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24 March 2006 Advanced CDSEM matching methodology for OPC litho-cell-based matching verification
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Lithography in the low k1 factor regime poses increasingly stringent requirements on the control of critical dimension (CD) of various pitch ratios, also referred to as the OPC (Optical Proximity Correction) curve. Part of the CD budget is consumed by the tool-to-tool variation of the CD metrology tools. Hence, a CD-SEM installed base must be matched for a wide range of pitches within 20% of the OPC litho cell budget. For the 70nm node the matching requirement is 1 nm (20% of 5 nm). Traditionally, scanning electron microscope (SEM) matching consisted of comparing multiple measurements of identical features from different SEMs. The differences found were applied as offsets in the SEMs. These offsets had to be determined for all features. For OPC applications, these features cover a large range of pitches. A full update of the offsets could take a couple of days. An advanced matching methodology has been applied, based upon component wise matching of the SEMs, without the use of matching offsets. This new approach allows to shorten the matching cycle time to a few hours only. A sensitive verification test, using an interlaced sampling scheme on resist layers, proved that better than 0.6nm across pitch matching can be achieved. This matching difference is low enough for successful OPC matching using multiple SEMs from an installed base and is on par with the ITRS and the industry requirement for the 45 nm technology node.
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Ofer Adan, Hugo Cramer, Erik Van Brederode, Robert Schreutelkamp, and Ilan Englard "Advanced CDSEM matching methodology for OPC litho-cell-based matching verification", Proc. SPIE 6152, Metrology, Inspection, and Process Control for Microlithography XX, 61522Q (24 March 2006);

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