Optimizing 13.5nm laser-produced tin plasma emission as a function of laser wavelength

White, J.; Dunne, Padraig; Hayden, P.; O’Reilly, Fergal; O’Sullivan, Gerry

doi:10.1063/1.2735944

Cited by 64 publications

(48 citation statements)

References 30 publications

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“…Satellite emission at wavelengths longer than 7 nm, on the other hand, is increased using the 532-nm and 355-nm wavelengths. The decrease of the 6.7-nm emission is attributed to selfabsorption in the denser, short-wavelength plasma [17]. This behavior is supported by the dual laser irradiation experiment to control the electron density gradient, i.e., the absorption length [7,18].…”

supporting

confidence: 49%

Systematic investigation of self-absorption and conversion efficiency of 6.7 nm extreme ultraviolet sources

Ôtsuka

Kilbane

Higashiguchi

et al. 2010

Applied Physics Letters

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We have investigated the dependence of the spectral behavior and conversion efficiencies of rare-earth plasma extreme ultraviolet sources with peak emission at 6.7 nm on laser wavelength and the initial target density. The maximum conversion efficiency was 1.3% at a laser intensity of 1.6×1012 W/cm2 at an operating wavelength of 1064 nm, when self-absorption was reduced by use of a low initial density target. Moreover, the lower-density results in a narrower spectrum and therefore improved spectral purity. It is shown to be important to use a low initial density target and/or to produce low electron density plasmas for efficient extreme ultraviolet sources when using high-Z targets.

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supporting

confidence: 49%

Systematic investigation of self-absorption and conversion efficiency of 6.7 nm extreme ultraviolet sources

Ôtsuka

Kilbane

Higashiguchi

et al. 2010

Applied Physics Letters

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“…Earlier techniques relied on focusing the laser pulse in a background gas to form a plasma shutter. [5][6][7] Plasma formation occurs at a definite time during the laser pulse and the remaining part of the pulse is Temporal profile of a TEA CO 2 laser pulse showing the two temporal components; a short intense first peak (1) followed by a second low energy long duration peak (2). The graph inset shows a close up of the first peak.…”

Section: Introductionmentioning

confidence: 99%

“…An example of a TEA CO 2 laser pulse profile is shown in Fig. 1 where the initial peak (1) and the long tail (2) are marked. The laser pulse temporal profile is problematic for two reasons.…”

Section: Introductionmentioning

confidence: 99%

“…1 This is partly due to the favorable opacity conditions that result in enhanced EUV emission when laser produced plasmas (LPPs) are formed with far infrared laser irradiation compared with those formed using optical and near infrared lasers. 2 LPP emission in a 2% band centered on 13.5 nm is the leading candidate as the source for next-generation photolithography in high-volume manufacturing of computer processors and memory components. 1 To optimize the EUV emission, the tin LPP should have an electron temperature in the region of 35 eV, where the dominant ions are Sn 8+ to Sn 10+ , resulting in a narrow band of bright emission at 13.5 nm.…”

Section: Introductionmentioning

confidence: 99%

“…Moving to shorter wavelength sources for lithography beyond 13.5 nm, amplified, short CO 2 pulses could be used to excite plasmas containing gadolinium for 6.76 nm sources. 4 Several methods of producing shortened CO 2 laser pulses have been previously demonstrated, [5][6][7][8][9][10][11][12][13][14] with varying degrees of complexity and success. Earlier techniques relied on focusing the laser pulse in a background gas to form a plasma shutter.…”

Section: Introductionmentioning

confidence: 99%

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CO2 laser pulse shortening by laser ablation of a metal target

Donnelly

Mazoyer²,

Lynch³

et al. 2012

Review of Scientific Instruments

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A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO2 laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ∼2 ns and to remove the low power, long duration tails that are present in TEA CO2 pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ∼10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.

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