• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    An extreme ultraviolet light generation system includes: a chamber; a target generation unit; a laser system configured to output a first pre-pulse laser beam, a 5 second pre-pulse laser beam, and a main pulse laser beam so that fluence of the first pre-pulse laser beam is 1.5 J/cm2 to 16 J/cm2 inclusive at a position where a target is irradiated with the first pre-pulse laser beam; and a control unit configured to control the laser system so that a first delay time from a timing of irradiation of the target with the first pre-pulse laser beam to a timing of irradiation with the 10 second pre-pulse laser beam and a second delay time from the timing of irradiation of the target with the second pre-pulse laser beam to a timing of irradiation with the main pulse laser beam have a following relation: the first delay time < the second delay time.
    公开号:NL2025612A
    申请号:NL2025612
    申请日:2020-05-19
    公开日:2021-02-09
    发明作者:Kobayashi Takanari；Hosoda Hirokazu
    申请人:Gigaphoton Inc；
    IPC主号:
    专利说明:

    [0066] [0066]
    When only the first and second pre-pulse laser beams P1 and P2 and the main pulse laser beam M are considered or when the third pre-pulse laser beam P3 is omitted, the delay times D1 and D2 between pulses desirably have a relation as follows.
    D1<D2
    3.3 Effect
    3.3.1 lon energy Fig. 8A is a graph illustrating the ion energy of ions generated when the target 27 is irradiated with the first and second pre-pulse laser beams P1 and P2 in the first embodiment. In Fig. 8A, the horizontal axis represents the ion energy. The vertical axis represents the number of ions. E1 represents the pulse energy of the first pre-pulse laser beam P1, and E2 represents the pulse energy of the second pre-puise laser beam P2.
    In measurement of the ion energy illustrated in Fig. 8A, the first and second pre-puise laser beams P1 and P2 each had a pulse time width of 18.8 ps at the full width at half maximum and a spot diameter of 50 um at the 1/e width.
    The first delay time D1 from the timing of irradiation of the target 27 with the first pre-pulse laser beam P1 to the timing of irradiation of the target 27 with the second pre-puise laser beam P2 was 13 ns.
    As indicated by Reference sign 000 in Fig. 8A, when the pulse energy E1 of the first pre-pulse laser beam P1 was 0 md, ions having high ion energy were generated as in the comparative example. The case in which the pulse energy E1 of the first pre-pulse laser beam P1 is 0 mJ corresponds to a case in which the target 27 is not irradiated with the first pre-puise laser beam P1 but is irradiated with the second pre-pulse laser beam P2.
    As illustrated in Fig. 8A, the ion energy of generated ions tends to decrease as the pulse energy E1 of the first pre-pulse laser beam P1 is increased in the following order.
    Reference sign 010: E1 = 0.010 mJ Reference sign 017: E1 = 0.017 md Reference sign 025: E1 = 0.025 mJ
    Reference sign 050: E1 = 0.050 mJ Reference sign 078: E1 = 0.078 mJ Reference sign 144: E1 = 0.144 mJ However, as indicated by Reference sign 267, when the pulse energy E1 of the first pre-pulse laser beam P1 was 0.267 mJ, the ion energy of generated ions is higher than in the cases of Reference signs 050, 078, and 144. Fig. 8B is a graph illustrating the relation between a fluence F1 of the first pre-pulse laser beam P1 in the first embodiment at the focal point and the maximum ion energy. The graph in Fig. 8B is produced by converting the pulse energy E1 of the first pre-pulse laser beam P1 in the result illustrated in Fig. 8A into the fluence F1 and extracting the relation between the pulse energy E1 and the maximum ion energy.
    As illustrated in Fig. 8B, the maximum ion energy can be reduced by irradiating the target 27 with the first pre-pulse laser beam P1 as compared to a case in which the target 27 is not irradiated with the first pre-pulse laser beam P1. In addition, as illustrated with an approximate curve in Fig. 8B, the maximum ion energy can be reduced to 20 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be 1.5 J/cm to 16 J/cm inclusive. In addition, the maximum ion energy can be reduced to 10 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be
    1.8 J/cm to 13 J/cm inclusive. In addition, the maximum ion energy can be reduced to 5 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be 3 J/cm2 to 9 J/em inclusive. In this manner, according to the first embodiment, the ion energy generated when the target 27 is irradiated with the first and second pre-pulse laser beams P1 and P2 can be reduced. Accordingly, degradation of the multi-layer reflective film of the EUV condensation mirror 23 and decrease of the reflectance thereof can be reduced.
    A fluence F2 of the second pre-pulse laser beam P2 at the focal point is preferably 2 to 100 times larger than the fluence F1 of the first pre-pulse laser beam P1 at the focal point. In addition, the maximum ion energy is lowest for irradiation conditions denoted by Reference sign 078 and Reference sign 144, and thus the fluence F2 is preferably 5 to 10 times larger than the fluence F1.
    3.3.2 Conversion efficiency (CE) Fig. 9 is a pulse waveform diagram illustrating exemplary irradiation conditions of the first to third pre-pulse laser beams P1 to P3 and the main pulse laser beam M in the first embodiment. The pulse energy E1 of the first pre-pulse laser beam Pi was 0.14 mJ. The pulse energy E2 of the second pre-pulse laser beam P2 was 0.8 mJ. The pulse energy of the third pre-pulse laser beam P3 was 3 mJ. The delay times D1, D2, and D4 between pulses were set as follows. The first delay time D1 was 10 ns. The second delay time D2 was 1.4 pus. The fourth delay time D4 was 0.1 ps. Accordingly, the third delay time D3 was calculated to be 1.3 us by subtracting the fourth delay time D4 from the second delay time D2. Fig. 10 is a graph illustrating conversion efficiency (CE) from the energies of the first to third pre-pulse laser beams P1 to P3 and the main pulse laser beam M into the energy of EUV light in the first embodiment. Fig. 10 illustrates, as a comparative example, the CE in a case of no irradiation with the first pre-pulse laser beam P1. As illustrated in Fig. 10, according to the first embodiment, the CE comparable to that in the comparative example can be obtained.
    3.4 First pre-pulse laser including regenerative amplifier
    3.4.1 Configuration Fig. 11 is a block diagram illustrating the configuration of the first pre-pulse laser 35 in a first modification of the first embodiment. In the first modification, a regenerative amplifier 356 is used in place of the optical shutter 352 and the amplifier 353 illustrated in Fig. 7A. The regenerative amplifier 356 includes an amplification medium 70 and an optical shutter 75.
    Any other feature of the configuration of the first pre-pulse laser 35 in the first modification is same as that described with reference to Fig. 7A.
    The regenerative amplifier 356 is an exemplary optical device configured to generate first and second pre-pulse laser beams from at least one pulse of a plurality of pulses output from a mode lock laser apparatus.
    Fig. 12 illustrates the configuration of the regenerative amplifier 356 in the first modification of the first embodiment. The regenerative amplifier 356 includes an optical resonator configured by a planar mirror 68 and a concave mirror 69. The amplification medium 70, a concave mirror 71, a planar mirror 72, a polarization beam splitter 73, a pockels cell PC1, and a A/4 wave plate 74 are disposed on the optical path of the optical resonator in this order from the planar mirror 68 side. The amplification medium 70 is, for example, Nd:YAG crystal. The pockels cell PC1 corresponds to an optical element configured to control pulse confinement to the optical resonator and pulse extraction from the optical resonator. The regenerative amplifier 356 also includes an excitation light source 61 for introducing excitation light from the outside of the optical resonator into the amplification medium 70. In addition, the regenerative amplifier 356 includes a polarization beam splitter 64, a Faraday isolator 65, a planar mirror 66, and a planar mirror 67. The Faraday isolator 65 includes a Faraday rotator (not illustrated) and a A/2 wave plate (not illustrated).
    The optical shutter 75 is configured by the polarization beam splitter 73, the pockels cell PC1, the A/4 wave plate 74, the concave mirror 69, the polarization beam splitter 64, the Faraday isolator 65, the planar mirror 66, and the planar mirror 67.
    3.4.2 Operation The polarization beam splitter 64 transmits the pulse laser beam B1, which is linearly polarized light having a polarization direction parallel to the sheet, at high transmittance. In addition, the polarization beam splitter 64 reflects a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet at high reflectance as described later.
    The pulse laser beam B1 includes a first polarization component and a second polarization component orthogonal to each other. The direction of a resultant vector of the first and second polarization components is aligned with the polarization direction of the pulse laser beam B1 and is parallel to the sheet.
    The Faraday isolator 65 shifts the phase of the second polarization component of the pulse laser beam B1 incident from the lower side in Fig. 12 relative to the phase of the first polarization component thereof by 1/2 of the wavelength and transmits the pulse laser beam B1. Accordingly, the Faraday isolator 65 rotates the polarization direction of the pulse laser beam B1 as linearly polarized light by 90° and transmits the pulse laser beam B1. In addition, the Faraday isolator 65 transmits a pulse laser beam incident from the upper side in Fig. 12 without changing the phase difference between the first and second polarization components of the pulse laser beam as described later. In other words, the Faraday isolator 65 transmits a pulse laser beam incident from the upper side in Fig. 12 without rotating the polarization direction of the pulse laser beam.
    The polarization beam splitter 73 disposed in the optical resonator reflects a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet at high reflectance. In addition, the polarization beam splitter 73 transmits a pulse laser beam that is linearly polarized light having a polarization direction parallel to the sheet at high transmittance as described later.
    Voltage V3 can be applied to the pockels cell PC1 by the voltage waveform generation circuit 355. While the voltage V3 is not applied, the pockels cell PC1 transmits a pulse laser beam without changing the phase difference between the first and second polarization components of the pulse laser beam. While the voltage V3 is applied, the pockels cell PC1 shifts the phase of the second polarization component of a pulse laser beam relative to the phase of the first polarization component thereof by 1/4 of the wavelength and transmits the pulse laser beam. An electric optical element or an acoustic optical element having the same function may be used in place of the pockels cell PC1. The 2/4 wave plate 74 shifts the phase of the second polarization component of a pulse laser beam relative to the phase of the first polarization component thereof by 1/4 of the wavelength and transmits the pulse laser beam.
    3.4.2.1 Case in which voltage V3 is not applied to pockels cell PC1 A pulse laser beam incident from the Faraday isolator 65 on the optical resonator through the planar mirrors 66 and 67 and the polarization beam splitter 73 is squarely reflected by the concave mirror 69 and returned to the polarization beam splitter 73. In this case, the pulse laser beam transmits through each of the pockels cell PC1 and the A/4 wave plate 74 twice. When the voltage V3 is not applied to the pockels cell PC1, the phase of the second polarization component is shifted relative to the phase of the first polarization component by 1/2 of the wavelength in total. Thus, the polarization direction of the pulse laser beam is rotated by 90°, and the pulse laser beam is incident on the polarization beam splitter 73 as a pulse laser beam that is linearly polarized light having a polarization direction parallel to the sheet. The polarization beam splitter 73 transmits the pulse laser beam that is linearly polarized light having a polarization direction parallel to the sheet at high transmittance. A pulse laser beam B4 having transmitted through the polarization beam splitter 73 is amplified by the amplification medium 70 while being squarely reflected by the planar mirror 68 and returned to the polarization beam splitter 73 as a pulse laser beam B5. The pulse laser beam B5 transmits through the polarization beam splitter 73 at high transmittance. The pulse laser beam having transmitted through the polarization beam splitter 73 is squarely reflected by the concave mirror 69 and returned to the polarization beam splitter 73. In this case, when the voltage V3 is not applied to the pockels cell PC1, the polarization direction of the pulse laser beam is rotated by 90°, and the pulse laser beam is incident on the polarization beam splitter 73 as a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet. The polarization beam splitter 73 reflects the pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet at high reflectance. As described above, when the voltage V3 is not applied to the pockels cell PCH, the pulse laser beam is output from the optical resonator after only one round trip inside the optical resonator. The pulse laser beam output from the optical resonator is incident on the Faraday isolator 65 from the upper side in Fig. 12. The Faraday isolator 65 transmits the linearly polarized pulse laser beam incident from the upper side in Fig. 12 without rotating the polarization direction thereof. The polarization beam splitter 64 reflects the pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet at high reflectance. The pulse laser beam B3 reflected by the polarization beam splitter 64 is guided to the plasma generation region 25 through the laser beam condensation optical system 22a illustrated in Fig. 6. However, the pulse laser beam B3, which is output after only one round trip inside the optical resonator of the regenerative amplifier 356, has such a weak intensity that the pulse laser beam B3 does not diffuse the target 27 nor generate plasma from the target 27 when incident on the target 27.
    3.4.2.2 Case in which voltage V3 is applied to pockels cell PC1 The voltage waveform generation circuit 355 may change the voltage V3 applied to the pockels cell PC1 from "OFF" to "ON" after the pulse laser beam B4 is emitted from the polarization beam splitter 73 and before the pulse laser beam B4 is returned to the polarization beam splitter 73 as the pulse laser beam B5. While the voltage V3 is applied, the pockels cell PC1 shifts the phase of the second polarization component of a pulse laser beam relative to the phase of the first polarization component thereof by 1/4 of the wavelength and transmits the pulse laser beam. A pulse laser beam having transmitted through the polarization beam splitter 73 from the left side in Fig. 12 is squarely reflected by the concave mirror 69 and returned to the polarization beam splitter 73. In this case, the polarization direction of the pulse laser beam is rotated by 90° as the pulse laser beam transmits through the A/4 wave plate 74 twice, and the polarization direction is further rotated by 90° as the pulse laser beam transmits through the pockels cell PC1 to which the voltage V3 is applied twice. Accordingly, a pulse laser beam that is linearly polarized light having a polarization direction parallel to the sheet is incident on the polarization beam splitter 73. The pulse laser beam that is linearly polarized light having a polarization direction parallel to the sheet transmits through the polarization beam splitter 73 again and is amplified by the amplification medium 70. While the voltage V3 is applied to the pockels cell PC1, pulse confinement to the optical resonator is maintained and amplification operation is repeated.
    After the amplification operation is repeated, the voltage waveform generation circuit 355 may change the voltage V3 applied to the pockels cell PCH from "ON" to "OFF" before the pulse laser beam B4 emitted from the polarization beam splitter 73 is returned to the polarization beam splitter 73 as the pulse laser beam BS. A pulse laser beam having transmitted through the polarization beam splitter 73 from the left side in Fig. 12 is squarely reflected by the concave mirror 69 and returned to the polarization beam splitter 73. When the voltage V3 is not applied to the pockels cell PC1, the polarization direction of the pulse laser beam is rotated by 90°, and the pulse laser beam is incident on the polarization beam splitter 73 as a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet. The polarization beam splitter 73 reflects the pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet at high reflectance. In this manner, pulses are extracted from the optical resonator. While the voltage V3 is applied to the pockels cell PC1 and the amplification operation is repeated, the pulse laser beam B1 newly output from the mode lock laser apparatus 351 is incident on the optical resonator as a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet, and is incident on the pockels cell PC1. The polarization direction of the pulse laser beam is rotated by 90° as the pulse laser beam transmits through the 2/4 wave plate 74 twice, and the polarization direction is further rotated by 90° as the pulse laser beam transmits through the pockels cell PC1 to which the voltage V3 is applied twice. Then, the pulse laser beam is incident on the polarization beam splitter 73 as a pulse laser beam that is linearly polarized light having a polarization direction orthogonal to the sheet. Thus, the pulse laser beam is reflected by the polarization beam splitter 73 and output out of the optical resonator without being amplified.
    3.4.2.3 Generation of first and second pre-pulse laser beams Figs. 13A and 13B simply illustrate the function of the optical shutter 75 in the first modification of the first embodiment. While the voltage V3 is not applied to the pockels cell PC1 (PC1:OFF), the pulse laser beam B1 is output from the regenerative amplifier 356 as the pulse laser beam B3 after only one round trip as the pulse laser beams B4 and B5 in the optical resonator including the amplification medium 70.
    When the voltage V3 applied to the pockels cell PC1 is switched from "OFF" to "ON" after the pulse laser beam B4 is emitted from the optical shutter 75 and before the pulse laser beam B4 is returned as the pulse laser beam B5 (PC1:0N}), pulses are confined to the optical resonator and repeatedly amplified by the amplification medium 70. In this case, the pulse laser beam B1 that is newly incident is output from the regenerative amplifier 356 as the pulse laser beam B3 without being amplified by the amplification medium 70. When the voltage V3 applied to the pockels cell PC1 is switched from "ON" to "OFF" (PC1:OFF), the pulses confined to the optical resonator are extracted through the optical shutter 75 and output from the regenerative amplifier 356 as the pulse laser beam B3. The state in which the voltage V3 is applied to the pockels cell PC1 (PC1:ON) corresponds to a first state in which pulse confinement to the optical resonator is performed. The state in which the voltage V3 is not applied to the pockels cell PC1 (PC1:OFF) corresponds to a second state in which pulse extraction from the optical resonator is performed.
    Fig. 13C is a time chart illustrating the process of generating the first and second pre-pulse laser beams P1 and P2 in the first modification of the first embodiment. In Fig. 13C, the horizontal axis represents time T. The vertical axis represents signal strength or pulse laser beam energy.
    The pulse laser beam Bt is periodically output from the mode lock laser apparatus 351.
    While the voltage V3 is not applied to the pockels cell PC1 (PC1:OFF), Pulse #1 included in the pulse laser beam B1 is emitted from the optical shutter 75 as Pulse #10 of the pulse laser beam B4. This pulse is amplified by the amplification medium 70, returned to the optical shutter 75 as Pulse #11 of the pulse laser beam B5, and output from the regenerative amplifier 356 as Pulse #12 of the pulse laser beam B3. Pulse #2 passes through a path same as that of Pulse #1 and is output as Pulse #22 of the pulse laser beam BS.
    Pulse #3 included in the pulse laser beam B1 is emitted from the optical shutter 75 as Pulse #30 of the pulse laser beam B4. To confine this pulse to the optical resonator, rise of the voltage V3 is completed (PC1:0ON) before Pulse #30 is returned to the optical shutter 75 as Pulse #31 of the pulse laser beam B5.
    Accordingly, this pulse is emitted again from the optical shutter 75 as Pulse #32 of the pulse laser beam B4. Thereafter, the pulse is amplified through round trips inside the optical resonator as Pulses #33, #34, #35, #36, and #37.
    While the voltage V3 is applied to the pockels cell PC1 (PC1:0N), Pulses #4, #5, and #6 of the pulse laser beam B1 incident on the optical shutter 75 are output from the regenerative amplifier 356 as Pulses #40, #50, and #60 of the pulse laser beam B3 without being amplified.
    In the first modification of the first embodiment, the voltage V3 applied to the pockels cell PC1 is switched from "ON" to "OFF" in synchronization as Pulse #37 of the pulse laser beam B5 returned from the amplification medium 70 to the optical shutter 75 passes through the pockels cell PC1. More specifically, the timing of fall of the voltage V3 is adjusted so that Pulse #37 passes through the pockels cell PC1 halfway through fall of the voltage V3. The timing of fall of the voltage V3 may be controlled, for example, based on a result of detection by a light detector (not ilustrated).
    Accordingly, part of Pulse #37 is output from the regenerative amplifier 356 as the pulse laser beam B3. This pulse laser beam B3 corresponds to the first pre- pulse laser beam P1. However, the other part of Pulse #37 is not output as the pulse laser beam B3 but remains inside the optical resonator as Pulse #38 of the pulse laser beam B4. Pulse #38 is further amplified by the amplification medium 70 and returned to the optical shutter 75 as Pulse #39 of the pulse laser beam B5. In this case, when the voltage V3 is not applied to the pockels cell PC1 (PC1:OFF), Pulse #39 is output from the regenerative amplifier 356 as the pulse laser beam BS. This pulse laser beam B3 corresponds to the second pre-pulse laser beam P2.
    3.4.3 Effect According to the first modification, a pulse energy ratio of the first and second pre-pulse laser beams P1 and P2 can be changed by finely adjusting a timing at which Pulse #37 passes through the pockels cell PC1 halfway through fall of the voltage V3.
    The output timing difference between the first and second pre-pulse laser beams P1 and P2 depends on the resonator length of the optical resonator included in the regenerative amplifier 356. For example, the output timing difference is 10 ns assuming that the resonator length of the optical resonator is 1.5 m, the speed of light in vacuum is 3x108 m/s, and the refractive index in the optical path is one. The output timing difference substantially corresponds to the first delay time D1.
    3.5 Regenerative amplifier including two pockels cells
    3.5.1 Configuration Fig. 14 illustrates the configuration of the regenerative amplifier 356 in a second modification of the first embodiment. In the second modification, the regenerative amplifier 356 includes another pockels cell PC2 between the concave mirror 69 and the polarization beam splitter 73. The pockels cells PC1 and PC2 correspond to first and second optical elements configured to control pulse confinement to the optical resonator and pulse extraction from the optical resonator.
    Voltage V4 can be applied to the pockels cell PC2 by the voltage waveform generation circuit 355. While the voltage V4 is not applied, the pockels cell PC2 transmits a pulse laser beam without changing the phase difference between the first and second polarization components of the pulse laser beam. Thus, operation of the regenerative amplifier 356 in the second modification is same as that in the first modification when the voltage V4 is not applied to the pockels cell PC2.
    While the voltage V4 is applied, the pockels cell PC2 shifts the phase of the second polarization component of a pulse laser beam relative to the phase of the first polarization component thereof and transmits the pulse laser beam. The amount of phase shift provided to these polarization components can be changed by changing the value of the voltage V4.
    Any other feature of the configuration of the second modification is same as that of the first modification described with reference to Fig. 12.
    3.5.2 Operation Figs. 15A and 15B simply illustrate the function of the optical shutter 75 in the second modification of the first embodiment. While the voltage V4 is not applied to the pockels cell PC2 (PC2:0FF), the function of the optical shutter 75 is same as the function of the optical shutter 75 in the first modification described with reference to Figs. 13A and 13B.
    When the voltage V4 equal to the voltage V3 is applied to the pockels cell PC2 (PC2:0ON), the pockels cell PC2 shifts the phase of the second polarization component of a pulse laser beam relative to the phase of the first polarization component thereof by 1/4 of the wavelength and transmits the pulse laser beam. Thus, the operation of the optical shutter 75 when the voltages of both pockels cells PC1 and PC2 are set to "ON" (PC1:ON and PC2:ON) is same as the operation of the optical shutter 75 when the voltages of both pockels cells PC1 and PC2 are set to "OFF" (PC1:OFF and PC2:OFF).
    Fig. 15C is a time chart illustrating the process of generating the first and second pre-pulse laser beams P1 and P2 in the second modification of the first embodiment. In Fig. 15C, the horizontal axis represents time T. The vertical axis represents signal strength or pulse laser beam energy.
    When the voltage V4 is not applied to the pockels cell PC2 (PC2:0FF), the operation of the optical shutter 75 in the second modification is same as that in the first modification. The voltage V3 is applied to the pockels cell PC1 (PC1:0N) to confine Pulse #3 included in the pulse laser beam B1 to the optical resonator.
    In the second modification, the voltage V4 is risen to a predetermined value after Pulse #36 of the pulse laser beam B4 is emitted from the optical shutter 75 and before the pulse is returned to the optical shutter 75 as Pulse #37 of the pulse laser beam B5. The predetermined value of the voltage V4 is higher than zero and lower than the voltage V3.
    Accordingly, part of Pulse #37 is output from the regenerative amplifier 356 as the pulse laser beam B3. This pulse laser beam B3 corresponds to the first pre- pulse laser beam P1. However, the other part of Pulse #37 is not output as the pulse laser beam B3 but remains inside the optical resonator as Pulse #38 of the pulse laser beam B4. Pulse #38 is further amplified by the amplification medium 70 and returned to the optical shutter 75 as Pulse #39 of the pulse laser beam B5.
    Application of both voltages V3 and V4 is canceled (PC1:OFF and PC2:0FF) after Pulse #38 of the pulse laser beam B4 is emitted from the optical shutter 75 and before the pulse is returned to the optical shutter 75 as Pulse #39 of the pulse laser beam B5. Accordingly, Pulse #39 is extracted from the optical resonator as the pulse laser beam B3 and output from the regenerative amplifier
    356. This pulse laser beam B3 corresponds to the second pre-pulse laser beam P2.
    Alternatively, application of the voltage V4 may be canceled but application of the voltage V3 may be kept (PC1:ON and PC2:OFF) after Pulse #38 of the pulse laser beam B4 is emitted from the optical shutter 75 and before the pulse is returned to the optical shutter 75 as Pulse #39 of the pulse laser beam B5. In this case, Pulse #39 remains inside the optical resonator and is further amplified. Thereafter, this pulse can be output from the regenerative amplifier 356 as the pulse laser beam B3 by canceling application of the voltage V3 (PC1:OFF and PC2:OFF). This pulse laser beam B3 corresponds to the second pre-pulse laser beam P2.
    3.5.3 Effect According to the second modification, the pulse energy ratio of the first and second pre-pulse laser beams P1 and P2 can be changed by adjusting the value of the voltage V4. The control of the value of the voltage V4 in the second modification is likely to be stabilized as compared to the control of the timing of fall of the voltage V3 in the first modification, and thus the pulse energy ratio can be stabilized.
    3.6 First pre-pulse laser including delay optical path
    3.6.1 Configuration Fig. 16A is a block diagram illustrating the configuration of the first pre-pulse laser 35 in a third modification of the first embodiment. The first pre-pulse laser 35 in the third modification includes a master oscillator MO, a retarder 357, two polarizers 358 and 359, and the amplifier 353.
    The master oscillator MO is a laser apparatus configured to output the pulse laser beam B1 having a pulse time width in the order of picoseconds. The retarder 357 includes, for example, a A/2 wave plate. When the direction of the optical axis of crystal included in the retarder 357 is tilted by 6 relative to the polarization direction of the pulse laser beam B1 output from the master oscillator MO, the retarder 357 rotates the polarization direction of the pulse laser beam B1 by 26 and emits the pulse laser beam B1. The pulse laser beam emitted from the retarder 357 includes a first polarization component and a second polarization component orthogonal to each other. The ratio of the first and second polarization components differs in accordance with the polarization direction of the pulse laser beam emitted from the retarder 357. The polarizers 358 and 359 each include for example, a polarization beam splitter. The polarizers 358 and 359 each reflect the first polarization component at high reflectance and transmit the second polarization component at high transmittance. Accordingly, the polarizer 358 bifurcates the pulse laser beam emitted from the retarder 357 into a pulse laser beam B7 including the first polarization component and a pulse laser beam B8 including the second polarization component. The polarizer 359 merges the pulse laser beam B7 and the pulse laser beam B8 and emits the merged pulse laser beams as a pulse laser beam B9. The optical path of the pulse laser beam B7 between the polarizer 358 and the polarizer 359 includes a delay optical path DP1. The optical path of the pulse laser beam B8 between the polarizer 358 and the polarizer 359 includes a delay optical path DP2 longer than the delay optical path DP1. The polarizer 358 corresponds to a first polarizer of the present disclosure, and the polarizer 359 corresponds to a second polarizer of the present disclosure. The delay optical path DP1 corresponds to a first delay optical path of the present disclosure, and the delay optical path DP2 corresponds to a second delay optical path of the present disclosure.
    The present invention is not limited thereto, but an alternative configuration in which the delay optical path DP1 is longer than the delay optical path DP2 may be employed. In this alternative configuration, the delay optical path DP1 corresponds to the second delay optical path of the present disclosure, and the delay optical path DP2 corresponds to the first delay optical path of the present disclosure. The amplifier 353 includes a multipath slab amplifier or a fiber amplifier. The amplifier 353 amplifies the pulse laser beam B9 and outputs the amplified pulse laser beam B9 as the pulse laser beam B3. The pulse laser beam B3 includes the first and second pre-pulse laser beams P1 and P2.
    3.6.2 Operation and effect Fig. 16B is a time chart illustrating the process of generating the first and second pre-pulse laser beams P1 and P2 in the third modification of the first embodiment. In Fig. 16B, the horizontal axis represents time T. The vertical axis represents pulse laser beam energy. The pulse laser beam B1 is bifurcated into the pulse laser beams B7 and B8 through the retarder 357 and the polarizer 358. The ratio of the first and second polarization components can be adjusted by adjusting the direction of the optical axis of crystal included in the retarder 357. The pulse energy ratio of the pulse laser beams B7 and B8 can be adjusted by adjusting the ratio of the first and second polarization components. Thus, the pulse energy ratio of the first and second pre-pulse laser beams P1 and P2 can be adjusted by the tilt angle 6 of the optical axis of crystal of the retarder 357 relative to the polarization direction of the puise laser beam B1. The polarizer 359 merges the pulse laser beams B7 and B8 and emits the merged pulse laser beams as the pulse laser beam B9. The time difference between the first and second polarization components included in the pulse laser beam B9 can be adjusted by the optical path length difference between the delay optical paths DP1 and DP2. The time difference between the first and second polarization components substantially corresponds to the first delay time D1. The first pre-pulse laser beam P1 is generated through amplification of the pulse laser beam B7 having passed through the delay optical path DP1, and the second pre- pulse laser beam P2 is generated through amplification of the pulse laser beam B8 having passed through the delay optical path DP2. With the above-described alternative configuration, the first pre-pulse laser beam P1 is generated through amplification of the pulse laser beam B8 having passed through the delay optical path DP2, and the second pre-pulse laser beam P2 is generated through amplification of the pulse laser beam B7 having passed through the delay optical path DP1. According to the third modification, the first and second pre-pulse laser beams P1 and P2 can be generated without controlling the pockels cells and the like. In the third modification, the first and second pre-pulse laser beams P1 and P2 have polarization directions different from each other, but the present disclosure is not limited thereto. For example, an optical element for aligning the polarization directions of the first and second pre-pulse laser beams P1 and P2 or setting each polarization direction to be an optional polarization direction may be disposed between the polarizer 359 and the amplifier 353.
    3.7 First pre-pulse laser beam of the order of nanoseconds
    3.7.1 Configuration Fig. 17 is a partially cross-sectional view illustrating the configuration of the EUV light generation system 11 according to a fourth modification of the first embodiment. In the fourth modification, the first pre-pulse laser 35 outputs the first pre-pulse laser beam P1 having a pulse time width in the order of nanoseconds. In the present disclosure, the order of nanoseconds is equal to or longer than 1 ns and shorter than the third delay time D3. Alternatively, the order of nanoseconds may be equal to or longer than 1 ns and shorter than the second delay time D2. Alternatively, the order of nanoseconds may be equal to or longer than 1 ns and shorter than 1000 ns.
    The second pre-pulse laser 36 outputs the second pre-pulse laser beam P2 having a pulse time width in the order of picoseconds.
    The main pulse laser 37 outputs both the third pre-pulse laser beam P3 and the main pulse laser beam M. The configuration in which the main pulse laser 37 outputs both the third pre-pulse laser beam P3 and the main pulse laser beam M will be described later with reference to Fig. 19. Alternatively, a third pre-pulse laser (not illustrated) and the main pulse laser 37 may be separately used to output the third pre-pulse laser beam P3 and the main pulse laser beam M.
    Any other feature of the configuration of the fourth modification is same as that described with reference to Fig. 6.
    3.7.2 lon energy Fig. 18A is a graph illustrating the ion energy of ions generated when the target 27 is irradiated with the first and second pre-pulse laser beams P1 and P2 in the fourth modification of the first embodiment. In Fig. 18A, the horizontal axis represents the ion energy. The vertical axis represents the number of ions. E1 represents the pulse energy of the first pre-pulse laser beam P1, and E2 represents the pulse energy of the second pre-pulse laser beam P2.
    In measurement of the ion energy illustrated in Fig. 18A, the first pre-puise laser beam P1 had a pulse time width of 6 ns at the full width at half maximum, and a spot diameter of 400 um at the 1/e2 width.
    The second pre-pulse laser beam P2 had a pulse time width of 18.8 ps at the full width at half maximum, and a spot diameter of 50 um at the 1/e width.
    The first delay time D1 from the timing of irradiation of the target 27 with the first pre-pulse laser beam P1 to the timing of irradiation of the target 27 with the second pre-pulse laser beam P2 was 10 ns.
    As indicated by Reference sign 000 in Fig. 18A, when the pulse energy E1 of the first pre-pulse laser beam P1 was 0 md, ions having high ion energy were generated.
    As illustrated in Fig. 18A, the ion energy of generated ions tends to decrease as the pulse energy E1 of the first pre-pulse laser beam P1 is increased in the following order.
    Reference sign 015: Et = 1.5 mJ Reference sign 017: E1 = 1.72 mJ Reference sign 020: E1 = 2.01 mJ Reference sign 030: Et = 3 md Reference sign 060: E1 = 6 mJ Reference sign 120: E1 = 12 mJ Fig. 18B is a graph illustrating the relation between the fluence F1 of the first pre-pulse laser beam P1 at the focal point in the fourth modification of the first embodiment and the maximum ion energy. The graph in Fig. 18B is produced by converting the pulse energy E1 of the first pre-pulse laser beam P1 in the result illustrated in Fig. 18A into the fluence F1 and extracting the relation between the pulse energy E1 and the maximum ion energy.
    As illustrated in Fig. 18B, the maximum ion energy can be reduced by irradiating the target 27 with the first pre-pulse laser beam P1 as compared to a case in which the target 27 is not irradiated with the first pre-pulse laser beam P1.
    In addition, as illustrated with an approximate curve in Fig. 18B, the maximum ion energy can be reduced to 10 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be 1.5 J/cm to 16 J/cm inclusive.
    In addition, the maximum ion energy can be reduced to 5 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be
    1.8 J/cm to 13 J/cm inclusive.
    In addition, the maximum ion energy can be reduced to 2.5 keV or less by setting the fluence F1 of the first pre-pulse laser beam P1 at the focal point to be 3 Jiem to 11 J/em:.
    The fluence F2 of the second pre-pulse laser beam P2 at the focal point is preferably 2 to 100 times larger than the fluence F1 of the first pre-pulse laser beam P1 at the focal point. In addition, the maximum ion energy is lowest for irradiation conditions denoted by Reference signs 060 and 120, and thus the fluence F2 is preferably 4 to 8 times larger than the fluence F1.
    4. Main pulse laser configured to generate two pulses
    4.1 Configuration Fig. 19 is a partially cross-sectional view illustrating the configuration of the EUV light generation system 11 according to a second embodiment of the present disclosure. In the second embodiment, the main pulse laser 37 outputs the third pre-pulse laser beam P3 and the main pulse laser beam M.
    Any other feature of the second embodiment is same as that of the first embodiment.
    Fig. 20A is a block diagram illustrating the configuration of the main pulse laser 37 in the second embodiment. The main pulse laser 37 includes two master oscillators MO1 and MO2, a beam combiner 373, and a plurality of amplifiers PA1, PA2, and PA3. The master oscillators MO1 and MO2 each include, for example, a CO: laser oscillator including a Q switch (not illustrated), or a quantum cascade laser. The amplifiers PA1, PA2, and PAS each include, for example, a CO: laser amplifier.
    A main pulse laser control unit 374 connects the delay circuit 51 and the main pulse laser 37 through a signal line. The main pulse laser control unit 374 may be included in the EUV light generation control unit 5 or may be integrated with the EUV light generation control unit 5.
    4.2 Operation Fig. 20B illustrates the pulse waveform of a pulse laser beam output from the master oscillator MO1 in the second embodiment. The main pulse laser control unit 374 outputs an oscillation trigger signal to the master oscillator MO1 in accordance with a trigger signal transmitted from the delay circuit 51. The master oscillator MO1 outputs the pulse laser beam in accordance with the oscillation trigger signal.
    Fig. 20C illustrates the pulse waveform of a pulse laser beam output from the master oscillator MO2 in the second embodiment. The main pulse laser control unit 374 outputs an oscillation trigger signal to the master oscillator MO2 in accordance with a trigger signal transmitted from the delay circuit 51. The master oscillator MO2 outputs the pulse laser beam in accordance with the oscillation trigger signal.
    Fig. 20D illustrates the pulse waveform of a pulse laser beam emitted from the beam combiner 373 in the second embodiment. The beam combiner 373 connects the optical paths of the pulse laser beams output from the master oscillators MO1 and MO2, respectively, and emits the pulse laser beams toward the amplifier PAT.
    The pulse laser beam output from the master oscillator MO2 has a predetermined time difference relative to the pulse laser beam output from the master oscillator MO1. The pulse laser beam output from the master oscillator MO2 has an energy larger than that of the pulse laser beam output from the master oscillator MO1.
    Fig. 20E illustrates the pulse waveform of a pulse laser beam emitted from the amplifier PA3 in the second embodiment. The amplifiers PA1 to PA3 amplify the pulse laser beams emitted from the beam combiner 373 and output the amplified pulse laser beams as the third pre-pulse laser beam P3 and the main pulse laser beam M. The time difference between the pulse laser beams output from the master oscillators MO1 and MO2 substantially corresponds to the fourth delay time D4 from the timing of irradiation of the target 27 with the third pre-pulse laser beam P3 to the timing of irradiation of the target 27 with the main pulse laser beam M.
    4.3 Effect According to the second embodiment, since both the third pre-pulse laser beam P3 and the main pulse laser beam M are output from the one main pulse laser 37, the configuration of the laser system 3 can be simplified.
    In the second embodiment, the beam combiner 373 is disposed between the master oscillator MO2 and the amplifier PA1, but the present disclosure is not limited thereto. When the third pre-pulse laser beam P3 does not need to be largely amplified, the beam combiner 373 may be disposed between the amplifier PA1 and the amplifier PA2 or between the amplifier PA2 and the amplifier PA3.
    In the second embodiment, the third pre-pulse laser beam P3 and the main pulse laser beam M are output from the main pulse laser 37 as separate pulses,
    but the present disclosure is not limited thereto. The time difference between the pulse laser beams output from the master oscillators MO1 and MO2 may be set to be short so that two pulses are close to each other to generate a main pulse laser beam including a pedestal part.
    4.4 Main pulse laser configured to generate main pulse including pedestal part
    4.4.1 Configuration Fig. 21 is a partially cross-sectional view illustrating the configuration of the EUV light generation system 11 according to a modification of the second embodiment. In the modification of the second embodiment, the main pulse laser 37 outputs a main pulse laser beam MP including a pedestal part.
    Any other feature is same as that described with reference to Fig. 19.
    Fig. 22A is a block diagram illustrating the configuration of the main pulse laser 37 in the modification of the second embodiment. The main pulse laser 37 includes the master oscillator MO, an optical shutter 372, the amplifiers PA1, PA2, and PAS, and a voltage waveform generation circuit 375.
    4.4.2 Operation Fig. 22B illustrates the pulse waveform of the pulse laser beam B1 output from the master oscillator MO in the modification of the second embodiment. The main pulse laser control unit 374 outputs an oscillation trigger signal to the master oscillator MO in accordance with a trigger signal transmitted from the delay circuit
    51. The master oscillator MO outputs the pulse laser beam B1 in accordance with the oscillation trigger signal.
    Fig. 22C illustrates the pulse waveform of optical shutter control voltage V5 output from the voltage waveform generation circuit 375 in the modification of the second embodiment. The optical shutter control voltage V5 is a stepped pulse including a first half part having a low voltage value, and a second half part having a high voltage value.
    Fig. 22D illustrates the pulse waveform of the pulse laser beam B2 having passed through the optical shutter 372 in the modification of the second embodiment. The transmittance of the optical shutter 372 is low when the voltage value of the optical shutter control voltage V5 is low, but the transmittance is high when the voltage value of the optical shutter control voltage V5 is high. Thus, the pulse waveform of the pulse laser beam B2 includes a first half part in which the light intensity is low and gradually increases, and a second half part in which the light intensity abruptly increases to a high value and then decreases. Fig. 22E illustrates the pulse waveform of the main pulse laser beam MP having passed through the amplifier PA3 in the modification of the second embodiment. The amplifiers PA1 to PA3 amplify the pulse laser beam B2 and output the main pulse laser beam MP. The pulse waveform of the main pulse laser beam MP includes a pedestal part in which the light intensity is low and gradually increases, and a peak part in which the light intensity abruptly increases to a high value and then decreases.
    Fig. 23 is a pulse waveform diagram of the first and second pre-pulse laser beams P1 and P2 and the main pulse laser beam MP including the pedestal part in the modification of the second embodiment. The delay times D1 and D2 between pulses has a relation as follows. D1 < D2 The delay time D2 when the target 27 is irradiated with the main pulse laser beam MP including the pedestal part in place of the main pulse laser beam M is defined as follows. The second delay time D2 is a delay time from the timing of irradiation of the target 27 with the second pre-pulse laser beam P2 to the timing of irradiation of the target 27 with the main pulse laser beam MP.
    4.4.3 Effect According to the modification of the second embodiment, plasma can be efficiently generated from the target 27 by generating the main pulse laser beam MP including the pedestal part. The first half part and the second half part included in the optical shutter control voltage V5 do not necessarily need to be temporally continuous with each other but may be temporally separated from each other and generated as separate square wave pulses. When the first half part and the second half part of the optical shutter control voltage V5 are temporally separated from each other, the pulse laser beam B2 is two pulses temporally separated from each other. Accordingly, the third pre-pulse laser beam P3 and the main pulse laser beam M can be output from the amplifier PAS.
    5. Other Fig. 24 schematically illustrates the configuration of the exposure apparatus 6 connected with the EUV light generation apparatus 1.
    In Fig. 24, the exposure apparatus 6 includes a mask irradiation unit 600 and a workpiece irradiation unit 601. The mask irradiation unit 600 illuminates, with EUV light incident from the EUV light generation apparatus 1, a mask pattern on a mask table MT through a reflection optical system. The workpiece irradiation unit 601 images the EUV light reflected by the mask table MT onto a workpiece (not illustrated) disposed on a workpiece table WT through the reflection optical system. The workpiece is a photosensitive substrate such as a semiconductor wafer to which photoresist is applied. The exposure apparatus 6 translates the mask table MT and the workpiece table WT in synchronization to expose the workpiece to the EUV light reflected at the mask pattern. Through the exposure process as described above, a device pattern is transferred onto the semiconductor wafer, thereby manufacturing an electronic device.
    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 for those skilled in the art that 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. 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 "atleast 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 the any thereof and any other than A, B, and C.
    权利要求:
    Claims (19)
    [1]
    An extreme ultraviolet light generation system comprising: a chamber; a target generation unit configured to deliver a target to a predetermined region in the chamber; a laser system configured to provide a first pre-pulse laser beam, a second pre-pulse laser beam, and a main pulse laser beam to irradiate the target with the first pre-pulse laser beam, the second pre-pulse laser beam, and the main pulse laser beam in this sequence, so that the smoothness of the first pre-pulse laser beam is 1.5 J / cm2 to 16 J / cm2, at a position where the target is irradiated with the first pre-pulse laser beam; and a control unit adapted to control the laser system so that a first delay time from a moment of irradiation of the target with the first pre-pulse laser beam, to a moment of irradiation of the target with the second pre-pulse laser beam, and a second delay time from a moment of irradiation of the target with the second pre-pulse laser beam, to a moment of irradiation of the target with the main pulse laser beam, meet the following relationship: the first delay time <the second delay time.
    [2]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system is arranged so that the smoothness of the second pre-pulse laser beam at a position where the target is irradiated with the second pre-pulse laser beam is 5 to 10 times greater than the integrity of the first pre-pulse laser beam at a position where the target is irradiated with the first pre-pulse laser beam.
    [3]
    The extreme ultraviolet light generation system of claim 1, wherein the controller controls the laser system so that a first delay time is 5 ns to 100 ns.
    [4]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system comprises a mode lock laser device configured to provide a pulsed laser beam comprising a plurality of pulses, and an optical device configured to capture the first pre-pulse laser beam and the second pre-pulse laser beam from at least one of the pulses.
    [5]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system comprises: a mode-locked laser device, and an optical shutter disposed in an optical path of a pulsed laser beam supplied from the mode-locked laser device, and the control unit a first pulse sets as a first pre-pulse laser beam, which pulse is sent by the optical shutter by setting, as a first transmission, a transmission of the optical shutter when a first pulse of a plurality of pulses that make up the pulsed laser beam enters the optical shutter, and sets a second pulse as a second pre-pulse laser beam, which pulse is sent by the optical shutter by setting, as a second transmission higher than the first transmission, a transmission of the optical shutter when the second pulse which follows after the first pulse as part of the pulses, reaches the optical shutter.
    [6]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system comprises: a mode-locked laser device, and a regenerable amplifier arranged in an optical path of a laser beam supplied by the mode-locked laser device, the regenerable amplifier having an optical resonator. comprises, a gain medium disposed in an optical path of the optical resonator, and an optical element adapted to control pulse confinement in the optical resonator and pulse extraction from the optical resonator, and after trapping a pulse of a plurality of pulses emitting the pulsed laser beam contained in the optical resonator, the control unit, in synchronism with a moment when a pulse passes through the optical element, changes the optical element from a first state in which pulse confinement is performed in the optical resonator to a second state in which pulse extraction from the optical resonator is performed. performed, so Some of the one pulse is extracted from the optical resonator, and is provided as the first pre-pulse laser beam, and another portion of the one pulse is further amplified within the optical resonator, and is provided as the second pre-pulse laser beam.
    [7]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system comprises: a mode-locked laser device, and a regenerable amplifier arranged in an optical path of a laser beam supplied by the mode-locked laser device, the regenerable amplifier having an optical resonator. comprises, a gain medium arranged in an optical path of the optical resonator, and first and second optical elements arranged to control pulse confinement in the optical resonator and pulse extraction from the optical resonator, and after trapping a pulse of a plurality of pulses that pulsed laser beam included in the optical resonator by setting a voltage, as a first voltage, applied to the first optical element, the control unit sets a voltage as the second voltage, which is lower than the first voltage, which is applied to the second optical element, so that it becomes part of one pulse extracted from the optical resonator as the first pre-pulse laser beam, then further amplifying another part of one pulse within the optical resonator and applying the second voltage to the second optical element so that the other part is extracted from the optical resonator to provide laser beam as the second pre-pulse.
    [8]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system comprises: a main oscillator, a first polarizer arranged in an optical path of a pulsed laser beam supplied from the main oscillator and arranged to split the pulsed laser beam into a first laser beam comprising a first polarization component, a second laser beam comprising a second polarization component, a second polarizer configured to unite the first laser beam and second laser beam, and provide the combined laser beams as the first pre-pulse laser beam and the second pre-pulse laser beam ,
    a first retarding optical path included in an optical path of the first laser beam between the first polarizer and the second polarizer, a second retarding optical path included in an optical path of the second laser beam between the first polarizer and the second polarizer, the second retarding optical path is longer than the first delay optical path.
    [9]
    The extreme ultraviolet light generation system of claim 1, wherein the laser system further provides a third pre-pulse laser beam to irradiate the target with the third pre-pulse laser beam after the target is irradiated with the second pre-pulse laser beam, and before the target is irradiated with the main pulse laser beam.
    [10]
    The extreme ultraviolet light generation system of claim 9, wherein the controller controls the laser system such that the first delay time, a third delay time from a time of irradiation of the target with the second pre-pulse laser beam, to a time of irradiation of the target with the third pre-pulse laser beam, a fourth delay time from a moment of irradiation of the target with the third pre-pulse laser beam, to a moment of irradiation of the target with the main pulse laser beam, in the following relationship to each other: the first delay time <the fourth delay time <the third delay time.
    [11]
    The extreme ultraviolet light generation system of claim 9, wherein the laser system comprises a CO2 laser device configured to provide the third prepulse laser beam and the main pulse laser beam.
    [12]
    An extreme ultraviolet light generation system comprising: a chamber; a target generation unit configured to deliver a target to a predetermined region in the chamber; a laser system configured to provide a first pre-pulse laser beam having a pulse time width on the order of nanoseconds, a second pre-pulse laser beam having a pulse time width on the order of picoseconds, a third pre-pulse laser beam, and a main pulse laser beam so as to irradiating the target with the first pre-pulse laser beam, the second pre-pulse laser beam, the third pre-pulse laser beam and the main pulse laser beam in this order, and a control unit adapted to control the laser system so that a first delay time of a moment from irradiation of the target with the first pre-pulse laser beam, to a moment of irradiation of the target with the second pre-pulse laser beam, and a second delay time from a moment of irradiation of the target with the second pre-pulse laser beam, to a moment of irradiating the target with the main pulse laser beam to satisfy the following relationship: the first delay time <the second delay time.
    [13]
    The extreme ultraviolet light generation system of claim 12, wherein the laser system is arranged such that the smoothness of the first pre-pulse laser beam has a value of 1.5 J / cm2 to 16 J / cm2, at a position where the target is irradiated with the first pre-pulse laser beam.
    [14]
    The extreme ultraviolet light generation system of claim 12, wherein the laser system is arranged so that the smoothness of the second pre-pulse laser beam at a position where the target is irradiated with the second pre-pulse laser beam is 4 to 8 times greater than the smoothness of the first pre-pulse laser beam at a position where the target is irradiated with the first pre-pulse laser beam.
    [15]
    The extreme ultraviolet light generation system of claim 12, wherein the controller controls the laser system so that a first delay time is 5 ns to 100 ns.
    [16]
    The extreme ultraviolet light generation system of claim 12, wherein the controller controls the laser system such that the first delay time, a third delay time from a time of irradiation of the target with the second pre-pulse laser beam, to a time of irradiation of the target. target with the third pre-pulse laser beam, and a fourth delay time from a moment of irradiation of the target with the third pre-pulse laser beam, to a moment of irradiation of the target with the main pulse laser beam, are in the following relationship to each other:
    the first delay time <the fourth delay time <the third delay time.
    [17]
    The extreme ultraviolet light generation system of claim 12, wherein the laser system comprises a CO2 laser device configured to provide the third pre-pulse laser beam and the main pulse laser beam.
    [18]
    18. A method of manufacturing an electronic device, comprising: generating extreme ultraviolet light by irradiating a target with a pulsed laser beam in an extreme ultraviolet light generation system; delivering extreme ultraviolet light to an exposure device; and exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus to manufacture an electronic device, the extreme ultraviolet light generating system comprising: a chamber; a target generation unit configured to deliver a target to a predetermined region in the chamber; a laser system configured to provide a first pre-pulse laser beam, a second pre-pulse laser beam, and a main pulse laser beam to irradiate the target with the first pre-pulse laser beam, the second pre-pulse laser beam, and the main pulse laser beam in this sequence so that the smoothness of the first pre-pulse laser beam is 1.5 J / cm2 to 16 J / cm2, at a position where the target is irradiated with the first pre-pulse laser beam; and a control unit adapted to control the laser system such that a first delay time from a moment of irradiation of the target with the first pre-pulse laser beam, to a moment of irradiation of the target with the second pre-pulse laser beam, and a second delay time from a moment of irradiation of the target with the second pre-pulse laser beam, to a moment of irradiation of the target with the main pulse laser beam, meet the following relationship: the first delay time <the second delay time.
    [19]
    19. Manufacturing method of an electronic device, comprising:
    generating extreme ultraviolet light by irradiating a target with a pulsed laser beam in an extreme ultraviolet light generation system; delivering extreme ultraviolet light to an exposure device; and exposing a photosensitive substrate to the extreme ultraviolet light in the exposure apparatus to manufacture an electronic device, the extreme ultraviolet light generating system comprising: a chamber; a target generation unit configured to deliver a target to a predetermined region in the chamber; a laser system configured to provide a first pre-pulse laser beam having a pulse time width on the order of nanoseconds, a second pre-pulse laser beam having a pulse time width on the order of picoseconds, a third pre-pulse laser beam, and a main pulse laser beam so as to irradiating the target with the first pre-pulse laser beam, the second pre-pulse laser beam, the third pre-pulse laser beam and the main pulse laser beam in this order, and a control unit adapted to control the laser system so that a first delay time of a moment from irradiation of the target with the first pre-pulse laser beam, to a moment of irradiation of the target with the second pre-pulse laser beam, and a second delay time from a moment of irradiation of the target with the second pre-pulse laser beam, to a moment of irradiating the target with the main pulse laser beam to satisfy the following relationship: the first delay time <the second delay time.
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    引用文献:
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    US8791440B1|2013-03-14|2014-07-29|Asml Netherlands B.V.|Target for extreme ultraviolet light source|
    US20160073487A1|2013-05-31|2016-03-10|Gigaphoton Inc.|Extreme ultraviolet light generation system|
    WO2018083727A1|2016-11-01|2018-05-11|ギガフォトン株式会社|Extreme uv light generation device|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    JP2019135009A|JP2021018364A|2019-07-23|2019-07-23|Extreme ultraviolet light generating system, and method for manufacturing electronic device|
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