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22 March 2008 Extracting dose and focus from critical dimension data: optimizing the inverse solution
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We present a summary of various methods for inverting top and bottom critical dimension (CD) data to extract dose and focus information. We explain analytical, numerical, and library inversion techniques in detail, and explore their relative merits for the purposes of online and offline focus monitoring use models. We also detail the modeling requirements associated with each inversion technique, and -- for cases where the model form is flexible -- present a cross-validation methodology for optimizing the response model to fit experimental data. We present modeling and inversion results from seven exemplary photolithography processes, and study the results from each methodology in detail. While each method has its own set of advantages and disadvantages, we show that the library method represents the optimum choice to satisfy a variety of use models while minimizing cost.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kevin R. Lensing, J. Broc Stirton, and Siddharth Chauhan "Extracting dose and focus from critical dimension data: optimizing the inverse solution", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 692209 (22 March 2008);

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