Modeling the Effect of Line Profile Variation on Optical Critical Dimension Metrology

Published

May 7, 2007

Author(s)

Thomas A. Germer

Abstract

We investigate the effects that variations in profile have on specular and diffuse reflectance from a grating consisting of parallel lines. We investigate, as an example, a nominal grating consisting of 100 nm photoresist or silicon lines on a silicon substrate, having a vertical sidewall angle, a pitch of 200 nm, and a height of 100 nm. We model the effects of variations by calculating the reflectance of multiple 25-line superstructures, in which the positions of the line edges are randomly modulated about their nominal profile. We study line-edge variation, line-position variation, and random edge variation. We find that the reflected field can be approximated by the mean field reflected by a distribution of periodic gratings and that the field does not represent the field from the average profile. When fitting results to more than one modeled parameter, the changes that are observed can be enough to shift the deduced parameter in some cases by more than the rms variation of that parameter. The intensity distribution and the polarization of the diffuse scattering are found to be different for line-width variation and line-position variation.

Proceedings Title

Metrology, Inspection, and Process Control for Microlithography | XXI | 2007 |

Conference Dates

February 25-March 2, 2007

Conference Title

Metrology, Inspection, and Process Control for Microlithography

Pub Type

Conferences

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Keywords

gratings, line-edge variation, optical critical dimension metrology, scatterometry

Citation

Germer, T. (2007), Modeling the Effect of Line Profile Variation on Optical Critical Dimension Metrology, Metrology, Inspection, and Process Control for Microlithography | XXI | 2007 |, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=841071 (Accessed May 9, 2026)

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