Analysis of three-dimensional pinhole diffraction of deep ultraviolet converging light with large numerical aperture

The measurement accuracy of a point diffraction interferometer is influenced by the quality of the diffraction wavefront generated by a nanometer-scale pinhole. This paper analyzes the diffraction process of a pinhole illuminated by deep ultraviolet converging light with a large numerical aperture (NA) based on vector diffraction theory. Key metrics, including the diffraction NA and the wavefront aberrations relative to an ideal spherical wavefront, are examined in relation to the polarization state, pinhole diameter, and Cr thickness. Additionally, the impact of alignment errors is investigated. The results indicate that for a converging beam with and , the optimal polarization state is linear polarization, and the diffraction wavefront most closely approximates an ideal spherical wavefront when the pinhole diameter is 200 nm and the Cr thickness is 100 nm. Alignment errors alter the magnitude of the original central-symmetric aberration components and introduce asymmetric components such as coma.