of the target temperature in the laser gas temperature control of the gas laser apparatus according to the first embodiment.

[0022] Figure 9 This is a graph showing another example of the transition of the target temperature in the laser gas temperature control of the gas laser apparatus according to the first embodiment.

[0023] Figure 10 This is a graph showing another example of the transition of the target temperature in the laser gas temperature control of the gas laser apparatus according to the first embodiment.

[0024] Figure 11 Examples of beam profiles of pulsed laser light output during control at target temperatures varied within a range of 65° C. to 100° C. are shown.

[0025] Figure 12 This is a flowchart of laser gas temperature control in the gas laser device according to the first embodiment.

[0026] Figure 13 is shown to be applied to Figure 12 This is a flowchart of a subroutine of a target temperature change process of step S50.

[0027] Figure 14 is shown to be applied to Figure 12 This is a flowchart of a subroutine for the laser gas temperature control mode change process of step S56.

[0028] Figure 15 These are examples of the beam profile when the laser gas temperature is 65°C and the average beam profile obtained when the target temperature is changed within the range of 65°C to 100°C.

[0029] Figure 16 This is a graph comparing the peak intensities in the respective beam profiles when the average beam profile is calculated while changing the target temperature fluctuation range.

[0030] Figure 17 This is a graph showing an example of the transition of the target temperature in the laser gas temperature control of the gas laser device according to the second embodiment.

[0031] Figure 18 This is a graph showing another example of the transition of the target temperature in the laser gas temperature control of the gas laser device according to the second embodiment.

[0032] Figure 19 This is a graph showing another example of the transition of the target temperature in the laser gas temperature control of the gas laser device according to the second embodiment.

[0033] Figure 20 This is a flowchart of laser gas temperature control in the gas laser device according to the second embodiment.

[0034] Figure 21 The structure of the gas laser device according to the third embodiment is schematically shown.

[0035] Figure 22 Yes Figure 21 The laser amplifier system in FIG is rotated 90° to the left.

[0036] Figure 23 The structure of the exposure device is schematically shown. DETAILED DESCRIPTION

[0037] -Table of contents-

[0038] 1. Overview of Comparative Example Gas Laser Device

[0039] 1.1 Structure

[0040] 1.2 Action

[0041] 1.3 Topics

[0042] 2. Implementation Method 1

[0043] 2.1 Structure

[0044] 2.2 Action

[0045] 2.3 Effects

[0046] 3. Implementation Method 2

[0047] 3.1 Structure

[0048] 3.2 Action

[0049] 3.3 Function / Effect

[0050] 4. Implementation Method 3

[0051] 4.1 Structure

[0052] 4.2 Action

[0053] 4.3 Action / Effect

[0054] 5. Implementation Method 4

[0055] 5.1 Structure

[0056] 5.2 Action

[0057] 5.3 Action / Effect

[0058] 6. Implementation Method 5

[0059] 6.1 Structure

[0060] 6.2 Action

[0061] 6.3 Action / Effect

[0062] 7. Regarding the manufacturing method of electronic devices

[0063] 8. Others

[0064] Below, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. The embodiments described below illustrate several examples of the present disclosure and do not limit the content of the present disclosure. In addition, the structures and actions described in each embodiment are not necessarily all required structures and actions of the present disclosure. In addition, the same reference numerals are given to the same structural elements, and repeated descriptions are omitted.

[0065] 1. Overview of Comparative Example Gas Laser Device

[0066] 1.1 Structure

[0067] Figure 1 A diagram showing the structure of a gas laser device 1 according to a comparative example is provided. The comparative examples disclosed herein are methods known only to the applicant and are not publicly known examples acknowledged by the applicant. The gas laser device 1 is an excimer laser device comprising a laser oscillator system 4, a laser gas supply and exhaust system 6, and a laser control processor 8.

[0068] The laser oscillator system 4 includes a laser cavity 10 , a narrowband module (LNM) 12 , an output coupler (OC) 14 , a power monitor 16 , and a charger 18 .

[0069] Laser gas containing fluorine is contained in a laser cavity 10. Disposed within the laser cavity 10 are a pair of discharge electrodes 20a and 20b, which excite the laser gas for discharge; a pulse power module (PPM) 24, which includes a switch 22 that causes the discharge electrodes 20a and 20b to generate pulsed discharges; an electrical insulator 26; and a feedthrough 28. Discharge electrode 20a is a cathode electrode, and discharge electrode 20b is an anode electrode. Electrical insulator 26 supports discharge electrode 20a, insulating it from PPM 24.

[0070] The PPM 24 includes a charging capacitor (not shown) and is connected to the discharge electrode 20a via the feedthrough 28. The charger 18 is connected to the charging capacitor of the PPM 24. The voltage generated by the PPM 24 is applied to the discharge electrode 20a via the feedthrough 28.

[0071] Furthermore, laser cavity 10 is equipped with a pressure sensor 30, a crossflow fan 34, a shaft 36 for rotating crossflow fan 34, a bearing 38 for securing shaft 36, and a motor 40 for applying driving force to shaft 36. Pressure sensor 30 measures the total pressure of the laser gas. Crossflow fan 34 rotates within laser cavity 10, circulating the laser gas. The rotation of crossflow fan 34 circulates the laser gas within laser cavity 10.

[0072] LNM 12 includes a grating 44 and a beam-expanding prism 42. Grating 44 is configured in a Littrow configuration so that the incident angle and diffraction angle are equal. OC 14 is a partially reflecting mirror coated with a multilayer film that reflects a portion of the laser light generated within laser cavity 10 and transmits another portion. OC 14 and LNM 12 together constitute a laser resonator. Laser cavity 10 has two windows 46 and 47 that transmit light from the laser resonator and are located on the optical path of the laser resonator.

[0073] The power monitor 16 includes a beam splitter 50 , a condenser lens 52 , and a photosensor 54 , which are arranged on the optical path of the laser light output from the OC 14 .

[0074] The laser gas supply and exhaust system 6 includes a laser gas supply system and a laser gas exhaust system (not shown). The laser gas supply system includes a flow control valve connected to a gas cylinder serving as a laser gas supply source. The laser gas exhaust system includes an on-off valve and an exhaust pump. Laser gas may be, for example, Ar or Kr as a rare gas, F₂ as a halogen gas, Ne or He as a buffer gas, or a mixture thereof.

[0075] Figure 2 Show Figure 1 The structure of the laser oscillator system 4 shown is rotated 90° to the left. The laser cavity 10 is equipped with a heat exchanger 60, a temperature sensor 62, an insulating guide 64 and a metallic guide 66 for rectifying the laser gas flow, a preionization outer electrode 68 for generating corona discharge, a preionization inner electrode 70 and a dielectric tube 72, a ground plate 74, and wiring 76 and 77 for securing the ground plate 74 to the laser cavity 10. The heat exchanger 60 changes the temperature of the laser gas circulating within the laser cavity 10. The temperature sensor 62 detects the temperature of the laser gas.

[0076] The gas laser device 1 includes a laser gas temperature control system 80 that controls the temperature of the laser gas circulating within the laser cavity 10. The laser gas temperature control system 80 includes a laser control processor 8, a temperature sensor 62, a heat exchanger 60, refrigerant pipes 82 and 83 that circulate refrigerant within the heat exchanger 60, and a cooler 84 that supplies refrigerant to the heat exchanger 60 via the refrigerant pipes 82 and 83.

[0077] Refrigerant piping 82 includes a flow sensor 86 and a valve 88. Flow sensor 86 detects the flow rate of the refrigerant flowing through refrigerant piping 82. Information on the flow rate detected by flow sensor 86 is transmitted to the laser control processor 8. Valve 88 is a valve that can be opened and closed by signals from the laser control processor 8 to adjust the refrigerant flow rate. Valve 88 can be an on-off valve or a flow control valve.

[0078] A cooler 84 for cooling the refrigerant flowing therein is connected to heat exchanger 60 . Cooler 84 can freely change the set temperature of the refrigerant according to instructions from laser control processor 8 , thereby controlling the temperature of the laser gas inside laser cavity 10 .

[0079] The laser control processor 8 is electrically connected to the temperature sensor 62 and can measure the temperature of the laser gas inside the laser cavity 10 based on the output signal of the temperature sensor 62. The laser control processor 8 controls the valve 88 based on the measurement result of the temperature sensor 62. In addition, a plurality of gas laser devices (not shown) may be connected to the cooler 84. In addition, the cooler 84 may also be connected to other devices (not shown).

[0080] The laser control processor 8 functions as a control device for the gas laser device 1. The laser control processor 8 is a processing device including a storage device storing a control program and a CPU (Central Processing Unit) that executes the control program. The laser control processor 8 is specially configured or programmed to perform the various processes included in the present disclosure. The storage device is a non-temporary computer-readable medium that is a tangible object, for example, including a memory as a main storage device and a storage unit as an auxiliary storage device. The computer-readable medium can be, for example, a semiconductor memory, a hard disk drive (HDD) device, or a solid state drive (SSD) device, or a combination thereof. The laser control processor 8 is electrically connected to the exposure device control processor 92 of the exposure device 90.

[0081] 1.2 Action

[0082] The laser cavity 10 is filled with laser gas supplied from the laser gas supply system. The laser gas is circulated along the laser cavity 10 by the continuously rotating cross-flow fan 34. Figure 2 The cycle continues in the direction of the hollow arrow A.

[0083] The laser gas is rectified by the inclined surfaces of insulating guide 64 and metallic guide 66 and supplied to the discharge space. The discharge space comprises the space between discharge electrodes 20a and 20b. This rectification increases the flow rate of the laser gas through the discharge space, effectively removing discharge products generated there. Consequently, arc discharge caused by these products is suppressed.

[0084] Figure 3 Flowchart of laser oscillation operation in the gas laser device 1 of the comparative example. Figure 3 When the laser oscillation process shown in FIG. 1 is started, in step S11, the laser control processor 8 determines whether the temperature of the laser gas is being controlled. If the determination result of step S11 is "No", that is, if the temperature control of the laser gas has not started, the laser control processor 8 repeats step S11. On the other hand, if the determination result of step S11 is "Yes", that is, after the temperature control of the laser gas has started, the laser control processor 8 proceeds to step S12. In addition, the temperature control process of the laser gas uses Figure 4 This will be described later.

[0085] In step S12, the laser control processor 8 applies a high voltage to the charger 18 based on the emission trigger signal and target pulse energy received from the exposure device control processor 92, thereby causing the laser to oscillate. Upon receiving the emission trigger signal from the exposure device control processor 92, the laser control processor 8 activates the switch 22 within the PPM 24, applying a high voltage across the preionization outer electrode 68 and preionization inner electrode 70, which serve as preionization electrodes, and the discharge electrodes 20a and 20b, which serve as main discharge electrodes, within the laser cavity 10.

[0086] As a result, corona discharge first occurs at the pre-ionization electrode, generating discharge ultraviolet light (UV light). UV light irradiates the laser gas between the main discharge electrodes, pre-ionizing the laser gas. A main discharge then occurs between discharge electrodes 20a and 20b, exciting the laser gas and causing laser oscillation in the laser resonator formed by OC14 and grating 44.

[0087] At this time, pulsed laser light narrowed by prism 42 and grating 44 is output from OC 14. Part of the pulsed laser light output from OC 14 enters power monitor 16, while part is reflected by beam splitter 50, passes through condenser lens 52, and is detected by optical sensor 54.

[0088] The pulse energy of the output laser light detected by the power monitor 16 is input to the laser control processor 8. Based on the output of the power monitor 16, the laser control processor 8 uses its own counter circuit to count the number of laser pulses. Alternatively, pulse counts can be accumulated based on a light emission trigger signal. After passing through the beam splitter 50, the laser light is output toward the exposure device 90.

[0089] In step S13, the laser control processor 8 determines whether to interrupt laser oscillation based on a signal from the exposure device control processor 92. If the determination result in step S13 is "No," that is, while the laser control processor 8 has not received a signal from the exposure device control processor 92 to interrupt exposure, the process returns to step S12 and repeats the subsequent steps. Furthermore, while the gas laser device 1 is operating, the laser control processor 8 performs feedback control on the high voltage charged to the charger 18 based on the difference between the target pulse energy and the actual output pulse energy.

[0090] If the result of determination in step S13 is “Yes”, that is, if the laser control processor 8 receives a signal to interrupt exposure from the exposure device control processor 92 , the process proceeds to step S14 .

[0091] In step S14, the laser control processor 8 stops laser oscillation or stops outputting laser light to the exposure device 90 by moving the shutter on the laser light path. Figure 3 Flowchart of the process.

[0092] Figure 4 This is a flow chart of the temperature control of the laser gas in the gas laser device 1. Figure 4 When the laser gas temperature control process shown starts, in step S21, the laser control processor 8 sets the target temperature T0 of the laser gas to output pulse laser light with the target pulse energy. Note that the target temperature T0 is a temperature of a predetermined value corresponding to the target pulse energy.

[0093] In step S22 , the laser control processor 8 obtains the current laser gas temperature T1 in the laser cavity 10 based on the output of the temperature sensor 62 .

[0094] In step S23, the laser control processor 8 determines whether to stop temperature control based on a signal from the exposure device control processor 92. If the result of the determination in step S23 is "No," that is, if the laser control processor 8 has not received a stop signal, the process proceeds to step S24 to continue temperature control.

[0095] In step S24, the laser control processor 8 compares the laser gas temperature T1 with the target temperature T0 to determine whether T1 = T0 is satisfied. When the determination result in step S24 is "yes", that is, when it is determined that the laser gas temperature T1 is equal to the target temperature T0, the laser control processor 8 returns to step S22.

[0096] When the determination result in step S24 is "no", that is, when it is determined that the laser gas temperature T1 is not the target temperature T0, the laser control processor 8 proceeds to step S26.

[0097] In step S26, the laser control processor 8 performs a change process of the laser gas temperature control mode. In step S26, the laser gas temperature control system 80 performs an operation of changing the cooling effect applied to the laser gas so that the laser gas temperature T1 reaches the target temperature T0. The details of the change process of the laser gas temperature control mode applied to step S26 are described later. After step S26, the laser control processor 8 returns to step S22. Figure 5 After step S26, the laser control processor 8 returns to step S22.

[0098] When the determination result in step S23 is "yes", that is, when the laser control processor 8 receives a stop signal, the flowchart ends, and the temperature control is stopped. Figure 4 and stops the temperature control.

[0099] Figure 5 is a flowchart of a subroutine showing the change process of the laser gas temperature control mode applied to Figure 4 step S26. Figure 5 The operation process shown is premised on controlling the flow rate of the refrigerant supplied to the heat exchanger 60 by opening and closing the valve 88 in the laser gas temperature control system 80. However, it is not limited to this example, and methods of controlling the temperature of the refrigerant supplied from the cooler 84 or methods combining them can also be used to control the laser gas temperature. In addition, the opening and closing of the valve 88 can be simple opening and closing control or flow rate control capable of changing the flow rate hierarchically or continuously. The opening and closing control of the valve 88 is an example of a method of adjusting the flow rate of the refrigerant.

[0100] At Figure 5 the start of the change process of the laser gas temperature control mode shown, in step S261, the laser control processor 8 determines whether the current laser gas temperature T1 is lower or higher than the target temperature T0. For example, the laser control processor 8 determines whether T1 < T0 is satisfied. When the determination result in step S261 is "yes", the laser control processor 8 determines that the laser gas temperature T1 has not reached the target temperature T0 and needs to be heated, and proceeds to step S262.

[0101] In step S262, the laser control processor 8 determines the open / close state of the valve 88. For example, the laser control processor 8 determines whether the valve 88 is in the open state. If the result of the determination in step S262 is "yes," that is, if the valve 88 is in the open state, the process proceeds to step S263.

[0102] In step S263, the laser control processor 8 closes valve 88 and stops supplying refrigerant to reduce the cooling effect. By stopping the supply of refrigerant, the cooling effect of the heat exchanger 60 is reduced, and the laser gas temperature T1 gradually rises. The action of increasing the laser gas temperature T1 as in step S263 is defined as "temperature increase mode". After step S263, the laser control processor 8 ends. Figure 5 Flowchart of , returns Figure 4 Flowchart of the process.

[0103] On the other hand, if the result of the determination in step S262 is "No", that is, if the valve 88 is in the closed state, the cooling effect is already low, and therefore, the valve 88 is still closed, and the laser control processor 8 ends. Figure 5 Flowchart of , returns Figure 4 Flowchart of the process.

[0104] If the result of determination in step S261 is "No," the laser control processor 8 determines that the laser gas temperature T1 is higher than the target temperature T0 and needs to be lowered, and the process proceeds to step S264.

[0105] In step S264, the laser control processor 8 determines the open / close state of the valve 88. For example, the laser control processor 8 determines whether the valve 88 is in the closed state. If the result of the determination in step S264 is "yes," that is, if the valve 88 is in the closed state, the process proceeds to step S265.

[0106] In step S265, laser control processor 8 opens valve 88 and resumes refrigerant supply to enhance the cooling effect. Resuming refrigerant supply enhances the cooling effect of heat exchanger 60, gradually lowering laser gas temperature T1. The operation of lowering laser gas temperature T1 in step S265 is defined as "cooling mode."

[0107] On the other hand, if the result of the determination in step S264 is "No", that is, if the valve 88 is in the open state, the cooling effect is already high, and therefore, the valve 88 is still open, and the laser control processor 8 ends. Figure 5 Flowchart of , returns Figure 4 Flowchart of the process.

[0108] Here, the target temperature T0 is, in principle, set to a fixed value during product adjustment of the gas laser device 1, and the gas laser device 1 is used with the target temperature T0 set. Typically, the target temperature T0 is, for example, 65°C. Figure 5 The change of the laser gas temperature control mode described in is performed independently of the presence or absence of laser oscillation.

[0109] Through the above actions, such as Figure 6 As shown, the pulse laser light is output in a state controlled so as to keep the laser gas temperature T1 constant, regardless of the elapse of the laser oscillation time and the elapse of the number of output pulses. Figure 6 The horizontal axis can be time or pulse number.

[0110] 1.3 Topics

[0111] Figure 7 An example of the intensity distribution of the pulsed laser light output from the laser oscillator system 4 , that is, the beam profile is shown. Figure 7 The V direction (vertical axis) in FIG. 5 represents the discharge direction, and the H direction (horizontal axis) represents the electrode width direction of the discharge electrodes 20 a and 20 b. Figure 7 The figure shows the beam profile of the pulsed laser output from the laser oscillator system 4, which operates at a temperature of 65°C and an oscillation frequency of 6000 Hz in the laser cavity 10. This beam profile is obtained by simulating the density distribution of the acoustic waves generated by the internal structure of the laser cavity 10 and calculating the beam profile (the result of the simulation). Figure 7 In FIG. 1 , a beam profile is shown that expresses the intensity distribution of the beam by a light and dark heat map, and the greater the intensity, the brighter (higher brightness) the beam profile is displayed.

[0112] It can be seen that in the outgoing beam output from the laser oscillator system 4, the refractive index distribution is generated by the density of the acoustic waves generated in the laser cavity 10 during the discharge, resulting in an intensity distribution within the beam profile. The acoustic waves here refer to the shock waves generated in the discharge space by the pulse discharge. These shock waves are reflected by the ground plate 74, dielectric tube 72, and insulating guide 64 around the discharge electrodes 20a and 20b and return to the discharge space, causing density fluctuations in the laser gas in the discharge space. Figure 2 The image of the sound wave is schematically illustrated in FIG.

[0113] Figure 7 The beam profile shown is an intensity distribution calculated through simulation. However, actual beam profile measurements confirmed that the same intensity distribution as the simulation results was also observed. In this case, OC14 exhibited localized degradation at the peak intensity position within the beam profile. This degradation is not limited to OC14; it can also occur in optical components such as windows 46 and 47 and prism 42.

[0114] Specifically, the density distribution of the laser gas in the discharge space changes due to the influence of acoustic waves. This change in density distribution produces an intensity distribution in the pulsed laser. While the difference in the intensity distribution of pulsed laser light is relatively small within each pulse, the intensity distribution accumulates in the optical element during repeated oscillations, potentially causing localized degradation. Consequently, the life of the optical element is shortened.

[0115] 2. Implementation Method 1

[0116] 2.1 Structure

[0117] The gas laser device of the first embodiment differs from the gas laser device 1 of the comparative example in that the target temperature in the laser gas temperature control is changed according to the accumulated value of the number of pulses. Figure 1 and Figure 2 The structure of the gas laser devices 1 shown is the same.

[0118] 2.2 Action

[0119] Figure 8 This is a graph showing an example of the transition of the target temperature in the laser gas temperature control of the gas laser device of embodiment 1. The horizontal axis shows the number of pulses, and the vertical axis shows the target temperature. Figure 8 As shown, the laser control processor 8 in Embodiment 1 changes the target temperature Tc of the laser gas within the laser cavity 10 in multiple steps within the range of a target lower limit temperature Tc_LL to a target upper limit temperature Tc_UL, each time a certain number of pulses are passed. This causes the target temperature Tc to change periodically. The term "period" here refers to the period from when the target temperature Tc changes slightly from Tc_LL to when it returns to Tc_LL after passing through Tc_UL, while the target temperature Tc changes slightly according to the number of pulses or the elapsed time.

[0120] exist Figure 8 In the example shown below, Tc_LL is set to 65°C, Tc_UL is set to 100°C, and the target temperature Tc is changed by 1°C every time the number of pulses increases by 10 Mpls (megapulses). In this case, the cycle becomes 700 Mpls. The cycle of the target temperature Tc change is preferably 350 Mpls to 3500 Mpls. Figure 8 The figure shows the transition of one cycle, but Figure 8 In the cycle shown, the target temperature Tc is changed periodically and repeatedly.

[0121] The method of changing the target temperature Tc in a plurality of steps within the range of Tc_LL to Tc_UL at every certain number of pulses in response to an increase in the number of pulses is not limited to Figure 8 The target temperature Tc can also be along Figure 8Such a triangular wave changes in steps, is not limited to a triangular wave, and can also be changed along Figure 9 The sine wave shown here is Figure 10 The sawtooth wave shown is changed. Figures 8 to 10 The changes in the target temperature Tc shown are examples of a method of periodically changing the target temperature Tc within the range of Tc_LL to Tc_UL.

[0122] Figure 11 The following shows an example of the beam profile of the pulsed laser outputted during control at each target temperature Tc changed within the range of 65°C to 100°C. Figure 11 In, with Figure 7 Similarly, the intensity distribution calculated by simulation is shown. The speed of sound in the gas depends on the temperature of the gas. Therefore, by changing the temperature in the laser cavity 10, the density distribution of the sound wave changes. As a result, Figure 11 As shown, the beam profile varies depending on the temperature of the laser gas.

[0123] From the viewpoint of the degradation rate of the optical element and the stability of output performance, the target temperature Tc is preferably changed by, for example, approximately 1° C. per 10 Mpls.

[0124] Figure 12 This is a flow chart of laser gas temperature control in the gas laser device of embodiment 1. Figure 12 At the start of the temperature control process shown, in step S40, the laser control processor 8 sets the target lower limit temperature Tc_LL, target upper limit temperature Tc_UL, target temperature Tc, target temperature difference ΔT, laser oscillation pulse number step Ns, and target temperature adjustment flag X for the laser gas. Specific values ​​are shown, for example, for Tc_LL to be 65°C, and for Tc_UL to be 100°C. Tc_LL is an example of a "lower limit temperature" in this disclosure, and Tc_UL is an example of an "upper limit temperature" in this disclosure. The initial value of Tc can be either Tc_LL or Tc_UL, or a temperature between Tc_LL and Tc_UL. ΔT is the amount of change required to slightly change the target temperature Tc. ΔT can be, for example, 0.5°C to 1°C. Ns represents the number of pulses that specifies the timing for changing the target temperature Tc by ΔT. Each time the count value (cumulative value) obtained by counting the number of pulses reaches Ns, the target temperature Tc is slightly changed. Ns can be, for example, 5 Mpls to 50 Mpls. X is a flag for determining whether to increase or decrease the target temperature Tc. The initial value of X is set to "1", for example.

[0125] In step S42, the laser control processor 8 resets the pulse counter. That is, the laser control processor 8 initializes the value of the pulse number N stored in its own counter circuit to N=0.

[0126] In step S44, the laser control processor 8 determines whether pulsed laser light is detected. If the result of step S44 is "No," that is, if the output of the power monitor 16 does not exceed the threshold, the laser control processor 8 determines that pulsed laser light is not being output and repeats step S44.

[0127] On the other hand, if the result of step S44 is "yes," that is, if the output of power monitor 16 exceeds the threshold, laser control processor 8 determines that pulsed laser light is being output, and the process proceeds to step S46. Alternatively, instead of step S44, the presence or absence of an input light emission trigger signal may be detected. When the number of pulses of the pulsed laser light is counted based on the light emission trigger signal, the process proceeds to step S46 if the light emission trigger signal is input.

[0128] In step S46 , the laser control processor 8 increments the counter of the counter circuit to count and accumulate the number of pulses N.

[0129] In step S48, the laser control processor 8 determines whether the number of pulses N has reached the pulse number step Ns. If the result of the determination in step S48 is "No", that is, if the number of pulses N has not reached Ns, the process proceeds to step S54. On the other hand, if the result of the determination in step S48 is "Yes", that is, if the number of pulses N has reached Ns, the process proceeds to step S50 to execute the process of changing the target temperature Tc of the laser gas. The details of the process flow applied to step S50 are described in detail using Figure 13 This will be described later.

[0130] After the target temperature Tc of the laser gas is changed in step S50, the process proceeds to step S52. In step S52, the laser control processor 8 resets the pulse counter, that is, sets the pulse number N to "0".

[0131] In step S54 , the laser control processor 8 measures the current laser gas temperature T1 in the laser cavity 10 based on the output of the temperature sensor 62 .

[0132] In step S56, the laser control processor 8 performs temperature control of the laser gas at the target temperature Tc. The details of the laser gas temperature control mode change process applied to step S56 are as follows: Figure 14 This will be described later.

[0133] In step S58, the laser control processor 8 determines whether to stop the temperature control. If the determination result of step S58 is "No", the laser control processor 8 returns to step S44. If the determination result of step S58 is "Yes", the laser control processor 8 ends the temperature control. Figure 12 Flowchart of the process.

[0134] Figure 13 is shown to be applied to Figure 12 Flowchart of the subroutine of the target temperature Tc change process in step S50. Figure 13 When the target temperature Tc change process shown begins, in step S501, the laser control processor 8 determines whether the target upper limit temperature Tc_UL is exceeded when the target temperature Tc of the laser gas is changed by X·ΔT. If the result of step S501 is "yes," the laser control processor 8 determines that the temperature needs to be lowered and proceeds to step S502. In step S502, the laser control processor 8 sets the value of the target temperature adjustment flag X to "-1" to initiate the temperature reduction. After step S502, the process proceeds to step S505.

[0135] On the other hand, if the result of determination in step S501 is "No", the laser control processor 8 determines that it is necessary to increase the temperature or maintain the current state, and proceeds to step S503.

[0136] In step S503, the laser control processor 8 determines whether the target temperature Tc of the laser gas, after changing it by X·ΔT, falls below the target lower limit temperature Tc_LL. If the determination result in step S503 is "yes," the laser control processor 8 determines that a temperature increase is necessary and proceeds to step S504. In step S504, the laser control processor 8 sets the value of the target temperature adjustment flag X to "1" to initiate a temperature increase. After step S504, the process proceeds to step S505.

[0137] On the other hand, when the result of determination in step S503 is "No", the laser control processor 8 determines that the current temperature change policy should be maintained, and the process proceeds to step S505.

[0138] In step S505 , the laser control processor 8 changes the target temperature Tc by X·ΔT to update the value of the target temperature Tc.

[0139] After step S505, the laser control processor 8 ends Figure 13 Flowchart of , returns Figure 12 Flowchart of the process.

[0140] Figure 14 is shown to be applied to Figure 12This is a flowchart of the subroutine for the laser gas temperature control mode change process of step S56. Figure 14 When the laser gas temperature control mode change process shown begins, in step S561, the laser control processor 8 determines whether the current laser gas temperature T1 is lower than the target temperature Tc. If the result of step S561 is "yes," that is, if the current laser gas temperature T1 has not reached the target temperature Tc, the laser control processor 8 determines that the temperature needs to be increased and proceeds to step S562.

[0141] On the other hand, when the result of the determination in step S561 is "No", that is, when the current laser gas temperature T1 exceeds the target temperature Tc, the laser control processor 8 determines that the temperature must be lowered, and proceeds to step S564.

[0142] Each step of step S562 to step S565 is the same as Figure 5 The laser control processor 8 controls the valve 88 based on the measurement result of the temperature sensor 62 to adjust the flow rate of the refrigerant so that the laser gas approaches the target temperature Tc.

[0143] In this way, the laser control processor 8 periodically repeats the operation of changing the target temperature Tc after the pulse number N is increased by Ns according to the count value of the pulse number N. The temperature control method of the laser gas in the first embodiment is an example of the temperature control method of the laser gas in the present disclosure. Figures 12 to 14 The laser control processor 8 in the flowchart is an example of a “processor” in the present disclosure.

[0144] 2.3 Effects

[0145] Figure 15 The figure shows a comparison of the beam profile obtained when the laser gas temperature is 65°C (F15A) and the average beam profile obtained when the target temperature Tc is changed within the range of 65°C to 100°C (F15B). 65°C is an example of a "specific temperature" in the present disclosure. The beam profiles obtained at each temperature when the target temperature Tc is changed within the range of 65°C to 100°C at a constant number of pulses (see Figure 11 ) When the average beam profile is calculated, the beam profile shown in FIG. F15B on the right is obtained by integrating the beam profiles at temperatures between 65°C and 100°C and dividing the accumulated beam profiles by the number of shots.

[0146] about Figure 15For each beam profile shown in the left figure F15A and the right figure F15B, when calculating the peak intensity relative to the average intensity within the beam profile, the peak intensity of the beam profile at 65°C (left figure F15A) is used as a benchmark, and the peak intensity of the average beam profile from 65°C to 100°C (right figure F15B) is reduced to 44% relative to this benchmark.

[0147] Figure 16 This is a graph comparing the peak intensities in each beam profile (BP) when the average beam profile is calculated by changing the range of target temperature Tc. Figure 16 , the peak intensity within the beam profile at 65°C, which serves as a comparison benchmark, is set to 1.00, and the peak intensities within each average beam profile are shown when the variation range of the target temperature Tc is set to "65°C to 75°C", "65°C to 85°C", "65°C to 95°C" and "65°C to 100°C".

[0148] like Figure 16 As shown, the peak intensity of the average beam profile when the temperature changes from 65 to 75°C is 78% of the peak intensity of the beam profile at 65°C, the peak intensity of the average beam profile when the temperature changes from 65 to 85°C is 60% of the peak intensity of the beam profile at 65°C, and the peak intensity of the average beam profile when the temperature changes from 65 to 95°C is 49% of the peak intensity of the beam profile at 65°C.

[0149] By changing the laser gas temperature within the laser cavity 10 in this way, the local beam intensity within the average beam profile is reduced. If damage to optical components placed in the laser optical path is considered to be caused by two-photon absorption, the probability of two-photon absorption is proportional to the square of the laser intensity. Therefore, for example, if the beam intensity is reduced to 44% at an average temperature of 65°C to 100°C, the probability of two-photon absorption is reduced to one-fifth of that at 65°C, and the lifetime is expected to be extended by approximately five times.

[0150] It is preferable to adjust the target temperature range so that the peak intensity of the average beam profile is suppressed to 70% or less of the peak intensity of the beam profile at 65°C (the peak intensity of the benchmark) to achieve a life that is more than twice that of the conventional beam profile. It is more preferable to adjust the target temperature range so that the peak intensity of the average beam profile is less than 57% of the peak intensity of the benchmark to achieve a life that is more than three times that of the conventional beam profile. It is further preferable to adjust the target temperature range so that the peak intensity of the average beam profile is less than 50% of the peak intensity of the benchmark to achieve a life that is more than four times that of the conventional beam profile. It is further preferable to adjust the target temperature range so that the peak intensity of the average beam profile is less than 44% of the peak intensity of the benchmark to achieve a life that is more than five times that of the conventional beam profile. The target temperature range is a fluctuation range of the target temperature Tc defined by the target lower limit temperature Tc_LL and the target upper limit temperature Tc_UL, and the target temperature range is adjusted by setting the target lower limit temperature Tc_LL and the target upper limit temperature Tc_UL.

[0151] As described above, according to Embodiment 1, by varying the laser gas temperature every certain number of pulses, the density distribution of the laser gas in the discharge space changes, thereby varying the intensity distribution of the pulsed laser light. This change in intensity distribution balances the intensity distribution accumulated by optical components such as the OC14. As a result, localized degradation of the optical components is suppressed, extending their lifespan.

[0152] 3. Implementation Method 2

[0153] 3.1 Structure

[0154] The gas laser device of Embodiment 2 differs from the gas laser device of Embodiment 1 in that the target temperature Tc used in laser gas temperature control is changed based on the elapsed time. Specifically, while in Embodiment 1, the target temperature Tc is changed based on the number of pulses, in Embodiment 2, the target temperature Tc is changed based on the elapsed time during which pulsed laser output has been performed, rather than the number of pulses. This elapsed time can also be understood as the accumulated time of laser oscillation. The remaining configuration is the same as that of the gas laser device of Embodiment 1.

[0155] 3.2 Action

[0156] Figure 17 This is a graph showing an example of the transition of the target temperature Tc in the laser gas temperature control of the gas laser device according to the second embodiment. The horizontal axis shows time, and the vertical axis shows the target temperature Tc. Figure 17 As shown, the laser control processor 8 in the second embodiment changes the target temperature Tc of the laser gas inside the laser cavity 10 in multiple steps within the range of the target lower limit temperature Tc_LL to the target upper limit temperature Tc_UL at every predetermined time, thereby periodically changing the target temperature Tc.

[0157] exist Figure 17 In the example shown below, Tc_LL is set to 65°C, Tc_UL is set to 100°C, and the target temperature Tc is changed by 1°C every time the elapsed time increases by 1 hour (60 minutes). In this case, the cycle becomes 70 hours (4200 minutes). The preferred cycle for changing the target temperature Tc is 2100 minutes to 21000 minutes. Figure 17 The figure shows the transition of one cycle, but Figure 17 In the cycle shown, the target temperature Tc is changed periodically and repeatedly.

[0158] The target temperature Tc can also be along Figure 17 The triangular wave shown here is changed in steps, but is not limited to the triangular wave. Figure 18 The sine wave shown here is Figure 19 The sawtooth wave shown is changed.

[0159] Figure 20 A flow chart showing the laser gas temperature control in the gas laser device according to the second embodiment is shown. Figure 20 The flowchart shown is for Figure 12 The differences between the flowcharts are explained.

[0160] Figure 20 The flowchart shown replaces Figure 12 Instead of step S40 and step S42, step S41 and step S43 are included. Figure 12 The system includes steps S46, S48 and S52 and steps S47, S49 and S53.

[0161] In step S41, the laser control processor 8 sets the target lower limit temperature Tc_LL, target upper limit temperature Tc_UL, target temperature Tc, target temperature difference ΔT, time step Δt and target temperature adjustment flag X of the laser gas. The setting of each value of Tc_LL, Tc_UL, ΔT and X can be the same as Figure 12 The time step Δt may be, for example, 30 minutes to 300 minutes.

[0162] In step S43, the laser control processor 8 resets the time counter. That is, the laser control processor 8 initializes the value of the elapsed time t stored in its own time counter circuit to t=0.

[0163] After step S43, the laser control processor 8 proceeds to step S44. If the determination result of step S44 is "Yes", the laser control processor 8 proceeds to step S47.

[0164] In step S47, the laser control processor 8 updates the time counter according to the elapsed time. That is, the time counter circuit updates the value of the elapsed time t.

[0165] In step S49 , the laser control processor 8 determines whether the elapsed time t has reached the time step Δt.

[0166] If the result of step S49 is "No," that is, if the elapsed time t has not reached Δt, the process proceeds to step S54. On the other hand, if the result of step S49 is "Yes," that is, if the elapsed time t has reached Δt, the process proceeds to step S50 to execute the process of changing the target temperature Tc of the laser gas.

[0167] After the target temperature Tc of the laser gas is changed in step S50, the process proceeds to step S53. In step S53, the laser control processor 8 resets the time counter, that is, sets the elapsed time t to "0." After step S53, the laser control processor 8 proceeds to step S54.

[0168] Other steps and Figure 12 Similarly, the subroutines applied to steps S50 and S56 are also as follows. Figure 13 and Figure 14 Like that.

[0169] In this manner, the laser control processor 8 periodically repeats the operation of changing the target temperature Tc when the elapsed time t increases by Δt based on the count value of the elapsed time t of the laser oscillation.

[0170] 3.3 Function / Effect

[0171] The functions and effects of the second embodiment are the same as those of the first embodiment.

[0172] 4. Implementation Method 3

[0173] 4.1 Structure

[0174] Figure 21 The structure of a gas laser apparatus 1A according to Embodiment 3 is schematically shown. In Embodiment 3, a control method is applied to the laser oscillator system 4 of the dual-cavity gas laser apparatus 1A, which changes the target temperature Tc of the laser gas based on the accumulated pulse count. Furthermore, Embodiment 3, similar to the example described in Embodiment 2, can also be applied to cases where the target temperature Tc is changed based on the elapsed time.

[0175] about Figure 21 The structure of the gas laser device 1A shown in FIG. Figure 1 The differences from the gas laser device 1 shown will be described.

[0176] In the dual-cavity gas laser device 1A, Figure 21 The laser amplifier system 204 shown in the upper layer is Figure 21 The laser light outputted from the laser oscillator system 4 shown in the lower layer is amplified and outputted as seed light.

[0177] In the gas laser device 1A, instead of Figure 1 The gas laser apparatus 1A includes a laser control processor 8 and a laser gas supply and exhaust system 6 for controlling the laser amplifier system 204 and the laser oscillator system 4, and a laser gas supply and exhaust system 6A for supplying laser gas to and exhausting laser gas from the respective laser cavities 10 and 210. Furthermore, the gas laser apparatus 1A includes high-reflection mirrors 151 and 152 for guiding the laser light output from the laser oscillator system 4 to the laser amplifier system 204.

[0178] The structure of the laser oscillator system 4 of the oscillation stage is Figure 1 The laser light output from the laser oscillator system 4 passes through the high-reflection mirrors 151 and 152 and is input to the partial reflection mirror 212 of the laser amplifier system 204 in the subsequent stage (amplification stage).

[0179] Laser amplifier system 204 includes a laser cavity 210, a partially reflecting mirror 212, an OC 214, a power monitor 216, and a charger 218. Laser gas containing fluorine is sealed in laser cavity 210. Laser cavity 210 is equipped with a pair of discharge electrodes 220a and 220b, a PPM 224 including a switch 222, an electrical insulator 226, and a feedthrough 228. Furthermore, laser cavity 210 is equipped with a pressure sensor 230, a crossflow fan 234, a shaft 236 for rotating crossflow fan 234, a bearing 238 for securing shaft 236, and a motor 240 for applying driving force to shaft 236. Laser cavity 210 has two windows 246 and 247 for transmitting laser light. The basic structure of laser amplifier system 204 is the same as that of laser oscillator system 4, but it does not include an LNM. Instead, laser light is amplified by an optical resonator formed by the partially reflecting mirror 212 and OC 214. The amplified laser light is output from OC 214.

[0180] The power monitor 216 has the same structure as the power monitor 16 , and includes a beam splitter 250 , a condenser lens 252 , and a photosensor 254 , which are arranged on the optical path of the laser light output from the OC 214 .

[0181] make Figure 21 The structure diagram of the laser oscillator system 4 rotated 90° to the left is the same as Figure 2 The structure of the laser gas temperature control system 80 of the laser cavity 10 is similar to that of the laser cavity 10. Figure 2 same.

[0182] 4.2 Action

[0183] When laser light is input to the laser amplifier system 204, the laser control processor 8A generates a discharge between the pair of discharge electrodes 220a and 220b of the laser amplifier system 204, thereby exciting the laser gas. This amplifies and oscillates the laser light input to the laser amplifier system 204. The laser control processor 8A causes the laser oscillator system 4 to perform the same operations as in Embodiment 1. The laser oscillator system 4 is an example of a "laser oscillator" in this disclosure. The laser amplifier system 204 is an example of a "laser amplifier" in this disclosure.

[0184] 4.3 Action / Effect

[0185] According to Embodiment 3, the average beam profile of the seed light output from the laser oscillator system 4 is similar to that of Embodiment 1, with the local peak intensity being reduced within the beam profile. Therefore, even if the laser amplifier system 204 exhibits a characteristic in which the beam intensity is locally increased within the beam profile, the laser amplifier system 204 can output amplified light with a locally low peak intensity by inputting seed light having a locally low peak intensity within the beam profile. This can suppress degradation of optical components and extend their lifespan.

[0186] 5. Implementation Method 4

[0187] 5.1 Structure

[0188] In the fourth embodiment, a control method is applied to the laser amplifier system 204 of the dual-cavity gas laser apparatus 1A, in which the target temperature of the laser gas is changed based on the accumulated value of the pulse count. Furthermore, similar to the example described in the second embodiment, the fourth embodiment can also be applied in cases where the target temperature Tc is changed based on the elapsed time.

[0189] The structure of the gas laser device 1A of the fourth embodiment can be Figure 21 However, the laser oscillator system 4 of the fourth embodiment may also not have Figure 2 Instead, the laser amplifier system 204 has the same system as the laser gas temperature control system 80 .

[0190] Figure 22 Show Figure 21The laser amplifier system 204 is rotated 90 degrees to the left. The laser cavity 210 is equipped with a heat exchanger 260, a temperature sensor 262, an insulating guide 264 and a metallic guide 266 for rectifying the laser gas, a pre-ionization outer electrode 268 for generating corona discharge, a pre-ionization inner electrode 270 and a dielectric tube 272, a ground plate 274, and wiring 276 and 277 for holding the ground plate 274 in the laser cavity 210. The structure and function of these components can be compared with the structure and function of the laser cavity 210. Figure 2 The structures and functions of the corresponding components are the same as those described in .

[0191] The gas laser device 1A includes a laser gas temperature control system 280 that controls the temperature of the laser gas circulating in the direction of arrow A within the laser cavity 210. The laser gas temperature control system 280 includes a laser control processor 8A, a temperature sensor 262, a heat exchanger 260, refrigerant pipes 282 and 283 that circulate refrigerant within the heat exchanger 260, and a cooler 284 that supplies refrigerant to the heat exchanger 260 via the refrigerant pipes 282 and 283. The refrigerant pipe 282 has a flow sensor 286 and a valve 288. The structures and functions of these components can be similar to those of FIG. Figure 2 The structures and functions of the corresponding components are the same as those described in the preceding text.

[0192] 5.2 Action

[0193] The laser control processor 8A causes the laser amplifier system 204 to perform the same operation as that in the first embodiment.

[0194] 5.3 Action / Effect

[0195] According to Embodiment 4, even when seed light having locally high intensity within the beam profile is input, amplified light with reduced local intensity can be output from the laser amplifier system 204. This can suppress degradation of optical elements and extend their lifespan.

[0196] 6. Implementation Method 5

[0197] 6.1 Structure

[0198] In the fifth embodiment, a control method for changing the target temperature Tc of the laser gas based on the accumulated value of the pulse count is applied to both the laser oscillator system 4 and the laser amplifier system 204 of the dual-cavity gas laser apparatus 1A. This control method can also be applied to changing the target temperature based on the elapsed time.

[0199] The laser oscillator system 4 and the laser amplifier system 204 are respectively Figure 21 The left-side rotated 90° structure diagram is respectively Figure 2and Figure 22 same.

[0200] 6.2 Action

[0201] The laser control processor 8A causes both the laser oscillator system 4 and the laser amplifier system 204 to perform the same operations as those in the first embodiment.

[0202] 6.3 Action / Effect

[0203] According to the fifth embodiment, the local intensity within each beam profile is reduced by both the laser oscillator system 4 and the laser amplifier system 204 . Therefore, compared with the configurations of the third and fourth embodiments, amplified light with the minimum local intensity can be output.

[0204] 7. Regarding the manufacturing method of electronic devices

[0205] Figure 23 The structure of the exposure apparatus 90 is schematically shown. The exposure apparatus 90 includes an illumination optical system 906 and a projection optical system 908. A gas laser device 1 generates laser light and outputs it to the exposure apparatus 90. The illumination optical system 906 illuminates the reticle pattern of a mask (not shown) placed on the reticle stage RT using the laser light incident from the gas laser device 1. The projection optical system 908 projects the laser light transmitted through the reticle into a reduced size, forming an image on a workpiece (not shown) placed on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0206] The exposure device 90 synchronously moves the reticle stage RT and the workpiece stage WT in parallel, thereby exposing the workpiece to laser light reflecting the reticle pattern. After the reticle pattern is transferred to the semiconductor wafer through the above exposure process, a semiconductor device can be manufactured through multiple steps. A semiconductor device is an example of an "electronic device" in this disclosure. The gas laser device 1 is not limited to the configuration of the gas laser device of Embodiment 1 or Embodiment 2; the gas laser device 1A described in Embodiments 3 to 5 may also be used.

[0207] 8. Others

[0208] In Embodiments 1 to 5, an excimer laser device is described as an example of a gas laser device. However, the technology disclosed herein is not limited to excimer laser devices, and can be applied to various gas laser devices that perform laser oscillation by discharge excitation of laser gas. Figure 21, a system using a MOPO (Master Oscillator Power Oscillator) method using a resonator in the amplification stage is described, but the present invention is not limited to this and a system using a MOPA (Master Oscillator Power Amplifier) ​​method without using a resonator in the amplification stage may also be used.

[0209] The above description is not limiting, but merely illustrative. Therefore, those skilled in the art will appreciate that modifications can be made to the embodiments of the present disclosure without departing from the scope of the claims. Furthermore, those skilled in the art will appreciate that combinations of the embodiments of the present disclosure can be used.

[0210] Unless otherwise expressly stated, the terms used in this specification and claims as a whole should be interpreted as “non-limiting” terms. For example, terms such as “including”, “having”, “having”, and “equipped” should be interpreted as “excluding the presence of structural elements other than the structural elements to be recorded”. In addition, the modifier “one” should be interpreted as meaning “at least one” or “one or more”. In addition, 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”. Furthermore, it should be interpreted as also including combinations of these and parts other than “A”, “B”, and “C”.

Claims

1. A gas laser device that outputs pulsed laser light, wherein: The gas laser device comprises: a laser cavity containing laser gas; a discharge electrode, which is disposed in the laser cavity and excites the laser gas to discharge; an optical element disposed on an optical path of the pulsed laser; as well as A processor changes the target temperature of the laser gas according to either the number of pulses of the pulsed laser or the elapsed time during which the pulsed laser is output.

2. The gas laser device according to claim 1, wherein The processor slightly changes the target temperature according to the number of pulses or the elapsed time, and changes the target temperature by using a period from the lower limit temperature of the target temperature to the lower limit temperature after passing the upper limit temperature.

3. The gas laser device according to claim 2, wherein: When the target temperature is slightly changed, the amount of change is 0.5°C to 1°C.

4. The gas laser device according to claim 2, wherein: The lower limit temperature and the upper limit temperature are set so that the peak intensity relative to the average intensity within the average beam profile of the pulsed laser at each temperature of the target temperature changed within the range of the lower limit temperature to the upper limit temperature is suppressed to below 70% based on the peak intensity relative to the average intensity within the beam profile of the pulsed laser obtained when the target temperature is fixed at a specific temperature.

5. The gas laser device according to claim 2, wherein: When the period is expressed by the number of pulses, it is 350 Mpls to 3500 Mpls.

6. The gas laser device according to claim 2, wherein: When the cycle is expressed using the elapsed time, it is 2100 minutes to 21000 minutes.

7. The gas laser device according to claim 2, wherein: The lower limit temperature is 65°C, and the upper limit temperature is 100°C.

8. The gas laser device according to claim 2, wherein: The processor changes the target temperature when the number of pulses increases by 5 Mpls to 50 Mpls.

9. The gas laser device according to claim 2, wherein: The processor changes the target temperature when the elapsed time increases by 30 minutes to 300 minutes.

10. The gas laser device according to claim 1, wherein The optical element is configured in any one of the window of the laser cavity, the output coupling mirror and the prism of the narrowband module.

11. The gas laser device according to claim 1, wherein The processor changes the target temperature every certain number of pulses or every certain elapsed time.

12. The gas laser device according to claim 1, wherein The processor sets a lower limit temperature and an upper limit temperature of the target temperature, The processor changes the target temperature in a plurality of stages within a range from the lower limit temperature to the upper limit temperature according to either the number of pulses or the elapsed time.

13. The gas laser device according to claim 1, wherein The gas laser device further comprises: a temperature sensor for measuring the temperature of the laser gas; a heat exchanger disposed in the laser cavity; a cooler that cools the refrigerant; a pipe that circulates the refrigerant between the heat exchanger and the cooler; and a valve disposed on the pipe, The processor controls the valve based on the measurement result of the temperature sensor, thereby adjusting the flow rate of the refrigerant so that the laser gas approaches the target temperature.

14. The gas laser device according to claim 1, wherein The gas laser device is a dual-cavity type having a laser oscillator and a laser amplifier, wherein the laser amplifier amplifies the seed light output from the laser oscillator. The change in the target temperature of the laser gas is applied to at least one of a laser oscillator and the laser amplifier.

15. A method for controlling the temperature of laser gas in a gas laser device that outputs pulsed laser light, wherein: The gas laser device comprises: a laser cavity containing the laser gas; a discharge electrode, which is disposed in the laser cavity and excites the laser gas to discharge; an optical element disposed on an optical path of the pulsed laser; as well as processor, The laser gas temperature control method includes the following step: the processor changes the target temperature of the laser gas according to either the number of pulses of the pulsed laser or the elapsed time during which the pulsed laser is output.

16. The laser gas temperature control method according to claim 15, wherein: The processor slightly changes the target temperature according to the number of pulses or the elapsed time, and periodically changes the target temperature using a period from the lower limit temperature of the target temperature to the lower limit temperature after passing the upper limit temperature.

17. The laser gas temperature control method according to claim 16, wherein: When the target temperature is slightly changed, the amount of change is 0.5°C to 1°C.

18. The laser gas temperature control method according to claim 16, wherein: The temperature control method of the laser gas includes the following steps: setting the lower limit temperature and the upper limit temperature so that the peak intensity relative to the average intensity in the average beam profile of the pulsed laser at each temperature of the target temperature changed within the range of the lower limit temperature to the upper limit temperature is suppressed to less than 70% based on the peak intensity relative to the average intensity in the beam profile of the pulsed laser obtained when the target temperature is fixed at a specific temperature.

19. A method for manufacturing an electronic device, comprising the following steps: Laser is generated by a gas laser device, Outputting the laser to an exposure device, The laser is exposed on a photosensitive substrate in the exposure device to manufacture an electronic device. The gas laser device comprises: a laser cavity containing laser gas; a discharge electrode, which is disposed in the laser cavity and excites the laser gas to discharge; an optical element disposed on an optical path of the pulsed laser; and A processor changes the target temperature of the laser gas according to either the number of pulses of the pulsed laser output by the discharge excitation or an elapsed time during which the pulsed laser is output.

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