Comparison of EUV spectral and ion emission features from laser-produced Sn and Li plasmas

Coons, R. W.; Campos, D; Crank, Matthew; Harilal, S. S.; Hassanein, A.

doi:10.1117/12.848318

Cited by 12 publications

(8 citation statements)

References 14 publications

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“…Vertical scattering at 10 J/cm 2 shows that unlike ns-lasers, the maximum energy of H + ions is effectively generated by 100fs XFEL pulses. However, the slowest H + ions were emitted from the 14 Si target, the fastest from the 28 Ni and 29 Cu targets. The maximum kinetic energy of Ni and Cu target ions produced in this experiment is about 50-60 times higher than that of H + ions (not shown in Figure 4).…”

Section: Resultsmentioning

confidence: 99%

Ion emission from plasmas produced by femtosecond pulses of short-wavelength free-electron laser radiation focused on massive targets: an overview and comparison with long-wavelength laser ablation

Krása,

Nassisi,

Burian

et al. 2023

Optics Damage and Materials Processing by EUV/X-ray Radiation (XDam8)

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We report on ion emission from plasma produced on thick targets irradiated with nanosecond and femtosecond pulses delivered by mid-ultraviolet and soft x-ray lasers, respectively. To distinguish between different ion acceleration mechanisms, the maximum kinetic energy of ions produced under different interaction conditions is plotted versus laser fluence. The transformation of the time-of-flight detector signal into ion charge density distance-of-flight spectra makes it possible to determine the mean kinetic energy of the fastest ion groups based on the influence of the acoustic velocity of ion expansion. This allows obtaining additional characteristics of the ion production. The final energy of the group of fast ions determined using the ion sound velocity model is an order of magnitude larger in the fs-XFEL interaction than in the ns-UV one. On the contrary, the ablation yield of ions in our experiment is seven orders of magnitude greater when applying ns-UV laser pulses, not only due to higher energies of UV laser pulses, but also due to a significant difference in interaction and ion formation mechanisms.

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Section: Resultsmentioning

confidence: 99%

Ion emission from plasmas produced by femtosecond pulses of short-wavelength free-electron laser radiation focused on massive targets: an overview and comparison with long-wavelength laser ablation

Krása,

Nassisi,

Burian

et al. 2023

Optics Damage and Materials Processing by EUV/X-ray Radiation (XDam8)

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“…For larger focal spots there is increased coupling between the plasma and laser due to the cylindrical expansion; as the laser energy is now shared between a greater number of emitting ions a lower average charge is obtained but an increase in continuum emission is observed for the same reason, bremsstrahlung emission scales with ξ Av 2 n i , where n i is the ion density. It is also worth noting the increased scale length for larger focal spots leads to greater self-absorption and emission from lower ion stages at longer wavelengths from recombined ions and free electrons in the outer plasma [45,46].…”

Section: Influence Of Spot Size On Plasma Expansionmentioning

confidence: 99%

An Investigation of Laser Produced Lead-Tin Alloy Plasmas between 10 and 18 nm

Scally

O’Reilly

Hayden

et al. 2020

Atoms

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The results of a systematic study performed on Pb-Sn alloys of concentration 65–35% and 94–6% by weight along with spectra from pure Pb and Sn in the wavelength range of 9.8–18 nm are presented. The dynamics of the Nd:YAG laser produced plasma were changed by varying the focused spot size and input energy of the laser pulse; the laser irradiance at the target varied from 7.3 × 109 W cm−2 to 1.2 × 1012 W cm−2. The contributing ion stages and line emission are identified using the steady state collisional radiative model of Colombant and Tonon, and the Cowan suite of atomic structure codes. The Sn spectrum was dominated in each case by the well-known unresolved transition array (UTA) near 13.5 nm. However, a surprising result was the lack of any enhancement or narrowing of this feature at low concentrations of Sn in the alloy spectra whose emission was essentially dominated by Pb ions.

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“…One of these issues is the need for collector cleaning and replacement. EUV is made by irradiating a small Sn droplet with a high-power laser and highly ionizing the Sn, which gives off 13.5nm EUV photons through transitions in the +8 -+13 ionization states [1]. Due to the absence of a material with sufficiently low EUV absorption, transparent lenses are not possible; the EUV photons must be focused by a series of expensive Bragg reflectors, which are made of alternating layers of Mo and Si, each only a few nm thick [2].…”

Section: Introductionmentioning

confidence: 99%

Collector optic cleaning by in-situ hydrogen plasma

et al. 2015

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Extreme ultraviolet (EUV) lithography sources produce EUV photons by means of a hot, dense, highly-ionized Sn plasma. This plasma expels high-energy Sn ions and neutrals, which deposit on the collector optic used to focus the EUV light. This Sn deposition lowers the reflectivity of the collector optic, necessitating downtime for collector cleaning and replacement. A method is being developed to clean the collector with an in-situ hydrogen plasma, which provides hydrogen radicals that etch the Sn by forming gaseous SnH 4 . This method has the potential to significantly reduce collector-related source downtime. EUV reflectivity restoration and Sn cleaning have been demonstrated on multilayer mirror samples attached to a Sn-coated 300mm-diameter steel dummy collector driven at 300W RF power with 500sccm H 2 and a pressure of 260mTorr. Use of the in-situ cleaning method is also being studied at industriallyapplicable high pressure (1.3 Torr). Plasma creation across the dummy collector surface has been demonstrated at 1.3 Torr with 1000sccm H 2 flow, and etch rates have been measured. Additionally, etching has been demonstrated at higher flow rates up to 3200sccm. A catalytic probe has been used to measure radical density at various pressures and flows. The results lend further credence to the hypothesis that Sn removal is limited not by radical creation but by the removal of SnH 4 from the plasma. Additionally, further progress has been made in an attempt to model the physical processes behind Sn removal.

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Comparison of EUV spectral and ion emission features from laser-produced Sn and Li plasmas

Cited by 12 publications

References 14 publications

Ion emission from plasmas produced by femtosecond pulses of short-wavelength free-electron laser radiation focused on massive targets: an overview and comparison with long-wavelength laser ablation

Ion emission from plasmas produced by femtosecond pulses of short-wavelength free-electron laser radiation focused on massive targets: an overview and comparison with long-wavelength laser ablation

An Investigation of Laser Produced Lead-Tin Alloy Plasmas between 10 and 18 nm

Collector optic cleaning by in-situ hydrogen plasma

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