Mitigation of fast ions from laser-produced Sn plasma for an extreme ultraviolet lithography source

Tao, Y.; Tillack, M. S.

doi:10.1063/1.2349831

Cited by 20 publications

(9 citation statements)

References 13 publications

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“…In Tao and Tillack's paper, the 13.5 nm intensity increased by 10 % when the delay was less than 20 ns, and dropped with a delay time up to 200 ns to about half, then recovered slowly with a delay time. 21 This is similar to our observations shown in Fig. 2.…”

Section: -9supporting

confidence: 83%

“…As discussed by Aota and Tomie, 18 the laser absorption coefficient is proportional to the square of the electron density, and a plasma becomes transparent to a laser when the density is low. The initial density of a pre-formed plasma generated on the surface of the Gd plate will be a little lower than 4x10 21 /cm 3 which corresponds to the critical density of the 532nm pre-pulse laser. The plasma density decreases with expansion, and it will become transparent to the main pulse when the density becomes much lower than 1x10 21 /cm 3 which is the critical density of 1064nm light.…”

Section: -mentioning

confidence: 99%

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Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

et al. 2016

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For effective use of a laser-produced-plasma (LPP) light source, an LPP is desired to emit a narrow spectral peak because the reflection spectrum of multilayer mirrors for guiding emission from the source is very narrow. While a Gd plasma has been studied extensively as an extreme ultraviolet (EUV) light source at around 6.8 nm, where La/B4C multilayer is reported to have a high reflectivity with a bandwidth of about 0.6 %, all previous works using an Nd:YAG laser reported very broad spectra. This paper reports the first narrowing of the 6.8 nm peak in the case of using an Nd:YAG laser to generate a Gd plasma by using a pre-pulse. The best peak narrowing is observed when a pre-formed plasma is heated by a 1064 nm main laser pulse with a duration of 10 ns at the irradiation density of 4x 1011 W/cm2 at a delay time of 50 ns after the pre-pulse irradiation. The observed spectral width of about 0.3 nm is about one fifth of the value for no pre-formed plasma. The peak wavelength of the 6.8 nm band shifted to a longer wavelength side and the peak was broadened both for lower and higher laser irradiation density. It is discussed that this robustness of the peak position of the 6.8 nm Gd peak against temperature change is suitable to achieve a narrow bandwidth from an LPP generated on solid. The observed spectra are compared with those previously reported in various conditions.

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Section: -9supporting

confidence: 83%

Section: -mentioning

confidence: 99%

Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

et al. 2016

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“…8 On the other hand, suppression of the suprathermal ion energy by using a low-density plasma has been demonstrated with a view to minimizing the debris. [9][10][11][12] To develop a practical EUV source, we chose to use a regenerative liquid microjet target containing SnO 2 nanoparticles with double pulse irradiation. By using double laser pulses with liquid microjet target, we could simultaneously maximize the EUV emissions and minimize the suprathermal ion and debris emissions.…”

mentioning

confidence: 99%

Suppression of suprathermal ions from a colloidal microjet target containing SnO2 nanoparticles by using double laser pulses

Higashiguchi¹,

Kaku

Katto

et al. 2007

Applied Physics Letters

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We have demonstrated suppression of suprathermal ions from a colloidal microjet target plasma containing tin-dioxide (SnO2) nanoparticles irradiated by double laser pulses. We observed a significant decrease of the tin and oxygen ion signals in the charged-state-separated energy spectra when double laser pulses were irradiated. The peak energy of the singly ionized tin ions decreased from 9to3keV when a preplasma was produced. The decrease in the ion energy, considered as debris suppression, is attributed to the interaction between an expanding low-density preplasma and a main laser pulse.

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“…5 Recently we demonstrated a much larger reduction factor of 30 in ion energy from a laser-produced Sn plasma by introducing a low energy prepulse. 9 However, the mechanism dominating the phenomena was not clear until now. Further understanding of the effect of initial density profile on ion acceleration is not only necessary for the development of an EUV lithography source but also for other applications of laser plasma, such as laser ion acceleration, laser fusion, soft and hard x-ray sources, and pulsed laser deposition ͑PLD͒.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the interaction of a laser pulse with a preformed Gaussian Sn plume for an extreme ultraviolet lithography source

Tao

Tillack

Harilal

et al. 2007

Journal of Applied Physics

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The interaction of a laser pulse with a Sn preplasma formed by a low energy prepulse was investigated for an extreme ultraviolet ͑EUV͒ lithography light source. A much lower ion kinetic energy and nearly the same conversion efficiency from laser to in-band ͑2% bandwidth͒ 13.5 nm EUV light were simultaneously observed as compared with those from the direct interaction with a solid surface. The reason comes from the interaction of the laser pulse with a smooth preplume induced by the prepulse. The density profile of the preplume was measured with time-resolved shadowgraphy and could be fitted with a Gaussian function. The energy of the ions located at the flux peak E p scales with the length of the preplume l s as E p ϰ 1/l s . Laser absorption in the low-density preplume and ion acceleration during plasma expansion are discussed. This result provides a general way to control particle energy from a laser plasma interaction.

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Mitigation of fast ions from laser-produced Sn plasma for an extreme ultraviolet lithography source

Cited by 20 publications

References 13 publications

Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

Sharpening of the 6.8 nm peak in an Nd:YAG laser produced Gd plasma by using a pre-formed plasma

Suppression of suprathermal ions from a colloidal microjet target containing SnO2 nanoparticles by using double laser pulses

Investigation of the interaction of a laser pulse with a preformed Gaussian Sn plume for an extreme ultraviolet lithography source

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