在曝光线宽为90 nm的投影光刻机中，准分子激光光源发出的矩形截面光束，需要进行一维扩束，以获得光束整形单元所需的正方形截面分布。现有的这类扩束单元分别存在严重的相干散斑效应和严格的装调公差等不足。基于此，提出了多组元平行反射扩束镜组。通过求解各组元透射率值的线性方程组，得到若干种扩束单元结构，其中的四组元扩束单元每个组元只有一种透射率，有效降低了镀膜的工艺成本。分别从公差分析、系统透射率和出射光束均匀性等方面对各类扩束单元结构进行综合比较，并通过建模仿真，验证了设计的四组元扩束单元的散斑效应和装调公差灵敏度都明显降低，而且出射光束较均匀，有利于提高照明均匀性。

The excimer laser beam is needed to be expanded in one dimension to meet the requirement of square cross-section distribution for beam shaping unit, because of the rectangular cross-section distribution characteristic of laser source for projected lithography which holds 90 nm exposure linewidth. The reported beam expanding units have the deficiencies of serious speckle effect of coherence and the strict tolerance to alignment. A kind of multi-component parallel reflective expander is proposed aiming at the shortages above. The structures of such beam expanding units are determined by calculating linear equation set. One of the structures, which is called four-component beam expanding unit, has only one transmissivity to reduce the cost of coating. A synthesis comparison is executed at the aspects of tolerance analysis, transmission efficiencies and uniformities of output beam. According to the simulation results, the designed four-component beam expanding unit is proven to be an optimal scheme by the evident reduction in speckle effect and tolerance sensitivity. Meanwhile, the homogeneity of output beam is improved, which is favorable to enhance the uniformity of the whole illumination system.