Laser-plasma source parameters for Kr, Gd, and Tb ions at 6.6 nm

Abstract

There is increasing interest in extreme-ultraviolet (EUV) laser-based lamps for sub-10-nm lithography operating in the region of 6.6 nm. A collisional-radiative model is developed as a post-processor of a hydrodynamic code to investigate emission from resonance lines in Kr, Gd, and Tb ions under conditions typical for mass-limited EUV sources. The analysis reveals that maximum conversion efficiencies of Kr occur at 5×1010W/cm2, while for Gd and Tb it was ≃0.9%/2πsr for laser intensities of (2−5)×1012W/cm2.

Laser-Produced Heavy Ion Plasmas as Efficient Soft X-Ray Sources

“…The in-band EUV CEs were evaluated at λ = 6.7 nm within a bandwidth of 0.6% for Gd and Mo and at λ = 6.5 nm with the bandwidth of 0.6% for Tb. The CEs were maximized at 0.8% in both Gd and Tb at I L = 1 × 10 12 W/cm 2 , and the observed maximum CE was almost in agreement with the theoretical evaluation of 0.9% obtained from a collisional-radiative (CR) and modified 1D hydrodynamic code numerical simulation [21]. It is noted that the wavelength of 6.6 nm, predicted in the work, is slightly different compared to our spectral peaks at 6.5 and 6.7 nm.…”

6.7-nm Emission from Gd and Tb Plasmas over a Broad Range of Irradiation Parameters Using a Single Laser

“…The highest CE for Gd, 0.47%, was obtained at a laser intensity of 6.8x10 11 W/cm 2 with a laser pulse duration of 2ns. Both the maximum CE value and the laser intensity at which the maximum CE occurs are similar to those reported in in previous modeling work [29]. It should be noticed that if the CE were to be computed using the data from a single detector placed at 45 degrees assuming an isotropic distribution, the CE values in FIG.…”

Efficient extreme ultraviolet emission from one-dimensional spherical plasmas produced by multiple lasers

“…EUV sources at 6.x nm are provided by LPPs of the rare-earth elements, Gd and Tb, 11,12) and other elements, Mo and Kr. 13) The rare-earth elements Gd and Tb produce strong narrowband emission, which is attributed to an n = 4 ¹ n = 4 (¦n = 0) unresolved transition array (UTA). The spectral behavior of Gd and Tb plasmas is expected to be similar to that of Sn plasmas because their emission is dominated by 4d open-shell ions.…”