Design of angle-resolved illumination optics using nonimaging bi-telecentricity for 193 nm scatterfield microscopy

Published: March 01, 2018

Author(s)

Martin Y. Sohn, Bryan M. Barnes, Richard M. Silver

Abstract

Accurate optics-based dimensional measurements of features sized well-below the diffraction limit require a thorough understanding of the illumination within the optical column and of the three-dimensional scattered fields that contain the information required for quantitative metrology. Scatterfield microscopy can pair simulations with angle-resolved tool characterization to improve agreement between the experiment and calculated libraries, yielding sub-nanometer parametric uncertainties. Optimized angle-resolved illumination requires bi- telecentric optics in which a telecentric sample plane defined by a Köhler illumination configuration and a telecentric conjugate back focal plane (CBFP) of the objective lens; scanning an aperture or an aperture source at the CBFP allows control of the illumination beam angle at the sample plane with minimal distortion. A bi-telecentric illumination optics has been designed enabling angle-resolved illumination for both aperture and source scanning modes while yielding low distortion and chief ray parallelism. The optimized design features a maximum chief ray angle at the CBFP of 0.002° and maximum wavefront deviations of less than 0.06 λ for angle-resolved illumination beams at the sample plane, holding promise for high quality angle-resolved illumination for improved measurements of deep-subwavelength structures using deep-ultraviolet light.
Citation: Optik
Volume: 156
Pub Type: Journals

Keywords

Optical microscopy, scatterfield microscopy, lens system design, angle-resolved illumination, bi-telecentric system, 193 nm microscopy
Created March 01, 2018, Updated November 10, 2018