Optical metrology system is used as high sampling CD measurement. The optical measurement technology using Fourier image can obtain much information with various optical conditions. We evaluated Fourier image method for CD metrology. Various issues of the optical measurement technology were found for CD measurement uncertainty. Measurement uncertainty depends on the number of position on Fourier image, and measurement uncertainty is improved by using multiple positions data. Top CD value is influenced by under layer pattern CD variance and under layer thickness variance. Optical CD measurement technology is influenced by various process variation like under-layer structure, stacked film thickness, material changes and so on. If optical measurement system applies to CD metrology, Fourier image method should be used in development phase for unfixed process because high number of data and speedy process feedback in no under layer situation is needed.
As well as measuring CD, monitoring pattern profile is becoming important for semiconductor metrology. Illuminating
the wafer and detecting the reflective light, reflective light intensity in the Fourier space includes the information of CD
and pattern profile variation by form birefringence effect. CD change and profile variation could be detected separately
for the actual wafer. Mathematical simulation is presented the background of our unique approach. The detail results of
CD and pattern profile monitor is shown in this paper.
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