Torretti F, Sheil J, Schupp R, Basko M M, Bayraktar M, Meijer R A, Witte S, Ubachs W, Hoekstra R, Versolato O O, Neukirch A J, Colgan J
Advanced Research Center for Nanolithography, Science Park 106, 1098 XG, Amsterdam, The Netherlands.
Department of Physics and Astronomy, and LaserLaB, Vrije Universiteit, De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
Nat Commun. 2020 May 11;11(1):2334. doi: 10.1038/s41467-020-15678-y.
Extreme ultraviolet (EUV) lithography is currently entering high-volume manufacturing to enable the continued miniaturization of semiconductor devices. The required EUV light, at 13.5 nm wavelength, is produced in a hot and dense laser-driven tin plasma. The atomic origins of this light are demonstrably poorly understood. Here we calculate detailed tin opacity spectra using the Los Alamos atomic physics suite ATOMIC and validate these calculations with experimental comparisons. Our key finding is that EUV light largely originates from transitions between multiply-excited states, and not from the singly-excited states decaying to the ground state as is the current paradigm. Moreover, we find that transitions between these multiply-excited states also contribute in the same narrow window around 13.5 nm as those originating from singly-excited states, and this striking property holds over a wide range of charge states. We thus reveal the doubly magic behavior of tin and the origins of the EUV light.
极紫外（EUV）光刻技术目前正进入大规模制造阶段，以实现半导体器件的持续小型化。所需的波长为13.5纳米的极紫外光由热且密集的激光驱动锡等离子体产生。这种光的原子起源显然还知之甚少。在这里，我们使用洛斯阿拉莫斯国家实验室的原子物理套件ATOMIC计算了详细的锡不透明度光谱，并通过实验比较验证了这些计算。我们的关键发现是，极紫外光很大程度上源自多重激发态之间的跃迁，而不是像当前范式那样源自单重激发态向基态的衰变。此外，我们发现这些多重激发态之间的跃迁在13.5纳米左右的相同窄窗口内也有贡献，与源自单重激发态的跃迁相同，并且这种显著特性在广泛的电荷态范围内都成立。因此，我们揭示了锡的双幻特性以及极紫外光的起源。
