10 May 2005 Lithography tool qualification using angular scatterometry
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Lithography process control remains a significant challenge in modern semiconductor manufacturing. Metrology efforts must overcome the complexity of the lithography process, as well as the number of process elements that contribute to overall process yield. One specific area of concern is lithography tool focus control. It is vital to control photolithography tool focus during the photoresist development step with a high degree of precision and accuracy. Furthermore, dose variations can compound the difficulty in determining focus. The lenses used in photolithography tools have a very limited depth of focus, so utmost precision is necessary. Tools that are in focus will result in sharper and better controlled features, while tools that are out of focus will result in improperly developed photoresist features. Angular scatterometry is a technology well-suited for lithography inspection and process control because it provides rapid measurement data and can be used for the measurement of resist line profiles. We report on model-based methods for focus control and their application towards photolithography control in a production setting. Topics of discussion include the effect of model parameter selection for focus metrics on focus curve quality and accuracy, as well as the effect of grating target design on focus sensitivity and accuracy. Measurement data using this focus technique in a production setting will be presented.
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Mike Littau, Mike Littau, Christopher J. Raymond, Christopher J. Raymond, Prasad Dasari, Prasad Dasari, Jasen Moffitt, Jasen Moffitt, Sushil Shakya, Sushil Shakya, } "Lithography tool qualification using angular scatterometry", Proc. SPIE 5752, Metrology, Inspection, and Process Control for Microlithography XIX, (10 May 2005); doi: 10.1117/12.600413; https://doi.org/10.1117/12.600413

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