Radiative Properties and Hydrodynamics of Laser Produced Tin Plasma for Efficient Extreme Ultraviolet Light Source

Abstract

A laser-produced tin (Sn) plasma is an attractive extreme-ultraviolet(EUV) light source for the next generation lithography in terms of its brightness and compactness. Radiative properties and hydrodynamics of the laser-produced Sn plasmas are quite important for investigating the optimum conditions for EUV generation. Several experiments have been performed to clarify the above issues;(i) EUV spectra emitted from isolated Snq+ (5 < q < 15) ions and opacity spectrumof a 30-eV Sn plasma have been measured as fundamental data for accurate modelingradiation energy transport in plasmas, (ii) electron density profile in 13.5 nmemission dominant region of a laser-produced Sn plasma was measured with a laserinterferometer for understanding hydrodynamics of an EUV source plasma. (iii) benchmarking one-dimensional (1D) radiation-hydrodynamic simulation codewith multiple laser beam irradiated spherical 1D Sn plasma. Based on the experimentalresults and calculations, it was found that optically thinner plasma emits 13.5 nm light more efficiently. Optical depth of Sn plasma is actively controlledwith changing laser pulse duration and the use of low-density porous target.