Research On Laser-produced Plasma Source With Output Wavelength Shorter Than 15nm

Compared with other extreme ultraviolet(EUV)sources,laser-produced plasma EUV source has the advantages of high brightness,small size,strong stability,and controllable wavelength.Extreme ultraviolet source plays a vital role in the manufacture of integrated circuits,metrology for mask detection,and microbial imaging.We systematically study the extreme ultraviolet radiation generated by laser ablation of five metal targets: aluminum(Al),molybdenum(Mo),tin(Sn),gadolinium(Gd)and bismuth(Bi)in the article.Furthermore,the radiation intensity of the extreme ultraviolet source with different metal targets is optimized by using the double-pulse shooting method.The specific research contents and results are as follows:Firstly,the EUV radiation characteristic of laser pulse interacting with Al,Mo,Sn,Gd and Bi target is studied.The study finds that the EUV light radiation of the five targets increases with increasing incident laser energy by changing the incident laser energy.We make the incident laser energy become 200 mJ,and the effect of lens position on the output light intensity is studied.It is found that when the metal target is located at the focal point of the lens,it does not correspond to the position where the EUV radiation is most intense.When moving the focus position,the EUV light radiation of the five targets shows an increasing trend and then a decreasing trend.In addition,the intensity changes of the EUV spectra of the five targets are studied by changing the number of laser-targeting pulse number at the same target location,and the results show that the Mo target has the highest reuse rate.Secondly,the dual-pulse laser targeting method is used to optimize the extreme ultraviolet radiation of the plasma,and the impacts of pre-pulse energy and pre-main pulse delay on the EUV light radiation characteristic of Al,Mo,Sn,Gd and Bi target are observed.The experimental results show that the EUV light radiation produced by the five targets shows a trend of first increases and then decreases with the increase of pre-pulse energy.With the increase of the pre-main pulse delay,the EUV light radiation of the five metal targets first decreases and then increases.Under the experimental conditions of optimal pre-pulse energy and pre-main pulse delay,the extreme ultraviolet spectrum radiation intensity generated by the double pulse is 1.77,1.67,1.97,1.65 and 1.64 times of the extreme ultraviolet radiation intensity during single pulse shooting.The results show that the double-pulse laser shooting method can greatly increase the output power of the laser plasma extreme ultraviolet light source.