Calculated are the properties of amplification on Balmer-alpha of hydrogen-like nitrogen (N-Ba-alpha), which is extreme ultraviolet (EUV) light. It is expected to be applied to semiconductor lithography for higher integration degree.
According to the previous study [1], stimulated emission of unresolved satellite lines by amplified N-Ba-alpha reduces the small signal gain of N-Ba-alpha in the framework of population kinetics. To consider the satellite lines, a radiation transport calculation code was developed, and, to carry out the calculation, a noninteracting spectator-electron model (NISEM) [2] was applied. In the model, unresolved satellite lines are approximated to be Gaussian functions by three parameters. Emission energies and oscillator strengths of the unresolved satellite lines were calculated by GRASP (a General-purpose Relativistic Atomic Structure Program) [3]. In this study, singly excited nitrogen was assumed to have a spectator electron and the orbitals of the spectator electron are 7s-7i, 8s-8k, and 9s-9l, being 24 orbitals in total.
The time evolution of N-Ba-alpha was calculated by a rate equation coupled with radiation transport including the unresolved satellite lines modeled by the NISEM. In the calculation, a traveling- wave excitation scheme was applied to examine successive amplification. The peak intensity and the gain coefficients of N-Ba-alpha is estimated and the accuracy of the NISEM will be also discussed.
[1] N. Tatsumura, S. Yamamura, T. Ozawa, K. Horioka, and T. Kawamura, Phys. Plasmas. 20 (2013) 083304.
[2] K. Honda, K. Mima, and F. Koike, Phys. Rev. E. 55 (1997) 4594.
[3] K. G. Dyall, I. P. Grant, C. T. Johnson, F. A. Parpia, and E. P. Plummer, Comput. Phys. Commun. 55 (1989) 425.
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