Proceedings Article | 3 April 2012
Proc. SPIE. 8324, Metrology, Inspection, and Process Control for Microlithography XXVI
KEYWORDS: Metrology, Cadmium, Sensors, Image analysis, Scanning electron microscopy, Monte Carlo methods, Image quality, Line width roughness, Critical dimension metrology, Line edge roughness
The uncertainty associated with scanning electron microscopy (SEM) metrology is significant because
SEM image brightness is complexly related to the size and shape of the feature, its material, the geometry of
the pattern, as well as SEM setup. While regularly used methods of extracting critical dimensions (CD) rely
on image brightness analysis, the myCD software uses a physical model of the SEM in order to improve the
accuracy of measurements. Metrology below 10 nm was studied in this paper. Patterns were fabricated
using electron beam lithography and nanoimprint; they were imaged by SEM and examined using myCD.
Factors that are important for metrology at the sub-10 nm size range were studied using advanced Monte
Carlo software; the beam size, voltage, detector and linewidth were varied. SEM images were processed
using myCD, which utilizes an analytic model of the SEM and so does not require any libraries. The top and
bottom sizes, as well as wall angles and line width roughness were analyzed. The CD and profile results
from top down SEM images were compared to the vertical crossections. The challenges of sub-10 nm
metrology are discussed, mainly regarding the quality of SEM images and the physics of image formation.
