Investigation Of The Debris And Spectral Behavior Of Laser-produced Gd Plasma Extreme Ultraviolet Sources

Extreme ultraviolet radiation( EUV) from high temperature laser-produced plasmas(LPPs) are considered as the most promising source candidate for next generation lithography. Particularly, in the investigation of the extreme ultraviolet source, people are focusing the Tin and Gd targets. Main reason of the choice comes from the fact that they provide high conversion efficiency in 2% bandwidth centered at 13.5nm and 6.7nm separately. For, Tin target, we consider 1s22s22p63s23p63d104s2 as atomic core, 4p64 dn as ground state, it occurs 4d-4f and 4p-4d transitions. That is unresolved transition array(UTA).The in-band radiation comes from Sn8+ and Sn13+.For Gd target, it has the same spectral properties as Tin. The in-band radiation comes from Gd12+ and Gd25+.However, with the interaction between laser and material, it produces a lot of debris. The composition of debris is cluster, neutral particles, molten droplets and energetic ions. On one hand, debris will deposit on the surface of optical system, which causes serious damage and effects, resulting in reducing reflectivity and lifetime. On the other hand, debris will absorb EUV radiation, which limits the conversion efficiency of EUV source. As a consequence, we must research the dynamic process of debris to find the appropriate method reducing kinetic energy and the number of debris.In this paper, we not only find the way how to mitigate the debris,but also design flat-field spectrometer to get EUV spectrum. Utilizing the condition of applying a ambient gas, magnetic field and combined effect to mitigate debris. The experiment results demonstrate all of three methods are effective, but combined effect is the optimum. By design, testing, calibration, we built a flat-field spectrometer and got the EUV spectrum of Tin, Gd, doped Gd target with increasing laser density.