Design of tilted and decentered anamorphic optical system based on nodal aberration control

This paper proposes a design method for tilted and decentered anamorphic projection optics. In this method, the structure is designed in groups according to the magnification requirements; the anamorphic system section’s primary aberration is analyzed based on vector aberration theory, the tilted and decentered system section’s node behavior is analyzed based on node aberration theory, and spatial ray tracing is used to control the anamorphic optical system’s pupil to be elliptical to realize pupil matching between groups. A mathematical aberration balance and constraint control model is established. The node position is used as an evaluation function such that the node is close to or within the full field, thus controlling the primary aberration for the initial system over the full field. The initial system is constructed with increased optimization potential to satisfy the aberration and structural constraints. The initial structure for the tilted and decentered anamorphic projection optics (βx=1/4,βy=1/8) is constructed with the coma and astigmatism nodes close to or within the full field. The structure is then optimized to achieve a wavefront root-mean-square error for the EUV tilted and decentered anamorphic objective with NA= 0.55 of better than 0.025λ (λ = 13.5 nm).