Symmetry and Anisotropy in Wafer Deformation: Their Effect on Alignment Signal Degradation

To minimize overlay errors, precise alignment is essential. However, wafer warpages caused by chemical-mechanical polishing or high-temperature processing can severely compromise alignment accuracy. This work extends our previous work by developing a more comprehensive model of alignment mark behavior under wafer deformation. Using the finite-difference time-domain method, we evaluate how diffraction signals vary under different deformation modes. Our results demonstrate that asymmetric and parallel direction deformations have a more noticeable impact on alignment marks' diffraction signals. This provides valuable insights for resolving warpage-related wafer rejection and designing novel alignment marks that are resistant to wafer warpage.