Experimental And Theoretical Study Of Laser-produced Al-Sn Alloy Plasma Extreme Ultraviolet Radiation Behavior

Tin（Sn）is one of the elements of great interest for extreme ultraviolet lithography light sources,and its radiation in the 13.5 nm band contains a large number of indistinguishable transitions（UTAs）and quasi-continuous spectral lines.The process of laser tin plasma radiation light generation has a high temperature difference between its core region and edge region,and there is a strong self-absorption effect as well as self-etching phenomenon of non-uniform plasma,how to improve the conversion efficiency of the extreme ultraviolet light source has become the subject of current research.Some experimental results show that the doping of solid tin targets can effectively reduce the self-absorption effect of tin plasma.Laser plasma,as an ideal laboratory ion source,can provide a large amount of energy level jump data,atomic structure and kinetic parameters of highly charged state ions,which can provide data and diagnostic support for tin plasma studies in extreme ultraviolet lithography light sources.In this paper,laser Al-Sn alloy plasma extreme ultraviolet spectra in the wavelength range of 8.5-17.0 nm were obtained using a laser plasma spatio-temporal evolution measurement device to analyze the spatio-temporal evolution characteristics of Al-Sn alloy spectra and the spectral profile features.The leap arrays of Al and Sn elements in the 8.5-17 nm range were obtained by the atomic structure calculation program（Cowan）.Using the discrete spectral features of Al elements at 8.5-17 nm,the plasma emission spectra of Al-Sn alloys are simulated using a steady-state-based collisional radiation model to realize the diagnosis of the plasma state.The main work includes:1.Measurement and analysis of Al-Sn alloy plasma with atomic percentages of 5-95%,50-50%and 95-5%and pure Sn laser plasma extreme ultraviolet spectra.The spatio-temporal evolution spectra of the four scaled targets and the intensity evolution of the characteristic peaks are analyzed,and the spectra of the four targets with different atomic percentages are illustrated in terms of spectral intensity,spectral structure,self-absorption peaks and conversion efficiency of the extreme ultraviolet spectra under the same experimental conditions.2.Designation of the plasma spectral profile of laser Al-Sn alloys.Using the atomic structure calculation program（Cowan）,the single-electron excited state lepton arrays of Al³⁺-Al⁶⁺and Sn⁷⁺-Sn¹²⁺ions were obtained to specify the lepton arrays of the dominant spectral features.3.Simulation of laser Al-Sn alloy plasma spectra and diagnosis of plasma states.Using the characteristics of the experimental spectra of Al elements in the 8.5-13.1 nm and 16.0-17.0 nm discrete spectral lines,the characteristic spectral lines of Al elements were determined by combining with the NIST database;using the steady-state collisional radiation model（CR model）,the charge state distribution of ions in the highly ionized state was calculated;the data output from the Cowan program and the ion abundance obtained from the collisional radiation model were used to Theoretical simulations of the experimental spectra of Al-Sn alloy plasma were performed to obtain information on the state parameters of the plasma,such as electron temperature and electron density,to achieve an accurate diagnosis of the laser plasma state of Al-Sn alloy.