Evolution analysis of EUV radiation from laser-produced tin plasmas based on a radiation hydrodynamics model

Abstract

One of fundamental aims of extreme ultraviolet (EUV) lithography is to maximize brightness or conversion efficiency of laser energy to radiation at specific wavelengths from laser produced plasmas (LPPs) of specific elements for matching to available multilayer optical systems. Tin LPPs have been chosen for operation at a wavelength of 13.5 nm. For an investigation of EUV radiation of laser-produced tin plasmas, it is crucial to study the related atomic processes and their evolution so as to reliably predict the optimum plasma and experimental conditions. Here, we present a simplified radiation hydrodynamic model based on the fluid dynamic equations and the radiative transfer equation to rapidly investigate the evolution of radiation properties and dynamics in laser-produced tin plasmas. The self-absorption features of EUV spectra measured at an angle of 45° to the direction of plasma expansion have been successfully simulated and explained, and the evolution of some parameters, such as the plasma temperature, ion distribution and density, expansion size and velocity, have also been evaluated. Our results should be useful for further understanding of current research on extreme ultraviolet and soft X-ray source development for applications such as lithography, metrology and biological imaging.

Efficient Generation of Extreme Ultraviolet Light From Nd :YAG-Driven Microdroplet-Tin Plasma

“…The literature on Nd:YAG-driven tin plasma mostly deals with the emission from planar solid targets [31][32][33][34][35][36][37][38][39][40][41][42], tin-coated spherical targets [29,[43][44][45][46][47], or liquid-droplet targets out of tin alloys [48]. The literature covering the emission properties of laser-produced plasma (LPP) from high-purity tin microdroplets, the industrial targets of choice, remains scarce [49][50][51].…”

Prominent radiative contributions from multiply-excited states in laser-produced tin plasma for nanolithography

“…In the context of understanding and supporting the drive laser wavelength change in future industrial sources, calculation of complete and accurate opacity spectra and of the atomic data therein is essential for predictive simulations of source performance. These data are needed in radiation hydrodynamics codes [23][24][25][26] and for the calculation of emission spectra. Without such accurate opacity data, the capability for predictive modeling would be severely impaired as, for example, modest underestimations of opacity could lead to significant underestimation of required drive laser intensities.…”

Effect of Time Delay on Laser-Triggered Discharge Plasma for a Beyond EUV Source

“…The atomic data for the theoretical simulation of the Gd spectra are calculated by the Hartree-Fock approximate Cowan codes. Research shows that the configuration interaction (CI), which causes considerable changes in wavelength and the intensity of EUV lines [23], is to be taken into account between the 4d n , 4d n−1 f, 4d n−1 5p, 4d n−1 5f, and 4p 5 4d n+1 configurations. The configuration setups and scaling factors are according to S. S. Churilov [24].…”