Ablation dynamics of tin micro-droplet irradiated by double pulse laser used for extreme ultraviolet lithography source

Nakamura, Daisuke; Akiyama, Tsuyoshi; Okazaki, Ken; Tamaru, K.; Takahashi, Akihiko; Okada, Tatsuo

doi:10.1088/0022-3727/41/24/245210

Cited by 10 publications

(6 citation statements)

References 16 publications

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“…In Fig. 5 we present our model predictions for the sensitivity θ tilt /∆x as function of beam width σ around zero misalignment (∆x = 0) for several values of the effective droplet size R eff = [10,15,25,35,50] µm. We note that by plotting for several effective droplet sizes R eff , we incorporate both the droplet size R 0 and the distance from the droplet surface to the plasma critical surface d crit for each case, since R eff = R 0 + d crit (see previous section).…”

Section: Discussion and Industrial Applicationmentioning

confidence: 99%

“…Maximizing the conversion efficiency (CE) of laser light into the required EUV light of such sources requires a careful control over the target shape. This shape is very sensitive to the precise alignment of the prepulse laser to the initially spherical droplet 10,11 . Any deviation from the optimum location for laser impact will produce a suboptimal target tilt and decrease the target radial expansion, as shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The curves are the analytically calculated tilt angle sensitivities from Eq. (5), with δp = 0.6 and for several relevant values for the effective droplet size R eff =[10,15, 25, 35, 50] µm. The red square, green diamond and blue circle represent the values corresponding to the experimental conditions (see Section IV, color coding as in Fig.3).…”

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confidence: 99%

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Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Reijers

Kurilovich

Torretti

et al. 2018

Journal of Applied Physics

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We present and experimentally validate a model describing the sensitivity of the tilt angle, expansion and propulsion velocity of a tin micro-droplet irradiated by a 1 µm Nd:YAG laser pulse to its relative alignment. This sensitivity is particularly relevant in industrial plasma sources of extreme ultraviolet light for nanolithographic applications. Our model has but a single parameter: the dimensionless ratio of the laser spot size to the effective size of the droplet, which is related to the position of the plasma critical density surface. Our model enables the development of straightforward scaling arguments in turn enabling precise control the alignment sensitivity.

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Section: Discussion and Industrial Applicationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Reijers

Kurilovich

Torretti

et al. 2018

Journal of Applied Physics

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show abstract

“…Despite its importance for EUV lithography, literature on the production of in-band radiation from mass-limited, prepulse deformed targets remains rather scarce, with the majority of studies to-date focusing on λ = 10 µm main pulses (see, e.g. [29,[40][41][42]). A broad body of literature has investigated experimentally the emission from undeformed liquid tin droplet targets [9,34,43,44], coated spheres [45] or solidplanar targets [46][47][48][49] using 1 µm solid-state lasers.…”

Section: Introductionmentioning

confidence: 99%

Characterization of angularly resolved EUV emission from 2-µm-wavelength laser-driven Sn plasmas using preformed liquid disk targets

Schupp

Behnke

Bouza

et al. 2021

J. Phys. D: Appl. Phys.

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The emission properties of tin plasmas, produced by the irradiation of preformed liquid tin targets by several-ns-long 2 µm-wavelength laser pulses, are studied in the extreme ultraviolet (EUV) regime. In a two-pulse scheme, a pre-pulse laser is first used to deform tin microdroplets into thin, extended disks before the main (2 µm) pulse creates the EUV-emitting plasma. Irradiating 30-to 300 µm-diameter targets with 2 µm laser pulses, we find that the efficiency in creating EUV light around 13.5 nm follows the fraction of laser light that overlaps with the target. Next, the effects of a change in 2 µm drive laser intensity (0.6-1.8 × 10 11 W cm −2 ) and pulse duration (3.7-7.4 ns) are studied. It is found that the angular dependence of the emission of light within a 2% bandwidth around 13.5 nm and within the backward 2π hemisphere around the incoming laser beam is almost independent of intensity and duration of the 2 µm drive laser. With increasing target diameter, the emission in this 2% bandwidth becomes increasingly anisotropic, with a greater fraction of light being emitted into the hemisphere of the incoming laser beam. For direct comparison, a similar set of experiments is performed with a 1 µm-wavelength drive laser. Emission spectra, recorded in a 5.5-25.5 nm wavelength range, show significant self-absorption of light around 13.5 nm in the 1 µm case, while in the 2 µm case only an opacity-related broadening of the spectral feature at 13.5 nm is observed. This work demonstrates the enhanced capabilities and performance of 2 µm-driven plasmas produced from disk targets when compared to 1 µm-driven plasmas, providing strong motivation for the use of 2 µm lasers as drive lasers in future high-power sources of EUV light.

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“…Despite its importance for EUV lithography, literature on the production of in-band radiation from mass-limited, prepulse deformed targets remains rather scarce, with the majority of studies to-date focusing on λ = 10 µm main pulses (see, e.g., [28,[38][39][40]). A broad body of literature has investigated experimentally the emission from undeformed liquid tin droplet targets [9,32,41,42], coated spheres [43] or solidplanar targets [44][45][46][47] using 1-µm solid-state lasers.…”

Section: Introductionmentioning

confidence: 99%

Characterization of angularly resolved EUV emission from 2-$μ$m-wavelength laser-driven Sn plasmas using preformed liquid disk targets

Schupp,

Behnke,

Bouza

et al. 2021

Preprint

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The emission properties of tin plasmas, produced by the irradiation of preformed liquid tin targets by severalns-long 2-µm-wavelength laser pulses, are studied in the extreme ultraviolet (EUV) regime. In a two-pulse scheme, a pre-pulse laser is first used to deform tin microdroplets into thin, extended disks before the main (2 µm) pulse creates the EUV-emitting plasma. Irradiating 30-to 300-µm-diameter targets with 2-µm laser pulses, we find that the efficiency in creating EUV light around 13.5 nm follows the fraction of laser light that overlaps with the target. Next, the effects of a change in 2-µm drive laser intensity (0.6-1.8 × 10 11 W/cm 2 ) and pulse duration (3.7-7.4 ns) are studied. It is found that the angular dependence of the emission of light within a 2% bandwidth around 13.5 nm and within the backward 2π hemisphere around the incoming laser beam is almost independent of intensity and duration of the 2-µm drive laser. With increasing target diameter, the emission in this 2% bandwidth becomes increasingly anisotropic, with a greater fraction of light being emitted into the hemisphere of the incoming laser beam. For direct comparison, a similar set of experiments is performed with a 1-µm-wavelength drive laser. Emission spectra, recorded in a 5.5-25.5 nm wavelength range, show significant self-absorption of light around 13.5 nm in the 1-µm case, while in the 2-µm case only an opacity-related broadening of the spectral feature at 13.5 nm is observed. This work demonstrates the enhanced capabilities and performance of 2-µm-driven plasmas produced from disk targets when compared to 1-µmdriven plasmas, providing strong motivation for the use of 2-µm lasers as drive lasers in future high-power sources of EUV light.

show abstract

Ablation dynamics of tin micro-droplet irradiated by double pulse laser used for extreme ultraviolet lithography source

Cited by 10 publications

References 16 publications

Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Laser-to-droplet alignment sensitivity relevant for laser-produced plasma sources of extreme ultraviolet light

Characterization of angularly resolved EUV emission from 2-µm-wavelength laser-driven Sn plasmas using preformed liquid disk targets

Characterization of angularly resolved EUV emission from 2-$μ$m-wavelength laser-driven Sn plasmas using preformed liquid disk targets

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