3 April 2012 SEM metrology on bit patterned media nanoimprint template: issues and improvements
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Critical dimension measurement is the most essential metrology needed in nanofabrication processes and the practice is most commonly executed using SEMs for its flexibility in sampling, imaging, and data processing. In bit patterned media process development, nanoimprint lithography (NIL) is used for template replication and media fabrication. SEM imaging on templates provide not only individual dot size, but also information for dot size distribution, the location of dots, pitch and array alignment quality, etc. It is very important to know the SEM measurement limit since the feature nominal size is less than 20 nm and the dot feature size and other metrics will relate to the final media performance. In our work an analytical SEM was used. We performed and compared two imaging analysis approaches for metrology information. The SEM beam was characterized using BEAMETR test sample and software for proper beam condition setup. A series of images obtained on a 27 nm nominal pitch dot array patterns were analyzed by conventional brightness intensity threshold method and physical model based analysis using myCD software. Through comparison we identified the issues with threshold method and the strength of using model based analysis for its improvement in feature size and pitch measurement uncertainty and accuracy. TEM cross sections were performed as accuracy reference for better understanding the source of measurement accuracy deviation.
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Justin J. Hwu, Justin J. Hwu, Sergey Babin, Sergey Babin, Peter Yushmanov, Peter Yushmanov, "SEM metrology on bit patterned media nanoimprint template: issues and improvements", Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83241F (3 April 2012); doi: 10.1117/12.918064; https://doi.org/10.1117/12.918064

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