18 April 2013 A novel focus monitoring technique using Iso-Dense overlay mark
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With decreasing of critical dimension (CD), the availability of depth of focus (DOF) goes down from technology node to technology node. Monitoring and controling of scanner focus on product wafers will be necessary. A technique entitled Iso-Dense Focus Monitor(IDFM) is developed to measure the focus errors of scanner systems. This IDFM method uses double side chrome mask and iso-dense binary overlay mark. The accuracy of this IDFM technique using binary mark may equal to the conventional PGFM method, and the IDFM technique only expose the wafer one time comparing with Z-SPIN which may expose two times. This method was simulated and also implemented on a litho tool of SMEE SSA600/10.
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S.X. Li, S.X. Li, J.R. Cheng, J.R. Cheng, A. Bourov, A. Bourov, G. Sun, G. Sun, "A novel focus monitoring technique using Iso-Dense overlay mark", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86811H (18 April 2013); doi: 10.1117/12.2011422; https://doi.org/10.1117/12.2011422


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