Work

Polarization aberrations in EUV projection objectives: effects of numerical aperture and illumination incidence angle

Year: 2026

Type: article

Abstract: Polarization aberrations become increasingly significant in extreme ultraviolet (EUV) projection objectives as the numerical aperture increases and multilayer coating structures become more complex. In this work, polarization ray tracing is employed to investigate the effects of numerical aperture and illumination incidence angle on polarization aberrations. The P -matrix pupil is constructed to characterize the spatially varying polarization response, and the amplitude response matrix is calculated to evaluate its coherent-light impulse response. The effects of NA are investigated using MET3 and MET5 projection objectives with image-side NAs of 0.3 and 0.5, respectively. Increasing the NA increases the maximum diattenuation from 0.00926 to 0.22286 and the maximum retardance from 0.01784 rad to 0.20921 rad, accompanied by stronger off-diagonal ARM responses and spatial modulation. Under pseudo-total-reflection conditions, increasing the illumination-side plane-mirror tilt angle from 80° to 85° reduces the maximum diattenuation from 0.0264 to 0.0220 and the retardance range from 0.218 ∼ 0.486 rad to 0.077 ∼ 0.286 rad, with slightly weaker off-diagonal ARM responses. These results demonstrate distinct effects of numerical aperture and illumination incidence angle on polarization aberrations. The observed angular dependence is influenced by the multilayer reflection mechanism, coating properties, and optical configuration. This work provides a basis for analyzing polarization aberrations in high-NA EUV projection objectives under different multilayer-reflection conditions.

Source: Optics Express

DOI: 10.1364/oe.616344