Generation of particles and fragments by quasicontinuous wave fiber laser irradiation of stainless steel, alumina, and concrete materials

Daido, Hiroyuki*; Yamada, Tomonori; Furukawa, Hiroyuki*; Ito, Chikara; Miyabe, Masabumi; Shibata, Takuya; Hasegawa, Shuichi*

Journal of Laser Applications, 33(1), p.012001_1 -  012001_16, 2021/02

https://doi.org/10.2351/7.0000190

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

https://doi.org/10.1063/1.3524494

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 nm, which originates from 4-4 transitions of near palladium like ions (Tb). 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 nm.

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

https://doi.org/10.1016/j.hedp.2009.04.002

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 lasers as a pumping source has an advantage to reduce satellite contribution and to have narrower emission spectrum to obtain higher conversion efficiency.

Evaluation of fast EUV scintillator using 13.9 nm X-ray laser

Tanaka, Momoko; Furukawa, Hiroyuki*; Murakami, Hidetoshi*; Saito, Shigeki*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Yamatani, Hiroshi; Nagashima, Keisuke; Kagamitani, Yuji*; Ehrentraut, D.*; et al.

Journal of Physics; Conference Series, 112(4), p.042058_1 - 042058_4, 2008/00

https://doi.org/10.1088/1742-6596/112/4/042058

Optical technologies in the extreme ultraviolet (EUV) region have been receiving strong interest for the next generation lithography. Efficient and fast scintillators are one of the key devices functioning in the EUV region. In this paper, we report excellent properties of ZnO and GaN as scintillators in the EUV region, and to demonstrate the feasibility of using a Ni-like Ag EUV laser operated at 13.9-nm to evaluate these properties. The sample was irradiated with EUV laser pulses, and the fluorescence spectrum and the fluorescence lifetime were measured using a streak camera fitted with a spectrograph. In the case of ZnO, a clear, excitonic, fluorescence peak was observed at around 380 nm with a decay lifetime of 3 ns. For GaN, a fluorescence peak at 370 nm having slower 5-ns decay time was observed. In this respect, the EUV scintillation properties of ZnO is said to be more favorable than GaN.

Low-density tin targets for efficient extreme ultraviolet light emission from laser-produced plasmas

Okuno, Tomoharu*; Fujioka, Shinsuke*; Nishimura, Hiroaki*; Tao, Y.*; Nagai, Keiji*; Gu, Q.*; Ueda, Nobuyoshi*; Ando, Tsuyoshi*; Nishihara, Katsunobu*; Norimatsu, Takayoshi*; et al.

Applied Physics Letters, 88(16), p.161501_1 - 161501_3, 2006/04

https://doi.org/10.1063/1.2195693

no abstracts in English

Theoretical simulation of extreme UV radiation source for lithography

Fujima, Kazumi*; Nishihara, Katsunobu*; Kawamura, Toru*; Furukawa, Hiroyuki*; Kagawa, Takashi*; Koike, Fumihiro*; More, R.*; Murakami, Masakatsu*; Nishikawa, Takeshi*; Sasaki, Akira; et al.

Emerging Lithographic Technologies VIII, Proceedings of SPIE Vol.5374, p.405 - 412, 2004/00

no abstracts in English

Development of the atomic model of Sn and Xe ions and its application to studies of the EUV sources

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

no journal, , 

We present calculation of atomic data and development of atomic model of Sn and Xe ions, for the theoretical investigation and optimization of the EUV source for the next generation microlithography. In order to evaluate radiative properties of Sn and Xe ions, measurement of accurate wavelengths of strong emission lines as well as determination of dominant satellite channels from multiply- and inner-shell excited states are essential. We apply database technologies to choose a set of atomic levels, which has significant contribution to the emission. After iterative calculation, an appropriate atomic model which gives reasonable values of coefficients of radiative transfer is obtained.

Atomic processes for shorter wavelength EUV sources

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

no journal, , 

Atomic processes in laser produced plasmas of atomic elements with Z=50-70 for their application to the shorter wavelength EUV sources. The scaling of the wavelength of the 4d-4f transition array is investigated, which shows emission in the wavelength of 6.5nm band can be obtained using Gd and Tb. Based on the calculated atomic data, the radiative property of the plasma is calculated using the collisional radiative model. The power balance model suggests that the conversion efficiency similar to that from Sn plasma can be obtained by optimizing the plasma condition, with higher laser intensity of the order of , which is required to obtain high plasma temperature of 100eV, and to obtain around 20 times ionized Gd.

Atomic radiation processes in plasmas for the EUV source

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

no journal, , 

We study atomic radiation processes in the Sn plasmas for the EUV source. We develop a collisional radiative model of Sn ions, based on the atomic data calculated using the Hullac code. We calculate spectral emissivity and opacity of the plasma, which are used in the radiation hydrodynamics simulation, for the optimization of the pumping condition of the laser produced plasma (LPP) EUV sources. Methods to improve atomic model is also discussed.

Atomic modeling of short wavelength EUV sources using Gd and Tb target

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

no journal, , 

no abstracts in English