Laser amplification device and extreme ultraviolet light generating device

Abstract

The invention comprises: a laser oscillator (20) having a first laser active medium, the first laser active medium having a mixed gas containing carbon dioxide gas, the laser oscillator (20) oscillating a pulse laser having a half-value full width between 15 ns and 200 ns; and a laser amplifier (30) having a second laser active medium, the second laser active medium having a mixed gas containing carbon dioxide gas, the pulse laser oscillated from the laser oscillator (20) passing through the second laser active medium, thereby being shortened to a pulse laser having a half-value full width between 5 ns and 30 ns and outputted.

Description

Technical Field

[0001] The invention relates to a laser amplifying device and an extreme ultraviolet light generating device having the laser amplifying device. Background Art

[0002] Patent Document 1 discloses a technique for extending the pulse width of laser light by amplifying pulsed laser light output from an oscillation laser device, the intensity of which increases with time, at an amplification factor that decreases with time.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2013-084971 Summary of the invention

[0004] In Patent Document 1, since the pulse width of the laser light input to the amplifier is short, there is a problem that the amplification factor is reduced due to the influence of the rotation relaxation of the laser medium.

[0005] The present invention has been proposed in view of the above-mentioned problems, and an object of the present invention is to obtain a laser amplification device and an extreme ultraviolet light generating device that can prevent a decrease in amplification factor and can emit high-output extreme ultraviolet light.

[0006] In order to solve the above-mentioned problems and achieve the purpose, the laser amplification device involved in the present invention comprises: a laser oscillator, which has a first laser active medium, the first laser active medium has a mixed gas including carbon dioxide gas, and oscillates a pulse laser with a half-value full width between 15ns and 200ns; and a laser amplifier, which has a second laser active medium, the second laser active medium has a mixed gas including carbon dioxide gas, and the pulse laser oscillated from the laser oscillator passes through the second laser active medium, thereby shortening it to a pulse laser with a half-value full width between 5ns and 30ns and outputting it.

[0007] Effects of the Invention

[0008] According to the present invention, it is possible to provide a laser amplification device that can prevent a decrease in amplification factor in a laser amplifier and can emit high-output extreme ultraviolet light. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a diagram showing the structure of an extreme ultraviolet light generating device having a laser amplification device according to Embodiment 1.

[0010] Figure 2 This is a diagram showing the pulse width dependency characteristics of amplification of a laser amplifier in a MOPA-type CO 2 laser.

[0011] Figure 3 This is a diagram showing the detailed structure of an extreme ultraviolet light generating device having a laser amplification device according to Embodiment 1.

[0012] Figure 4 This is a diagram showing the relationship between the pulse width of the pulse laser light input to the laser amplifier and the pulse width of the pulse laser light emitted from the laser amplifier.

[0013] Figure 5 This is a diagram showing a change process of a pulse waveform when a super-Gaussian laser pulse is amplified.

[0014] Figure 6 This is a diagram showing how the pulse waveform changes when a Gaussian laser pulse is amplified.

[0015] Figure 7 This is a diagram showing an example of the shape of a super-Gaussian laser pulse.

[0016] Figure 8 It represents the ratio T r A graph showing the relationship between and the coefficient P.

[0017] Fig. 9 This is a diagram showing changes in pulse shape and intensity during the amplification process of laser pulses.

[0018] Fig.10 This is an explanatory diagram showing the generation of super-Gaussian shaped pulses caused by Q-switch cavity dumping oscillation.

[0019] Fig.11 This is an explanatory diagram of the generation of Gaussian-shaped pulses when the switching time of the electro-optical element is long.

[0020] Fig.12 This is a diagram illustrating an example of pulse shortening when laser pulses having different pulse widths are incident on a laser amplifier.

[0021] Fig.13 This is a diagram illustrating an example of pulse shortening when laser pulses having different pulse widths are incident on a laser amplifier.

[0022] Fig.14 This is a diagram showing the structure of an extreme ultraviolet light generating device having a laser amplification device according to a second embodiment.

[0023] Fig.15 This is a diagram showing outgoing light traveling from a laser oscillator to a laser amplifier in the laser amplification device according to the second embodiment.

[0024] Fig.16 This is a diagram showing return light traveling from the laser amplifier to the laser oscillator in the laser amplification device according to the second embodiment.

[0025] Fig.17 It is a timing chart of the voltage applied to the electro-optical element and a timing chart of the laser pulse output from the laser oscillator.

[0026] Fig.18 This is a diagram illustrating the operation of a pulse shaper as an electro-optical element and a polarization beam splitter.

[0027] Fig.19 This is a diagram illustrating the operation of a pulse shaper as an electro-optical element and a polarization beam splitter.

[0028] Fig. 20 This is a diagram illustrating the operation of a pulse shaper as an electro-optical element and a polarization beam splitter.

[0029] Fig.21 This is a diagram showing another structure of the extreme ultraviolet light generating device having the laser amplification device of embodiment 2.

[0030] Fig. 22 This is a diagram illustrating laser pulses that are input to and output from a laser amplifier.

[0031] Fig.23 This is a diagram illustrating laser pulses that are input to and output from a laser amplifier.

[0032] Fig.24 This is a diagram showing the structure of an extreme ultraviolet light generating device having a laser amplification device according to a third embodiment.

[0033] Fig.25 This is a diagram showing another structure of the extreme ultraviolet light generating device having the laser amplification device of embodiment 3.

[0034] Fig.26 This is a diagram showing an example of the amplification characteristics when the gas pressure of the CO 2 laser amplifier is changed.

[0035] Fig. 27 This is a diagram showing a situation where the repetitive pulses output from the oscillator have intensity fluctuations.

[0036] Fig.28 This is a graph showing that the fluctuation of the repetitive pulse is reduced after amplification.

[0037] Fig.29 This is a diagram showing an example of an estimation device for estimating a pulse waveform output from a laser amplifier in the fourth embodiment.

[0038] Fig.30 This is a flowchart showing the processing procedure of the estimation device.

[0039] Fig.31 This is a diagram showing an example of a learning device that learns the pulse waveform output from a laser amplifier in the fourth embodiment.

[0040] Fig.32 This is a flowchart showing the processing procedure of the learning device.

[0041] Fig.33 This is a diagram showing an example of another learning device in the fourth embodiment. DETAILED DESCRIPTION

[0042] Hereinafter, a laser amplification device and an extreme ultraviolet light generating device according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0043] Implementation method 1.

[0044] Figure 1 This is a diagram showing the structure of an extreme ultraviolet light generator 100 having a laser amplification device 10 according to Embodiment 1. Extreme ultraviolet light is also referred to as EUV (Extreme Ultraviolet) light, and an extreme ultraviolet light generator is also referred to as an EUV light generator. The EUV light generator 100 is used as a light source of an exposure device, and emits EUV light with a wavelength of 13.5 nm. The EUV light generator 100 includes a laser amplification device 10 and an EUV light generator 40.

[0045] The laser amplifier 10 is a laser amplifier of the MOPA (Master Oscillator Power Amplifier) ​​type. The laser amplifier 10 includes a laser oscillator 20 and a laser amplifier 30. The laser oscillator 20 includes an oscillator, and emits a pulse laser 25. The oscillator includes a laser active medium composed of a mixed gas including carbon dioxide gas (CO2 gas). The laser amplifier 30 amplifies the pulse laser 25 output from the laser oscillator 20, and outputs the amplified pulse laser 35 to the EUV light generator 40. The pulse laser 25 is also referred to as an incident laser pulse 25, and the pulse laser 35 is also referred to as an outgoing laser pulse 35. In addition, the pulse laser is also referred to as a laser pulse.

[0046] The EUV light generator 40 has a droplet generator 41 and a collector mirror 42. The collector mirror 42 has a transmission portion in the center portion that allows the pulse laser 35 emitted from the laser amplifier 30 to pass through. In the EUV light generator 40, the droplets DL dropped from the droplet generator 41 are irradiated with the pulse laser 35 emitted from the laser amplifier 30. As the droplets DL, tin (Sn), xenon (Xe), gadolinium (Gd), ytterbium (Tb), etc. are used. If the droplets DL are irradiated with the pulse laser 35, the droplets DL are plasmatized, and EUV light 50 with a wavelength of 13.5 nm is emitted from the plasmatized droplets DL. The emitted EUV light 50 is focused toward an intermediate focusing (IF: Intermediate Focus) point 60 by the collector mirror 42. At Figure 1Although not shown in the figure, the EUV light generator 40 also has a droplet catcher, etc. In addition, in the EUV light generator 40, a pre-pulse may be irradiated in order to increase the EUV light output.

[0047] In the extreme ultraviolet light generating device 100, when the pulse width of the pulse laser 35 irradiated to the droplet DL is about 5ns to 30ns, the conversion efficiency to EUV light becomes high, and high-output EUV light is obtained. In the exposure device using the extreme ultraviolet light generating device 100, it is desired to obtain high-output EUV light exceeding 250W at the IF point 60, and the pulse laser 35 exceeding 20kW is effective in emitting high-output EUV light.

[0048] Therefore, in the extreme ultraviolet light generating device 100, in order to obtain high-output EUV light, it is desirable to irradiate the target material, ie, the droplet DL, with a pulse laser 35 having a pulse width of 5 ns to 30 ns and an output of 20 kW or more.

[0049] exist Figure 2 An example of the pulse width dependency characteristic of amplification by the laser amplifier 30 in the MOPA-type CO 2 laser is shown. Figure 2 The horizontal axis shows the pulse width τ of the pulse laser 25 injected into the laser amplifier 30. p Divided by the rotational relaxation time τ of the CO2 molecule r The obtained value τ p / τ r . Pulse width τ p It is expressed as the full width at half maximum. Figure 2 The vertical axis shows the normalized extraction energy η ext . Normalized extraction energy η ext is the energy extracted from the laser amplifier 30 divided by τ p >>τ r The value obtained by the extraction energy at the time. ext Also referred to as the extraction energy η ext τ p >>τ r The pulse width τ of the pulse laser 25 is shown p Than the rotational relaxation time τ of CO2 molecules r Fully large. Figure 2 In the characteristic of the pulse laser 25 incident on the laser amplifier 30, the energy density E in The saturation energy density E of the laser amplifier 30 is s Sufficiently large.

[0050] according to Figure 2 , we know the value τ p / τ rIn other words, the larger the pulse width τ of the pulse laser 25 incident on the laser amplifier 30 is, the p Specific rotation relaxation time τ r The longer it is, the more energy η is extracted ext The larger it becomes, the greater the energy extracted from the laser amplifier 30 becomes. In the gain spectrum of the active medium of the CO2 laser, the pressure expansion dominates, and at pressures greater than 20 Torr, the rotation relaxation time τ r In typical cases, it is about several nanoseconds. Therefore, if the pulse width τ effective for emitting high-output EUV light is set to p A laser pulse of 5 ns to 30 ns is injected into the laser amplifier 30, and then according to Figure 2 It can be seen that the extracted energy η ext If the ratio is not approximately 1, sufficient energy cannot be extracted from the laser amplifier 30. As a result, the amplification factor of the laser amplifier 30 decreases, and the output of EUV light obtained at the IF point 60 decreases.

[0051] Therefore, in the first embodiment, the pulse width τ of the pulse laser 25 incident on the laser amplifier 30 is set to p By setting the time to 15 ns to 200 ns, the influence of the rotation relaxation of the CO 2 molecules is suppressed and amplified, thereby improving the amplified output of the laser amplifier 30 .

[0052] Figure 3 1 is a diagram showing a more detailed configuration example of the EUV light generator 100 according to Embodiment 1. The EUV light generator 100 includes a laser oscillator 20 that generates a pulse with a width τ of 15 ns to 200 ns. p The laser amplifier 30 amplifies the pulsed laser 25 output from the laser oscillator 20 and outputs a pulsed laser 35 having a pulse width of 5 ns to 30 ns; and an EUV light generator 40 irradiates the target material, i.e., the droplet DL, with the pulsed laser 35 output from the laser amplifier 30 to emit EUV light.

[0053] exist Figure 3In the figure, the laser oscillator 20 is a Q-switch cavity dumping oscillator. The laser oscillator 20 has a mixed gas containing CO2 gas, i.e., a laser active medium 21, an electro-optical element 22, a polarization beam splitter 23, a resonator mirror 24, and a resonator mirror 26. The pulse laser output from the laser oscillator 20 is transmitted to the laser amplifier 30 through a mirror 27. The laser oscillator 20 is composed of a resonator mirror 24 and a resonator mirror 26 to form a resonator. In the mixed gas containing CO2 gas, in addition to CO2 gas, for example, nitrogen (N2), helium (He), carbon monoxide (CO), xenon (Xe), oxygen (O2), hydrogen (H2) and other gases may also be included. In the laser oscillator 20, by modulating the voltage applied to the electro-optical element 22 at a high repetition frequency greater than or equal to 5 kHz, for example, a pulse width τ of 15ns to 200ns is obtained through Q-switch cavity dumping oscillation. p The pulsed laser 25 is emitted. Figure 3 In the example of the laser oscillator 20 performing Q-switched cavity dumping oscillation, other pulse oscillations such as Q-switched oscillations may also be used. In addition, the laser oscillator 20 may also be a pulsed laser oscillator such as a quantum cascade laser that can oscillate at the oscillation wavelength of a CO2 laser. Figure 3 Although the electro-optical element 22 is used, an acousto-optical element may be used to emit a pulse laser 25 having a pulse width of 15 ns to 200 ns.

[0054] The laser amplifier 30 is an amplifier having a mixed gas including CO2 gas as an amplification active medium. Figure 3 In the example of the laser amplifier 30, a single-stage amplifier is shown, but a multi-stage laser amplifier in which multiple amplifiers are arranged may be used. The beam diameter of the pulsed laser can be adjusted in the laser amplifier 30 by using a lens, a reflector, etc. so that the amplified output in the laser amplifier 30 becomes the maximum. The pulse width τ of 15ns to 200ns injected into the laser amplifier 30 is p The pulsed laser light 25 is amplified by the laser amplifier 30 and output as the pulsed laser light 35 having a pulse width of 5 ns to 30 ns.

[0055] EUV light generator 40 Figure 1 As shown, there is a droplet generator 41 and a collector mirror 42.

[0056] In the configuration according to the first embodiment, the pulse width τ of the pulse laser 25 incident on the laser amplifier 30 is set to p By setting the rotation relaxation time τ to 15 ns to 200 ns, the influence of the rotation relaxation of the CO 2 molecules can be suppressed and amplification can be performed, thereby increasing the amplified output of the laser amplifier 30. For the following description, the rotation relaxation time τ is set to rThe discussion is set to 1.5ns, but the rotation relaxation time τ is not r To be limited.

[0057] Figure 4 is the pulse width τ of the pulse laser 25 incident on the laser amplifier 30 p and the pulse width of the pulse laser 35 emitted from the laser amplifier 30. Figure 4 In FIG. 1 , the vertical axis shows the pulse width (ns) of the outgoing laser pulse 35, and the horizontal axis shows the pulse width τ of the incident laser pulse 25. p As described above, in the EUV light generator 40, the conversion efficiency to EUV light becomes high when the pulse width of the emitted laser pulse 35 is 5 ns to 30 ns. Figure 4 In the region where the pulse width of the emitted laser pulse 35, where the conversion efficiency to EUV light is high, is 5 ns to 30 ns, the rotation relaxation time τ is used. r The normalized extraction energy η at 1.5 ns ext The value of is divided into four areas including area A, area B, area C and area D.

[0058] Region A is the pulse width τ of the incident laser pulse 25 p The range is 5ns to 15ns, such as Figure 2 As shown, it is the standardized extraction energy η ext <0.5 area.

[0059] Region B is the pulse width τ of the incident laser pulse 25 p The range is 15ns to 30ns, such as Figure 2 As shown, 0.5<η ext <0.75 area.

[0060] Region C is the pulse width τ of the incident laser pulse 25 p The range is 30ns to 50ns, such as Figure 2 As shown, 0.75<η ext <0.9 area.

[0061] Region D is the pulse width τ of the incident laser pulse 25 p The range is 50ns to 200ns, such as Figure 2 As shown, it is η ext >0.9 area.

[0062] As mentioned above, the output of the laser amplifier 30 is located at Figure 4 The further to the right, the higher it becomes. If arranged in order of amplification output from high to low, it becomes area D, area C, area B, and area A.

[0063] In normal amplification operation, the pulse width of the pulse laser input to the laser amplifier and the pulse width of the pulse laser emitted from the laser amplifier do not change significantly, so the pulse width of the pulse laser input to the laser amplifier in this case becomes 5ns to 30ns. That is, in the case of normal amplification operation, it can be seen that Figure 4 The action is performed on the dotted line K.

[0064] In contrast, in Embodiment 1, the pulse width of the pulsed laser 25 incident on the laser amplifier 30 is 15 ns to 200 ns, so that the amplification operation can be performed in any of the regions B, C, and D. Regions B, C, and D are regions located on the right side of the dotted line K, so in Embodiment 1, an amplified output greater than or equal to the output obtained by the normal amplification operation can be obtained. Next, the pulse width τ of the pulsed laser 25 incident on the laser amplifier 30 is changed to τ. p is called the incident pulse width τ p .

[0065] In the first embodiment, the incident pulse width τ p In the region C and region D from 30 ns to 200 ns, the energy η is extracted. ext >0.75. In the usual amplification operation, Figure 4 The dotted line K is a part of area A and area B, so the energy η is extracted. ext No more than 0.75. Therefore, at the incident pulse width τ p When the time is 30 ns to 200 ns, an amplified output higher than the output obtained by a normal amplification operation can be obtained.

[0066] In the first embodiment, the incident pulse width τ p Extract energy η from the region D between 50ns and 200ns ext >0.9. Therefore, at the incident pulse width τ p When the current is 50ns to 200ns, a higher amplification output can be obtained than the output obtained by the normal amplification operation. Figure 2 As shown, in this region, the energy η is extracted ext Relative to the incident pulse width τ p Saturation, relative to the incident pulse width τ p The change in the amplified output becomes smaller with the change in the incident pulse width τ. Therefore, even if the pulse shortening during amplification described below occurs, the amplification factor is not easily reduced in this region. p In the region of 50 ns to 200 ns, amplification is performed while suppressing the decrease in amplification factor to a minimum.

[0067] In addition, the incident pulse width τ pIt can also be set as the extraction energy η ext >0.5 is greater than or equal to 15ns. Preferably, the extraction energy η can be set to ext >0.6 is greater than or equal to 20ns. It is further preferred that the extraction energy η ext >0.75 is greater than or equal to 30ns. It is further preferred that the extraction energy η ext >0.8 is greater than or equal to 40ns. It is further preferred that the extraction energy η ext >0.9 is greater than or equal to 50ns.

[0068] like Figure 2 As shown, at the incident pulse width τ p When the time is greater than or equal to 200ns, the energy η is extracted ext is approximately equal to 1. In this region, even if the incident pulse width τ p Become longer, extract energy η ext The value of does not increase, and the amplified output cannot be significantly improved. On this basis, the incident pulse width τ p The longer the incident pulse width τ is, the lower the peak value of the pulse laser 35 output from the laser amplifier 30 is. Therefore, in order to prevent the decrease in the peak value of the laser pulse and obtain a high amplified output, it is preferable that the incident pulse width τ is p The peak value of the laser pulse is reduced in detail later.

[0069] Next, the pulse shortening effect caused by the change in the pulse waveform during amplification in the laser amplifier 30 will be described. Figure 5 An example of the change process of the pulse waveform when a super-Gaussian laser pulse is amplified is shown. Here, only the change of the pulse shape is focused on, so Figure 5 The maximum values ​​of the vertical axes of the pulse waveforms shown are equal, but in fact, the maximum values ​​of the vertical axes increase continuously with amplification. The horizontal axis t represents time, and the vertical axis I represents intensity. Hereinafter, t is used as a symbol to represent time, and I is used as a symbol to represent intensity. If a laser pulse is injected into the laser amplifier 30, the energy accumulated in the amplifying medium is first consumed by the front part of the laser pulse. Therefore, the amplification factor of the rear part of the laser pulse amplified by the remaining energy is lower than the amplification factor of the front part of the laser pulse. Here, the front part of the laser pulse refers to the part that is first injected into the laser amplifier 30, and refers to the part that is not injected into the laser amplifier 30. Figure 5 The front part of the laser pulse first consumes the energy accumulated in the laser amplifier 30, thus Figure 5 The laser pulse shown becomes sharper as it is amplified, and as a result, an outgoing laser pulse 35 having a shorter pulse width than the incident laser pulse 25 is obtained.

[0070] In contrast, Figure 6 1 is a diagram showing an example of the change process of the pulse waveform during amplification when the incident laser pulse 25 is set to a normal Gaussian waveform. In the case of the Gaussian shape, the energy consumption of the front part of the laser pulse is small compared with the super Gaussian shape, so it is not easy to sharpen the laser pulse. As a result, the shortening effect of the laser pulse of the degree obtained when the super Gaussian shape is injected cannot be obtained.

[0071] As described above, when a super-Gaussian pulse waveform is used as the incident laser pulse 25, the pulse laser 25 having a pulse width of 15 ns to 200 ns output from the laser oscillator 20 is incident on the laser amplifier 30 and amplified, thereby outputting a pulse laser 35 having a pulse width of 5 ns to 30 ns.

[0072] exist Figure 7 An example of the shape of a super-Gaussian laser pulse is shown. When the time t=t0 is set as the symmetry center, the maximum intensity is set as I0, and the half-value full width is set as τ p , when the coefficient is set to P, the super Gaussian function I sg (t) can be expressed as a function of time t as shown in equation (1).

[0073] [Formula 1]

[0074]

[0075] In formula (1), when the coefficient P is 1, the super-Gaussian function is consistent with the Gaussian function. Figure 7 As shown, the rise time τ b It is defined as the time from when the intensity I rises from 0.1I0 to 0.9I0. In other words, in the pulse time waveform, the time from when the intensity I rises to 10% of the maximum intensity of the pulse light to when it rises to 90% of the maximum intensity is called the rise time τ. b Similarly, the time from when the intensity I decreases to 90% of the maximum intensity of the pulse light to when it decreases to 10% of the maximum intensity is called the fall time. p and rise time τ b The ratio is set to T r =τ b / τ p , then the ratio T r The relationship between the coefficient P becomes Figure 8 That is, the larger the coefficient P becomes, the greater the ratio T r For example, at the ratio T r When it is close to 0.72, the coefficient P is close to 1, thus indicating a Gaussian shape. rWhen it is close to 0.35, it means that the pulse waveform is a super-Gaussian shape with P = 2. r When <<0.72, P becomes a value sufficiently larger than 1, indicating that the pulse waveform is a waveform close to a rectangular shape.

[0076] When the incident laser pulse 25 has any shape other than super-Gaussian, for example, an asymmetric laser pulse having different rise time and fall time, T r Defined as the full width at half maximum τ p and rise time τ b The ratio (T r =τ b / τ p ). In the description of the present invention, a super-Gaussian shape with equal rise time and fall time is used for explanation, but the shape of the pulse is not limited. In addition, even a pulse waveform of any shape such as an asymmetric laser pulse can obtain the same effect as a symmetric pulse.

[0077] like Figure 6 As shown, in the ratio T r In the case of a waveform close to a Gaussian shape close to 0.72, a significant pulse shortening effect cannot be obtained, but at a ratio T r When the ratio T is less than 0.72 and the waveform is close to the super-Gaussian shape, a significant pulse shortening effect can be obtained. r As the pulse waveform gets smaller, it approaches a rectangular shape, resulting in a greater pulse shortening effect.

[0078] The change in pulse shape that leads to pulse shortening appears more significantly when the extraction energy of the laser amplifier 30 relative to the incident laser pulse 25 is large, in other words, when the amplification factor of the laser amplifier 30 is large. Fig. 9 An example of the change in pulse shape and pulse intensity during the pulse amplification process is shown. Fig. 9 In the case where the extraction energy from the laser amplifier 30 relative to the incident laser pulse 25 is small, for example, Fig. 9 When the laser pulse 53 shown on the left side of FIG. 1 is incident on the laser amplifier 30 and amplified, as shown from Fig. 9 The second laser pulse 54 shown from the left or from Fig. 9 The back pedestal 55 remains in the pulse waveform, as shown in the third figure from the left of FIG. 54. The back pedestal 55 refers to the pedestal-shaped portion that appears behind the main pulse 56. The reason for this is that in the laser pulse 54 or the laser pulse 57, the energy portion extracted from the laser amplifier 30, that is, the main pulse 56, is small, and the contribution of the energy portion of the incident laser pulse 53 becomes large. In contrast, when the amplification factor of the laser amplifier 30 is high, such as from Fig. 9As in the laser pulse 58 shown in the fourth figure from the left, the energy portion extracted from the laser amplifier 30, namely the main pulse 56, is large, so a pulse waveform without a back pedestal 55 can be obtained.

[0079] In order to obtain EUV light exceeding 250W in the EUV light generator 40, the amplification factor of the laser amplifier 30 is preferably greater than or equal to 1000 times. The reason is explained below. When the EUV light output from the extreme ultraviolet light generator 100 is greater than 250W, the number of wafers that can be processed by the exposure device per hour becomes larger than 125 wafers suitable for mass production. Therefore, in order to meet the EUV light output > 250W, the output of the pulsed laser 35 output from the laser amplifier 30 is greater than 20kW, so that the EUV light generator that is most suitable for the exposure device can be obtained. In the case where the laser oscillator 20 is a Q-switched cavity dumping oscillator, its output is limited to tens of W due to the light resistance of the electro-optical element 22. The output of the laser oscillator 20 is tens of W, and an output greater than 20kW is required in the output of the laser amplifier 30, so the amplification factor of the laser amplifier 30 is preferably greater than or equal to 1000 times. When the laser amplifier 30 is a multi-stage amplifier, the value obtained by dividing the output of the laser pulse output from the final stage by the output of the laser pulse before entering the first-stage amplifier is preferably equal to or greater than 1000 times.

[0080] In addition, it is not limited to outputting laser pulses having a single wavelength from the laser oscillator 20, and laser pulses having multiple wavelengths may also be output. A CO2 laser that outputs multiple wavelengths is called a multi-line CO2 laser. By outputting multiple wavelengths, the influence of the reduction in amplification factor caused by the rotational relaxation of the laser amplifier 30 can be suppressed, and a high amplified output can be obtained. These multiple wavelengths are preferably transition wavelengths between rotational energy levels of the CO2 laser. For example, on the basis of the wavelength P(20) for maximum output obtained by the CO2 laser, laser pulses such as P(16), P(18), P(22), and P(24) may also be output.

[0081] exist Figure 3 In the example, the pulse laser light 25 of 15 ns to 200 ns injected into the laser amplifier 30 shows the ratio T r <0.72. The super-Gaussian laser pulse as described above can be realized, for example, by the aforementioned Q-switch cavity dump oscillation. In the Q-switch cavity dump oscillation, if the resonator length is set to L and the speed of light is set to c, the pulse width τ of the output laser pulse p It is approximately equal to 2L / c. Therefore, the resonator length L may be selected so that 2L / c becomes 15 ns to 200 ns. Fig.10This is a diagram illustrating the generation of super-Gaussian pulses caused by Q-switch cavity dump oscillation. Fig.10 As shown in the upper part of the figure, the switching time of the electro-optical element 22, that is, the time for the loss in the resonator to switch from a low-loss state to a high-loss state, is shorter than the pulse width τ p When the pulse is short enough, the laser pulse output by the Q switch cavity dump oscillation rises sharply, such as Fig.10 As shown in the lower part, we get T r Super Gaussian shape of <0.72.

[0082] In contrast, Fig.11 As shown in the upper part of the figure, the switching time of the electro-optical element 22 is, for example, a pulse width τ p When the laser pulse is about half of the original value, the rapid rise of the laser pulse is hindered by the gentle switching of the electro-optical element 22. As a result, the laser pulse waveform is as follows: Fig.11 As shown in the lower part of , it becomes a shape close to a Gaussian shape.

[0083] like Figure 5 and Figure 6 As described in the description, the shortening effect of the laser pulse in the laser amplifier 30 depends not only on the shape of the incident laser pulse 25, but also on its pulse width τ p The reason is that, Figure 4 As shown, the pulse width τ of the incident laser pulse 25 p Accordingly, the normalized extraction energy η ext Different. In extracting energy η ext If the laser amplifier 30 is too small, the energy in the laser amplifier 30 cannot be fully extracted, so the front portion of the laser pulse is not easily sharpened, and the laser pulse is not easily shortened. Figure 4 If the regions are arranged in the order in which the shortening of the laser pulse is likely to occur, the order is regions D, C, B, and A. In the structure involved in the first embodiment, the extraction energy η can be increased compared to the usual amplification operation. ext , therefore, the obtained pulse shortening effect can also be increased.

[0084] Fig.12 and Fig.13 An example of pulse shortening when laser pulses with different pulse widths are incident on the laser amplifier 30 is shown. Fig.12 The example shows a case where the pulse width of the incident laser pulse 25 is longer than the pulse width of the emitted laser pulse 35. In this case, the emitted laser pulse 35 rises sharply and falls gently. Fig.13 The pulse width ratio of the incident laser pulse 25 is shown as an example Fig.12 The case where the incident laser pulse 25 is longer is shown. Fig.13 The outgoing laser pulse 35 shown is Fig.12The outgoing laser pulses 35 shown have the same pulse width, but Fig.13 The outgoing laser pulse 35 shown has a Fig.12 The outgoing laser pulse 35 shown has a longer fall time. Fig.12 The output of the outgoing laser pulse 35 is shown as Fig.13 When the output of the outgoing laser pulse 35 is the same as shown, Fig.13 The peak output of the outgoing laser pulse 35 shown becomes smaller. As shown above, when the pulse width τ of the incident laser pulse 25 p When the time is greater than 200ns, the energy η is extracted ext Therefore, even if the pulse width τ of the incident laser pulse 25 is p If the pulse width of the incident laser pulse 25 is made longer than 200 ns, the amplified output will not change significantly. p If the pulse width τ of the incident laser pulse 25 is increased, the fall time of the emitted laser pulse 35 will be increased. p If the pulse width τ of the incident laser pulse 25 is increased by 200 ns, the amplified output will not change significantly, the fall time will be longer, and the peak output will decrease. p By setting the time to be 200 ns or less, both a high amplified output and a pulse with a high peak value can be achieved.

[0085] As described above, in Embodiment 1, a pulse laser having a half-value width of 15 ns to 200 ns is oscillated in the laser oscillator 20 and injected into the laser amplifier 30, and the amplifier laser active medium is passed through the laser amplifier 30, thereby shortening the pulse width to a pulse laser having a half-value width of 5 ns to 30 ns and outputting the pulse laser. Therefore, in Embodiment 1, a pulse laser having a half-value width of 5 ns to 30 ns, which is most suitable for emitting high-output extreme ultraviolet light, and having a high output of 20 kW or more can be emitted.

[0086] In the first embodiment, the rise time τ is the time from when the intensity of the pulsed laser light 25 incident on the laser amplifier 30 rises from 10% of the maximum intensity to when it rises to 90% of the maximum intensity. b divided by the full width at half maximum τ of the pulse laser 25 incident on the laser amplifier 30 p The obtained value T r (=τ b / τ p ) is less than 0.72, so a significant pulse shortening effect can be obtained.

[0087] Implementation method 2.

[0088] Fig.14FIG. 2 is a diagram showing the structure of an extreme ultraviolet light generating device 200 having a laser amplifying device 110 according to Embodiment 2. Fig.14 In the embodiment, the laser amplification device 110 includes a laser oscillator 20, a transmission optical system 120, and a laser amplifier 30. The transmission optical system 120 includes a polarization beam splitter 70, an electro-optical element 71, a polarization beam splitter 72, a beam splitter 73, a waveform measurement sensor 74, and a reflector 75. The electro-optical element 71, the polarization beam splitter 70, and the polarization beam splitter 72 function as both an optical isolator and a pulse waveform shaper. The waveform measurement sensor 74 measures the waveform I of the pulsed laser light before it is injected into the laser amplifier 30. in Carry out determination.

[0089] use Fig.15 , Fig.16 and Fig.17 , the operation of the electro-optical element 71, the polarization beam splitter 70, and the polarization beam splitter 72 as an optical isolator will be described. Fig.15 Outgoing light travelling from the laser oscillator 20 to the laser amplifier 30 is shown. Fig.16 Return light traveling from the laser amplifier 30 to the laser oscillator 20 is shown. Fig.17 2 is a diagram showing a timing chart of applied voltage for rotating polarization by 90 degrees by the electro-optical element 71 and a timing chart of laser pulses output from the laser oscillator 20. Fig.17 The area with diagonal shadow H in Fig.17 The applied voltage corresponds to the period during which it is turned on.

[0090] A voltage for rotating the polarization by 90 degrees is applied to the electro-optical element 71 in synchronization with the repetition frequency of the laser pulse output from the laser oscillator 20. Fig.15 As shown, the outgoing light passing through the electro-optical element 71 is only Fig.17 During the on-time of the applied voltage shown in the upper part of , the polarization 77 in the vertical direction is rotated 90 degrees to the polarization 78 in the horizontal direction. As a result, Fig.17 As shown in the lower part of , only the pulse with the oblique line shadow H is cut out and passes through the polarization beam splitter 72, and the rest is reflected by the polarization beam splitter 72.

[0091] The return light from the laser amplifier 30 side is, for example, the self-excited oscillation light of the laser amplifier 30. The return light from the laser amplifier 30 side cannot be Fig.17 The applied voltage of the electro-optical element 71 shown in the upper part of the laser amplifier 30 is synchronized, so that even if the light passes through the electro-optical element 71, the polarization does not rotate and the horizontal polarization 78 is maintained. As a result, the return light from the laser amplifier 30 side is as follows: Fig.16As shown, the light does not pass through the polarization beam splitter 70 and does not return to the laser oscillator 20. Therefore, the laser oscillator 20 is not affected by the return light and can oscillate stably. In addition, if the same principle is used, the electro-optical element 71 and the polarization beam splitters 70 and 72 can also suppress the parasitic oscillation generated between the laser oscillator 20 and the laser amplifier 30. Fig.14 In the figure, the polarization beam splitters 70 and 72 are illustrated, but an optical element having the same function, such as ATFR (Absorbing thin film reflector), may be used.

[0092] Fig.18 The operation of the electro-optical element 71, the polarization beam splitter 70, and the polarization beam splitter 72 as a pulse shaper is exemplified. Fig.18 The area with diagonal shadow H in the Fig.17 As shown, this corresponds to a period during which the applied voltage for rotating the polarization by 90 degrees in the electro-optical element 71 is turned on. Figure 3 The laser pulse with a pulse width of 15 ns to 200 ns is shown as an example of T r <0.72. However, in the case of a laser pulse with this super-Gaussian shape, Fig.18 As shown on the left side of FIG. 1 , a pedestal 15 may appear before the main pulse 14, and a post-pulse 16 may appear after the main pulse 14. If the pedestal 15 or the post-pulse 16 enters the laser amplifier 30 and consumes the energy in the laser amplifier 30, the amplification of the main pulse 14 is hindered. Fig.18 As shown by the oblique line shadow H, by rotating the polarization of the main pulse 14 by 90 degrees in the electro-optical element 71 and cutting it out, the pulse measured by the waveform measurement sensor 74 is as follows: Fig.18 As shown on the right side of FIG, the pedestal 15 and the post pulse 16 are removed and only the main pulse 14 is included. Fig.18 Since the pedestal 15 and the post-pulse 16 are removed from the pulse shown on the right side of FIG. 1 , the pedestal 15 and the post-pulse 16 do not consume energy in the laser amplifier 30 , and the amplified output of the main pulse 14 is improved.

[0093] exist Fig.19 The second example of pulse shaping is shown in FIG. Fig.19 The area with diagonal shadow H is as follows Fig.17 As shown in FIG. 1 , this corresponds to the period during which the applied voltage for rotating the polarization by 90 degrees in the electro-optical element 71 is turned on. Fig.19In the embodiment, the pulse width of the applied voltage for rotating the polarization by 90 degrees in the electro-optical element 71 is controlled, so that the laser pulse 19 with a pulse width of 15ns to 200ns is cut out from the laser pulse 18 emitted by the electro-optical element 71. As a result, as described in Embodiment 1, the pulse width of the laser pulse output from the laser amplifier 30 can be set to 5ns to 30ns, and the EUV light output in the EUV light generator 40 can be improved. In addition, when the cut laser pulse is rectangular, a more significant shortening effect of the pulse of the laser amplifier 30 is obtained.

[0094] exist Fig. 20 The third example of pulse shaping is shown. Fig. 20 The area with diagonal shadow H in the Fig.17 As shown, this corresponds to the period during which the applied voltage for rotating the polarization by 90 degrees in the electro-optical element 71 is turned on. When the laser oscillator 20 is oscillated by Q-switching or the like, sometimes Fig. 20 Therefore, the electro-optical element 71 cuts out only the area with the oblique line shadow H, that is, the rear part of the laser pulse 12, so that the waveform measurement sensor 74 can detect the Gaussian shape of the laser pulse 12 on the left side. Fig. 20 The laser pulse 13 shown on the right side of the pulse is measured. The laser pulse 13 has a shape in which the intensity of the front part of the pulse is greater than that of the rear part, and the front part is sharp. If the laser pulse 13 of the above shape is passed through the laser amplifier 30, the sharpening of the front part of the pulse is significantly caused by amplification, and a more significant pulse shortening effect is obtained.

[0095] Fig.21 It means having Fig.14 FIG. 2 is a diagram showing a modified example of the extreme ultraviolet light generating device 200 of the laser amplifying device 110. Fig.21 In, relative to Fig.14 The extreme ultraviolet light generating device 200 shown in the figure is additionally provided with a spectrometer 81, a waveform measuring sensor 82 and a reflector 99. A portion of the laser pulse output from the laser amplifier 30 is taken out by the spectrometer 81, and its waveform is measured by the waveform measuring sensor 82. In the waveform measuring sensor 82, the waveform I of the pulsed laser output from the laser amplifier 30 is measured. out By measuring the waveform I out Monitor and judge the waveform I out Is it the laser pulse that is most suitable for conversion into EUV light?

[0096] Fig. 22 The laser pulse shown on the left side of shows the waveform of the laser pulse incident on the laser amplifier 30 measured by the waveform measurement sensor 74. Fig. 22The laser pulse shown on the right side of FIG. 8 shows an example of the waveform of the laser pulse emitted from the laser amplifier 30 measured by the waveform measurement sensor 82. Fig. 22 As shown in FIG. 1 , the laser pulse before entering the laser amplifier 30 may have a waveform including a back pedestal 83 in the rear portion of the main pulse after being amplified in the laser amplifier 30 .

[0097] Therefore, the pulse waveform measured by the waveform measuring sensor 82 is monitored, such as Fig.23 The electro-optical element 71 is adjusted in such a way that the laser pulse waveform after amplification has no back base, as shown in the laser pulse 85 on the right side of FIG. Fig.23 The laser pulse 84 shown on the left side is cut out. By using the waveform measurement sensor 82, it is possible to achieve Fig.23 The optimal laser pulse waveform shown on the left side of the cutout can improve the output of the EUV light emitted by injecting the optimal laser pulse into the EUV light generator 40. Here, the adjustment is made in such a way that the back base does not appear, but the laser pulse can also be cut out by adjusting the electro-optical element 71 in such a way that the laser pulse waveform with improved EUV light output is obtained.

[0098] As described above, in the second embodiment, the period during which the polarization rotation function of the electro-optical element 71 is turned on is controlled, so that the electro-optical element 71, the polarization beam splitter 70, and the polarization beam splitter 72 function as an optical isolator, thereby allowing the laser oscillator 20 to stably oscillate without being affected by the return light. In addition, by controlling the period during which the polarization rotation function of the electro-optical element 71 is turned on, the electro-optical element 71, the polarization beam splitter 70, and the polarization beam splitter 72 function as a pulse shaper, thereby removing the pedestal 15 or the after pulse 16 that appears before and after the main pulse 14, or shortening and shaping the pulse width, and improving the amplification performance of the laser amplifier 30. In addition, the laser pulse input and output to the laser amplifier 30 is monitored, and the electro-optical element 71 is controlled using the monitoring results, so that the optimal laser pulse can be emitted to the EUV light generator 40.

[0099] Implementation method 3.

[0100] Fig.24 FIG. 1 is a diagram showing the structure of an extreme ultraviolet light generating device 300 having a laser amplifying device 130 according to Embodiment 3. Fig.24 In the embodiment, the laser amplification device 130 includes a laser oscillator 20, a reflection mirror 27, and a multi-channel laser amplifier 31. Fig.24 middle, Figure 3 The laser amplifier 30 in the extreme ultraviolet light generating device 100 is replaced by a multi-channel laser amplifier 31. Figure 3In the case of an incident laser pulse 25, the energy density E in The saturation energy density E of the laser amplifier 30 is s When the energy density E of the incident laser pulse 25 is sufficiently large, the energy accumulated in the laser amplifier 30 can be fully extracted, and a high amplified output can be obtained. in Less than the saturation energy density E of the laser amplifier 30 s In the case of , the energy accumulated in the laser amplifier 30 cannot be fully extracted. As a result, the pulse shortening effect cannot be fully obtained. Therefore, when the energy density E of the incident laser pulse 25 is in Less than the saturation energy density E of the laser amplifier 30 s In the case of Fig.24 As shown, by using a multi-channel laser amplifier 31, the energy extraction efficiency can be further improved. As a result, a high amplification output can be obtained, and as a result, a high EUV light output can be obtained. Fig.24 A five-path amplifier having five paths is exemplified in FIG. 1 , but the number of paths may be a number greater than or equal to two, and the number of paths is not limited to five.

[0101] The energy density E of the incident laser pulse 25 in Less than the saturation energy density E of the laser amplifier 30 s In such cases, if the gas pressure of the laser amplifier 30 is optimized, a higher amplified output and a pulse waveform most suitable for high EUV light output can be obtained. Fig.25 In the extreme ultraviolet light generating device 400, the laser amplifier 33 has a gas pressure regulating mechanism 32 for regulating the gas pressure of the laser gas. Figure 3 The extreme ultraviolet light generating device 100 shown is the same. In a CO2 laser, the saturation energy density E s Increases in direct proportion to the gas pressure N. Therefore, if the gas pressure N is reduced, the saturation energy density E s decreases. On the contrary, if the gas pressure N is increased, the saturation energy density E s Increase. The energy density E of the incident pulse in At the same time, by adjusting the gas pressure N, the saturation energy density E can be s By making adjustments, the energy extracted from the laser amplifier 33 can be adjusted.

[0102] Fig.26 This is a graph showing an example of the amplification characteristics when the gas pressure N of the laser amplifier 33 is changed. Suppose the saturation energy density at the initial gas pressure is E s0 The saturation energy density when the gas pressure is reduced from the initial gas pressure is set to Es1 The saturation energy density when the gas pressure is increased from the initial gas pressure is set to E s2 .like Fig.26 As shown, if the gas pressure is reduced from the initial gas pressure, it becomes E s1 <E s0 , so the amplification characteristic curve 34 changes as shown in the curve 37. At this time, relative to the energy density E of the incident pulse in The increase of the output E out The saturation characteristics of the gas are more prominent. In contrast, if the gas pressure is increased from the initial gas pressure, it becomes E s0 <E s2 , so the amplification characteristic curve 34 changes as shown in the curve 38. At this time, relative to the energy density E of the incident pulse in The increase of the output E out The saturation characteristic of becomes subtle and approaches a linear characteristic. Therefore, when the energy density E of the incident laser pulse 25 in Less than the saturation energy density E of the laser amplifier 33 s When the energy accumulated in the laser amplifier 33 cannot be fully extracted, the saturation energy density E can be reduced by reducing the gas pressure. s , the amplified output can be increased. On the contrary, when it is desired to reduce the amplified output, it is sufficient to increase the gas pressure. If the gas pressure is changed, sometimes the impedance matching between the discharge circuit of the laser amplifier 33 and the amplifier cannot be achieved. In the case of impedance mismatch, the power used during discharge, that is, the discharge power, cannot be effectively used. Therefore, if the impedance matching is achieved, the discharge power can be effectively used, and the amplified output can be further improved.

[0103] In addition, when the gas pressure is reduced, in addition to increasing the amplified output, the extracted energy from the amplifier increases, thereby achieving the effect of significantly shortening the pulse. Furthermore, if the saturated amplification characteristics such as those in the graph 37 are utilized, the stability of the repetitive pulses output from the laser oscillator 20 is also improved. This is described below. Fig. 27 FIG. 3 shows a case where the repetitive pulses output from the laser oscillator 20 have intensity fluctuations. If the above-mentioned fluctuations exist, as shown in FIG. 37, the output saturated laser amplifier is used for amplification, and the output saturated laser amplifier is used for amplification. Fig.28As shown, the fluctuation of the amplified repetitive pulse is reduced. As a result, the pulse stability can be improved. As described above, if the gas pressure is reduced by the gas pressure adjustment mechanism 32, the three effects of increased amplified output, significant pulse shortening, and improved pulse stability can be obtained at the same time. In this embodiment, if the gas pressure is adjusted within the range of the gas pressure where the rotation relaxation time becomes a few ns, the above three effects can be expected. The rotation relaxation time becomes a few ns. In typical cases, since it is about 20 Torr to 100 Torr, the gas pressure can be adjusted within the range of 20 Torr to 100 Torr.

[0104] The improvement of the pulse stability of the incident pulse is obtained by the amplification characteristic of the saturation tendency. Therefore, for example, when the energy density E of the incident laser pulse 25 is in The saturation energy density E of the laser amplifier 30 is s When it is sufficiently large, even in the case of the multi-channel laser amplifier 31, the same effect of improving the pulse stability can be obtained.

[0105] As described above, in Embodiment 3, the multi-channel laser amplifier 31 is used, so that the energy extraction efficiency can be further improved, and a high amplified output can be obtained. In addition, the gas pressure of the laser gas of the laser amplifier 33 is adjusted to be lowered, so that the saturation energy density E of the laser amplifier can be reduced. s , which can improve the amplification output of the laser amplifier.

[0106] Implementation method 4.

[0107] Fig.29 It means from Fig.14 or Fig.21 FIG. 1 is a diagram of an estimation device 90 for estimating the pulse waveform of the pulse laser 35 outputted from the laser amplifier 30 of the laser amplification device 110 shown in FIG. The estimation device 90 includes a data acquisition unit 91 and an estimation unit 92. The data acquisition unit 91 acquires the pulse waveform of the pulse laser 35 outputted from the laser amplifier 30 of the laser amplification device 110. Fig.14 or Fig.21 The laser pulse waveform I before amplification measured by the waveform measurement sensor 74 is shown in FIG. in The inference unit 92 uses the trained model storage unit 93 to infer the laser pulse waveform amplified by the laser amplifier 30. That is, the laser pulse waveform I obtained by the data acquisition unit 91 is input to the trained model stored in the trained model storage unit 93. in , so that the amplified pulse waveform I estimated by the estimation unit 92 can be obtained from the estimation unit 92 oif The inference device 90 can be used to infer the amplified pulse waveform I oifThe pulse waveform before amplification is changed by the method that is most suitable for emitting 5ns to 30ns pulses of EUV light. Fig.14 The pulse shaper composed of the electro-optical element 71, the polarization beam splitter 70 and the polarization beam splitter 72 shown is optimized. This optimization enables emission of high-output EUV light.

[0108] Fig.30 1 is a flowchart showing the processing procedure of the estimation device 90. In step S1, the data acquisition unit 91 acquires the pulse waveform I before amplification measured by the waveform measurement sensor 74. in In step S2, the inference unit 92 inputs the pulse waveform I into the trained model stored in the trained model storage unit 93. in , and the inferred amplified pulse waveform I is obtained oif In step S3, the inference unit 92 calculates the pulse waveform I obtained by the trained model. oif The output is sent to the EUV light generator 200. In step S4, the EUV light generator 200 uses the inferred pulse waveform I oif The amplified pulse is optimized to a laser pulse light having a pulse width of 5ns to 30ns. As a result, high-output EUV light can be emitted.

[0109] exist Fig.31 The learning device 94 is shown as an example, and the learning device 94 generates Fig.29 The learning device 94 includes a data acquisition unit 95, a model generation unit 96, and a trained model storage unit 93. In this embodiment, the learning algorithm used by the model generation unit 96 is explained as a case of teacher learning, but a well-known algorithm such as unsupervised learning and reinforcement learning can also be used. The data acquisition unit 95 acquires the trained model from Fig.21 The laser pulse waveform I before amplification measured by the waveform measurement sensor 74 is shown in FIG. in and the amplified laser pulse waveform I measured by the waveform measurement sensor 82 out .

[0110] The model generation unit 96 is based on the laser pulse waveform I output from the data acquisition unit 95. in and laser pulse waveform I out The generated learning data is the output I of the amplified pulse waveform. oif That is, generate in and I out For output I oif Here, the learning data is the input I in and I out Data that are related to each other.

[0111] Fig.32 1 is a flowchart showing the processing procedure of the learning device 94. In step S10, the data acquisition unit 95 acquires the input I in and I out In addition, it is not necessary to obtain input I in and I out , as long as the input I in and I out In step S11, the model generation unit 96 generates the model according to the input I obtained by the data acquisition unit 95. in and I out The learning data created by the combination of the output I oif Learning is performed to generate a trained model. In step S12 , the trained model storage unit 93 stores the trained model generated by the model generation unit 96 .

[0112] The model generation unit 96 may generate the output I according to the learning data created for a plurality of EUV light generating devices. oif For example, learning data can be obtained from multiple EUV light generators used in the same area, or from multiple EUV light generators operating independently in different areas. In addition, the EUV light generator that collects learning data can be added to the object or removed from the object. In addition, the output I of a certain EUV light generator can be oif The learning device that has been learned is applied to other EUV light generating devices, and the output I of other EUV light generating devices is oif Relearn and update.

[0113] In addition, as a learning algorithm used by the model generation unit 96, deep learning that learns the extraction of feature quantities themselves can also be used, and machine learning can also be performed according to other well-known methods such as genetic programming, functional logic programming, support vector machines, etc.

[0114] exist Fig.33 In the example, the learning device 97 combines an input set 98 including a plurality of different parameter values ​​with an input I out As learning data, the output I oif The input set 98 includes the pulse waveform I before amplification as a parameter. in, the gas pressure of the laser amplifier 30, and the number of paths in the laser amplifier 30. It is sufficient to input the elements that can change the waveform of the amplified pulse described in Embodiments 1 to 3 to the input set 98. For example, the discharge power of the laser amplifier 30, the output of the laser oscillator 20, and other elements can be added to the input set 98.

[0115] The model generation unit 96 generates a model based on the input set 98 and the input I acquired by the data acquisition unit 95. out The learning data created by the teacher learning is the amplified pulse waveform, that is, the output I oif The trained model storage unit 93 stores the trained model generated by the model generation unit 96 .

[0116] When the trained model learned by the learning device 97 is applied to the inference device 90, Fig.29 The data acquisition unit 91 shown replaces the input I in Instead, the input set 98 is obtained. Fig.29 The inference unit 92 infers the pulse waveform after amplification by the laser amplifier 30 using the trained model stored in the trained model storage unit 93. That is, by inputting the input set 98 acquired by the data acquisition unit 91 to the trained model, the amplified pulse waveform I estimated by the inference unit 92 can be obtained. oif The estimated amplified pulse waveform I is output from the estimation unit 92. oif The method of obtaining the pulse of 5ns to 30ns that is most suitable for emitting EUV light is to optimize the pulse waveform before amplification, the gas pressure of the laser amplifier 30, the number of paths in the laser amplifier 30, and other factors. Through this optimization, high-output EUV light can be emitted. In addition, by inputting I in By setting the input set 98 to include a plurality of factors, the plurality of factors can be optimized, and higher output EUV light can be emitted.

[0117] The structure shown in the above embodiment is an example of the content of the present invention, and can also be combined with other well-known technologies. In addition, part of the structure can be omitted or changed within the scope of the gist of the present invention.

[0118] Description of the label

[0119] 10, 110, 130 laser amplification device, 20 laser oscillator, 21 laser active medium, 22, 71 electro-optical element, 23, 70, 72 polarization beam splitter, 24, 26 resonator mirror, 25 pulse laser (incident laser pulse), 30, 33 laser amplifier, 31 multi-channel laser amplifier, 32 gas pressure adjustment mechanism, 35 pulse laser (outgoing laser pulse), 40 EUV light generator, 41 droplet generator, 42 collector mirror, 50 EUV light, 60 intermediate focusing point, 70, 72 polarization beam splitter, 74, 82 waveform measurement sensor, 90 inference device, 94, 97 learning device, 100, 200, 300, 400 extreme ultraviolet light generating device (EUV light generating device), 120 transmission optical system.

Claims

1. A laser amplification device, characterized in that: have: A laser oscillator having a first laser active medium, the first laser active medium having a mixed gas including carbon dioxide gas, the laser oscillator oscillating a pulse laser having a full width at half maximum of between 15 ns and 200 ns; as well as A laser amplifier having a second laser active medium having a mixed gas containing carbon dioxide gas, wherein the pulsed laser light oscillated by the laser oscillator is shortened to a pulsed laser light having a half-value width between 5 ns and 30 ns by passing through the second laser active medium and outputted, The value obtained by dividing the rise time, which is the time from when the intensity of the pulsed laser light outputted from the laser oscillator rises to 10% of the maximum intensity to when it rises to 90% of the maximum intensity, by the full width at half maximum of the pulsed laser light outputted from the laser oscillator is less than 0.

72.

2. The laser amplification device according to claim 1, characterized in that: Also features: at least one polarization beam splitter, including a first polarization beam splitter, the first polarization beam splitter being disposed in an optical path of the pulsed laser between the laser oscillator and the laser amplifier; and The electro-optical element is provided in the optical path of the pulse laser light between the first polarization beam splitter and the laser oscillator, and performs 90-degree polarization control so that only a part of the incident pulse laser light can pass through the first polarization beam splitter.

3. The laser amplification device according to claim 2, characterized in that: The electro-optical element performs the 90-degree polarization control so as to shape the pulse width so that the first half and the second half of the incident pulse laser light are reflected by the first polarization beam splitter and only the central portion is transmitted.

4. The laser amplification device according to any one of claims 1 to 3, characterized in that: The gas pressure of the mixed gas is between 20 Torr and 100 Torr.

5. The laser amplification device according to any one of claims 1 to 3, characterized in that: The laser amplifier has a plurality of optical paths, ie, routes, from when the pulsed laser light is incident on the second laser active medium to when the pulsed laser light is emitted from the second laser active medium.

6. The laser amplification device according to claim 4, characterized in that: The laser amplifier has a plurality of optical paths, ie, routes, from when the pulsed laser light is incident on the second laser active medium to when the pulsed laser light is emitted from the second laser active medium.

7. The laser amplification device according to any one of claims 1 to 3, characterized in that: Also features: a data acquisition unit that acquires a first signal indicating a time-series waveform of the intensity of the pulsed laser light incident on the laser amplifier and a second signal indicating a time-series waveform of the intensity of the pulsed laser light emitted from the laser amplifier; a learning unit that performs learning for estimating a time-series waveform of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier, based on the first signal and the second signal; as well as An estimating unit estimates, based on the result learned by the learning unit, a timing signal of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier.

8. The laser amplification device according to claim 4, characterized in that: Also features: a data acquisition unit that acquires a first signal indicating a time-series waveform of the intensity of the pulsed laser light incident on the laser amplifier and a second signal indicating a time-series waveform of the intensity of the pulsed laser light emitted from the laser amplifier; a learning unit that performs learning for estimating a time-series waveform of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier, based on the first signal and the second signal; as well as An estimating unit estimates, based on the result learned by the learning unit, a timing signal of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier.

9. The laser amplification device according to claim 5, characterized in that: Also features: a data acquisition unit that acquires a first signal indicating a time-series waveform of the intensity of the pulsed laser light incident on the laser amplifier and a second signal indicating a time-series waveform of the intensity of the pulsed laser light emitted from the laser amplifier; a learning unit that performs learning for estimating a time-series waveform of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier, based on the first signal and the second signal; as well as An estimating unit estimates, based on the result learned by the learning unit, a timing signal of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier.

10. The laser amplification device according to claim 6, characterized in that: Also features: a data acquisition unit that acquires a first signal indicating a time-series waveform of the intensity of the pulsed laser light incident on the laser amplifier and a second signal indicating a time-series waveform of the intensity of the pulsed laser light emitted from the laser amplifier; a learning unit that performs learning for estimating a time-series waveform of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier, based on the first signal and the second signal; as well as An estimating unit estimates, based on the result learned by the learning unit, a timing signal of the intensity of the pulsed laser light output when the first signal is input to the laser amplifier.

11. An extreme ultraviolet light generating device, characterized in that: have: The laser amplification device according to any one of claims 1 to 10; and An extreme ultraviolet light generator irradiates a target material with the pulse laser output from the laser amplification device to emit extreme ultraviolet light.

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