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Critical dimension metrology is the most needed feedback in nanofabrication and automatic CDSEM-based methods
are by far the industrial standard for its well-established methodology and ease of programming and flexibility in
measurement setup and operation. The dimensional measurements from SEMs consist of two steps, the first being the
pixel based electron emission signal intensity profile generation and the second being the algorithm treatment on the
generated intensity profile for the dimension determination. However, SEM metrology involves uncertainty of the
measurement in the signal processing step, because the SEM signal formation is an extremely complex process
depending on the pattern geometry, materials, detector setup, and beam voltage. Analytical SEMs are even less
optimized for the task of quantitative metrology, especially at the CD ranging below 100 nm.
In this work, we used an analytical SEM for CD metrology applications on quartz nanoimprint template from the
perspective that only analytical SEM is accessible. The machine was tuned and beam characterization was done first to
find the best reasonable condition for consistent manual operation using BEAMETR beam measurement pattern and
software. The optimized beam condition set was then used for image collection on pitch pattern quartz template and
the measurements were done using regular imaging processing and physical model based processing tool myCD. In
order to discuss the spot size on the scan signal and the resulting influence on CD measurements, we used CHARIOT
simulation software for simulated intensity profile as demonstration. The quartz template was then measured through a
mask CDSEM for final data comparison. Selected sites were cross sectioned to reveal profile information as metrology
comparison reference. Through our exercise, the metrology capability and fundamental limitation of analytical SEM
operation with regular imaging processing was identified and the improvement using the physical modeling imaging
process was verified.
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