Characterization of cross-sectional profile of resist L/S and hole pattern using CD-SAXS

Abstract

Critical dimension small-angle x-ray scattering (CD-SAXS) with a grazing-incidence geometry, which was recently developed by the authors, has been successfully applied to the cross-sectional profile measurements of different types of L/S- and hole-type patterns on photoresist surfaces. We have calculated diffraction intensities from the nanostructures based on a distorted wave Born approximation method to take the refraction and the reflection at the interfaces between layers into account, and the average cross-sectional profiles have been analyzed by a model-based least-square method. From the precise analyses, slight cross-sectional profile differences of a few nanometers scale generated by using different material and exposure conditions have been identified. The obtained cross-sectional profiles showed good agreements with the results obtained by cross-sectional scanning electron microscopy (SEM). These results demonstrate the applicability of the CD-SAXS to the nanoscale structural metrology. It is expected that the CD-SAXS is also applicable to even smaller scale structures, e.g., those of EUV, NIL, or DSA, as the x-ray wavelength is well shorter than the critical lengths of these structures.