Design of a grazing incidence illumination system for anamorphic extreme ultraviolet lithography

High-numerical-aperture (NA) anamorphic extreme ultraviolet lithography (EUVL) is the next-generation technology under advanced technology nodes. The design of the illumination system requires achieving better illumination uniformity while ensuring energy efficiency. However, the traditional four-mirror structure illumination system ignores the impact of energy efficiency. In this paper, a grazing incidence illumination system design method is proposed. The illumination system adopts a grazing incidence relay system structure to improve energy efficiency and ensure good illumination uniformity. To realize different illumination modes and eliminate ray obstruction between adjacent field facet mirrors, a multiparameter double facet mirror assignment method is proposed. In this work, the double facet mirrors' multiparameter automatic alignment assignment model is established. Then the model parameters are optimized by using the Kuhn-Munkres algorithm to minimize the cost function. The optimal allocation relationship for double facet mirrors is obtained by using the proposed method. Through the above methods, an EUV illumination system matching an NA 0.55 anamorphic projection objective is designed. The simulation results show that the illumination system can achieve a mask plane illumination uniformity of 99% under different illumination modes, and the energy efficiency of the illumination system is 23.6%. Compared with the traditional four-mirror illumination system, the energy efficiency of the illumination system has improved by 28.2%.