| Fused silica is one of the commonly used optical elements in excimer lithography system,long-term laser irradiation will cause fused silica aging,which seriously affects the efficiency and quality of lithography,therefore,the evaluation on the service life of fused silica naturally becomes an important part that cannot be ignored in the research process.The radiation uniformity of the traditional accelerated aging system is poor,which does not meet the actual working conditions,and the energy density adjustment range of the system is small,which cannot meet the accelerated aging requirements of different grades of fused silica lenses.Therefore,an accelerated aging system that can reasonably evaluate the service life of fused silica is established,which is of great significance for improving the life database of related optical components of excimer lithography systems.Firstly,this paper proposes an accelerated aging experiment scheme that meets actual working conditions:according to the light intensity distribution characteristics of the excimer laser,an aspheric cylindrical lens group is used to shape the vertical beam;a combined attenuator and a variable magnification beam reduction system are used to change the energy density,so as to meet the accelerated aging requirements of different grades of fused silica lenses;finally,a damage detection system is designed,the microscope is used to observe and record the damage of lens during irradiation.Then,the optical design is performed according to the basic parameters of the optical system.The design results show that the maximum beam uniformity can reach more than 96%after shaping,which meets the actual working conditions;the beam reduction ratio is0.25~×～0.5~×,the results show that the RMS wave aberration at each magnification is less than λ/4,which meets the requirements of image quality evaluation,and the cam curve is designed;the magnification of the microscope objective isb β=6~×,the numerical aperture is NA=0.2,which meets the imaging requirements.Finally,the mechanical structure of the completed optical system is designed in this paper.The mechanical structure is divided into five parts:accelerated aging system,damage detection system,energy detection system,experiment box system,and three-dimensional lens adjustment mechanism,the results meet the processing requirements. |
