Understanding the influence of three-dimensional sidewall roughness on observed line-edge roughness in scanning electron microscopy images

Understanding the influence of three-dimensional sidewall roughness on observed line-edge roughness in scanning electron microscopy images

van Kessel, L.C.P.M. (TU Delft ImPhys/Microscopy Instrumentation & Techniques)
Huisman, T.A. (ASML)
Hagen, Cornelis W. (Student TU Delft)

2020

Background: Line-edge roughness (LER) is often measured from top-down critical dimension scanning electron microscope (CD-SEM) images. The true three-dimensional roughness profile of the sidewall is typically ignored in such analyses. Aim: We study the response of a CD-SEM to sidewall roughness (SWR) by simulation. Approach: We generate random rough lines and spaces, where the SWR is modeled by a known power spectral density. We then obtain corresponding CD-SEM images using a Monte Carlo electron scattering simulator. We find the measured LER from these images and compare it to the known input roughness. Results: For isolated lines, the SEM measures the outermost extrusion of the rough sidewall. The result is that the measured LER is up to a factor of 2 less than the true on-wafer roughness. The effect can be modeled by making a top-down projection of the rough edge. Our model for isolated lines works fairly well for a dense grating of lines and spaces as long as the trench width exceeds the line height. Conclusions: In order to obtain and compare accurate LER values, the projection effect of SWR needs to be taken into account.

line edge roughness
metrology
Monte Carlo methods
scanning electron microscopy
sidewall roughness

http://resolver.tudelft.nl/uuid:c791571a-aa13-45c3-8854-04c344f20078

https://doi.org/10.1117/1.JMM.19.3.034002

1932-5150

Journal of Micro/Nanolithography, MEMS, and MOEMS, 19 (3)

Institutional Repository

journal article

© 2020 L.C.P.M. van Kessel, T.A. Huisman, Cornelis W. Hagen