Layout small-angle rotation and shift for EUV defect mitigation

Blank defect mitigation is crucial for extreme ultraviolet (EUV) lithography. One of the existing options is to relocate patterns to avoid defect impact. However, when the defect number increases, only pattern shift in X-Y directions becomes far from enough, requiring the reticle holder rotate a small angle to provide a third exploring dimension. This non-trivial extension from 2D to 3D exploration requests efficient runtime as well as enough accuracy to handle different defect sizes and locations on the different features. In this paper, we present the first work with a detailed algorithm to find the optimal shift and rotation for layout patterns on blanks. Compared to the straightforward method, which is to check every pair of defect and feature at every possible relocation position, our proposed algorithm can significantly reduce the runtime complexity to scale linearly with the size of the full solution space. The experimental results validate our method and show a largely increased success rate of defect mitigation by shift and rotation.