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Journal Articles

Modeling of initial interaction between the laser pulse and Sn droplet target and pre-plasma formation for the LPP EUV source

Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Nishikawa, Takeshi*

Proceedings of SPIE, Vol.9776, p.97762C_1 - 97762C_6, 2016/03

 Times Cited Count:1 Percentile:55.95

For the improvement of efficiency and output of the laser pumped plasma (LPP) extreme ultra-violet (EUV) light source, we present a hydrodynamics model of laser irradiated Sn targets. The model takes liquid/solid to gas transition and mixed phase condition of the flow into account for the calculation of the distribution of the particles produced by the pre-pulse laser irradiation and optimization of the EUV source. Firstly, we investigate the mechanisms of the fragmentation of the target and particle emission, including the effect of the equation of state of Sn, and secondly, an applicable model is proposed based on the analysis.

Journal Articles

Prepulse and amplified spontaneous emission effects on the interaction of a petawatt class laser with thin solid targets

Esirkepov, T. Z.; Koga, J. K.; Sunahara, Atsushi*; Morita, Toshimasa; Nishikino, Masaharu; Kageyama, Kei*; Nagatomo, Hideo*; Nishihara, Katsunobu; Sagisaka, Akito; Kotaki, Hideyuki; et al.

Nuclear Instruments and Methods in Physics Research A, 745, p.150 - 163, 2014/05

 Times Cited Count:40 Percentile:96.82(Instruments & Instrumentation)

Journal Articles

Atomic processes and radiation hydrodynamics

Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*

Purazuma, Kaku Yugo Gakkai-Shi, 89(10), p.654 - 658, 2013/10

no abstracts in English

Journal Articles

Modeling of atomic processes of multiple charged ions in plasmas and its application to the study of EUV light sources

Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Furukawa, Hiroyuki*; Nishikawa, Takeshi*; Koike, Fumihiro*

Plasma and Fusion Research (Internet), 6(Sp.1), p.2401145_1 - 2401145_4, 2011/12

Atomic processes and radiation from multiple charged ions in plasmas are of the interest in the investigation of plasma wall interaction and transport of impurity ions in the fusion devices. The emission from multiple charged ions is also investigated for the development of extreme ultra violet light (EUVL) sources at $$lambda=13.5 nm$$. Efficient emission through the 4d-4f + 4p-4d transition array is obtained from tin ions. An optimization of pumping conditions of laser produced plasma sources is carried out theoretically and experimentally. We also investigate an extension of the plasma light sources to short wavelength to $$lambda=6.5 nm$$ using Gd and Tb plasmas. We discuss requirements to the atomic structure, rate coefficient and collisional radiative codes to determine ion abundance and level population as a function of plasma temperature and density, to calculate the radiation intensity as well as emission spectrum.

Journal Articles

Theoretical investigation of the spectrum and conversion efficiency of short wavelength extreme-ultraviolet light sources based on terbium plasmas

Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Furukawa, Hiroyuki*; Nishikawa, Takeshi*; Koike, Fumihiro*

Applied Physics Letters, 97(23), p.231501_1 - 231501_3, 2010/12

 Times Cited Count:14 Percentile:52.65(Physics, Applied)

Emission spectrum and conversion efficiency of laser produced terbium plasmas are investigated theoretically on the basis of computational atomic data. It is shown that calculation reproduces the main peak of the experimental spectrum at $$lambda=6.5$$nm, which originates from 4$$d$$-4$$f$$ transitions of near palladium like ions (Tb$$^{19+}$$). Simple model of the isothermal expansion of plasma suggests that efficient emission can be obtained by pumping a plasma with a laser pulse with an intensity approximately one order of magnitude grater than in the case of tin sources at $$lambda=13.5$$nm.

Journal Articles

Physics and future of the laser pumped plasma XUV sources

Sasaki, Akira; Nishihara, Katsunobu*

Reza Kenkyu, 38(12), p.969 - 975, 2010/12

Extension of the laser pumped plasma (LPP) EUV source toward shorter wavelength is discussed. Properties of the emission from the 4d-4f + 4p-4d transition array of 4d open-shell ions, which has been used for the lithographic EUV source at $$lambda$$=13.5nm using Sn target, are investigated. Using calculated emissivity, opacity, and spectral efficiency, the conversion efficiency (CE) for each ion at their characteristic emission wavelength is investigated, showing the LPP can be scalable down to $$lambda$$=6.5nm using Gd target, even the estimated irradiation intensity of $$10^{11} rm W/cm^2$$ demands considerable improvement of laser technologies. Possibility and further requirement to the theoretical method for the prediction of the performance of LPP EUV source are also discussed.

Journal Articles

Modeling of radiative properties of Sn plasmas for extreme-ultraviolet source

Sasaki, Akira; Sunahara, Atsushi*; Furukawa, Hiroyuki*; Nishihara, Katsunobu*; Fujioka, Shinsuke*; Nishikawa, Takeshi*; Koike, Fumihiro*; Ohashi, Hayato*; Tanuma, Hajime*

Journal of Applied Physics, 107(11), p.113303_1 - 113303_11, 2010/06

 Times Cited Count:33 Percentile:77.78(Physics, Applied)

Atomic processes in Sn plasmas are investigated for application to extreme-ultraviolet (EUV) light sources used in microlithography. An atomic model of Sn is developed on the basis of calculated atomic data using the Hebrew University Lawrence Livermore Atomic Code (HULLAC). Resonance and satellite lines from singly and multiply excited states of Sn ions are identified. The wavelengths of the 4$$d$$-4$$f$$ + 4$$p$$-4$$d$$ transitions of Sn$$^{5+}$$ to Sn$$^{13+}$$ are investigated. Results of calculation are compared with those of the charge exchange spectroscopy, measurement of the emission spectrum of the laser produced plasma EUV source, and the opacity measurement of a radiatively heated Sn sample. A reasonable agreement is observed between calculated and experimental EUV emission spectra. The spectral emissivity and opacity of Sn plasmas are calculated using a full collisional radiative (CR) model as a function of electron temperature and ion density.

Journal Articles

Atomic modeling of the plasma EUV sources

Sasaki, Akira; Sunahara, Atsushi*; Furukawa, Hiroyuki*; Nishihara, Katsunobu*; Nishikawa, Takeshi*; Koike, Fumihiro*; Tanuma, Hajime*

High Energy Density Physics, 5(3), p.147 - 151, 2009/09

 Times Cited Count:9 Percentile:36.1(Physics, Fluids & Plasmas)

We study the radiative properties of the EUV source to address conditions to achieve an output power and efficiency required for its application to the next generation microlithography. An atomic model is developed based on the atomic data calculated by Hullac code, which is validated through detailed comparisons with experimental emission and a absorption spectra. The atomic model is improved with respect to the wavelength of the strong emission lines, and the number of satellite channels taken into account. As a result, the radiation hydrodynamics model is shown to successfully reproduce the experiments. We show Sn plasma is more efficient than Xe plasma because of the atomic number dependence of the emission wavelength, and the use of CO$$_{2}$$ lasers as a pumping source has an advantage to reduce satellite contribution and to have narrower emission spectrum to obtain higher conversion efficiency.

Journal Articles

Low-threshold ablation of dielectrics irradiated by picosecond soft X-ray laser pulses

Faenov, A. Y.; Inogamov, N. A.*; Zhakhovskii, V. V.*; Khokhlov, V. A.*; Nishihara, Katsunobu*; Kato, Yoshiaki*; Tanaka, Momoko; Pikuz, T. A.*; Kishimoto, Maki; Ishino, Masahiko; et al.

Applied Physics Letters, 94(23), p.231107_1 - 231107_3, 2009/06

 Times Cited Count:42 Percentile:82.49(Physics, Applied)

Journal Articles

The Atomic model of the Sn plasmas for the EUV sources

Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*; Nishikawa, Takeshi*; Koike, Fumihiro*; Tanuma, Hajime*

Journal of Physics; Conference Series, 163, p.012107_1 - 012107_4, 2009/06

 Times Cited Count:5 Percentile:85.65

no abstracts in English

Journal Articles

Complementary spectroscopy of tin ions using ion and electron beams

Ohashi, Hayato*; Suda, Shintaro*; Tanuma, Hajime*; Fujioka, Shinsuke*; Nishimura, Hiroaki*; Nishihara, Katsunobu*; Kai, Takeshi; Sasaki, Akira; Sakaue, Hiroyuki*; Nakamura, Nobuyuki*; et al.

Journal of Physics; Conference Series, 163, p.012071_1 - 012071_4, 2009/06

 Times Cited Count:7 Percentile:89.94

Extreme ultra-violet (EUV) emission spectra of multiply charged tin ions were measured in the wavelength range of 10-22 nm following charge exchange collisions or the electron impact excitation of tin ions. In charge exchange collisions, we observed both the resonance lines and the emission lines corresponding to the transitions between the excited states. On the other hand, we observed mainly the resonance lines in the electron impact experiments. We can distinguish the resonance lines from other emission lines in the charge exchange spectrum by comparison with the emission lines in the electron impact spectrum.

Journal Articles

Atomic processes in the LPP and LA-DPP EUV sources

Sasaki, Akira; Nishihara, Katsunobu*; Sunahara, Atsushi*; Furukawa, Hiroyuki*; Nishikawa, Takeshi*; Koike, Fumihiro*

Alternative Lithographic Technologies (Proceedings of SPIE Vol.7271), p.727130_1 - 727130_8, 2009/03

We investigate characteristic feature of the atomic radiation from tin plasmas, which allow one to obtain high power EUV emission efficiently. We develop a collisional radiative model of tin ions to calculate steady-state and time dependent ion abundance, level population, and coefficients of radiative transfer of the plasma. The model, which is based atomic data calculated using the Hullac code is refined both theoretically and experimentally. Calculation of the spectral emissivity and opacity are carried out over a wide range of plasma density and temperature, and pumping conditions to obtain high conversion efficiency are discussed.

Journal Articles

Modeling of the atomic processes and photo emission of the plasmas for the EUV source

Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*; Nishikawa, Takeshi*; Koike, Fumihiro*; Tanuma, Hajime*

Reza Kenkyu, 36(Suppl.), p.1132 - 1135, 2008/11

no abstracts in English

Journal Articles

Atomic model and optimization of EUV light source

Nishihara, Katsunobu*; Sunahara, Atsushi*; Sasaki, Akira; Tanuma, Hajime*; Koike, Fumihiro*; Fujioka, Shinsuke*; Nishimura, Hiroaki*; Shimada, Yoshinori*

Reza Kenkyu, 36(11), p.690 - 699, 2008/11

The critical issue for realization of a laser produced plasma (LPP) extreme ultraviolet (EUV) light source is the conversion efficiency (CE) from incident laser power to EUV radiation of 13.5 nm wavelength. From an atomic physics, we show that tin is the most suitable radiation material compared with xenon and lithium. We also show the optimization of laser and target conditions to obtain high CE using a power balance model. We propose a double-pulse irradiation scheme for high CE using a carbon dioxides laser and a droplet target.

Journal Articles

Optimization of extreme ultraviolet emission from laser-produced tin plasmas based on radiation hydrodynamics simulations

Sunahara, Atsushi*; Nishihara, Katsunobu*; Sasaki, Akira

Plasma and Fusion Research (Internet), 3, p.043_1 - 043_5, 2008/08

no abstracts in English

Journal Articles

An Automated method to generate the collisional radiative model of multiple charged ions

Sasaki, Akira; Nishihara, Katsunobu*; Murata, Masaki*

Purazuma, Kaku Yugo Gakkai-Shi, 84(8), p.546 - 554, 2008/08

no abstracts in English

Journal Articles

Detailed atomic modeling of Sn plasmas for the EUV source

Sasaki, Akira; Sunahara, Atsushi*; Nishihara, Katsunobu*; Nishikawa, Takeshi*; Koike, Fumihiro*; Tanuma, Hajime*

Journal of Physics; Conference Series, 112, p.042062_1 - 042062_4, 2008/00

 Times Cited Count:4 Percentile:85.59

no abstracts in English

Journal Articles

Two dimensional radiation hydrodynamic simulation for extreme ultra-violet emission from laser-produced tin plasmas

Sunahara, Atsushi*; Sasaki, Akira; Nishihara, Katsunobu*

Journal of Physics; Conference Series, 112, p.042048_1 - 042048_4, 2008/00

 Times Cited Count:19 Percentile:98.45

We simulated Extreme Ultra-Violet (EUV) emission from laser-produced tin plasmas for the lithography of semi-conductor, using one- and two- dimensional radiation hydrodynamic simulation codes, and benchmarked the simulations by comparison with recent experiments. We successfully reproduced the measured conversion efficiency, X-ray spectra, and plasma density profiles in the experimental conditions. We found self-absorption of radiation due to the large opacity plays an important role in emission.

Journal Articles

EUV light source by high power laser

Izawa, Yasukazu*; Nishihara, Katsunobu*; Tanuma, Hajime*; Sasaki, Akira; Murakami, Masakatsu*; Sunahara, Atsushi*; Nishimura, Hiroaki*; Fujioka, Shinsuke*; Aota, Tatsuya*; Shimada, Yoshinori*; et al.

Journal of Physics; Conference Series, 112, p.042047_1 - 042047_4, 2008/00

 Times Cited Count:7 Percentile:92.73

In the development of a high power EUV source used in the EUV lithography system, we have been constructed EUV database of laser-produced tin plasma by the theoretical and experimental studies. On the basis of our understanding, the optimum conditions of lasers and plasmas were clarified, and we proposed the guidelines of laser plasma to obtain clean, efficient and high power EUV source for the practical EUV lithography system. In parallel to such studies, novel targets and high power laser system to generate the optimized EUV source plasma have been developed.

Journal Articles

Plasma physics and radiation hydrodynamics in developing an extreme ultraviolet light source for lithography

Nishihara, Katsunobu*; Sunahara, Atsushi*; Sasaki, Akira; Nunami, Masanori*; Tanuma, Hajime*; Fujioka, Shinsuke*; Shimada, Yoshinori*; Fujima, Kazumi*; Furukawa, Hiroyuki*; Kato, Takako*; et al.

Physics of Plasmas, 15(5), p.056708_1 - 056708_11, 2008/00

 Times Cited Count:109 Percentile:97.52(Physics, Fluids & Plasmas)

68 (Records 1-20 displayed on this page)