Patent Application
20250180933
The present disclosure relates to a laser device and an electronic device manufacturing method.
Recently, in a semiconductor exposure apparatus, improvement in resolution has been desired for miniaturization and high integration of semiconductor integrated circuits. For this purpose, an exposure light source that outputs light having a shorter wavelength has been developed. For example, as a gas laser device for exposure, a KrF excimer laser device for outputting laser light having a wavelength of about 248 nm and an ArF excimer laser device for outputting laser light having a wavelength of about 193 nm are used.
The KrF excimer laser device and the ArF excimer laser device each have a large spectral line width of about 350 to 400 pm in natural oscillation light. Therefore, when a projection lens is formed of a material that transmits ultraviolet rays such as KrF laser light and ArF laser light, there is a case in which chromatic aberration occurs. As a result, the resolution may decrease. Then, a spectral line width of laser light output from the gas laser device needs to be narrowed to the extent that the chromatic aberration can be ignored. For this purpose, there is a case in which a line narrowing module (LNM) including a line narrowing element (etalon, grating, and the like) is provided in a laser resonator of the gas laser device to narrow a spectral line width. In the following, a gas laser device with a narrowed spectral line width is referred to as a line narrowing gas laser device.
A laser device according to an aspect of the present disclosure includes a semiconductor laser configured to output continuous light, a first amplifier configured to amplify the continuous light and convert the continuous light to pulse light in synchronization with a light emission trigger signal received from an external apparatus, an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator configured to output a modulation signal to be provided to the optical phase modulator, and a processor configured to control the modulation signal generator. Here, the processor causes the modulation signal generator to generate the modulation signal having an identical pattern in synchronization with the light emission trigger signal and provide the modulation signal having the identical pattern to the optical phase modulator so as to modulate a wavelength of the continuous light within a time period corresponding to one pulse of the pulse light and adjust a spectral line width of the pulse light.
An electronic device manufacturing method according to another aspect of the present disclosure includes generating laser light having an ultraviolet wavelength using a laser device, outputting the laser light to an exposure apparatus, and exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device. Here, the laser device includes a semiconductor laser configured to output continuous light, a first amplifier configured to amplify the continuous light and convert the continuous light to pulse light in synchronization with a light emission trigger signal received from an external apparatus, an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator configured to output a modulation signal to be provided to the optical phase modulator, a processor configured to control the modulation signal generator, and a wavelength conversion system configured to output second pulse laser light as converting a wavelength of first pulse laser light output from the first amplifier. The processor causes the modulation signal generator to generate the modulation signal having an identical pattern in synchronization with the light emission trigger signal and provide the modulation signal having the identical pattern to the optical phase modulator so as to modulate a wavelength of the continuous light within a time period corresponding to one pulse of the pulse light and adjust a spectral line width of the pulse light.
A laser device according to another aspect of the present disclosure includes a semiconductor laser configured to output continuous light, a first amplifier configured to amplify the continuous light and convert the continuous light to pulse light in synchronization with a light emission trigger signal received from an external apparatus, an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator configured to output a modulation signal to be provided to the optical phase modulator, and a processor configured to control the modulation signal generator. Here, the processor causes the modulation signal generator to generate the modulation signal having an identical pattern in synchronization with the light emission trigger signal and provide the modulation signal having the identical pattern to the optical phase modulator so as to modulate a wavelength of the continuous light within a time period corresponding to one pulse of the pulse light, and to adjust a power of the modulation signal so as to adjust a spectral line width of the pulse light.
An electronic device manufacturing method according to another aspect of the present disclosure includes generating laser light having an ultraviolet wavelength using a laser device, outputting the laser light to an exposure apparatus, and exposing a photosensitive substrate to the laser light in the exposure apparatus to manufacture an electronic device. Here, the laser device includes a semiconductor laser configured to output continuous light, a first amplifier configured to amplify the continuous light and convert the continuous light to pulse light in synchronization with a light emission trigger signal received from an external apparatus, an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator configured to output a modulation signal to be provided to the optical phase modulator, and a processor configured to control the modulation signal generator. Here, the processor causes the modulation signal generator to generate the modulation signal having an identical pattern in synchronization with the light emission trigger signal and provide the modulation signal having the identical pattern to the optical phase modulator so as to modulate a wavelength of the continuous light within a time period corresponding to one pulse of the pulse light, and to adjust a power of the modulation signal so as to adjust a spectral line width of the pulse light.
Embodiments of the present disclosure will be described below merely as examples with reference to the accompanying drawings.
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the contents of the present disclosure. Also, all configurations and operation described in the embodiments are not necessarily essential as configurations and operation of the present disclosure. Here, the same components are denoted by the same reference numeral, and duplicate description thereof is omitted.
The laser device 10 includes a solid-state seeder 20 as a master oscillator (MO), an excimer amplifier 30 as a power amplifier (PA), a monitor module 40, an outlet port shutter 46, and a laser control processor 50.
The solid-state seeder 20 includes a semiconductor laser system 100 for outputting continuous wave (CW) light, an optical phase modulator 104, a solid-state amplifier 106, a wavelength conversion system 108, a white noise generator 110, and a solid-state seeder control processor 112.
The semiconductor laser system 100 includes a distributed feedback (DFB) type semiconductor laser that outputs CW laser light having a wavelength of about 773.6 nm. The semiconductor laser system 100 has a configuration in which the oscillation wavelength can be changed by controlling a temperature value of a semiconductor laser and/or a current value flowing through an element of the semiconductor laser.
The optical phase modulator 104 modulates the phase of CW light output from the semiconductor laser system 100. The white noise generator 110 superimposes a modulation signal on the optical phase modulator 104.
The solid-state amplifier 106 converts output light of the optical phase modulator 104 to pulse light and amplifies the pulse light. The solid-state amplifier 106 includes a semiconductor optical amplifier (SOA), a titanium sapphire crystal, and a pumping pulse laser. By supplying pulse current to the SOA, the SOA pulse-amplifies the CW light output from the optical phase modulator 104, and outputs pulse-amplified pulse laser light. The titanium sapphire crystal is arranged on the optical path of the pulse laser light pulse-amplified by the SOA. The pumping pulse laser is a laser device for outputting second harmonic light of a YLF laser. Yttrium lithium fluoride (YLF) is a solid-state laser crystal represented by the chemical formula LiYF4. The solid-state amplifier 106 may include a fiber amplifier instead of or in combination with the amplifier using the titanium sapphire crystal.
The wavelength conversion system 108 includes a nonlinear crystal, performs wavelength conversion on the incident pulse laser light to cause second harmonic generation twice, and generates pulse light having an optical frequency four times that of the incident pulse laser light. The wavelength conversion system 108 includes, for example, an LBO crystal and a KBBF crystal. “LBO” is represented by the chemical formula LiB3O5. “KBBF” is represented by the chemical formula KBe2BO3F2. The wavelength conversion system 108 converts the wavelength of pulse laser light PL1 output from the solid-state amplifier 106 and outputs pulse laser light PL2 having a wavelength of about 193.4 nm.
The solid-state seeder control processor 112 controls the wavelength, power, pulse waveform, spectral line width, and the like of the laser light output from the solid-state seeder 20. The solid-state seeder control processor 112 controls the semiconductor laser system 100, the solid-state amplifier 106, the wavelength conversion system 108, and the white noise generator 110 based on input from the laser control processor 50. The processor in the present specification is a processing device including a storage device in which a control program is stored and a central processing unit (CPU) that executes the control program. The processor is specifically configured or programmed to perform various processes included in the present disclosure.
The excimer amplifier 30 includes a chamber 120, a pulse power module (PPM) 122, a charger 124, a convex mirror 126, and a concave mirror 127. The chamber 120 includes windows 134a, 134b, a pair of electrodes 135a, 135b, and an electrically insulating member 136. An ArF laser gas is supplied into the chamber 120 from a gas supply device (not shown). The ArF laser gas includes an Ar gas, an F2 gas, and an Ne gas.
The PPM 122 includes a switch 123 and a charging capacitor (not shown). The charger 124 holds electric energy to be supplied to the PPM 122. The charger 124 is connected to the charging capacitor (not shown). The charger 124 charges the charge capacitor of the PPM 122 in accordance with a command from the laser control processor 50.
The PPM 122 is connected to the electrode 135b in the chamber 120 via a feedthrough in the electrically insulating member 136. The electrode 135a is connected to the ground potential.
The windows 134a, 134b are arranged such that the pulse laser light amplified by discharge excitation between the electrodes 135a, 135b passes therethrough.
The convex mirror 126 and the concave mirror 127 are arranged such that the pulse laser light PL2 output from the wavelength conversion system 108 passes through the discharge space between the electrodes 135a, 135b three times and the beam thereof is expanded.
The monitor module 40 includes beam splitters 142, 143, a spectrum monitor 146, and an optical sensor 148. The beam splitter 142 is arranged, on the optical path of pulse laser light PL3 output from the excimer amplifier 30, such that the pulse laser light PL3 reflected by the beam splitter 142 is incident on the beam splitter 143. Here, the beam splitter 142 may be arranged outside the monitor module 40.
The beam splitter 143 is arranged such that the pulse laser light PL3 reflected by the beam splitter 143 enters the spectrum monitor 146 and the pulse laser light PL3 transmitted through the beam splitter 143 enters the optical sensor 148.
The spectrum monitor 146 monitors the spectrum of the entering pulse laser light PL3 and detects the oscillation wavelength of the entering pulse laser light PL3. The spectrum monitor 146 may be, for example, an etalon spectrometer. The etalon spectrometer includes a diffusion plate for diffusing sample light, an etalon, a light concentrating lens arranged on the output side of the etalon, and a photodiode array arranged on the focal plane of the light concentrating lens for detecting the pattern of interference fringes, and can detect the wavelength by measuring the diameter of the interference fringes.
The optical sensor 148 detects the pulse energy of the entering pulse laser light PL3. The optical sensor 148 may be, for example, a photodiode or the like.
The outlet port shutter 46 is arranged on the optical path of the pulse laser light PL3 output from the laser device 10 to the outside, and is configured to be capable of switching between outputting, to the outside, and blocking of the pulse laser light PL3. The pulse laser light PL3 transmitted through the beam splitter 142 is output from the laser device 10 via the outlet port shutter 46.
The laser device 10 is connected to the exposure apparatus 80 via a beam delivery unit (BDU) (not shown). The BDU is an optical system that transmits the pulse laser light PL3 from the laser device 10 to the exposure apparatus 80. The pulse laser light PL3 output from the laser device 10 enters the exposure apparatus 80.
The exposure apparatus 80 includes an exposure control processor 86. The exposure control processor 86 controls the exposure apparatus 80. Further, the exposure control processor 86 is connected to the laser control processor 50. The exposure apparatus 80 is an example of the “external apparatus” in the present disclosure.
The exposure control processor 86 transmits various parameters including a target wavelength, a target spectral line width, and a target pulse energy to the laser control processor 50. Further, the exposure control processor 86 transmits a light emission trigger signal Tr to the laser control processor 50. The laser control processor 50 controls the laser device 10 based on the various parameters and the light emission trigger signal Tr received from the exposure control processor 86. The laser control processor 50 outputs trigger signals Tr1, Tr2 synchronized with the light emission trigger signal Tr. The trigger signal Tr1 is input to the switch 123 of the PPM 122, and the trigger signal Tr2 is input to the solid-state amplifier 106.
The operation of the solid-state seeder 20 is as follows. CW laser light having a wavelength of about 773.6 nm is output from the semiconductor laser system 100. The CW laser light is phase-modulated by the optical phase modulator 104, and the optical spectrum thereof is changed in shape. The CW laser light having the shape-changed optical spectrum is pulse-amplified when a pulse current is supplied to the SOA in the solid-state amplifier 106 at the timing of the trigger signal Tr2, and is further amplified by the solid-state amplifier 106 including the fiber amplifier connected downstream of the SOA, and the pulse laser light PL1 having the shape-changed optical spectrum is output.
The amplified pulse laser light PL1 enters the wavelength conversion system 108 and is wavelength-converted to fourth harmonic light having a wavelength of about 193.4 nm.
The variable range of the wavelength of the pulse laser light PL2 output from the solid-state seeder 20 is about 193.2 nm to 193.5 nm, which is an amplification wavelength band of the excimer amplifier 30.
The trigger signal Tr1 is input to the switch 123 of the PPM 122 so that discharge occurs in synchronization with the pulse laser light PL2 output from the solid-state seeder 20 entering the discharge space of the chamber 120 of the excimer amplifier 30. Consequently, the pulse laser light PL2 output from the solid-state seeder 20 is three-pass amplified by the excimer amplifier 30.
The pulse laser light PL3 amplified by the excimer amplifier 30 is sampled by the beam splitter 142 and the beam splitter 143 of the monitor module 40, and the optical spectrum and the pulse energy are measured by the spectrum monitor 146 and the optical sensor 148.
From the measured optical spectrum of the pulse laser light PL3 output from the excimer amplifier 30, the laser control processor 50 transmits a control signal of the center wavelength to the solid-state seeder control processor 112 so that the center wavelength approaches the target wavelength which is the target value. The solid-state seeder 112 transmits command values of the control processor 1 temperature value and the current value to the semiconductor laser system 100 based on the control signal acquired from the laser control processor 50. The semiconductor laser system 100 changes the temperature and the current of the semiconductor laser of the semiconductor laser system 100 based on the command values of the temperature value and the current value acquired from the solid-state seeder control processor 112 to change the oscillation wavelength.
Further, from the measured optical spectrum of the pulse laser light PL3 output from the excimer amplifier 30, the laser control processor 50 transmits a control signal of the spectral line width to the solid-state seeder control processor 112 so that the spectral line width approaches the target spectral line width which is the target value. The solid-state seeder control processor 112 changes the signal bandwidth and power of the modulation signal output from the white noise generator 110 based on the control signal acquired from the laser control processor 50.
The optical phase modulator 104 changes the optical spectrum of the laser light output from the optical phase modulator 104 according to the signal bandwidth and power of the output from the white noise generator 110.
Further, the laser control processor 50 changes the charge voltage of the charger 124 so that the measured pulse energy of the pulse laser light PL3 output from the excimer amplifier 30 approaches the target pulse energy which is the target value.
The optical spectrum of the semiconductor laser is very narrow, and the spectral line width required by the exposure apparatus 80 cannot be obtained even if wavelength conversion to deep ultraviolet (DUV) light is directly performed. Phase modulation of the output light of the semiconductor laser results in a band (spectral rise) due to modulation around the original spectrum. When the white noise is selected as the modulation signal, the phase-modulated optical spectrum may be a Gaussian-shaped spectrum corresponding to the signal bandwidth and the signal intensity of the white noise. By appropriately selecting the signal bandwidth and the signal intensity of the white noise, it is possible to set the optical spectral line width to the target width.
However, in the case of pulse light, it is found that, in the white noise generator 110, the spectrum distribution of the signal to be superimposed on the optical phase modulator 104 in a very short period of time, such as corresponding to the pulse width (e.g., about 30 nsec), is not the ideal Gaussian distribution, but has a multimodal complicated shape and differs in shape from pulse to pulse (see
The laser device 11 includes a solid-state seeder 21 instead of the solid-state seeder 20 of
The pseudo-random signal generator 111 is an example of the “modulation signal 1 generator” in the present disclosure. The solid-state amplifier 106 is an example of the “first amplifier” in the present disclosure, and the pulse laser light PL1 output from the solid-state amplifier 106 is an example of the “first pulse laser light” in the present disclosure. The pulse laser light PL2 output from the wavelength conversion system 108 is an example of the “second pulse laser light” in the present disclosure. The wavelength in the wavelength range of about 193.2 nm to 193.5 nm is an example of the “ultraviolet wavelength” in the present disclosure. The excimer amplifier 30 is an example of the “second amplifier” in the present disclosure.
The CW laser light having a wavelength of about 773.6 nm is output from the semiconductor laser of the solid-state seeder 21. The solid-state seeder control processor 112 transmits a reset signal for the shift register in the pseudo-random signal generator 111 and a timing signal same as the trigger signal Tr2 to the pseudo-random signal generator 111.
The pseudo-random signal generator 111 receives a reset signal from the solid-state seeder control processor 112 for the shift register, and generates a pseudo-random signal having an identical pattern in synchronization with the trigger signal Tr2 due to the timing signal of the trigger signal Tr2. In the pseudo-random signal, unnecessary spectral components of a high frequency component are removed by a subsequent variable bandpass filter.
The optical phase modulator 104 phase-modulates the CW laser light with the pseudo-random signal limited to an appropriate frequency band from the pseudo-random signal generator 111 to change the shape of the optical spectrum.
The optical spectral line width becomes wider when the cutoff frequency of the variable bandpass filter is changed to the high frequency side, and becomes narrower when the cutoff frequency of the variable bandpass filter is changed to the low frequency side. Further, the waveform and spectral shape of the pseudo-random signal are changed by changing the timing of entering the reset signal to the shift register in the pseudo-random signal generator 111 and the like, and the optical spectrum of the laser light output from the optical phase modulator 104 is also changed.
For controlling the spectral line width, the frequency of the pseudo-random signal is adjusted based on the measured spectral line width. Specifically, the cutoff frequency of the variable bandpass filter is adjusted.
When the determination result of step S12 is YES, the laser control processor 50 returns to step S11. When the determination result of step S12 is NO, the laser control processor 50 proceeds to step S13.
In step S13, the laser control processor 50 transmits a command to the solid-state seeder control processor 112 to adjust the frequency of the pseudo-random signal controlling the optical phase modulator 104 via the solid-state seeder control processor 112. After step S13, the laser control processor 50 returns to step S11.
Other operation may be the same as the operation of the laser device 10 according to the comparative example described with reference to
The pseudo-random signal generator 111 includes the D flip-flops FF1 to FF4, an exclusive OR (XOR) circuit 162, a variable bandpass filter 164, and an amplifier 166. As shown in
Although
By increasing clock frequency, a pseudo-random signal having a higher frequency band can be generated.
Time Ta in
The pulse current (injection current) is supplied to the SOA after a second delay time (delay2) from the timing of the trigger signal Tr2. Here, delay2 is the sum of the time of delay1 and the time until the SOA starts amplification after the phase-modulated laser light reaches the SOA.
Pulse light is output from the SOA after a third delay time (delay3) from the timing of starting to increase the SOA injection current. Here, delay3 is the period of delay for propagating in the SOA after continuous light entering the SOA is pulsed at the SOA.
As shown in
According to the first embodiment, since the pseudo-random signal having the identical pattern is generated in synchronization with the trigger signal Tr2 synchronized with the timing of generation of the pulse light and is superimposed on the optical phase modulator 104, the modulation signal having the identical waveform for each pulse is superimposed on the optical phase modulator 104, and the spectral shape of the superimposed signal is also the identical for each pulse. Therefore, since the optical spectrum of the laser light output from the optical phase modulator 104 is modulated identically for each pulse, the optical spectral shape is identical for each pulse, and the spectral line width is also identical for each pulse and stabilized.
In
Further, for example, the spectral line width of the pulse laser light PL1 may be measured with a configuration in which a beam splitter is arranged on the optical path between the wavelength conversion system 108 and the excimer amplifier 30, and a part of the pulse laser light PL2 output from the wavelength conversion system 108 is sampled and guided to a measurement instrument such as a spectrum monitor.
That is, each of the pulse laser light PL1, PL2, PL3 propagating downstream of the solid-state amplifier 106 is an example of the “pulse laser light pulse-amplified by the first amplifier” in the present disclosure.
Further, in the first embodiment, the CW light from the semiconductor laser is converted to pulse laser light by causing a pulse current to flow through the SOA, but the method of generating the pulse laser light is not limited thereto. For example, the CW light from the semiconductor laser may be amplified into pulse laser light by exciting the excitation light of the titanium-sapphire crystal of the solid-state amplifier 106 with the pulse light.
Alternatively, instead of the SOA, an optical shutter may be used for optical pulsing. The optical shutter may be a combination of an electro optical (EO) pockels cell and a polarizer, or may be a Mach-Zehnder optical modulator using an EO effect.
Further, in the solid-state seeder 22, an optical bandpass filter (BPF) 182 is arranged on the optical path between the optical phase modulator 104 and the solid-state amplifier 106. Other configurations may be similar to those in
The CW laser light having a wavelength of about 773.6 nm is output from the semiconductor laser of the solid-state seeder 22. The solid-state seeder control processor 112 transmits the trigger signal Tr2 to the sweep frequency generator 180. The sweep frequency generator 180 sets a delay time of delay1 at the timing of the trigger signal Tr2, and then sweeps the frequency by changing the frequency at a substantially constant sweep speed (change in frequency per unit time) over a desired time, and outputs a frequency sweep signal.
The optical phase modulator 104 phase-modulates the CW laser light with the frequency sweep signal supplied from the sweep frequency generator 180 to change the optical spectral shape.
In the frequency shift chart of the frequency sweep signal shown at the second stage from the top, the vertical axis indicates the frequency as showing an example in which the base frequency is fm and the sweep width is Δf. That is, the frequency of the frequency sweep signal may vary from fm to fm+Δf. Note that the sweep width Δf satisfies Δf<fm. Although
The frequency shift of the frequency sweep signal is started after the delay time of delay1 with respect to the timing of the trigger signal Tr2, and the frequency is changed at a constant rate during the period of time Tb. Here, delay1 is adjusted so that the light modulated with the frequency sweep signal of the time Tb is pulsed at the SOA in the solid-state amplifier 106. The time Tb is equal to or longer than the time Ta described with reference to
The change of the optical spectral shape will be described with reference to
The solid-state seeder control processor 112 sweeps the modulation frequency fm to change the spectral line width (see F11B). F11B shown at the lower stage of
The solid-state seeder 22 uses only the +1st order sideband of the frequency fc+fm shown in F11B, and cuts off other spectral components (in the example of
For controlling the spectral line width, the sweep width of the modulation frequency fm is adjusted so that the target spectral line width is obtained based on the spectral line width measured by the monitor module.
In step S14, the laser control processor 50 transmits a command to the solid-state seeder control processor 112 to adjust the sweep width of the frequency sweep signal controlling the optical phase modulator 104 via the solid-state seeder control processor 112. After step S14, the laser control processor 50 returns to step S11. Other steps may be similar to those in
According to the second embodiment, since the waveform of the modulation signal input to the optical phase modulator 104 is synchronized with the trigger signal Tr2, the pulse laser light is modulated with the identical waveform. According to the above, the optical spectral shape is identical for each pulse, and the spectral line width is also identical for each pulse.
In order to facilitate the control of the spectral line width, as shown in
Modification of the solid-state seeder 21 described with reference to
The solid-state seeder 23 includes a first solid-state laser device 200, a second solid-state laser device 210, a dichroic mirror 230, the wavelength conversion system 240, the solid-state seeder control processor 112, and the pseudo-random signal generator 111.
The solid-state seeder 23 has a system configuration in which pulse laser light PL4 having a wavelength of about 1554 nm output from the first solid-state laser device 200 and pulse laser light PL5 having a wavelength of about 257.6 nm output from the second solid-state laser device 210 are converted to the pulse laser light PL2 having a wavelength of about 193.4 nm by two times of sum frequency in the wavelength conversion system 240.
The first solid-state laser device 200 includes a semiconductor laser system 204 and a solid-state amplifier 206. The semiconductor laser system 204 may have a configuration similar to that of the semiconductor laser system 100 shown in
The solid-state amplifier 206 may be an optical parametric amplifier (OPA). The OPA is, for example, a periodically poled lithium niobate (PPLN) crystal or a periodically poled potassium titanyl phosphate (PPKTP) crystal.
The solid-state amplifier 206 is configured to pulse-amplify the seed light by receiving pulse laser light having a wavelength of 1030 nm to be described later as pumping light and laser light output from the semiconductor laser system 204 as seed light.
The second solid-state laser device 210 includes a semiconductor laser system 212, the optical phase modulator 104, a solid-state amplifier 216, an LBO crystal 220 and a CLBO crystal 222, which are two nonlinear crystals for performing second harmonic generation twice and wavelength-converting such that the optical frequency becomes four times, and a dichroic mirror 224. “CLBO” is represented by the chemical formula CsLiB6O10.
The semiconductor laser system 212 may have a configuration similar to that of the semiconductor laser system 100 shown in
The solid-state amplifier 216 may be configured to include, for example, a Yb fiber amplifier or a Yb:YAG crystal. The solid-state 216 may amplifier have a configuration similar to that of the solid-state amplifier 106. The optical phase modulator 104 is arranged on the optical path between the semiconductor laser system 212 and the solid-state amplifier 216. The solid-state amplifier 216 is an example of the “first amplifier” in the present disclosure.
The dichroic mirror 224 is arranged on the optical path between the LBO crystal 220 and the CLBO crystal 222, and highly transmits pulse laser light having a wavelength of about 515 nm and highly reflects pulse laser light having a wavelength of about 1030 nm. The dichroic mirror 224 is arranged such that the highly reflected pulse laser light having a wavelength of about 1030 nm is incident thereon as the pumping light of the solid-state amplifier 206. Instead of the dichroic mirror 224, a beam splitter (not shown) may be arranged between the LBO crystal 220 and the solid-state amplifier 216, and the pulse laser light output from the solid-state amplifier 216 may be branched so as to enter the LBO crystal 220 and the solid-state amplifier 206, respectively.
The wavelength conversion system 240 includes a CLBO crystal 242 and a CLBO crystal 243, and a rotation stage 252 and a rotation stage 253. The CLBO crystal 242 and the CLBO crystal 243 are arranged on the rotation stage 252 and the rotation stage 253 including piezoelectric elements, respectively, and are configured so that the incident angles on the respective crystals can be changed at high speed.
The dichroic mirror 230 is configured to highly reflect the pulse laser light PL4 having a wavelength of about 1554 nm output from the first solid-state laser device 200 and to highly transmit the pulse laser light PL5 having a wavelength of about 257.6 nm output from the second solid-state laser device 210, and is arranged so that both pulse laser lights coaxially enter the wavelength conversion system 240.
In the solid-state seeder 23, the wavelength of the pulse laser light PL4 output from the first solid-state laser device 200 is changed from pulse to pulse while the wavelength of the pulse laser light PL5 output from the second solid-state laser device 210 is fixed, whereby the wavelength of the pulse laser light PL2 output from the wavelength conversion system 240 can be changed.
The operation of the second solid-state laser device 210 is as follows. The solid-state seeder control processor 112 fixes the oscillation wavelength of the second solid-state laser device 210 to 1030 nm. That is, the solid-state seeder control processor 112 causes the semiconductor laser to continuously oscillate with the current value of the semiconductor laser in the semiconductor laser system 212 kept constant, and the semiconductor laser to output CW laser light.
The CW laser light output from the semiconductor laser system 212 is phase-modulated by the optical phase modulator 104 and enters the solid-state amplifier 216. The operation of the pseudo-random signal generator 111 and the optical phase modulator 104 are the same as those of the first embodiment described with reference to
The solid-state seeder control processor 112 causes the solid-state amplifier 216 to pulse-amplify the CW laser light in synchronization with the trigger signal Tr2. The solid-state amplifier 216 outputs pulse laser light PL6 having a wavelength of 1030 nm.
The pulse laser light PL6 having a wavelength of 1030 nm output from the solid-state amplifier 216 is converted to the second harmonic light having a wavelength of 515 nm in the LBO crystal 220. The second harmonic light having a wavelength of about 515 nm is highly transmitted through the dichroic mirror 224, and is converted by the CLBO crystal 222 to the pulse laser light PL5 having a wavelength of about 257.6 nm.
Here, the dichroic mirror 224 highly reflects the pulse laser light having a wavelength of 1030 nm that has not been wavelength-converted by the LBO crystal 220, and causes the pulse laser light to enter as the pumping light of the solid-state amplifier 206 of the first solid-state laser device 200.
On the other hand, the laser control processor 50 and the solid-state seeder control processor 112 can change the wavelength of the pulse laser light PL4 output from the first solid-state laser device 200 in the vicinity of 1554 nm by controlling the temperature value and/or the current value of the semiconductor laser in the semiconductor laser system 204 of the first solid-state laser device 200. The solid-state seeder control processor 112 may change the oscillation wavelength of the semiconductor laser system 204 from pulse to pulse.
The pulse laser light PL4 having a wavelength of about 1554 nm output from the first solid-state laser device 200 and the pulse laser light PL5 having a wavelength of 257.6 nm output from the CLBO crystal 222 are sum-frequency-mixed by the CLBO crystal 242 of the wavelength conversion system 240 and wavelength-converted to pulse laser light having a wavelength of about 220.9 nm. Further, by the CLBO crystal 243, the pulse laser light having a wavelength of about 220.9 nm and the pulse laser light having a wavelength of 1554 nm are sum-frequency-mixed and wavelength-converted to the pulse laser light PL2 having a wavelength of about 193.4 nm. Then, the pulse laser light PL2 is output from the wavelength conversion system 240.
In
Modification of the solid-state seeder 22 described with reference to
The operation of the sweep frequency generator 180, the optical phase modulator 104, and the optical bandpass filter 182 shown in
The CW laser light output from the semiconductor laser system 212 has a desired optical spectral shape due to the optical phase modulator 104 to which the frequency sweep signal output from the sweep frequency generator 180 is applied and the optical bandpass filter 182, and has the identical optical spectral shape for each pulse. Other operation is similar to that in the first embodiment described with reference to
The semiconductor laser used in the semiconductor laser system is not limited to a DFB laser, and may be a distributed Bragg reflector (DBR) type semiconductor laser or a sampled grating distributed Bragg reflector (SG-DBR) type semiconductor laser.
The first and second embodiments show an example of a three-multipass amplifier as the excimer amplifier, but not limited to a multipass amplifier, an amplifier including, for example, an optical resonator such as a Fabry-Perot resonator or a ring resonator may be adopted.
The first and second embodiments show an exemplary configuration in which a solid-state seeder and an ArF excimer amplifier are combined, but not limited to these embodiments, a combination of an excimer amplifier including a KrF laser gas and a solid-state seeder that oscillates in an amplification wavelength band of a KrF excimer may be adopted. Specifically, the solid-state seeder may be a semiconductor laser system that outputs pulse laser light having a wavelength of about 745.2 nm, a solid-state amplifier, and a wavelength conversion system that converts the wavelength to third harmonic light having a wavelength of about 248.4 nm. The wavelength conversion element in this case may be an LBO crystal that performs wavelength conversion to the second harmonic light and a CLBO crystal that performs sum-frequency-mixing of the second harmonic light and the fundamental wave.
The exposure apparatus 80 synchronously translates the reticle stage RT and the workpiece table WT to expose the workpiece to the laser light reflecting the reticle pattern. After the reticle transferred pattern is onto the semiconductor wafer by the exposure process described above, a semiconductor device can be manufactured through a plurality of processes. The semiconductor device is an example of the “electronic device” in the present disclosure. Instead of the laser device 11, the laser device 12 may be applied.
The configuration of the laser device according to a third embodiment may be similar to the configuration shown in
The operation of the laser device according to the third embodiment will be described in terms of differences from the operation of the laser device 11 according to the first embodiment. In the laser device 11 according to the first embodiment, the spectral line width of the pulse laser light PL3 is controlled by adjusting the frequency of the pseudo-random signal s the modulation signal for controlling the optical phase modulator 104, whereas in the laser device according to the third embodiment, the spectral line width of the pulse laser light PL3 is controlled by adjusting the power of the modulation signal having an identical pattern in synchronization with the light emission trigger signal Tr.
In step S22, the laser control processor 50 calculates a difference between the target spectral line width periodically updated by the exposure control processor 86 and the measurement result (measured spectral line width) in step S21.
In step S23, the laser control processor 50 determines whether or not the difference calculated in step S22 is within an allowable range. When the determination result of step S23 is YES, that is, when the difference is within the allowable range, the laser control processor 50 returns to step S21.
On the other hand, when the determination result of step S23 is NO, that is, when the difference is outside the allowable range, the laser control processor 50 proceeds to step S24.
In step S24, the laser control processor 50 determines the power of the modulation signal based on a predetermined function indicating the relationship between the square root of the power of the modulation signal and the spectral line width and the difference calculated in step S22, and changes the power of the modulation signal to be superimposed on the optical phase modulator 104. When the spectral line width measured in step S21 (measurement result of step S21) is smaller than the target range, the laser control processor 50 increases the power of the modulation signal. On the other hand, when the spectral line width measured in step S21 is larger than the target range, the laser control processor 50 reduces the power of the modulation signal. Here, instead of the predetermined function indicating the relationship between the square root of the power of the modulation signal and the spectral line width, table data indicating the relationship between the square root of the power of the modulation signal recorded in advance and the spectral line width may be used. The operation of step S24 may be performed by the solid-state seeder control processor 112 in accordance with the command of the laser control processor 50.
After step S24, the laser control processor 50 returns to step S21. Other operation may be similar to the operation of the laser device 11 of the first embodiment.
According to the laser device of the third embodiment, since the relationship between the square root of the power of the modulation signal and the spectral line width of the pulse laser light PL3 has high linearity (see
In the pseudo-random signal generator 312, a trigger regeneration circuit 314 and an initial value setting circuit 316 are added, and an initial value of a shift register 360 is adjusted so that the shape (spectral shape) of the spectral waveform of the generated pulse laser light PL3 is unimodal.
The pseudo-random signal generator 312 includes D flip-flops FF1 to FF36, at least one exclusive OR (XOR) circuit 162, the variable bandpass filter 164, and the amplifier 166. As shown in
The trigger regeneration circuit 314 generates a timing signal that changes initial values of the D flip-flops FF1 to FF36 based on the trigger signal Tr2 from the solid-state seeder control processor 112 and the clock of the pseudo-random signal generator 312.
The initial value setting circuit 316 transmits, in synchronization with the timing signal generated by the trigger regeneration circuit 314, a signal to a SET terminal or a CLR terminal of each of the D flip-flops FF1 to FF36 so that the initial value of each of the D flip-flops FF1 to FF36 is set to “0” or “1” (“Low” or “Hi”) by the control signal from the solid-state seeder control processor 112. For example, the signal is transmitted to the CLR terminal to set the initial value to “0”, and the signal is transmitted to the SET terminal to set the initial value to “1”.
Although
In step S32, the laser control processor 50 determines whether the measured spectral shape is unimodal or multimodal and determines whether or not the spectrum waveform is unimodal. When the determination result of step S32 is NO, that is, when the spectral shape is multimodal, the laser control processor 50 proceeds to step S33.
In step S33, the laser control processor 50 changes the initial value of the shift register 360 via the solid-state seeder control processor 112 and returns to step S31.
On the other hand, when the determination result of step S32 is YES, that is, when the spectral shape is unimodal, the laser control processor 50 proceeds to step S34.
In step S34, the laser control processor 50 measures the spectral line width from the acquired spectrum waveform.
In step S35, the laser control processor 50 calculates a difference between the target spectral line width periodically updated by the exposure control processor 86 and the measurement result in step S34.
In step S36, the laser control processor 50 determines whether or not the calculated difference is within an allowable range. When the determination result of step S36 is YES, that is, when the difference is within the allowable range, the laser control processor 50 returns to step S31.
On the other hand, when the determination result of step S36 is NO, that is, when the difference is outside the allowable range, the laser control processor 50 proceeds to step S37. Step S37 is similar to step S24 of
According to the laser device of the fourth embodiment, by adjusting the initial value of the shift register 360, it is possible to always control the target spectral line width with a unimodal spectral shape. Further, as described with reference to
Here, even when the bandwidth of the modulation signal is to be adjusted instead of step S37 shown in
The configuration of the laser device according to a fifth embodiment is similar to the configuration of the laser device according to the fourth embodiment. The laser device according to the fifth embodiment differs from the laser device according to the fourth embodiment in the content of the control performed by the laser control processor 50.
The operation of the laser device according to the fifth embodiment will be described in terms of differences from the operation of the laser device according to the fourth embodiment. The laser device according to the fifth embodiment coarsely adjusts the spectral line width of the pulse laser light PL3 by changing the bandwidth of the modulation signal to be superimposed on the optical phase modulator 104, and finely adjusts the spectral line width of the pulse laser light PL3 by changing the power of the modulation signal. The fine adjustment is adjustment with a smaller adjustment amount than the coarse adjustment. For example, the range of the adjustment amount of the spectral line width adjustable by the fine adjustment may be equal to or less than 0.4 pm, and the range of the adjustment amount of the spectral line width adjustable by the coarse adjustment may be greater than 0.4 pm and equal to or less than 3 pm.
The laser control processor 50 of the laser device according to the fifth embodiment determines whether to perform the coarse adjustment or the fine adjustment according to the magnitude of the difference between the target spectral line width and the measured spectral line width. The fine adjustment may be performed when the difference from the target value is outside the allowable range and equal to or less than 0.4 pm (hereinafter, within the allowable range of the fine adjustment), and the coarse adjustment may be performed when the difference from the target value is outside the allowable range and greater than 0.4 pm and equal to or less than 3 pm (hereinafter, within the allowable range of the coarse adjustment).
The flowchart shown in
After step S35, in step S38, the laser control processor 50 determines whether or not the difference calculated in step S35 is within the allowable range of the coarse adjustment. When the determination result of step S38 is NO, that is, when the difference is outside the allowable range of the coarse adjustment, the laser control processor 50 proceeds to step S39.
In step S39, the laser control processor 50 changes the bandwidth of the modulation signal to be superimposed on the optical phase modulator 104 by the variable bandpass filter 164. In step S39, the method of the first embodiment is applied. The operation of step S39 may be performed by the solid-state seeder control processor 112 in accordance with the command of the laser control processor 50. After step S39, the laser control processor 50 returns to step S31.
When the determination result of step S38 is YES, that is, when the difference is within the allowable range of the coarse adjustment, the laser control processor 50 proceeds to step S40. In step S40, the laser control processor 50 determines whether or not the difference calculated in step S35 is within the allowable range of the fine adjustment. When the determination result of step S40 is YES, that is, when the difference is within the allowable range of the fine adjustment, the laser control processor 50 returns to step S31.
When the determination result of step S40 is NO, that is, when the difference is outside the allowable range of the fine adjustment, the laser control processor 50 proceeds to step S41. Step S41 is similar to step S24 of
According to the laser device of the fifth embodiment, by adjusting the initial value of the shift register 360, it is possible to always control the target spectral line width with a unimodal spectral shape. Further, in the laser device according to the fifth embodiment, the bandwidth of the modulation signal is changed when the spectral line width is to be coarsely adjusted, and the power of the modulation signal is changed when the spectral line width is to be finely adjusted, so that the amount of changing the power of the modulation signal is smaller than when the spectral line width is controlled only by the power of the modulation signal. Therefore, the stability of the entire modulation signal generator including pseudo-random signal the generator 111 is improved and the thermal load applied to the optical phase modulator 104 and the like is small, and stable control is possible.
Further, compared with the case in which the spectral line width is controlled only by the bandwidth of the modulation signal, the setting resolution can be finer when the power of the modulation signal is changed.
An input-side optical fiber 410 and a lens 412 are arranged on the optical input port side of the optical phase modulator 104, and a lens 414 and an output-side optical fiber 416 are arranged on the optical output port side. The lens 412 and the lens 414 are arranged to face each other with the lithium niobate crystal 400 interposed therebetween. The laser light guided by the input-side optical fiber 410 is input to the lithium niobate crystal 400 via the lens 412. The laser light having passed through the optical waveguide 404 enters the output-side optical fiber 416 via the lens 414, and is guided to the solid-state amplifier 106 (see
Instead of the laser device 11 used together with the exposure apparatus 80 shown in
The description above is intended to be illustrative and the present disclosure is not limited thereto. Therefore, it would be obvious to those skilled in the art that various modifications to the embodiments of the present disclosure would be possible without departing from the spirit and the scope of the appended claims. Further, it would be also obvious to those skilled in the art that the embodiments of the present disclosure would be appropriately combined.
The terms used throughout the present specification and the appended claims should be interpreted as non-limiting terms unless clearly described. For example, terms such as “comprise”, “include”, “have”, and “contain” should not be interpreted to be exclusive of other structural elements. Further, indefinite articles “a/an” described in the present specification and the appended claims should be interpreted to mean “at least one” or “one or more.” Further, “at least one of A, B, and C” should be interpreted to mean any of A, B, C, A+B, A+C, B+C, and A+B+C as well as to include combinations of any thereof and any other than A, B, and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/034458 | Sep 2022 | WO | international |
The present application the claims benefit of International Application No. PCT/JP2023/024268 filed Jun. 29, 2023, which claims priority to International Application No. PCT/JP2022/034458 filed Sep. 14, 2022. Each of the above applications is hereby expressly incorporated by reference, in its entirety, into the present application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/024268 | Jun 2023 | WO |
| Child | 19044183 | US |
