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Spectroscopic CD metrology for sub-100-nm lithography process control

The accelerating trend to smaller linewidths and low-k1 lithography makes metrology and process control more challenging with each succeeding technology generation. Optical CD metrology based on spectroscopic ellipsometry provides higher precision, improved matching, and richer information for line width and shape (profile) control which complement conventional litho metrology techniques. Analysis of site-to-site, within-field, field-to-field, and cross-wafer CD and line-shape distributions using KLA-Tencor SpectraCD permits separation of sources of variation between the stepper and track thus enabling proper process control. Focus-exposure analysis using SpectraCD data provides a more complete understanding of the lithography process window. Comparison between SpectraCD CD measurements on nominal 1:5 Line/Space ratio grating targets to isolated line CD-SEM measurements show excellent correlation over a large focus-exposure process range, including sub-100nm features. This result provides verification that SCD measurements on grating targets can be used to monitor and provide feedback to lithography process for isolated lines.