Method for adjusting spectral linewidth, and method for manufacturing electronic devices

Abstract

This invention provides a method for narrowing the spectral linewidth of a laser beam to a level where chromatic aberration is negligible. [Solution] The adjustment method includes: a first step of adjusting at least one of the timing of a first trigger signal that amplifies a portion of the first pulsed laser light and converts it into a second pulsed laser light, and the timing of a second trigger signal that amplifies a portion of the second continuous light and converts it into a third pulsed laser light, thereby adjusting the spectrum of the fourth pulsed laser light, which is obtained by sum-frequency mixing of the second pulsed laser light and the third pulsed laser light, to a first spectrum with a non-Gaussian shape; and a second step of causing a modulation signal generator to generate a modulation signal of the same pattern synchronized with the emission trigger signal, and providing the modulation signal of the same pattern to an optical phase modulator, thereby modulating the wavelength of the second continuous light within a time corresponding to one pulse of the third pulsed laser light, thereby adjusting the spectrum of the fourth pulsed laser light to a wider spectral linewidth.

Description

[Technical Field]

[0001] This disclosure relates to a method for adjusting spectral linewidth and a method for manufacturing an electronic device. [Background technology]

[0002] In recent years, semiconductor lithography equipment has been required to improve resolution as semiconductor integrated circuits become smaller and more integrated. Therefore, efforts are being made to shorten the wavelength of light emitted from lithography light sources. For example, gas laser equipment used for lithography includes KrF excimer laser equipment that outputs laser light with a wavelength of approximately 248 nm, and ArF excimer laser equipment that outputs laser light with a wavelength of approximately 193 nm.

[0003] The spectral linewidth of the spontaneously emitted light from KrF and ArF excimer laser systems is broad, 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 occur. As a result, resolution may decrease. Therefore, it is necessary to narrow the spectral linewidth of the laser light output from a gas laser system until chromatic aberration is negligible. For this reason, gas laser systems may be equipped with a Line Narrowing Module (LNM) containing narrowing elements (such as etalons or gratings) within the laser resonator to narrow the spectral linewidth. In the following, a gas laser system with a narrowed spectral linewidth will be referred to as a narrow-band gas laser system. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. WO2024 / 057673 [Patent Document 2] Summary of Japanese Patent Publication No. 2010-238684

[0005] A spectral linewidth adjustment method relating to one aspect of this disclosure includes: a first semiconductor laser emitting a first continuous light; a first amplifier that amplifies a portion of the first continuous light in synchronization with a light emission trigger signal received from an external device and converts it into a first pulsed laser light; a second amplifier that amplifies a portion of the first pulsed laser light in synchronization with a first trigger signal generated in synchronization with the light emission trigger signal and converts it into a second pulsed laser light; a second semiconductor laser emitting a second continuous light; a third amplifier that amplifies a portion of the second continuous light in synchronization with a second trigger signal generated in synchronization with the light emission trigger signal and converts it into a third pulsed laser light; an optical phase modulator arranged in the optical path of the second continuous light between the second semiconductor laser and the third amplifier; a modulation signal generator that outputs a modulation signal to be supplied to the optical phase modulator; and the second pulsed laser light and the third pulsed laser light. A method for adjusting the spectral linewidth of pulsed laser light output by a laser device comprising: a wavelength conversion system that converts the wavelength by sum-frequency mixing of pulsed laser light and outputs a fourth pulsed laser light, the method comprising: a first step of adjusting at least one of the timing of a first trigger signal and the timing of a second trigger signal to adjust the spectrum of the fourth pulsed laser light to a first spectrum with a non-Gaussian shape; and a second step of causing a modulation signal generator to generate a modulation signal of the same pattern synchronized with the emission trigger signal, and providing the modulation signal of the same pattern to an optical phase modulator, thereby modulating the wavelength of the second continuous light within a time corresponding to one pulse of the third pulsed laser light, and adjusting the spectrum of the fourth pulsed laser light to a second spectrum having a wider spectral linewidth than the first spectrum.

[0006] A method for manufacturing an electronic device relating to another aspect of the present disclosure is a method for manufacturing an electronic device comprising: a first semiconductor laser emitting a first continuous light; a first amplifier that amplifies a portion of the first continuous light in synchronization with a light emission trigger signal received from an external device and converts it into a first pulsed laser light; a second amplifier that amplifies a portion of the first pulsed laser light in synchronization with a first trigger signal generated in synchronization with the light emission trigger signal and converts it into a second pulsed laser light; a second semiconductor laser emitting a second continuous light; a third amplifier that amplifies a portion of the second continuous light in synchronization with a second trigger signal generated in synchronization with the light emission trigger signal and converts it into a third pulsed laser light; an optical phase modulator arranged in the optical path of the second continuous light between the second semiconductor laser and the third amplifier; a modulation signal generator that outputs a modulation signal to be given to the optical phase modulator; and the second pulsed laser light and the third pulsed laser light. The laser device comprises a wavelength conversion system that combines the sum frequency of two pulses to convert the wavelength and outputs a fourth pulsed laser beam, and includes a laser device that generates a fourth pulsed laser beam by adjusting the timing of at least one of a first trigger signal and a second trigger signal to adjust the spectrum of the fourth pulsed laser beam to a first spectrum with a non-Gaussian shape, modulates the wavelength of a second continuous light within a time equivalent to one pulse of the third pulsed laser beam by causing a modulation signal generator to generate a modulation signal of the same pattern synchronized with the emission trigger signal, and provides the modulation signal of the same pattern to an optical phase modulator, thereby adjusting the spectrum of the fourth pulsed laser beam to a second spectrum having a wider spectral linewidth than the first spectrum, outputs the fourth pulsed laser beam to an exposure apparatus, and exposes a photosensitive substrate with the fourth pulsed laser beam in the exposure apparatus in order to manufacture an electronic device. [Brief explanation of the drawing]

[0007] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 schematically shows the configuration of the laser apparatus in the comparative example. [Figure 2] Figure 2 shows a schematic representation of the solid seeder configuration. [Figure 3]Figure 3 shows an example of a pseudo-random signal generator. [Figure 4] Figure 4 shows a flowchart illustrating an example of spectral linewidth control in a comparative example. [Figure 5] Figure 5 shows a flowchart of other control examples for spectral linewidth in the comparative example. [Figure 6] Figure 6 schematically shows the configuration of the laser device according to Embodiment 1. [Figure 7] Figure 7 shows a schematic representation of the solid seeder configuration. [Figure 8] Figure 8 shows the timing chart during laser operation. [Figure 9] Figure 9 shows a flowchart for timing adjustment. [Figure 10] Figure 10 shows a flowchart of the first step of Embodiment 1. [Figure 11] Figure 11 shows the timing chart for the first step. [Figure 12] Figure 12 shows the spectrum of the fourth pulsed laser light during the adjustment in the first step. [Figure 13] Figure 13 shows an example of determining a non-Gaussian waveform. [Figure 14] Figure 14 shows a flowchart of the second step. [Figure 15] Figure 15 shows the spectrum of the fourth pulsed laser beam after the search in the second step. [Figure 16] Figure 16 shows a flowchart of the first step of Embodiment 2. [Figure 17] Figure 17 shows the spectrum of the fourth pulsed laser light during the adjustment in the first step. [Figure 18] Figure 18 shows the spectrum of the fourth pulsed laser beam after the search in the second step. [Figure 19] Figure 19 shows a flowchart of the first step of Embodiment 3. [Figure 20] Figure 20 shows the spectrum of the fourth pulsed laser light during the adjustment in the first step. [Figure 21] FIG. 21 shows the spectrum of the fourth pulsed laser beam after the search in the second step. [Figure 22] FIG. 22 schematically shows a configuration example of an exposure apparatus. Embodiment

[0008] -Contents- 1. Comparative Example 1.1 Laser Device 1.1.1 Configuration 1.1.2 Operation​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The embodiments of this disclosure will be described in detail below with reference to the drawings. The embodiments described below are examples of the disclosure and are not intended to limit the scope of this disclosure. Furthermore, not all configurations and operations described in each embodiment are necessarily essential to the configurations and operations of this disclosure. The same reference numerals are used for identical components, and redundant descriptions are omitted.

[0010] 1. Comparative Example 1.1 Laser equipment 1.1.1 Configuration Figure 1 schematically shows the configuration of the laser apparatus 10 according to the comparative example. The comparative example in this disclosure is a form that the applicant recognizes as being known only to the applicant, and is not a prior art example acknowledged by the applicant.

[0011] The laser device 10 includes a solid-state seeder 20 as a master oscillator (MO) that generates pulsed laser light, an excimer amplifier 30 as a power amplifier (PA) that amplifies the output light of the solid-state seeder 20, a monitor module 40, an output shutter 46, and a laser control processor 50.

[0012] The solid-state seeder 20 outputs pulsed laser light with a central wavelength of approximately 193.4 nm.

[0013] The excimer amplifier 30 includes a chamber 31, a pulsed power module (PPM) 32, a charger 33, a convex mirror 34, and a concave mirror 35. The chamber 31 includes windows 36a and 36b, a pair of electrodes 37a and 37b, and an electrical insulating member 38. ArF laser gas is supplied into the chamber 31 from a gas supply device (not shown). The ArF laser gas includes Ar gas, F2 gas, and Ne gas.

[0014] The PPM32 includes a switch 39 and a charging capacitor (not shown). A charger 33 holds electrical energy to supply to the PPM32. The charger 33 is connected to the charging capacitor (not shown). The charger 33 charges the charging capacitor of the PPM32 according to commands from the laser control processor 50.

[0015] The PPM32 is connected to electrode 37b in the chamber 31 via a feedthrough in the electrical insulating member 38. Electrode 37a is connected to ground potential.

[0016] Windows 36a and 36b are positioned so that pulsed laser light amplified by discharge excitation between electrodes 37a and 37b can pass through.

[0017] The convex mirror 34 and the concave mirror 35 are positioned such that the pulsed laser beam output from the solid-state seeder 20 passes through the discharge space between electrodes 37a and 37b three times, causing the beam to expand.

[0018] The monitor module 40 includes beam splitters 41 and 42, a spectrum monitor 43, and an optical sensor 44. Beam splitter 41 is positioned on the optical path of pulsed laser light output from the excimer amplifier 30 so that pulsed laser light reflected by beam splitter 41 is incident on beam splitter 42. Beam splitter 41 may be positioned outside the monitor module 40.

[0019] The beam splitter 42 is positioned such that the pulsed laser light reflected by the beam splitter 42 is incident on the spectrum monitor 43, and the pulsed laser light that passes through the beam splitter 42 is incident on the optical sensor 44.

[0020] The spectrum monitor 43 monitors the spectrum of the incident pulsed laser light and detects the oscillation wavelength of the incident pulsed laser light. The spectrum monitor 43 may be, for example, an etalon spectrometer. An etalon spectrometer includes a diffuser plate for diffusing sample light, an etalon, a focusing lens positioned on the output side of the etalon, and a photodiode array positioned at the focal plane of the focusing lens to detect the interference fringe pattern, and can detect the wavelength by measuring the diameter of the interference fringes.

[0021] The optical sensor 44 detects the pulse energy of the incident pulsed laser light. The optical sensor 44 may be, for example, a photodiode.

[0022] The output shutter 46 is positioned on the optical path of the pulsed laser light output from the laser device 10 to the outside, and is configured to switch between outputting the pulsed laser light to the outside and blocking it. The pulsed laser light that has passed through the beam splitter 41 is emitted from the laser device 10 via the output shutter 46.

[0023] The laser device 10 is connected to the exposure device 60 via a beam delivery unit (BDU), which is not shown. The BDU is an optical system that transmits pulsed laser light from the laser device 10 to the exposure device 60. The pulsed laser light emitted from the laser device 10 enters the exposure device 60 via the BDU.

[0024] The exposure apparatus 60 includes an exposure control processor 61. The exposure control processor 61 controls the exposure apparatus 60. The exposure control processor 61 is also connected to the laser control processor 50. The exposure apparatus 60 is an example of an "external device" in this disclosure.

[0025] The laser control processor 50 receives the target center wavelength, target linewidth, target pulse energy, and emission trigger signal from the exposure control processor 61. The laser control processor 50 also sends a trigger A signal and a charging voltage value to the excimer amplifier 30, and a trigger B signal, a linewidth control signal, a temperature value, and a current value to the solid-state seeder 20 to operate the laser device 10 and control the pulsed laser light. In this specification, a processor is a processing unit that includes a memory device storing a control program and a CPU (Central Processing Unit) that executes the control program. The processor is specially configured or programmed to perform the various processes included in this disclosure.

[0026] Figure 2 schematically shows the configuration of the solid-state seeder 20. The solid-state seeder 20 includes a first solid-state laser device 100, a second solid-state laser device 110, a dichroic mirror 130, a wavelength conversion system 140, a pseudo-random signal generator 150, and a solid-state seeder control processor 160.

[0027] The solid-state seeder 20 is a system configuration in which pulsed laser light with a wavelength of approximately 1554 nm output from the first solid-state laser device 100 and pulsed laser light with a wavelength of approximately 257.6 nm output from the second solid-state laser device 110 are converted into pulsed laser light with a wavelength of approximately 193.4 nm by double sum frequency in the wavelength conversion system 140.

[0028] The first solid-state laser apparatus 100 includes a semiconductor laser system 101 and a solid-state amplifier 102. The semiconductor laser system 101 includes a first semiconductor laser that oscillates in a single longitudinal mode in continuous wave (CW) at a wavelength of approximately 1554 nm and emits a first continuous beam of light.

[0029] The solid-state amplifier 102 may be an optical parametric amplifier (OPA). The OPA may be, for example, PPLN (periodically poled lithium niobate crystal) or PPKTP (periodically poled potassium titanyl phosphate crystal).

[0030] The solid-state amplifier 102 is configured to pulse-amplify the seed light by receiving a pulsed laser beam with a wavelength of 1030 nm (described later) as the pump light and a laser beam output from the semiconductor laser system 101 as the seed light.

[0031] The second solid-state laser device 110 includes a semiconductor laser system 111, an optical phase modulator 112, a solid-state amplifier 113, two nonlinear crystals, an LBO crystal 114 and a CLBO crystal 115, which perform two second harmonic generations and wavelength conversion so that the optical frequency quadruples, and a dichroic mirror 116. "LBO" is represented by the chemical formula LiB3O5. "CLBO" is represented by the chemical formula CsLiB6O 10 It is represented as follows.

[0032] The semiconductor laser system 111 includes a second semiconductor laser that oscillates in a single longitudinal mode in CW at a wavelength of approximately 1030 nm and emits a second continuous beam of light.

[0033] The solid-state amplifier 113 may have a configuration including, for example, a Yb fiber amplifier or a Yb:YAG crystal. The solid-state amplifier 113 may have a configuration similar to that of the solid-state amplifier 102.

[0034] The optical phase modulator 112 is positioned on the optical path between the semiconductor laser system 111 and the solid-state amplifier 113.

[0035] The dichroic mirror 116 is positioned in the optical path between the LBO crystal 114 and the CLBO crystal 115, and transmits pulsed laser light with a wavelength of approximately 515 nm with high transmittance and reflects pulsed laser light with a wavelength of approximately 1030 nm with high reflectance. The dichroic mirror 116 is positioned so that the highly reflected pulsed laser light with a wavelength of approximately 1030 nm is incident as the pump light for the solid-state amplifier 102. Instead of the dichroic mirror 116, a beam splitter (not shown) may be placed between the solid-state amplifier 113 and the LBO crystal 114 to split the pulsed laser light emitted from the solid-state amplifier 113 so that it is incident on the LBO crystal 114 and the solid-state amplifier 102, respectively.

[0036] The dichroic mirror 130 is configured to highly reflect pulsed laser light with a wavelength of approximately 1554 nm output from the first solid-state laser device 100 and highly transmit pulsed laser light with a wavelength of approximately 257.6 nm output from the second solid-state laser device 110, and is positioned so that both pulsed laser beams are incident coaxially on the wavelength conversion system 140.

[0037] The wavelength conversion system 140 includes CLBO crystals 141 and 142, and rotating stages 143 and 144. The CLBO crystals 141 and 142 are placed on rotating stages 143 and 144, which each contain a piezoelectric element, and are configured so that the incident angle of each crystal can be changed at high speed.

[0038] The pseudo-random signal generator 150 outputs a modulation signal to be supplied to the optical phase modulator 112. The pseudo-random signal generator 150 consists of a multi-stage shift register and a variable band filter (digital filter), which are not shown in Figure 2.

[0039] The solid-state seeder control processor 160 controls the wavelength, power, pulse waveform, spectrum, etc., of the laser light output by the solid-state seeder 20. Based on the input from the laser control processor 50, the solid-state seeder control processor 160 controls the first solid-state laser device 100, the second solid-state laser device 110, the dichroic mirror 130, the wavelength conversion system 140, and the pseudo-random signal generator 150.

[0040] 1.1.2 Operation In the solid-state seeder 20, the wavelength of the pulsed laser light output from the second solid-state laser device 110 is fixed, and the wavelength of the pulsed laser light output from the first solid-state laser device 100 is changed for each pulse, thereby changing the wavelength of the pulsed laser light output from the wavelength conversion system 140.

[0041] The operation of the second solid-state laser device 110 is as follows: The solid-state seeder control processor 160 fixes the oscillation wavelength of the second solid-state laser device 110 to 1030 nm. That is, the solid-state seeder control processor 160 keeps the current value of the second semiconductor laser in the semiconductor laser system 111 constant, causing the second semiconductor laser to oscillate continuously and output CW laser light from the second semiconductor laser.

[0042] The CW laser light output from the semiconductor laser system 111 is phase-modulated by the optical phase modulator 112 and then incident on the solid-state amplifier 113.

[0043] The solid-state seeder control processor 160 transmits to the pseudo-random signal generator 150 the same timing signal as the trigger B signal acquired from the laser control processor 50, as well as a reset signal to the shift register of the pseudo-random signal generator 150.

[0044] The pseudo-random signal generator 150 receives a reset signal from the solid-state seeder control processor 160 to the shift register and generates a pseudo-random signal of the same pattern in synchronization with the trigger B signal.

[0045] In a pseudo-random signal, unwanted spectral components at higher frequencies are removed by a variable band filter.

[0046] The optical phase modulator 112 modulates the CW laser light by phase-modulating it with a pseudo-random signal from the pseudo-random signal generator 150 that is limited to an appropriate frequency band, thereby changing its spectrum.

[0047] Changing the cutoff frequency of the variable band filter of the pseudo-random signal generator 150 to a higher frequency widens the spectral linewidth of the light, while changing it to a lower frequency narrows it. Furthermore, changing the timing of the reset signal to the shift register of the pseudo-random signal generator 150 also changes the waveform and spectrum of the pseudo-random signal, and consequently, the spectral linewidth of the laser light output from the optical phase modulator 112 also changes.

[0048] To control the spectral linewidth, the spectral linewidth of the laser light is measured, and the frequency of the pseudo-random signal is adjusted based on the measured spectral linewidth. Specifically, the cutoff frequency of the variable band filter is adjusted.

[0049] The solid-state seeder control processor 160, in synchronization with the trigger B signal, pulses the CW laser light, which has been phase-modulated by the optical phase modulator 112, using the solid-state amplifier 113. The solid-state amplifier 113 outputs pulsed laser light with a wavelength of 1030 nm.

[0050] The pulsed laser light with a wavelength of 1030 nm output from the solid-state amplifier 113 is converted to second harmonic light with a wavelength of 515 nm by the LBO crystal 114. The second harmonic light with a wavelength of 515 nm is highly transmitted through the dichroic mirror 116 and converted to pulsed laser light with a wavelength of 257.6 nm by the CLBO crystal 115. The LBO crystal 114 and the CLBO crystal 115 are examples of "wavelength conversion crystals" in this disclosure.

[0051] Here, the dichroic mirror 116 highly reflects the pulsed laser light with a wavelength of 1030 nm that was not wavelength-converted by the LBO crystal 114, and directs it as pump light into the solid-state amplifier 102 of the first solid-state laser device 100.

[0052] On the other hand, the laser control processor 50 and the solid-state seeder control processor 160 can change the wavelength of the pulsed laser light output from the first solid-state laser device 100 around 1554 nm by controlling the temperature and / or current value of the first semiconductor laser in the semiconductor laser system 101 of the first solid-state laser device 100. The solid-state seeder control processor 160 may also change the oscillation wavelength of the semiconductor laser system 101 for each pulse.

[0053] The pulsed laser light with a wavelength of approximately 1554 nm output from the first solid-state laser device 100 and the pulsed laser light with a wavelength of 257.6 nm output from the second solid-state laser device 110 are sum-frequency mixed by the CLBO crystal 141 of the wavelength conversion system 140, and wavelength converted to pulsed laser light with a wavelength of approximately 220.9 nm. Furthermore, the pulsed laser light with a wavelength of approximately 220.9 nm and the pulsed laser light with a wavelength of approximately 1554 nm are sum-frequency mixed by the CLBO crystal 142, and wavelength converted to pulsed laser light with a wavelength of approximately 193.4 nm. Then, pulsed laser light with a wavelength of approximately 193.4 nm is output from the wavelength conversion system 140.

[0054] The variable wavelength range of the pulsed laser light output from the solid-state seeder 20 is approximately 193.2 nm to 193.5 nm, which is the amplification wavelength band of the excimer amplifier 30.

[0055] A trigger A signal is input to the switch 39 of the PPM 32 so that a discharge occurs in synchronization with the pulsed laser light output from the solid-state seeder 20 entering the discharge space of the chamber 31 of the excimer amplifier 30. As a result, the pulsed laser light output from the solid-state seeder 20 is amplified in three passes by the excimer amplifier 30.

[0056] The pulsed laser light amplified by the excimer amplifier 30 is sampled by the beam splitter 41 and beam splitter 42 of the monitor module 40, and the spectrum and pulse energy are measured by the spectrum monitor 43 and the optical sensor 44.

[0057] Based on the measured spectrum of the pulsed laser light output from the excimer amplifier 30, the laser control processor 50 sends a control signal for the center wavelength to the solid-state seeder control processor 160 so that the center wavelength approaches the target value, which is the target center wavelength. Based on the control signal obtained from the laser control processor 50, the solid-state seeder control processor 160 sends command values ​​for temperature and current to the semiconductor laser system 101. Based on the command values ​​for temperature and current obtained from the solid-state seeder control processor 160, the semiconductor laser system 101 changes the temperature and current of its semiconductor laser to change the oscillation wavelength.

[0058] Furthermore, based on the measured spectrum of the pulsed laser light output from the excimer amplifier 30, the laser control processor 50 sends a spectral linewidth control signal to the solid-state seeder control processor 160 so that the spectral linewidth approaches the target value. Based on the control signal obtained from the laser control processor 50, the solid-state seeder control processor 160 changes the signal bandwidth and power of the modulated signal output from the pseudo-random signal generator 150.

[0059] The optical phase modulator 112 changes the spectral linewidth of the laser light output from the optical phase modulator 112 based on the signal bandwidth and power of the output from the pseudo-random signal generator 150.

[0060] Furthermore, the laser control processor 50 changes the charging voltage of the charger 33 so that the measured pulse energy of the pulsed laser light output from the excimer amplifier 30 approaches the target value, which is the target pulse energy.

[0061] With the above configuration and operation, the wavelength of the second continuous light is modulated within the time equivalent to one pulse of the pulsed laser light, and the spectral linewidth of the pulsed laser light is adjusted. A pseudo-random signal with the same pattern is generated in synchronization with the trigger B signal, which is synchronized with the timing of the generation of the pulsed laser light, and is superimposed on the optical phase modulator 112. As a result, a modulated signal with the same waveform is superimposed on the optical phase modulator 112 for each pulse, and the spectrum of the superimposed signal is also the same for each pulse. Therefore, since the pulsed laser light output from the optical phase modulator 112 is modulated the same for each pulse, the spectrum is the same for each pulse, and the spectral linewidth is also the same for each pulse, resulting in stability.

[0062] Furthermore, when operating the pseudo-random signal generator 150 in synchronization with the trigger B signal to change the spectrum, a search flow is required to update the initial value of the shift register until the spectrum becomes unimodal in order to make its shape unimodal.

[0063] 1.2 Configuration of a pseudo-random signal generator An initial value setting circuit is added to the pseudo-random signal generator, and the initial value of the shift register is adjusted so that the generated spectrum is unimodal.

[0064] Figure 3 shows an example of a pseudo-random signal generator 150. The pseudo-random signal generator 150 includes a shift register 151, at least one exclusive OR (XOR) circuit 152, a variable band filter 153, an amplifier 154, a trigger regeneration circuit 155, and an initial value setting circuit 156.

[0065] The shift register 151 consists of 36 D flip-flops FF1 to FF36 connected in series. The Q output of the 11th stage D flip-flop FF11 and the Q output of the 36th stage D flip-flop FF36 are inputs to the XOR circuit 152, and the output of the XOR circuit 152 is fed back to the 1st stage D flip-flop. The Q output of the 36th stage D flip-flop FF36 is 2 times the clock. 36 - Each time you count (cycle 2 36-1) The same random pattern (pseudo-random pattern) is repeated. The Q output of the 36th stage D flip-flop FF36 is input to the variable band filter 153, and the output of the variable band filter 153 is amplified and output by the amplifier 154. The passband of the variable band filter 153 and the output power of the amplifier 154 are controlled by control signals from the solid-state seeder control processor 160.

[0066] The trigger regeneration circuit 155 generates timing signals that change the initial values ​​of the D flip-flops FF1 to FF36 from the trigger B signal from the solid-state seeder control processor 160 and the high-speed internal clock of the pseudo-random signal generator 150.

[0067] The initial value setting circuit 156, in synchronization with the timing signal generated by the trigger regeneration circuit 155, sends signals to the SET terminal or CLR terminal of the D flip-flops FF1 to FF36 based on a control signal from the solid-state seeder control processor 160, so that the initial value of the D flip-flops FF1 to FF36 is set to "0" or "1" ("Low" or "Hi"). For example, to set the initial value to "0", a signal is sent to the CLR terminal, and to set the initial value to "1", a signal is sent to the SET terminal.

[0068] Here, we have shown an example using 36 D flip-flops, but the number of D flip-flop stages is not limited to this example. For example, the number of stages, feedback positions, and the number of XOR circuits 152 can be appropriately arranged and connected according to a well-known feedback polynomial. Also, the shift register 151, which is composed of multiple D flip-flops, may be constructed using an FPGA (Field Programmable Gate Array), etc. Furthermore, although the power of the output modulation signal is adjusted by the amplifier 154 here, the output power can also be adjusted by inserting a variable attenuator after or before the amplifier 154.

[0069] An XNOR circuit may be used instead of the XOR circuit 152. The pseudo-random signal generator 150 is an example of a "modulated signal generator" in this disclosure.

[0070] 1.3 Example of a Pseudo-Random Signal Generator in Operation 1 Figure 4 shows a flowchart of an example of spectral linewidth control in a comparative example. In step S1, the laser control processor 50 measures the spectrum of the output pulsed laser light of the excimer amplifier 30 using the spectrum monitor 43 of the monitor module 40.

[0071] In step S2, the laser control processor 50 examines whether the measured spectrum is unimodal or multimodal and determines whether the spectrum has a unimodal shape. If the determination result in step S2 is NO, that is, if the spectrum is multimodal, the laser control processor 50 proceeds to step S3.

[0072] In step S3, the laser control processor 50 changes the initial value of the shift register 151 via the solid-state seeder control processor 160, and then returns to step S1.

[0073] On the other hand, if the result of step S2 is a YES determination, that is, if the spectrum is unimodal, the laser control processor 50 proceeds to step S4.

[0074] In step S4, the laser control processor 50 measures the spectral linewidth from the acquired spectrum.

[0075] In step S5, the laser control processor 50 calculates the difference between the target line width, which is periodically updated by the exposure control processor 61, and the measurement result from step S4.

[0076] In step S6, the laser control processor 50 determines whether the calculated difference is within an acceptable range. If the determination result in step S6 is YES, that is, if the difference is within an acceptable range, the laser control processor 50 returns to step S1.

[0077] On the other hand, if the result of step S6 is a NO judgment, that is, if the difference is not within the acceptable range, the laser control processor 50 proceeds to step S7.

[0078] In step S7, the laser control processor 50 determines the power of the modulated signal using a function that shows the relationship between the square root of the power of the modulated signal and the spectral linewidth, which has been determined in advance, and the difference calculated in step S5. It then changes the power of the modulated signal superimposed on the optical phase modulator 112 and returns to step S1. However, instead of using the relationship between the square root of the power of the modulated signal and the spectral linewidth, which has been determined in advance, a recorded table list of the relationship between the square root of the power of the modulated signal and the spectral linewidth may be used. Alternatively, instead of adjusting the power of the modulated signal, the bandwidth of the modulated signal may be adjusted using the variable band filter 153.

[0079] 1.4 Action and Effects By adjusting the initial value of the shift register 151, it becomes possible to always control the spectral linewidth to the target spectral linewidth with a unimodal spectrum.

[0080] Because the relationship between the square root of the modulated signal power and the spectral linewidth is highly linear, linewidth control can be performed more easily and with greater precision by adjusting the power of the modulated signal.

[0081] Furthermore, because the relationship between the bandwidth of the modulated signal and the spectral linewidth is highly linear, linewidth control can be performed more easily and with greater precision by adjusting the bandwidth of the modulated signal.

[0082] 1.5 Example 2 of the operation of a pseudo-random signal generator Figure 5 shows a flowchart of another example of spectral linewidth control in the comparative example. In this example, the spectral linewidth is coarsely adjusted by the bandwidth of the modulated signal and finely adjusted by the power of the modulated signal. The processing in steps S1 to S5 is the same as in the flowchart shown in Figure 4.

[0083] In step S8, following step S5, the laser control processor 50 determines whether the difference calculated in step S5 is within the acceptable range for coarse adjustment. If the determination result in step S8 is NO, that is, if the difference is not within the acceptable range for coarse adjustment, the laser control processor 50 proceeds to step S9.

[0084] In step S9, the laser control processor 50 changes the bandwidth of the modulation signal superimposed on the optical phase modulator 112 using the variable band filter 153. The operation in step S9 may also be performed by the solid-state seeder control processor 160 according to the commands of the laser control processor 50. After step S9, the laser control processor 50 returns to step S1.

[0085] If the result of step S8 is YES, that is, if the difference is within the acceptable range for coarse adjustment, the laser control processor 50 proceeds to step S10. In step S10, the laser control processor 50 determines whether the difference calculated in step S5 is within the acceptable range for fine adjustment. If the result of step S10 is YES, that is, if the difference is within the acceptable range for fine adjustment, the laser control processor 50 returns to step S1.

[0086] If the result of step S10 is a NO judgment, that is, if the difference is not within the acceptable range for fine adjustment, the laser control processor 50 proceeds to step S7. The processing in step S7 is the same as the flowchart shown in Figure 4. After step S7, the laser control processor 50 returns to step S1. The operation in step S7 may also be performed by the solid-state seeder control processor 160 according to the commands of the laser control processor 50.

[0087] 1.6 Action and Effects By adjusting the initial value of the shift register 151, it is possible to always control the spectral linewidth to the target spectral linewidth with a unimodal spectrum. Furthermore, since the method employs changing the bandwidth of the modulation signal when coarsely adjusting the spectral linewidth and changing the power of the modulation signal when finely adjusting it, the amount by which the modulation signal power is changed is smaller compared to when the linewidth is controlled solely by the power of the modulation signal. As a result, the stability of the entire modulation signal generator, including the pseudo-random signal generator 150, is improved, the thermal load on the optical phase modulator 112 is reduced, and stable control becomes possible.

[0088] Furthermore, compared to controlling the linewidth solely by the bandwidth of the modulated signal, using changes in the power of the modulated signal allows for finer setting resolution.

[0089] 1.7 Challenges In the technique of adjusting the spectrum of laser light using a pseudo-random signal generator 150 consisting of a multi-stage shift register 151 and a variable bandpass filter 153, and an optical phase modulator 112, when widening the spectral linewidth defined by Full Width at Half Maximum (FWHM), E95 width, etc., while maintaining unimodality such as a Gaussian waveform, there was a limit to the adjustment range of the spectral linewidth (especially the upper limit of the spectral linewidth) because the amplitude of the optical phase modulation is finite.

[0090] For example, when obtaining a wider spectral linewidth, such as 0.5 pm, compared to the E95 linewidth of 0.2 pm to 0.5 pm required for semiconductor lithography, it was difficult to obtain a sufficiently wide spectral linewidth using optical phase modulation alone.

[0091] 2. Embodiment 1 2.1 Configuration 2.1.1 Laser equipment Figure 6 schematically shows the configuration of the laser device 11 according to Embodiment 1. The differences between the configuration shown in Figure 6 and that in Figure 1 will be explained. The laser device 11 includes a solid-state seeder 21 instead of the solid-state seeder 20 in Figure 1.

[0092] 2.1.2 Solid Seed Figure 7 schematically shows the configuration of the solid-state seeder 21. The differences between the configuration shown in Figure 7 and that shown in Figure 2 will be explained. The solid-state seeder 21 includes a first solid-state laser device 200 and a second solid-state laser device 210 instead of the first solid-state laser device 100 and the second solid-state laser device 110.

[0093] The first solid-state laser apparatus 200 includes a semiconductor laser system 101, a solid-state amplifier 202, a solid-state amplifier 203, and a solid-state amplifier 204.

[0094] Solid-state amplifiers 202 and 203 may be semiconductor optical amplifiers (SOAs). SOAs are, for example, multiple quantum well structures of InP / InGaAsP.

[0095] The solid-state amplifier 202, in response to a trigger signal 3 sent from the solid-state seeder control processor 160, extracts a portion of the CW laser light output from the semiconductor laser system 101 in a pulsed form, amplifies it, and converts it into the first pulsed laser light PL1. The solid-state amplifier 202 is an example of the "first amplifier" in this disclosure.

[0096] The solid-state amplifier 203, in response to a trigger 1 signal sent from the solid-state seeder control processor 160, further extracts and amplifies a portion of the first pulsed laser beam PL1 to form a second pulsed laser beam PL2. The trigger 1 signal is an example of the “first trigger signal” in this disclosure. The solid-state amplifier 203 is an example of the “second amplifier” in this disclosure.

[0097] The solid-state amplifier 204 is, for example, an optical fiber amplifier doped with a rare earth ion such as Yb. Based on the gain signal sent from the solid-state seeder control processor 160, the solid-state amplifier 204 amplifies the power of the second pulsed laser beam PL2 to produce the fifth pulsed laser beam PL5. Hereinafter, the amplification gain of the solid-state amplifier 204 will be referred to as Gain. The solid-state amplifier 204 is an example of the "fourth amplifier" in this disclosure.

[0098] The second solid-state laser device 210 has a configuration that does not include the dichroic mirror 116 compared to the second solid-state laser device 110. The solid-state amplifier 113, in response to the trigger 2 signal sent from the solid-state seeder control processor 160, pulses and amplifies the CW laser light output from the semiconductor laser system 111 to produce a third pulsed laser light PL3. The trigger 2 signal is an example of the "second trigger signal" in this disclosure. The solid-state amplifier 113 is an example of the "third amplifier" in this disclosure.

[0099] The LBO crystal 114 converts the third pulsed laser light PL3, with a wavelength of approximately 1030 nm, from the modulated and pulsed solid-state amplifier 113 into pulsed laser light with a wavelength of approximately 515 nm. The CLBO crystal 115 converts the pulsed laser light with a wavelength of approximately 515 nm, converted by the LBO crystal 114, into a sixth pulsed laser light PL6 with a wavelength of approximately 257.6 nm.

[0100] The fifth pulsed laser beam PL5 with a wavelength of approximately 1554 nm output from the first solid-state laser device 200 and the sixth pulsed laser beam PL6 with a wavelength of approximately 257.6 nm output from the second solid-state laser device 210 are sum-frequency mixed by the CLBO crystal 141 of the wavelength conversion system 140 and wavelength converted to pulsed laser beam with a wavelength of approximately 220.9 nm. Furthermore, the pulsed laser beam with a wavelength of approximately 220.9 nm is converted by the CLBO crystal 142 to a fourth pulsed laser beam PL4 with a wavelength of approximately 193.4 nm and output from the solid-state seeder 21.

[0101] The wavelength conversion system 140 may sum-frequency mix the second pulsed laser light PL2, which is the output of the solid-state amplifier 203 of the first solid-state laser device 200, instead of the fifth pulsed laser light PL5.

[0102] Alternatively, the wavelength conversion system 140 may be composed of an optical crystal that performs sum-frequency mixing at a different wavelength than in the example above, and the pulsed laser light from the first solid-state laser device 200 and the pulsed laser light from the second solid-state laser device 210 may be sum-frequency mixed to convert the wavelength and use it as the output of the solid-state seeder 21. In this case, the pulsed laser light from the first solid-state laser device 200 and the pulsed laser light from the second solid-state laser device 210 may each output wavelengths different from those in the example above.

[0103] In other words, the wavelength conversion system 140 may be configured to convert wavelengths by sum-frequency mixing of the second pulsed laser light PL2 or the fifth pulsed laser light PL5 from the first solid-state laser device 200 and the third pulsed laser light PL3 ​​or the sixth pulsed laser light PL6 from the second solid-state laser device 210.

[0104] The laser control processor 50 generates trigger A and trigger B signals in synchronization with the light emission trigger signal sent from the exposure control processor 61 of the exposure apparatus 60 shown in Figure 6. The solid-state seeder control processor 160 generates trigger 1, trigger 2, and trigger 3 signals in synchronization with trigger B signal. Therefore, trigger 1 to trigger 3 signals are synchronized with the light emission trigger signal.

[0105] 2.2 Operation 2.2.1 When laser operation is performed Figure 8 shows the timing chart during laser operation when the solid-state seeder 21 is operating, after the timing adjustments described later in Embodiment 1 have been completed.

[0106] The solid-state seeder control processor 160 receives spectral linewidth control signals, temperature and current values ​​for semiconductor laser systems 101 and 111, and a trigger B signal from the laser control processor 50, and performs the following controls (1) to (6).

[0107] (1) The solid-state seeder control processor 160 controls the oscillation wavelength and output of the CW light of the semiconductor laser system 101 and the semiconductor laser system 111 based on the temperature value and current value it receives.

[0108] (2) Based on the timing of the trigger B signal, the solid-state seeder control processor 160 resets the shift register 151 of the pseudo-random signal generator 150 and then operates the pseudo-random signal generator 150.

[0109] (3) The solid-state seeder control processor 160 controls the first solid-state laser device 200 by adding a delay time Delay1 based on the timing of the trigger B signal to generate a trigger 3 signal with a pulse width of W1. The solid-state amplifier 202 amplifies the CW light with a wavelength of approximately 1554 nm output from the semiconductor laser system 101 and converts it into the first pulsed laser light PL1. The pulse width of the first pulsed laser light is approximately W1.

[0110] (4) The solid-state seeder control processor 160 adds a delay time, Delay2, to the timing of the trigger 3 signal to generate a trigger 1 signal with a pulse width of W2. The solid-state amplifier 203 further amplifies the first pulsed laser beam PL1 output from the solid-state amplifier 202 and generates a second pulsed laser beam PL2 by cutting it out with a pulse width of approximately W2. The solid-state seeder control processor 160 may also generate the trigger 1 signal by adding a delay time of Delay1 + Delay2 based on the trigger B signal.

[0111] (5) The second pulsed laser beam PL2 output by the solid-state amplifier 203 is further amplified by the solid-state amplifier 204 to become the fifth pulsed laser beam PL5. The solid-state seeder control processor 160 adjusts the power of the fifth pulsed laser beam PL5, which is the output of the first solid-state laser device 200, by controlling the gain of the solid-state amplifier 204.

[0112] (6) Meanwhile, the solid-state seeder control processor 160 controls the second solid-state laser device 210 by adding a delay time, Delay3, based on the timing of the trigger B signal to generate a trigger 2 signal with a pulse width of W3. The solid-state amplifier 113 amplifies the CW light with a wavelength of approximately 1030 nm output from the semiconductor laser system 111 and modulated by the optical phase modulator 112, and also cuts it into pulses to form the third pulsed laser light PL3. The pulse width of the third pulsed laser light PL3 ​​is approximately W3.

[0113] The third pulsed laser beam PL3 is wavelength-converted to pulsed laser beam with a wavelength of approximately 257.6 nm via the LBO crystal 114 and CLBO crystal 115, and becomes the sixth pulsed laser beam PL6 as the output light of the second solid-state laser device 210.

[0114] Subsequently, the solid-state seeder control processor 160 adjusts the rotating stages 143 and 144 of the wavelength conversion system 140 to convert the fifth pulsed laser beam PL5, which is the output of the first solid-state laser device 200, and the sixth pulsed laser beam PL6, which is the output of the second solid-state laser device 210, into a fourth pulsed laser beam PL4 with a wavelength of approximately 193.4 nm by sum-frequency mixing twice (CLBO crystal 141, CLBO crystal 142).

[0115] As described above, the fourth pulsed laser beam PL4, which is the output of the solid-state seeder 21, is generated by the timing overlap of the fifth pulsed laser beam PL5 and the sixth pulsed laser beam PL6. Therefore, it can be said that the fourth pulsed laser beam PL4 is generated based on the overlap of trigger signal 1 and trigger signal 2.

[0116] In the operation during the laser operation described above, similar to the laser device 10, the laser control processor 50 receives the target center wavelength, target linewidth, target pulse energy, and emission trigger signal from the exposure control processor 61 of the exposure device 60, and sends the trigger A signal and charging voltage value to the excimer amplifier 30, and the trigger B signal, linewidth control signal, temperature value, and current value to the solid seeder 21 to operate the laser device 11 and control the pulsed laser light.

[0117] With the above configuration and operation, a pseudo-random signal with the same pattern is generated in synchronization with the trigger 2 signal, which is synchronized with the timing of the light emission trigger signal, and superimposed on the optical phase modulator 112. As a result, a modulated signal with the same waveform is superimposed on the optical phase modulator 112 for each pulse, and the spectrum of the superimposed signal is also the same for each pulse. Therefore, since the laser light output from the optical phase modulator 112 is modulated the same for each pulse, the spectrum is the same for each pulse, and the spectral linewidth is also the same for each pulse, resulting in stability.

[0118] Furthermore, with the above configuration and operation, the laser device 11 can output laser light with a broader, unimodal spectrum than the laser device 10, with an expanded spectral linewidth adjustment range.

[0119] 2.2.2 During adjustment This section describes a method for adjusting the timing of the spectral linewidth to output a broad, unimodal spectrum from the solid-state seeder 21.

[0120] Figure 9 shows a flowchart of the timing adjustment process. As shown in Figure 9, the timing adjustment process includes a first step and a second step that follows the first step.

[0121] 2.2.2.1 Step 1 The first step involves adjusting the timing of at least one of the trigger 1 signal and the trigger 2 signal to adjust the spectrum of the fourth pulsed laser light PL4 to a first non-Gaussian-shaped spectrum. Here, the first step involves searching for the trigger 1 signal start timing such that the spectrum of the fourth pulsed laser light PL4 becomes a first non-Gaussian-shaped spectrum by changing the start timing of the trigger 1 signal and measuring the spectrum of the fourth pulsed laser light PL4.

[0122] Figure 10 shows the flowchart of the first step. In step S21, the solid-state seeder control processor 160 stops the pseudo-random signal generator 150. The solid-state seeder control processor 160 also sets Delay2 to 0.

[0123] In step S22, the solid-state seeder control processor 160 determines whether Delay2 is less than (W1-W2). W1 is the width of the trigger 3 signal, and W2 is the width of the trigger 1 signal. If the determination result in step S22 is NO, that is, if Delay2 is not less than (W1-W2), the solid-state seeder control processor 160 proceeds to step S23.

[0124] In step S23, the solid-state seeder control processor 160 determines that there is an error (not adjustable) and terminates the timing adjustment process.

[0125] On the other hand, if the result of step S22 is a YES determination, that is, if Delay2 is less than (W1-W2), the solid-state seeder control processor 160 proceeds to step S24.

[0126] In step S24, the solid-state seeder control processor 160 measures the spectrum of the fourth pulsed laser light PL4. The spectrum of the fourth pulsed laser light PL4 may also be measured by the spectrum monitor 43. In this case, the spectrum monitor 43 measures the spectrum of the light amplified by the excimer amplifier 30 from the fourth pulsed laser light PL4. Alternatively, a beam splitter may be installed between the solid-state seeder 21 and the excimer amplifier 30 to monitor the spectrum of the fourth pulsed laser light PL4.

[0127] In step S25, the solid-state seeder control processor 160 determines whether the spectrum of the fourth pulsed laser light PL4 is a non-Gaussian waveform, which is a waveform with a non-Gaussian shape.

[0128] If the result of step S25 is NO, that is, if the spectrum is not a non-Gaussian waveform, the solid-state seeder control processor 160 proceeds to step S26. In step S26, the solid-state seeder control processor 160 adds a certain value to Delay2 and returns to step S22.

[0129] On the other hand, if the result of step S25 is a YES determination, that is, if the spectrum is a non-Gaussian waveform, the solid-state seeder control processor 160 proceeds to step S27. In step S27, the solid-state seeder control processor 160 determines whether the difference between the spectral linewidth of the fourth pulsed laser light PL4 and the predetermined target linewidth during adjustment is within an acceptable range.

[0130] If the result of step S27 is a NO judgment, that is, if the difference from the target line width during adjustment is not within the acceptable range, the solid-state seeder control processor 160 proceeds to step S26.

[0131] On the other hand, if the result of step S27 is a YES judgment, that is, if the difference from the target line width during adjustment is within the acceptable range, the solid-state seeder control processor 160 terminates the processing of this flowchart and determines the value of Delay2. Alternatively, the spectrum of the fourth pulsed laser light PL4 may be measured for all Delay2 values, and the most appropriate Delay2 may be selected.

[0132] Figure 11 shows the timing chart in the first step. As shown in Figures 10 and 11, in the first step, the solid-state seeder control processor 160 stops the pseudo-random signal generator 150 and changes Delay2 with the second solid-state laser device 210 without optical phase modulation to adjust the fourth pulsed laser beam PL4 to a first spectrum with a spectral linewidth wider than Gaussian shape.

[0133] FIG. 12 shows the spectrum of the fourth pulsed laser beam PL4 in the adjustment of the first step. The waveforms A, B, and C shown in FIG. 12 have Delay2 values of 9 nsec, 11 nsec, and 13 nsec respectively, Gain values of 0.8 V respectively, and E95 widths of 0.08 pm, 0.16 pm, and 0.23 pm respectively. When Delay2 is changed, as shown in FIG. 12, the spectrum of the fourth pulsed laser beam PL4 changes from a narrow Gaussian shape (single-peakedness) to a spectrum with a wider spectral linewidth than the Gaussian shape, and further to a multi-peaked spectrum.

[0134] In the first step, select Delay2 that results in a wide spectrum, such as waveforms B and C shown in FIG. 12. If Delay2 that results in a narrow single-peaked spectrum like waveform A shown in FIG. 12 is selected in the first step, it will be difficult to obtain a wide spectrum when phase modulation is applied by a pseudo-random signal in the second step.

[0135] Note that the determination of whether the fourth pulsed laser beam PL4 in step S25 of FIG. 10 has a non-Gaussian waveform is performed by fitting the measured spectrum to a Gaussian waveform using the least squares method and using the magnitude of the coefficient of determination R 2 For example, when R 2 <0.9, it is determined that the waveform is non-Gaussian.

[0136] FIG. 13 shows an example of the determination of a non-Gaussian waveform. F13A and F13B in FIG. 13 each include a graph showing the measured spectrum and the Gaussian fit waveform. The spectrum of F13A in FIG. 13 has R 2 = 0.9876 and does not satisfy R 2 <0.9. Therefore, the spectrum of F13A is determined to be a Gaussian waveform.

[0137] On the other hand, the spectrum of F13B in FIG. 13 has R 2 = 0.7411 and satisfies R 2 <0.9. Therefore, the spectrum of F13B is determined to be a non-Gaussian waveform.

[0138] Furthermore, in the first step, the spectrum is adjusted by changing Delay2 within the range of 0 to (W1-W2). If Delay2 is negative or greater than W1-W2, the time width of the fifth pulsed laser beam PL5, which is the output of the first solid-state laser device 200, becomes shorter than W2. Moreover, care must be taken because if Delay2 is shifted so much that there is no temporal overlap between the trigger 3 signal and the trigger 1 signal, the fifth pulsed laser beam PL5, and consequently the fourth pulsed laser beam PL4, which is the output of the solid-state seeder 21, will disappear.

[0139] Similarly, care must be taken to set Delay3 and W3 so that the Trigger 1 signal and the Trigger 2 signal overlap.

[0140] By adjusting the timing based on the above, the fourth pulsed laser beam PL4 is output from the solid-state seeder 21 in accordance with the timing of the trigger 1 signal.

[0141] The length of Delay1 + Delay2, which determines the timing of the Trigger 1 signal, needs to be adjusted to match the optical amplification timing of the excimer amplifier 30. For this reason, the first step may involve adjusting Delay2, then changing the timing of the Trigger 1 signal with Delay1, so that the output pulse laser light of the solid-state seeder 21 coincides with the amplification timing of the excimer amplifier 30. In this case, Delay3 may also be changed in accordance with the change in Delay1 so that the relative timing difference between the Trigger 3 signal and the Trigger 2 signal remains unchanged.

[0142] Alternatively, in the first step, Delay1 and Delay3 may be fixed, and after adjusting Delay2, the time difference between trigger A signal and trigger B signal may be adjusted to achieve the appropriate amplification timing.

[0143] 2.2.2.2 Second Step The second step involves having the pseudo-random signal generator 150 generate a modulated signal of the same pattern synchronized with the light emission trigger signal, and then supplying this modulated signal to the optical phase modulator 112. This modulates the wavelength of the second continuous light within a time equivalent to one pulse of the third pulsed laser light PL3, thereby adjusting the spectrum of the fourth pulsed laser light PL4 to a second spectrum with a wider spectral linewidth than the first spectrum. In this second step, the pseudo-random signal generator 150 is operated, the spectrum of the fourth pulsed laser light PL4 is observed, and the initial value of the shift register 151 of the pseudo-random signal generator 150 is changed and searched for so that the spectrum of the fourth pulsed laser light PL4 becomes a unimodal and broad second spectrum.

[0144] Figure 14 shows a flowchart of the second step. In step S31, the solid-state seeder control processor 160 operates the pseudo-random signal generator 150.

[0145] In step S32, the solid-state seeder control processor 160 measures the spectrum of the fourth pulsed laser light PL4.

[0146] In step S33, the solid-state seeder control processor 160 determines whether the spectrum of the fourth pulsed laser light PL4 is unimodal.

[0147] If the result of step S33 is NO, that is, if the spectrum is not unimodal, the solid-state seeder control processor 160 proceeds to step S34. In step S34, the solid-state seeder control processor 160 updates the initial value of the shift register 151 and returns to step S32.

[0148] On the other hand, if the result of step S33 is a YES determination, that is, if the spectrum is unimodal, the solid-state seeder control processor 160 proceeds to step S35. In step S35, the solid-state seeder control processor 160 determines whether the difference between the spectral linewidth of the fourth pulsed laser light PL4 and the target linewidth of the unimodal spectrum is within an acceptable range.

[0149] If the result of step S35 is a NO judgment, that is, if the difference from the target line width for unimodal lines is not within the acceptable range, the solid-state seeder control processor 160 proceeds to step S34.

[0150] On the other hand, if the result of step S35 is a YES determination, that is, if the difference from the target linewidth for unimodal propagation is within the acceptable range, the solid-state seeder control processor 160 terminates the processing of this flowchart and determines the initial value of the shift register 151. Alternatively, the spectrum may be evaluated for all initial values ​​of the shift register 151, and the most appropriate initial value may be selected.

[0151] Figure 15 shows the spectrum of the fourth pulsed laser beam PL4 after the search in the second step. Waveforms A, B, and C in Figure 15 are the spectra of the fourth pulsed laser beam PL4 after determining the initial values ​​of the shift register 151 for waveforms A, B, and C in Figure 12, respectively. Waveforms A, B, and C in Figure 15 have E95 widths of 0.24 pm, 0.32 pm, and 0.4 pm, respectively. If a broad, multimodal spectrum like waveform C in Figure 12 is selected during the adjustment of Delay2, a broad, unimodal spectrum like waveform C in Figure 15 is obtained. In contrast, if a narrow, unimodal spectrum like waveform A in Figure 12 is selected, a narrow, unimodal spectrum like waveform A in Figure 15 is obtained.

[0152] 2.3 Action and Effects In the comparative example laser device 10, with the pseudo-random signal generator 150 stopped and the second solid-state laser device 110 without optical phase modulation, the output pulsed laser light of the solid-state seeder 20 corresponds to waveform A in Figure 12. This is because the ultimate goal is to make the output pulsed laser light of the solid-state seeder 20 unimodal (Gaussian shape). Therefore, if the spectrum is unimodal (Gaussian shape) even without phase modulation, it becomes easier to operate the pseudo-random signal generator 150 afterward and search by changing the initial value of the shift register 151 of the pseudo-random signal generator 150 so that the spectrum becomes unimodal (waveform A in Figure 15). Thus, the spectrum of the pulsed laser light output from the solid-state amplifier 102 of the comparative example laser device 10 was designed and manufactured to be Gaussian shaped (waveform A in Figure 12). Furthermore, because the solid-state amplifier 102 used pulsed laser light with a wavelength of 1030 nm, which could not be wavelength-converted by the LBO crystal, as the pump light, it was difficult to adjust the amplification timing of the solid-state amplifier 102, which corresponds to the adjustment of Delay 2 in Embodiment 1.

[0153] On the other hand, in the first step, the laser device 11 according to Embodiment 1 stops the pseudo-random signal generator 150 and adjusts Delay2 without applying optical phase modulation to the second solid-state laser device 210. This temporarily results in a spectrum with a wider spectral linewidth than a Gaussian shape, which is not a Gaussian shape, as shown in waveform B or waveform C in Figure 12. Subsequently, in the second step, the laser device 11 is set to a state where optical phase modulation is applied and the initial value of the shift register 151 of the pseudo-random signal generator 150 is changed and searched for. This shapes the spectrum, and a broad and unimodal spectrum, as shown in waveform B or waveform C in Figure 15, can be obtained. In particular, by temporarily adjusting to a multimodal spectrum, as shown in waveform C in Figure 12, an even broader spectrum can be ultimately obtained, as shown in waveform C in Figure 15.

[0154] 3. Embodiment 2 3.1 Configuration The configuration of the laser device according to Embodiment 2 is the same as that of the laser device according to Embodiment 1. The laser device 11 according to Embodiment 2 differs from the laser device 11 according to Embodiment 1 in that the control performed by the solid-state seeder control processor 160 is different.

[0155] 3.2 Operation The first step of Embodiment 2 involves adjusting the timing of at least one of the trigger 1 signal and the trigger 2 signal, as well as adjusting the gain of the solid-state amplifier 204, to adjust the spectrum of the fourth pulsed laser light PL4 to a first non-Gaussian-shaped spectrum. Here, in addition to adjusting Delay 2, the gain is further adjusted to obtain a broad, unimodal spectrum. The second step of Embodiment 2 is the same as in Embodiment 1.

[0156] Figure 16 shows a flowchart of the first step of Embodiment 2. In step S41, the solid-state seeder control processor 160 stops the pseudo-random signal generator 150. The solid-state seeder control processor 160 also sets Delay2 to 0 and Gain to the minimum value.

[0157] The processing in steps S22 to S25 and step S27 is the same as in Figure 10. If the result of the determination in step S25 is YES and the result of the determination in step S27 is YES, the solid-state seeder control processor 160 terminates the processing in this flowchart and determines the values ​​of Delay2 and Gain.

[0158] On the other hand, if the result of the determination in step S25 is NO, or if the result of the determination in step S27 is NO, the solid-state seeder control processor 160 proceeds to step S42. In step S42, the solid-state seeder control processor 160 determines whether or not the Gain is less than the maximum value.

[0159] If the result of step S42 is NO, that is, if Gain is not less than the maximum value, the solid-state seeder control processor 160 proceeds to step S43. In step S43, the solid-state seeder control processor 160 sets Gain to the minimum value. Then, in step S26, the solid-state seeder control processor 160 adds a certain value to Delay2 and returns to step S22.

[0160] On the other hand, if the result of step S42 is a YES determination, that is, if the Gain is less than the maximum value, the solid-state seeder control processor 160 proceeds to step S44. In step S44, the solid-state seeder control processor 160 measures the spectrum of the fourth pulsed laser light PL4.

[0161] In step S45, the solid-state seeder control processor 160 determines whether the spectrum of the fourth pulsed laser light PL4 is a non-Gaussian waveform. This determination may be performed in the same manner as in step S25.

[0162] If the result of step S45 is NO, that is, if the spectrum is not a non-Gaussian waveform, the solid-state seeder control processor 160 proceeds to step S46. In step S46, the solid-state seeder control processor 160 increases the Gain by a certain amount and returns to step S42.

[0163] On the other hand, if the result of step S45 is a YES determination, that is, if the spectrum is a non-Gaussian waveform, the solid-state seeder control processor 160 proceeds to step S47. In step S47, the solid-state seeder control processor 160 determines whether the difference between the spectral linewidth of the fourth pulsed laser light PL4 and the target linewidth during adjustment is within an acceptable range.

[0164] If the result of step S47 is NO, that is, if the difference from the target line width during adjustment is not within the acceptable range, the solid-state seeder control processor 160 proceeds to step S46. On the other hand, if the result of step S47 is YES, that is, if the difference from the target line width during adjustment is within the acceptable range, the solid-state seeder control processor 160 terminates the processing of this flowchart and determines the values ​​of Delay2 and Gain.

[0165] In the first step of Embodiment 2, if the desired multimodal spectrum can be obtained by adjusting only Delay2, the Gain adjustment may not be necessary, as in Embodiment 1. On the other hand, if the desired multimodal spectrum cannot be obtained by adjusting only Delay2, the Gain adjustment should be performed. Alternatively, the Gain may be adjusted first, and if the desired multimodal spectrum cannot be obtained, Delay2 may be adjusted.

[0166] You could examine the spectra for all combinations of Delay2 and Gain and choose the best one.

[0167] 3.3 Action and Effects Figure 17 shows the spectrum of the fourth pulsed laser beam PL4 during the adjustment of the first step. Waveforms A, B, and C shown in Figure 17 have a Delay2 of 9 nsec, 11 nsec, and 13 nsec, respectively, a Gain of 0.8 V, 1.1 V, and 1.4 V, respectively, and an E95 width of 0.08 pm, 0.19 pm, and 0.3 pm, respectively.

[0168] Figure 18 shows the spectrum of the fourth pulsed laser beam PL4 after the search in the second step. Waveforms A, B, and C in Figure 18 are the spectra of the fourth pulsed laser beam PL4 after determining the initial values ​​of the shift register 151, respectively, for waveforms A, B, and C in Figure 17. Waveforms A, B, and C shown in Figure 18 have E95 widths of 0.24 pm, 0.37 pm, and 0.5 pm, respectively.

[0169] As shown in Figures 17 and 18, a wider spectrum can be obtained by combining the adjustment of Delay2 and the adjustment of Gain.

[0170] 4. Embodiment 3 4.1 Configuration The configuration of the laser device according to Embodiment 3 is the same as that of the laser device according to Embodiment 1. The laser device 11 according to Embodiment 3 differs from the laser device 11 according to Embodiment 1 in that the control performed by the solid-state seeder control processor 160 is different.

[0171] 4.2 Operation The first step of Embodiment 3 is to change the Delay3, which is the start timing of the trigger 2 signal, and measure the spectrum of the fourth pulsed laser light PL4 to search for the start timing of the trigger 2 signal such that the spectrum of the fourth pulsed laser light PL4 becomes a first spectrum with a non-Gaussian shape. The second step of Embodiment 3 is the same as in Embodiment 1.

[0172] Figure 19 shows a flowchart of the first step of Embodiment 3. In step S61, the solid-state seeder control processor 160 stops the pseudo-random signal generator 150. The solid-state seeder control processor 160 also sets Delay3 to (Delay1 + Delay2 + W2 - W3).

[0173] In step S62, the solid-state seeder control processor 160 determines whether Delay3 is less than (Delay1 + Delay2). If the result of the determination in step S62 is NO, that is, if Delay3 is not less than (Delay1 + Delay2), the solid-state seeder control processor 160 proceeds to step S23. The processing in step S23 is the same as step S23 in Figure 10.

[0174] On the other hand, if the result of step S62 is a YES determination, that is, if Delay3 is less than (Delay1 + Delay2), the solid-state seeder control processor 160 proceeds to step S24.

[0175] The processes in steps S24, S25, and S27 are the same as those in steps S24, S25, and S27 of Figure 10. If the result of the determination in step S25 is YES and the result of the determination in step S27 is YES, the solid-state seeder control processor 160 terminates the process in this flowchart and determines the value of Delay3.

[0176] On the other hand, if the result of the determination in step S25 is NO, or if the result of the determination in step S27 is NO, the solid-state seeder control processor 160 proceeds to step S63. In step S63, the solid-state seeder control processor 160 adds a certain value to Delay3 and returns to step S62.

[0177] In this way, by adjusting Delay3, the difference in pulse extraction timing between the first solid-state laser device 200 and the second solid-state laser device 210 is adjusted, and the spectrum of the fourth pulsed laser light PL4 is adjusted to be broad and multi-peaked. Alternatively, the spectrum of the fourth pulsed laser light PL4 may be measured for all Delay3 settings, and the most appropriate Delay3 may be selected.

[0178] When adjusting Delay3, it is important to set Delay3 and W3 so that there is an overlap between the Trigger 1 signal and the Trigger 2 signal. Specifically, set Delay3 and W3 so that the following equation 1 is satisfied. Delay1+ Delay2+W2-W3< Delay3< Delay1+ Delay2 …(Formula 1)

[0179] Furthermore, the adjustment of Delay3 in the first step of Embodiment 3 may be performed in combination with the adjustment of Delay1 in Embodiment 1, in combination with the adjustment of Gain in Embodiment 2, or in combination with the adjustment of both Delay1 and Gain in Embodiment 2.

[0180] 4.3 Action and Effects Figure 20 shows the spectrum of the fourth pulsed laser beam PL4 during the adjustment of the first step. Waveforms A, B, and C shown in Figure 20 have a Delay 2 of 9 nsec, a Delay 3 of 9962 ns, 9963 ns, and 9964 ns, respectively, a Gain of 0.8 V, and E95 widths of 0.08 pm, 0.20 pm, and 0.33 pm, respectively.

[0181] Figure 21 shows the spectrum of the fourth pulsed laser beam PL4 after the search in the second step. Waveforms A, B, and C in Figure 21 are the spectra of the fourth pulsed laser beam PL4 after determining the initial values ​​of the shift register 151 for waveforms A, B, and C in Figure 20, respectively. Waveforms A, B, and C in Figure 21 have E95 widths of 0.24 pm, 0.40 pm, and 0.55 pm, respectively.

[0182] As shown in Figures 20 and 21, adjusting Delay3 yields a wider spectrum.

[0183] Processors such as the laser control processor 50 and the exposure control processor 61 may be physically configured in hardware form to perform the various processes included in this disclosure. For example, the processor may be a computer including a memory storing control programs that define the various processes, and a processing unit that executes the control programs. The control programs may be stored in a single memory, or they may be divided and stored in multiple physically separate memories, and the various processes may be defined by the control program as a collection of these memories. The processing unit may be a general-purpose processing unit such as a CPU, or a purpose-specific processing unit such as a GPU.

[0184] Furthermore, the processor may be programmed in software form to perform the various processes included in this disclosure. For example, the processor may have functions for performing the various processes implemented in a dedicated device such as an ASIC or a programmable device such as an FPGA.

[0185] The various processes included in this disclosure may be performed by one computer, one dedicated device, or one programmable device, or by the cooperation of multiple computers, multiple dedicated devices, or multiple programmable devices located physically separately. The various processes may be performed by at least two combinations of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0186] 5. Methods for manufacturing electronic devices Figure 22 schematically shows an example configuration of the exposure apparatus 60. The exposure apparatus 60 includes an illumination optical system 62 and a projection optical system 63. The laser device 11 generates laser light and outputs the laser light to the exposure apparatus 60. The illumination optical system 62 illuminates the reticle pattern of a reticle (not shown) placed on the reticle stage RT with the laser light incident from the laser device 11. The projection optical system 63 reduces and projects the laser light that has passed through the reticle onto a workpiece (not shown) placed on the workpiece table WT, forming an image. The workpiece is a photosensitive substrate such as a semiconductor wafer coated with photoresist.

[0187] The exposure apparatus 60 exposes the workpiece to a laser beam reflecting the reticle pattern by synchronously moving the reticle stage RT and the workpiece table WT in parallel. After transferring the reticle pattern to the semiconductor wafer through the exposure process described above, a semiconductor device can be manufactured by going through several processes. The semiconductor device is an example of an "electronic device" in this disclosure.

[0188] 6. Others The above description is intended to be illustrative and not restrictive. It will therefore be apparent to those skilled in the art that modifications can be made to the embodiments of this disclosure without departing from the claims. It will also be apparent to those skilled in the art that the embodiments of this disclosure can be used in combination.

[0189] Terms used in this specification and throughout the claims should be interpreted as "non-limiting" unless otherwise specified. For example, terms such as "includes," "have," "equip," and "possess" should be interpreted as "not excluding the existence of components other than those described." Also, the modifier "one" should be interpreted as "at least one" or "one or more." Furthermore, the term "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." In addition, it should be interpreted as including combinations of these with anything other than "A," "B," and "C."

Claims

1. A first semiconductor laser that emits a first continuous beam of light, A first amplifier that, in synchronization with a light emission trigger signal received from an external device, amplifies a portion of the first continuous light and converts it into a first pulsed laser light, A second amplifier that amplifies a portion of the first pulsed laser light and converts it into a second pulsed laser light using a first trigger signal generated in synchronization with the light emission trigger signal, A second semiconductor laser that emits a second continuous beam of light, A third amplifier that amplifies a portion of the second continuous light and converts it into a third pulsed laser light using a second trigger signal generated in synchronization with the aforementioned light emission trigger signal, An optical phase modulator is positioned in the optical path of the second continuous light between the second semiconductor laser and the third amplifier, A modulation signal generator that outputs a modulation signal to be supplied to the optical phase modulator, A wavelength conversion system that combines the second pulsed laser beam and the third pulsed laser beam using sum-frequency mixing to convert the wavelength and outputs a fourth pulsed laser beam, A method for adjusting the spectral linewidth of pulsed laser light output by a laser device equipped with the following: A first step of adjusting at least one of the timing of the first trigger signal and the timing of the second trigger signal to adjust the spectrum of the fourth pulsed laser light to a first spectrum with a non-Gaussian shape, A second step involves causing the modulation signal generator to generate the modulation signal of the same pattern synchronized with the light emission trigger signal, and supplying the modulation signal of the same pattern to the optical phase modulator, thereby modulating the wavelength of the second continuous light within a time corresponding to one pulse of the third pulsed laser light, and adjusting the spectrum of the fourth pulsed laser light to a second spectrum having a wider spectral linewidth than the first spectrum. A method for adjusting spectral linewidths, including [specific parameters].

2. A method for adjusting spectral linewidth according to claim 1, The system further comprises a fourth amplifier that amplifies the second pulsed laser light and converts it into a fifth pulsed laser light, The wavelength conversion system converts the wavelength by sum-frequency mixing the fifth pulsed laser light and the third pulsed laser light, and outputs the fourth pulsed laser light. The first step involves adjusting the timing of at least one of the first trigger signal and the second trigger signal, adjusting the amplification gain of the fourth amplifier, and adjusting the spectrum of the fourth pulsed laser light to the first spectrum which has a non-Gaussian shape. How to adjust spectral linewidth.

3. A method for adjusting spectral linewidth according to claim 1, The modulated signal is a pseudo-random signal. How to adjust spectral linewidth.

4. A method for adjusting spectral linewidth according to claim 3, The modulated signal generator includes a shift register, How to adjust spectral linewidth.

5. A method for adjusting spectral linewidth according to claim 4, The aforementioned modulation signal generator includes an initial value setting circuit, The second step is to set the initial value of the shift register such that the second spectrum is unimodal. How to adjust spectral linewidth.

6. A method for adjusting spectral linewidth according to claim 1, The first spectrum is multimodal, and the second spectrum is unimodal. How to adjust spectral linewidth.

7. A method for adjusting spectral linewidth according to claim 1, The device further comprises a wavelength conversion crystal that converts the wavelength of the third pulsed laser light into a sixth pulsed laser light, The wavelength conversion system converts the wavelength by sum-frequency mixing the second pulsed laser light and the sixth pulsed laser light, and outputs the fourth pulsed laser light. How to adjust spectral linewidth.

8. A method for adjusting spectral linewidth according to claim 1, The wavelength of the fourth pulsed laser light is 193 nm. How to adjust spectral linewidth.

9. A method for adjusting spectral linewidth according to claim 1, In the first step described above, the modulation signal generated by the modulation signal generator is not output. How to adjust spectral linewidth.

10. A method for adjusting spectral linewidth according to claim 1, In the first step, the timing of the first trigger signal is adjusted. How to adjust spectral linewidth.

11. A method for adjusting spectral linewidth according to claim 10, In the first step, the start timing of the first trigger signal is changed and the spectrum of the fourth pulsed laser light is measured to search for the start timing of the first trigger signal such that the spectrum of the fourth pulsed laser light becomes the first spectrum which has a non-Gaussian shape. How to adjust spectral linewidth.

12. A method for adjusting spectral linewidth according to claim 10, In the first step, the spectrum of the fourth pulsed laser light is measured for all start timings of the first trigger signal. How to adjust spectral linewidth.

13. A method for adjusting spectral linewidth according to claim 11, In the first step, the spectrum of the measured fourth pulsed laser light is fitted with a Gaussian waveform using the least squares method to determine whether or not the spectrum of the fourth pulsed laser light has a non-Gaussian shape. How to adjust spectral linewidth.

14. A method for adjusting spectral linewidth according to claim 11, In the first step, among the start timings of the first trigger signal that result in the spectrum of the fourth pulsed laser light being a non-Gaussian-shaped first spectrum, the start timing of the first trigger signal is selected such that the difference between a predetermined target linewidth and the spectral linewidth of the fourth pulsed laser light is within an acceptable range. How to adjust spectral linewidth.

15. A method for adjusting spectral linewidth according to claim 1, In the first step, the timing of the second trigger signal is adjusted. How to adjust spectral linewidth.

16. A method for adjusting spectral linewidth according to claim 15, In the first step, the start timing of the second trigger signal is changed and the spectrum of the fourth pulsed laser light is measured to search for the start timing of the second trigger signal such that the spectrum of the fourth pulsed laser light becomes the first spectrum which has a non-Gaussian shape. How to adjust spectral linewidth.

17. A method for adjusting spectral linewidth according to claim 16, In the first step, the spectrum of the fourth pulsed laser light is measured for all start timings of the second trigger signal. How to adjust spectral linewidth.

18. A method for adjusting spectral linewidth according to claim 16, In the first step, the spectrum of the measured fourth pulsed laser light is fitted with a Gaussian waveform using the least squares method to determine whether or not the spectrum of the fourth pulsed laser light has a non-Gaussian shape. How to adjust spectral linewidth.

19. A method for adjusting spectral linewidth according to claim 16, In the first step, among the start timings of the second trigger signal that result in the spectrum of the fourth pulsed laser light having a non-Gaussian shape, the start timing of the second trigger signal is selected such that the difference between a predetermined target linewidth and the spectral linewidth of the fourth pulsed laser light is within an acceptable range. How to adjust spectral linewidth.

20. A method for manufacturing electronic devices, A first semiconductor laser that emits a first continuous beam of light, A first amplifier that, in synchronization with a light emission trigger signal received from an external device, amplifies a portion of the first continuous light and converts it into a first pulsed laser light, A second amplifier that amplifies a portion of the first pulsed laser light and converts it into a second pulsed laser light using a first trigger signal generated in synchronization with the light emission trigger signal, A second semiconductor laser that emits a second continuous beam of light, A third amplifier that amplifies a portion of the second continuous light and converts it into a third pulsed laser light using a second trigger signal generated in synchronization with the aforementioned light emission trigger signal, An optical phase modulator is positioned in the optical path of the second continuous light between the second semiconductor laser and the third amplifier, A modulation signal generator that outputs a modulation signal to be supplied to the optical phase modulator, A wavelength conversion system that combines the second pulsed laser beam and the third pulsed laser beam using sum-frequency mixing to convert the wavelength and outputs a fourth pulsed laser beam, Equipped with, The timing of the first trigger signal and the timing of the second trigger signal are adjusted to adjust the spectrum of the fourth pulsed laser light to a first spectrum with a non-Gaussian shape. The fourth pulsed laser light is generated by a laser device that causes the modulation signal generator to generate the modulation signal of the same pattern synchronized with the light emission trigger signal, and provides the modulation signal of the same pattern to the optical phase modulator, thereby modulating the wavelength of the second continuous light within a time corresponding to one pulse of the third pulsed laser light, and adjusting the spectrum of the fourth pulsed laser light to a second spectrum having a wider spectral linewidth than the first spectrum. The fourth pulsed laser beam is output to the exposure apparatus, To manufacture an electronic device, the process includes exposing a photosensitive substrate with the fourth pulsed laser light in the exposure apparatus, A method for manufacturing electronic devices.

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