Design Of Extreme Ultraviolet Collecter System Based On Free Surface Method

The collector for extreme ultraviolet(EUV) source is one of the most important parts in EUV lithography system.It usually consist of collection system and illumination system.The traditional type of EUV lithography system mainly adopts Wolter collection system,but the light distribution in the intermediate focus of this collection is uniform.So the illumination system must use the fly’s eye illumination system,This is a form of optical integrator, the optical integrator is composed of multiple tiny mirrors, manufacturing process is complex, the cost is very high.For the high production and lower cost,this paper will design a new collection system based on the method of free-form surface.First the development of EUV lithography and its collection system in the recent years is discussed;then the methods of designing free-form surface in the new type of collection system based on non-imaging geometry theories and extreme ultraviolet theoretical knowledge,according to the parameters of the collection system,a theoretical method to design free-form surface is obtained.In the process of constructing the free-form surface,firstly,the discrete points of the free-form surface is calculated in the matlab,secondly,the 3D model of the free-form surface is realized in Solid Works,finally,the designed system simulation is verified by the Tracepro software. The analysis of energy and evenness of the surface prove that the feasibility and correctness of the design.In order to facilitate the processing of the numerical control machine tool,we must get the corresponding model formula of the surface.Then the discrete points are obtained by high order power fitting,finally we get a 7 times higher power polynomial simulation structure that meets the design requirements.