Radiation-Hydrodynamics, Spectral, and Atomic Physics Modeling of Laser-Produced Plasma EUV Lithography Light Sources

Tin, lithium, and xenon laser-produced plasmas are attractive candidates as light sources for extreme ultraviolet lithography (EUVL). Simulation of the dynamics and spectral properties of plasmas created in EUVL experiments plays a crucial role in analyzing and interpreting experimental measurements, and in optimizing the 13.5 nm radiation from the plasma source. Developing a good understanding of the physical processes in EUVL plasmas is challenging, as it requires accurate modeling for the atomic physics of complex atomic systems, frequency-dependent radiation transport, hydrodynamics, and the ability to simulate emergent spectra and images that can be directly compared with experimental measurements. We have developed a suite of plasma and atomic physics codes to simulate in detail the radiative properties of hot plasmas. HELIOS-CR is a 1-D radiation-magnetohydrodynamics code used to simulate the dynamic evolution of laser-produced and z-pinch plasmas. Multi-frequency radiation transport can be computed using either fluxlimited diffusion or multi-angle models. HELIOS-CR also includes the capability to perform in-line non-LTE atomic kinetics calculations at each time step in the simulation. Energy source modeling includes laser energy deposition, radiation from external sources, and current discharges. The results of HELIOS-CR simulations can be post-processed using SPECT3D to generate images and spectra that include instrumental effects, and therefore can be directly compared with experimental measurements. Results from simulations of Sn laser-produced plasmas are presented, along with comparisons with experimental data. We discuss the sensitivity of the 13.5 nm conversion efficiency to laser intensity, wavelength, and pulse width, and show how the thickness of the Sn radiation layer affects the characteristics of the 13.5 nm emission.