Laser apparatus, method for controlling laser apparatus, and method for manufacturing electronic device

Abstract

The laser device includes: a laser cavity; a pair of discharge electrodes disposed in the laser chamber; a fan that is disposed in the laser chamber and that causes the laser gas in the laser chamber to flow between the pair of discharge electrodes; a rotation detector that detects rotation of the fan; an adjuster that adjusts laser characteristics of the pulse laser light generated in the laser cavity; and a processor that corrects the control value of the adjuster on the basis of the repetition frequency of the pulsed laser light and the detection signal of the rotation detector, and controls the adjuster using the corrected control value.

Description

Technical Field

[0001] The present disclosure relates to a laser device, a method for controlling the laser device, 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 lasers 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 where chromatic aberration is invisible. Therefore, in order to narrow the spectral line width, a narrowing module (Line Narrowing Module: LNM) containing narrowing elements (etalon, grating, etc.) is sometimes included in the laser resonator of the gas laser device. A gas laser device with a narrowed spectral line width is called a narrowed gas laser device.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-114689

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-218432 Summary of the Invention

[0008] A laser device according to one aspect of the present disclosure comprises: a laser cavity; a pair of discharge electrodes disposed in the laser cavity; a fan disposed in the laser cavity for causing laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector for detecting the rotation of the fan; an adjuster for adjusting the laser characteristics of a pulsed laser generated in the laser cavity; and a processor for correcting a control value of the adjuster based on a repetition frequency of the pulsed laser and a detection signal from the rotation detector, and controlling the adjuster using the corrected control value.

[0009] In a control method for a laser device according to one aspect of the present disclosure, the laser device comprises: a laser cavity; a pair of discharge electrodes, which are arranged in the laser cavity; a fan, which is arranged in the laser cavity and causes laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector, which detects the rotation of the fan; and an adjuster, which adjusts the laser characteristics of a pulsed laser generated in the laser cavity. The control method includes the following steps: in the laser device, a control value of the adjuster is corrected according to the repetition frequency of the pulsed laser and the detection signal of the rotation detector, and the adjuster is controlled using the corrected control value.

[0010] A method for manufacturing an electronic device according to one aspect of the present disclosure includes the following steps: generating a pulsed laser by a laser device, outputting the pulsed laser to an exposure device, and exposing the pulsed laser on a photosensitive substrate in the exposure device to manufacture the electronic device, wherein the laser device comprises: a laser cavity; a pair of discharge electrodes, which are arranged in the laser cavity; a fan, which is arranged in the laser cavity and causes the laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector, which detects the rotation of the fan; an adjuster, which adjusts the laser characteristics of the pulsed laser generated in the laser cavity; and a processor, which corrects the control value of the adjuster according to the repetition frequency of the pulsed laser and the detection signal of the rotation detector, and controls the adjuster using the corrected control value. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Several embodiments of the present disclosure are described below by way of example only with reference to the accompanying drawings.

[0012] Figure 1 The structure of a laser device according to a comparative example is schematically shown.

[0013] Figure 2 A partial structure of a laser device according to a comparative example viewed along the -V direction is schematically shown.

[0014] Figure 3 A partial structure of a laser device according to a comparative example viewed in the -Z direction is schematically shown.

[0015] Figure 4 The structure of the rotation detector is schematically shown.

[0016] Figure 5 The disc and protrusion are shown viewed along the Z direction.

[0017] Figure 6 : is a waveform diagram showing an example of a detection signal output from a rotation detector.

[0018] Figure 7 1 is a flowchart showing a procedure for controlling laser characteristics in a comparative example.

[0019] Figure 8 Graph showing time-series data of laser characteristics in a comparative example.

[0020] Figure 9 Graph showing time-series data of laser characteristics in a comparative example.

[0021] Figure 10 It shows the Figure 9 The graph shown is a result of performing a fast Fourier transform on the time series data of laser characteristics.

[0022] Figure 11 This is a diagram for explaining acoustic waves generated inside a laser cavity.

[0023] Figure 12 The structure of the laser device according to the first embodiment is schematically shown.

[0024] Figure 13 This is a graph showing the fluctuation component Bfi1(t) of the laser characteristics in the first embodiment.

[0025] Figure 14 A first example of data stored in the parameter storage device in the first embodiment is shown.

[0026] Figure 15 A second example of data stored in the parameter storage device in the first embodiment is shown.

[0027] Figure 16 This is a flowchart showing the procedure for controlling laser characteristics in the first embodiment.

[0028] Figure 17 The control value SVb1 for calculating the N+1th pulse is shown in FIG. N+1 Flowchart of the details of the processing.

[0029] Figure 18 This shows that the corrected control value SVb1 is used in the first embodiment. N+1 Generate a graph of the time series data of laser characteristics.

[0030] Figure 19 Shown are expressions and variables that are replaced when controlling pulse energy, wavelength, or line width as laser characteristics.

[0031] Figure 20 Graph showing the difference between the time series data of laser characteristics and the fluctuation component Bfi1(t).

[0032] Figure 21 It is a graph showing the fluctuation component Bfi2(t) in the second embodiment.

[0033] Figure 22A first example of data stored in the parameter storage device in the second embodiment is shown.

[0034] Figure 23 A second example of data stored in the parameter storage device in the second embodiment is shown.

[0035] Figure 24 This is a flowchart showing the procedure for controlling laser characteristics in the second embodiment.

[0036] Figure 25 The control value SVb2 for the N+1th pulse is calculated. N+1 Flowchart of the details of the processing.

[0037] Figure 26 This is a diagram showing the use of the corrected control value SVb2 in the second embodiment. N+1 Generate a graph of the time series data of laser characteristics.

[0038] Figure 27 Shown are expressions and variables that are replaced when controlling pulse energy, wavelength, or line width as laser characteristics.

[0039] Figure 28 The structure of an exposure device connected to a laser device is schematically shown. DETAILED DESCRIPTION

[0040] <Content>

[0041] 1. Comparative Example

[0042] 1.1 Structure of Laser Device 1

[0043] 1.2 Action

[0044] 1.3 Control of laser characteristic B

[0045] 1.4 Issues of the Comparative Example

[0046] 2. Speculation on the causes of the changes

[0047] 2.1 Relationship with rotation frequency fk

[0048] 2.2 Relationship with blade frequency fa

[0049] 3. Feedforward control based on repetition frequency f and detection signal SIG

[0050] 3.1 Structure

[0051] 3.2 Calculation of the variable component Bfi1(t)

[0052] 3.3 Control of laser characteristic B

[0053] 3.4 Function

[0054] 4. Modification of the First Embodiment

[0055] 4.1 First Modification

[0056] 4.2 Second Modification

[0057] 4.3 Third Modification

[0058] 4.4 Fourth Variation

[0059] 4.5 Effect of the fourth variant

[0060] 5. Feedforward control of blade frequency fa is used

[0061] 5.1 Calculation of the variable component Bfi2(t)

[0062] 5.2 Control of Laser Characteristic B

[0063] 5.3 Function

[0064] 6. Modification of the Second Embodiment

[0065] 6.1 First Modification

[0066] 6.2 Second Modification

[0067] 6.3 Third Modification

[0068] 6.4 Fourth Variation

[0069] 7. Others

[0070] 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.

[0071] 1. Comparative Example

[0072] 1.1 Structure of Laser Device 1

[0073] Figure 1 The structure of a comparative example laser device 1 is schematically shown. The comparative examples disclosed herein are methods known only to the applicant and are not publicly known examples acknowledged by the applicant. Laser device 1 is a discharge-excitation gas laser device capable of outputting pulsed laser light to exposure device 100. Exposure device 100 includes an exposure control processor 110.

[0074] Laser device 1 includes a laser cavity 10, a pair of discharge electrodes 11a and 11b, a power supply 13, a narrowband module 14, a spectrum adjuster 15, a monitor module 17, and a laser control processor 30. Narrowband module 14 and spectrum adjuster 15 constitute an optical resonator. Laser cavity 10 is positioned on the optical path of the optical resonator. Laser control processor 30 is a processing device comprising a memory 38 storing a control program and a CPU (central processing unit) 39 for executing the control program. Laser control processor 30 is specifically configured or programmed to perform the various processes included in this disclosure. Laser control processor 30 corresponds to the processor in this disclosure.

[0075] The traveling direction of the pulse laser output from the spectrum adjuster 15 is defined as the Z direction. The discharge direction between the discharge electrodes 11a and 11b is defined as the V direction or the -V direction. The Z direction and the V direction are perpendicular to each other, and the direction perpendicular to both directions is defined as the H direction or the -H direction. Figure 1 , the structure of the laser device 1 viewed along the -H direction is shown.

[0076] Figure 2 FIG. 2 shows a partial structure of a laser device 1 according to a comparative example viewed along the -V direction. Figure 3 A partial structure of the laser device 1 according to the comparative example as viewed in the -Z direction is shown.

[0077] The laser cavity 10 houses discharge electrodes 11a and 11b, a cross-flow fan 21, and a heat exchanger 23. Figure 2 , only the discharge electrode 11a is shown as the internal structure of the laser cavity 10. The laser cavity 10 is provided with windows 10a and 10b at both ends.

[0078] Laser gas containing, for example, argon or krypton as a rare gas, fluorine as a halogen gas, and neon as a buffer gas is enclosed in the laser cavity 10. Alternatively, a laser gas containing fluorine and a buffer gas may be enclosed.

[0079] An opening is formed in a portion of the laser cavity 10, and this opening is blocked by an electrical insulating portion 29. The electrical insulating portion 29 supports the discharge electrode 11a. Multiple conductive portions 29a are embedded in the electrical insulating portion 29. Each conductive portion 29a is electrically connected to the discharge electrode 11a. The power supply 13 includes a charger (not shown) and is connected to the discharge electrode 11a via the conductive portions 29a.

[0080] A return plate 10c is disposed inside the laser cavity 10. The discharge electrode 11b is supported by the return plate 10c. The discharge electrode 11b is electrically connected to the ground potential via the return plate 10c and the conductive component of the laser cavity 10. Figure 3 As shown, the return plate 10c is Figure 1 There are gaps on the deep side and the near side of the paper for the laser gas to pass through.

[0081] The crossflow fan 21 includes multiple blades 21b arranged around a rotation axis Ax. One end of the rotation axis Ax is supported by a bearing 10e and connected to a rotation detector 21a located outside the laser cavity 10. The other end of the rotation axis Ax is supported by a bearing 10f and connected to a motor 22 located outside the laser cavity 10. The crossflow fan 21 corresponds to the fan in this disclosure.

[0082] Figure 4 The structure of the rotation detector 21a is schematically shown. The rotation detector 21a is located inside a housing fixed to the bearing 10e and includes a disk 21c supported by one end of the rotation axis Ax and an eddy current sensor 21e fixed to the bearing 10e via the housing. The disk 21c is made of metal and includes a protrusion 21d.

[0083] Figure 5 The disk 21c and protrusion 21d are shown as viewed in the Z direction. The disk 21c and protrusion 21d rotate together with the rotation axis Ax. The eddy current sensor 21e generates a first pulsed magnetic field. When the protrusion 21d passes near the eddy current sensor 21e, eddy currents are generated within the protrusion 21d based on the first pulsed magnetic field. The eddy current sensor 21e detects the second pulsed magnetic field generated by the eddy currents and outputs a detection signal SIG. A capacitive sensor may also be used in place of the eddy current sensor 21e.

[0084] Figure 6 The waveform diagram shows an example of the detection signal SIG output from the rotation detector 21a. Each time the rotation axis Ax rotates once, a single pulse of the detection signal SIG is output. The repetition frequency of the detection signal SIG matches the rotation frequency fk of the crossflow fan 21, and the period of the detection signal SIG is 1 / fk. The detection signal SIG is transmitted to the laser control processor 30.

[0085] Refer again Figure 1 and Figure 2 The narrowband module 14 includes a plurality of prisms 14a and 14b and a grating 14c. The prisms 14a and 14b are sequentially arranged on the optical path of the light emitted from the window 10a. The surfaces of the prisms 14a and 14b for light input and output are parallel to the V direction. The prism 14b is supported by a rotating stage 14d. The rotating stage 14d includes a driver (not shown). The grating 14c is arranged on the optical path of the light after passing through the prisms 14a and 14b. The grooves of the grating 14c are parallel to the V direction.

[0086] The spectrum adjuster 15 includes a cylindrical plano-concave lens 15a and a cylindrical plano-convex lens 15b. The cylindrical plano-concave lens 15a is positioned between the laser cavity 10 and the cylindrical plano-convex lens 15b. The convex surface of the cylindrical plano-convex lens 15b and the concave surface of the cylindrical plano-concave lens 15a face each other, each having a focal axis parallel to the V direction. The flat surface of the cylindrical plano-convex lens 15b opposite the convex surface is coated with a partially reflective film. The cylindrical plano-concave lens 15a is supported by a linear stage 15d. The linear stage 15d includes a drive (not shown).

[0087] Monitor module 17 includes beam splitters 17a and 17b, an energy sensor 17c, and a beam monitor 17d. Beam splitter 17a is located on the optical path of the pulsed laser output from spectrum adjuster 15. Beam splitter 17a is configured to transmit a portion of the pulsed laser light toward exposure device 100 with high transmittance and reflect the remaining portion. Beam splitter 17b is located on the optical path of the pulsed laser light after being reflected by beam splitter 17a. Energy sensor 17c is located on the optical path of the pulsed laser light after being reflected by beam splitter 17b. Beam monitor 17d is located on the optical path of the pulsed laser light after being transmitted through beam splitter 17b and includes an etalon spectrometer (not shown). Monitor module 17 corresponds to the laser detector in the present disclosure.

[0088] 1.2 Action

[0089] The laser control processor 30 receives setting data of target values ​​Et, λt, and Δλt of the pulse energy E, wavelength λ, and line width Δλ, respectively, and a light emission trigger signal from the exposure control processor 110 .

[0090] The laser control processor 30 sends charging voltage setting data to the charger included in the power supply device 13 based on the setting data of the target value Et of the pulse energy E. In addition, the laser control processor 30 sends a trigger signal to the power supply device 13 based on the emission trigger signal.

[0091] When receiving a trigger signal from the laser control processor 30 , the power supply device 13 generates a pulsed high voltage using the electric energy charged by the charger, and applies the pulsed high voltage between the discharge electrodes 11 a and 11 b .

[0092] When a high voltage is applied between discharge electrodes 11a and 11b, a discharge occurs between them. The energy from this discharge excites the laser medium within laser cavity 10, causing it to transition to a higher energy level. The excited laser medium then transitions to a lower energy level, emitting light of a wavelength corresponding to the energy level difference.

[0093] Light generated in laser cavity 10 is emitted outside laser cavity 10 through windows 10a and 10b. The beam width of light emitted from window 10a of laser cavity 10 is expanded in the H direction by prisms 14a and 14b, and then enters grating 14c.

[0094] Light incident on grating 14c is reflected by its multiple grooves and diffracted in a direction corresponding to the light's wavelength. By aligning the incident angle of the light incident on grating 14c with the diffraction angle of diffracted light of a desired wavelength, the wavelength of the diffracted light incident from grating 14c on prism 14b is selected. Prisms 14b and 14a narrow the H-direction beam width of the diffracted light incident from grating 14c and return this light to laser cavity 10 through window 10a.

[0095] The cylindrical plano-convex lens 15 b included in the spectrum adjuster 15 transmits a portion of the light emitted from the window 10 b of the laser cavity 10 and outputs the light, and reflects the other portion and returns it to the laser cavity 10 .

[0096] In this manner, light emitted from the laser cavity 10 travels back and forth between the band-narrowing module 14 and the spectrum adjuster 15, being amplified each time it passes through the discharge space between the discharge electrodes 11a and 11b. This light is narrowed each time it returns to the band-narrowing module 14. The narrowed light thus oscillated is output from the spectrum adjuster 15 as pulsed laser light.

[0097] Based on the set data for the target value λt of wavelength λ, laser control processor 30 sends a control signal for the rotation angle of prism 14b to rotation stage 14d included in narrowband module 14. Rotation stage 14d rotates prism 14b about an axis parallel to the V direction in accordance with the control signal. Rotation of prism 14b adjusts the selected wavelength of narrowband module 14 and the wavelength λ of the pulsed laser light. The wavelength λ of the pulsed laser light is, for example, the center wavelength.

[0098] Based on the set data for the target value Δλt for the spectral linewidth Δλ, the laser control processor 30 sends a control signal to the linear stage 15d included in the spectrum adjuster 15 to control the position of the cylindrical plano-concave lens 15a. In response to the control signal, the linear stage 15d moves the cylindrical plano-concave lens 15a along the optical path between the laser cavity 10 and the cylindrical plano-convex lens 15b. This changes the wavefront of the light traveling from the spectrum adjuster 15 toward the narrowband module 14. This change in wavefront adjusts the spectral waveform and linewidth Δλ of the pulsed laser light.

[0099] The energy sensor 17c detects the pulse energy E of the pulse laser and outputs the data of the pulse energy E to the laser control processor 30. The data of the pulse energy E is used by the laser control processor 30 to perform feedback control on the setting data of the charging voltage sent to the power supply device 13.

[0100] The etalon spectrometer included in beam monitor 17d obtains the waveform of the interference fringes of the pulsed laser light and outputs the interference fringes waveform data to laser control processor 30. Laser control processor 30 calculates the wavelength λ of the pulsed laser light based on the position of the interference fringes and calculates the spectral linewidth Δλ of the pulsed laser light based on a portion of the interference fringes corresponding to the free spectrum range. The calculated wavelength λ is used by laser control processor 30 to feedback control the rotation angle of prism 14b, and the calculated spectral linewidth Δλ is used by laser control processor 30 to feedback control the position of cylindrical plano-concave lens 15a.

[0101] The laser control processor 30 sends a control signal to the motor 22 to rotate the cross flow fan 21. When the motor 22 rotates the cross flow fan 21, as shown in FIG. Figure 3 As indicated by arrow A, laser gas flows and circulates within laser cavity 10. Discharge products generated by the discharge between discharge electrodes 11a and 11b are removed from the discharge space by the flow of laser gas before the next discharge. This reduces the number of discharge products in the discharge space and its vicinity, resulting in stable discharge. Rotation detector 21a detects the rotation of crossflow fan 21 and outputs this information to laser control processor 30. Heat exchanger 23 dissipates the heat energy of the laser gas, heated by the discharge, to the exterior of laser cavity 10.

[0102] 1.3 Control of laser characteristic B

[0103] Figure 7 : is a flowchart showing the control procedure of laser characteristic B in a comparative example. Laser characteristic B is, for example, any one of pulse energy E, wavelength λ, and line width Δλ. The laser control processor 30 performs feedback control on laser characteristic B by performing the following processing.

[0104] In S20 , the laser control processor 30 sets the pulse number N of the pulse laser to 1 .

[0105] In S30, the laser control processor 30 sets the control value SVb of the Nth pulse to N Set to the initial value. If the laser characteristic B is the pulse energy E, the control value SVb is the charging voltage set in the power supply device 13. If the laser characteristic B is the wavelength λ, the control value SVb is the attitude angle of the prism 14b rotated by the rotating stage 14d. If the laser characteristic B is the spectral line width Δλ, the control value SVb is the position of the cylindrical plano-concave lens 15a moved by the linear stage 15d. When the Nth pulse number is determined, the control value SVb is N The initial value is a value determined in advance corresponding to the target value Bt of the laser characteristic B, for example.

[0106] In S40 , the laser control processor 30 sends a trigger signal to the power supply device 13 to perform laser oscillation and output a pulsed laser of one pulse.

[0107] In S60, the laser control processor 30 measures the laser characteristic Bn of the Nth pulse. N .

[0108] In S70, the laser control processor 30 calculates the control value SVb of the N+1th pulse using the following equation 1: N+1 .

[0109] SVb N+1 =-Gb×(Bn N -Bt)×Kb+SVb N … (Equation 1)

[0110] Here, Gb is the control gain, Bt is the target value of the laser characteristic B, and Kb is a proportional constant representing the ratio of the change in the control value SVb to the change in the laser characteristic B. N The difference between the target value Bt and the control value SVb of the N+1th pulse is calculated. N+1 , thus performing feedback control so that the laser characteristic Bn of the N+1th pulse N+1 Close to the target value Bt. The control value SVb obtained in the comparative example N+1 The Nth pulse corresponds to the first pulse in the present disclosure, and the N+1th pulse corresponds to the second pulse in the present disclosure.

[0111] In S80, the laser control processor 30 sets the control value SVb of the N+1th pulse to N+1 The calculated value is set and sent to the corresponding adjuster. If laser characteristic B is pulse energy E, the adjuster is power supply 13. If laser characteristic B is wavelength λ, the adjuster is rotary stage 14d. If laser characteristic B is line width Δλ, the adjuster is linear stage 15d.

[0112] In S90 , the laser control processor 30 adds 1 to the pulse number N of the pulse laser light to update the value of N.

[0113] In S100, the laser control processor 30 determines whether to terminate control of laser characteristic B. For example, if the output of pulsed laser light at a fixed repetition frequency f is stopped, control of laser characteristic B is terminated. If control of laser characteristic B is terminated (S100: Yes), the laser control processor 30 terminates the processing of this flowchart. If control of laser characteristic B is not terminated (S100: No), the laser control processor 30 returns the processing to S40.

[0114] 1.4 Issues of the Comparative Example

[0115] Figure 8 and Figure 9 Graph showing time series data of laser characteristic B in a comparative example. As laser characteristic B, pulse energy E is controlled. Time series data is obtained from monitor module 17. Figure 8 In the example, the repetition frequency f of the pulsed laser is 6000 Hz. Figure 9 In , the repetition frequency f is 1000Hz. Figure 8 and Figure 9 The target value Et of the pulse energy E is 10.0 mJ. Figure 7 The process shown performs feedback control on the pulse energy E, as Figure 8 and Figure 9 As shown in FIG, the pulse energy E sometimes changes and deviates from the target value Et. Figure 8 and Figure 9 Comparison shows that the variation of pulse energy E sometimes varies depending on the repetition frequency f. Figure 9 As shown, the pulse energy E may fluctuate periodically. When the pulse energy E fluctuates, exposure performance in the exposure apparatus 100 may vary, and the quality of the semiconductor device may become unstable.

[0116] Several embodiments described below relate to further stabilizing laser characteristics B such as pulse energy E and bringing them closer to a target value Bt.

[0117] 2. Speculation on the causes of the changes

[0118] Figure 10 It shows the Figure 9 The graph of the result of fast Fourier transform of the time series data of laser characteristic B shown in FIG. Figure 10 It can be seen that Figure 9 The time series data of the laser characteristic B shown contains two relatively large frequency components of 66 Hz and 88 Hz.

[0119] 2.1 Relationship with rotation frequency fk

[0120] Figure 10The first frequency component shown, 66 Hz, is roughly consistent with the rotation frequency fk of the cross-flow fan 21. When vibrations are generated in the laser device 1 due to the rotation of the cross-flow fan 21, the vibrations are transmitted to the various optical elements included in the laser device 1, and the alignment of the optical elements may change synchronously with the vibrations. Therefore, it is speculated that the 66 Hz frequency component included in the change of the laser characteristic B is caused by the vibrations generated in the laser device 1 in synchronization with the rotation of the cross-flow fan 21. In addition, as the laser characteristic B, not only the pulse energy E, but also, for example, the wavelength λ may vary due to changes in the alignment of the prisms 14a and 14b, and the spectral line width Δλ may also vary due to changes in the alignment of the cylindrical plano-concave lens 15a.

[0121] In the first embodiment, the laser characteristic B is feedforward controlled not only by the repetition frequency f but also by the detection signal SIG indicating the rotation of the cross flow fan 21. In the first embodiment, the laser characteristic B is feedforward controlled using the rotation frequency fk.

[0122] 2.2 Relationship with blade frequency fa

[0123] The product of the rotational frequency fk of the crossflow fan 21 and the number of blades 21b is defined as the blade frequency fa. In the comparative example, the rotational frequency fk is 66 Hz and the number of blades 21b is 44. In this case, the blade frequency fa is 2904 Hz, and the observation frequency is calculated to be 96 Hz. This observation frequency is the frequency obtained by sampling the 2904 Hz frequency component at 1000 Hz, which is the repetition frequency f of the pulsed laser. Figure 10 The second frequency component shown, 88 Hz, does not completely coincide with 96 Hz, but is considered to correspond to the observed frequency of the blade frequency fa when quantization error is taken into account.

[0124] Figure 11 1 is a diagram for explaining acoustic waves W1 and W2 generated inside the laser cavity 10 . Figure 11 Equivalent to Figure 3 Arrows A indicating gas flow are omitted in the diagram; instead, acoustic waves W1 and W2 are shown. A discharge with a repetition frequency f occurs in the discharge space between discharge electrodes 11a and 11b. Synchronously with this discharge, the gas within the discharge space is excited and heated, generating a compression wave. The compression wave generated in the discharge space propagates through the space within the laser cavity 10. This compression wave is sometimes referred to as acoustic wave W1. Acoustic wave W1 comes into contact with components within the laser cavity 10 and is reflected.

[0125] When sound wave W1 contacts blades 21b of crossflow fan 21, the sound wave W2 reflected by blades 21b may be affected by the blade frequency fa. When sound wave W2 reaches the discharge space, the density of the laser gas in the discharge space changes, potentially causing fluctuations in pulse energy E. Therefore, the 88 Hz frequency component, which is presumed to be caused by the sound wave W2 reflected by blades 21b, is responsible for the fluctuations in laser characteristic B. Furthermore, changes in the density of the laser gas in the discharge space also alter the refractive index distribution of the discharge space. Therefore, laser characteristic B may fluctuate not only in terms of pulse energy E but also in terms of wavelength λ and linewidth Δλ.

[0126] In the second embodiment, the laser characteristic B is feedforward controlled using the blade frequency fa.

[0127] 3. Feedforward control based on repetition frequency f and detection signal SIG

[0128] 3.1 Structure

[0129] Figure 12 The structure of the laser device 1a of the first embodiment is schematically shown. The laser device 1a includes a parameter storage device 37a. The parameter storage device 37a is configured to be accessible by the laser control processor 30 and stores reference parameters. Figures 13 to 15 The parameter storage device 37 a may also be included in the internal memory 38 of the laser control processor 30 .

[0130] 3.2 Calculation of the variable component Bfi1(t)

[0131] Figure 13 This is a graph showing the fluctuation component Bfi1(t) of the laser characteristic B in the first embodiment. Figure 13 Revealed again Figure 9 The laser characteristic B is shown in time series data, and the detection signal SIG indicating the rotation of the cross flow fan 21 and the variable component Bfi1(t) calculated in the first embodiment are shown. The detection signal SIG is output from the rotation detector 21a with a period of 1 / fk (see Figure 6 ).

[0132] The variable component Bfi1(t) is a periodic function having a period of 1 / fk, which is the same as the period of the detection signal SIG. The periodic function is, for example, a sine function. The variable component Bfi1(t) is equivalent to the first periodic function in the present disclosure, and 1 / fk is equivalent to the first period in the present disclosure. The variable component Bfi1(t) is obtained by fitting a sine curve of a period of 1 / fk to the time series data of the laser characteristic B. The initial phase of the sine curve is given by the phase offset Δkb1 of the sine curve relative to the detection signal SIG. As shown in FIG. Figure 10As described above, when the result of Fourier analysis of time series data is obtained, the amplitude Akb1 of the sinusoidal curve can also be obtained from the intensity corresponding to the rotation frequency fk of the cross flow fan 21. Akb1 corresponds to the first amplitude in the present disclosure.

[0133] If the period 1 / fk, the phase shift Δkb1, and the amplitude Akb1 are determined as described above, the variation component Bfi1(t) is given by the following equation.

[0134] Bfi1(t)=Akb1×sin(2×π×fk×t-Δkb1)

[0135] Figure 13 The variable component Bfi1(t) obtained by fitting the time series data is shown. However, the position on the horizontal axis where the variable component Bfi1(t) is 0 coincides with the position of 10 mJ, the target value Et of the pulse energy E. The variable component Bfi1(t) fluctuates in synchronization with the rotation of the crossflow fan 21.

[0136] In the first embodiment, the control value SVb of the N+1th pulse obtained in the comparative example is adjusted by feedforward control using the fluctuation component Bfi1(t). N+1 (Refer to Figure 7 ) is corrected, thereby calculating the corrected control value SVb1 N+1 This makes it possible to perform control such that the fluctuation of the laser characteristic B is offset and the deviation from the target value Bt is suppressed.

[0137] Figure 14 A first example of data stored in the parameter storage device 37a in the first embodiment is shown. Figure 8 and Figure 9 As explained, if the repetition frequency f of the pulsed laser is different, the laser characteristics B may be different. Therefore, a different variable component Bfi1(t) is used for each repetition frequency f of the pulsed laser. Therefore, the parameter storage device 37a stores data containing the correspondence between the repetition frequency f and parameters, and the parameters include the amplitude Akb1, the rotation frequency fk, and the phase offset Δkb1. By searching the parameter storage device 37a using the repetition frequency f, the corresponding parameters can be obtained. However, the rotation frequency fk of the cross flow fan 21 can also be independent of the repetition frequency f and can be the same value fk1. In addition, the phase offset Δkb1 can also be independent of the repetition frequency f and can be the same value.

[0138] Figure 15A second example of data stored in the parameter storage device 37a in the first embodiment is shown. For example, the rotation frequency fk of the cross flow fan 21 can be changed for the purpose of reducing power consumption, and different variable components Bfi1(t) are used according to changes in the rotation frequency fk. Therefore, in the parameter storage device 37a, data including the correspondence between a combination of the repetition frequency f and the rotation frequency fk and a parameter including the amplitude Akb1 and the phase offset Δkb1 can also be stored. By searching the parameter storage device 37a using the repetition frequency f and the rotation frequency fk, the corresponding parameters can be obtained. In the second example, the rotation frequency fk is also one of the parameters. The rotation frequency fk is set, for example, in a range of 30 Hz to 95 Hz, preferably 63 Hz, 66 Hz or 75 Hz.

[0139] 3.3 Control of laser characteristic B

[0140] Figure 16 This is a flowchart showing the control procedure of the laser characteristic B in the first embodiment. The laser control processor 30 performs the following processing in the feedback control in the comparative example (see Figure 7 ), feedforward control based on the repetition frequency f and the detection signal SIG is performed.

[0141] In S10a, the laser control processor 30 starts the timer when receiving the detection signal SIG. In S50a described later, the time t is read from the timer. N , calculate the time t in S71a N+1 , thereby performing control based on the timing of the detection signal SIG. While this flowchart illustrates a case where the timer started in S10a is not reset midway and continues counting, the present disclosure is not limited to this. Alternatively, the timer may be reset and started each time the detection signal SIG is received.

[0142] The treatments of S20, S30a and S40 were compared with those of reference Figure 7 S20, S30 and S40 are substantially the same as those described above. In addition, in S30a, the control value SVb is set to be the same as that in the comparative example. N To distinguish, the reference symbol of the control value is set to SVb1 N .

[0143] In S50a, the laser control processor 30 reads the time t of the oscillation Nth pulse from the timer. N Time t N This corresponds to the first moment in this disclosure.

[0144] S60 processing and reference Figure 7 The instructions are handled the same way.

[0145] In S70a, the laser control processor 30 replaces the reference Figure 7 The control value SVb of the N+1th pulse is shown as follows: N+1 The control value SVb1 of the N+1th pulse is calculated as follows N+1 .

[0146] Figure 17 The control value SVb1 for calculating the N+1th pulse is shown in FIG. N+1 Flowchart of the details of the processing. Figure 17 The processing shown is equivalent to Figure 16 The S70a subroutine.

[0147] In S71a, the laser control processor 30 calculates the time t of oscillating the N+1th pulse. N+1 Time t N+1 By oscillating the time t of the Nth pulse N Add the reciprocal of the repetition frequency f, 1 / f, to calculate. N+1 This corresponds to the second moment in this disclosure.

[0148] In S72a, the laser control processor 30 obtains the parameters of the variable component Bfi1(t) based on the repetition frequency f. The parameters of the variable component Bfi1(t) include the amplitude Akb1, the rotation frequency fk, and the phase offset Δkb1 stored in the parameter storage device 37a.

[0149] In S73a, the laser control processor 30 calculates the control value SVb1 of the N+1th pulse using the following equation 2: N+1 .

[0150] SVb1 N+1 =-[Gb×(Bn N -Bt)+gb1×{Bfi1(t N+1 )-Bfi1(t N )}]×Kb+SVb1 N …(Equation 2)

[0151] Here, gb1 is the control gain.

[0152] Formula 2 corresponds to subtracting gb1×{Bfi1(t N+1 )-Bfi1(t N )}×Kb. In the comparative example, according to the laser characteristic Bn of the Nth pulse N The difference between the target value Bt and the control value SVb of the N+1th pulse is calculated. N+1 , therefore, in the control value SVb N+1 The time t of the Nth pulse has been addedN The first value of the corresponding variable component Bfi1(t N ). Therefore, in the first embodiment, the time t of the N+1th pulse is used. N+1 The second value of the corresponding variable component Bfi1(t N+1 ) and the time t of the Nth pulse N The first value of the corresponding variable component Bfi1(t N ) difference, the control value SVb in the comparative example N+1 Make corrections.

[0153] After S73a, the laser control processor 30 ends the processing of this flowchart and returns to Figure 16 The processing shown.

[0154] Refer again Figure 16 The treatments of S80a, S90 and S100 were compared with those of reference Figure 7 S80, S90 and S100 are substantially the same as those described above. In addition, in S80a, the control value SVb is set to be the same as that in the comparative example. N+1 To distinguish, the reference symbol of the control value is set to SVb1 N+1 .

[0155] 3.4 Function

[0156] (1) The laser device 1a of the first embodiment includes a laser cavity 10; a pair of discharge electrodes 11a and 11b; a cross-flow fan 21; a rotation detector 21a; an adjuster such as a power supply device 13, a rotating stage 14d, and a linear stage 15d; and a laser control processor 30. The discharge electrodes 11a and 11b are arranged in the laser cavity 10. The cross-flow fan 21 is arranged in the laser cavity 10 so that the laser gas in the laser cavity 10 flows between the discharge electrodes 11a and 11b. The rotation detector 21a detects the rotation of the cross-flow fan 21. The adjuster adjusts the laser characteristic B of the pulsed laser generated in the laser cavity 10. The laser control processor 30 controls the control value SVb of the adjuster based on the repetition frequency f of the pulsed laser and the detection signal SIG of the rotation detector 21a. N+1 Correction is performed and the corrected control value SVb1 is used. N+1 Control the regulator.

[0157] Thus, the control value SVb can be N+1 Correction is performed to cancel fluctuations in the laser characteristic B affected by the repetition frequency f and the rotation of the cross-flow fan 21 , thereby enabling the laser characteristic B to be controlled with high precision.

[0158] Figure 18 This shows that the corrected control value SVb1 is used in the first embodiment. N+1This is a graph of time-series data of the generated laser characteristic B. As the laser characteristic B, the pulse energy E is controlled. Figure 18 The difference between the time series data of the laser characteristic B and the variation component Bfi1(t) in the comparative example (see Figure 20 ) is roughly consistent. The repetition frequency f of the pulse laser is 1000Hz, and the target value Et of the pulse energy E is 10.0mJ. Figure 9 Compared with the comparative example shown, the fluctuation range of the pulse energy E is reduced, and the control accuracy of the laser characteristic B is improved.

[0159] (2) According to the first embodiment, the laser control processor 30 controls the control value SVb N+1 Correction is performed to suppress the laser characteristic B from deviating from the target value Bt.

[0160] Thus, by suppressing the deviation from the target value Bt, the laser characteristic B can be stabilized.

[0161] (3) According to the first embodiment, the laser device 1a includes the monitor module 17 for measuring the laser characteristic B. The laser control processor 30 controls the control value SVb by feedforward control based on the repetition frequency f and the detection signal SIG. N+1 Correction is performed, and the control value SVb N+1 The laser characteristic Bn of the Nth pulse of the pulse laser is set to N The feedback control of the difference between the Nth pulse and the target value Bt makes the laser characteristic Bn of the N+1th pulse after the Nth pulse N+1 Close to the target value Bt.

[0162] Thus, by combining feedforward control and feedback control, the laser characteristic B can be controlled with high precision.

[0163] (4) According to the first embodiment, the laser control processor 30 calculates the variation component Bfi1(t) of the laser characteristic B that varies synchronously with the rotation of the cross flow fan 21, and uses the variation component Bfi1(t) to adjust the control value SVb. N+1 Make corrections.

[0164] Thus, by using the fluctuation component Bfi1 (t) synchronized with the rotation of the cross flow fan 21 , fluctuations in the laser characteristic B due to the rotation of the cross flow fan 21 can be suppressed.

[0165] (5) According to the first embodiment, the laser control processor 30 performs the laser oscillation of the Nth pulse according to the time t N The first value of the corresponding variable component Bfi1(t N ) and the time t of laser oscillation of the N+1th pulse N+1 The second value of the corresponding variable component Bfi1(tN+1 ) difference, the control value SVb N+1 Make corrections.

[0166] Thus, by using the variation component Bfi1 (t N ) and the variation component Bfi1(t N+1 ) is used to accurately correct the control value SVb of the feedback control based on the difference between the laser characteristic B of the Nth pulse and the target value Bt. N+1 .

[0167] (6) According to the first embodiment, the laser control processor 30 obtains the time t by measuring N , based on time t N and the calculation of the repetition frequency f to obtain the time t N+1 .

[0168] Thus, the actual time t is measured. N , using the measured time t N Calculate time t N+1 Therefore, it is possible to perform high-precision analysis based on the variable component Bfi1(t N ) and Bfi1(t N+1 ) correction of the difference.

[0169] (7) According to the first embodiment, time t N and t N+1 This is the elapsed time based on the time when the detection signal SIG is received.

[0170] Thus, by using the time when the detection signal SIG is received as a reference, correction using the fluctuation component Bfi1 (t) synchronized with the rotation of the cross flow fan 21 can be performed with high accuracy.

[0171] (8) According to the first embodiment, the laser control processor 30 uses the fluctuation component Bfi1(t) to adjust the control value SVb. N+1 Correction is performed so that the fluctuation component Bfi1(t) is a periodic function whose period is the inverse of the rotation frequency fk of the cross flow fan 21 .

[0172] By using a periodic function whose period is the inverse of the rotation frequency fk, it is possible to suppress with high accuracy the periodic variation of the laser characteristic B caused by the vibration due to the rotation of the cross flow fan 21 .

[0173] (9) According to the first embodiment, the laser device 1a includes the monitor module 17 for measuring the laser characteristic B. The laser control processor 30 obtains time series data of the laser characteristic B from the monitor module 17 and fits a sine curve to the time series data to obtain the variation component Bfi1(t).

[0174] Thus, by using the actually measured time series data, the fluctuation component Bfi1(t) can be obtained with high accuracy. The fluctuation component Bfi1(t) is obtained, for example, during adjustment after assembling the laser device 1a.

[0175] (10) According to the first embodiment, the laser control processor 30 performs Fourier analysis on the time series data, obtains the amplitude Akb1 of the sine curve from the intensity corresponding to the rotation frequency fk, and fits the sine curve having the amplitude Akb1 to the time series data.

[0176] Thus, the amplitude Akb1 of the sinusoidal curve is obtained by Fourier analysis of the time series data, and therefore the variation component Bfi1 (t) can be obtained with high accuracy.

[0177] (11) According to the first embodiment, the laser control processor 30 is configured to be able to access the data including the repetition frequency f and the data for correcting the control value SVb. N+1 The laser control processor 30 uses the parameters obtained by searching the data using the repetition frequency f to determine the control value SVb. N+1 Make corrections.

[0178] Thus, by using pre-created data, the control value SVb can be quickly obtained. N+1 Parameters.

[0179] (12) According to the first embodiment, the laser control processor 30 is configured to be able to access the repetition frequency f, the rotation frequency fk of the cross flow fan 21, and the control value SVb for correction. N+1 The laser control processor 30 uses the parameters obtained by searching the data using the repetition frequency f and the rotation frequency fk to control the control value SVb. N+1 Make corrections.

[0180] Thus, by acquiring parameters based on both the repetition frequency f and the rotation frequency fk, detailed correction can be performed.

[0181] Regarding other aspects, the first embodiment is the same as the comparative example.

[0182] 4. Modification of the First Embodiment

[0183] Figure 19 The following shows expressions and variables that are replaced when controlling the pulse energy E, wavelength λ, or line width Δλ as the laser characteristic B.

[0184] 4.1 First Modification

[0185] In the first modified example, the pulse energy E is controlled as the laser characteristic B. In this case, the fluctuation component Efi1(t) of the pulse energy E given by the following equation is used instead of the fluctuation component Bfi1(t).

[0186] Efi1(t)=Ake1×sin(2×π×fk×t-Δke1)

[0187] Here, Ake1 is the amplitude of the variation component Efi1(t).

[0188] When the pulse energy E is controlled as the laser characteristic B, the control value SVb1 of the N+1th pulse is replaced by N+1 The control value SVer1 given by the following formula is used N+1 .

[0189] SVe1 N+1 =-[Ge×(En N -Et)+ge1×{Efi1(t N+1 )-Efi1(t N )}]×Ke+SVe1 N

[0190] Here, the meanings of the variables are as follows.

[0191] Ge is the control gain of the feedback control of the pulse energy E.

[0192] ·En N is the pulse energy E of the Nth pulse.

[0193] Et is the target value of the pulse energy E.

[0194] ge1 is a control gain of the feedforward control using the pulse energy E of the rotation frequency fk.

[0195] ·Efi1(t N+1 ) and Efi1(t N ) are respectively N+1 and t N The value of the corresponding variation component Efi1(t) of the pulse energy E.

[0196] Ke is a proportionality constant indicating the ratio of the amount of change in the control value SVer1 to the amount of change in the pulse energy E.

[0197] In other respects, the first modification is the same as the first embodiment.

[0198] 4.2 Second Modification

[0199] In the second modified example, the wavelength λ is controlled as the laser characteristic B. In this case, a variable component λfi1(t) of the wavelength λ given by the following equation is used instead of the variable component Bfi1(t).

[0200] λfi1(t)=Akλ1×sin(2×π×fk×t-Δkλ1)

[0201] Here, Akλ1 is the amplitude of the fluctuation component λfi1(t).

[0202] When the wavelength λ is controlled as the laser characteristic B, the control value SVb1 of the N+1th pulse is replaced by N+1 The control value SVλ1 given by the following formula is used N+1 .

[0203] SVλ1 N+1 =-[Gλ×(λn N -λt)+gλ1×{λfi1(t N+1 )-λfi1(t N )}]×Kλ+SVλ1 N

[0204] Here, the meanings of the variables are as follows.

[0205] Gλ is the control gain of the feedback control of the wavelength λ.

[0206] ·λn N is the wavelength λ of the Nth pulse.

[0207] ·λt is the target value of wavelength λ.

[0208] gλ1 is a control gain of feedforward control using the wavelength λ of the rotation frequency fk.

[0209] ·λfi1(t N+1 ) and λfi1(t N ) are respectively N+1 and t N The value of the variation component λfi1(t) of the corresponding wavelength λ.

[0210] Kλ is a proportionality constant indicating the ratio of the amount of change in the control value SVλ1 to the amount of change in the wavelength λ.

[0211] In other respects, the second modification is the same as the first embodiment.

[0212] 4.3 Third Modification

[0213] In the third modified example, the line width Δλ is controlled as the laser characteristic B. In this case, a variation component Δλfi1(t) of the line width Δλ given by the following equation is used instead of the variation component Bfi1(t).

[0214] Δλfi1(t)=AkΔλ1×sin(2×π×fk×t-ΔkΔλ1)

[0215] Here, AkΔλ1 is the amplitude of the fluctuation component Δλfi1(t).

[0216] When the line width Δλ is controlled as the laser characteristic B, the control value SVb1 of the N+1th pulse is replaced by N+1 The control value SVΔλ1 given by the following formula is used N+1 .

[0217] SVΔλ1 N+1 =-[GΔλ×(Δλn N -Δλt)+gΔλ1×{Δλfi1(t N+1 )-Δλfi1(t N )}]×KΔλ+SVΔλ1 N

[0218] Here, the meanings of the variables are as follows.

[0219] GΔλ is the control gain of the feedback control of the spectral line width Δλ.

[0220] ·Δλn N is the linewidth Δλ of the Nth pulse.

[0221] ·Δλt is the target value of the spectral line width Δλ.

[0222] gΔλ1 is a control gain of feedforward control using the line width Δλ of the rotation frequency fk.

[0223] ·Δλfi1(t N+1 ) and Δλfi1(t N ) are respectively N+1 and t N The value of the variation component Δλfi1(t) of the corresponding spectral line width Δλ.

[0224] KΔλ is a proportionality constant representing the ratio of the amount of change in the control value SVΔλ1 to the amount of change in the spectral line width Δλ.

[0225] In other respects, the third modification is the same as the first embodiment.

[0226] 4.4 Fourth Variation

[0227] In the fourth modification, two or more of the pulse energy E, wavelength λ, and line width Δλ are controlled as the laser characteristics B. In this case, the control of each laser characteristic B is performed using Figure 19 The variables shown. The individual laser characteristics B may be controlled independently of one another. However, the repetition frequency f, the rotation frequency fk, and the detection signal SIG may be shared by different laser characteristics B. Phase offsets Δkb1, Δke1, Δkλ1, and ΔkΔλ1 may also use values ​​shared by different laser characteristics B.

[0228] 4.5 Effect of the fourth variant

[0229] (13) According to the fourth variant, the laser characteristic B includes a first characteristic as one of the pulse energy E, the wavelength λ, and the spectral line width Δλ, and a second characteristic as the other. The adjuster includes a first adjuster for adjusting the first characteristic and a second adjuster for adjusting the second characteristic. If the first characteristic is the pulse energy E, the first adjuster is the power supply device 13, and the second characteristic is the wavelength λ or the spectral line width Δλ. If the second characteristic is the wavelength λ, the second adjuster is the rotating stage 14d, and if the second characteristic is the spectral line width Δλ, the second adjuster is the linear stage 15d. The laser control processor 30 adjusts the first control value SVb of the first adjuster according to the repetition frequency f and the detection signal SIG. N+1 and the second control value SVb of the second regulator N+1 Both the first and second adjusters are calibrated and controlled.

[0230] Thus, by applying control based on the repetition frequency f and the detection signal SIG to the plurality of laser characteristics B, variations in the laser characteristics B can be effectively suppressed.

[0231] In other respects, the fourth modification is the same as the first embodiment.

[0232] 5. Feedforward control of blade frequency fa is used

[0233] Next, the second embodiment will be described. The structure of the laser device 1a in the second embodiment and the reference Figure 12 The same as the first embodiment described above.

[0234] 5.1 Calculation of the variable component Bfi2(t)

[0235] Figure 20 Graph showing the difference between the time series data of the laser characteristic B and the fluctuation component Bfi1(t). Figure 20 The pulse energy E in the comparative example is obtained by time series data (refer to Figure 9 ) minus the time t of each pulse NThe corresponding pulse energy E variable component Efi1(t N ) and obtained.

[0236] Figure 21 It is a graph showing the fluctuation component Bfi2(t) in the second embodiment. Figure 21 Enlarged view Figure 20 The inside of the encircling line XXI shows the detection signal SIG indicating the rotation of the cross flow fan 21 and the variable component Bfi2(t) calculated in the second embodiment. The detection signal SIG is output from the rotation detector 21a with a period of 1 / fk (see Figure 6 ).

[0237] The variable component Bfi2(t) is a periodic function whose period is 1 / fa, the inverse of the blade frequency fa given by the product of the rotation frequency fk of the cross-flow fan 21 and the number of blades 21b. The periodic function is, for example, a sine function. The period 1 / fa of the variable component Bfi2(t) is shorter than the period 1 / fk of the variable component Bfi1(t). The variable component Bfi2(t) is equivalent to the second periodic function in the present disclosure, and 1 / fa is equivalent to the second period in the present disclosure. The variable component Bfi2(t) is obtained by fitting a sine curve of a period 1 / fa to the difference between the timing data of the laser characteristic B and the variable component Bfi1(t). The initial phase of the sine curve is given by the phase offset Δkb2 of the sine curve relative to the detection signal SIG. As shown in FIG. Figure 10 As explained, when the results of Fourier analysis of time-series data are obtained, the amplitude Akb2 of the sinusoidal curve can also be calculated based on the intensity corresponding to the observation frequency when the frequency component of the blade frequency fa is sampled at the repetition frequency f. Akb2 corresponds to the second amplitude in this disclosure.

[0238] If the period 1 / fa, the phase shift Δkb2, and the amplitude Akb2 are determined as described above, the variation component Bfi2(t) is given by the following equation.

[0239] Bfi2(t)=Akb2×sin(2×π×fa×t-Δkb2)

[0240] Figure 21 The figure shows the variable component Bfi2(t) obtained by fitting the difference between the time series data and the variable component Bfi1(t). However, the position on the horizontal axis where the value of the variable component Bfi2(t) is 0 coincides with the target value Et of the pulse energy E, which is 10 mJ. The variable component Bfi2(t) fluctuates synchronously with the rotation of the crossflow fan 21.

[0241] In the second embodiment, the control value SVb of the N+1th pulse obtained in the comparative example is adjusted by feedforward control using the fluctuation components Bfi1(t) and Bfi2(t). N+1 (Refer to Figure 7 ) is corrected, thereby calculating the corrected control value SVb2 N+1 This makes it possible to perform control such that the fluctuation of the laser characteristic B is offset and the deviation from the target value Bt is suppressed.

[0242] Figure 22 A first example of data stored in the parameter storage device 37a in the second embodiment is shown. Figure 8 and Figure 9 As explained, if the repetition frequency f of the pulsed laser light varies, the laser characteristics B may vary. Therefore, a different variable component Bfi2(t) is used for each repetition frequency f of the pulsed laser light. Therefore, the parameter storage device 37a stores data containing the correspondence between the repetition frequency f and parameters, including the amplitude Akb2, the blade frequency fa, and the phase offset Δkb2. By searching the parameter storage device 37a using the repetition frequency f, the corresponding parameters can be obtained. However, the blade frequency fa may also be the same value fa1, independent of the repetition frequency f. Furthermore, the phase offset Δkb2 may also be the same value, independent of the repetition frequency f.

[0243] Figure 23 A second example of data stored in the parameter storage device 37a in the second embodiment is shown. It is also possible to change the rotation frequency fk of the cross flow fan 21, and use different variable components Bfi2(t) according to the accompanying changes in the blade frequency fa. Therefore, in the parameter storage device 37a, data including the correspondence between a combination of the repetition frequency f and the blade frequency fa and a parameter including the amplitude Akb2 and the phase offset Δkb2 may also be stored. By searching the parameter storage device 37a using the repetition frequency f and the blade frequency fa, the corresponding parameters can be obtained. In the second example, the blade frequency fa is also one of the parameters. The blade frequency fa is, for example, set in a range of more than 1300 Hz and less than 4200 Hz, preferably 2772 Hz, 2904 Hz or 3300 Hz.

[0244] 5.2 Control of Laser Characteristic B

[0245] Figure 24 This is a flowchart showing the control procedure of the laser characteristic B in the second embodiment. In addition to calculating the control value SVb2 of the N+1th pulse in S70b, N+1 In addition to the processing, Figure 24 The processing and reference shown Figure 16The first embodiment is substantially the same as described above. In addition, in S30b, S70b and S80b, the control value SVb1 is the same as the control value SVb1 in the first embodiment. N and SVb1 N+1 To distinguish, the reference symbol of the control value is set to SVb2 N and SVb2 N+1 .

[0246] Figure 25 The control value SVb2 for the N+1th pulse is calculated. N+1 Flowchart of the details of the processing. Figure 25 The processing shown is equivalent to Figure 24 The S70b subroutine.

[0247] Processing and reference of S71a Figure 17 The same as the first embodiment described above.

[0248] In S72b, the laser control processor 30 obtains the parameters of the variable components Bfi1(t) and Bfi2(t) according to the repetition frequency f. The parameters of the variable component Bfi1(t) include Figure 14 or Figure 15 The parameters of the variable component Bfi2(t) include the amplitude Akb1, the rotation frequency fk, and the phase shift Δkb1. Figure 22 or Figure 23 Shown are the amplitude Akb2, the blade frequency fa and the phase shift Δkb2.

[0249] In S73b, the laser control processor 30 calculates the control value SVb2 of the N+1th pulse using the following equation 3: N+1 .

[0250] SVb2 N+1 =-[Gb×(Bn N -Bt)+gb1×{Bfi1(t N+1 )-Bfi1(t N )}+gb2×{Bfi2(t N+1 )-Bfi2

[0251] (t N )}]×Kb+SVb2 N …(Equation 3)

[0252] Here, gb2 is the control gain.

[0253] Formula 3 corresponds to subtracting [gb1×{Bfi1(t N+1 )-Bfi1(t N )}+gb2×{Bfi2(t N+1 )-Bfi2(tN )}]×Kb. In the comparative example, according to the laser characteristic Bn of the Nth pulse N The difference between the target value Bt and the control value SVb of the N+1th pulse is calculated. N+1 , therefore, in the control value SVb N+1 The time t of the Nth pulse has been added N The first value of the corresponding variable component Bfi1(t N ) and Bfi2(t N ). Therefore, in the second embodiment, the time t of the N+1th pulse is used. N+1 The second value of the corresponding variable component Bfi1(t N+1 ) and the time t of the Nth pulse N The first value of the corresponding variable component Bfi1(t N ) and the time t of the N+1th pulse N+1 The second value of the corresponding variable component Bfi2(t N+1 ) and the time t of the Nth pulse N The first value of the corresponding variable component Bfi2(t N ) difference, the control value SVb in the comparative example N+1 Make corrections.

[0254] After S73b, the laser control processor 30 ends the processing of this flowchart and returns to Figure 24 The processing shown.

[0255] 5.3 Function

[0256] (14) According to the second embodiment, the cross flow fan 21 includes a plurality of blades 21b arranged around the rotation axis Ax. The laser control processor 30 uses the variation component Bfi2(t) to control the control value SVb. N+1 Correction is performed so that the fluctuation component Bfi2(t) is a periodic function whose period is the inverse of the blade frequency fa given by the product of the rotation frequency fk of the cross flow fan 21 and the number of blades 21b.

[0257] Thus, by using the product of the rotation frequency fk of the cross-flow fan 21 and the number of blades 21 b , correction can be performed that takes into account the influence of the sound waves W2 reflected by the blades 21 b .

[0258] Figure 26 This is a diagram showing the use of the corrected control value SVb2 in the second embodiment. N+1 This is a graph of time-series data of the generated laser characteristic B. As the laser characteristic B, the pulse energy E is controlled. Figure 26The difference between the time series data of the laser characteristic B and the sum of the variation components Bfi1(t) and Bfi2(t) is roughly the same as that in the comparative example. The repetition frequency f of the pulse laser is 1000 Hz, and the target value Et of the pulse energy E is 10.0 mJ. Figure 18 Compared with the first embodiment shown, the fluctuation range of the pulse energy E is reduced and stabilized near the target value Et.

[0259] Feedforward control is not limited to using both the variable components Bfi1(t) and Bfi2(t); only the variable component Bfi2(t) may be used. When only the variable component Bfi2(t) is used, the variation in the laser characteristic B of the pulsed laser is substantially consistent with the difference between the time series data of the laser characteristic B and the variable component Bfi2(t) in the comparative example.

[0260] (15) According to the second embodiment, the laser control processor 30 uses the variable component Bfi1(t) and the variable component Bfi2(t) to calculate the control value SVb. N+1 Correction is performed so that the variation component Bfi1(t) is a periodic function having a period 1 / fk and being synchronized with the rotation of the cross flow fan 21, and the variation component Bfi2(t) is a periodic function having a period 1 / fa shorter than the period 1 / fk and being synchronized with the rotation of the cross flow fan 21.

[0261] Thus, by using the variation components Bfi1(t) and Bfi2(t) having different periods, even when the variation of the laser characteristic B includes two frequency components, the control value SVb can be corrected with high accuracy. N+1 .

[0262] (16) According to the second embodiment, the cross flow fan 21 includes a plurality of blades 21b arranged around the rotation axis Ax. The laser control processor 30 uses the variable component Bfi1(t) and the variable component Bfi2(t) to calculate the control value SVb. N+1 Correction is performed, the variable component Bfi1(t) is a periodic function with the inverse of the rotation frequency fk of the cross flow fan 21 as the period, and the variable component Bfi2(t) is a periodic function with the inverse of the blade frequency fa given by the product of the rotation frequency fk and the number of blades 21b as the period.

[0263] This makes it possible to perform correction that takes into account the influence of both the vibration due to the rotation of the cross-flow fan 21 and the sound wave W2 reflected by the blades 21 b.

[0264] (17) According to the second embodiment, the laser device 1a includes a monitor module 17 for measuring the laser characteristic B. The laser control processor 30 obtains time-series data of the laser characteristic B from the monitor module 17. The laser control processor 30 fits a first sinusoidal curve to the time-series data to obtain the variation component Bfi1(t), and fits a second sinusoidal curve to the difference between the time-series data and the variation component Bfi1(t) to obtain the variation component Bfi2(t).

[0265] Thus, by using the difference between the time series data and the fluctuation component Bfi1(t), in addition to the correction amount based on the fluctuation component Bfi1(t), the fluctuation component Bfi2(t) can be obtained with high accuracy.

[0266] (18) According to the second embodiment, the laser control processor 30 performs Fourier analysis on the time series data, calculates the amplitude Akb1 of the first sinusoidal curve based on the first intensity corresponding to the rotation frequency fk, and calculates the amplitude Akb2 of the second sinusoidal curve based on the second intensity corresponding to the observation frequency, which is the frequency when the frequency component of the blade frequency fa is sampled at the repetition frequency f. The laser control processor 30 fits the first sinusoidal curve having the amplitude Akb1 to the time series data, and fits the second sinusoidal curve having the amplitude Akb2 to the difference between the time series data and the variable component Bfi1(t).

[0267] Thus, the amplitudes Akb1 and Akb2 of the sinusoidal curves are obtained by Fourier analysis of the time series data, and therefore the variation components Bfi1 (t) and Bfi2 (t) can be obtained with high accuracy.

[0268] Regarding other aspects, the second embodiment is the same as the first embodiment.

[0269] 6. Modification of the Second Embodiment

[0270] Figure 27 The following shows expressions and variables that are replaced when controlling the pulse energy E, wavelength λ, or line width Δλ as the laser characteristic B.

[0271] 6.1 First Modification

[0272] In the first modified example, the pulse energy E is controlled as the laser characteristic B. In this case, the fluctuation component Efi2(t) of the pulse energy E given by the following equation is used instead of the fluctuation component Bfi2(t).

[0273] Efi2(t)=Ake2×sin(2×π×fa×t-Δke2)

[0274] Here, Ake2 is the amplitude of the variation component Efi2(t).

[0275] When the pulse energy E is controlled as the laser characteristic B, the control value SVb2 of the N+1th pulse is replaced by N+1 The control value SVer2 given by the following formula is used N+1 .

[0276] SVe2 N+1 =-[Ge×(En N -Et)+ge1×{Efi1(t N+1 )-Efi1(t N )}+ge2×{Efi2(t N+1 )-Efi2

[0277] (t N )}]×Ke+SVe2 N

[0278] Here, the meanings of the variables are as follows.

[0279] ge2 is the control gain of the feedforward control using the pulse energy E of the blade frequency fa.

[0280] ·Efi2(t N+1 ) and Efi2(t N ) are respectively N+1 and t N The value of the corresponding variation component Efi2(t) of the pulse energy E.

[0281] In other respects, the first modification is the same as the second embodiment.

[0282] 6.2 Second Modification

[0283] In the second modified example, the wavelength λ is controlled as the laser characteristic B. In this case, a variable component λfi2(t) of the wavelength λ given by the following equation is used instead of the variable component Bfi2(t).

[0284] λfi2(t)=Akλ2×sin(2×π×fa×t-Δkλ2)

[0285] Here, Akλ2 is the amplitude of the variation component λfi2(t).

[0286] When the wavelength λ is controlled as the laser characteristic B, the control value SVb2 of the N+1th pulse is replaced by N+1 The control value SVλ2 given by the following formula is used N+1 .

[0287] SVλ2 N+1 =-[Gλ×(λn N-λt)+gλ1×{λfi1(t N+1 )-λfi1(t N )}+gλ2×{λfi2(t N+1 )-λfi2

[0288] (t N )}]×Kλ+SVλ2 N

[0289] Here, the meanings of the variables are as follows.

[0290] gλ2 is a control gain of feedforward control using the wavelength λ of the blade frequency fa.

[0291] ·λfi2(t N+1 ) and λfi2(t N ) are respectively N+1 and t N The value of the variation component λfi2(t) corresponding to the wavelength λ.

[0292] In other respects, the second modification is the same as the second embodiment.

[0293] 6.3 Third Modification

[0294] In the third modified example, the line width Δλ is controlled as the laser characteristic B. In this case, a variation component Δλfi2(t) of the line width Δλ given by the following equation is used instead of the variation component Bfi2(t).

[0295] Δλfi2(t)=AkΔλ2×sin(2×π×fa×t-ΔkΔλ2)

[0296] Here, AkΔλ2 is the amplitude of the variation component Δλfi2(t).

[0297] When the line width Δλ is controlled as the laser characteristic B, the control value SVb2 of the N+1th pulse is replaced by N+1 The control value SVΔλ2 given by the following formula is used N+1 .

[0298] SVΔλ2 N+1 =-[GΔλ×(Δλn N -Δλt)+gΔλ1×{Δλfi1(t N+1 )-Δλfi1(t N )}+gΔλ2×{Δλfi2

[0299] (t N+1 )-Δλfi2(t N )}]×KΔλ+SVΔλ2N

[0300] Here, the meanings of the variables are as follows.

[0301] gΔλ2 is a control gain of feedforward control using the line width Δλ of the blade frequency fa.

[0302] ·Δλfi2(t N+1 ) and Δλfi2(t N ) are respectively N+1 and t N The value of the variation component Δλfi2(t) of the corresponding spectral line width Δλ.

[0303] Regarding other aspects, the third modification is the same as the second embodiment.

[0304] 6.4 Fourth Variation

[0305] In the fourth modification, two or more of the pulse energy E, wavelength λ, and line width Δλ are controlled as the laser characteristics B. In this case, the control of each laser characteristic B is performed using Figure 19 and Figure 27 The variables shown. The control of each laser characteristic B may be independent of each other. However, the repetition frequency f, the rotation frequency fk, the blade frequency fa, and the detection signal SIG may be shared between different laser characteristics B. Phase offsets Δkb1, Δke1, Δkλ1, ΔkΔλ1, Δkb2, Δke2, Δkλ2, and ΔkΔλ2 may also use values ​​shared between different laser characteristics B.

[0306] Regarding other aspects, the fourth modification is the same as the second embodiment.

[0307] 7. Others

[0308] Figure 28 The structure of the exposure device 100 connected to the laser device 1 a is schematically shown. The laser device 1 a generates pulsed laser light and outputs it to the exposure device 100 .

[0309] exist Figure 28In the figure, the exposure device 100 includes an illumination optical system 40 and a projection optical system 41. The illumination optical system 40 illuminates the mask pattern of the mask (not shown) arranged on the mask stage RT by pulse laser light incident from the laser device 1a. The projection optical system 41 performs reduced projection of the pulse laser light after passing through the mask, so that it is imaged on the workpiece (not shown) arranged on the workpiece stage WT. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist. The exposure device 100 exposes the pulse laser light reflecting the mask pattern on the workpiece by synchronously moving the mask stage RT and the workpiece stage WT in parallel. After the mask pattern is transferred to the semiconductor wafer through the above exposure process, electronic devices can be manufactured through multiple processes.

[0310] 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.

[0311] 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” or “comprising” should be interpreted as “excluding the presence of structural elements other than the recorded structural elements”. Terms such as “having” should be interpreted as “not limited to the parts recorded as having”. In addition, the indefinite article “a” 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 laser device comprising: Laser cavity; a pair of discharge electrodes disposed in the laser cavity; a fan disposed in the laser cavity to cause the laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector that detects rotation of the fan; an adjuster for adjusting laser characteristics of the pulsed laser generated in the laser cavity; as well as A processor corrects a control value of the adjuster according to the repetition frequency of the pulsed laser and the detection signal of the rotation detector, and controls the adjuster using the corrected control value.

2. The laser device according to claim 1, wherein The processor corrects the control value to suppress the laser characteristic from deviating from a target value.

3. The laser device according to claim 1, wherein The laser device further includes a laser detector for measuring the laser characteristics. The processor corrects the following control value through feedforward control based on the repetition frequency and the detection signal, and the control value is set to make the laser characteristics of the second pulse after the first pulse close to the target value through feedback control based on the difference between the laser characteristics of the first pulse of the pulsed laser and the target value.

4. The laser device according to claim 3, wherein The processor calculates a variation component of the laser characteristic that varies in synchronization with the rotation of the fan, and corrects the control value using the variation component.

5. The laser device according to claim 4, wherein The processor corrects the control value based on a difference between a first value of the variation component corresponding to a first timing when the laser oscillation of the first pulse is performed and a second value of the variation component corresponding to a second timing when the laser oscillation of the second pulse is performed.

6. The laser device according to claim 5, wherein The processor acquires the first time by measurement, and acquires the second time by calculation based on the first time and the repetition frequency.

7. The laser device according to claim 5, wherein The first time and the second time are elapsed times based on the time when the detection signal is received.

8. The laser device according to claim 1, wherein The processor corrects the control value using a periodic function having an inverse of a rotation frequency of the fan as a period.

9. The laser device according to claim 8, wherein The laser device further includes a laser detector for measuring the laser characteristics. The processor obtains the time series data of the laser characteristics from the laser detector, The processor fits a sine curve to the time series data to obtain the periodic function.

10. The laser device according to claim 9, wherein The processor performs Fourier analysis on the time series data and obtains the amplitude of the sine curve according to the intensity corresponding to the rotation frequency. The processor fits the sinusoidal curve having the amplitude to the time series data.

11. The laser device according to claim 1, wherein The processor is configured to access data containing a correspondence between the repetition frequency and a parameter for correcting the control value. The processor corrects the control value using the parameter obtained by retrieving the data using the repetition frequency.

12. The laser device according to claim 1, wherein The processor is configured to access data including a correspondence relationship between the repetition frequency, the rotation frequency of the fan, and a parameter for correcting the control value. The processor corrects the control value using the parameter acquired by searching the data using the repetition frequency and the rotation frequency.

13. The laser device according to claim 1, wherein The laser characteristics include a first characteristic being one of pulse energy, wavelength, and line width and a second characteristic being the other. The adjuster includes a first adjuster for adjusting the first characteristic and a second adjuster for adjusting the second characteristic. The processor corrects both a first control value of the first adjuster and a second control value of the second adjuster based on the repetition frequency and the detection signal, and controls the first adjuster and the second adjuster.

14. The laser device according to claim 1, wherein The fan includes a plurality of blades arranged around a rotation axis. The processor corrects the control value using a periodic function having an inverse of a blade frequency as a period, the blade frequency being a product of a rotation frequency of the fan and the number of blades.

15. The laser device according to claim 1, wherein The processor corrects the control value using a first periodic function having a first period and synchronized with the rotation of the fan and a second periodic function having a second period shorter than the first period and synchronized with the rotation of the fan.

16. The laser device according to claim 1, wherein The fan includes a plurality of blades arranged around a rotation axis. The processor corrects the control value using a first periodic function having an inverse of the fan's rotational frequency as a period and a second periodic function having an inverse of a blade frequency as a period, the blade frequency being given by the product of the rotational frequency and the number of blades.

17. The laser device according to claim 16, wherein: The laser device further includes a laser detector for measuring the laser characteristics. The processor obtains the time series data of the laser characteristics from the laser detector, The processor fits a first sine curve to the time series data to obtain the first periodic function, The processor fits a second sine curve to the difference between the time series data and the first periodic function to obtain the second periodic function.

18. The laser device according to claim 17, wherein The processor performs Fourier analysis on the time series data, calculates a first amplitude of the first sinusoidal curve based on a first intensity corresponding to the rotation frequency, and calculates a second amplitude of the second sinusoidal curve based on a second intensity corresponding to an observation frequency, wherein the observation frequency is a frequency when the frequency component of the blade frequency is sampled at the repetition frequency. The processor fits the first sinusoidal curve having the first amplitude to the time series data, The processor fits the second sinusoidal curve having the second amplitude to the difference.

19. A method for controlling a laser device, wherein: The laser device has: Laser cavity; a pair of discharge electrodes disposed in the laser cavity; a fan disposed in the laser cavity to cause the laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector that detects rotation of the fan; and an adjuster that adjusts laser characteristics of the pulsed laser generated in the laser cavity, The control method comprises the following steps: In the laser device, the control value of the regulator is corrected according to the repetition frequency of the pulsed laser and the detection signal of the rotation detector. The regulator is controlled using the corrected control value.

20. A method for manufacturing an electronic device, comprising the following steps: Generate pulsed laser light through a laser device, Outputting the pulse laser to an exposure device, exposing the pulsed laser light on a photosensitive substrate in the exposure device to manufacture the electronic device. The laser device has: Laser cavity; a pair of discharge electrodes disposed in the laser cavity; a fan disposed in the laser cavity to cause the laser gas in the laser cavity to flow between the pair of discharge electrodes; a rotation detector that detects rotation of the fan; an adjuster for adjusting laser characteristics of the pulsed laser generated in the laser cavity; as well as A processor corrects a control value of the adjuster according to the repetition frequency of the pulsed laser and the detection signal of the rotation detector, and controls the adjuster using the corrected control value.

Images