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The OPC model is very critical in the sub 45nm device because the Critical Dimension Uniformity (CDU) is so tight to
meet the device performance and the process window latitude for the production level. The OPC model is generally
composed of an optical model and a resist model. Each of them has physical terms to be calculated without any wafer
data and empirical terms to be fitted with real wafer data to make the optical modeling and the resist modeling. Empirical
terms are usually related to the OPC accuracy, but are likely to be overestimated with the wafer data and so those terms
can deteriorate OPC stability in case of being overestimated by a small cost function.
Several physical terms have been used with ideal value in the optical property and even weren't be considered because
those parameters didn't give a critical impact on the OPC accuracy, but these parameters become necessary to be applied
to the OPC modeling at the low k1 process. Currently, real optic parameter instead of ideal optical parameter like the
laser bandwidth, source map, pupil polarization including the phase and intensity difference start to be measured and
those real measured value are used for the OPC modeling. These measured values can improve the model accuracy and
stability. In the other hand these parameters can make the OPC model to overcorrect the process proximity errors without
careful handling.
The laser bandwidth, source map, pupil polarization, and focus centering for the optical modeling are analyzed and the
sample data weight scheme and resist model terms are investigated, too. The image blurring by actual laser bandwidth in
the exposure system is modeled and the modeling result shows that the extraction of the 2D patterns is necessary to get a
reasonable result due to the 2D patterns' measurement noise in the SEM. The source map data from the exposure
machine shows lots of horizontal and vertical intensity difference and this phenomenon must come from the
measurement noise because this huge intensity difference can't be caused by the scanner system with respect to the X-Y
intensity difference specification in the scanner. Therefore this source map should be well organized for the OPC
modeling and a manipulated source map improves the horizontal and vertical mask bias and even OPC convergence. The
focus parameter which is critical for the process window OPC and ORC should be matched to the tilted Bossung plot
which is caused by uncorrectable aberration to predict the CD change in the through focus with a new devised method.
Pupil polarization data can be applied into the OPC modeling and this parameter is also used for the unpolarized source
and the polarized source and specially this parameter helps Apodization loss to be 0 and is evaluated for the effect into
the modeling.
With the analysis and optimization about the model parameters the robust model is achieved in the sub 45nm device
node.
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