Optical anisotropy approach in spectroscopic ellipsometry to determine the CD of contact hole patterns

Abstract

We applied spectroscopic ellipsometry for possible determination of the size of contact holes. We fabricated contact hole patterns in two dimensional array to increase sensitivity and the size of contact hole varied from 80 to 150 nm. Variation of hole-diameter in few nm was distinguishable by comparing the features in ellipsometry parameter Δ, ψ or the degree of polarization spectra. These features could be used to estimate the size of contact holes once they were calibrated by other techniques. When the photoresist film with dense contact hole pattern was regarded as a uniaxial material, the ellipsometry spectra could be analyzed with anisotropic optical model. In the process, the average size of contact hole could be estimated from the anisotropy of the film.