用于投影光刻机光瞳整形的衍射光学元件设计

Design of Diffractive Optical Element for Pupil Shaping Optics in Projection Lithography System

投影光刻机普遍采用衍射光学元件(DOE)来产生各种照明模式。针对投影光刻机中准分子激光器空间相干性差的特点,提出了一种混合分区设计方法,并利用该方法对产生传统照明模式、二极照明模式和四极照明模式的DOE进行了具体的设计。仿真分析了采用常规重复分区方法和混合分区方法的两类设计结果,并对它们的远场光强分布进行了详细的比较分析。在相同的局部优化算法条件下,相对于常规重复分区方法的设计结果而言,混合分区方法设计的DOE可使传统照明模式的非均匀性从26.45%下降到1.12%,二极照明模式的非均匀性从19.93%下降到5.45%,四极照明模式的非均匀性从17.73%下降到3.54%。混合分区设计方法无需改变局部优化算法,在保持高衍射效率的同时能大幅度提高光瞳均匀性。

The diffractive optical element （DOE） is widely used to generate various illumination modes for pupil shaping optics in the projection lithography system. A mixed multi-region design method is proposed to calculate the phase of DOE, aiming at the poor spatial coherence of excimer laser. The DOEs generating conventional, dipole and quadrupole illumination modes are designed and analyzed by both the repeated multi-region design and the mixed multi-region design. Compared with the results of the repeated multi-region design method, the non-uniformities of the mixed multi-region design method can decrease from 26.45% to 1. 12%, from 19.93% to 5.45% and from 17.93 % to 3.54 % respectively for the conventional, dipole and quadrupole illumination modes using the same local optimization algorithm. The analysis results indicate that the DOE designed by the mixed multi-region design can improve the uniformity of the far-field intensity distribution greatly while maintaining a high diffractive efficiency without changing the local optimization algorithm.