LPP EUV light source employing high power C0 2 laser

Hoshino, Hideo; Suganuma, Takashi; Asayama, Takeshi; Nowak, K.; Moriya, Masato; Abe, Tamotsu; Endo, Akira; Sumitani, Akira

doi:10.1117/12.771847

Cited by 24 publications

(10 citation statements)

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“…The forced rapid flow of the laser gas allowed for an increased RF power input with− out an adverse overheating of the gas medium, resulting in higher output power levels as compared to their diffusion− −cooled counterpart but at an expense of additional system complexity (blowers, heat exchangers, etc.). However, being the largest lasers available commercially, these sys− tems are of interest because they can be used in a pulsed laser design as power amplifiers [61][62][63]. Presently a record output power of 20 kW (CW) from a small package belongs to the TrueFlow FAF laser series from Trumpf GmbH.…”

Section: Brief Overview Of Relevant Co 2 Laser Technologymentioning

confidence: 99%

“…The exponentially−like rising pedestal is undesired because it gets amplified preferentially and leads to an uncontrollable pulse width broadening. This kind of master oscillator, employing the sealed−off RF−discharge excited waveguide laser was employed previously in LPP EUV source development [76,77,61].…”

Section: Robust Generation Of Short Pulses For Lppmentioning

confidence: 99%

“…REE in− creases with pulse frequency and decreases with the increas− ing gas pressure p, a result of different scaling laws for rele− vant medium parameters, the saturation energy fluence (sca− ling in proportion to p) and saturation intensity (scaling in proportion to p 2 ). In case of 10-20ns pulse and 100 kHz rep− etition frequency, REE was found to be 30-40% in a 15 kW FAF amplifier operating at~150 Torr gas mix pressure [61], and about 50-60% measured in amplifiers operating at~50 Torr [84]. Figure 9 shows REE as a function of drive input power for a 15 kW single−pass FAF amplifier.…”

Section: Efficient Amplification Of Short Pulses In Typical Co 2 Mediamentioning

confidence: 99%

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CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

Nowak

Ohta

Suganuma

et al. 2013

Opto-Electronics Review

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It was shown both theoretically and experimentally that nanosecond order laser pulses at 10.6 micron wavelength were superior for driving the Sn plasma extreme ultraviolet (EUV) source for nano-lithography for the reasons of higher conversion efficiency, lower production of debris and higher average power levels obtainable in CO2 media without serious problems of beam distortions and nonlinear effects occurring in competing solid-state lasers at high intensities. The renewed interest in such pulse format, wavelength, repetition rates in excess of 50 kHz and average power levels in excess of 18 kiloWatt has sparked new opportunities for a matured multi-kiloWatt CO2 laser technology. The power demand of EUV source could be only satisfied by a Master-Oscillator-Power-Amplifier system configuration, leading to a development of a new type of hybrid pulsed CO2 laser employing a whole spectrum of CO2 technology, such as fast flow systems and diffusion-cooled planar waveguide lasers, and relatively recent quantum cascade lasers. In this paper we review briefly the history of relevant pulsed CO2 laser technology and the requirements for multi-kiloWatt CO2 laser, intended for the laser-produced plasma EUV source, and present our recent advances, such as novel solid-state seeded master oscillator and efficient multi-pass amplifiers built on planar waveguide CO2 lasers.

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Section: Brief Overview Of Relevant Co 2 Laser Technologymentioning

confidence: 99%

Section: Robust Generation Of Short Pulses For Lppmentioning

confidence: 99%

Section: Efficient Amplification Of Short Pulses In Typical Co 2 Mediamentioning

confidence: 99%

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CO2 laser drives extreme ultraviolet nano-lithography — second life of mature laser technology

Nowak

Ohta

Suganuma

et al. 2013

Opto-Electronics Review

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“…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%

“…These procedures are limited to low repetition rates due to the background gas renewal time and control of spatial stability can be an issue. Q-switched pulse shortening 11,12 has also been demonstrated, but the output energies need to be small to avoid damage to optical components. Short pulse production by mode locking 13 schemes also suffer from this drawback.…”

Section: Introductionmentioning

confidence: 99%

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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