Spectroscopic study of debris mitigation with minimum-mass Sn laser plasma for extreme ultraviolet lithography

Namba Shinichi

Fujioka Shinsuke

Nishimura Hiroaki

Yasuda Yuzuri

Nagai Keiji

Miyanaga Noriaki

Izawa Yasukazu

Mima Kunioki

Takiyama Ken

Applied Physics Letters

An experimental study was made of a target consisting of the minimum mass of pure tin (sSn) necessary for the highest conversion to extreme ultraviolet (sEUV) light while minimizing the generation of plasma debris. The minimum-mass target comprised a thin Sn layer coated on a plastic shell and was irradiated with a Nd:YAG laser pulse. The expansion behavior of neutral atoms and singly charged ions emanating from the Sn plasma were investigated by spatially resolved visible spectroscopy. A remarkable reduction of debris emission in the backward direction with respect to the incident laser beam was demonstrated with a decrease in the thickness of the Sn layer. The optimal thickness of the Sn layer for a laser pulse of 9 ns at 7×1010 W/cm2 was found to be 40 nm, at which low-debris emission in the backward direction and a high conversion to 13.5 nm EUV radiation were simultaneously attained.

eng

American Institute of Physics

Copyright (c) 2006 American Institute of Physics.

[ISSN] 0003-6951

[DOI] 10.1063/1.2199494

[NCID] AA00543431

[DOI] http://dx.doi.org/10.1063/1.2199494