离轴照明作为一种重要的分辨率增强技术被广泛地应用于投影光刻系统。使用衍射光学元件(DOE)作为光刻照明系统的光束整形器件,能够在保持较高照明效率的基础上精确控制离轴照明光束的形状及光强分布。本文利用基于傅里叶变换的分步迭代方法,优化设计了该类衍射光学元件(DOE)。DOE采用了多台阶位相结构,设计所得8台阶DOE设计结果分别实现了偶极、四极、环形及Bulls-Eye等照明方式,其照明效率都达到了80%以上,与目标光强分布的均方根偏差均＜7％。

As a very important Resolution Enhancement Technology (RETs),Off-axis Illumination (OAI) is widely applied to optical projection lithography system.Application of Diffractive Optical Element(DOE) to OAI not only can cotrol precisely the flexible illumination shape and the intensity profile but also can retain a higher efficiency of light source.In this paper,the four kinds of DOEs with 8 phase levels were designed by using the step-iterative algorithm based Fourier transfer,and the four elements could realize dipole,quadrupole,annular and Bulls-Eye illuminations respectively.The simulation results show that the efficiencies of the light sources are all better than 80% and the RootMean-Squares(RMSs) of intensity profiles are all smaller than 7% as compared with that of the ideal one.